U.S. patent application number 11/408052 was filed with the patent office on 2007-02-08 for method for introducing and expressing genes in animal cells, and live invasive bacterial vectors for use in the same.
This patent application is currently assigned to UNIVERSITY OF MARYLAND, BALTIMORE. Invention is credited to David M. Hone, George K. Lewis, Robert J. Powell.
Application Number | 20070031382 11/408052 |
Document ID | / |
Family ID | 30117727 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070031382 |
Kind Code |
A1 |
Powell; Robert J. ; et
al. |
February 8, 2007 |
Method for introducing and expressing genes in animal cells, and
live invasive bacterial vectors for use in the same
Abstract
A method for introducing and expressing genes in animal cells is
disclosed comprising infecting the animal cells with live invasive
bacteria, wherein the bacteria contain a eukaryotic expression
cassette encoding the gene. The gene may encode, e.g., a vaccine
antigen, a therapeutic agent, an immunoregulatory agent or an
anti-sense RNA or a catalytic RNA.
Inventors: |
Powell; Robert J.;
(Baltimore, MD) ; Lewis; George K.; (Baltimore,
MD) ; Hone; David M.; (Ellicott City, MD) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
UNIVERSITY OF MARYLAND,
BALTIMORE
|
Family ID: |
30117727 |
Appl. No.: |
11/408052 |
Filed: |
April 21, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10369519 |
Feb 21, 2003 |
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11408052 |
Apr 21, 2006 |
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09420770 |
Oct 19, 1999 |
6682729 |
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10369519 |
Feb 21, 2003 |
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09126220 |
Jul 30, 1998 |
6150170 |
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09420770 |
Oct 19, 1999 |
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08433790 |
May 3, 1995 |
5877159 |
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09126220 |
Jul 30, 1998 |
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Current U.S.
Class: |
424/93.2 ;
424/200.1; 514/44R |
Current CPC
Class: |
A61K 48/00 20130101;
A61K 2039/523 20130101; A61K 2039/53 20130101; A61K 2039/51
20130101; A61K 48/0008 20130101; A61K 48/0091 20130101; C12N 15/87
20130101; A61K 2039/5254 20130101 |
Class at
Publication: |
424/093.2 ;
514/044; 424/200.1 |
International
Class: |
A61K 48/00 20060101
A61K048/00; A61K 39/02 20060101 A61K039/02 |
Claims
1-20. (canceled)
21. A delivery vehicle for delivering a mammalian expression
plasmid into a mammalian cell, said vehicle comprising a pure
culture of attenuated Shigella cells into which said expression
plasmid has been introduced, wherein said Shigella cells have at
least one genetic mutation such that they lyse once inside said
mammalian cell, thereby delivering said expression plasmid
therein.
22. The delivery vehicle according to claim 21, wherein said
Shigella is S. flexneri.
23. The delivery vehicle according to claim 21, wherein said
mammalian cell is a cell of an intestinal mucosal epithelium.
24. The delivery vehicle according to claim 23, wherein said
Shigella is S. flexneri.
25. The delivery vehicle according to claim 21, wherein said
attenuated Shigella cells are inactivated.
26. The delivery vehicle of claim 21, wherein said mutation is a
mutation in the wild-type asd gene within said Shigella cells.
27. A method for delivering a mammalian expression plasmid into a
mammalian cell, said method comprising: (i) introducing a mammalian
expression plasmid into a pure culture of attenuated Shigella
cells, wherein said Shigella cells have at least one genetic
mutation such that they lyse once inside said mammalian cell; and
(ii) administering said Shigella cells to said mammalian cell,
thereby delivering said expression plasmid therein.
28. The method according to claim 27, wherein said Shigella is S.
flexneri.
29. The method according to claim 27, wherein said mammalian cell
is a cell of a mucosal epithelium.
30. The method according to claim 29, wherein said mucosal
epithelium is intestinal mucosal epithelium.
31. The method according to claim 27, wherein said attenuated
Shigella cells are inactivated.
32. The method of claim 27, wherein said mutation is a mutation in
the wild-type asd gene within said Shigella cells.
Description
[0001] The development of this invention was supported by the
University of Maryland, Baltimore, Md.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for introducing
endogenous or foreign genes into animal cells using live invasive
bacteria as vectors. The method allows for the delivery of
eukaryotic expression cassettes encoding the endogenous or foreign
genes into animal cells or animal tissue, and is useful for
expressing, e.g., vaccine antigens, therapeutic agents,
immunoregulatory agents, antisense RNAs, and catalytic RNAs, in
animal cells or animal tissue.
BACKGROUND OF THE INVENTION
I. Live Bacterial Vector Vaccines
[0003] The advent of recombinant DNA technology has greatly
accelerated the development of vaccines to control epidemic,
endemic, and pandemic infectious diseases (Woodrow et al, New
Generation Vaccines: The Molecular Approach, Eds., Marcel Dekker,
Inc., New York, N.Y. (1989); Cryz, Vaccines and Immunotherapy, Ed.,
Pergamon Press, New York, N.Y. (1991); and Levine et al, Ped. Ann.,
22:719-725 (1993)). In particular, this technology has enabled the
growth of a new class of vaccines called bacterial vector vaccines
(Curtiss, In: New Generation Vaccines: The Molecular Approach, Ed.,
Marcel Dekker, Inc., New York, N.Y., pages 161-188 and 269-288
(1989); and Mims et al, In: Medical Microbiology, Eds., Mosby-Year
Book Europe Ltd., London (1993)). These vaccines can enter the
host, either orally, intranasally or parenterally. Once gaining
access to the host, the bacterial vector vaccines express an
engineered prokaryotic expression cassette contained therein that
encodes a foreign antigen(s). Foreign antigens can be any protein
(or part of a protein) or combination thereof from a bacterial,
viral, or parasitic pathogen that has vaccine properties (New
Generation Vaccines: The Molecular Approach, supra; Vaccines and
Immunotherapy, supra; Hilleman, Dev. Biol. Stand., 82:3-20 (1994);
Formal et al, Infect. Immun. 34:746-751 (1981); Gonzalez et al, J.
Infect. Dis., 169:927-931 (1994); Stevenson et al, FEMS Lett.,
28:317-320 (1985); Aggarwal et al, J. Exp. Med., 172:1083-1090
(1990); Hone et al, Microbial. Path., 5:407-418 (1988); Flynn et
al, Mol. Microbiol., 4:2111-2118 (1990); Walker et al, Infect.
Immun., 60:4260-4268 (1992); Cardenas et al, Vacc., 11:126-135
(1993); Curtiss et al, Dev. Biol. Stand., 82:23-33 (1994); Simonet
et al, Infect. Immun., 62:863-867 (1994); Charbit et al, Vacc.,
11:1221-1228 (1993); Turner et al, Infect. Immun., 61:5374-5380
(1993); Schodel et al, Infect. Immun., 62:1669-1676 (1994); Schodel
et al, J. immunol., 145:4317-4321 (1990); Stabel et al, Infect.
Immun., 59:2941-2947 (1991); Brown, J. Infect. Dis., 155:86-92
(1987); Doggett et al, Infect. Immun., 61:1859-1866 (1993); Brett
et al, Immunol., 80:306-312 (1993); Yang et al, J. Immunol.,
145:2281-2285 (1990); Gao et al, Infect. Immun., 60:3780-3789
(1992); and Chatfield et al, Bio/Technology, 10:888-892 (1992)).
Delivery of the foreign antigen to the host tissue using bacterial
vector vaccines results in host immune responses against the
foreign antigen, which provide protection against the pathogen from
which the foreign antigen originates (Mims, The Pathogenesis of
Infectious Disease, Academic Press, London (1987); and New
Generation Vaccines: The Molecular Approach, supra).
[0004] Of the bacterial vector vaccines, live oral Salmonella
vector vaccines have been studied most extensively. There are
numerous examples showing that Salmonella vectors are capable of
eliciting humoral and cellular immunity against bacterial, viral
and parasitic antigens (Formal et al, Infect. Immun., 34:746-751
(1981); Gonzalez et al, supra; Stevenson et al, supra; Aggarwal et
al, supra; Hone et al, supra; Flynn et al, supra; Walker et al,
supra; Cardenas et al, supra; Curtiss et al, supra; Simonet et al,
supra; Charbit et al, supra; Turner et al, supra; Schodel et al,
supra, Schodel et al (1990), supra; Stabel et al, supra; Brown,
supra; Doggett et al, supra; Brett et al, supra; Yang et al, supra;
Gao et al, supra; and Chatfield et al, supra). These humoral
responses occur in the mucosal (Stevenson et al, supra; Cardenas et
al, supra; Walker et al, supra; and Simonet et al, supra), and
systemic compartments (Gonzalez et al, supra; Stevenson et al,
supra; Aggarwal et al, supra; Hone et al, supra; Flynn et al,
supra; Walker et al, supra; Cardenas et al, supra; Curtiss et al,
supra; Simonet et al, supra; Charbit et al, supra; Turner et al,
supra; Schodel et al, supra, Schodel et al (1990), supra; Stabel et
al, supra; Brown, supra; Doggett et al, supra; Brett et al, supra;
Yang et al, supra; Gao et al, supra; and Chatfield et al, supra).
Live oral Salmonella vector vaccines also elicit T cell responses
against foreign antigens (Wick et al, Infect. Immun., 62:4542-4548
(1994)). These include antigen-specific cytotoxic CD8.sup.+ T cell
responses (Gonzalez et al, supra; Aggarwal et al, supra; Flynn et
al, supra; Turner et al, supra; and Gao et al, supra).
[0005] Ideally, bacterial vector vaccines are genetically defined,
attenuated and well-tolerated by the recipient animal or human, and
retain immunogenicity (Hone et al, Vaccine, 9:810-816 (1991);
Tacket et al, Infect. Immun., 60:536-541 (1992); Hone et al, J.
Clin. Invest., 90:412-420 (1992); Chatfield et al, Vaccine, 10:8-11
(1992); Tacket et al, Vaccine, 10:443-446 (1992); and Mims, supra).
Recently, the number of potential bacterial vector vaccines for the
delivery of prokaryotic expression cassettes has grown. They now
include, but are not restricted to Yersinia enterocolitica (van
Damme et al, Gastroenterol., 103:520-531 (1992)), Shigella spp.
(Noriega et al, Infect. Immun., 62:5168-5172 (1994)), Vibrio
cholerae (Levine et al, In: Vibrio cholerae, Molecular to Global
Perspectives, Wachsmuth et al, Eds, ASM Press, Washington, D.C.,
pages 395-414 (1994)), Mycobacterium strain BCG (Lagranderie et al,
Vaccine, 11:1283-1290 (1993); Flynn, Cell. Molec. Biol., 40(Suppl.
1):31-36 (1994)), and Listeria monocytogenes (Schafer et al, J.
Immunol., 149:53-59 (1992)) vector vaccines.
II. Eukaryotic and Prokaryotic Expression Cassettes
[0006] Normally, an expression cassette is composed of a promoter
region, a transcriptional initiation site, a ribosome binding site
(RBS), an open reading frame (orf) encoding a protein (or fragment
thereof), with or without sites for RNA splicing (only in
eukaryotes), a translational stop codon, a transcriptional
terminator and post-transcriptional poly-adenosine processing sites
(only in eukaryotes) (Wormington, Curr. Opin. Cell Biol., 5:950-954
(1993); Reznikoff et al, Maximizing Gene Expression, Eds.,
Butterworths, Stoneham, Mass. (1986)). The promoter region, the
RBS, the splicing sites, the transcriptional terminator and
post-transcriptional poly-adenosine processing sites are markedly
different in eukaryotic expression cassettes than those found in
prokaryotic expression cassettes (Wasylyk, In: Maximizing Gene
Expression, supra, pages 79-99; Reznikoff et al, In: Maximizing
Gene Expression, supra, pages 1-34; and Lewin, Genes V, Oxford
University Press, Oxford (1994)). These differences prevent
expression of prokaryotic expression cassettes in eukaryotic cells
and visa versa (Miller et al, Mol. Micro., 4:881-893 (1990); and
Williamson et al, Appl. Env. Micro., 60:771-776 (1994)).
