107 Escape from Neutralizing Antibody in Early Subtype C HIV-1 Infection

Abstract

HIV-1 subtype C viruses circulate predominantly in India and sub-Saharan Africa, accounting for most global infections. We previously demonstrated that 9 out of 11 subtype C infected seroconvertors followed in a Zambian cohort rapidly developed high titer autologous neutralizing antibody (Nab) against the infecting virus. Here we characterized the Nab sensitivity of individual envelope (Env) glycoproteins that evolved during early infection in four of these seroconvertors. Env genes were PCR amplified from longitudinal patient PBMC DNA and plasma samples using single genome analysis, cloned into an expression vector, and screened for biological function using a pseudovirus assay. Neutralization sensitivity of each Env pseudovirus was evaluated against autologous plasma from longitudinal time points to identify variants that had escaped from contemporaneous Nab. The molecular mechanism of Nab escape was then investigated in detail in two subjects by replacing Env domains of the initial, Nab sensitive virus with those derived from 6 to 10 escape variants from the same patient. The monophyletic founder virus in the newly infected subjects was rapidly replaced by a succession of variants that were resistant to contemporaneous Nab but were subsequently neutralized by a de novo antibody response. In one patient, the virus used multiple escape mechanisms, even at a single time point. One of these escape pathways required sequence changes in both gp120 and the gp41 ectodomain, while another involved only the V3-V5 region of gp120. The V1V2 domain, however, did not contribute to neutralization escape in this subject. In contrast, in the second patient, the V1V2 domain played a major role in resistance in every Env analyzed. The changes in V1V2 conferred early and complete resistance against a monoclonal antibody isolated from the PBMC of this patient four years later, but changes outside of V1V2 were required to escape from the polyclonal antibody response. Our data demonstrate that subtype C viruses use multiple mechanisms to escape from potent autologous Nab, even within a single patient. These findings highlight the need to define and understand potential escape mechanisms in strategies to induce protective Nab.