U.S. patent application number 14/831480 was filed with the patent office on 2016-07-14 for engineered opsonin for pathogen detection and treatment.
The applicant listed for this patent is President And Fellows Of Harvard College. Invention is credited to Donald E. INGBER, Michael SUPER, Jeffrey Charles WAY.
Application Number | 20160200785 14/831480 |
Document ID | / |
Family ID | 44307537 |
Filed Date | 2016-07-14 |
United States Patent
Application |
20160200785 |
Kind Code |
A1 |
SUPER; Michael ; et
al. |
July 14, 2016 |
ENGINEERED OPSONIN FOR PATHOGEN DETECTION AND TREATMENT
Abstract
The present invention provides for engineered molecular opsonins
that may be used to bind biological pathogens or identify
subclasses or specific pathogen species for use in devices and
systems for treatment and diagnosis of patients with infectious
diseases, blood-borne infections or sepsis. An aspect of the
invention provides for mannose-binding lectin (MBL), which is an
abundant natural serum protein that is part of the innate immune
system. The ability of this protein lectin to bind to surface
molecules on virtually all classes of biopathogens (viruses,
bacteria, fungi, protozoans) make engineered forms of MBL extremely
useful in diagnosing and treating infectious diseases and
sepsis.
Inventors: |
SUPER; Michael; (Lexington,
MA) ; WAY; Jeffrey Charles; (Cambridge, MA) ;
INGBER; Donald E.; (Boston, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
President And Fellows Of Harvard College |
Cambridge |
MA |
US |
|
|
Family ID: |
44307537 |
Appl. No.: |
14/831480 |
Filed: |
August 20, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13574191 |
Oct 23, 2012 |
9150631 |
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PCT/US2011/021603 |
Jan 19, 2011 |
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14831480 |
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61296222 |
Jan 19, 2010 |
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Current U.S.
Class: |
435/7.2 |
Current CPC
Class: |
G01N 33/56961 20130101;
C07K 2317/66 20130101; C07K 2317/53 20130101; A61P 7/00 20180101;
A61P 31/04 20180101; A61P 43/00 20180101; G01N 2333/40 20130101;
A61P 31/00 20180101; C07K 17/00 20130101; C07K 14/4726 20130101;
C07K 2319/30 20130101; C07K 16/44 20130101 |
International
Class: |
C07K 14/47 20060101
C07K014/47; C07K 16/44 20060101 C07K016/44; C07K 17/00 20060101
C07K017/00; G01N 33/569 20060101 G01N033/569 |
Claims
1.-30. (canceled)
31. A recombinant opsonin comprising: a carbohydrate recognition
domain of mannose-binding lectin (MBL), wherein the carbohydrate
recognition domain binds to at least one carbohydrate that is
present on a surface of a microbe; and a peptide comprising a
portion of an immunoglobulin Fc that links to the carbohydrate
recognition domain, and wherein the recombinant opsonin excludes a
functional domain of MBL that binds to a mannan-binding lectin
associated serine protease (MASP), the functional domain being
present in cysteine-rich N terminal domain of MBL or collagen
segment of MBL.
32. The recombinant opsonin of claim 31, wherein said carbohydrate
recognition domain comprises the neck and lectin domains of
MBL.
33. The recombinant opsonin of claim 31, wherein N-terminus of the
recombinant opsonin comprises at least one cysteine residue that
allows chemical cross-linking to a surface of a solid
substrate.
34. The recombinant opsonin of claim 31, wherein the peptide
comprises a Glycine+Serine segment, or a Proline+Alanine+Serine
segment.
35. The recombinant opsonin of claim 31, wherein the portion of the
immunoglobulin Fc comprises a hinge or a CH2-CH3 interface.
36. The recombinant opsonin of claim 31, wherein the carbohydrate
recognition domain consists of (i) SEQ ID NO: 2, or (ii) amino acid
residues 31 (glycine) to 148 (isoleucine) of SEQ ID NO: 2.
37. The recombinant opsonin of claim 31, wherein the recombinant
opsonin comprises a lectin having amino acid residues 81 (proline)
to 228 (isoleucine) of MBL, fused to an Fc portion of human IgG
(Fc.gamma.) (SEQ ID NO: 3).
38. The recombinant opsonin of claim 31, wherein the peptide
comprising the portion of the immunoglobulin Fc comprises an amino
acid sequence of SEQ ID NO: 1.
39. The recombinant opsonin of claim 38, wherein the amino acid
sequence of the peptide is modified to exclude N-linked
glycosylation.
40. The recombinant opsonin of claim 39, wherein the amino acid
residue 82 in the SEQ ID NO: 1 is changed from asparagine (N) to
aspartic acid (D).
41. The recombinant opsonin of claim 31, wherein N-terminus of the
recombinant opsonin consists essentially of an amino acid sequence
of alanine-lysine-threonine (AKT).
42. The recombinant opsonin of claim 31, wherein the recombinant
opsonin is attached to a solid substrate.
43. The recombinant opsonin of claim 42, wherein N-terminus of the
recombinant opsonin is attached to the solid substrate.
44. The recombinant opsonin of claim 42, wherein the solid
substrate is a magnetic microbead.
45. The recombinant opsonin of claim 42, wherein the solid
substrate is selected from a group consisting of a magnetic
microbead, a paramagnetic microbead, a microporous membrane, a
hollow fiber, any other fluid filtration membrane, flow device, a
living cell, an extracellular matrix of a biological tissue or
organ, and a phagocyte.
46. The recombinant opsonin of claim 31, wherein the carbohydrate
recognition domain is linked to C-terminal of the peptide.
47. A method comprising: contacting a fluid with a recombinant
opsonin, the recombinant opsonin comprising a carbohydrate
recognition domain of mannose-binding lectin (MBL), wherein the
carbohydrate recognition domain binds to at least one carbohydrate
that is present on a surface of a microbe; and a peptide comprising
a portion of an immunoglobulin Fc that links to the carbohydrate
recognition domain, and wherein the recombinant opsonin excludes a
functional domain of MBL that binds to a mannan-binding lectin
associated serine protease (MASP), the functional domain being
present in cysteine-rich N terminal domain of MBL or collagen
segment of MBL.
48. The method of claim 47, wherein the recombinant opsonin is
conjugated to a magnetic particle prior to the contacting, and the
separating is achieved by applying magnetic force to the fluid
after the opsonin-binding microorganism has bound to the
recombinant opsonin.
49. The method of claim 47 wherein the fluid is a biological fluid
derived from a subject selected from the group consisting of blood,
cerebrospinal fluid, joint fluid, urine, semen, saliva, tears, and
fluids collected by needle, biopsy, or aspiration procedures; or is
a fluid derived from a water or a food sample.
50. The method of claim 49, wherein the subject is suffering from
infection or sepsis.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/296,222, filed Jan. 19, 2010, the contents of
which are incorporated fully herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to molecular immunology,
microbial pathogens, and systems for detecting and/or removing
pathogens in fluids, including bodily fluids such as blood. More
specifically, for example, the present invention provides for an
engineered molecular opsonin that may be used to bind biological
pathogens or identify subclasses or specific pathogen species for
use in devices and systems for treatment and diagnosis of patients
with infectious diseases, blood-borne infections, or sepsis.
