201
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Strategies for development of dengue virus inhibitors. Antiviral Res 2010; 85:450-62. [DOI: 10.1016/j.antiviral.2009.12.011] [Citation(s) in RCA: 211] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 12/16/2009] [Accepted: 12/30/2009] [Indexed: 01/03/2023]
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202
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Hessell AJ, Poignard P, Hunter M, Hangartner L, Tehrani DM, Bleeker WK, Parren PWHI, Marx PA, Burton DR. Effective, low-titer antibody protection against low-dose repeated mucosal SHIV challenge in macaques. Nat Med 2009; 15:951-4. [PMID: 19525965 DOI: 10.1038/nm.1974] [Citation(s) in RCA: 458] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 04/28/2009] [Indexed: 01/09/2023]
Abstract
Neutralizing antibodies are thought to be crucial for HIV vaccine protection, but studies in animal models suggest that high antibody concentrations are required. This is a major potential hurdle for vaccine design. However, these studies typically apply a large virus inoculum to ensure infection in control animals in single-challenge experiments. In contrast, most human infection via sexual encounter probably involves repeated exposures to much lower doses of virus. Therefore, animal studies may have provided an overestimate of the levels of antibodies required for protection in humans. We investigated whether plasma concentrations of antibody corresponding to relatively modest neutralization titers in vitro could protect macaques from repeated intravaginal exposure to low doses of a simian immunodeficiency virus-HIV chimera (SHIV) that uses the CC chemokine receptor 5 (CCR5) co-receptor. An effector function-deficient variant of the neutralizing antibody was also included. The results show that a substantially larger number of challenges is required to infect macaques treated with neutralizing antibody than control antibody-treated macaques, and support the notion that effector function may contribute to antibody protection. Overall, the results imply that lower amounts of antibody than previously considered protective may provide benefit in the context of typical human exposure to HIV-1.
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Affiliation(s)
- Ann J Hessell
- Department of Immunology and Microbial Science and International AIDS Vaccine Initiative Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, California, USA
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203
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Utilization of immunoglobulin G Fc receptors by human immunodeficiency virus type 1: a specific role for antibodies against the membrane-proximal external region of gp41. J Virol 2009; 83:7397-410. [PMID: 19458010 DOI: 10.1128/jvi.00656-09] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Receptors (FcgammaRs) for the constant region of immunoglobulin G (IgG) are an important link between humoral immunity and cellular immunity. To help define the role of FcgammaRs in determining the fate of human immunodeficiency virus type 1 (HIV-1) immune complexes, cDNAs for the four major human Fcgamma receptors (FcgammaRI, FcgammaRIIa, FcgammaRIIb, and FcgammaRIIIa) were stably expressed by lentiviral transduction in a cell line (TZM-bl) commonly used for standardized assessments of HIV-1 neutralization. Individual cell lines, each expressing a different FcgammaR, bound human IgG, as evidence that the physical properties of the receptors were preserved. In assays with a HIV-1 multisubtype panel, the neutralizing activities of two monoclonal antibodies (2F5 and 4E10) that target the membrane-proximal external region (MPER) of gp41 were potentiated by FcgammaRI and, to a lesser extent, by FcgammaRIIb. Moreover, the neutralizing activity of an HIV-1-positive plasma sample known to contain gp41 MPER-specific antibodies was potentiated by FcgammaRI. The neutralizing activities of monoclonal antibodies b12 and 2G12 and other HIV-1-positive plasma samples were rarely affected by any of the four FcgammaRs. Effects with gp41 MPER-specific antibodies were moderately stronger for IgG1 than for IgG3 and were ineffective for Fab. We conclude that FcgammaRI and FcgammaRIIb facilitate antibody-mediated neutralization of HIV-1 by a mechanism that is dependent on the Fc region, IgG subclass, and epitope specificity of antibody. The FcgammaR effects seen here suggests that the MPER of gp41 could have greater value for vaccines than previously recognized.
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204
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Nechansky A, Szolar OHJ, Siegl P, Zinoecker I, Halanek N, Wiederkum S, Kircheis R. Complement dependent cytotoxicity (CDC) activity of a humanized anti Lewis-Y antibody: FACS-based assay versus the 'classical' radioactive method -- qualification, comparison and application of the FACS-based approach. J Pharm Biomed Anal 2009; 49:1014-20. [PMID: 19250790 DOI: 10.1016/j.jpba.2009.01.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 01/21/2009] [Accepted: 01/22/2009] [Indexed: 11/16/2022]
Abstract
The fully humanized Lewis-Y carbohydrate specific monoclonal antibody (mAb) IGN311 is currently tested in a passive immunotherapy approach in a clinical phase I trail and therefore regulatory requirements demand qualified assays for product analysis. To demonstrate the functionality of its Fc-region, the capacity of IGN311 to mediate complement dependent cytotoxicity (CDC) against human breast cancer cells was evaluated. The "classical" radioactive method using chromium-51 and a FACS-based assay were established and qualified according to ICH guidelines. Parameters evaluated were specificity, response function, bias, repeatability (intra-day precision), intermediate precision (operator-time different), and linearity (assay range). In the course of a fully nested design, a four-parameter logistic equation was identified as appropriate calibration model for both methods. For the radioactive assay, the bias ranged from -6.1% to -3.6%. The intermediate precision for future means of duplicate measurements revealed values from 12.5% to 15.9% and the total error (beta-expectation tolerance interval) of the method was found to be <40%. For the FACS-based assay, the bias ranged from -8.3% to 0.6% and the intermediate precision for future means of duplicate measurements revealed values from 4.2% to 8.0%. The total error of the method was found to be <25%. The presented data demonstrate that the FACS-based CDC is more accurate than the radioactive assay. Also, the elimination of radioactivity and the 'real-time' counting of apoptotic cells further justifies the implementation of this method which was subsequently applied for testing the influence of storage at 4 degrees C and 25 degrees C ('stability testing') on the potency of IGN311 drug product. The obtained results demonstrate that the qualified functional assay represents a stability indicating test method.