[0007] Prokaryotic promoters are not active in eukaryotic cells and
eukaryotic promoters are not active in prokaryotic cells (Eick et
al, Trends in Genetics, 10:292-296 (1994)). The basis for the
functional diversity of eukaryotic versus prokaryotic promoters is
mediated by RNA-polymerase, transcription regulatory factors and
the DNA structure of the promoter (Eick et al, supra).
[0008] RNA polymerases are DNA-binding proteins that recognize
specific sequences in the DNA of promoter regions. RNA polymerases
catalyze the synthesis of RNA molecules by polymerizing nucleoside
triphosphates in the specific order that is dictated by the DNA
coding sequence (Libby et al, Mol. Micro., 5:999-1004 (1991);
Kerppola et al, FASEB J., 5:2833-2842 (1991); Alberts et al,
Molecular Biology of the Cell, Eds., Garland Publishing Inc, New
York, N.Y. (1994); Watson et al, Molecular Biology of the Gene,
Vol. 1, Eds., The Benjamin/Cummings Publishing Comp. Inc., Menlo
Park Calif. (1987); and Lewin, supra). RNA polymerases of
prokaryotes typically are composed of two identical .alpha.
subunits and two similar, but non-identical, .beta. and .beta.'
subunits (Ishihama, Mol. Micro., 6:3283-3288 (1992); Watson et al,
supra; Alberts et al, supra; and Lewin, supra). The specificity of
prokaryotic RNA polymerases for a given promoter region is mediated
by specific .sigma. factors that recognize core sequences encoded
by the DNA in the promoter regions (Libby et al, supra; and Lewin,
supra).
[0009] In eukaryotic cells, there are three RNA polymerases. Each
of the different RNA polymerases contain 10 to 15 different
subunits and each performs a different function (Kerppola et al,
supra; Larson et al, Biochem. Cell. Biol., 69:5-22 (1991);
Archambault et al, Microbiol. Rev., 57:703-724 (1993); Watson et
al, supra; Alberts et al, supra; and Lewin, supra). In addition,
specific DNA-binding factors may be required for the association of
eukaryotic RNA polymerases to the DNA in a promoter region (Darnell
et al, Molecular Cell Biology, Scientific American Books, Inc.,
W.H. Freeman and Co., New York, N.Y. (1990); Hori et al, Curr.
Opin. Gen. Devel., 4:236-244 (1994); Lewin, supra; Watson et al,
supra; and Alberts et al, supra). These binding factors recognize
specific sequences in the DNA, and also interact with the
eukaryotic RNA polymerases.
[0010] There is little similarity between the primary DNA sequence
of prokaryotic promoters and the primary DNA sequence of eukaryotic
promoters. The DNA structure of prokaryotic promoters is relatively
simple, consisting of -10 and -35 regions and proximal regulatory
sequences (Darnell et al, supra; Lewin, supra; Watson et al, supra;
and Alberts et al, supra). Prokaryotic promoters are located
upstream of the transcription start site. Eukaryotic promoters, in
contrast, are composed of a core unit, which is usually located
from 50 bp upstream to 20 bp downstream of the transcriptional
start site (Darnell et al, supra; Lewin, supra; Watson et al,
supra; and Alberts et al, supra), and enhancer sequences that are
located from about 100 to 200 bp upstream of the transcriptional
start, but also can be located in distal locations (Sonenberg,
Curr. Opin. Gen. Devel., 4:310-315 (1994); Geballe et al, Trends
Bio. Sci., 1:159-164 (1994); and Lewin, supra).
[0011] The RBS is the site recognized by the ribosome for binding
to the 5' end of messenger RNA (mRNA) molecules. This binding is
essential for the translation of hRNA into a protein by the
ribosome. In prokaryotes, the RBS in the 5' end of the mRNA
molecule is a sequence that is complementary to the 3' end of the
small ribosomal RNA molecule (5S rRNA) (Chatterji et al, Ind. J.
Biochem. Biophys., 29:128-134 (1992); and Darnell et al, supra;
Lewin, supra; Watson et al, supra; and Watson et al, supra). The
presence of the RBS promotes binding of the ribosome to the 5' end
of the nascent mRNA molecule. Translation is then initiated at the
first AUG codon encountered by the scanning ribosome (Darnell et
al, supra; Lewin, supra; Watson et al, supra; and Alberts et al,
supra). At present, no such recognition pattern has been observed
in eukaryotic mRNA-ribosome interactions (Eick et al, supra). In
addition, prior to initiation of translation of eukaryotic mRNA,
the 5' end of the mRNA molecule is "capped" by addition of
methylated guanylate to the first mRNA nucleotide residue (Darnell
et al, supra; Lewin, supra; Watson et al, supra; and Alberts et al,
supra). It has been proposed that recognition of the translational
start site in mRNA by the eukaryotic ribosomes involves recognition
of the cap, followed by binding to specific sequences surrounding
the initiation codon on the mRNA. It is possible for cap
independent translation initiation to occur and/or to place
multiple eukaryotic coding sequences within a eukaryotic expression
cassette if a cap-independent translation enhancer (CITE) sequence,
such as derived from encephalomyocarditis virus (Duke et al, J.
Virol., 66:1602-1609 (1992)), is included prior to or between the
coding regions. However, the initiating AUG codon is not
necessarily the first AUG codon encountered by the ribosome (Louis
et al, Molec. Biol. Rep., 13:103-115 (1988); and Voorma et al,
Molec. Biol. Rep., 19:139-145 (1994); Lewin, supra; Watson et al,
supra; and Alberts et al, supra). Thus, RBS binding sequences in
eukaryotes are sufficiently divergent from that of prokaryotic RBS
such that the two are not interchangeable.
[0012] Termination of transcription in prokaryotes is mediated by
rho-independent and rho-dependent stem loops (Richardson, Crit.
Rev. Biochem. Mol. Biol., 28:1-30 (1993); Platt, Molec. Microbiol.,
11:983-990 (1994); and Lewin, supra). In contrast, terminator loops
are not commonly found downstream of eukaryotic expression
cassettes, and transcription often extends beyond the end of the
open reading frame (Tuite et al, Mol. Biol. Reps., 19:171-181
(1994)). However, usually the over-extended mRNA is specifically
cleaved by endonucleases, and the 3' end of the mRNA is
poly-adenylated by poly-A polymerase (Proudfoot, Cell, 64:671-674
(1991); Wahle, Bioassays, 14:113-118 (1992); Lewin, supra; and
Watson et al, supra). Sequences that are recognized by the
endonucleases and poly-A polymerase must be included in the 3' end
of the mRNA molecule for these post-translation modifications to
occur. Polyadenylation of the 3' end of mRNA molecules is thought
to be a necessary step prior to transport of mRNA to the cytoplasm
of eukaryotic cells and translation into proteins (Sachs et al, J.
Biol. Chem., 268:22955-22958 (1993); and Sachs, Cell, 74:413-421
(1993)). A eukaryotic expression cassette does not need to code for
a functional gene product, i.e., it may also code for a partial
gene product which acts as an inhibitor of a eukaryotic enzyme
(Warne et al, Nature, 364:352-355 (1993); and Wang, J. Cell
Biochem., 45:49-53 (1991)), an antisense RNA (Magrath, Ann. Oncol.,
5(Suppl 1):67-70 (1994); Milligan et al, Ann. NY Acad. Sci.,
716:228-241 (1994); and Schreier, Pharma. Acta Helv., 68:145-159
(1994)), a catalytic RNA (Cech, Biochem. Soc. Trans., 21:229-234
(1993); Cech, Gene, 135:33-36 (1993); Long et al, FASE J., 7:25-30;
and Rosi et al, Pharm. Therap., 50:245-254 (1991)), or any other
sequence which can be transcribed into RNA.
[0013] Due to a need for eukaryotic expression cassettes to study
the biology of eukaryotic cells, a number of eukaryotic expression
plasmids are now readily available. These include, but are not
limited to, commercial products from companies, such as Invitrogen
Corporation (San Diego, Calif.), Stratagene (La Jolla, Calif.),
ClonTech (Palo Alto, Calif.) and Promega Corporation (Madison,
Wis.). All of these plasmids contain the elements of a eukaryotic
expression cassette listed above, and many also contain a
prokaryotic promoter sequence such that the gene placed downstream
from the promoter sequences will be expressed in a prokaryotic as
well as in an eukaryotic cell, e.g., plasmid pSV.beta.-gal contains
the eukaryotic SV40 promoter and the prokaryotic gpt promoter which
allows for the expression of the .beta.-galactosidase gene in
either prokaryotic cells or eukaryotic cells (Promega Corp.).
III. Delivery of Eukaryotic Expression Cassettes to Plant Cells
[0014] The use of Agrobacterium tumerfacium Ti plasmid to stably
deliver DNA to plant cells has been a fundamental component of the
boom in plant biotechnology. This system is unique in that it uses
a pilus-like structure which binds to the plant cell via specific
receptors, and then through a process that resembles bacterial
conjugation, delivers the Ti plasmid-linked. DNA to the plant cell
(Zambryski, Ann. Rev. Genet., 22:1-30 (1988); Lessl et al, Cell,
77:321-324 (1994); and Walden et al, Eur. J. Biochem., 192:563-576
(1990)). The specificity of this delivery system for plants,
however, renders it ineffective for delivery of DNA to animal cells
(Chilton, Proc. Natl. Acad. Sci., USA, 90:3119-3120 (1993); and
Walden et al, supra).
IV. Delivery of Eukaryotic Expression Cassettes to Animal Cells
[0015] There are several techniques for introducing DNA into animal
cells cultured in vitro. These include chemical methods (Felgner et
al, Proc. Natl. Acad. Sci., USA, 84:7413-7417 (1987); Bothwell et
al, Methods for Cloning and Analysis of Eukaryotic Genes, Eds.,
Jones and Bartlett Publishers Inc., Boston, Mass. (1990), Ausubel
et al, Short Protocols in Molecular Biology, John Wiley and Sons,
New York, N.Y. (1992); and Farhood, Annal. N.Y. Acad. Sci.,
716:23-34 (1994)), use of protoplasts (Bothwell, supra) or
electrical pulses (Vatteroni et al, Mutn. Res., 291:163-169 (1993);
Sabelnikov, Prog. Biophys. Mol. Biol., 62:119-152 (1994); Brothwell
et al, supra; and Ausubel et al, supra), use of attenuated viruses
(Moss, Dev. Biol. Stan., 82:55-63 (1994); and Brothwell et al,
supra), as well as physical methods (Fynan et al, supra; Johnston
et al, Meth. Cell Biol, 43(Pt A):353-365 (1994); Brothwell et al,
supra; and Ausubel et al, supra).
[0016] Successful delivery of DNA to animal tissue has been
achieved by cationic liposomes (Watanabe et al, Mol. Reprod. Dev.,
38:268-274 (1994)), direct injection of naked DNA into animal
muscle tissue (Robinson et al, Vacc., 11:957-960 (1993); Hoffman et
al, Vacc., 12:1529-1533; (1994); Xiang et al, Virol., 199:132-140
(1994); Webster et al, Vacc., 12:1495-1498 (1994); Davis et al,
Vacc., 12:1503-1509 (1994); and Davis et al, Hum. Molec. Gen.,
2:1847-1851 (1993)), and embryos (Naito et al, Mol. Reprod. Dev.,
39:153-161 (1994); and Burdon et al, Mol. Reprod. Dev., 33:436-442
(1992)), or intradermal injection of DNA using "gene gun"
technology (Johnston et al, supra). A limitation of these
techniques is that they only efficiently deliver DNA to parenteral
sites. At present, effective delivery of eukaryotic expression
cassettes to mucosal tissue has been met with limited success. This
is presumably due to poor access to these sites, toxicity of the
delivery vehicles or instability of the delivery vehicles when
delivered orally.
[0017] The commercial application of DNA delivery technology to
animal cells is broad and includes delivery of vaccine antigens
(Fynan et al, Proc. Natl. Acad. Sci., USA, 90:11478-11482 (1993)),
immunotherapeutic agents, and gene therapeutic agents (Darris et
al, Cancer, 74(3 Suppl.):1021-1025 (1994); Magrath, Ann. Oncol.,
5(Suppl 1):67-70 (1994); Milligan et al, Ann. NY Acad. Sci.,
716:228-241 (1994); Schreier, Pharma. Acta Helv., 68:145-159
(1994); Cech, Biochem. Soc. Trans., 21:229-234 (1993); Cech, Gene,
135:33-36 (1993); Long et al, FASEB J., 7:25-30 (1993); and Rosi et
al, Pharm. Therap., 50:245-254 1991)).
