Histidine 375 Modulates CD4 Binding in HIV-1 CRF01_AE Envelope Glycoproteins

Abstract

The envelope glycoproteins (Envs) from human immunodeficiency virus type 1 (HIV-1) mediate viral entry. The binding of the HIV-1 gp120 glycoprotein to CD4 triggers conformational changes in gp120 that allow high-affinity binding to its coreceptors. In contrast to all other Envs from the same phylogenetic group, M, which possess a serine (S) at position 375, those from CRF01_AE strains possess a histidine (H) at this location. This residue is part of the Phe43 cavity, where residue 43 of CD4 (a phenylalanine) engages with gp120. Here we evaluated the functional consequences of replacing this residue in two CRF01_AE Envs (CM244 and 92TH023) by a serine. We observed that reversion of amino acid 375 to a serine (H375S) resulted in a loss of functionality of both CRF01_AE Envs as measured by a dramatic loss in infectivity and ability to mediate cell-to-cell fusion. While no effects on processing or trimer stability of these variants were observed, decreased functionality could be linked to a major defect in CD4 binding induced by the replacement of H375 by a serine. Importantly, mutations of residues 61 (layer 1), 105 and 108 (layer 2), and 474 to 476 (layer 3) of the CRF01_AE gp120 inner domain layers to the consensus residues present in group M restored CD4 binding and wild-type levels of infectivity and cell-to-cell fusion. These results suggest a functional coevolution between the Phe43 cavity and the gp120 inner domain layers. Altogether, our observations describe the functional importance of amino acid 375H in CRF01_AE envelopes.IMPORTANCE A highly conserved serine located at position 375 in group M is replaced by a histidine in CRF01_AE Envs. Here we show that H375 is required for efficient CRF01_AE Env binding to CD4. Moreover, this work suggests that specific residues of the gp120 inner domain layers have coevolved with H375 in order to maintain its ability to mediate viral entry.

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

“…CRF01_AE HIV-1 isolates have a highly conserved histidine residue at Env position 375 (Fig. 1E), which was recently shown to be important for CD4 interaction (27) but also to confer strong resistance to the BMS-599793 entry inhibitor (36). To evaluate whether His 375 influences the recognition of infected cells by ADCC-mediating antibodies and HIV ϩ sera, His 375 in the CRF01_AE 703357 strain was replaced by a serine (H375S).…”

“…In order to achieve the same level of infection among the different mutants tested, vesicular stomatitis virus G (VSVG)-pseudotyped HIV-1 clones were produced, as previously described (14). This was necessary since mutations at residue 375 were shown to affect CD4 binding and infectivity in CRF01_AE strains (27). Briefly, proviral vectors and a VSVG-encoding plasmid were cotransfected into 293T cells by standard calcium phosphate transfection.…”

“…While Ser 375 is well conserved in the majority of group M HIV-1 isolates, we noticed that CRF01_AE Env possess a Phe 43 cavity-filling residue at position 375 (His 375) (27). CRF01_AE is the predominant circulating strain in Thailand, where the RV144 clinical vaccine trial took place.…”

HIV-1 subtype CRF01_AE and B differ in utilization of low levels of CCR5, Maraviroc susceptibility and potential N-glycosylation sites

“…Recently, Zoubchenok et al analyzed residues in AE Envs important for CD4 binding (Zoubchenok et al, 2017) especially at position 375 and its interaction with other residues in the gp120 inner domain layers as HIV evolved. They determined that AE strains possess a Histidine at position 375 instead of the highly conserved Serine in group M. This His375 residue is part of the Phe43 cavity where Phe at position 43 in CD4 engages with gp120 and is required for efficient AE Env binding to CD4.…”

“…Recently, Zoubchenok et al analyzed residues in CRF01_AE Envs important for CD4 binding (Zoubchenok et al, 2016) and identified Histidine 375 as a critical residue in the process. Overall, our data concur with findings of Zoubchenok et al except for the lower prevalence of His at position 105 which is likely a bias caused by small sample size.…”