Genetic variability of principal neutralizing determinants on HIV-1 gp41 and its correlation with subtypes

HIV Transmembrane Glycoprotein Conserved Domains and Genetic Markers Across HIV-1 and HIV-2 Variants

HIV envelope transmembrane glycoproteins gp41 (HIV-1) and gp36 (HIV-2) present high variability and play a key role in the HIV-host cell membrane's fusion, as a target for human broadly neutralizing antibodies (bnAbs) and drugs. Thus, a better knowledge of amino acid (aa) conservation across structural domains and HIV variants can help to identify conserved targets to direct new therapeutic and diagnostic strategies. All available gp41/gp36 nucleotide sequences were downloaded from Los Alamos National Laboratory (LANL) HIV Sequence Database, selecting 17,078 sequences ascribed to HIV-1 and HIV-2 variants with ≥3 sequences. After aligning and translating into aa with MEGAv6.0, an in-house bioinformatics program (EpiMolBio) was used to identify the most conserved aa and the aa changes that were specific for each variant (V-markers) vs. HXB2/BEN (HIV-1/HIV-2) reference sequence. We analyzed the presence of specific aa changes among V-markers affecting infectivity, gp41 structure, function, or resistance to the enfuvirtide viral fusion inhibitor (T-20). We also inferred the consensus sequences per HIV variant, describing in each HIV-1 group (M, N, O, P) the conservation level along the complete gp41 per structural domain and locating in each binding site the anti-gp41 human Abs (bnAbs and non bnAbs) described in LANL. We found 38.3/59.7% highly conserved aa present in ≥90% of the 16,803/275 gp41/gp36 sequences ascribed to 105/3 HIV-1/HIV-2 variants, with 9/12.6% of them showing complete conservation across LANL sequences. The fusion peptide, its proximal region, the N-heptad repeat, and the membrane-proximal external region were the gp41 domains with ≥84% of conserved aa in the HIV-1 consensus sequence, the target of most Abs. No natural major resistance mutations to T-20 were observed. Our results show, for the first time, a complete conservation study of gp41/gp36 per variant in the largest panel of HIV variants analyzed to date, providing useful information for a more rational design of drugs, vaccines, and molecular detection tests targeting the HIV transmembrane glycoprotein.

Enhancing efficacy and mucosa-tropic distribution of an oral HIV-PsV DNA vaccine in animal models

A strategy combined the oral delivery route and bovine papillomavirus (BPV) pseudovirus (PsV)-based human immunodeficiency virus (HIV) DNA vaccine, which has been proven to enhance the mucosal immunization compared with the systemic immunization and in general does not induce effective mucosal immune responses. In this study, the immune responses against the BPV expressing HIV gp41 epitopes (ELDKWA, NWFDIT) after oral administration in Cynomolgus monkeys (Macaca fascicularis) were assessed, and the biodistribution of plasmid DNA encapsulated in the papillomavirus-like particles (VLPs) were evaluated in murine models. Results showed that oral immunization with the HIV-PsV DNA vaccine in monkey generated p24 and gp41 epitopes-specific serum IgG. Importantly, these induced antibodies had been shown to neutralize HIV-1 primary strain. In addition, the advantage of VLPs as vehicles delivering genes had been first revealed in biodistribution results. Therefore, orally administered HIV-PsV DNA vaccine was well-tolerated, enhanced the mucosa targeting property of the plasmid DNA, and reduced the nontargeting distribution, which indicate that it would reduce stress associated with systemic vaccination.

Neutralizing epitopes in the membrane-proximal region of HIV-1 gp41: genetic variability and co-variation

Recent investigations on the passive immunization have proved that neutralizing antibodies directed to the membrane-proximal region of HIV-1 gp41 are potent anti-viral components, so this region is thought to be an attractive target for AIDS vaccine. Three key neutralizing epitopes, ELDKWA (aa662-667), NWFDIT (aa671-676) and ERDRDR (aa739-744) have been mapped in this region. In this study, their genetic variability and co-variation was evaluated. There exists marked shift in the predominant sequence patterns on these three neutralizing epitopes over time. Compared with subtype B, non-B clades exhibit significant genetic variability and co-variation on these three epitopes. Among HIV-1 strains isolated in recent 5 years, about one third displays epitope variants simultaneously on three epitopes. The newly isolated strains with co-variations on several neutralizing epitopes ought to be of strict surveillance in clinical treatment, and those frequent epitope variants should also be considered in vaccine design.