[0018] The delivery of endogenous and foreign genes to animal
tissue for gene therapy has shown significant promise in
experimental animals and volunteers (Nabel, Circulation, 91:541-548
(1995); Coovert et al, Curr. Opin. Neuro., 7:463-470 (1994); Foa,
Bill. Clin. Haemat., 7:421-434 (1994); Bowers et al, J. Am. Diet.
Assoc., 95:53-59 (1995); Perales et al, Eur. J. Biochem.,
226:255-266 (1994); Danko et al, Vacc., 12:1499-1502 (1994); Conry
et al, Canc. Res., 54:1164-1168 (1994); and Smith, J. Hemat.,
1:155-166 (1992)). Recently, naked DNA vaccines carrying eukaryotic
expression cassettes have been used to successfully immunize
against influenza both in chickens (Robinson et al, supra) and
ferrets (Webster et al, Vacc., 12:1495-1498 (1994)); against
Plasmodium yoelii in mice (Hoffman et al, supra); against rabies in
mice (Xiang et al, supra); against human carcinoembryonic antigen
in mice (Conry et al, supra) and against hepatitis B in mice (Davis
et al, supra). These observations open the additional possibility
that delivery of endogenous and foreign genes to animal tissue
could be used for prophylactic and therapeutic applications.
[0019] Therefore, there is a need to deliver eukaryotic expression
cassettes, encoding endogenous or foreign genes that are vaccines
or therapeutic agents to animal cells or tissue. In particular, a
method that delivers eukaryotic expression cassettes to mucosal
surfaces is highly desirable. Bacterial vector vaccines have been
used in the past to deliver foreign antigens encoded on prokaryotic
expression cassettes to animal tissue at mucosal sites.
[0020] The present invention describes a novel and unexpected
finding that invasive bacteria are capable of delivering eukaryotic
expression cassettes to animal cells and tissue. An important
aspect of using live invasive bacteria to deliver eukaryotic
expression cassettes is that they are capable of delivering DNA to
mucosal sites.
[0021] Heretofore, there has been no documented demonstration of
live bacteria invading animal cells and introducing a eukaryotic
expression cassette(s), which then is expressed by the infected
cells and progeny thereof. That is, the present invention provides
the first documentation of genetic exchange between live invasive
bacteria and animals cells. Heretofore, foreign antigen delivery by
live bacterial vector vaccines merely involved delivery of
prokaryotic expression cassettes to and expression of the foreign
antigen by the bacterial vaccine vector, in animal cells or
tissues. In contrast, the present invention involves the delivery
of eukaryotic expression cassettes by live bacterial strains to
animal cells in vitro or to cells in animal tissue, and expression
of the eukaryotic expression cassettes by the animal cell or cells
in animal tissue.
SUMMARY OF THE INVENTION
[0022] An object of the present invention is to use live invasive
bacteria to deliver one or more eukaryotic expression cassettes to
animal cells or animal tissue.
[0023] Another object of the present invention is to use live
invasive bacteria to deliver one or more eukaryotic expression
cassettes encoding a vaccine antigen(s) to animal cells or animal
tissue.
[0024] Another object of the present invention is to use live
invasive bacteria to deliver one or more eukaryotic expression
cassettes encoding therapeutic agents to animal cells or animal
tissue.
[0025] Yet another objective of the present invention is to use
live invasive bacteria to deliver one or more eukaryotic expression
cassettes encoding biologically active RNA species to animal cells
or animal tissue.
[0026] These and other objects of the present invention, which will
be apparent from the detailed description of the invention provided
hereinafter, have been met in one embodiment by a method for
introducing and expressing a gene in animal cells comprising
infecting said animal cells with live invasive bacteria, wherein
said bacteria contain a eukaryotic expression cassette encoding
said gene.
[0027] In another embodiment, the present invention relates to live
invasive bacteria which contain one or more eukaryotic expression
cassettes encoding an endogenous or foreign gene.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIGS. 1A and 1B show the colony forming units per well of S.
flexneri .DELTA.aroA.DELTA.virG containing the p.beta.-gal+SV40
expression cassette (FIG. 1A), or containing the p.beta.-gal-SV40
expression cassette (FIG. 1B), that survive intra-cellularly within
HeLa cells 6 hours, 24 hours, 48 hours, 72 hours and 92 hours
post-bactofection.
[0029] FIG. 2 shows the cell number per well of HeLa cells present
6 hours, 24 hours, 48 hours, 72 hours and 92 hours
post-bactofection with S. flexneri .DELTA.aroA.DELTA.virG
containing the p.beta.-gal+SV40 expression cassette.
[0030] FIGS. 3A and 3B show the colony forming units per well of S.
flexneri .DELTA.asd containing the p.beta.-gal+SV40 expression
cassette (FIG. 3A), or containing the p.beta.-gal-SV40 expression
cassette (FIG. 3B), that survive intra-cellularly within HeLa cells
6 hours, 24 hours, 48 hours and 96 hours post-bactofection.
[0031] FIG. 4 shows the cell number per well of HeLa cells present
6 hours, 24 hours, 48 hours and 96 hours post-bactofection with S.
flexneri .DELTA.asd containing the p.beta.-gal+SV40 expression
cassette.
DETAILED DESCRIPTION OF THE INVENTION
[0032] As discussed above, in one embodiment, the present invention
relates to a method for introducing and expressing a gene in animal
cells comprising infecting said animal cells with live invasive
bacteria, wherein said bacteria contain a eukaryotic expression
cassette encoding said gene.
[0033] Animal cells are defined as nucleated, non-chloroplast
containing cells derived from or present in multicellular organisms
whose taxanomic position lies within the kingdom animalia. The
cells may be present in the intact animal, a primary cell culture,
explant culture or a transformed cell line. The particular tissue
source of the cells is not critical to the present invention.
[0034] The recipient animal cells employed in the present invention
are not critical thereto and include cells present in or derived
from all organisms within the kingdom animalia, such as those of
the families mammalia, pisces, avian, reptilia.
[0035] Preferred animal cells are mammalian cells, such as humans,
bovine, ovine, porcine, feline, buffalo, canine, goat, equine,
donkey, deer, and primate cells. The most preferred animal cells
are human cells.
[0036] Examples of human cell lines include but are not limited to
ATCC Nos. CCL 62, CCL 159, HTB 151, HTB 22, CCL 2, CRL 1634, CRL
8155, HTB 61, and HTB104.
[0037] Examples of bovine cell lines include ATCC Nos. CRL 6021,
CRL 1733, CRL 6033, CRL 6023, CCL 44 and CRL 1390.
[0038] Examples of ovine cells lines include ATCC Nos. CRL 6540,
CRL 6538, CRL 6548 and CRL 6546.
[0039] Examples of porcine cell lines include ATCC Nos. CL 184, CRL
6492, and CRL 1746.
[0040] Examples of feline cell lines include CRL 6077, CRL 6113,
CRL 6140, CRL 6164, CCL 94, CCL 150, CRL 6075 and CRL 6123.
[0041] Examples of buffalo cell lines include CCL 40 and CRL
6072.
[0042] Examples of canine cells include ATCC Nos. CRL 6213, CCL 34,
CRL 6202, CRL 6225, CRL 6215, CRL 6203 and CRL 6575.
[0043] Examples of goat derived cell lines include ATCC No. CCL 73
and ATCC No. CRL 6270.
[0044] Examples of horse derived cell lines include ATCC Nos. CCL
57 and CRL 6583.
[0045] Examples of deer cell lines include ATCC Nos. CRL
6193-6196.
[0046] Examples of primate derived cell lines include those from
chimpanzee's such as ATCC Nos. CRL 6312, CRL 6304, and CRL 1868;
monkey cell lines such as ATCC Nos. CRL 1576, CCL 26, and CCL 161;
orangautan cell line ATCC No. CRL 1850; and gorilla cell line ATCC
No. CRL 1854.
[0047] As used herein, "invasive bacteria" are bacteria that are
capable of delivering eukaryotic expression cassettes to animal
cells or animal tissue. "Invasive bacteria" include bacteria that
are naturally capable of entering the cytoplasm or nucleus of
animal cells, as well as bacteria that are genetically engineered
to enter the cytoplasm or nucleus of animal cells or cells in
animal tissue.
[0048] The particular naturally occurring invasive bacteria
employed in the present invention is not critical thereto. Examples
of such naturally-occurring invasive bacteria include, but are not
limited to, Shigella spp, Listeria spp., Rickettsia spp and
enteroinvasive Escherichia coli.
[0049] The particular Shigella strain employed is not critical to
the present invention. Examples of Shigella strains which can be
employed in the present invention include Shigella flexneri 2a
(ATCC No. 29903), Shigella sonnei (ATCC No. 29930), and Shigella
disenteriae (ATCC No. 13313). An attenuated Shigella strain, such
as Shigella flexneri 2a 2457T .DELTA.aroA.DELTA.virG mutant CVD
1203 (Noriega et al, supra), Shigella flexneri M90T .DELTA.icsA
mutant (Goldberg et al, Infect. Immun., 62:5664-5668 (1994)),
Shigella flexneri Y SFL114 aroD mutant (Karnell et al, Vacc.,
10:167-174 (1992)), and Shigella flexneri .DELTA.aroA.DELTA.aroD
mutant (Verma et al, Vacc., 9:6-9 (1991)) are preferably employed
in the present invention. Alternatively, new attenuated Shigella
spp. strains can be constructed by introducing an attenuating
mutation either singularly or in conjunction with one or more
additional attenuating mutations.
[0050] Attenuating mutations can be introduced into bacterial
pathogens using non-specific mutagenesis either chemically, using
agents such as N-methyl-N'-nitro-N-nitrosoguanidine, or using
recombinant DNA techniques; classic genetic techniques, such as
Tn10 mutagenesis, P22-mediated transduction, .lamda. phage mediated
crossover, and conjugational transfer; or site-directed mutagenesis
using recombinant DNA techniques. Recombinant DNA techniques are
preferable since strains constructed by recombinant DNA techniques
are far more defined. Examples of such attenuating mutations
include, but are not limited to: [0051] (i) auxotrophic mutations,
such as aro (Hoiseth et al, Nature, 291:238-239 (1981)), qua
(McFarland et al, Microbiol. Path., 3:129-141 (1987)), nad (Park et
al, J. Bact., 170:3725-3730 (1988), thy (Nnalue et al, Infect.
Immun., 55:955-962 (1987)), and asd (Curtiss, supra) mutations;
[0052] (ii) mutations that inactivate global regulatory functions,
such as cya (Curtiss et al, Infect. Immun., 55: 3035-3043 (1987) ),
crp (Curtiss et al (1987), supra), phoP/phoQ (Groisman et al, Proc.
Natl. Acad. Sci., USA, 86:7077-7081 (1989); and Miller et al, Proc.
Natl. Acad. Sci., USA, 86:5054-5058 (1989)), phoP.sup.c (Miller et
al, J. Bact., 172:2485-2490 (1990)) or ompR (Dorman et al, Infect.
Immun., 57:2136-2140 (1989)) mutations; [0053] (iii) mutations that
modify the stress response, such as recA (Buchmeier et al, Mol.
Micro., 7:933-936 (1993)), htrA (Johnson et al, Mol. Micro.,
5:401-407 (1991)), htpR (Neidhardt et al, Biochem. Biophys. Res.
Com., 100:894-900 (1981)), hsp (Neidhardt et al, Ann. Rev. Genet.,
18:295-329 (1984)) and groEL (Buchmeier et al, Sci., 248:730-732
(1990)) mutations; [0054] (iv) mutations in specific virulence
factors, such as lsyA (Libby et al, Proc. Natl. Acad. Sci., USA,
91:489-493 (1994)), pag or prg (Miller et al (1990), supra; and
Miller et al (1989), supra), iscA or virG (d'Hauteville et al, Mol.