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Affiliation(s)
- A Nechansky
- Vela Pharmazeutische Entwicklung und Laboranalytik GmbH, Vienna, Austria.
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205
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CD4+ T lymphocytes mediate in vivo clearance of plasmid DNA vaccine antigen expression and potentiate CD8+ T-cell immune responses. Blood 2008; 112:4585-90. [PMID: 18784371 DOI: 10.1182/blood-2008-06-165803] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There is evidence that the limited immunogenicity of plasmid DNA vaccines is the result, at least in part, of the rapid clearance of vaccine antigen expression by antigen-specific immune responses. However, the cell types responsible for the clearance of plasmid DNA vaccine antigens are not known. Here we demonstrate that macrophages, NK cells, and CD8(+) T cells did not significantly contribute to the DNA antigen clearance but CD4(+) T cells played the crucial role in attenuating plasmid DNA vaccine antigen expression. Adoptive transfer experiments demonstrate that CD4(+) T cells facilitated DNA vaccine antigen clearance in a Fas/FasL-dependent manner. Furthermore, we show that depletion of CD4(+) T cells prevented the clearance of vaccine antigen and the appearance of a CD8(+) T-cell immune response. Inoculation of major histocompatibility complex class II KO mice with the plasmid DNA led to persistent antigen expression and abolition of a CD8(+) T-cell immune response. Importantly, the prolongation of antigen expression by disrupting the CD4(+) T-cell Fas/FasL myocytes signaling led to a 3- to 5-fold increase of antigen-specific CD8(+) T-cell responses. These data demonstrate a dominant role of CD4(+) T cell-mediated cytotoxicity in plasmid DNA vaccine antigen clearance.
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206
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Labrijn AF, Aalberse RC, Schuurman J. When binding is enough: nonactivating antibody formats. Curr Opin Immunol 2008; 20:479-85. [PMID: 18577454 DOI: 10.1016/j.coi.2008.05.010] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Revised: 05/23/2008] [Accepted: 05/27/2008] [Indexed: 01/12/2023]
Abstract
Most therapeutic antibodies currently used in the clinic are based on the human IgG1 format, which is a bivalent molecule that efficiently interacts with the immune system's effector functions. In clinical applications where binding to the target alone is sufficient for therapeutic efficacy; however, engagement of the immune system is not required and may even cause unwanted side-effects. Likewise, bivalent binding to the target may negatively influence the therapeutic efficacy of an antibody. Here we discuss the state of the art for antibody-based therapeutics, designed to be nonactivating (i.e. do not engage the innate immune system's effector functions), in both monovalent and bivalent formats.
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207
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Oganesyan V, Gao C, Shirinian L, Wu H, Dall’Acqua WF. Structural characterization of a human Fc fragment engineered for lack of effector functions. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2008; 64:700-4. [PMID: 18560159 PMCID: PMC2467532 DOI: 10.1107/s0907444908007877] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Accepted: 03/22/2008] [Indexed: 11/10/2022]
Abstract
The first three-dimensional structure of a human Fc fragment genetically engineered for the elimination of its ability to mediate antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity is reported. When introduced into the lower hinge and CH2 domain of human IgG1 molecules, the triple mutation L234F/L235E/P331S ('TM') causes a profound decrease in their binding to human CD64, CD32A, CD16 and C1q. Enzymatically produced Fc/TM fragment was crystallized and its structure was solved at a resolution of 2.3 A using molecular replacement. This study revealed that the three-dimensional structure of Fc/TM is very similar to those of other human Fc fragments in the experimentally visible region spanning residues 236-445. Thus, the dramatic broad-ranging effects of TM on IgG binding to several effector molecules cannot be explained in terms of major structural rearrangements in this portion of the Fc.
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Affiliation(s)
- Vaheh Oganesyan
- Department of Antibody Discovery and Protein Engineering, MedImmune Inc., One MedImmune Way, Gaithersburg, MD 20878, USA
| | - Changshou Gao
- Department of Antibody Discovery and Protein Engineering, MedImmune Inc., One MedImmune Way, Gaithersburg, MD 20878, USA
| | - Lena Shirinian
- Department of Antibody Discovery and Protein Engineering, MedImmune Inc., One MedImmune Way, Gaithersburg, MD 20878, USA
| | - Herren Wu
- Department of Antibody Discovery and Protein Engineering, MedImmune Inc., One MedImmune Way, Gaithersburg, MD 20878, USA
| | - William F. Dall’Acqua
- Department of Antibody Discovery and Protein Engineering, MedImmune Inc., One MedImmune Way, Gaithersburg, MD 20878, USA
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208
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Hepatitis C virus (HCV)-induced immunoglobulin hypermutation reduces the affinity and neutralizing activities of antibodies against HCV envelope protein. J Virol 2008; 82:6711-20. [PMID: 18417597 DOI: 10.1128/jvi.02582-07] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Hepatitis C virus (HCV) often causes persistent infection despite the presence of neutralizing antibodies against the virus in the sera of hepatitis C patients. HCV infects both hepatocytes and B cells through the binding of its envelope glycoprotein E2 to CD81, the putative viral receptor. Previously, we have shown that E2-CD81 interaction induces hypermutation of heavy-chain immunoglobulin (V(H)) in B cells. We hypothesize that if HCV infects antibody-producing B cells, the resultant hypermutation of V(H) may lower the affinity and specificity of the HCV-specific antibodies, enabling HCV to escape from immune surveillance. To test this hypothesis, we infected human hybridoma clones producing either neutralizing or non-neutralizing anti-E2 or anti-E1 antibodies with a lymphotropic HCV (SB strain). All of the hybridoma clones, except for a neutralizing antibody-producing hybridoma, could be infected with HCV and support virus replication for at least 8 weeks after infection. The V(H) sequences in the infected hybridomas had a significantly higher mutation frequency than those in the uninfected hybridomas, with mutations concentrating in complementarity-determining region 3. These mutations lowered the antibody affinity against the targeting protein and also lowered the virus-neutralizing activity of anti-E2 antibodies. Furthermore, antibody-mediated complement-dependent cytotoxicity with the antibodies secreted from the HCV-infected hybridomas was impaired. These results suggest that HCV infection could cause some anti-HCV-antibody-producing hybridoma B cells to make less-protective antibodies.
