Antibody Functional Assays as Measures of Fc Receptor-Mediated Immunity to HIV - New Technologies and their Impact on the HIV Vaccine Field.
BACKGROUND
There is now intense interest in the role of HIV-specific antibodies and the engagement of FcγR functions in the control and prevention of HIV infection. The analyses of the RV144 vaccine trial, natural progression cohorts, and macaque models all point to a role for Fc-dependent effector functions, such as cytotoxicity (ADCC) or phagocytosis (ADCP), in the control of HIV. However, reliable assays that can be reproducibly used across different laboratories to measure Fcdependent functions, such as antibody dependent cellular cytotoxicity (ADCC) are limited.


METHODS
This brief review highlights the importance of Fc properties for immunity to HIV, particularly via FcγR diversity and function. We discuss assays used to study FcR mediated functions of HIV-specific Ab, including our recently developed novel cell-free ELISA using homo-dimeric FcγR ectodomains to detect functionally relevant viral antigen-specific antibodies.


RESULTS
The binding of these dimeric FcγR ectodomains, to closely spaced pairs of IgG Fc, mimics the engagement and cross-linking of Fc receptors by IgG opsonized virions or infected cells as the essential prerequisite to the induction of Ab-dependent effector functions. The dimeric FcγR ELISA reliably correlates with ADCC in patient responses to influenza. The assay is amenable to high throughput and could be standardized across laboratories.


CONCLUSIONS
We propose the assay has broader implications for the evaluation of the quality of antibody responses in viral infections and for the rapid evaluation of responses in vaccine development campaigns for HIV and other viral infections.
Centre for Biomedical Research, Burnet Institute, Melbourne, Vic 3004, Australia.|Department of Immunology, Monash University Central Clinical School, Melbourne, Victoria 3004, Australia.|Department of Pathology, The University of Melbourne, Victoria, 3010, Australia.
Bruce D
BD
Wines
Centre for Biomedical Research, Burnet Institute, Melbourne, Vic 3004, Australia.
Hugh
H
Billings
Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Parkville, Victoria, Australia.
Milla R
MR
Mclean
Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Parkville, Victoria, Australia.|ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, The University of Melbourne, Parkville, Victoria, Australia.|Melbourne Sexual Health Centre, Infectious Diseases Department, Alfred Health, Central Clinical School, Monash University, Victoria, Australia.
Stephen J
SJ
Kent
Centre for Biomedical Research, Burnet Institute, Melbourne, Vic 3004, Australia.|Department of Immunology, Monash University Central Clinical School, Melbourne, Victoria 3004, Australia.|Department of Pathology, The University of Melbourne, Victoria, 3010, Australia.
P Mark
PM
Hogarth
D016915:AIDS Vaccines / Q000276:immunology*; D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity; D006678:HIV / Q000276:immunology*; D015483:HIV Antibodies / Q000276:immunology*; D015658:HIV Infections / Q000276:immunology* / Q000517:prevention & control*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D010587:Phagocytosis; D011961:Receptors, Fc / Q000378:metabolism*
D016915:AIDS Vaccines; D015483:HIV Antibodies; D011961:Receptors, Fc
ADCC; ADCP; Fc receptors; HIV; IG; antibodies; natural killer cells; vaccine