BACKGROUND
[0003] In the U.S., sepsis is the second-leading cause of death in
non-coronary ICU patients, and the tenth-most-common cause of death
overall. Sepsis is a serious medical condition that is
characterized by a whole-body inflammatory state (called a systemic
inflammatory response syndrome) and the presence of a known or
suspected infection. Sepsis typically occurs during bacteremia,
viremia or fungemia, and may result from infections that are caused
by pathogens, such as Staphylococcus aureus, that are not typical
bloodborne pathogens. Bloodborne pathogens are microorganisms that
cause disease when transferred from an infected person to another
person through blood or other potentially infected body fluids. The
most common diseases include Hepatitis B, Human Immunodeficiency
Virus, malaria, Hepatitis C, and syphilis.
[0004] Unfortunately, systemic inflammatory response syndrome may
become life threatening before an infective agent has been
identified by blood culture. This immunological response causes
widespread activation of acute-phase proteins, affecting the
complement system and the coagulation pathways, which then cause
damage to both vasculature and organs. Various neuroendocrine
counter-regulatory systems are also activated, often compounding
the problem. Even with immediate and aggressive treatment, this can
progress to multiple organ dysfunction syndrome and eventually
death. Hence, there remains a need for improved techniques for
diagnosis and treatment of patients with infectious diseases,
blood-borne infections, sepsis, or systemic inflammatory response
syndrome.
SUMMARY
[0005] The present invention provides for an engineered molecular
opsonin that may be used to bind biological pathogens or identify
subclasses or specific pathogen species for use in devices and
systems for treatment and diagnosis of patients with infectious
diseases, blood-borne infections or sepsis; or in the
identification of water- or food-borne pathogens. An aspect of the
invention provides for mannose-binding lectin (MBL), which is an
abundant natural serum protein that is part of the innate immune
system. The ability of this protein lectin to bind to surface
molecules on virtually all classes of biopathogens (viruses,
bacteria, fungi, protozoans) make engineered forms of MBL extremely
useful in diagnosing and treating infectious diseases and
sepsis.
[0006] An embodiment of the present invention provides for a
recombinant opsonin comprising a carbohydrate recognition domain of
an opsonin, a substrate binding domain, and a flexible peptide
domain that links the recognition domain to the solid surface
binding domain. In aspects of the invention, the carbohydrate
recognition domain is a lectin or fragment of a lectin.
Alternatively, the carbohydrate recognition domain is a collectin
or ficollin, or a portion or fragment of these. In a particular
aspect, the carbohydrate recognition domain (CRD) comprises the
portion of MBL starting at the residue proline 81 at the N-terminal
end of the lectin portion of the engineered opsonin. In another
particular aspect, the carbohydrate recognition domain comprises
the portion of MBL starting at the residue glycine 111 at the
N-terminal end of the lectin portion for the engineered
opsonin.
[0007] In a particular aspect of the invention, the substrate
binding domain of the recombinant opsonin comprises one or more
cysteine residues that allow chemical cross-linking to a solid
substrate. The solid substrate may comprise a magnetic microbead
(which may be coated with protein A), a microporous membrane, a
hollow-fiber reactor, or any other blood filtration membrane or
flow device. In other aspects, the substrate can be the surface of
cells, such as immune cells (e.g., macrophages), the surfaces of
cells that line the tissues or organs of the immune system (e.g.,
lymph nodes or spleen), or the surface of the extracellular matrix
of tissues or organs of the immune system.
[0008] In another aspect of the invention, the flexible peptide
domain may comprise at least one Glycine+Serine segment and/or at
least one Proline+Alanine+Serine segment. In another aspect of the
present invention, the flexible linker is a Fc portion of
immunoglobulin, such as Fc.gamma.. Fusion of human IgG1 Fc to the
neck and CRD regions of MBL improves the expression and
purification and coupling to a substrate in an active form.
[0009] An embodiment of the invention provides for a method of
collecting an opsonin-binding microorganism from a fluid comprising
contacting the fluid with a recombinant opsonin conjugated to a
solid surface; wherein the recombinant opsonin consists of a
carbohydrate recognition domain of an opsonin, a solid substrate
binding domain, and a flexible peptide domain that links the
recognition domain to the solid surface binding domain; allowing
the opsonin-binding microorganism to bind to said recombinant
opsonin-solid surface conjugate; and separating said fluid from
said microorganism-bound recombinant opsonin-solid surface
conjugate. The fluid may be a biological fluid, such as blood,
obtained from a subject. The fluid may then be returned to the
subject.
[0010] Another embodiment of the invention provide a method of
treating a blood infection in a subject comprising administering a
recombinant opsonin to the blood of the subject, wherein the
recombinant opsonin consists of a carbohydrate recognition domain
of an opsonin, a substrate binding domain, and a flexible peptide
domain that links the recognition domain to the substrate binding
domain, wherein the carbohydrate recognition domain binds an
opsonin-binding microorganism, and wherein the substrate binding
domain binds with a cell, tissue or organ of the immune system;
allowing the recombinant opsonin to bind to the opsonin-binding
microorganism; and allowing the microorganism-bound recombinant
opsonin to bind with a cell, tissue or organ of the immune system
wherein the microorganism is killed. The subject may be an animal
or a human.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows a diagram of mannose-binding lectin (MBL)
engineered into sets of trimers (polymers) in an embodiment of the
present invention.
[0012] FIGS. 2A and 2B are diagrams of an embodiment of the present
invention in which an artificial protein (FIG. 2A) comprising a
sterically unhindered N-terminus (optionally with a cysteine at or
near the N-terminus), followed by a long, flexible peptide segment,
then an MBL lectin domain at the C-terminus, is crosslinked to a
solid substrate in the example device in FIG. 2B.
[0013] FIG. 3 shows a diagram of an embodiment of the invention,
Fc-MBL.81, both in cartoon and in model form based on the X ray
crystallography models of Fc and of the neck and carbohydrate
recognition domains (CRD) of MBL.
[0014] FIG. 4 is a scheme of a vector encoding Fc in an aspect of
the invention.
[0015] FIG. 5 shows the calcium-dependent binding of dynabead-MBL
to C. albicans in which calcium maintains binding and EDTA
destabilizes binding.
[0016] FIG. 6 shows the binding of MBL-magnetic beads to different
pathogens. Pathogens were bound by MBL-coated magnetic beads
(control: beads without MBL), washed, and eluted onto culture
plates.
[0017] FIG. 7 shows data from MBL-magnetic beads binding to
microorganisms and overnight culture assay. The pathogens were
bound by MBL-coated magnetic beads (control: beads without MBL),
washed, and eluted onto culture plates and incubated overnight.
[0018] FIG. 8 demonstrates high levels of FcMBL expression from
transient transfection. FIG. 8A is a western blot of a reduced gel
loaded with unpurified supernatant of 293 cells transfected with
pFUSEFc MBL.81 (and pFUSE Fc) probed with anti-hFc. FIG. 8B shows
Protein A-purified FcMBL.81.
[0019] FIG. 9 shows results of a depletion assay in which the
FcMBL.81 construct was as active as full-length MBL in binding C.
albicans.
DETAILED DESCRIPTION
[0020] It should be understood that this invention is not limited
to the particular methodology, protocols, and reagents, etc.,
described herein and as such may vary. The terminology used herein
is for the purpose of describing particular embodiments only, and
is not intended to limit the scope of the present invention, which
is defined solely by the claims.
[0021] As used herein and in the claims, the singular forms include
the plural reference and vice versa unless the context clearly
indicates otherwise. Other than in the operating examples, or where
otherwise indicated, all numbers expressing quantities of
ingredients or reaction conditions used herein should be understood
as modified in all instances by the term "about."
[0022] All patents and other publications identified are expressly
incorporated herein by reference for the purpose of describing and
disclosing, for example, the methodologies described in such
publications that might be used in connection with the present
invention. These publications are provided solely for their
disclosure prior to the filing date of the present application.
