Recombinant HIV type 1 Glycoprotein 120 [GST]

Objectives: Fostemsavir, a novel attachment inhibitor targeting the HIV-1 gp120, has demonstrated wide in vitro activity. However, the high rate of HIV gp120 substitutions could jeopardize its efficacy. We investigated envelope (env) substitutions at positions associated with resistance to fostemsavir in patients with a new HIV-1 diagnosis according to HIV subtype and tropism. Methods: Gp120 sequences from 409 subjects were retrospectively analysed and the presence of the L116P, A204D, S375H/M/T, M426L, M434I and M475I mutations was evaluated. Other amino acid changes at the same positions were also recorded. The variability at each amino acid position was evaluated using Shannon entropy. Results: The frequency of mutations was: S375T (13.2%); M426L (6.8%); M434I (2.9%); M475I (2.7%); S375H (1.0%)/M (0.8%) and L116P (0.31%). Statistically significant differences were found at positions 375 (R5/non-R5 strains and B/non-B subtypes) and 426 (B/non-B subtypes); post hoc analysis revealed that significance for position 375 was steered by S375T while for position 426 significance was governed by unusual substitutions, in particular M426R (B/non-B, P<0.00001). The variability of env constant domains appeared to be more relevant in the non-B virus population. Conclusions: In conclusion, gp120 substitutions were detected in different subtypes and in both R5 and non-R5 variants. Despite the great variability of gp120, the frequency of mutations was low overall and the predominant substitution was S375T, the role of which in reducing fostemsavir efficacy is less substantial.

Cell entry by HIV-1 is mediated by its principal receptor, CD4, and a coreceptor, either CCR5 or CXCR4, with viral envelope glycoprotein gp120. Generally, CCR5-using HIV-1 variants, called R5, predominate over most of the course of infection, while CXCR4-using HIV-1 variants (variants that utilize both CCR5 and CXCR4 [R5X4, or dual] or CXCR4 alone [X4]) emerge at late-stage infection in half of HIV-1-infected individuals and are associated with disease progression. Although X4 variants also appear during acute-phase infection in some cases, these variants apparently fall to undetectable levels thereafter. In this study, replication-competent X4 variants were isolated from plasma of drug treatment-naive individuals infected with HIV-1 strain CRF01_AE, which dominantly carries viral RNA (vRNA) of R5 variants. Next-generation sequencing (NGS) confirmed that sequences of X4 variants were indeed present in plasma vRNA from these individuals as a minor population. On the other hand, in one individual with a mixed infection in which X4 variants were dominant, only R5 replication-competent variants were isolated from plasma. These results indicate the existence of replication-competent variants with different coreceptor usage as minor populations. IMPORTANCE The coreceptor switch of HIV-1 from R5 to CXCR4-using variants (R5X4 or X4) has been observed in about half of HIV-1-infected individuals at late-stage infection with loss of CD4 cell count and disease progression. However, the mechanisms that underlie the emergence of CXCR4-using variants at this stage are unclear. In the present study, CXCR4-using X4 variants were isolated from plasma samples of HIV-1-infected individuals that dominantly carried vRNA of R5 variants. The sequences of the X4 variants were detected as a minor population using next-generation sequencing. Taken together, CXCR4-using variants at late-stage infection are likely to emerge when replication-competent CXCR4-using variants are maintained as a minor population during the course of infection. The present study may support the hypothesis that R5-to-X4 switching is mediated by the expansion of preexisting X4 variants in some cases.