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209
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Hessell AJ, Hangartner L, Hunter M, Havenith CEG, Beurskens FJ, Bakker JM, Lanigan CMS, Landucci G, Forthal DN, Parren PWHI, Marx PA, Burton DR. Fc receptor but not complement binding is important in antibody protection against HIV. Nature 2007; 449:101-4. [PMID: 17805298 DOI: 10.1038/nature06106] [Citation(s) in RCA: 737] [Impact Index Per Article: 43.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 07/20/2007] [Indexed: 11/08/2022]
Abstract
Most successful vaccines elicit neutralizing antibodies and this property is a high priority when developing an HIV vaccine. Indeed, passively administered neutralizing antibodies have been shown to protect against HIV challenge in some of the best available animal models. For example, antibodies given intravenously can protect macaques against intravenous or mucosal SHIV (an HIV/SIV chimaera) challenge and topically applied antibodies can protect macaques against vaginal SHIV challenge. However, the mechanism(s) by which neutralizing antibodies afford protection against HIV is not understood and, in particular, the role of antibody Fc-mediated effector functions is unclear. Here we report that there is a dramatic decrease in the ability of a broadly neutralizing antibody to protect macaques against SHIV challenge when Fc receptor and complement-binding activities are engineered out of the antibody. No loss of antibody protective activity is associated with the elimination of complement binding alone. Our in vivo results are consistent with in vitro assays indicating that interaction of Fc-receptor-bearing effector cells with antibody-complexed infected cells is important in reducing virus yield from infected cells. Overall, the data suggest the potential importance of activity against both infected cells and free virus for effective protection against HIV.
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Affiliation(s)
- Ann J Hessell
- Department of Immunology and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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210
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Abstract
Humoral immunity is considered a key component of effective vaccines against HIV-1. Hence, an enormous effort has been put into investigating the neutralizing antibody response to HIV-1 over the past 20 years which generated key information on epitope specificity, potency, breadth and in vivo activity of the neutralizing antibodies. Less clear is still the role of antibody-mediated effector functions (antibody-dependent cellular cytotoxicity, phagocytosis, complement system) and uncertainty prevails whether Fc-mediated mechanisms are largely beneficial or detrimental for the host. The current knowledge on the manifold functions of the humoral immune response in HIV infection, their underlying mechanisms and potential in vaccine-induced immunity will be discussed in this review.
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Affiliation(s)
- M Huber
- Division of Infectious Diseases, University Hospital Zurich, Zurich, Switzerland
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211
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Greenland JR, Geiben R, Ghosh S, Pastor WA, Letvin NL. Plasmid DNA vaccine-elicited cellular immune responses limit in vivo vaccine antigen expression through Fas-mediated apoptosis. THE JOURNAL OF IMMUNOLOGY 2007; 178:5652-8. [PMID: 17442948 PMCID: PMC2262927 DOI: 10.4049/jimmunol.178.9.5652] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Particularly potent cellular or humoral immune responses are needed to confer protection in animal models against such pathogens as HIV/SIV, Mycobacterium tuberculosis, and malarial parasites. Persistent, high-level vaccine Ag expression may be required for eliciting such potent and durable immune responses. Although plasmid DNA immunogens are being explored as potential vaccines for protection against these pathogens, little is known about host factors that restrict long-term plasmid DNA vaccine Ag expression in vivo. We observed rapid damping of transgene expression from a plasmid DNA immunogen in wild-type, but not in T cell-deficient mice. This damping of Ag expression was temporally associated with the emergence of Ag-specific cellular immune responses. A requirement for Fas and the appearance of apoptotic nuclei at the site of vaccine inoculation suggest that T cells induce Fas-mediated apoptosis of plasmid DNA vaccine Ag-expressing cells. These studies demonstrate that high levels of in vivo Ag expression are associated with high-frequency cellular immune responses that in turn rapidly down-regulate vaccine Ag expression in vivo. These findings argue that it may not be possible to maintain persistent, high-level production of vaccine Ag in vivo to drive persistent immune responses as long as vaccine Ag production can be limited by host immune responses.
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Affiliation(s)
| | | | | | | | - Norman L. Letvin
- Address correspondence and reprint requests to Dr. Norman L. Letvin, Division of Viral Pathogenesis, Harvard Medical School, Beth Israel Deaconess Medical Center, 41 Avenue Louis Pasteur, Boston, MA 02215; E-mail address:
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212
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Gómez-Román VR, Florese RH, Peng B, Montefiori DC, Kalyanaraman VS, Venzon D, Srivastava I, Barnett SW, Robert-Guroff M. An adenovirus-based HIV subtype B prime/boost vaccine regimen elicits antibodies mediating broad antibody-dependent cellular cytotoxicity against non-subtype B HIV strains. J Acquir Immune Defic Syndr 2006; 43:270-7. [PMID: 16940858 DOI: 10.1097/01.qai.0000230318.40170.60] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Although HIV subtype B predominates in North America and Western Europe, most HIV infections worldwide are non-subtype B. Globally effective AIDS vaccines need to elicit broad immunity against multiple HIV strains. In this study, 10 chimpanzees were intranasally primed sequentially with adenovirus type 5 (Ad5)- and Ad7-HIVMNenv/rev recombinants and boosted twice intramuscularly with heterologous oligomeric HIVSF162 gp140DeltaV2 protein in MF59 adjuvant. Sera were evaluated for binding, neutralizing, and antibody-dependent cellular cytotoxicity (ADCC) against HIV clades A, B, C, and CRF01_AE. The vaccine regimen elicited high-titered HIV subtype A, B, C and CRF01_AE gp120-binding antibodies. Sera from 7 of 10 vaccinated chimpanzees cross-neutralized the heterologous South African subtype C primary HIVTV-1 isolate. Significant cross-clade neutralization against other subtype A, C and E isolates was not observed. Sera from all animals mediated ADCC of cells coated with gp120 from HIV subtypes A and B. Nine of 10 animals also exhibited ADCC activity against HIV subtype C and CRF01_AE gp120-coated targets. This subtype B Ad-HIV recombinant prime/envelope protein boost regimen is a promising approach for eliciting broad ADCC activity against diverse HIV clades. Incorporating additional non-subtype B envelope genes and protein boosts in a multivalent strategy may be required to elicit broader neutralizing antibodies against non-subtype B HIV strains.
