V1 and V2 Domains of HIV Envelope Contribute to CCR5 Antagonist Resistance

Evolution of Multiple Domains of the HIV-1 Envelope Glycoprotein during Coreceptor Switch with CCR5 Antagonist Therapy

HIV-1 uses CD4 as a receptor and chemokine receptors CCR5 and/or CXCR4 as coreceptors. CCR5 antagonists are a class of antiretrovirals used to inhibit viral entry. Phenotypic prediction algorithms such as Geno2Pheno are used to assess CCR5 antagonist eligibility, for which the V3 region is screened. However, there exist scenarios where the algorithm cannot give an accurate prediction of tropism. The current study examined coreceptor shift of HIV-1 from CCR5-tropic strains to CXCR4-tropic or dual-tropic strains among five subjects in a clinical trial of the CCR5 antagonist vicriviroc. Envelope gene amplicon libraries were constructed and subjected to next-generation sequencing, as well as single-clone sequencing and functional analyses. Approximately half of the amplified full-length single envelope-encoding clones had no significant activity for infection of cells expressing high levels of CD4 and CCR5 or CXCR4. Functional analysis of 9 to 21 individual infectious clones at baseline and at the time of VF were used to construct phylogenetic trees and sequence alignments. These studies confirmed that specific residues and the overall charge of the V3 loop were the major determinants of coreceptor use, in addition to specific residues in other domains of the envelope protein in V1/V2, V4, C3, and C4 domains that may be important for coreceptor shift. These results provide greater insight into the viral genetic determinants of coreceptor shift. IMPORTANCE This study is novel in combining single-genome sequence analysis and next-generation sequencing to characterize HIV-1 quasispecies. The work highlights the importance of mutants present at frequencies of 1% or less in development of drug resistance. This study highlights a critical role of specific amino acid substitutions outside V3 that contribute to coreceptor shift as well as important roles of the V1/V2, V4, C3, and C4 domain residues.

Emergence of Nanotechnology to Fight HIV Sexual Transmission: The Trip of G2-S16 Polyanionic Carbosilane Dendrimer to Possible Pre-Clinical Trials

Development of new, safe, and effective microbicides to prevent human immunodeficiency virus HIV sexual transmission is needed. Unfortunately, most microbicides proved ineffective to prevent the risk of HIV-infection in clinical trials. We are working with G2-S16 polyanionic carbosilane dendrimer (PCD) as a new possible vaginal topical microbicide, based on its short reaction times, wide availability, high reproducibility, and quantitative yields of reaction. G2-S16 PCD exerts anti-HIV activity at an early stage of viral replication, by blocking gp120/CD4/CCR5 interaction, and providing a barrier against infection for long periods of time. G2-S16 PCD was stable at different pH values, as well as in the presence of seminal fluids. It maintained the anti-HIV activity against R5/X4 HIV over time, did not generate any type of drug resistance, and retained the anti-HIV effect when exposed to semen-enhanced viral infection. Importantly, G2-S16 PCD did not modify vaginal microbiota neither in vitro or in vivo. Histopathological examination did not show vaginal irritation, inflammation, lesions, or damage in the vaginal mucosa, after administration of G2-S16 PCD at different concentrations and times in female mice and rabbit animal models. Based on these promising data, G2-S16 PCD could become a good, safe, and readily available candidate to use as a topical vaginal microbicide against HIV.

Characterization of envelope sequence of HIV virus in children infected with HIV in Vietnam

Background:

HIV is characterized by high levels of genetic variability, including increased numbers of heterogeneous sequences of the envelope region. Therefore, studying genetic variability of HIV in relation to viral replication might facilitate prognosis of disease progression.

Methods:

The study was designed as cross-sectional; data and samples of participants collected and analyzed env genes were obtained from 23 children enrolled by Vietnam National Children’s Hospital.

Results:

Substantial mutations in the C2 region were found in patients with high levels of viral replication while changes in the C3 region were mostly found in patients with low viral load. In the V1 region, we found profound amino acid modifications in patients with low HIV viral loads in contrast to the V2 sequence, where we identified single point mutations in patients with increased HIV viral load. The V3 region was relatively homogeneous, while profound deletions in the V4 region were detected in patients with increased viral replication.

Conclusion:

Our results suggest that genetic variations in different regions of the HIV envelope sequence, including both conserved C2 and C3 and variable V1/V2 and V4 regions, might be involved in increased viral infectivity and replication capacity. Such knowledge might help improve prediction of HIV progress and treatment in patients.

P2X1 Selective Antagonists Block HIV-1 Infection through Inhibition of Envelope Conformation-Dependent Fusion

Purinergic receptors are well-established modulators of inflammatory processes, primarily through detection of extracellular nucleotides that are released by dying or infected cells. Emerging literature has demonstrated that inhibition of these inflammatory receptors can block HIV-1 productive infection and HIV-1-associated inflammation. The specificity of receptor type and mechanism of interaction has not yet been determined. Here, we characterize the inhibitory activity of P2X1 receptor antagonists, NF279 and NF449, in cell lines, primary cells, and a variety of HIV-1 envelope (Env) clades. NF279 and NF449 blocked productive infection at the level of viral membrane fusion, with a range of inhibitory activities against different HIV-1 Env isolates. A mutant virus carrying a truncation deletion of the C-terminal tail of HIV-1 Env glycoprotein 41 (gp41) showed reduced sensitivity to P2X1 antagonists, indicating that the sensitivity of inhibition by these molecules may be modulated by Env conformation. In contrast, a P2X7 antagonist, A438079, had a limited effect on productive infection and fusion. NF279 and NF449 interfered with the ability of the gp120 variable regions 1 and 2 (V1V2)-targeted broadly neutralizing antibody PG9 to block productive infection, suggesting that these drugs may antagonize HIV-1 Env at gp120 V1V2 to block viral membrane fusion. Our observations indicate that P2X1 antagonism can inhibit HIV-1 replication at the level of viral membrane fusion through interaction with Env. Future studies will probe the nature of these compounds in inhibiting HIV-1 fusion and the development of small molecules to block HIV-1 entry via this mechanism.IMPORTANCE While effective treatment can lower the severe morbidity and mortality associated with HIV-1 infection, patients infected with HIV-1 suffer from significantly higher rates of noncommunicable comorbidities associated with chronic inflammation. Emerging literature suggests a key role for P2X1 receptors in mediating this chronic inflammation, but the mechanism is still unknown. Here, we demonstrate that HIV-1 infection is reduced by P2X1 receptor antagonism. This inhibition is mediated by interference with HIV-1 Env and can impact a variety of viral clades. These observations highlight the importance of P2X1 antagonists as potential novel therapeutics that could serve to block a variety of different viral clades with additional benefits for their anti-inflammatory properties.