Phagocytosis by an HIV antibody is associated with reduced viremia irrespective of enhanced complement lysis

Abstract

Increasingly, antibodies are being used to treat and prevent viral infections. In the context of HIV, efficacy is primarily attributed to dose-dependent neutralization potency and to a lesser extent Fc-mediated effector functions. It remains unclear whether augmenting effector functions of broadly neutralizing antibodies (bNAbs) may improve their clinical potential. Here, we use bNAb 10E8v4 targeting the membrane external proximal region (MPER) to examine the role of antibody-mediated effector and complement (C’) activity when administered prophylactically against SHIV challenge in rhesus macaques. With sub-protective dosing, we find a 78–88% reduction in post-acute viremia that is associated with 10E8v4-mediated phagocytosis acting at the time of challenge. Neither plasma nor tissue viremic outcomes in vivo is improved with an Fc-modified variant of 10E8v4 enhanced for C’ functions as determined in vitro. These results suggest that effector functions inherent to unmodified 10E8v4 contribute to efficacy against SHIVSF162P3 in the absence of plasma neutralizing titers, while C’ functions are dispensable in this setting, informing design of bNAb modifications for improving protective efficacy.

Beyond neutralization: Fc-dependent antibody effector functions in SARS-CoV-2 infection

“…C3 deposition on beads can then be assessed as a measure of median fluorescence intensity 182 Virus-based assays Virions are incubated with complement, resulting in viral membrane disruption. Viral proteins are conjugated to streptavidin-coated beads and fluorescence intensity is determined by flow cytometry 183 Live/dead staining Antigen-expressing target cells are incubated with serum and cells are stained with a viability marker to assess membrane integrity. Flow cytometry is used to measure the magnitude of cell killing 183 Antibody-dependent cell-mediated virus inhibition ELISA Infected target cells are incubated with antibodies and effector cells.…”

“…Viral proteins are conjugated to streptavidin-coated beads and fluorescence intensity is determined by flow cytometry 183 Live/dead staining Antigen-expressing target cells are incubated with serum and cells are stained with a viability marker to assess membrane integrity. Flow cytometry is used to measure the magnitude of cell killing 183 Antibody-dependent cell-mediated virus inhibition ELISA Infected target cells are incubated with antibodies and effector cells. An ELISA is performed on the supernatant to measure viral antigen 174 , 184 ADCC, antibody-dependent cellular cytotoxicity; ADCD, antibody-dependent complement deposition; ADCP, antibody-dependent cellular phagocytosis; CCL4, CC-chemokine ligand 4; CFSE, carboxyfluorescein succinimidyl ester; 51 Cr, chromium-51; ELISA, enzyme-linked immunosorbent assay; FACS, fluorescence-activated cell sorting; Fc, crystallizable fragment; FcR, Fc receptor; IFNγ, interferon-γ; PKH-26, Paul Karl Horan 26.…”

Early intervention with 3BNC117 and romidepsin at antiretroviral treatment initiation in people with HIV-1: a phase 1b/2a, randomized trial

“…In addition, in vitro and animal experiments indicate that 3BNC117 can enhance the clearance of HIV-1-infected cells through Fc-mediated effector functions 26,[50][51][52] . While it could be argued that the latter effect might primarily target short-lived productively infected cells and not long-term HIV-1 persistence 27,53 , we were able to demonstrate that 3BNC117 mainly eliminated infected cells in the central memory subset-a subset shown to be the main T cell compartment harboring the latent replication-competent HIV-1 reservoir during long-term ART [54][55][56][57] . Thus, we conclude that potent bNAbs like 3BNC117 can enhance the elimination of cell-free virus and infected cells among individuals initiating ART through biological mechanisms that differ from those of standard antiretroviral drugs.…”

Directing HIV-1 for degradation by non-target cells, using bi-specific single-chain llama antibodies

“…Conventional antibodies bind to HIV through two variable domains and require engagement of the immune system through their constant domains (Fc), before finally the viruses are cleared. This takes time and is most likely the reason that neutralizing antibodies are required 8,63 . EGFR is ubiquitously expressed on many (non-immune) cells in the body.…”