Micro., 6:833-841 (1992)), plcA (Mengaud et al, Mol. Microbiol.,
5:367-72 (1991); Camilli et al, J. Exp. Med, 173:751-754 (1991)),
and act (Brundage et al, Proc. Natl. Acad. Sci., USA,
90:11890-11894 (1993)) mutations; [0055] (v) mutations that affect
DNA topology, such as topA (Galan et al, Infect. Immun.,
58:1879-1885 (1990)) mutation; [0056] (vi) mutations that block
biogenesis of surface polysaccharides, such as rfb, galE (Hone et
al, J. Infect. Dis., 156:164-167 (1987)) or via (Popoff et al, J.
Gen. Microbiol., 138:297-304 (1992)) mutations; [0057] (vii)
mutations that modify suicide systems, such as sacB (Recorbet et
al, App. Environ. Micro., 59:1361-1366 (1993); Quandt et al, Gene,
127:15-21 (1993)), nuc (Ahrenholtz et al, App. Environ. Micro.,
60:3746-3751 (1994)), hok, gef, kil, or phlA (Molin et al, Ann.
Rev. Microbiol., 47:139-166 (1993)) mutations; [0058] (viii)
mutations that introduce suicide systems, such as lysogens encoded
by P22 (Rennell et al, Virol., 143:280-289 (1985)), .lamda. murein
transglycosylase (Bienkowska-Szewczyk et al, Mol. Gen. Genet.,
184:111-114 (1981)) or S-gene (Reader et al, Virol., 43:623-628
(1971)); and [0059] (ix) mutations that disrupt or modify the
correct cell cycle, such as minB (de Boer et al, Cell, 56:641-649
(1989)) mutation.
[0060] The attenuating mutations can be either constitutively
expressed or under the control of inducible promoters, such as the
temperature sensitive heat shock family of promoters (Neidhardt et
al, supra), or the anaerobically induced nirB promoter (Harborne et
al, Mol. Micro., 6:2805-2813 (1992)) or repressible promoters, such
as uapA (Gorfinkiel et al, J. Biol. Chem., 268:23376-23381 (1993))
or gcv (Stauffer et al, J. Bact., 176:6159-6164 (1994)).
[0061] The particular Listeria strain employed is not critical to
the present invention. Examples of Listeria strains which can be
employed in the present invention include Listeria monocytogenes
(ATCC No. 15313). Attenuated Listeria strains, such as L.
monocytogenes .DELTA.actA mutant (Brundage et al, supra) or L.
monocytogenes .DELTA.plcA (Camilli et al, J. Exp. Med., 173:751-754
(1991)) are preferably used in the present invention.
Alternatively, new attenuated Listeria strains can be constructed
by introducing one or more attenuating mutations as described for
Shigella spp. above.
[0062] The particular Rickettsia strain employed is not critical to
the present invention. Examples of Rickettsia strains which can be
employed in the present invention include Ricketsia rickettsiae
(ATCC Nos. VR149 and VR891), Ricketsia prowaseckii (ATCC No.
VR233), Ricketsia tsutsugamuchi (ATCC Nos. VR312, VR150 and VR609),
Ricketsia mooseri (ATCC No. VR144), Ricketsia sibirica (ATCC No.
VR151), and Rochalimaea quitana (ATCC No. VR358). Attenuated
Ricketsia strains are preferably used in the present invention and
can be constructed by introducing one or more attenuating mutations
as described for Shigella spp. above.
[0063] The particular enteroinvasive Escherichia strain employed is
not critical to the present invention. Examples of enteroinvasive
Escherichia strains which can be employed in the present invention
include Escherichia coli strains 4608-58, 1184-68, 53638-C-17,
13-80, and 6-81 (Sansonetti et al, Ann. Microbiol. (Inst. Pasteur),
132A:351-355 (1982)). Attenuated enteroinvasive Escherichia strains
are preferably used in the present invention and can be constructed
by introducing one or more attenuating mutations as described for
Shigella spp. above.
[0064] Examples of bacteria which can be genetically engineered to
be invasive include, but are not limited to, Yersinia spp.,
Escherichia spp., Klebsiella spp., Bordetella spp., Neisseria spp.,
Aeromonas spp., Franciesella spp., Corynebacterium spp.,
Citrobacter spp., Chlamydia spp., Hemophilus spp., Brucella spp.,
Mycobacterium spp., Legionella spp., Rhodococcus spp., Pseudomonas
spp., Helicobacter spp., Salmonella spp., Vibrio spp., Bacillus
spp., and Erysipelothrix spp. These organisms can be engineered to
mimic the invasion properties of Shigella spp., Listeria spp.,
Rickettsia spp., or enteroinvasive E. coli spp. by inserting genes
that enable them to access the cytoplasm of an animal cell.
[0065] Examples of such genes include the invasive proteins of
Shigella, hemolysin or the invasion plasmid of Escherichia, or
listeriolysin O of Listeria, as such techniques are known to result
in strains that are capable of entering the cytoplasm of infected
animal cells (Formal et al, Infect. Immun., 46:465 (1984); Bielecke
et al, Nature, 345:175-176 (1990); Small et al, In:
Microbiology-1986, pages 121-124, Levine et al, Eds., American
Society for Microbiology, Washington, D.C. (1986); and Zychlinsky
et al, Molec. Micro., 11:619-627 (1994)). Any gene or combination
of genes, from one or more sources, that mediates entry into the
cytoplasm of animal cells will suffice. Thus, such genes are not
limited to bacterial genes, and include viral genes, such as
influenza virus hemagglutinin HA-2 which promotes endosmolysis
(Plank et al, J. Biol. Chem., 269:12918-12924 (1994)).
[0066] The above invasive genes can be introduced into the target
strain using chromosome or plasmid mobilization (Miller, A Short
Course in Bacterial Genetics, Cold Spring Harbor Laboratory Press,
Cold Spring Harbor, N.Y. (1992); Bothwell et al, supra; and Ausubel
et al, supra), bacteriophage-mediated *transduction (de Boer,
supra; Miller, supra; and Ausubel et al, supra), or chemical
(Bothwell et al, supra; Ausubel et al, supra; Felgner et al, supra;
and Farhood, supra), electroporation (Bothwel et al, supra; Ausubel
et al, supra; and Sambrook, Molecular Cloning: A Laboratory Manual,
Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.) and
physical transformation techniques (Johnston et al, supra; and
Bothwell, supra). The genes can be incorporated on bacteriophage
(de Boer et al, Cell, 56:641-649 (1989)), plasmids vectors (Curtiss
et al, supra) or spliced into the chromosome (Hone et al, supra) of
the target strain.
[0067] The particular Yersinia strain employed is not critical to
the present invention. Examples of Yersinia strains which can be
employed in the present invention include Y. enterocolitica (ATCC
No. 9610) or Y. pestis (ATCC No. 19428). Attenuated Yerinia
strains, such as Y. enterocolitica Ye03-R2 (al-Hendy et al, Infect.
Immun., 60:870-875 (1992)) or Y. enterocolitica aroA (O'Gaora et
al, Micro. Path., 9:105-116 (1990)) are preferably used in the
present invention. Alternatively, new attenuated Yersinia strains
can be constructed by introducing one or more attenuating mutations
as described for Shigella spp. above.
[0068] The particular Escherichia strain employed is not critical
to the present invention. Examples of Escherichia strains which can
be employed in the present invention include E. coli H10407
(Elinghorst et al, Infect. Immun., 60:2409-2417 (1992)), and E.
coli EFC4, CFT325 and CPZ005 (Donnenberg et al, J. Infect. Dis.,
169:831-838 (1994)). Attenuated Escherichia strains, such as the
attenuated turkey pathogen E. coli O2 carAB mutant (Kwaga et al,
Infect. Immun., 62:3766-3772 (1994)) are preferably used in the
present invention. Alternatively, new attenuated Escherichia
strains can be constructed by introducing one or more attenuating
mutations as described for Shigella spp. above.
[0069] The particular Klebsiella strain employed is not critical to
the present invention. Examples of Klebsiella strains which can be
employed in the present invention include K. pneuoniae (ATCC No.
13884). Attenuated Klebsiella strains are preferably used in the
present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0070] The particular Bordetella strain employed is not critical to
the present invention. Examples of Bordetella strains which can be
employed in the present invention include B. bronchiseptica (ATCC
No. 19395). Attenuated Bordetella strains are preferably used in
the present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0071] The particular Neisseria strain employed is not critical to
the present invention. Examples of Neisseria strains which can be
employed in the present invention include N. meningitidis (ATCC No.
13077) and N. gonorrhoeae (ATCC No. 19424). Attenuated Neisseria
strains, such as N. gonorrhoeae MS11 aro mutant (Chamberlain et al,
Micro. Path., 15:51-63 (1993)) are preferably used in the present
invention. Alternatively, new attenuated Neisseria strains can be
constructed by introducing one or more attenuating mutations as
described for Shigella spp. above.
[0072] The particular Aeromonas strain employed is not critical to
the present invention. Examples of Aeromonas strains which can be
employed in the present invention include A. eucrenophila (ATCC No.
23309). Alternatively, new attenuated Aeromonas strains can be
constructed by introducing one or more attenuating mutations as
described for Shigella spp. above.
[0073] The particular Franciesella strain employed is not critical
to the present invention. Examples of Franiesella strains which can
be employed in the present invention include F. tularensis (ATCC
No. 15482). Attenuated Franciesella strains are preferably used in
the present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0074] The particular Corynebacterium strain employed is not
critical to the present invention. Examples of Corynebacterium
strains which can be employed in the present invention include C.
pseudotuberculosis (ATCC No. 19410). Attenuated Corynebacterium
strains are preferably used in the present invention, and can be
constructed by introducing one or more attenuating mutations as
described for Shigella spp. above.
[0075] The particular Citrobacter strain employed is not critical
to the present invention. Examples of Citrobacter strains which can
be employed in the present invention include C. freundii (ATCC No.
8090). Attenuated Citrobacter strains are preferably used in the
present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0076] The particular Chlamydia strain employed is not critical to
the present invention. Examples of Chlamydia strains which can be
employed in the present invention include C. pneumoniae (ATCC No.
VR1310). Attenuated Chlamydia strains are preferably used in the
present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0077] The particular Hemophilus strain employed is not critical to
the present invention. Examples of Hemophilus strains which can be
employed in the present invention include H. sornnus (ATCC No.
43625). Attenuated Hemophilus strains are preferably used in the
present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0078] The particular Brucella strain employed is not critical to
the present invention. Examples of Brucella strains which can be
employed in the present invention include B. abortus (ATCC No.
23448). Attenuated Brucella strains are preferably used in the
present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0079] The particular Mycobacterium strain employed is not critical
to the present invention. Examples of Mycobacterium strains which
can be employed in the present invention include M. intracellulare
(ATCC No. 13950) and M. tuberculosis (ATCC No. 27294). Attenuated
Mycobacterium strains are preferably used in the present invention,
and can be constructed by introducing one or more attenuating
mutations as described for Shigella spp. above.
[0080] The particular Legionella strain employed is not critical to
the present invention. Examples of Legionella strains which can be
employed in the present invention include L. pneumophila (ATCC No.
33156). Attenuated Legionella strains, such as a L. pneumophila mip
mutant (Ott, FEMS Micro. Rev., 14:161-176 (1994)) are preferably
used in the present invention. Alternatively, new attenuated
Legionella strains can be constructed by introducing one or more
attenuating mutations as described for Shigella spp. above.
[0081] The particular Rhodococcus strain employed is not critical
to the present invention. Examples of Rhodococcus strains which can
be employed in the present invention include R. equi (ATCC No.
6939). Attenuated Rhodococcus strains are preferably used in the
present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0082] The particular Pseudomonas strain employed is not critical
to the present invention. Examples of Pseudomonas strains which can
be employed in the present invention include P. aeruginosa (ATCC
No. 23267). Attenuated Pseudomonas strains are preferably used in
the present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0083] The particular Helicobacter strain employed is not critical
to the present invention. Examples of Helicobacter strains which
can be employed in the present invention include H. mustelae (ATCC
No. 43772). Attenuated Helicobacter strains are preferably used in
the present invention, and can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0084] The particular Salmonella strain employed is not critical to
the present invention. Examples of Salmonella strains which can be
employed in the present invention include Salmonella typhi (ATCC
No. 7251) and S. typhimurium (ATCC No. 13311). Attenuated
Salmonella strains are preferably used in the present invention and
include S. typhi aroAaroD (Hone et al, Vacc., 2:810-816 (1991)) and
S. typhimurium aroA mutant (Mastroeni et al, Micro. Pathol.,
13:477-491 (1992))). Alteratively, new attenuated Salmonella
strains can be constructed by introducing one or more attenuating
mutations as described for Shigella spp. above.