Nothing in this regard should be construed as an admission that the
inventors are not entitled to antedate such disclosure by virtue of
prior invention or for any other reason. All statements as to the
date or representation as to the contents of these documents is
based on the information available to the applicants and does not
constitute any admission as to the correctness of the dates or
contents of these documents.
[0023] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as those commonly understood to
one of ordinary skill in the art to which this invention pertains.
Although any known methods, devices, and materials may be used in
the practice or testing of the invention, the methods, devices, and
materials in this regard are described herein.
[0024] In the broadest sense, opsonins are proteins that bind to
the surface of a particle. In nature, opsonins act as binding
enhancers for the process of phagocytosis, for example, by coating
the negatively-charged molecules on a target pathogen's membrane.
The present invention provides for an engineered molecular opsonin,
such as mannose-binding lectin (MBL), that may be used to bind
biological pathogens or identify subclasses or specific pathogen
species for use in devices and systems for treatment and diagnosis
of patients with infectious diseases, blood-borne infections or
sepsis. Treatment may be carried out in vivo or ex vivo.
[0025] MBL is a serum lectin opsonin that binds to mannose,
N-acetylglucosamine (NAG)-containing carbohydrates, and various
other carbohydrates that are present on the surface of many
microbial pathogens. MBL (also called mannose- or mannan-binding
protein, MBP) is a polymeric protein assembled from three or more
32 kDa monomers. Each monomer has an N-terminal cysteine rich
region, a collagen-like gly-X-Y region, a neck region and a
carbohydrate recognition domain. The assembly of the higher
molecular weight (MW) polymers begins with formation of trimers of
the 32 kDa monomer; these trimers then self-assembly into higher MW
polymers of three to six sets of trimers. See FIG. 1.
[0026] MBL is a key component in opsonization of microbial
pathogens and in the activation of complement (via the lectin
pathway) and coagulation. Opsonization is the binding of proteins
to target cells and the targeting these cells for uptake and
destruction by phagocytic cells, such as macrophages and
neutrophils. This opsonization appears to be mediated by the small,
cysteine-rich N-terminal domain of MBL as well as C3b deposited on
the target cell surface by MBL-mediated lectin complement pathway
activation.
[0027] In the activation of complement via the lectin pathway, the
microbe and specialized proteins, i.e., MASP-1 (Mannan-binding
lectin Associated Serine Protease) (Matsushita & Fujita, 176 J.
Exp. Med. 1497 (1992)), and MASP-2 (Thiel et al., 386 Nat. 506
(1997)), interact with bound MBL and activate complement in the
absence of antibody. The higher molecular weight MBL complexes (5
to 6 repeats of the functional MBL trimer) are potent activators of
complement via this lectin pathway, in which MASP 2 appears to
activate complement, and MASP 1 activates coagulation. The smaller
complexes (three to four repeats of the MBL trimer unit) are the
most potent activators of coagulation. Krarup et al., 2 PLoS One
e623 (2007).
[0028] In certain human populations, there is a high allele
frequency of mutations in MBL in the collagen helix, at codons 52,
54, and 57. Garred et al., 7 Genes Immun. 85 (2006). These
mutations prevent the formation of the higher molecular weight MBL
forms and suppress complement activation. In these cases, MBL still
functions as an opsonin and stimulates coagulation, but without
activating complement. There is also some evidence for heterozygote
advantage with respect to sepsis, in that heterozygotes have the
best survival, homozygous "wild-type" second best, and homozygous
"mutant" have the worst survival. See Sprong et al., 49 Clin.
Infect Dis. 1380 (2009). In addition, homozygous mutant neonates
are particularly susceptible to infection before the acquired
immune system begins to function.
[0029] There has been much debate on the usefulness of MBL as a
recombinant therapeutic protein for treatment of infectious
diseases. Intact MBL has been used in Phase 1 and Phase 2 clinical
trials, both as a recombinant protein and when purified from human
blood donations. In fact, plasma-derived MBL has been used as a
therapeutic in Phase 1 and Phase II trials of MBL deficient,
pediatric patients with chemotherapy induced neutropenia. Frakking
et al., 45 Eur. J. Cancer 50 (2009). Commercial efforts to develop
MBL have foundered because of difficulties in both producing the
recombinant protein and establishing efficacy. As used herein,
treatment or treating a subject can refer to medical care provided
to manage, improve, or relieve disease, illness, or symptoms
thereof.
[0030] The present invention provides for engineered opsonins,
e.g., engineered MBL or MBL polymers, for use in devices and
systems for pathogen detection and clearance. FIG. 5 shows the
calcium-dependent binding of MBL-conjugated magnetic microbeads to
the yeast C. albicans. FIGS. 6 and 7 compare the MBL-magnetic bead
binding between several difference pathogens, including the gram
positive bacterium, S. aureus; gram negative bacteria, Klebsiella
and E. coli; and yeast, C. albicans. Recent work has demonstrated
the feasibility of using combined micromagnetic and microfluidic
techniques to clear living pathogens from flowing fluids, such as
biological fluids, such as blood. Xia et al., 8 Biomed. Dev.
Biomed. Microdev. 299 (2006); Yung et al., Lab on a Chip DOI:
10.1039/b816986a (2009). In these microdevices (magnetic microbeads
that are coated with molecules that bind specifically to surface
markers on pathogen cells), are allowed to bind to these cells in
whole human blood, and then are pulled free from blood flowing
through microfluidic channels using an applied magnetic field
gradient. See WO/2008/130618; WO/2007/044642.
[0031] Among other uses, these devices have great promise to
rapidly clear blood of septic patients of toxin-producing
pathogens, and hence greatly increase response to conventional
antibiotic therapies. The ability to rapidly (within minutes) bind,
detect and isolate living pathogens circulating in blood, or
present within other biological fluids, using a potentially
inexpensive and easy-to-use microdevice also circumvents the major
limitations of current pathogen detection and sensitivity testing
assays that require multiple days of microbial culture in hospital
or commercial laboratories.
[0032] Biological fluids that may by used in the present invention
include, for example, blood, cerebrospinal fluid, joint fluid,
urine, semen, saliva, tears, and fluids collected by insertion of a
needle. Additionally, fluids may be collected from food or water
samples for rapid, general contamination assays according to the
present invention: such fluid can be collected and analyzed for
natural microbial contamination or for possible "bio-terrorism"
contamination.
[0033] Further, the current effectiveness of these methods
harnesses prior knowledge of the specific pathogen that one desires
to clear from the blood, because a specific ligand for that
pathogen (e.g., specific antibody) is placed on the magnetic
microbeads prior to using the blood cleansing device. Thus, the
present invention bolsters the current approaches by providing
engineered generic binding molecules that function like biological
opsonins and bind to specific, many or all, types of microbial
pathogens as the application requires. In this regard, the present
invention has therapeutic applications.
[0034] Another need addressed herein is the development of
specialized pathogen class-specific opsonins that bind, for
example, all types of fungi or all gram negative bacteria or all or
specific gram positive bacteria or all viruses or all protozoans,
as this knowledge could quickly advise physicians in their choice
of anti-microbial therapies before complete characterization of
species type of antibiotic sensitivity is identified with
conventional methods that often take many days to complete.
[0035] In addition, with the use of genetic engineering, and
directed evolution and selection strategies, modified versions of
natural opsonins can be engineered, such as MBL, that bind to
pathogens in a species-specific manner. Finally, binding that is
specific for pathogen sensitivity to different antibiotics or
antimicrobial therapeutics can be accomplished using appropriate
selection strategies. Hence, this invention provides for
development of engineered opsonins that provide these high value
properties.
