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Chen G, Koellhoffer JF, Zak SE, Frei JC, Liu N, Long H, Ye W, Nagar K, Pan G, Chandran K, Dye JM, Sidhu SS, Lai JR. Synthetic antibodies with a human framework that protect mice from lethal Sudan ebolavirus challenge. ACS Chem Biol 2014; 9:2263-73. [PMID: 25140871 PMCID: PMC4201348 DOI: 10.1021/cb5006454] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
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The ebolaviruses cause severe and
rapidly progressing hemorrhagic
fever. There are five ebolavirus species; although much is known about
Zaire ebolavirus (EBOV) and its neutralization by antibodies, little
is known about Sudan ebolavirus (SUDV), which is emerging with increasing
frequency. Here we describe monoclonal antibodies containing a human
framework that potently inhibit infection by SUDV and protect mice
from lethal challenge. The murine antibody 16F6, which binds the SUDV
envelope glycoprotein (GP), served as the starting point for design.
Sequence and structural alignment revealed similarities between 16F6
and YADS1, a synthetic antibody with a humanized scaffold. A focused
phage library was constructed and screened to impart 16F6-like recognition
properties onto the YADS1 scaffold. A panel of 17 antibodies were
characterized and found to have a range of neutralization potentials
against a pseudotype virus infection model. Neutralization correlated
with GP binding as determined by ELISA. Two of these clones, E10 and
F4, potently inhibited authentic SUDV and conferred protection and
memory immunity in mice from lethal SUDV challenge. E10 and F4 were
further shown to bind to the same epitope on GP as 16F6 with comparable
affinities. These antibodies represent strong immunotherapeutic candidates
for treatment of SUDV infection.
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Affiliation(s)
- Gang Chen
- Banting
and Best Department of Medical Research, Terrence Donnelly Centre
for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, Canada M5S 3E1
| | | | - Samantha E. Zak
- Virology
Division, United States Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Maryland 21702, United States
| | | | | | - Hua Long
- Banting
and Best Department of Medical Research, Terrence Donnelly Centre
for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, Canada M5S 3E1
| | - Wei Ye
- Banting
and Best Department of Medical Research, Terrence Donnelly Centre
for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, Canada M5S 3E1
| | - Kaajal Nagar
- Banting
and Best Department of Medical Research, Terrence Donnelly Centre
for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, Canada M5S 3E1
| | - Guohua Pan
- Banting
and Best Department of Medical Research, Terrence Donnelly Centre
for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, Canada M5S 3E1
| | | | - John M. Dye
- Virology
Division, United States Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Maryland 21702, United States
| | - Sachdev S. Sidhu
- Banting
and Best Department of Medical Research, Terrence Donnelly Centre
for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON, Canada M5S 3E1
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Harrison JS, Higgins CD, O'Meara MJ, Koellhoffer JF, Kuhlman BA, Lai JR. Role of electrostatic repulsion in controlling pH-dependent conformational changes of viral fusion proteins. Structure 2014; 21:1085-96. [PMID: 23823327 DOI: 10.1016/j.str.2013.05.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 05/07/2013] [Accepted: 05/13/2013] [Indexed: 11/29/2022]
Abstract
Viral fusion proteins undergo dramatic conformational transitions during membrane fusion. For viruses that enter through the endosome, these conformational rearrangements are typically pH sensitive. Here, we provide a comprehensive review of the molecular interactions that govern pH-dependent rearrangements and introduce a paradigm for electrostatic residue pairings that regulate progress through the viral fusion coordinate. Analysis of structural data demonstrates a significant role for side-chain protonation in triggering conformational change. To characterize this behavior, we identify two distinct residue pairings, which we define as Histidine-Cation (HisCat) and Anion-Anion (AniAni) interactions. These side-chain pairings destabilize a particular conformation via electrostatic repulsion through side-chain protonation. Furthermore, two energetic control mechanisms, thermodynamic and kinetic, regulate these structural transitions. This review expands on the current literature by identification of these residue clusters, discussion of data demonstrating their function, and speculation of how these residue pairings contribute to the energetic controls.