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Affiliation(s)
- V Raúl Gómez-Román
- Vaccine Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-5065, USA
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213
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Florese RH, Van Rompay KKA, Aldrich K, Forthal DN, Landucci G, Mahalanabis M, Haigwood N, Venzon D, Kalyanaraman VS, Marthas ML, Robert-Guroff M. Evaluation of passively transferred, nonneutralizing antibody-dependent cellular cytotoxicity-mediating IgG in protection of neonatal rhesus macaques against oral SIVmac251 challenge. THE JOURNAL OF IMMUNOLOGY 2006; 177:4028-36. [PMID: 16951366 DOI: 10.4049/jimmunol.177.6.4028] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Previously, Ab-dependent cellular cytotoxicity (ADCC) was significantly correlated with reduced acute viremia upon intrarectal SIVmac251 challenge of immunized rhesus macaques. To directly assess ADCC protective efficacy, six neonatal macaques were infused s.c. with immune IgG (220 mg/kg) purified from the immunized animals and positive for ADCC and Ab-dependent cell-mediated viral inhibition (ADCVI) activities. Six neonates received control IgG. The neonates were challenged twice orally with 10(5) 50% inhibiting tissue culture-infective dose of SIVmac251 2 days post-IgG infusion. At challenge, plasma of neonates that received immune IgG did not neutralize SIVmac251 but had geometric mean ADCC titers of 48,130 and 232,850 against SIVmac251 -infected and gp120-coated targets, respectively. Peak ADCVI activity varied from 62 to 81%. ADCC activity declined with the 2-wk IgG half-life but was boosted at wk 4, together with de novo ADCC-mediating Abs in controls, by postchallenge viremia. ADCVI activity was similarly induced. No protection, assessed by viral burdens, CD4 counts, and time to euthanasia was observed. Possible factors contributing to the discrepancy between the previous correlation and lack of protection here include: the high oral challenge dose compared with the 400-fold lower intrarectal dose; the challenge route with regard to viral dissemination and distribution of infused IgG; insufficient NK effector activity and/or poor functionality in newborns; insufficient immune IgG; and the possibility that the previous correlation of ADCC with protection was augmented by cellular immune responses also present at challenge. Future studies should explore additional challenge routes in juvenile macaques using higher amounts of potent IgG preparations.
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Affiliation(s)
- Ruth H Florese
- Vaccine Branch, National Cancer Institute, Bethesda, MD 20892-5065, USA
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214
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Forthal DN, Landucci G, Cole KS, Marthas M, Becerra JC, Van Rompay K. Rhesus macaque polyclonal and monoclonal antibodies inhibit simian immunodeficiency virus in the presence of human or autologous rhesus effector cells. J Virol 2006; 80:9217-25. [PMID: 16940533 PMCID: PMC1563916 DOI: 10.1128/jvi.02746-05] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although antibodies can prevent or modulate lentivirus infections in nonhuman primates, the biological functions of antibody responsible for such effects are not known. We sought to determine the role of antibody-dependent cell-mediated virus inhibition (ADCVI), an antibody function that inhibits virus yield from infected cells in the presence of Fc receptor-bearing effector cells, in preventing or controlling SIVmac251 infection in rhesus macaques (Macaca mulatta). Using CEMx174 cells infected with simian immunodeficiency virus mac251 (SIVmac251), both polyclonal and monoclonal anti-SIV antibodies were capable of potent virus inhibition in the presence of human peripheral blood mononuclear cell (PBMC) effector cells. In the absence of effector cells, virus inhibition was generally very poor. PBMCs from healthy rhesus macaques were also capable of mediating virus inhibition either against SIVmac251-infected CEMx174 cells or against infected, autologous rhesus target cells. We identified both CD14(+) cells and, to a lesser extent, CD8(+) cells as the effector cell population in the rhesus PBMCs. Finally, pooled, nonneutralizing SIV-antibody-positive serum, shown in a previous study to prevent infection of neonatal macaques after oral SIVmac251 challenge, had potent virus-inhibitory activity in the presence of effector cells; intact immunoglobulin G, rather than F(ab')(2), was required for such activity. This is the first demonstration of both humoral and cellular ADCVI functions in the macaque-SIV model. ADCVI activity in nonneutralizing serum that prevents SIV infection suggests that ADCVI may be a protective immune function. Finally, our data underscore the potential importance of Fc-Fc receptor interactions in mediating biological activities of antibody.
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Affiliation(s)
- Donald N Forthal
- Department of Medicine, Division of Infectious Diseases, School of Medicine, University of California-Irvine, Irvine, CA 92697-4028, USA.