[0036] MBL is an excellent choice for use as a generic opsonin for
the purposes described herein; however, the intact molecule is not
typically used in the presence of whole blood because it has
multiple functional domains that promote blood coagulation that may
interfere with diagnostic and therapeutic microdevice function.
This characteristic of MBL can be separated from its pathogen
binding function as provided herein. More specifically, MBL
contains four parts, from N- to C-terminus: a small N-terminal
domain of essentially unknown function that may be involved in
macrophage binding and/or MASP binding; a collagen segment that may
also be involved in MASP binding and higher-order oligomerization;
an alpha-helical "neck" segment that is sufficient for
trimerization; and the CRD lectin domain at the C-terminus that
mediates direct pathogen binding. The lectin domain is useful for
the application at hand, and the other domains may be present or
deleted depending on the needs of the user, and can be determined
by routine testing. Additionally, the lectin activity is
calcium-dependent, so bound microbes could be released by a
chelating agent for diagnostic purposes.
[0037] One embodiment of an engineered configuration of MBL, useful
as a generic opsonin for diagnostic and therapeutic applications,
comprises the lectin domain of MBL. For example, Glycine 111 (as
defined in the Research Collaboratory for Structural Bioinformatics
(RCSB), Protein Data Bank structure file 1HUP) is a convenient
N-terminal point at which to begin the lectin portion of the
engineered opsonin. Because the binding of MBL to a given monomeric
sugar is weak, the MBL may be attached to the solid matrix in a
flexible manner so that the proteins on the surface can move and
adjust to the shape of the microbe. For example, a flexible
peptide, such as one or more Glycine+Serine segment or one or more
Proline+Alanine+Serine segment, or other peptide linker(s) known in
the art, may be placed at the MBL N-terminus, as in FIG. 2A,
because these segments tend to not form folded structures.
[0038] Another embodiment of an engineered configuration of MBL,
useful as a generic opsonin for diagnosis and therapeutic
applications, comprises the neck and lectin domains of MBL. Proline
81 (as defined, for example, in the Research Collaboratory for
Structural Bioinformatics, Protein Data Bank (RCSB PDB) structural
file 1HUP) is a convenient N-terminal point at which to begin the
lectin sequence for this engineered opsonin construct. This portion
of MBL is fused downstream (C-terminal) to Fc portion of human IgG
(Fc.gamma.). The Fc portion may include the CH2-CH3 interface of
the IgG Fc domain, which contains the binding sites for a number of
Fc receptors including Staphylococcal protein A. In use, the Fc
portion dimerizes and strengthens the avidity affinity of the
binding by MBL lectins to monomeric sugars. Additionally, when used
as a diagnostic reagent, the n-linked glycosylation of the
recombinant opsonin can be removed. For example, in Fc MBL.81 the
glycosylation can be removed by changing the amino acid at residue
297 from asparagine to aspartic acid (N297D) in the Kabat system of
numbering amino acids in antibodies, this corresponds to amino acid
82 in this particular Fc construct. Glycosylated Fc maintains the
correct orientation for Fc mediated antibody-dependent
cell-mediated cytotoxicity (ADCC) and complement-mediated
cytotoxicity (CDC).
[0039] The engineered Fc MBL opsonin could be used in the
activation of Fc receptor-mediated uptake of Fc MBL opsonized
Mycobacterium tuberculosis, bypassing mannose receptor mediated
uptake of M. tuberculosis. Recent publications (Kang et al., 202 J.
Exp. Med. 987 (2005)), suggest that lipoarabinomannan (ManLaM) on
the cells surface of M. tuberculosis engage macrophage mannose
receptor (MMR) during the phagocytic process. This directs M.
tuberculosis to its initial phagosomal niche and inhibits
phagosome-lysosome (P-L) fusion, thereby enhancing survival in
human macrophages. Interestingly, inhibition of P-L fusion did not
occur with entry via Fc.gamma. receptors. In one embodiment, uptake
by Fc receptor endocytosis routes the bacterium, e.g., M.
tuberculosis, to different intracellular vesicles.
[0040] The configuration of the engineered opsonin of the present
invention also aids attachment of the fusion protein to a
substrate, such as a solid surface of a magnetic microbead or a
microporous membrane, using a chemical cross-linker that is
specific for the amino group at the N-terminus, or to a free
cysteine residue that has been engineered to be near the N-terminus
of the protein, as in FIG. 2B. (Lysine is an alternative to
cysteine, optionally following removal of the rest of the lysine
residues in the protein).
[0041] In some embodiments, the substrate to which the opsonin
binds is a living cell or extracellular matrix of a tissue or
organ. For example, the substrate may be the surface of a cell,
tissue or organ associated with the immune response. For example,
the cell may be a phagocyte (macrophage, neutrophil, and dendritic
cell), mast cell, eosinophil, basophil, and/or natural killer cell.
The cell may be the cell of tissues or organs of the immune system,
such as spleen, lymph nodes, lymphatic vessels, tonsils, thymus,
bone marrow, Peyer's patches, connective tissues, mucous membranes,
the reticuloendothelial system, etc. The surface to which the
opsonin binds may also be the extracellular matrix of one or more
of these tissues or organs.
[0042] In some embodiments, the solid substrate may comprise
magnetic beads or other structured materials, which then pull
microbes out from fluids, including biological fluids such as
blood, and concentrate and collect the microbes, including living
microbes. This approach is advantageous because the beads can then
be examined for the presence of the microbe, or be used to transfer
the collected microbes to conventional pathogen culture and
sensitivity testing assays. In other words, the engineered opsonin
may be used in diagnostics as a means of collecting potential
pathogens for identification; not only in the diagnosis of disease,
but in the identification of water- or food-borne pathogens,
particulates or other contaminants. Alternatively, the solid
substrate may comprise a hollow-fiber reactor or any other blood
filtration membrane or flow device (e.g., a simple dialysis tube)
or other resins, fibers, or sheets to selective bind and sequester
the biological pathogens.
[0043] The magnetic beads can be of any shape, including but not
limited to spherical, rod, elliptical, cylindrical, disc, and the
like. In some embodiments, magnetic beads having a true spherical
shape and defined surface chemistry are used to minimize chemical
agglutination and non-specific binding. As used herein, the term
"magnetic beads" refers to a nano- or micro-scale particle that is
attracted or repelled by a magnetic field gradient or has a
non-zero magnetic susceptibility. The magnetic bead can be
paramagnetic or super-paramagnetic. In some embodiments, magnetic
beads are super-paramagnetic. Magnetic beads are also referred to
as magnetic particles herein. In some embodiments, magnetic beads
having a polymer shell are used to protect the pathogen from
exposure to iron. For example, polymer-coated magnetic beads can be
used to protect pathogens from exposure to iron.
[0044] The magnetic beads can range in size from 1 nm to 1 mm. For
example, magnetic beads are about 250 nm to about 250 .mu.m in
size. In some embodiments, magnetic bead is 0.1 .mu.m to 100 .mu.m
in size. In some embodiments, magnetic bead is 0.1 .mu.m to 50
.mu.m in size. In some embodiments, magnetic bead is 0.1 .mu.m to
10 .mu.m in size. In some embodiments, the magnetic bead is a
magnetic nano-particle or magnetic micro-particle. Magnetic
nanoparticles are a class of nanoparticle which can be manipulated
using magnetic field or magnetic field gradient. Such particles
commonly consist of magnetic elements such as iron, nickel and
cobalt and their chemical compounds. Magnetic nano-particles are
well-known and methods for their preparation have been described in
the art. See, e.g., U.S. Pat. Nos. 6,878,445; 5,543,158; 5,578,325;
6,676,729; 6,045,925; 7,462,446; and U.S. Patent Publications No.