[0085] The particular Vibrio strain employed is not critical to the
present invention. Examples of Vibrio strains which can be employed
in the present invention include Vibrio cholerae (ATCC No. 14035)
and Vibrio cincinnatiensis (ATCC No. 35912). Attenuated Vibrio
strains are preferably used in the present invention and include V.
cholerae RSI virulance mutant (Taylor et al, J. Infect. Dis.,
170:1518-1523 (1994)) and V. cholerae ctxA, ace, zot, cep mutant
(Waldor et al, J. Infect. Dis., 170:278-283 (1994)). Alternatively,
new attenuated Vibrio strains can be constructed by introducing one
or more attenuating mutations as described for Shigella spp.
above.
[0086] The particular Bacillus strain employed is not critical to
the present invention. Examples of Bacillus strains which can be
employed in the present invention include Bacillus subtilis (ATCC
No. 6051). Attenuated Bacillus strains are preferably used in the
present invention and include B. anthracis mutant pX01 (Welkos et
al, Micro. Pathol., 14:381-388 (1993)) and attenuated BCG strains
(Stover et al, Nat., 351:456-460 (1991)). Alternatively, new
attenuated Bacillus strains can be constructed by introducing one
or more attenuating mutations as described for Shigella spp.
above.
[0087] The particular Erysipelothrix strain employed is not
critical to the present invention. Examples of Erysipelothrix
strains which can be employed in the present invention include
Erysipelothrix rhusiopathiae (ATCC No. 19414) and Erysipelothrix
tonsillarum (ATCC No. 43339). Attenuated Erysipelothrix strains are
preferably used in the present invention and include E.
rhusiopathiae Kg-1a and Kg-2 (Watarai et al, J. Vet. Med. Sci.,
55:595-600 (1993)) and E. rhusiopathiae ORVAC mutant
(Markowska-Daniel et al, Int. J. Med. Microb. Virol. Parisit.
Infect. Dis., 277:547-553 (1992)). Alternatively, new attenuated
Erysipelothrix strains can be constructed by introducing one or
more attenuating mutations as described for Shigella spp.
above.
[0088] As discussed above, the recipient animal cells to which
bacteria deliver a eukaryotic expression cassette may be those
derived from fish, birds or reptiles.
[0089] Examples of bacteria which can naturally access the
cytoplasm of fish cells include, but are not limited to Aeromonas
salminocida (ATCC No. 33658) and Aeromonas schuberii (ATCC No.
43700). Attenuated bacteria are preferably used in the invention,
and include A. salmonicidia vapA (Gustafson et al, J. Mol. Biol.,
23-7:452-463 (1994)) or A. salmonicidia aromatic-dependent mutant
(Vaughan et al, Infect. Immun., 61:2172-2181 (1993)).
[0090] Examples of bacteria which can naturally access the
cytoplasm of avian cells include, but are not restricted to,
Salmonella galinarum (ATCC No. 9184), Salmonella enteriditis (ATCC
No. 4931) and Salmonella typhimurium (ATCC No. 6994). Attenuated
bacteria are preferred to the invention and include attenuated
Salmonella strains such as S. galinarum cya crp mutant (Curtiss et
al, (1987) supra) or S. enteritidis aroA aromatic-dependent mutant
CVL30 (Cooper et al, Infect. Immun., 62:4739-4746 (1994)).
[0091] Examples of bacteria which can naturally access the
cytoplasm of reptilian cells include, but are not restricted to,
Salmonella typhimurium (ATCC No. 6994). Attenuated bacteria are
preferable to the invention and include, attenuated strains such as
S. typhimuirum aromatic-dependent mutant (Hormaeche et al,
supra).
[0092] Again, the particular animal cells infected with the
invasive bacteria are not critical to the present invention, and
will depend on the host range of the invasive bacteria
employed.
[0093] For example, Shigella flexneri infects human and primate
cells, but rarely infects dogs and other animals (Kreig et al,
Bergey's Manual of Systematic Bacteriology, Eds., Wilkins and
Williams, Baltimore, Md. (1984)), while Aeromonas salminocida
infects salmonid cells (Austin et al, Bacterial Fish Pathogens:
Diseases in Farmed and Wild Fishes, Eds., Ellis Harwood Ltd.,
London (1987)).
[0094] The mucosal and systemic immune systems are
compartmentalized (Mesteky, J. Clin. Immunol., 7:265-270 (19870;
Newby, In: Local Immune Response of the Gut, Boca Raton, CRC Press,
Newby and Stocks Eds., pages 143-160 (1984); and Pascual et al.,
Immuno. Methods., 5:56-72 (1994)). Thus, antigens delivered to
mucosal surfaces elicit mucosal and systemic responses, whereas
parentally delivered antigens elicit mainly systemic responses but
only stimulate poor mucosal responses (Mesteky, supra). Moreover,
mucosal stimulation at one mucosal site (for example the intestine)
can result in development of immunity at other mucosal surfaces
(for example genital/urinary tract) (Mesteky, supra). This
phenomenon is referred to as the common mucosal system and is well
documented (Mesteky, supra; and Pascual et al, supra).
[0095] The development of mucosal vaccines has been hindered by the
poor immunogenicity of antigens when delivered by these routes. In
this context, antigens can be divided into two classes: those that
bind to intestinal surfaces and those that do not bind, where the
former are significantly more immunogenic than the latter (De
Aizpurua et al, J. Exp. Med., 176:440-451 (1988)). Similarly,
delivery of DNA molecules to mucosal surfaces is inefficient due to
the many natural host defenses found at these surfaces, such as the
gastric barrier and nucleases in the gastrointestinal tract, and
the thick mucous layer in the respiratory tract.
[0096] One approach to circumvent these natural barrier functions
of the host and enable access to mucosal compartment is to use
bacterial vectors (Curtiss, In: New Generation Vaccines: The
Molecular Approach, Ed., Marcel Dekker, Inc., New York, N.Y., pages
161-188 and 269-288 (1989); and Mims et al, In: Medical
Microbiology, Eds., Mosby-Year. Book Europe Ltd., London (1993)).
Certain enteric and respiratory pathogens, for example, E. coli,
Shigella, Listeria, Bordetella and Salmonella, are naturally
adapted for this application, as these organisms possess the
ability to attach to and invade host mucosal surfaces (Kreig et al,
Supra). Therefore, in the present invention, live oral bacterial
vectors can be engineered to deliver eukaryotic expression
cassettes to the host mucosal compartment.
[0097] Alternatively, any bacteria could be genetically engineered
to mimic mucosal tissue tropism and invasive properties, as
discussed above, that thereby allow said bacteria to invade mucosal
tissue, and deliver genes at those sites.
[0098] It is also possible to change the tissue specificity of the
invasive bacteria by expression of a gene product singularly or in
combination, e.g., the Plasmodium vivax reticulocyte binding
proteins-1 and -2 bind specifically to erythrocytes in humans and
primates (Galinski et al, Cell, 69:1213-1226 (1992)); Yersinia
Invasin recognizes .beta.1 integrin receptors (Isberg et al, Trends
Microbiol., 2:10-14 (1994)); asialoorosomucoid is a ligand for the
asilogycoprotein receptor on hepatocytes (Wu et al, J. Biol. Chem.,
263:14621-14624 (1988)); presence of insulin-poly-L-lysine has been
shown to target plasmid uptake to cells with an insulin receptor
(Rosenkranz et al, Expt. Cell Res., 199:323-329 (1992)); p60 of
Listeria monocytogenes allows for tropism for hepatocytes (Hess et
al, Infect. Immun., 63:2047-2053 (1995)) and Trypanosoma cruzi
expresses a 60 kDa surface protein which causes specific binding to
the mammalian extra-cellular matrix by binding to heparin, heparin
sulfate and collagen (Ortega-Barria et al, Cell, 67:411-421
(1991)).
[0099] The particular eukaryotic cassette employed in the present
invention is not critical thereto, and can be selected from, e.g.,
any of the many commercially available cassettes, such as pCEP4 or
pRc/RSV obtained from Invitrogen Corporation (San Diego, Calif.),
pXT1, pSG5, pPbac or pMbac obtained from Stratagene (La Jolla,
Calif.), pPUR or pMAM obtained from ClonTech (Palo Alto, Calif.),
and pSV.beta.-gal obtained from Promega Corporation (Madison,
Wis.), or synthesized either de novo or by, adaptation of a
publically or commercially available eukaryotic expression
system.
[0100] The individual elements within the eukaryotic expression
cassette can be derived from multiple sources and may be selected
to confer specificity in sites of action or longevity of the
cassettes in the recipient cell. Such manipulation of the
eukaryotic expression cassette can be done by any standard
molecular biology approach.
[0101] These cassettes usually are in the form of plasmids, and
contain various promoters well-known to be useful for driving
expression of genes in animal cells, such as the viral derived
SV40, CMV and, RSV promoters or eukaryotic derived .beta.-casein,
uteroglobin, .beta.-actin or tyrosinase promoters. The particular
promoter is not critical to the present, except in the case where
the object is to obtain expression in only selective cell types. In
this case, the promoter is selected to be one which is only active
in the selected cell type. Examples of tissue specific promoters
include, but are not limited to, .alpha. S1- and .beta.-casein
promoters which are specific for mammary tissue (Platenburg et al,
Trans. Res., 3:99-108 (1994); and Maga et al, Trans. Res., 3:36-42
(1994)); the phosphoenolpyruvate carboxykinase promoter which is
active in liver, kidney, adipose, jejunum and mammary tissue
(McGrane et al, J. Reprod. Fert., 41:17-23 (1990)); the tyrosinase
promoter which is active in lung and spleen cells, but not testes,
brain, heart, liver or kidney (Vile et al, Canc. Res., 54:6228-6234
(1994)); the involucerin promoter which is only active in
differentiating keratinocytes of the squamous epithelia (Carroll et
al, J. Cell Sci., 103:925-930 (1992)); and the uteroglobin promoter
which is active in lung and endometrium (Helftenbein et al, Annal.
N.Y. Acad. Sci., 622:69-79 (1991)).
[0102] Alternatively, cell specific enhancer sequences can be used
to control expression, for example human neurotropic papovirus JCV
enhancer regulates viral transcription in glial cells alone
(Remenick et al, J. Virol., 65:5641-5646 (1991)). Yet another way
to control tissue specific expression is to use a hormone
responsive element (HRE) to specify which cell lineages a promoter
will be active in, for example, the MMTV promoter requires the
binding of a hormone receptor, such as progesterone receptor, to an
upstream HRE before it is activated (Beato, FASEB J., 5:2044-2051
(1991); and Truss et al, J. Steroid Biochem. Mol. Biol., 41:241-248
(1992)).
[0103] Additional genetic elements may be included on the plasmid
in order to modify its behavior inside the recipient animal cell
(Hodgson, Bio/Technology, 13:222-225 (1995)). Such elements include
but are not limited to mammalian artificial chromosome elements or
elements from the autonomous replicating circular minichromosomes,
such as found in DiFi colorectal cancer cells, to allow stable
non-integrated retention of the expression cassette (Huxley et al,
Bio/Technology, 12:586-590 (1994); and Untawale et al, Canc. Res.,
53:1630-1636 (1993)), intergrase to direct integration of the
expression cassette into the recipient cells chromosome (Bushman,
Proc. Natl. Acad. Sci., USA, 91:9233-9237 (1994), the inverted
repeats from adeno-associated virus to promote non-homologous
integration into the recipient cells chromosome (Goodman et al,
Blood, 84:1492-1500 (1994), recA or a restriction enzyme to promote
homologous recombination (PCT Patent Publication No. WO9322443
(1993); and PCT Patent Publication No. WO9323534-A (1993)) or
elements that direct nuclear targeting of the eukaryotic expression
cassette (Hodgson, supra; and Lewin, supra). It may be advantageous
to encode some of these elements, such as intergrase, recA, and
restriction enzymes, in prokaryotic expression cassettes, either on
the same genetic element as the eukaryotic expression cassette or
alternatively on separate genetic elements. The placing of such
toxic or deleterious elements under the control of a prokaryotic
promoter ensures that these elements will only be transcribed or
translated prior to lysis of the bacterial cell, while the
prokaryotic translational and transcriptional machinery is
functioning, and thus a finite dose of the element encoded will be
delivered to the eukaryotic recipient.
