Human Immunodeficiency Virus Type 1 V1-to-V5 Envelope Variants from the Chronic Phase of Infection Use CCR5 and Fuse More Efficiently than Those from Early after Infection

Abstract

Human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein modifications over the course of infection have been associated with coreceptor switching and antibody neutralization resistance, but the effect of the changes on replication and host cell receptor usage remains unclear. To examine this question, unique early-and chronic-stage infection envelope V1-toV5 (V1-V5) segments from eight HIV-1 subtype A-infected subjects were incorporated into an isogenic background to construct replication-competent recombinant viruses. In all subjects, viruses with chronic-infection V1-V5 segments showed greater replication capacity than those with early-infection V1-V5 domains in cell lines with high levels of both the CD4 and the CCR5 receptors. Viruses with chronic-infection V1-V5s demonstrated a significantly increased ability to replicate in cells with low CCR5 receptor levels and greater resistance to CCR5 receptor and fusion inhibitors compared to those with early-infection V1-V5 segments. These properties were associated with sequence changes in the envelope V1-V3 segments. Viruses with the envelope segments from the two infection time points showed no significant difference in their ability to infect cells with low CD4 receptor densities, in their sensitivity to soluble CD4, or in their replication capacity in monocyte-derived macrophages. Our results suggest that envelope changes, primarily in the V1-V3 domains, increase both the ability to use the CCR5 receptor and fusion kinetics. Thus, envelope modifications over time within a host potentially enhance replication capacity.The human immunodeficiency virus type 1 (HIV-1) viral envelope glycoprotein evolves over the course of infection (24,78), with the portion from constant region 2 to variable loop 5 (C2-V5) diversifying at an approximate rate of 1% per year in the absence of antiretroviral medications (77). The envelope glycoprotein variable loops 1 and 2 (V1-V2) expand and add more glycosylation sites over the course of infection (21, 76). These envelope changes arise primarily due to errors during reverse transcription, the high rate of viral replication, and recombination (25,42,58,86). The rate of mutation fixation in a virus population, however, depends on both the level of viral replication and, more importantly, the selective advantage or disadvantage conferred by the mutation. The host immune response and the replication capacity in the available target cells primarily drive this selection (12, 51). Envelope modifications that confer an advantage in evading the host humoral immune response and/or increase the efficiency of target cell infection and replication are likely favored over the course of an infection within a subject.Studies with the simian immunodeficiency virus/macaque model, simian human immunodeficiency virus, and HIV-1 have shown that envelope modifications that occur over the course of an infection confer antibody neutralization resistance (8,9,72,85). The host neutralizing antibodies target specific epitopes on the circulating vira...

Donor and Recipient Envs from Heterosexual Human Immunodeficiency Virus Subtype C Transmission Pairs Require High Receptor Levels for Entry

“…Indeed, when previously described cloned Envs (BBB, NNB, NBB) were tested in a replication-competent green fluorescent protein (GFP) reporter system for entry into the cell lines used in this study, the infectivities were consistent with the prior report (data not shown) (19). Using V1-V5 chimeric replication-competent subtype A viruses, Etemad et al (5) observed reduced replication in JC-10 cells for those chimeras containing the acute virus fragment relative to that for those containing fragments from chronically infected partners, although both replicated on these cells less efficiently than on JC-53 cells. Thus, it is possible that viruses from subtype A transmission pairs differ in their CCR5 requirements from those we have observed for subtype C Envs.…”

Enhanced Fusion and Virion Incorporation for HIV-1 Subtype C Envelope Glycoproteins with Compact V1/V2 Domains

“…HIV-1 variants encoding Envs with shorter and less glycosylated variable domains were selected for during transmission, suggesting that compact Envs confer a greater transmissibility or fitness advantage in establishing new infection. Until recently, no clear functional phenotype could be attributed to the founder Env (24,34,40,(52)(53)(54). In fact, the only phenotype reported for compact Envs was increased sensitivity to neutralizing antibodies in linked donor plasma, which does not explain the selective advantage in a new host where no HIV-1 immune response has developed.…”

“…Some variable domains that are functional in the context of a particular Env backbone might not be functional in another (22). Several studies have highlighted a possible connection between the V1/V2 domain and HIV-1 infection efficiency (23)(24)(25)(26). Virions encoding chimeric BaL Env with V1/V2 domains from JR-CSF or NL4-3 replicate less efficiently in macrophages but not in lymphocyte cultures (23,25).…”

“…Elimination of glycosylation sites neighboring the V1/V2 region also compromises replication of DH12 dual-tropic primary isolates in peripheral blood mononuclear cells (PBMCs) (26). Chimeric Envs with V1 to V5 domains seem to fuse to target cells with low CCR5 levels more efficiently during the chronic phase of HIV-1 infection than during the acute phase of infection (24). In this study, the Env sequences identified during the chronic phase of infection fused to target cells contained a higher number of predicted glycosylation sites within their V1/V2 domains and were less sensitive to the fusion inhibitor enfuvirtide (T20), which served as an indicator of faster and more efficient fusion (24,27).…”

Loss of Asparagine-Linked Glycosylation Sites in Variable Region 5 of Human Immunodeficiency Virus Type 1 Envelope Is Associated with Resistance to CD4 Antibody Ibalizumab

“…Previous studies demonstrated that alterations in gp120-CD4 interactions can impact viral infectivity and membrane fusion (8,22,31,32). To investigate whether reductions in ibalizumab susceptibility affect these Env-mediated functions, we assessed the in vitro infectivities of paired day 0 and week 9 virus isolates by comparing reporter gene expression levels in the HIV-1 entry assay.…”