2005/0025971; No. 2005/0200438; No. 2005/0201941; No. 2005/0271745;
No. 2006/0228551; No. 2006/0233712; No. 2007/01666232; and No.
2007/0264199.
[0045] Magnetic beads are easily and widely available commercially,
with or without functional groups capable of binding to affinity
molecules. Suitable magnetic beads are commercially available such
as from Dynal Inc. (Lake Success, N.Y.); PerSeptive Diagnostics,
Inc. (Cambridge, Mass.); Invitrogen Corp. (Carlsbad, Calif.);
Cortex Biochem Inc. (San Leandro, Calif.); and Bangs Laboratories
(Fishers, Ind.). In particular embodiments, magnetic particles are
MyOne.TM. Dynabeads.RTM. magnetic beads (Dynal Inc.).
[0046] The solid substrate can be fabricated from or coated with a
biocompatible material. As used herein, the term "biocompatible
material" refers to any material that does not deteriorate
appreciably and does not induce a significant immune response or
deleterious tissue reaction, e.g., toxic reaction or significant
irritation, over time when implanted into or placed adjacent to the
biological tissue of a subject, or induce blood clotting or
coagulation when it comes in contact with blood. Suitable
biocompatible materials include, for example, derivatives and
copolymers of a polyimides, poly(ethylene glycol), polyvinyl
alcohol, polyethyleneimine, and polyvinylamine, polyacrylates,
polyamides, polyesters, polycarbonates, and polystyrenes.
[0047] In some embodiments, the solid substrate is fabricated or
coated with a material selected from the group consisting of
polydimethylsiloxane, polyimide, polyethylene terephthalate,
polymethylmethacrylate, polyurethane, polyvinylchloride,
polystyrene polysulfone, polycarbonate, polymethylpentene,
polypropylene, a polyvinylidine fluoride, polysilicon,
polytetrafluoroethylene, polysulfone, acrylonitrile butadiene
styrene, polyacrylonitrile, polybutadiene, poly(butylene
terephthalate), poly(ether sulfone), poly(ether ether ketones),
poly(ethylene glycol), styrene-acrylonitrile resin,
poly(trimethylene terephthalate), polyvinyl butyral,
polyvinylidenedifluoride, poly(vinyl pyrrolidone), and any
combination thereof.
[0048] In an aspect of the invention, the recombinant opsonins
described herein can be conjugated with the solid substrate by
methods well known in the art for conjugating peptides with other
molecules. For example, Hermanson, BIOCONJUGATE TECHNIQUES (2nd
Ed., Academic Press (2008)) and Niemeyr, Bioconjugation Protocols:
Strategies & Methods, in METHODS IN MOLECULAR BIOLOGY (Humana
Press, 2004), provide a number of methods and techniques for
conjugating peptides to other molecules. de Graaf, et al., 20
Bioconjugate Chem. 1281 (2009), provides a review of site-specific
introduction of non-natural amino acids into peptides for
conjugation.
[0049] Alternatively, the surface of the solid substrate can be
functionalized to include binding molecules that bind selectively
with the recombinant opsonin. These binding molecules are also
referred to as affinity molecules herein. The binding molecule can
be bound covalently or non-covalently on the surface of the solid
substrate. As used herein, the term "binding molecule" or "affinity
molecule" refers to any molecule that is capable of specifically
binding a recombinant opsonin described herein. Representative
examples of affinity molecules include, but are not limited to,
antibodies, antigens, lectins, proteins, peptides, nucleic acids
(DNA, RNA, PNA and nucleic acids that are mixtures thereof or that
include nucleotide derivatives or analogs); receptor molecules,
such as the insulin receptor; ligands for receptors (e.g., insulin
for the insulin receptor); and biological, chemical or other
molecules that have affinity for another molecule, such as biotin
and avidin. The binding molecules need not comprise an entire
naturally occurring molecule but may consist of only a portion,
fragment or subunit of a naturally or non-naturally occurring
molecule, as for example the Fab fragment of an antibody. The
binding molecule may further comprise a marker that can be
detected.
[0050] The binding molecule can be conjugated to surface of the
solid substrate using any of a variety of methods known to those of
skill in the art. The binding molecule can be coupled or conjugated
to surface of the solid substrate covalently or non-covalently.
Covalent immobilization may be accomplished through, for example,
silane coupling. See, e.g., Weetall, 15 Adv. Mol. Cell Bio. 161
(2008); Weetall, 44 Meths. Enzymol. 134 (1976). The covalent
linkage between the binding molecule and the surface can also be
mediated by a linker. The non-covalent linkage between the affinity
molecule and the surface can be based on ionic interactions, van
der Waals interactions, dipole-dipole interactions, hydrogen bonds,
electrostatic interactions, and/or shape recognition
interactions.
[0051] As used herein, the term "linker" means a molecular moiety
that connects two parts of a composition. Peptide linkers may
affect folding of a given fusion protein, and may also react/bind
with other proteins, and these properties can be screened for by
known techniques. Example linkers, in addition to those described
herein, include is a string of histidine residues, e.g., His6;
sequences made up of Ala and Pro, varying the number of Ala-Pro
pairs to modulate the flexibility of the linker; and sequences made
up of charged amino acid residues e.g., mixing Glu and Lys.
Flexibility can be controlled by the types and numbers of residues
in the linker. See, e.g., Perham, 30 Biochem. 8501 (1991); Wriggers
et al., 80 Biopolymers 736 (2005). Chemical linkers may comprise a
direct bond or an atom such as oxygen or sulfur, a unit such as NH,
C(O), C(O)NH, SO, SO.sub.2, SO.sub.2NH, or a chain of atoms, such
as substituted or unsubstituted C.sub.1-C.sub.6 alkyl, substituted
or unsubstituted C.sub.2-C.sub.6 alkenyl, substituted or
unsubstituted C.sub.2-C.sub.6 alkynyl, substituted or unsubstituted
C.sub.6-C.sub.12 aryl, substituted or unsubstituted
C.sub.5-C.sub.12 heteroaryl, substituted or unsubstituted
C.sub.5-C.sub.12 heterocyclyl, substituted or unsubstituted
C.sub.3-C.sub.12 cycloalkyl, where one or more methylenes can be
interrupted or terminated by O, S, S(O), SO.sub.2, NH, or C(O).
[0052] Nucleic acid based binding molecules include aptamers. As
used herein, the term "aptamer" means a single-stranded, partially
single-stranded, partially double-stranded or double-stranded
nucleotide sequence capable of specifically recognizing a selected
non-oligonucleotide molecule or group of molecules by a mechanism
other than Watson-Crick base pairing or triplex formation. Aptamers
can include, without limitation, defined sequence segments and
sequences comprising nucleotides, ribonucleotides,
deoxyribonucleotides, nucleotide analogs, modified nucleotides and
nucleotides comprising backbone modifications, branchpoints and
nonnucleotide residues, groups or bridges. Methods for selecting
aptamers for binding to a molecule are widely known in the art and
easily accessible to one of ordinary skill in the art.
[0053] The recombinant opsonin can be conjugated with surface of
the solid substrate by an affinity binding pair. The term "affinity
binding pair" or "binding pair" refers to first and second
molecules that specifically bind to each other. One member of the
binding pair is conjugated with the solid substrate while the
second member is conjugated with the recombinant opsonin. As used
herein, the term "specific binding" refers to binding of the first
member of the binding pair to the second member of the binding pair
with greater affinity and specificity than to other molecules.