[0104] In the present invention, the live invasive bacteria can
deliver eukaryotic expression cassettes encoding a gene into an
animal cell or animal tissue. The gene may be either a foreign gene
or a endogenous gene. As used herein, "foreign gene" means a gene
encoding a protein or fragment thereof or anti-sense RNA or
catalytic RNA, which is foreign to the recipient animal cell or
tissue, such as a vaccine antigen, immunoregulatory agent, or
therapeutic agent. An "endogenous gene" means a gene encoding a
protein or part thereof or anti-sense RNA or catalytic RNA which is
naturally present in the recipient animal cell or tissue.
[0105] The vaccine antigen may be a protein or antigenic fragment
thereof from viral pathogens, bacterial pathogens, and parasitic
pathogens. Alternatively, the vaccine antigen may be a synthetic
gene, constructed using recombinant DNA methods, which encode
antigens or parts thereof from viral, bacterial, parasitic
pathogens. These pathogens, can be infectious in humans, domestic
animals or wild animal hosts.
[0106] The antigen can be any molecule that is expressed by any
viral, bacterial, parasitic pathogen prior to or during entry into,
colonization of, or replication in their animal host.
[0107] Multiple eukaryotic expression cassettes can be delivered
that express any combination of viral, bacterial, parasitic
antigens, or synthetic genes encoding all or parts or any
combination of viral, bacterial, parasitic antigens.
[0108] The viral pathogens, from which the viral antigens are
derived, include, but are not limited to, Orthomyxoviruses, such as
influenza virus; Retroviruses, such as RSV and SIV, Herpesviruses,
such as EBV; CMV or herpes simplex virus; Lentiviruses, such as
human immunodeficiency virus; Rhabdoviruses, such as rabies;
Picornoviruses, such as poliovirus; Poxviruses, such as vaccinia;
Rotavirus; and Parvoviruses.
[0109] Examples of protective antigens of viral pathogens include
the human immunodeficiency virus antigens Nef, p24, gp120, gp41,
Tat, Rev, and Pol et al, Nature, 313:277-280 (1985)) and T cell and
B cell epitopes of gp120 (Palker et al, J. Immunol., 142:3612-3619
(1989)); the hepatitis B surface antigen (Wu et al, Proc. Natl.
Acad. Sci., USA, 86:4726-4730 (1989)); rotavirus antigens, such as
VP4 (Mackow et al, Proc. Natl. Acad. Sci., USA, 87:518-522 (1990))
and VP7 (Green et al, J. Virol., 62:1819-1823 (1988)), influenza
virus antigens such as hemagglutinin or nucleoprotein (Robinson et
al., Supra; Webster et al, Supra) and herpes simplex virus
thymidine kinase (Whitley et al, In: New Generation Vaccines, pages
825-854).
[0110] The bacterial pathogens, from which the bacterial antigens
are derived, include but are not limited to, Mycobacterium spp.,
Helicobacter pylori, Salmonella spp., Shigella spp., E. coli,
Rickettsia spp., Listeria spp., Legionella pneumoniae, Pseudomonas
spp., Vibrio spp., and Borellia burgdorferi.
[0111] Examples of protective antigens of bacterial pathogens
include the Shigella sonnei form 1 antigen (Formal et al, Infect.
Immun., 34:746-750 (1981)); the O-antigen of V. cholerae Inaba
strain 569B (Forrest et al, J. Infect. Dis., 159:145-146 (1989);
protective antigens of enterotoxigenic E. coli, such as the CFA/I
fimbrial antigen (Yamamoto et al, Infect. Immun., 50:925-928
(1985)) and the nontoxic B-subunit of the heat-labile toxin
(Clements et al, 46:564-569 (1984)); pertactin of Bordetella
pertussis (Roberts et al, Vacc., 10:43-48 (1992)), adenylate
cyclase-hemolysin of B. pertussis (Guiso et al, Micro. Path.,
11:423-431 (1991)), and fragment C of tetanus toxin of Clostridium
tetani (Fairweather et al, Infect. Immun., 58:1323-1326
(1990)).
[0112] The parasitic pathogens, from which the parasitic antigens
are derived, include but are not limited to, Plasmodium spp.,
Trypanosome spp., Giardia spp., Boophilus spp., Babesia spp.,
Entamoeba spp., Eimeria spp., Leishmania spp., Schistosome spp.,
Brugia spp., Fascida spp., Dirofilaria spp., Wuchereria spp., and
Onchocerea spp.
[0113] Examples of protective antigens of parasitic pathogens
include the circumsporozoite antigens of Plasmodium spp. (Sadoff et
al, Science, 240:336-337 (1988)), such as the circumsporozoite
antigen of P. bergerii or the circumsporozoite antigen of P.
falciparum; the merozoite surface antigen of Plasmodium spp.
(Spetzler et al, Int. J. Pept. Prot. Res., 43:351-358 (1994)); the
galactose specific lectin of Entamoeba histolytica (Mann et al,
Proc. Natl. Acad. Sci., USA, 88:3248-3252 (1991)), gp63 of
Leishmania spp. (Russell et al, J. Immunol., 140:1274-1278 (1988)),
paramyosin of Brugia malayi (Li et al, Mol. Biochem. Parasitol.,
49:315-323 (1991)), the triose-phosphate isomerase of Schistosoma
mansoni (Shoemaker et al, Proc. Natl. Acad. Sci., USA, 89:1842-1846
(1992)); the secreted globin-like protein of Trichostrongylus
colubriformis (Frenkel et al, Mol. Biochem. Parasitol., 50:27-36
(1992)); the glutathione-S-transferase's of Frasciola hepatica
(Hillyer et al, Exp. Parasitol., 75:176-186 (1992)), Schistosoma
bovis and S. japonicum (Bashir et al, Trop. Geog. Med., 46:255-258
(1994)); and KLH of Schistosoma bovis and S. japonicum (Bashir et
al, supra).
[0114] In the present invention, the live invasive bacteria can
also deliver eukaryotic expression cassettes encoding a therapeutic
agent to animal cells or animal tissue. For example, the eukaryotic
expression cassettes can encode tumor-specific, transplant, or
autoimmune antigens or parts thereof. Alternatively, the eukaryotic
expression cassettes can encode synthetic genes, which encode
tumor-specific, transplant, or autoimmune antigens or parts
thereof.
[0115] Examples of tumor specific antigens include prostate
specific antigen (Gattuso et al, Human Pathol., 26:123-126 (1995)),
TAG-72 and CEA (Guadagni et al, Int. J. Biol. Markers, 9: 53-60
(1994)), MAGE-1 and yrosinase (Coulie et al, J. Immnunothera.,
14:104-109 (1993)). Recently it has been shown in mice that
immunization with non-malignant cells expressing a tumor antigen
provides a vaccine effect, and also helps the animal mount an
immune response to clear malignant tumor cells displaying the same
antigen (Koeppen et al, Anal. N.Y. Acad. Sci., 690:244-255
(1993)).
[0116] Examples of transplant antigens include the CD3 receptor on
T cells (Alegre et al, Digest. Dis. Sci., 40:58-64 (1995)).
Treatment with an antibody to CD3 receptor has been shown to
rapidly clear circulating T cells and reverse most rejection
episodes (Alegre et al, supra).
[0117] Examples of autoimmune antigens include IAS .beta. chain
(Topham et al, Proc. Natl. Acad. Sci., USA, 91:8005-8009 (1994)).
Vaccination of mice with an 18 amino acid peptide from IAS a chain
has been demonstrated to provide protection and treatment to mice
with experimental autoimmune encephalomyelitis (Topham et al,
supra).
[0118] Alternatively, in the present invention, live invasive
bacteria can deliver eukaryotic expression cassettes encoding
immunoregulatory molecules. These immunoregulatory molecules
include, but are not limited to, growth factors, such as M-CSF,
GM-CSF; and cytokines, such as IL-2, IL-4, IL-5, IL-6, IL-10, IL-12
or IFN-.gamma.. Recently, delivery of cytokines expression
cassettes to tumor tissue has been shown to stimulate potent
systemic immunity and enhanced tumor antigen presentation without
producing a systemic cytokine toxicity (Golumbek et al, Canc. Res.,
53:5841-5844 (1993); Golumbek et al, Immun. Res., 12:183-192
(1993); Pardoll, Curr. Opin. Oncol., 4:1124-1129 (1992); and
Pardoll, Curr. Opin. Immunol., 4:619-623 (1992)).
[0119] The antisense RNA and catalytic RNA species delivered to
animal cells can be targeted against any molecule present within
the recipient cell or likely to be present within the recipient
cell. These include but are not limited to RNA species encoding
cell regulatory molecules, such as interlukin-6 (Mahieu et al,
Blood, 84:3758-3765 (1994)), oncogenes such as ras (Kashani-Sabet
et al, Antisen. Res. Devel., 2:3-15 (1992)), causitive agents of
cancer such as human papillomavirus (Steele et al, Canc. Res.,
52:4706-4711 (1992)), enzymes, viral RNA's and pathogen derived
RNA's such as HIV-1 (Meyer et al, Gene, 129:263-268 (1993);
Chatterjee et al, Sci., 258:1485-1488 (1992); and Yamada et al,
Virol., 205:121-126 (1994)). The RNAs can also be targeted at
non-transcribed DNA sequences, such as promoter or enhancer
regions, or to any other molecule present in the recipient cells,
such as but not limited to, enzymes involved in DNA synthesis or
tRNA molecules (Scanlon et al, Proc. Natl. Acad. Sci. USA,
88:10591-10595 (1991); and Baier et al, Mol. Immunol., 31:923-932
(1994)).
[0120] In the present invention, live invasive bacteria can also
deliver eukaryotic expression cassettes encoding proteins to animal
tissue from which they can later be harvested or purified. An
example is the delivery of a eukaryotic expression cassette under
the control of a mammary specific viral promoter, such as derived
from mouse mammary tumor virus (ATCC No. VR731), encoding
.alpha..sub.1-antitrypsin to mammary tissue of a goat or sheep.
[0121] Alternatively an invasive bacteria carrying a eukaryotic
expression cassette can be introduced to a tissue site such that it
would not spread from such a site. This could be accomplished by
any of several methods including delivery of a very limited dose,
delivery of a severely attenuated auxotrophic strain, such as an
asd mutant (Curtiss et al, supra) that will be rapidly inactivated
or die, or delivery of a bacterial strain that contains attenuating
lesions, such as a suicide systems (Rennell et al, supra; and
Reader et al, supra) under the control of a strong promoter, such
as the anerobic nirB promoter (Harborne et al, supra) which will be
switched on within the recipient host tissue. Additionally, through
use of different species and/or serotypes multiple doses of
invasive bacteria, the eukaryotic expression cassette of interest
can be given to an animal so as to manipulate expression levels or
product type. This approach obviates the need for specially raised
transgenic animals containing tissue specific promoters and having
tight control of expression, as is currently the case (Janne et al,
Int. J. Biochem., 26:859-870 (1994); Mullins et al, Hyperten.,
22:630-633 (1993); and Persuy et al, Eur. J. Bichem., 205:887-893
(1992)).
[0122] As a further alternative, single or multiple eukaryotic
expression cassettes encoding tumor-specific, transplant, and/or
autoimmune antigens, can be delivered in any single or multiple
combination with eukaryotic expression cassettes encoding
immunoregulatory molecules or other proteins.
[0123] Yet a further alternative approach is to deliver prokaryotic
expression cassettes in combination with eukaryotic expression
cassettes.