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Affiliation(s)
- Joseph S Harrison
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
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3
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Koellhoffer JF, Higgins CD, Lai JR. Protein engineering strategies for the development of viral vaccines and immunotherapeutics. FEBS Lett 2013; 588:298-307. [PMID: 24157357 DOI: 10.1016/j.febslet.2013.10.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 10/12/2013] [Accepted: 10/14/2013] [Indexed: 01/12/2023]
Abstract
Vaccines that elicit a protective broadly neutralizing antibody (bNAb) response and monoclonal antibody therapies are critical for the treatment and prevention of viral infections. However, isolation of protective neutralizing antibodies has been challenging for some viruses, notably those with high antigenic diversity or those that do not elicit a bNAb response in the course of natural infection. Here, we discuss recent work that employs protein engineering strategies to design immunogens that elicit bNAbs or engineer novel bNAbs. We highlight the use of rational, computational, and combinatorial strategies and assess the potential of these approaches for the development of new vaccines and immunotherapeutics.
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Affiliation(s)
- Jayne F Koellhoffer
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, United States
| | - Chelsea D Higgins
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, United States
| | - Jonathan R Lai
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, United States.
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Higgins CD, Koellhoffer JF, Chandran K, Lai JR. C-peptide inhibitors of Ebola virus glycoprotein-mediated cell entry: effects of conjugation to cholesterol and side chain-side chain crosslinking. Bioorg Med Chem Lett 2013; 23:5356-60. [PMID: 23962564 DOI: 10.1016/j.bmcl.2013.07.056] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/19/2013] [Accepted: 07/24/2013] [Indexed: 11/20/2022]
Abstract
We previously described potent inhibition of Ebola virus entry by a 'C-peptide' based on the GP2 C-heptad repeat region (CHR) targeted to endosomes ('Tat-Ebo'). Here, we report the synthesis and evaluation of C-peptides conjugated to cholesterol, and Tat-Ebo analogs containing covalent side chain-side chain crosslinks to promote α-helical conformation. We found that the cholesterol-conjugated C-peptides were potent inhibitors of Ebola virus glycoprotein (GP)-mediated cell entry (~10(3)-fold reduction in infection at 40 μM). However, this mechanism of inhibition is somewhat non-specific because the cholesterol-conjugated peptides also inhibited cell entry mediated by vesicular stomatitis virus glycoprotein G. One side chain-side chain crosslinked peptide had moderately higher activity than the parent compound Tat-Ebo. Circular dichroism revealed that the cholesterol-conjugated peptides unexpectedly formed a strong α-helical conformation that was independent of concentration. Side chain-side chain crosslinking enhanced α-helical stability of the Tat-Ebo variants, but only at neutral pH. These result provide insight into mechanisms of C-peptide inhibiton of Ebola virus GP-mediated cell entry.
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Affiliation(s)
- Chelsea D Higgins
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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5
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Regula LK, Harris R, Wang F, Higgins CD, Koellhoffer JF, Zhao Y, Chandran K, Gao J, Girvin ME, Lai JR. Conformational properties of peptides corresponding to the ebolavirus GP2 membrane-proximal external region in the presence of micelle-forming surfactants and lipids. Biochemistry 2013; 52:3393-404. [PMID: 23650881 DOI: 10.1021/bi400040v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ebola virus and Sudan virus are members of the family Filoviridae of nonsegmented negative-strand RNA viruses ("filoviruses") that cause severe hemorrhagic fever with fatality rates as high as 90%. Infection by filoviruses requires membrane fusion between the host and the virus; this process is facilitated by the two subunits of the envelope glycoprotein, GP1 (the surface subunit) and GP2 (the transmembrane subunit). The membrane-proximal external region (MPER) is a Trp-rich segment that immediately precedes the transmembrane domain of GP2. In the analogous glycoprotein for HIV-1 (gp41), the MPER is critical for membrane fusion and is the target of several neutralizing antibodies. However, the role of the MPER in filovirus GP2 and its importance in membrane fusion have not been established. Here, we characterize the conformational properties of peptides representing the GP MPER segments of Ebola virus and Sudan virus in the presence of micelle-forming surfactants and lipids, at pH 7 and 4.6. Circular dichroism spectroscopy and tryptophan fluorescence indicate that the GP2 MPER peptides bind to micelles of sodium dodecyl sulfate and dodecylphosphocholine (DPC). Nuclear magnetic resonance spectroscopy of the Sudan virus MPER peptide revealed that residues 644-651 interact directly with DPC, and that this interaction enhances the helical conformation of the peptide. The Sudan virus MPER peptide was found to moderately inhibit cell entry by a GP-pseudotyped vesicular stomatitis virus but did not induce leakage of a fluorescent molecule from a large unilammellar vesicle comprised of 1-palmitoyl-2-oleoylphosphatidylcholine or cause hemolysis. Taken together, this analysis suggests the filovirus GP2 MPER binds and inserts shallowly into lipid membranes.