[0054] Exemplary binding pairs include any haptenic or antigenic
compound in combination with a corresponding antibody or binding
portion or fragment thereof (e.g., digoxigenin and
anti-digoxigenin; mouse immunoglobulin and goat antimouse
immunoglobulin) and nonimmunological binding pairs (e.g.,
biotin-avidin, biotin-streptavidin), hormone (e.g., thyroxine and
cortisol-hormone binding protein), receptor-receptor agonist,
receptor-receptor antagonist (e.g., acetylcholine
receptor-acetylcholine or an analog thereof), IgG-protein A,
lectin-carbohydrate, enzyme-enzyme cofactor, enzyme-enzyme
inhibitor, and complementary oligonucleotide pairs capable of
forming nucleic acid duplexes), and the like. The binding pair can
also include a first molecule that is negatively charged and a
second molecule that is positively charged.
[0055] One example of using binding pair conjugation is the
biotin-sandwich method. See, e.g., Davis et al., 103 PNAS 8155
(2006). The two molecules to be conjugated together are
biotinylated and then conjugated together using tetravalent
streptavidin as a linker. A peptide can be coupled to the 15-amino
acid sequence of an acceptor peptide for biotinylation (referred to
as AP; Chen et al., 2 Nat. Methods 99 (2005)). The acceptor peptide
sequence allows site-specific biotinylation by the E. coli enzyme
biotin ligase (BirA; Id.). A recombinant opsonin can be similarly
biotinylated for conjugation with a solid substrate. Many
commercial kits are also available for biotinylating proteins.
Another example for conjugation to a solid surface would be to use
PLP-mediated bioconjugation. See, e.g., Witus et al., 132 JACS
16812 (2010). In this example, an AKT sequence on the Fc N terminal
allows conjugation to the solid surface and orientation of the
lectin binding domain in the optimal orientation pointing away from
the solid surface.
[0056] It should be noted that the affinity of a single lectin
domain for a sugar is low, and binding is normally driven by
avidity and multivalency. In the case of the present devices, the
multimerization domains are deleted from the protein, and
multivalency of the protein is effectively produced by attachment
to a solid substrate (e.g., a bead) at high density, which density
can be varied to provide optimal functionality.
[0057] Further regarding the MBL, its binding characteristics can
be manipulated by directed evolution for altered binding
specificity. MBL may be modified so that it binds to a more limited
set of sugars or other molecular features, with the result that the
modified MBL will bind to a more limited set of microbes to provide
a capability for pathogen class identification (e.g., one of virus,
bacteria, fungi, or protozoan), subclass typing (e.g., gram
negative or gram positive bacteria) or specific species
determination. Numerous strategies are available in the art.
[0058] For example, a straightforward directed evolution strategy
visually examines an atomic structure of MBL complexed with a
sugar, and then mutates appropriate amino acids that make contact
in a sugar-specific manner, so that distinctive contacts are lost
or particular types of steric hindrance are created. The three
dimensional structure of rat MBL has been solved in a complex with
a high-mannose oligosaccharide and with N-acetylglucosamine, a
methylated fucose, and so on. His189Val and Ile207Val are examples
of substitutions that modifications alter specificity.
[0059] In another strategy of directed evolution, the protein is
subjected to random mutagenesis and the resulting proteins are
screened for desired qualities. This is a particularly useful
technology for affinity maturation of phage display antibodies,
where the antibody complementary determining regions (CDRs) are
mutated by saturation mutagenesis and successful variants of the
six CDRs are shuffled together to form the highest affinity
antibodies.
[0060] The directed evolution paradigm can be applied to MBL in
order to select MBL variants with specific binding to yeast,
gram-positive bacteria, gram-negative, coagulase negative, aerobic
bacteria, etc. For this to work, however, the pattern and nature of
the target sugars or related surface features on these target
organisms may have to differ between the classes or species.
[0061] MBL is known to bind strongly to mannose and
N-acetylglucosamine sugars on fungi, gram-positive, and
gram-negative bacteria. For example, MBL binds strongly to Candida
spp., Aspergillus fumigatus, Staphylococcus aureus, and .beta.
hemolytic group A streptococci. MBL has intermediate affinity to
Escherichia coli, Klebsiella spp., and Haemophilus influenzae type
b. MBL binds weakly to .beta. hemolytic group B streptococci,
Streptococcus pneumoniae, and Staphylococcus epidermidis. Neth et
al., 68 Infect. & Immun. 688 (2000). The capsular
polysaccharide of Neisseria meningitides serogroup B, H. influenzae
type b and Cryptococcus neoformans are thought to decrease MBL
binding, as does bacterial endotoxin. Id.; Van Emmerik et al., 97
Clin. Exp. Immunol. 411 (1994); Schelenz et al., 63 Infect. Immun.
3360 (1995).
[0062] Others have reported that MBL facilitates opsonophagocytosis
of yeasts but not of bacteria, despite MBL binding: MBL (Lectin)
pathway of complement was critical for the opsonophagocytosis of
yeast, but the classical complement pathway was critical for
opsonophagocytosis of bacteria. Brouwer et al., 180 J. Immunol.
4124 (2008). It was not reported that MBL bound to the bacterial
species tested, however, only that MBL binding did not promote
significant complement activation and opsonophagocytosis.
[0063] Derivatives of MBL with a particular specificity can be
isolated by the following approach, which is a standard phage
display strategy: First, express a set of MBL variants from a
phagemid vector; then bind this library to a target of interest
(e.g., E. coli) and perform one or two rounds of selection; and
then perform a round of negative selection against a related target
(e.g., Candida), taking those phagemids that fail to bind. These
cycles of positive and negative selection are then repeated until a
population of phages that generally bind to the target and do not
bind to the non-target is generated. This method may be applied to
any pair of microbial strains against which differential binding is
desired, such as bacteria that are resistant and sensitive to a
given antibiotic. This positive/negative enrichment strategy may
also be used with an antibody-phage display library, which is an
even more standard way to isolate such specific binders.
[0064] MBL belongs to the class of collectins in the C-type
(calcium-dependent) lectin superfamily, other members of which,
such as surfactant protein A, surfactant protein D, CL-L1 and
CL-P1, may be useful in the present invention. Other possible
opsonins include ficollins (Thiel et al., 1997), which also
activate the lectin pathway of complement and bind MASP proteins.
These proteins are related to MBL but have a different, more
limited specificity. In the context of the diagnostic device
described herein, one option is to simply use the lectin domain of
a ficollin that corresponds to the lectin domain of MBL described
above. Another approach is to use `shuffling` of segments or
individual amino acids between MBL and one or more Ficollins to
create hybrid molecules that may have hybrid specificities. The
directed evolution and selection approach described above also
could potentially be used to generate human antibody fragments or
peptides that provide the class, subclass and species specificity
described above.
[0065] The present invention may be defined in any of the following
numbered paragraphs:
[0066] 1. A recombinant opsonin comprising: a carbohydrate
recognition domain of an opsonin; a substrate binding domain; and a
peptide domain that links the recognition domain to the substrate
binding domain.
[0067] 2. The recombinant opsonin of paragraph 1, wherein said
carbohydrate recognition domain is a collectin or ficollin or
derived from a collectin or ficollin.
[0068] 3. The recombinant opsonin of paragraph 1, wherein said
carbohydrate recognition domain is a lectin or a portion or a
fragment of a lectin.
