Monoclonal Antibodies Specific for the V2, V3, CD4-Binding Site, and gp41 of HIV-1 Mediate Phagocytosis in a Dose-Dependent Manner

Abstract

In light of the weak or absent neutralizing activity mediated by anti-V2 monoclonal antibodies (MAbs), we tested whether they can mediate Ab-dependent cellular phagocytosis (ADCP), which is an important element of anti-HIV-1 immunity. We tested six anti-V2 MAbs and compared them with 21 MAbs specific for V3, the CD4-binding site (CD4bs), and gp41 derived from chronically HIV-1-infected individuals and produced by hybridoma cells. ADCP activity was measured by flow cytometry using uptake by THP-1 monocytic cells of fluorescent beads coated with gp120, gp41, BG505 SOSIP.664, or BG505 DS-SOSIP.664 complexed with MAbs. The measurement of ADCP activity by the area under the curve showed significantly higher activity of anti-gp41 MAbs than of the members of the three other groups of MAbs tested using beads coated with monomeric gp41 or gp120; anti-V2 MAbs were dominant compared to anti-V3 and anti-CD4bs MAbs against clade C gp120 ZM109 . ADCP activity mediated by V2 and V3 MAbs was positive against stabilized DS-SOSIP.664 trimer but negligible against SOSIP.664 targets, suggesting that a closed envelope conformation better exposes the variable loops. Two IgG3 MAbs against the V2 and V3 regions displayed dominant ADCP activity compared to a panel of IgG1 MAbs. This superior ADCP activity was confirmed when two of three recombinant IgG3 anti-V2 MAbs were compared to their IgG1 counterparts. The study demonstrated dominant ADCP activity of anti-gp41 against monomers but not trimers, with some higher activity of anti-V2 MAbs than of anti-V3 and anti-CD4bs MAbs. The ability to mediate ADCP suggests a mechanism by which anti-HIV-1 envelope Abs can contribute to protective efficacy.IMPORTANCE Anti-V2 antibodies (Abs) correlated with reduced risk of HIV-1 infection in recipients of the RV144 vaccine, suggesting that they play a protective role, but a mechanism providing such protection remains to be determined. The rare and weak neutralizing activities of anti-V2 MAbs prompted us to study Fc-mediated activities. We compared anti-V2 MAbs with other MAbs specific for V3, CD4bs, and gp41 for Ab-dependent cellular phagocytosis (ADCP) activity, implicated in protective immunity. The anti-V2 MAbs displayed stronger activity than other anti-gp120 MAbs in screening against one of two gp120s and against DS-SOSIP, which mimics the native trimer. The activity of anti-gp41 MAbs was superior in targeting monomeric gp41 but was comparable to that seen against trimers, which may not adequately expose gp41 epitopes. While anti-envelope MAbs in general mediated ADCP activity, anti-V2 MAbs displayed some dominance compared to other MAbs. Our demonstration that anti-V2 MAbs mediate ADCP activity suggests a functional mechanism for their contribution to protective efficacy.

Protein S and Gas6 induce efferocytosis of HIV-1-infected cells

“…Gas6/protein S might need to synergize with additional signals for efficient phagocytosis of live HIV-1-infected cells. Because broadly neutralizing antibodies against HIV-1 can provide signals for phagocytosis via the Fcreceptor (Musich et al, 2017), it would be of interest to determine whether the broadly neutralizing antibodies can synergize with Gas6/protein S to clear infected cells by phagocytosis/efferocytosis.…”

Update on Fc-Mediated Antibody Functions Against HIV-1 Beyond Neutralization

“…However, the epitope specificity of Abs mediating ADCP still needs to be investigated. Musich et al demonstrated that anti-V2 monoclonal Abs mediated ADCP activity in a dosedependent manner similar to anti-V3 and CD4bs monoclonal Abs against clade B gp120 (154) but displayed increased activity against clade C gp120 compared to anti-V3 and anti-CD4bs monoclonal Abs, suggesting the broader recognition of exposed epitopes (154); this may also have been due to V2 epitopes being more conserved between clade B and C than V3 epitopes. Moreover, the role played by the cell type that mediates ADCP should also be defined.…”

Phagocytosis of a Model Human Immunodeficiency Virus Target by Human Breast Milk Leukocytes Is Predominantly Granulocyte-Driven When Elicited by Specific Antibody

“…46,47 Monoclonal Abs were only used after they passed all QC assays. 48 Human BM Samples were obtained from healthy lactating women who had signed informed consents. Milk was expressed using double electronic or manual pumps.…”