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Affiliation(s)
- Lauren K Regula
- Department of Biochemistry and ‡Department of Microbiology and Immunology, Albert Einstein College of Medicine , 1300 Morris Park Avenue, Bronx, New York 10461, United States
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Koellhoffer JF, Chen G, Sandesara RG, Bale S, Saphire EO, Chandran K, Sidhu SS, Lai JR. Two synthetic antibodies that recognize and neutralize distinct proteolytic forms of the ebola virus envelope glycoprotein. Chembiochem 2012; 13:2549-57. [PMID: 23111988 DOI: 10.1002/cbic.201200493] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Indexed: 11/06/2022]
Abstract
Ebola virus (EBOV) is a highly pathogenic member of the Filoviridae family of viruses that causes severe hemorrhagic fever. Infection proceeds through fusion of the host cell and viral membranes, a process that is mediated by the viral envelope glycoprotein (GP). Following endosomal uptake, a key step in viral entry is the proteolytic cleavage of GP by host endosomal cysteine proteases. Cleavage exposes a binding site for the host cell receptor Niemann-Pick C1 (NPC1) and may induce conformational changes in GP leading to membrane fusion. However, the precise details of the structural changes in GP associated with proteolysis and the role of these changes in viral entry have not been established. Here, we have employed synthetic antibody technology to identify antibodies targeting EBOV GP prior to and following proteolysis (i.e. in the "uncleaved" [GP(UNCL)] and "cleaved" [GP(CL)] forms). We identified antibodies with distinct recognition profiles: Fab(CL) bound preferentially to GP(CL) (EC(50)=1.7 nM), whereas Fab(UNCL) bound specifically to GP(UNCL) (EC(50)=75 nM). Neutralization assays with GP-containing pseudotyped viruses indicated that these antibodies inhibited GP(CL)- or GP(UNCL)-mediated viral entry with specificity matching their recognition profiles (IC(50): 87 nM for IgG(CL); 1 μM for Fab(UNCL)). Competition ELISAs indicate that Fab(CL) binds an epitope distinct from that of KZ52, a well-characterized EBOV GP antibody, and from that of the luminal domain of NPC1. The binding epitope of Fab(UNCL) was also distinct from that of KZ52, suggesting that Fab(UNCL) binds a novel neutralization epitope on GP(UNCL). Furthermore, the neutralizing ability of Fab(CL) suggests that there are targets on GP(CL) available for neutralization. This work showcases the applicability of synthetic antibody technology to the study of viral membrane fusion, and provides new tools for dissecting intermediates of EBOV entry.