[0069] 4. The recombinant opsonin of paragraph 3, wherein said
lectin is mannose-binding lectin (MBL).
[0070] 5. The recombinant opsonin of paragraph 4, wherein the
lectin consists of amino acid residues 81 (proline) to 228
(isoleucine) of MBL (SEQ ID NO:2).
[0071] 6. The recombinant opsonin of any of the foregoing
paragraphs, wherein said substrate binding domain comprises at
least one cysteine residue that allows chemical cross-linking to a
solid substrate.
[0072] 7. The recombinant opsonin of any of the foregoing
paragraphs, wherein the flexible peptide comprises a Glycine+Serine
segment or a Proline+Alanine+Serine segment.
[0073] 8. The recombinant opsonin of the foregoing paragraphs,
where the flexible peptide comprises a portion of immunoglobulin
Fc.
[0074] 9. The recombinant opsonin of paragraph 8, wherein the Fc
portion includes the CH2-CH3 interface of the IgG Fc domain.
[0075] 10. The recombinant opsonin of any of the foregoing
paragraph, wherein the substrate is a magnetic microbead, a
paramagnetic microbead, a microporous membrane, a hollow-fiber
reactor, or any other fluid filtration membrane or flow device.
[0076] 11. The recombinant opsonin of any of the foregoing
paragraphs, wherein the substrate is a living cell or extracellular
matrix of a biological tissue or organ.
[0077] 12. The recombinant opsonin of paragraph 11, wherein the
substrate is a phagocyte.
[0078] 13. A method of collecting an opsonin-binding microorganism
from a fluid comprising contacting the fluid with a recombinant
opsonin conjugated to a solid surface; wherein the recombinant
opsonin consists of a carbohydrate recognition domain of an
opsonin, a solid substrate binding domain, and a flexible peptide
domain that links the recognition domain to the solid surface
binding domain; allowing the opsonin-binding microorganism to bind
to said recombinant opsonin-solid surface conjugate; and separating
said fluid from said microorganism-bound recombinant opsonin-solid
surface conjugate.
[0079] 14. The method of paragraph 13, wherein the solid surface is
a magnetic particle, and the separating is achieved by applying
magnetic force to the fluid after the opsonin-binding microorganism
has bound to the recombinant opsonin-solid surface conjugate.
[0080] 15. The method of paragraph 13, further comprising the step
of identifying the microorganism.
[0081] 16. The method of paragraph 13, wherein the fluid is a
biological fluid.
[0082] 17. The method of paragraph 16, wherein the biological fluid
is selected from the group consisting of blood, cerebrospinal
fluid, joint fluid, urine, semen, saliva, tears, and fluids
collected by needle, biopsy, or aspiration procedures.
[0083] 18. The method of paragraph 17, wherein the biological fluid
is blood.
[0084] 19. The method of paragraph 18, further comprising the step
of returning the blood to its source.
[0085] 20. The method of paragraph 19, wherein the source is a
subject.
[0086] 21. The method of paragraph 20, wherein the subject is
suffering from infection or sepsis.
[0087] 22. The method of paragraph 13, wherein the fluid is derived
from a water or a food sample.
[0088] 23. The use of the recombinant opsonin of any of paragraphs
1 to 10 in the identification of a pathogen.
[0089] 24. The use of the recombinant opsonin of any of paragraphs
1 to 10 in the diagnosis of disease.
[0090] 25. The use of the recombinant opsonin of any of paragraphs
1 to 10 in the identification of water or food contamination.
[0091] 26. The use of the recombinant opsonin of any of paragraphs
1 to 12 in the treatment of disease.
[0092] 27. The use of the recombinant opsonin as in paragraph 26,
further combined with additional treatment or therapy.
[0093] 28. A method of treating a blood infection in a subject
comprising administering a recombinant opsonin to the blood of the
subject, wherein the recombinant opsonin consists of a carbohydrate
recognition domain of an opsonin, a substrate binding domain, and a
flexible peptide domain that links the recognition domain to the
substrate binding domain, wherein the carbohydrate recognition
domain binds an opsonin-binding microorganism, and wherein the
substrate binding domain binds with a cell, tissue or organ of the
immune system; allowing the recombinant opsonin to bind to the
opsonin-binding microorganism; and allowing the microorganism-bound
recombinant opsonin to bind with a cell, tissue or organ of the
immune system wherein the microorganism is killed.
[0094] 29. The method of paragraph 28, wherein the subject is an
animal.
[0095] 30. The method of paragraph 28, wherein the subject is a
human.
Examples
Example 1
Construction and Expression of FcMBL.81
[0096] An embodiment of an engineered configuration of MBL, useful
as a generic opsonin for diagnosis and therapeutic applications,
was constructed using the "neck" and "lectin" domains of MBL.
Proline 81 (as defined in the Research Collaboratory for Structural
Bioinformatics, Protein Data Bank structural file 1HUP) was
selected as the N-terminal point at which to begin the lectin
sequence. This portion of the lectin molecule was fused downstream
(C-terminal) to Fc portion of human gamma 1 (Fc.gamma.). A diagram
of the engineered opsonin construct is shown in FIG. 3. A schematic
of the Fc portion of a clone is shown in FIG. 4. The amino acids
for this construct include the following residues:
Fc Protein Sequence:
TABLE-US-00001 [0097] (SEQ ID NO: 1) 001 epkssdktht cppcpapell
ggpsvflfpp kpkdtlmisr tpevtcvvvd vshedpevkf 061 nwyvdgvevh
naktkpreeq ynstyrvvsv ltvlhqdwln gkeykckvsn kalpapiekt 121
iskakgqpre pqvytlppsr deltknqvsl tclvkgfyps diavewesng qpennykttp
181 pvldsdgsff lyskltvdks rwqqgnvfsc svmhealhnh ytqkslslsp ga
MBL.81 Protein Sequence (this Includes the Coiled-Coil Neck Region
and the Carbohydrate Recognition Domains (CRD) of Human MBL):
TABLE-US-00002 (SEQ ID NO: 2) 81 pdgdsslaas erkalqtema rikkwltfsl
gkqvgnkffl tngeimtfek vkalcvkfqa 141 svatprnaae ngaiqnlike
eaflgitdek tegqfvdltg nrltytnwne gepnnagsde 201 dcvlllkngq
wndvpcstsh lavcefpi
Fc-MBL.81 Sequence:
TABLE-US-00003 [0098] (SEQ ID NO: 3) 001 epkssdktht cppcpapell
ggpsvflfpp kpkdtlmisr tpevtcvvvd vshedpevkf 061 nwyvdgvevh
naktkpreeq ynstyrvvsv ltvlhqdwln gkeykckvsn kalpapiekt 121
iskakgqpre pqvytlppsr deltknqvsl tclvkgfyps diavewesng qpennykttp
181 pvldsdgsff lyskltvdks rwqqgnvfsc svmhealhnh ytqkslslsp
gapdgdssla 241 aserkalqte marikkwltf slgkqvgnkf fltngeimtf
ekvkalcvkf qasvatprna 301 aengaiqnli keeaflgitd ektegqfvdl
tgnrltytnw negepnnags dedcvillkn 361 gqwndvpcst shlavcefpi
[0099] Thus, the FcMBL.81 construct consists of a lectin having
amino acid residues 81 (proline) to 228 (isoleucine) of MBL, fused
a portion of Fc.gamma.. In use, the Fc portion dimerizes and adds
avidity to the weak affinity of the binding by MBL lectins to
monomeric sugars. When Fc MBL.81 is designed for use as a
diagnostic reagent, the n-linked glycosylation can be removed by
changing the amino acid at 297 from asparagine to aspartic acid
(N297D), or amino acid 82 in the Fc construct. Glycosylated Fc is
maintains the correct orientation for Fc mediated ADCC and CDC.