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215
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Ferrantelli F, Buckley KA, Rasmussen RA, Chalmers A, Wang T, Li PL, Williams AL, Hofmann-Lehmann R, Montefiori DC, Cavacini LA, Katinger H, Stiegler G, Anderson DC, McClure HM, Ruprecht RM. Time dependence of protective post-exposure prophylaxis with human monoclonal antibodies against pathogenic SHIV challenge in newborn macaques. Virology 2006; 358:69-78. [PMID: 16996554 DOI: 10.1016/j.virol.2006.07.056] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Revised: 05/18/2006] [Accepted: 07/28/2006] [Indexed: 11/21/2022]
Abstract
In a primate model of postnatal virus transmission, we have previously shown that 1 h post-exposure prophylaxis (PEP) with a triple combination of neutralizing monoclonal antibodies (nmAbs) conferred sterilizing protection to neonatal macaques against oral challenge with pathogenic simian-human immunodeficiency virus (SHIV). Here, we show that nmAbs can also partially protect SHIV-exposed newborn macaques against infection or disease, when given as 12 or 24 h PEP, respectively. This work delineates the potential and the limits of passive immunoprophylaxis with nmAbs. Even though 24 h PEP with nmAbs did not provide sterilizing immunity to neonatal monkeys, it contained viremia and protected infants from acute disease. Taken together with our results from other PEP studies, these data show that the success of passive immunization depends on the nmAb potency/dose and the time window between virus exposure and start of immunotherapy.
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Affiliation(s)
- Flavia Ferrantelli
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115, USA
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216
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Dall'Acqua WF, Cook KE, Damschroder MM, Woods RM, Wu H. Modulation of the effector functions of a human IgG1 through engineering of its hinge region. THE JOURNAL OF IMMUNOLOGY 2006; 177:1129-38. [PMID: 16818770 DOI: 10.4049/jimmunol.177.2.1129] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We report here the engineering of a humanized anti-human EphA2 mAb (mAb 12G3H11) in an effort to explore the relationship between the hinge of a human IgG1 and its effector functions. mAb 12G3H11, used here as a model, is directed against the human receptor tyrosine kinase EphA2, which is an actively investigated target for cancer therapy due to its up-regulation in many cancer cells. Various rational modifications were introduced into the hinge region of mAb 12G3H11. These mutations were predicted to modulate the hinge's length, flexibility, and/or biochemical properties. We show that the upper and middle hinge both play important, although functionally distinct roles. In particular, middle hinge modifications predicted to decrease its rigidity or length as well as eliminating either one of its two cysteine residues had a strong negative impact on C1q binding and complement-dependent cytotoxicity. Disruption of covalent bonds between both H chains may account in part for these effects. We also describe middle hinge mutants with a significantly decreased ability to bind FcgammaRIIIA and trigger Ab-dependent cell-mediated cytotoxicity. Conversely, we also generated upper hinge mutants exhibiting an increase in C1q binding and complement-dependent cytotoxicity activity. Therefore, this approach represents a novel strategy to fine-tune the biological activity of a given human IgG1. We also define, for the first time in such a systematic fashion, the relationship between various characteristics of the middle and upper hinge and the corresponding effector functions.
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Affiliation(s)
- William F Dall'Acqua
- Department of Antibody Discovery and Protein Engineering, MedImmune, One MedImmune Way, Gaithersburg, MD 20878, USA.
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217
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Tsuchihashi SI, Fondevila C, Shaw GD, Lorenz M, Marquette K, Benard S, Shen XD, Ke B, Busuttil RW, Kupiec-Weglinski JW. Molecular characterization of rat leukocyte P-selectin glycoprotein ligand-1 and effect of its blockade: protection from ischemia-reperfusion injury in liver transplantation. THE JOURNAL OF IMMUNOLOGY 2006; 176:616-24. [PMID: 16365457 DOI: 10.4049/jimmunol.176.1.616] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
P-selectin glycoprotein ligand-1 (PSGL-1) mediates the initial tethering of leukocytes to activated platelets and endothelium. We report molecular cloning and characterization of the rat PSGL-1 gene. A neutralizing Ab was generated, and its binding epitope was mapped to the N-terminal binding region of rat PSGL-1. We examined the effects of early PSGL-1 blockade in rat liver models of cold ischemia, followed by ex vivo reperfusion or transplantation (orthotopic liver transplantation (OLT)) using an anti-PSGL-1 Ab with diminished Fc-mediated effector function. In the ex vivo hepatic cold ischemia and reperfusion model, pretreatment with anti-PSGL-1 Ab improved portal venous flow, increased bile production, and decreased hepatocellular damage. Rat pretreatment with anti-PSGL-1 Ab prevented hepatic insult in a model of cold ischemia, followed by OLT, as assessed by 1) decreased hepatocellular damage (serum glutamic oxaloacetic transaminase/glutamic-pyruvic transaminase levels), and ameliorated histological features of ischemia/reperfusion injury, consistent with extended OLT survival; 2) reduced intrahepatic leukocyte infiltration, as evidenced by decreased expression of P-selectin, ED-1, CD3, and OX-62 cells; 3) inhibited expression of proinflammatory cytokine genes (TNF-alpha, IL-1beta, IL-6, IFN-gamma, and IL-2); and 4) prevented hepatic apoptosis accompanied by up-regulation of antiapoptotic Bcl-2/Bcl-xL protective genes. Thus, targeting PSGL-1 with a blocking Ab that has diminished Fc-mediated effector function is a simple and effective strategy that provides the rationale for novel therapeutic approaches to maximize the organ donor pool through the safer use of liver transplants despite prolonged periods of cold ischemia.
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Affiliation(s)
- Sei-ichiro Tsuchihashi
- Dumont-University of California Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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218
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Hinton PR, Xiong JM, Johlfs MG, Tang MT, Keller S, Tsurushita N. An engineered human IgG1 antibody with longer serum half-life. THE JOURNAL OF IMMUNOLOGY 2006; 176:346-56. [PMID: 16365427 DOI: 10.4049/jimmunol.176.1.346] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The serum half-life of IgG Abs is regulated by the neonatal Fc receptor (FcRn). By binding to FcRn in endosomes, IgG Abs are salvaged from lysosomal degradation and recycled to the circulation. Several studies have demonstrated a correlation between the binding affinity of IgG Abs to FcRn and their serum half-lives in mice, including engineered Ab fragments with longer serum half-lives. Our recent study extended this correlation to human IgG2 Ab variants in primates. In the current study, several human IgG1 mutants with increased binding affinity to human FcRn at pH 6.0 were generated that retained pH-dependent release. A pharmacokinetics study in rhesus monkeys of one of the IgG1 variants indicated that its serum half-life was approximately 2.5-fold longer than the wild-type Ab. Ag binding was unaffected by the Fc mutations, while several effector functions appeared to be minimally altered. These properties suggest that engineered Abs with longer serum half-lives may prove to be effective therapeutics in humans.