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Affiliation(s)
- Jayne F Koellhoffer
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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Koellhoffer JF, Malashkevich VN, Harrison JS, Toro R, Bhosle RC, Chandran K, Almo SC, Lai JR. Crystal structure of the Marburg virus GP2 core domain in its postfusion conformation. Biochemistry 2012; 51:7665-75. [PMID: 22935026 DOI: 10.1021/bi300976m] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Marburg virus (MARV) and Ebola virus (EBOV) are members of the family Filoviridae ("filoviruses") and cause severe hemorrhagic fever with human case fatality rates of up to 90%. Filovirus infection requires fusion of the host cell and virus membranes, a process that is mediated by the envelope glycoprotein (GP). GP contains two subunits, the surface subunit (GP1), which is responsible for cell attachment, and the transmembrane subunit (GP2), which catalyzes membrane fusion. The GP2 ectodomain contains two heptad repeat regions, N-terminal and C-terminal (NHR and CHR, respectively), that adopt a six-helix bundle during the fusion process. The refolding of this six-helix bundle provides the thermodynamic driving force to overcome barriers associated with membrane fusion. Here we report the crystal structure of the MARV GP2 core domain in its postfusion (six-helix bundle) conformation at 1.9 Å resolution. The MARV GP2 core domain backbone conformation is virtually identical to that of EBOV GP2 (reported previously), and consists of a central NHR core trimeric coiled coil packed against peripheral CHR α-helices and an intervening loop and helix-turn-helix segments. We previously reported that the stability of the MARV GP2 postfusion structure is highly pH-dependent, with increasing stability at lower pH [Harrison, J. S., Koellhoffer, J. K., Chandran, K., and Lai, J. R. (2012) Biochemistry51, 2515-2525]. We hypothesized that this pH-dependent stability provides a mechanism for conformational control such that the postfusion six-helix bundle is promoted in the environments of appropriately mature endosomes. In this report, a structural rationale for this pH-dependent stability is described and involves a high-density array of core and surface acidic side chains at the midsection of the structure, termed the "anion stripe". In addition, many surface-exposed salt bridges likely contribute to the stabilization of the postfusion structure at low pH. These results provide structural insights into the mechanism of MARV GP2-mediated membrane fusion.
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Affiliation(s)
- Jayne F Koellhoffer
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States
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Harrison JS, Koellhoffer JF, Chandran K, Lai JR. Marburg virus glycoprotein GP2: pH-dependent stability of the ectodomain α-helical bundle. Biochemistry 2012; 51:2515-25. [PMID: 22369502 DOI: 10.1021/bi3000353] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Marburg virus (MARV) and Ebola virus (EBOV) constitute the family Filoviridae of enveloped viruses (filoviruses) that cause severe hemorrhagic fever. Infection by MARV requires fusion between the host cell and viral membranes, a process that is mediated by the two subunits of the envelope glycoprotein, GP1 (surface subunit) and GP2 (transmembrane subunit). Upon viral attachment and uptake, it is believed that the MARV viral fusion machinery is triggered by host factors and environmental conditions found in the endosome. Next, conformational rearrangements in the GP2 ectodomain result in the formation of a highly stable six-helix bundle; this refolding event provides the energetic driving force for membrane fusion. Both GP1 and GP2 from EBOV have been extensively studied, but there is little information available for the MARV glycoproteins. Here we have expressed two variants of the MARV GP2 ectodomain in Escherichia coli and analyzed their biophysical properties. Circular dichroism indicates that the MARV GP2 ectodomain adopts an α-helical conformation, and one variant sediments as a trimer by equilibrium analytical ultracentrifugation. Denaturation studies indicate the α-helical structure is highly stable at pH 5.3 (unfolding energy, ΔG(unf,H(2)O), of 33.4 ± 2.5 kcal/mol and melting temperature, T(m), of 75.3 ± 2.1 °C for one variant). Furthermore, we found the α-helical stability to be strongly dependent on pH, with higher stability under lower-pH conditions (T(m) values ranging from ~92 °C at pH 4.0 to ~38 °C at pH 8.0). Mutational analysis suggests two glutamic acid residues (E579 and E580) are partially responsible for this pH-dependent behavior. On the basis of these results, we hypothesize that the pH-dependent folding stability of the MARV GP2 ectodomain provides a mechanism for controlling conformational preferences such that the six-helix bundle "postfusion" state is preferred under conditions of appropriately matured endosomes.
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Affiliation(s)
- Joseph S Harrison
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States
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