Envelope residue 375 substitutions in simian–human immunodeficiency viruses enhance CD4 binding and replication in rhesus macaques

Abstract

Most simian–human immunodeficiency viruses (SHIVs) bearing envelope (Env) glycoproteins from primary HIV-1 strains fail to infect rhesus macaques (RMs). We hypothesized that inefficient Env binding to rhesus CD4 (rhCD4) limits virus entry and replication and could be enhanced by substituting naturally occurring simian immunodeficiency virus Env residues at position 375, which resides at a critical location in the CD4-binding pocket and is under strong positive evolutionary pressure across the broad spectrum of primate lentiviruses. SHIVs containing primary or transmitted/founder HIV-1 subtype A, B, C, or D Envs with genotypic variants at residue 375 were constructed and analyzed in vitro and in vivo. Bulky hydrophobic or basic amino acids substituted for serine-375 enhanced Env affinity for rhCD4, virus entry into cells bearing rhCD4, and virus replication in primary rhCD4 T cells without appreciably affecting antigenicity or antibody-mediated neutralization sensitivity. Twenty-four RMs inoculated with subtype A, B, C, or D SHIVs all became productively infected with different Env375 variants—S, M, Y, H, W, or F—that were differentially selected in different Env backbones. Notably, SHIVs replicated persistently at titers comparable to HIV-1 in humans and elicited autologous neutralizing antibody responses typical of HIV-1. Seven animals succumbed to AIDS. These findings identify Env–rhCD4 binding as a critical determinant for productive SHIV infection in RMs and validate a novel and generalizable strategy for constructing SHIVs with Env glycoproteins of interest, including those that in humans elicit broadly neutralizing antibodies or bind particular Ig germ-line B-cell receptors.

Influence of the Envelope gp120 Phe 43 Cavity on HIV-1 Sensitivity to Antibody-Dependent Cell-Mediated Cytotoxicity Responses

“…The replacement of the well-conserved group M serine at position 375 by a large hydrophobic residue such as tryptophan fills the Phe 43 cavity; this substitution alters the Env conformation by predisposing gp120 to spontaneously assume a state closer to the CD4-bound conformation (9). In agreement with the important role played by Env conformation in the CD4 interaction (1, 9-11), a recent study using the simian-human immunodeficiency virus (SHIV) model in rhesus macaques showed that the replacement of residue 375 by larger hydrophobic or basic amino acids enhanced the affinity of Env for macaque CD4 and allowed better infection of macaque T lymphocytes in culture and in vivo (12), highlighting the importance of this residue for viral replication.…”

“…Individual Env mutations were introduced in the previously described pNL43-ADA(Env)-GFP.IRES.Nef proviral vector (14) by using the QuikChange II XL site-directed mutagenesis protocol (Stratagene). The plasmids encoding SHIV clade C strain CH505, SHIV clade D strain 191859, and their variants were previously described (12). The sequence of HIV-1 CRF01_AE transmitted-founder (T/F) clone 703357 was derived by using a single-genome amplification (SGA) strategy.…”

“…Additional work is needed to assess the evolutionary selective pressures that resulted in the fixation of a histidine residue at position 375 in this rapidly spreading viral strain. Substitutions of large residues like histidine at this position have been shown to result in SHIVs that bind rhesus macaque CD4 and replicate in monkeys more efficiently (12). Apparently, the advantages of the S375W change in specific hosts (rhesus monkeys and some southern Chinese and Thai individuals) outweigh negative consequences such as enhanced susceptibility of HIV-1-infected cells to ADCC responses.…”

Simian Immunodeficiency Virus SIVmac239, but Not SIVmac316, Binds and Utilizes Human CD4 More Efficiently than Rhesus CD4

“…These chimeric viruses include the HIV-1 env and vpu genes and were developed to study the properties of HIV-1 envelope glycoprotein (Env) in the macaque model. Only a subset of SHIVs replicate efficiently in macaques, a consequence in part of the inefficiency with which most HIV-1 Envs utilize rhesus CD4 (12,13). An isoleucine at rhesus CD4 residue 39 has been identified as a major determinant of this inefficiency (13).…”

Polyvalent vaccine approaches to combat HIV‐1 diversity

“…In practice, when tested in NHP models, HIV‐1 mosaic vaccines significantly improved both the number and potency of vaccine‐elicited T‐cell responses that cross‐reacted with natural variants 36, 37, 38, 39. While the level of vaccine responses to HIV‐1 proteins can be evaluated in NHPs, their protective capacity cannot be assessed, except for responses to the HIV‐1 Env glycoprotein, which can be tested using simian‐human immunodeficiency virus (SHIV) challenge models 40. Using SIVmac proteins instead, the number of vaccine‐elicited SIVmac Gag CTL responses has been correlated with improved viral control in NHPs of SHIVs and SIVmac 41, 42.…”