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219
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Wang HW, Cole D, Jiang WZ, Jin HT, Fu N, Chen ZL, Jin NY. Engineering and functional evaluation of a single-chain antibody against HIV-1 external glycoprotein gp120. Clin Exp Immunol 2005; 141:72-80. [PMID: 15958072 PMCID: PMC1809408 DOI: 10.1111/j.1365-2249.2005.02826.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The HIV-1 envelope glycoprotein surface subunit gp120 is an attractive target for molecular intervention. This is because anti-HIV-1 gp120 neutralizing antibodies display the potential ability to inhibit HIV-1 infection. The present investigation describes the construction of a genetically engineered single chain antibody (scFv102) against HIV-1 gp120, its expression and functional evaluation. The parental hybridoma cell line (102) produces an immunoglobulin directed against the conserved CD4-binding region of gp120. cDNAs encoding the variable regions of the heavy (V(H)) and light (V(L)) chains were prepared by reverse transcription PCR and linked together with an oligonucleotide encoding a linker peptide (Gly(4)Ser)(3) to produce a single chain antibody gene. The resulting DNA construct was cloned into a prokaryotic expression vector (pET28) and recombinant scFv102 was expressed in Eserichia coli as an insoluble protein. The denatured scFv102 was refolded and purified by immobilized metal ion affinity chromatography. Purified scFv102 had the same specificity as the intact IgG in immuno-blotting assays and immuno-fluorescence (IF) detection, but ELISA analyses demonstrated the affinity of scFv102 to be 5-fold lower than that of the parental monoclonal antibody. In neutralization assays, scFv102 at concentrations lower than 40 microg/ml exhibited efficient interference with viral replication and inhibition of viral infection (90%) across a range of primary isolates of subtype B HIV-1. These results suggest that the constructed anti-HIV-1 gp120 scFv102 has good biological activity and can potentially be used for in vitro diagnostic and in vivo therapeutic applications.
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Affiliation(s)
- H W Wang
- Department of Immunology, Southern Medical University, Guangzhou, 510515, PR China
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220
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Gaboriaud C, Thielens NM, Gregory LA, Rossi V, Fontecilla-Camps JC, Arlaud GJ. Structure and activation of the C1 complex of complement: unraveling the puzzle. Trends Immunol 2004; 25:368-73. [PMID: 15207504 DOI: 10.1016/j.it.2004.04.008] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Christine Gaboriaud
- Laboratoire de Cristallographie et Cristallogénèse des Protéines, Institut de Biologie Structurale Jean Pierre Ebel, CEA-CNRS-Université Joseph Fourier, 41, rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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221
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Jegerlehner A, Schmitz N, Storni T, Bachmann MF. Influenza A vaccine based on the extracellular domain of M2: weak protection mediated via antibody-dependent NK cell activity. THE JOURNAL OF IMMUNOLOGY 2004; 172:5598-605. [PMID: 15100303 DOI: 10.4049/jimmunol.172.9.5598] [Citation(s) in RCA: 321] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Vaccination of mice with a peptide corresponding to the extracellular part of M2 protein coupled to the immunodominant domain of hepatitis B core can protect mice from a lethal challenge with influenza A virus. As the extracellular part of M2 protein is highly conserved in all known human influenza A strains, such a vaccine may protect against all human influenza A strains, which would represent a major advantage over current vaccine strategies. The present study demonstrates that protection is mediated exclusively by Abs, a very important feature of a successful preventive vaccine. However, these Abs neither bind efficiently to the free virus nor neutralize virus infection, but bind to M2 protein expressed on the surface of virus-infected cells. The presence of NK cells is important for protection, whereas complement is not, supposing that protection is mediated via Ab-dependent, cell-mediated cytotoxicity. The absence of neutralizing Abs results in much weaker protection than that achieved by vaccination with UV-inactivated influenza virus. Specifically, whereas neutralizing Abs completely eliminate signs of disease even at high viral challenge doses, M2-specific Abs cannot prevent infection, but merely reduce disease at low challenge doses. M2-specific Abs fail to protect from high challenge doses, as vaccinated mice undergo lethal infection under these conditions. In conclusion, protection mediated by M2-hepatitis B core vaccine would be insufficient during the yearly epidemics, for which full protection is desirable, and overall is clearly inferior to protection achieved by immunization with classical inactivated viral preparations.
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MESH Headings
- Animals
- Antibodies, Viral/biosynthesis
- Antibodies, Viral/metabolism
- Antibodies, Viral/physiology
- Antibody Specificity
- Antibody-Dependent Cell Cytotoxicity/immunology
- Binding Sites, Antibody
- Bronchoalveolar Lavage Fluid/cytology
- Complement C3/deficiency
- Complement C3/genetics
- Extracellular Fluid/immunology
- Extracellular Fluid/virology
- Female
- Hepatitis B virus/immunology
- Immunoglobulin G/biosynthesis
- Immunoglobulin G/classification
- Influenza A virus/immunology
- Influenza A virus/radiation effects
- Influenza Vaccines/administration & dosage
- Influenza Vaccines/immunology
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Killer Cells, Natural/virology
- Lymphocyte Depletion
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Knockout
- Orthomyxoviridae Infections/immunology
- Orthomyxoviridae Infections/prevention & control
- Protein Structure, Tertiary
- T-Lymphocytes/immunology
- Vaccines, Combined/administration & dosage
- Vaccines, Combined/immunology
- Viral Matrix Proteins/administration & dosage
- Viral Matrix Proteins/immunology
- Viral Matrix Proteins/metabolism
- Virus Inactivation/radiation effects
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222
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Tischenko VM, Zav'yalova GA, Bliznyukov OP, Zav'yalov VP. Thermodynamic, conformational and functional properties of the human C1q globular heads in the intact C1q molecule in solution. Mol Immunol 2004; 40:1225-36. [PMID: 15128039 DOI: 10.1016/j.molimm.2003.11.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Thermodynamic. conformational and functional properties of the human C1q globular heads (hgC1q) were studied with the experimental approaches, which allow investigating these properties in the intact hC1q molecule in solution. Surprisingly, the scanning calorimetry data reveal a low level of cooperativity of interactions between the hgC1q A, B and C domains even at a neutral pH area. Ionization of His residues due to acidification of the medium at the pH range from 6 to 5 or the chemical modification of His residues completely abolishes the cooperative interactions between the domains without significant effect on their conformation. The thermodynamic data provide evidence that the hgC1q module is composed of three structurally independent A, B and C globular domains characterized by the practically identical thermal stability and very similar enthalpy of melting. The spectroscopic studies and modification with 2-oxy-5-nitrobenzylbromide (ONBB) indicate that Trp residues in the hgC1q A and C domains are accessible to the solvent that has been confirmed by the hgC1q crystal structure solved and refined to 1.9 A. The modification of Trp residues significantly affects the complement-dependent cytotoxicity without noticeable effect on the hC1q conformation. These data provide evidence that Trp residues are the components of immunoglobulin-binding sites both in the hgC1q A and C domains.
