Virological Control by the CD4-Binding Site Antibody N6 in Simian-Human Immunodeficiency Virus-Infected Rhesus Monkeys

Abstract

Passive immunotherapy against HIV-1 will most likely require broadly neutralizing antibodies (bnAbs) with maximum breadth and potency to ensure therapeutic efficacy. Recently, the novel CD4 binding site antibody N6 demonstrated extraordinary neutralization breadth and potency against large panels of cross-clade pseudoviruses. We evaluated the in vivo antiviral activity of N6-LS, alone or in combination with the established V3-glycan antibody PGT121, in chronically simianhuman immunodeficiency virus (SHIV)-SF162P3-infected macaques. A single dose of N6-LS suppressed plasma viral loads in 4 out of 5 animals at day 7, while the combination of both antibodies suppressed all animals. The combination of both antibodies had no additive antiviral effect compared to a single dose of PGT121, potentially reflecting the nearly 10-fold-higher potency of PGT121 against this SHIV. Viral rebound occurred in the majority of suppressed animals and was linked to declining plasma bnAb levels over time. In addition to the effect on plasma viremia, bnAb administration resulted in significantly reduced proviral DNA levels in PBMCs after 2 weeks and in lymph nodes after 10 weeks. Autologous neutralizing antibody (nAb) responses and CD8 ϩ T-cell responses were not significantly enhanced in the bnAbtreated animals compared to control animals, arguing against their contribution to the viral effects observed. These results confirm the robust antiviral activity of N6-LS in vivo, supporting the further clinical development of this antibody.IMPORTANCE Monocloncal antibodies (MAbs) are being considered for passive immunotherapy of HIV-1 infection. A critical requirement for such strategies is the identification of MAbs that recognize the diversity of variants within circulating but also reservoir viruses, and MAb combinations might be needed to achieve this goal. This study evaluates the novel bnAb N6-LS alone or in combination with the bnAb PGT121, in rhesus macaques that were chronically infected with SHIV. The results demonstrate that N6-LS potently suppressed plasma viral loads in the majority of animals but that the combination with PGT121 was not superior to PGT121 alone in delaying time to viral rebound or reducing peripheral blood mononuclear cell (PBMC) or lymph node proviral DNA levels. The occurrence of viral escape variants in an N6-LS-monotreated animal, however, argues for the need to maximize breadth and antiviral efficacy by combining bnAbs for therapeutic indications.

Restriction of HIV-1 Escape by a Highly Broad and Potent Neutralizing Antibody

“…Similarly, removal of a PNGS adjacent to the CD4bs (N276 gp120 ) reduced sensitivity to the gp120-gp41 interface bNAb 8ANC195 (Scharf et al, 2014) but had no effect on 1-18 ( Figure 4). V H -restricted CD4bs bNAbs typically interact with loop D residues N279 gp120 and/or N280 gp120 , and changes in these residues have been associated with viral rebound from CD4bs therapy (Diskin et al, 2013;Horwitz et al, 2013;Julg et al, 2017;Klein et al, 2012;Lynch et al, 2015a). When we tested HIV-1 YU2 variants with mutations at these residues, we observed reduced or abrogated sensitivity to VRC01-class bNAbs and to the V H 1-46-derived CD4bs bNAb 8ANC131 (Figure 4).…”

Broadly resistant HIV-1 against CD4-binding site neutralizing antibodies

“…For example,nearly all HIV-1 variants found in recent plasma samples from the original VRC01 donor are now resistant to VRC01 [42], as are the VRC01-resistant strains we previously identified in a chronically infected patient [39][40][41].Similar to what we found in the current study, the mutations responsible for such resistance are also confined to the area between residues 278 and 283 of Loop D, and to potential N-linked glycosylation sites between residues 458 and 467 of the β23/loop V5/β24 region. Analyses of rebound viruses in humanized mice or rhesus macaque models after antibody monotherapy with 3BNC117 and N6 also revealed mutations between 279-281 of loop D, and between 458-459 of the β23/loop V5/β24 region [44,45] In particular,human monotherapy trials with the 3BNC117 and VRC01 antibodies revealed significant polymorphisms. A shift in HIV-1 plasma RNA populations was found at the abovementioned positions ( Fig 6).…”

“…Despite the superior potency and breadth of these CD4bs bnAbs, each fails to neutralize a small but significant portion of pseudotyped virus panels [17,25,27,28,37,38].For instance, VRC01 is unable to neutralize about 10% of tested viruses [25], and resistant strains have been isolated from patients infected with subtype B, subtype C, CRF07_BC, and CRF08_BC [29,[39][40][41][42]. Furthermore, reports show thatVRC01-, 3BNC117-and N6-resistant strains have emerged in both animal models and human clinical trials [11,15,[43][44][45][46][47], indicating that resistant virus Broadly resistant HIV-1 against CD4bs antibodies PLOS Pathogens | https://doi.org/10.…”

“…Structurally, these bnAbs recognize residues within the inner domain, the Loop D, the CD4 binding loop, and the β23/loop V5/β24 region [17,18,[29][30][31].The V1V2 and V3 loop also impact recognition,particularly in the context of the quaternary trimeric envelope protein [32][33][34][35][36].The primary mechanism of neutralization mimics and competes with the CD4 receptorto bind HIV-1 gp120, thereby preventing bound trimers from transitioning to the subsequent steps required for membrane fusion, although evidence indicates that there are differences in the fine details of this process [17,18,35,36].Despite the superior potency and breadth of these CD4bs bnAbs, each fails to neutralize a small but significant portion of pseudotyped virus panels [17,25,27,28,37,38].For instance, VRC01 is unable to neutralize about 10% of tested viruses [25], and resistant strains have been isolated from patients infected with subtype B, subtype C, CRF07_BC, and CRF08_BC [29,[39][40][41][42]. Furthermore, reports show thatVRC01-, 3BNC117-and N6-resistant strains have emerged in both animal models and human clinical trials [11,15,[43][44][45][46][47], indicating that resistant virus Broadly resistant HIV-1 against CD4bs antibodies PLOS Pathogens | https://doi.org/10.…”

Predicting the broadly neutralizing antibody susceptibility of the HIV reservoir

“…The recent identification of highly potent and broadly neutralizing antibodies (bNAbs) against HIV-1 has led to a renaissance of antibodies as therapeutic and prophylactic tools. Initial preclinical and clinical studies with passive administration of bNAbs have shown great promise that these monoclonals could play a revolutionary role in HIV care (3)(4)(5)(6)(7)(8)(9). While these antibodies are able to temporarily reduce plasma viral loads in viremic HIV-1-infected individuals (3,5,10) or delay viral rebound once ART is stopped, recent studies showed that neutralization-resistant viral strains were often selected to emerge, ultimately resulting in virological failure of bNAb treatment (11)(12)(13).…”