Additionally, a cysteine residue can be cloned onto the engineered
opsonin to allow binding to a solid substrate via chemical
conjugation. The construction and expression of an engineered
opsonin, such as FcMBL, may be achieved by various techniques known
in the art, see, e.g., U.S. Pat. No. 5,541,087.
[0100] Expression of the construct in transiently transfected cells
is demonstrated in FIGS. 8A and 8B. The FcMBL.81 expressed about 35
mg/L.
Example 2
Comparison of Fc MBL.81 Construct with Full-Length MBL in Binding
Yeast
[0101] Approximately 5.5 million Candida albicans yeast cells were
inoculated with varying numbers of MBL beads coated with either
wild-type, full-length MBL (hexamers of trimers) or Fc MBL.81. As
depicted graphically in FIG. 9, 18 million wild-type, full-length
MBL or Fc MBL.81 beads bound all 5.5 million fungal cells. This
example demonstrates that Fc MBL.81 beads are as active as
wild-type, full-length MBL beads in binding to C albicans.
Sequence CWU 1
1
31232PRTHomo sapiens 1Glu Pro Lys Ser Ser Asp Lys Thr His Thr Cys
Pro Pro Cys Pro Ala 1 5 10 15 Pro Glu Leu Leu Gly Gly Pro Ser Val
Phe Leu Phe Pro Pro Lys Pro 20 25 30 Lys Asp Thr Leu Met Ile Ser
Arg Thr Pro Glu Val Thr Cys Val Val 35 40 45 Val Asp Val Ser His
Glu Asp Pro Glu Val Lys Phe Asn Trp Tyr Val 50 55 60 Asp Gly Val
Glu Val His Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln 65 70 75 80 Tyr
Asn Ser Thr Tyr Arg Val Val Ser Val Leu Thr Val Leu His Gln 85 90
95 Asp Trp Leu Asn Gly Lys Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala
100 105 110 Leu Pro Ala Pro Ile Glu Lys Thr Ile Ser Lys Ala Lys Gly
Gln Pro 115 120 125 Arg Glu Pro Gln Val Tyr Thr Leu Pro Pro Ser Arg
Asp Glu Leu Thr 130 135 140 Lys Asn Gln Val Ser Leu Thr Cys Leu Val
Lys Gly Phe Tyr Pro Ser 145 150 155 160 Asp Ile Ala Val Glu Trp Glu
Ser Asn Gly Gln Pro Glu Asn Asn Tyr 165 170 175 Lys Thr Thr Pro Pro
Val Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr 180 185 190 Ser Lys Leu
Thr Val Asp Lys Ser Arg Trp Gln Gln Gly Asn Val Phe 195 200 205 Ser
Cys Ser Val Met His Glu Ala Leu His Asn His Tyr Thr Gln Lys 210 215
220 Ser Leu Ser Leu Ser Pro Gly Ala 225 230 2148PRTHomo sapiens
2Pro Asp Gly Asp Ser Ser Leu Ala Ala Ser Glu Arg Lys Ala Leu Gln 1
5 10 15 Thr Glu Met Ala Arg Ile Lys Lys Trp Leu Thr Phe Ser Leu Gly
Lys 20 25 30 Gln Val Gly Asn Lys Phe Phe Leu Thr Asn Gly Glu Ile
Met Thr Phe 35 40 45 Glu Lys Val Lys Ala Leu Cys Val Lys Phe Gln
Ala Ser Val Ala Thr 50 55 60 Pro Arg Asn Ala Ala Glu Asn Gly Ala
Ile Gln Asn Leu Ile Lys Glu 65 70 75 80 Glu Ala Phe Leu Gly Ile Thr
Asp Glu Lys Thr Glu Gly Gln Phe Val 85 90 95 Asp Leu Thr Gly Asn
Arg Leu Thr Tyr Thr Asn Trp Asn Glu Gly Glu 100 105 110 Pro Asn Asn
Ala Gly Ser Asp Glu Asp Cys Val Leu Leu Leu Lys Asn 115 120 125 Gly
Gln Trp Asn Asp Val Pro Cys Ser Thr Ser His Leu Ala Val Cys 130 135
140 Glu Phe Pro Ile 145 3380PRTArtificialConstruct Fc-MBL.81 3Glu
Pro Lys Ser Ser Asp Lys Thr His Thr Cys Pro Pro Cys Pro Ala 1 5 10
15 Pro Glu Leu Leu Gly Gly Pro Ser Val Phe Leu Phe Pro Pro Lys Pro
20 25 30 Lys Asp Thr Leu Met Ile Ser Arg Thr Pro Glu Val Thr Cys
Val Val 35 40 45 Val Asp Val Ser His Glu Asp Pro Glu Val Lys Phe
Asn Trp Tyr Val 50 55 60 Asp Gly Val Glu Val His Asn Ala Lys Thr
Lys Pro Arg Glu Glu Gln 65 70 75 80 Tyr Asn Ser Thr Tyr Arg Val Val
Ser Val Leu Thr Val Leu His Gln 85 90 95 Asp Trp Leu Asn Gly Lys
Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala 100 105 110 Leu Pro Ala Pro
Ile Glu Lys Thr Ile Ser Lys Ala Lys Gly Gln Pro 115 120 125 Arg Glu
Pro Gln Val Tyr Thr Leu Pro Pro Ser Arg Asp Glu Leu Thr 130 135 140
Lys Asn Gln Val Ser Leu Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser 145
150 155 160 Asp Ile Ala Val Glu Trp Glu Ser Asn Gly Gln Pro Glu Asn
Asn Tyr 165 170 175 Lys Thr Thr Pro Pro Val Leu Asp Ser Asp Gly Ser
Phe Phe Leu Tyr 180 185 190 Ser Lys Leu Thr Val Asp Lys Ser Arg Trp
Gln Gln Gly Asn Val Phe 195 200 205 Ser Cys Ser Val Met His Glu Ala
Leu His Asn His Tyr Thr Gln Lys 210 215 220 Ser Leu Ser Leu Ser Pro
Gly Ala Pro Asp Gly Asp Ser Ser Leu Ala 225 230 235 240 Ala Ser Glu
Arg Lys Ala Leu Gln Thr Glu Met Ala Arg Ile Lys Lys 245 250 255 Trp
Leu Thr Phe Ser Leu Gly Lys Gln Val Gly Asn Lys Phe Phe Leu 260 265
270 Thr Asn Gly Glu Ile Met Thr Phe Glu Lys Val Lys Ala Leu Cys Val
275 280 285 Lys Phe Gln Ala Ser Val Ala Thr Pro Arg Asn Ala Ala Glu
Asn Gly 290 295 300 Ala Ile Gln Asn Leu Ile Lys Glu Glu Ala Phe Leu
Gly Ile Thr Asp 305 310 315 320 Glu Lys Thr Glu Gly Gln Phe Val Asp
Leu Thr Gly Asn Arg Leu Thr 325 330 335 Tyr Thr Asn Trp Asn Glu Gly
Glu Pro Asn Asn Ala Gly Ser Asp Glu 340 345 350 Asp Cys Val Leu Leu
Leu Lys Asn Gly Gln Trp Asn Asp Val Pro Cys 355 360 365 Ser Thr Ser
His Leu Ala Val Cys Glu Phe Pro Ile 370 375 380
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