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Immunology Core: Binding Antibody Component
Antigen specific antibody responses using customizable antigen-specific binding assays are provided by the CFAR Immunology core under GCLP-compliant conditions. These assays can be used to profile global changes in isotype and subclass responses to infection or vaccination. HIV, TB, HCV, and SIV specific assays are currently available. Antibody assays include a binding antibody multiplex assay (BAMA), avidity index assay (BAMA-AI) and antibody peptide microarray, virion capture and phagocytosis. The Binding Antibody Multiplex Assay (BAMA) has multiplex capability to profile antibody isotypes and subclasses (IgG1-4, dIgA, SCIgA, IgA1-2, IgM) for multiple antigens simultaneously (e.g. 50-100 different proteins/epitopes). Avidity index is also a multiplex assay that can be used to profile the strength of these antigen- antibody interaction using specific peptides and a sodium-citrate step. Total, nonspecific antibodies, are also measured in mucosal samples (cervical/vaginal, rectal, saliva, etc). A peptide microarray assay determines the precise epitope mapping across clades using minimum specimen volume. Peptide microarrays are available for HIV and SIV antigens (with potential for TB epitopes). HIV virion capture assays can distinguish the capacity of different antibody specificities to recognize infectious and noninfectious virus particles. HIV-1 phagocytosis assays are employed to test the ability of vaccine or infection induced antibodies to engage FcR on primary monocyte/macrophages in addition to recognition of virus particles.
Binding Antibody Multiplex Assay (BAMA)
- Multiplex capability (µl sample volume, > 50 antigens /sample)
- HIV-1, SIV, TB antigens
- Subclass profiling (IgG, IgG1-4, IgA1-2, dIgA, SIgA, IgM)
- Mucosal Samples (antigen specific and total Ig)
Peptide Microarray (HIV-1 and SIV)
- HIV-1 cross-clade epitope mapping (Clades A, B, C,D, M; Thai and Clade C Vaccine strains)
- SIV (mac239, smE660)
- IgG, IgG3, IgA
- Multiplex (>1900 peptides/sample; µl sample volume)
- Plasma/Serum and Mucosal Samples
HIV-1 Virion Capture
- Cross-clade Viruses
- mAbs, Plasma, Mucosal (IgG, IgA)
- Infectious vs. Noninfectious particle capture
- Paired BAMA profiling
- Antigen coupled beads, Infectious Virions
- IgG, IgG3, IgA (mAbs, purified Ig from plasma/mucosa)
- Primary monocyte/macrophages/ THP-1 Cells
Antibody Immune Correlates. Effective implementation of an efficacious HIV-1 vaccine is an important goal put forth by the leaders of the National Institutes of Health to achieve an AIDS free generation. Global efforts toward an HIV-1 vaccine have been complicated by a history of vaccine research that has lacked biomarkers of vaccine efficacy. Together, we have identified IgA, IgG, and IgG3 biomarkers of HIV-1 infection risk that along with evaluating antibody function can be instrumental in benchmarking HIV-1 clinical trials. We determined that specific Env Plasma IgA (BAMA breadth) was a primary HIV-1 Correlate of Risk in RV144. Through a peptide microarray analysis, we (C1) identified a specific region in the HIV-1 Envelope as an HIV-1 Correlate of Risk (OR 3.15, p <0.003) in the secondary analysis. In a follow-up study, we identified that Env IgA/IgG ratio correlated with Risk in RV144 and that envelope IgA could inhibit Env IgG ADCC function. We also validated the BAMA approach for determination of the V1-V2 correlate of risk in RV144 and identified antibody subclasses (i.e. IgG3) as a key in distinguishing among vaccine candidates. Thus, IgG3 responses mark a qualitative difference in immune response between two vaccine regimens with divergent efficacy outcomes. Moreover, these findings revealed HIV-1 Env-specific IgG3 antibodies as a biomarker for evaluating HIV-1 vaccines. In concert, many of the diverse antibody immune measurements measured as part of this CFAR Immunology Core can be utilized to benchmark both preclinical and clinical vaccine studies.
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