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Affiliation(s)
- V M Tischenko
- The National Center for Biodefense, George Mason University, 10900 University Blvd., MS 4F3 Manassas, VA 20110, USA
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223
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Gaboriaud C, Juanhuix J, Gruez A, Lacroix M, Darnault C, Pignol D, Verger D, Fontecilla-Camps JC, Arlaud GJ. The crystal structure of the globular head of complement protein C1q provides a basis for its versatile recognition properties. J Biol Chem 2003; 278:46974-82. [PMID: 12960167 DOI: 10.1074/jbc.m307764200] [Citation(s) in RCA: 269] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1q is a versatile recognition protein that binds to an amazing variety of immune and non-immune ligands and triggers activation of the classical pathway of complement. The crystal structure of the C1q globular domain responsible for its recognition properties has now been solved and refined to 1.9 A of resolution. The structure reveals a compact, almost spherical heterotrimeric assembly held together mainly by non-polar interactions, with a Ca2+ ion bound at the top. The heterotrimeric assembly of the C1q globular domain appears to be a key factor of the versatile recognition properties of this protein. Plausible three-dimensional models of the C1q globular domain in complex with two of its physiological ligands, C-reactive protein and IgG, are proposed, highlighting two of the possible recognition modes of C1q. The C1q/human IgG1 model suggests a critical role for the hinge region of IgG and for the relative orientation of its Fab domain in C1q binding.
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Affiliation(s)
- Christine Gaboriaud
- Laboratoire de Cristallographie et Cristallogéncse des Protéines, Institut de Biologie Structurale Jean-Pierre Ebel, Commissariat à l'Energie Atomique (CEA)-CNRS-Université Joseph Fourier, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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224
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Nishimura Y, Igarashi T, Haigwood NL, Sadjadpour R, Donau OK, Buckler C, Plishka RJ, Buckler-White A, Martin MA. Transfer of neutralizing IgG to macaques 6 h but not 24 h after SHIV infection confers sterilizing protection: implications for HIV-1 vaccine development. Proc Natl Acad Sci U S A 2003; 100:15131-6. [PMID: 14627745 PMCID: PMC299920 DOI: 10.1073/pnas.2436476100] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Passive transfer of high-titered antiviral neutralizing IgG, known to confer sterilizing immunity in pig-tailed monkeys, has been used to determine how soon after virus exposure neutralizing antibodies (NAbs) must be present to block a simian immunodeficiency virus (SIV)/HIV chimeric virus infection. Sterilizing protection was achieved in three of four macaques receiving neutralizing IgG 6 h after intravenous SIV/HIV chimeric virus inoculation as monitored by PCR analyses of and attempted virus isolations from plasma, peripheral blood mononuclear cell, and lymph node specimens. In the fourth animal, the production of progeny virus was suppressed for >4 weeks. A delay in transferring NAbs until 24 h after virus challenge resulted in infection in two of two monkeys. These results suggest that even if a vaccine capable of eliciting broadly reactive NAbs against primary HIV-1 were at hand, the Abs generated must remain at, or rapidly achieve, high levels within a relatively short period after exposure to virus to prevent the establishment of a primate lentivirus infection.
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Affiliation(s)
- Yoshiaki Nishimura
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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225
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Ferrantelli F, Hofmann-Lehmann R, Rasmussen RA, Wang T, Xu W, Li PL, Montefiori DC, Cavacini LA, Katinger H, Stiegler G, Anderson DC, McClure HM, Ruprecht RM. Post-exposure prophylaxis with human monoclonal antibodies prevented SHIV89.6P infection or disease in neonatal macaques. AIDS 2003; 17:301-9. [PMID: 12556683 DOI: 10.1097/00002030-200302140-00003] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The majority of infants infected through maternal transmission acquire the virus during birth or postpartum through breastfeeding: mucosal exposure is considered to be a major route of infection. OBJECTIVES To develop passive immunization with human neutralizing monoclonal antibodies (mAbs) against mother-to-child transmission of HIV during delivery and through breastfeeding. DESIGN An oral challenge model in newborn rhesus macaques mimicked peri- and postpartum virus transmission. METHODS Neonatal rhesus macaques were challenged orally with the highly pathogenic, chimeric simian-human immunodeficiency virus SHIV89.6P and given post-exposure prophylaxis with a quadruple combination of neutralizing human mAbs, IgG1b12, 2G12, 2F5, and 4E10, directed against conserved epitopes of HIV envelope glycoproteins. Control animals were virus challenged but left untreated. All infants were followed prospectively for signs of viremia and immunodeficiency. RESULTS Two out of four macaque infants treated with neutralizing mAbs showed no evidence of infection; the other two maintained normal CD4 T cell counts. In contrast, all control animals became highly viremic and had profound CD4 T cell losses; three out of four died from AIDS within 1.5-6 weeks of the challenge. CONCLUSIONS Passive immunization with this quadruple neutralizing mAbs combination may represent a promising approach to prevent peri- and postnatal HIV transmission. Furthermore, the epitopes recognized by the four neutralizing mAbs are key determinants to achieve complete protection and represent important targets against which to develop active, antibody-response-based AIDS vaccines.
