Abstract
HIV-1 Envelope (Env) protein is the sole target of neutralizing antibodies (NAbs) that arise during infection to neutralize autologous variants. Under this immune pressure, HIV escape variants are continuously selected and over the course of infection Env becomes more neutralization resistant. Many common alterations are known to affect sensitivity to NAbs, including residues encoding potential N-linked glycosylation sites (PNGS). Knowledge of Env motifs associated with neutralization resistance is valuable for the design of an effective Env-based vaccine so we characterized Envs isolated longitudinally from a SHIVSF162P4 infected macaque for sensitivity to neutralizing monoclonal antibodies (MAbs) B12, 2G12, 4E10 and 2F5. The early Env, isolated from plasma at day 56 after infection, was the most sensitive and the late Env, from day 670, was the most resistant to MAbs. We identified four PNGS in these Envs that accumulated over time at positions 130, 139, 160 and 397. We determined that removal of these PNGS significantly increased neutralization sensitivity to 2G12, and conversely, we identified mutations by in silico analyses that contributed resistance to 2G12 neutralization. In order to expand our understanding of these PNGS, we analyzed Envs from clade B HIV-infected human subjects and identified additional glycan and amino acid changes that could affect neutralization by 2G12 in a context-dependent manner. Taken together, these in vitro and in silico analyses of clade B Envs revealed that 2G12 resistance is achieved by previously unrecognized PNGS substitutions in a context-dependent manner and by subject-specific pathways.
Highlights
The HIV-1 envelope glycoprotein complex (Env) is the sole target of neutralizing antibodies (NAbs) and it evolves rapidly to escape this immune pressure
As previously seen in some HIV-infected human subjects [23], these results show that over the course of infection in macaques, HIV-1 Env evolves to become more resistant to neutralization by monoclonal antibodies (MAbs) that target certain conserved determinants
HIV Envelope evolves under immune pressure and escape mechanisms include increase in variable loop length, introduction of specific amino acid mutations and additions and/or shift of potential N-linked glycosylation sites [43]
Summary
The HIV-1 envelope glycoprotein complex (Env) is the sole target of neutralizing antibodies (NAbs) and it evolves rapidly to escape this immune pressure. NAbs arise during infection to neutralize autologous variants and a limited number of HIV patients develop broad neutralizing antibodies [1,2]. Recent studies identified multiple escape pathways varying from patient to patient and over the course of infection [5,6]. Glycans are attached to the motif: N-X-S/T, (where X can be any amino acid except a proline) that defines Potential N-linked Glycosylation sites (PNGS). Recent studies identified glycans as targets of the very potent PGT monoclonal antibodies (MAbs) [15,16]
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