[0124] The invasive bacteria containing the eukaryotic expression
cassette can be used to infect animal cells that are cultured in
vitro. The animal cells can be further cultured in vitro, and the
cells carrying the desired genetic trait can be enriched by
selection for or against any selectable marker introduced to the
recipient cell at the time of bactofection. Such markers may
include antibiotic resistance genes, e.g., hygromycin, or neomycin,
selectable cell surface markers, or any other phenotypic or
genotypic element introduced or altered by bactofection. These in
vitro-infected cells or the in vitro-enriched cells can then be
introduced into animals intravenously, intramuscularly,
intradermally, or intraperitoneally, or by any inoculation route
that allows the cells to enter the host tissue.
[0125] Alternatively, the invasive bacteria containing the
eukaryotic expression cassettes can be introduced to infect the
animal by intravenous, intramuscular, intradermal,
intraperitoneally, peroral, intranasal, intraocular, intrarectal,
intravaginal, oral, immersion and intraurethral inoculation
routes.
[0126] The amount of the live invasive bacteria of the present
invention to be administered will vary depending on the species of
the subject, as well as the disease or condition that is being
treated. Generally, the dosage employed will be about 10.sup.3 to
10.sup.11 viable organisms, preferably about 10.sup.5 to 10.sup.9
viable organisms. Alternatively, when bactofecting individual
cells, the dosage of viable organisms to administered will be at a
multiplicity of infection ranging from about 0.1 to 10.sup.6,
preferably about 10.sup.2 to 10.sup.4.
[0127] The invasive bacteria of the present invention are generally
administered along with a pharmaceutically acceptable carrier or
diluent.
[0128] The particular pharmaceutically acceptable carrier or
diluent employed is not critical to the present invention. Examples
of diluents include a phosphate buffered saline, buffer for
buffering against gastric acid in the stomach, such as citrate
buffer (pH 7.0) containing sucrose, bicarbonate buffer (pH 7.0)
alone (Levine et al, J. Clin. Invest., 79:888-902 (1987); and Black
et al J. Infect. Dis., 155:1260-1265 (1987)), or bicarbonate buffer
(pH 7.0) containing ascorbic acid, lactose, and optionally
aspartame (Levine et al, Lancet, 11:467-470 (1988)). Examples of
carriers include proteins, e.g., as found in skim milk, sugars,
e.g., sucrose, or polyvinylpyrrolidone. Typically these carriers
would be used at a concentration of about 0.1-90% (w/v) but
preferably at a range of 1-10% (w/v).
[0129] The following examples are provided for illustrative
purposes only, and are in no way intended to limit the scope of the
present invention.
EXAMPLE 1
Bactofection Requires A Eukaryotic Expression Cassette
[0130] The following experiment was carried out to demonstrate that
infection with invasive bacteria is able to introduce a foreign
gene into animal cells, which is then expressed by the animal cells
(hereinafter "bactofection").
[0131] A. The Eukaryotic Expression Cassette
[0132] An attenuated Shigella flexneri strain containing both
.DELTA.aroA and .DELTA.virG attenuating lesions (Noriega et al,
supra) was transformed with either pSV.beta.-gal (Promega
Corporation, Madison, Wis.), which contains the reporter gene
.beta.-galactosidase (.beta.-gal) (hereinafter "p.beta.-gal+SV"),
or a derivative thereof which lacks the viral derived SV40
eukaryotic promoter region (hereinafter "p.beta.-gal-SV"), as
described by Promega Corp. (TB094, Promega Corpe). Both constructs
also contain the prokaryotic Escherichia coli gpt promoter which
enables expression of .beta.-gal by S. flexneri.
[0133] p.beta.-gal-SV was obtained by removing the SV40 promoter
from p.beta.-gal+SV by HindIII and NcoI restriction endonuclease
digestion, filling in the DNA overhangs, and then carrying out
religation using standard molecular biology techniques (Sambrook et
al, supra). The deletion of the SV40 promoter region was confirmed
by restriction digest analysis.
[0134] Thus, p.beta.-gal+SV contains a functional eukaryotic
expression cassette, whereas p.beta.-gal-SV only contains a
functional prokaryotic promoter.
[0135] The resulting transformed bacteria were seeded from 30%
(w/v) glycerol stocks, maintained at -70.degree. C., onto solid
medium (Tryptic Soy Agar, DIFCO, Madison, Wis.) containing 100
.mu.g/ml of ampicillin, to select for bacteria containing the
plasmids, and grown overnight at 37.degree. C.
[0136] B. The Eukaryotic Cells
[0137] HeLa cells (ATCC No. CCL-2) were grown on plastic tissue
culture plates at 37.degree. C. in 5% (v/v) CO.sub.2 in RPMI medium
supplemented with 10% (v/v) fetal bovine serum, 2.0 mM L-glutamine,
1.0 mM L-pyruvate, 50 U/ml penicillin and 50 .mu.g/ml streptomycin
(hereinafter "RPMI/FBS"). 24 to 48 hours prior to bactofection, the
HeLa cells were trypsinized with 0.25% (w/v) trypsin containing 1.0
mM EDTA, and split by limiting dilution such that they were 40-60%
confluent at the time of the experiment.
[0138] Prior to bactofection, the number of HeLa cells present was
ascertained by counting in a hemocytometer (Celis, Cell Biology: A
Laboratory Manual, Ed. Academic Press, San Diego, Calif.
(1994)).
[0139] C. Bactofection of the Eukaryotic Cells
[0140] 5.times.10.sup.4 HeLa cells were washed once with RPMI media
lacking fetal bovine serum and penicillin/streptomycin (hereinafter
"SFM"), then overlaid with a bacterial suspension in SFM, and
incubated at 37.degree. C. in 5% CO.sub.2. The bacterial suspension
was either off the overnight agar plates or from a fresh broth
culture, and was prepared to give an infection ratio of
approximately 10.sup.1 to 10.sup.3 viable transformed bacteria to 1
HeLa cell.
[0141] After 3 hours, the SFM containing the extra-cellular
bacteria was removed, the HeLa cells rinsed once with RPMI/FBS, and
then fresh RPMI/FBS containing 100 .mu.g/ml gentamicin was added.
Following a further 1 hour incubation at 37.degree. C. in 5%
CO.sub.2, the gentamicin solution was removed, the HeLa cells
rinsed once with RPMI/FBS, fresh RPMI/FBS was added and the cells
were returned to 37.degree. C. in 5% CO.sub.2.
[0142] At 6 hours, 24 hours, 48 hours, 72 hours and 92 hours
post-bactofection, the HeLa cells were washed twice with phosphate
buffered saline (hereinafter "PBS"), stained for .beta.-gal
activity as described by Hawley-Nelson et al, Focus, 15:73-79
(1993), and then photographed. When the incubation time prior to
analysis was greater than 48 hours, then the RPMI/FBS was changed
at 48 hours.
[0143] Cells in which the cytoplasm had stained evenly blue were
only observed for HeLa cells bactofected with S. flexneri
containing p.beta.-gal+Sv, and not for HeLa cells bactofected with
S. flexneri containing p.beta.-gal-SV. The average extent of
confluent staining was greater the longer the period between
bactofection and photography, which indicates that expression was
not due solely to .beta.-gal synthesized by the Shigella prior to
bactofection, but was a result of newly synthesized .beta.-gal
within the HeLa cell. This was confirmed by the p.beta.-gal-SV
bactofected cells in which there was no increase in the extent of
staining in relation to time.
[0144] The ratio of positive .beta.-gal stained bactofected
transformed HeLa cells, defined as those in which greater than 25%
of the cytoplasm stained blue (hereafter "transfected"), to
non-transformed, but bacterial associated HeLa cells, defined as
those with blue stained inter-cytosolic bacteria (a result of S.
flexneri expression of .beta.-gal off of the E. coli gpt promoter)
and/or less than or equal to 25% of the cytoplasm stained blue
(hereafter "untransfected"), was determined by counting 500 cells
in each of 3 wells. In both sets of bactofected cells, a small
number (.ltoreq.5 per well) of HeLa cells were hyperinfected with
S. flexneri. These hyperinfected cells were distinguishable by
their `patchy` appearance and non-uniform coloration, due to the
individual blue stained bacteria which were visible by microscopy.
These hyperinfected cells were not counted as having >25% blue
staining. The results are shown in Table 1 below. TABLE-US-00001
TABLE 1 Time p.beta.-gal + SV p.beta.-gal - SV (h) untransfected
transfected untransfected transfected 6 198.33 .+-. 40.10 22.00
.+-. 2.65 161.00 .+-. 44.64 0 24 136.00 .+-. 17.09 69.67 .+-. 16.62
168.33 .+-. 17.93 0 48 121.00 .+-. 39.59 102.00 .+-. 8.66 188.00
.+-. 12.00 0 72 74.67 .+-. 44.52 46.00 .+-. 22.65 96.00 .+-. 15.10
0 92 75.00 .+-. 19.97 39.67 .+-. 15.96 131.33 .+-. 21.01 0
[0145] As shown in Table 1 above, only HeLa cells bactofected with
the eukaryotic SV40 promoter containing .beta.-gal construct
(p.beta.-gal+SV) resulted in a transformed phenotype. This
indicates that the blue .beta.-gal phenotype was not due to
prokaryotically expressed .beta.-gal, but rather was due to nascent
synthesis by the bactofected HeLa cells.
[0146] The survival of the attenuated S. flexneri inside of the
HeLa cells was determined by counting viable bacteria present in
each of 3 wells at 6 hours, 24 hours, 48 hours, 72 hours and 92
hours, post-bactofection by standard methods (Celis, Cell Biology:
A Laboratory Manual, Ed, Academic Press, San Diego Calif. (1994)),
i.e., the post-bactofected HeLa cells were lysed with 1.0% (w/v)
deoxycholic acid and viable bacteria enumerated on solid media. The
results are shown in FIG. 1A for HeLa cells bactofected with S.
flexneri::p.beta.-gal+SV, and in FIG. 1B, for HeLa cells
bactofected with S. flexneri::p.beta.-gal-SV.
[0147] As shown in FIGS. 1A and 1B, the S. flexneri were rapidly
inactivated inside the HeLa cells. This further demonstrates that
the increase in .beta.-gal phenotype is due to new enzyme
synthesis. That is, plasmids used in this example are derived from
pSV.beta.-gal and lack a eukaryotic origin of replication. As such
they are not replicating inside the recipient HeLa cells.
Therefore, the partitioning of the plasmid is not regulated and new
daughter cells will not contain sufficient plasmid to develop a
permanently transformed phenotype.
[0148] To confirm that bactofection was not killing the HeLa cells,
control bactofected HeLa cells (using S. flexneri::p.beta.-gal+SV)
were counted at regular intervals methods, in a hemocytometer after
trypsin treatment as described by Celis, supra. The results,
average of 2 wells per time point, are shown in FIG. 2.
[0149] As shown in FIG. 2 the HeLa cell number continued to
increase throughout the experiment, indicating that the process of
bactofection can be accomplished without significant cellular
cytotoxicity against the host cell.
EXAMPLE 2
Bactofection In Various Cell Types
[0150] To ascertain the ability of bactofection to transform cell
lines other than the epithelial like human cervical HeLa cells, two
additional epithelial like cell lines and one kidney cell line were
subjected to bactofection.
[0151] More specifically, Int 407 (ATCC No. CCL-6), a human fetal
ileum/jejunal cell line; CaCo-2 (ATCC No. HTB-37), a human colonic
cell line; and MDCK (ATCC No. CCL-34), a canine kidney cell line
were cultured and infected with S. flexneri containing either
p.beta.-gal+SV or p.beta.-gal-SV, and evaluated for .beta.-gal
activity 24 hours post-bactofection as described in Example 1 above
for the HeLa cells.
[0152] Using p.beta.-gal+SV, transformed .beta.-gal positive
stained cells were obtained for the Int 407 and CaCo-2 cells, but,
as expected, not for the MDCK cells. That is, bactofection appears
to mirror the natural invasion characteristics seen by wild-type
Shigella sp., as such Shigella very rarely causes infection in
dogs, and normally is only found in epithelial cells (Kreig et al,
supra).
[0153] Thus, it is evident that the method of the present invention
is not restricted to one animal cell type, but is applicable to
animal cells derived from various tissues.