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Affiliation(s)
- Flavia Ferrantelli
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA
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226
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López-Bueno A, Mateu MG, Almendral JM. High mutant frequency in populations of a DNA virus allows evasion from antibody therapy in an immunodeficient host. J Virol 2003; 77:2701-8. [PMID: 12552010 PMCID: PMC141124 DOI: 10.1128/jvi.77.4.2701-2708.2003] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The degree of genetic heterogeneity of DNA virus populations in nature and its consequences for disease control are virtually unknown. The parvovirus minute virus of mice (MVMi) was used here to investigate (i) the frequency of antibody-escape mutants in populations of a DNA virus and (ii) the ability of a DNA virus to evade in the long-term a passive monoclonal antibody (MAb) therapy in an immunodeficient natural host. Independent clonal populations of MVMi harbored a high proportion of mutants resistant to neutralizing MAb (mutant frequency = [2.8 +/- 0.5] x 10(-5)) that rapidly evolved under antibody pressure in culture to become mixtures dominated by genotypically diverse escape mutants. Immunodeficient mice naturally infected with clonal populations of MVMi and subsequently treated by intravenous injections of MAb were initially protected from the characteristic viral induced lethal leukopenia. However, some treated animals developed a delayed severe leukopenic syndrome associated with the emergence of genetically heterogeneous populations of MAb-resistant mutants in the MVMi main target organs. The 11 plaque-purified viruses analyzed from an antibody-resistant population obtained from one animal corresponded to four different mutant genotypes, although their consensus sequence remained wild type. All cloned escape mutants harbored single radical amino acid changes within a stretch of seven residues in a surface-exposed loop at the threefold axes of the capsid. This antigenic site, which can tolerate radical changes preserving MVMi pathogenic potential, may thereby allow the virus to evade the immune control. These findings indicate a high genetic heterogeneity and rapid adaptation of populations of a mammal DNA virus in vivo and provide a genetic basis for the failure of passive immunotherapy in the natural host.
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Affiliation(s)
- Alberto López-Bueno
- Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Cantoblanco, 28049 Madrid, Spain
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227
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Villinger F, Mayne AE, Bostik P, Mori K, Jensen PE, Ahmed R, Ansari AA. Evidence for antibody-mediated enhancement of simian immunodeficiency virus (SIV) Gag antigen processing and cross presentation in SIV-infected rhesus macaques. J Virol 2003; 77:10-24. [PMID: 12477806 PMCID: PMC140624 DOI: 10.1128/jvi.77.1.10-24.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2002] [Accepted: 09/30/2002] [Indexed: 01/31/2023] Open
Abstract
By using the dominant simian immunodeficiency virus (SIV) Gag Mamu-A01 restricted major histocompatibility complex (MHC) class I epitope p11CM, we demonstrate antibody-mediated enhanced MHC class I cross presentation of SIV Gag. In vitro restimulation of peripheral blood mononuclear cells from SIV-infected rhesus macaques with recombinant full-length SIV Gag p55 plus p55 affinity-purified immunoglobulin G (p55 Gag/p55-IgG) led to the generation of markedly higher frequencies of p11CM specific precursor cytotoxic T lymphocytes (p-CTLs) compared with restimulation with (i) SIV Gag p55 alone or (ii) optimal concentrations of the p11CM peptide alone. These results, along with the finding that CD4 depletion abrogated the enhancement, suggest a prominent role for CD4(+) T cells. Testing for p-CTLs against other Mamu-A01-restricted SIV Gag epitopes suggested that this mechanism favored recognition of the dominant p11CM peptide, potentially further skewing of the CTL response. The p-CTL enhancing effect was also decreased or abrogated by pepsin digestion of the p55-specific IgG or by the addition of monoclonal antibodies to Fc receptor (FcR) II/III, suggesting that the effect was dependent on FcR-mediated uptake of the immune-complexed antigen. Finally, incubation of antigen-presenting cells with SIV Gag p55 immune complexes in the presence of lactacystin or of bafilomycin indicated that the mechanism of antibody-mediated enhancement of cross presentation required both the proteasomal and the endosomal pathways. These data demonstrate for the first time the cross presentation of antigens via immune complexes in lentiviral infection and indicate a heretofore-unrecognized role for antibodies in modulating the magnitude and potentially also the breadth of MHC class I-restricted antigen processing and presentation and CTL responses.
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Affiliation(s)
- Francois Villinger
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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228
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Abstract
Neutralizing antibodies are crucial for vaccine-mediated protection against viral diseases. They probably act, in most cases, by blunting the infection, which is then resolved by cellular immunity. The protective effects of neutralizing antibodies can be achieved not only by neutralization of free virus particles, but also by several activities directed against infected cells. In certain instances, non-neutralizing antibodies contribute to protection. Several viruses, such as HIV, have evolved mechanisms to evade neutralizing-antibody responses, and these viruses present special challenges for vaccine design that are now being tackled.
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Affiliation(s)
- Dennis R Burton
- Department of Immunology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
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229
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Abstract
The past few months have seen encouraging successes for neutralizing antibodies against HIV; human monoclonal antibodies targeting conserved HIV envelope epitopes potently neutralized primary virus isolates, including strains of different clades. In primates, passive immunization with combinations containing human monoclonal antibodies completely prevented infection, even after mucosal virus challenges. Epitopes recognized by the protective monoclonal antibodies are important determinants for protection and provide a rational basis for AIDS vaccine development.
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Affiliation(s)
- Flavia Ferrantelli
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute and Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
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