EXAMPLE 3
Bactofection-Mediated Expression of Various Foreign Antigens
[0154] The following experiment was carried out to demonstrate that
bactofection is able to mediate expression of various foreign
antigens in HeLa cells, as well as in human peripheral blood
derived mononuclear cells.
[0155] A. The Eukaryotic Expression Cassette
[0156] The S. flexneri .DELTA.aro.DELTA.virG strain was transformed
with the commercial eukaryotic reporter plasmid pGFP-C1
(Stratagene, La Jolla, Calif.). This plasmid contains a viral
derived CMV eukaryotic promoter driving the expression of a gene
encoding the Aequorea victoria jellyfish green fluorescent protein
(GFP) (Wang et al, Nature, 369:400-403 (1994)). Plasmid pGFP-C1
does not contain a prokaryotic promoter in the correct location to
express GFP in the prokaryotic host, i.e., the GFP gene is not
located in a functional prokaryotic expression cassette. Only when
the plasmid is delivered into eukaryotic cells is GFP produced from
its eukaryotic expression cassette.
[0157] In addition, a eukaryotic expression cassette was
constructed which contains the gp160 region of HIV-1 on the stable
episomal eukaryotic plasmid pCEP4 (Invitrogen Corporation, San
Diego, Calif.). The plasmid was made by cloning a 3.5 kb PCR
amplified XbaI::NotI fragment spanning from exon 1 of tat to the
last exon of rev amplified from the HIV-1 molecular clone pBH10
(Ratner et al, supra). This plasmid was designated plasmid
pCEP4::gp160. Due to the design of the host plasmid, pCEP4, the
cloned gp160 sequence is only expressed inside eukaryotic cells,
i.e., it is present in a eukaryotic expression cassette, not a
prokaryotic expression cassette.
[0158] B. The Eukaryotic Cells
[0159] The HeLa cells were obtained and prepared as described in
Example 1 above, except that they were grown on glass coverslips
for 24 hours prior bactofection.
[0160] Mononuclear cells were enriched for macrophages by culturing
in RPMI medium supplemented with 10% (v/v) human serum in teflon
beakers for 5 days prior to adhering to glass coverslips, for 24
hours, before bactofection.
[0161] C. Bactofection of the Eukaryotic Cells
[0162] Both the HeLa cells and macrophages were bactofected with
the S. flexneri .DELTA.aro.DELTA.virG strain transformed with
pGFP-C1, as described in Example 1 above. 48 hours
post-bactofection, the presence of GFP synthesized by the
bactofected transformed animal cells was visualized for green
fluorescence by fluorescent microscopy. Both HeLa cells and
macrophages resulted in two populations, those cells that were
bactofected, and therefore fluorescent due to expressed GFP, and
those cells that had not been bactofected, and were thereby
non-fluorescent. The ratio of bactofected HeLa cells to
non-bactofected HeLa cells was visibly similar to that seen with
p.beta.-gal+SV, while it appeared that less macrophages had been
bactofected.
[0163] In addition, HeLa cells grown on glass coverslips were
bactofected, as described in Example 1 above, using Shigella
.DELTA.aro.DELTA.virG transformed with either the pCEP4::gp160 or
pCEP4. 48 and 72 hours post-bactofection, the coverslips were
removed from the RPMI/FBS, rinsed twice with PBS, and then fixed
for more than 2 hours in methanol at -20.degree. C. Following
fixing, gp160 protein was detected by immunofluorescence using an
anti-gp160 monoclonal antibody cocktail (Abacioglu et al, AIDS Res.
and Human Retroviruses, 10(4):371-381 (1994)), and a FITC-labeled
detector antibody as described by Harlow et al, Antibodies, Cold
Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1988).
When visualized by fluorescent microscopy, two cell populations
were visible, i.e., both positive staining bactofected transformed
gp160 expressing cells and non-transformed cells. The ratio of
bactofected HeLa cells to non-bactofected HeLa cells was visibly
similar to that seen with p.beta.-gal+SV. However, due to the
overexpression of gp160, transformed cells appeared deformed and
were essentially unstable for long periods of time.
EXAMPLE 4
Bactofection with Other Attenuating Lesions
[0164] In order to demonstrate that the .DELTA.aro.DELTA.virG
attenuation in the S. flexneri strain employed in Example 1 is not
essential for bactofection, a second S. flexneri strain carrying a
.DELTA.asd attenuation was transformed with the p.beta.-gal+SV and
p.beta.-gal-SV plasmids, and used in bactofection experiments of
various cell types as described in Example 1.
[0165] The .DELTA.asd attenuation (EC 1.2.1.11) stops production of
peptidoglycans necessary for cell wall synthesis in prokaryotes
(Cohen et al, In: Escherichia coli and Salmonella typhimurium:
Cellular and Molecular Biology, Vol. 10, pages 429-444, Ingraham et
al, Eds., American Society of Microbiology, Washington, D.C.
(1987)). In the absence of externally added
DL-.alpha.,.epsilon.-diaminopimelic acid (hereinafter "DAP") to the
growth media, the .DELTA.asd attenuated prokaryotic cells lyse.
This compound is not present inside eukaryotic cells.
[0166] The presence of the .DELTA.asd attenuation resulted in a
slightly decreased ability to invade HeLa, Int-407 and CaCo-2 cells
compared with the .DELTA.aro.DELTA.virG strain. This attenuated
strain was also found to be unable to invade MDCK cells. Addition
of DAP (50 .mu.g/ml) to the bacterial cell suspension during the 3
hour invasion incubation restored invasion levels to that seen with
the .DELTA.aro.DELTA.virG attenuated strain (see Table 2 below).
TABLE-US-00002 TABLE 2 p.beta.-gal + SV p.beta.-gal - SV +/-DAP
untransfected transfected untransfected transfected +DAP 135.67
.+-. 43.32 87.66 .+-. 11.06 71.67 .+-. 16.92 0 -DAP 45.33 .+-.
14.01 43.33 .+-. 13.20 9.00 .+-. 2.65 0
[0167] Table 2 above shows the number of HeLa cells displaying a
transformed phenotype 48 hours after bactofection by S. flexneri
.DELTA.asd transformants with or without added DAP. The cells were
stained overnight for .beta.-gal activity, and then 500 cells in
each of 3 wells were counted. Averages.+-.std. error are given.
Only HeLa cells bactofected with S. flexneri .DELTA.asd containing
p.beta.-gal+SV resulted in a blue .beta.-gal positive
phenotype.
[0168] Thus, the nature of the attenuation is not crucial for
bactofection to occur, but may influence the level of
transformation.
[0169] The survival of the attenuated S. flexneri .DELTA.asd (+DAP)
inside of the HeLa cells was determined by counting viable bacteria
present in each of 3 wells at 6 hours, 24 hours, 48 hours and 96
hours, post-bactofection as described in Example 1. The results are
shown in FIG. 3A for HeLa cells bactofected with S.
flexneri::p.beta.-gal+SV, and in FIG. 3B, for HeLa cells
bactofected with S. flexneri::p.beta.-gal-SV. As shown in FIGS. 3A
and 3B, the S. flexneri were not replicating inside the HeLa cells,
and therefore the increase in .beta.-gal phenotype must be due to
new enzyme synthesis.
[0170] To confirm that bactofection was not killing the HeLa cells,
control bactofected HeLa cells (using S. flexneri::p.beta.-gal+SV)
were counted as described in Example 1. The results, i.e., average
of 2 wells per time point, are shown in FIG. 4.
[0171] As shown in FIG. 4 the HeLa cell number continued to
increase throughout the experiment, indicating that the process of
bactofection was not cell cytotoxic.
EXAMPLE 5
Delivery of a Reporter Gene in Vivo to Animal Tissue
[0172] In order to demonstrate that bactofection can occur in vivo,
restrained mice (Balb/c) were intranasally inoculated with
5.times.10.sup.6 viable S. flexneri .DELTA.aro.DELTA.virG
containing either p.beta.-gal+SV or p.beta.-gal-SV in a volume of
10 .mu.l of PBS. 48 hours after inoculation, the mice were
sacrificed, lung tissue collected and frozen to -70.degree. C.
Cryosections (5.0 .mu.M) were prepared, fixed, and then stained
overnight for .beta.-gal activity as described above (Hawley-Nelson
et al, supra). Following staining, the sections were rinsed twice
with PBS, then sealed under coverslips.
[0173] Blue-staining .beta.-gal-positive cells were visible per
lung section infected with p.beta.-gal+SV, but not those infected
with p.beta.-gal-SV.
[0174] Thus, bactofection is not a phenomena limited to in vitro
applications, but is also suitable for in vivo use.
EXAMPLE 6
Bactofection Requires Both Viability and an Invasion phenotype
[0175] To determine if either viability or an active invasion
phenotype are required for bactofection to occur, HeLa cells were
bactofected using non-invasive (congo red negative) S. flexneri
.DELTA.aro.DELTA.virG::p.beta.-gal+SV and UV-killed invasive (congo
red positive) S. flexneri .DELTA.aro.DELTA.virG::p.beta.-gal+SV, as
described in Example 1. A duplicate culture, not UV-killed, of the
invasive (congo red positive) S. flexneri
.DELTA.aro.DELTA.virG::p.beta.-gal+SV was used as a control.
[0176] Neither the congo red negative nor the UV-killed bacteria
were able to attach to HeLa cells nor invade. In both cases, no
positive .beta.-gal stained transformed HeLa cells were detected
(see Table 3 below). Additional experiments using either viable
congo red positive S. flexneri .DELTA.asd::p.beta.-gal+SV (+DAP) or
UV-killed (+DAP) cells showed the same result (see Table 3 below).
TABLE-US-00003 TABLE 3 strains containing p.beta.-gal + SV
untransfected transfected S. flexneri .DELTA.aro.DELTA.virG;
CR.sup.+ 35.00 .+-. 6.56 66.67 .+-. 1.15 S. flexneri
.DELTA.aro.DELTA.virG; CR.sup.+, 1.67 .+-. 2.08 0 UV-killed S.
flexneri .DELTA.aro.DELTA.virG; CR.sup.- 6.00 .+-. 2.00 0 S.
flexneri .DELTA.asd; CR.sup.+ 135.67 .+-. 43.32 87.66 .+-. 11.06 S.
flexneri .DELTA.asd; CR.sup.+, UV-killed 2.33 .+-. 4.04 0
[0177] Table 3 above shows the number of HeLa cells displaying a
transformed phenotype 48 hours after bactofection by S. flexneri
strains containing the reporter plasmid p.beta.-gal+Sv. The cells
were stained overnight for .beta.-gal activity, and then 500 cells
in each of three wells counted. Averages.+-.std. error are given.
Only HeLa cells bactofected with invasive, viable S. flexneri
resulted in a blue .beta.-gal positive phenotype.
[0178] Therefore, the viability and the ability of the prokaryotic
cells used in bactofection to invade the eukaryotic target cell
appear to be essential for transformation of an animal cell by
bactofection.
EXAMPLE 7
Development of an Immune Response to an in Vivo Delivered Gene
[0179] In order to show another example of in vivo use of
bactofection, 5.times.10.sup.7 S. flexneri .DELTA.aro .DELTA.virG
containing the pCEP4::gp160 plasmid construct were administered
intranasally to restrained Balb/c mice. 14 days following
bactofection, the mice were sacrificed and spleens collected.
[0180] Proliferation assays on the spleenocytes were performed by
standard methods (Kruisbeck et al, In: Current Protocols in
Immunology, pages 3.12.1-3.12.4, Current Protocols, New York, N.Y.
(1991)) using gp120 (Intracel, Cambridge, Mass.) as a matched
antigen and ovalbumin (Sigma Chemical Co., St Louis, Mo.) as
control antigen.
[0181] Splenocytes isolated from mice bactofected with plasmid
pCEP4::gp160, containing the gene for HIV-1 gp160, showed a
seven-fold stimulation, while splenocytes from control (pCEP4)
bactofected mice showed no response.
[0182] Thus bactofection is a suitable system for delivery of genes
encoding antigens to which an immune response is mounted.
[0183] While the invention has been described in detail, and with
reference to specific embodiments thereof, it will be apparent to
one of ordinary skill in the art that various changes and
modifications can be made therein without departing from the spirit
and scope thereof.
* * * * *