Variation in HIV-1 R5 macrophage-tropism correlates with sensitivity to reagents that block envelope: CD4 interactions but not with sensitivity to other entry inhibitors

Human immunodeficiency virus type 1 (HIV-1) infection in the central nervous system (CNS) is characterized by replication in macrophages or brain microglia that express low levels of the CD4 receptor and is the cause of HIV-associated dementia and related cognitive and motor disorders that affect 20 to 30% of treatment-naive patients with AIDS. Independent viral envelope evolution in the brain has been reported, with the need for robust replication in resident CD4 low cells, as well as CD4-negative cells, such as astrocytes, proposed as a major selective pressure. We previously reported giant-cell encephalitis in subtype B and C R5 simian-human immunodeficiency virus (SHIV)-infected macaques (SHIV-induced encephalitis [SHIVE]) that experienced very high chronic viral loads and progressed rapidly to AIDS, with varying degrees of macrophage or microglia infection and activation of these immune cells, as well as astrocytes, in the CNS. In this study, we characterized envelopes (Env) amplified from the brains of subtype B and C R5 SHIVE macaques. We obtained data in support of an association between severe neuropathological changes, robust macrophage and microglia infection, and evolution to CD4 independence. Moreover, the degree of Env CD4 independence appeared to correlate with the extent of astrocyte infection in vivo. These findings further our knowledge of the CNS viral population phenotypes that are associated with the severity of HIV/SHIV-induced neurological injury and improve our understanding of the mechanism of HIV-1 cellular tropism and persistence in the brain. IMPORTANCE Human immunodeficiency virus type 1 (HIV-1) infection of astrocytes in the brain has been suggested to be important in HIV persistence and neuropathogenesis but has not been definitively demonstrated in an animal model of HIV-induced encephalitis (HIVE).Here, we describe a new nonhuman primate (NHP) model of R5 simian-human immunodeficiency virus (SHIV)-induced encephalitis (SHIVE) with several classical HIVE features that include astrocyte infection. We further show an association between severe neuropathological changes, robust resident microglia infection, and evolution to CD4 independence of viruses in the central nervous system (CNS), with expansion to infection of truly CD4-negative cells in vivo. These findings support the use of the R5 SHIVE models to study the contribution of the HIV envelope and viral clades to neurovirulence and residual virus replication in the CNS, providing information that should guide efforts to eradicate HIV from the body.

Section: Characteristics Of R5 Shiv-infected Macaques With Encephalitissupporting

confidence: 73%

Emergence of CD4 Independence Envelopes and Astrocyte Infection in R5 Simian-Human Immunodeficiency Virus Model of Encephalitis

Zhuang

Léda

Tsai

et al. 2014

“…Therefore, our observations support previous conclusions that replication capacity in macrophages does not correlate with an ability to use CCR5 (59). Because we did not observe significant differences in CD4 receptor use, however, we cannot directly corroborate that CD4 affinity predominately influences macrophage tropism as has been previously suggested (59).…”

Section: Discussioncontrasting

confidence: 38%

“…6). Previous studies and our controls suggest that these measurements could be surrogate markers for coreceptor affinity and fusion kinetics (59,66). Because cell entry is potentially the rate-limiting step in HIV-1 replication (3,44,65), in the aggregate, our data suggest that increases in replication capacity over the course of infection are potentially related to greater affinity for the CCR5 receptor and/or faster fusion kinetics.…”

Section: Discussionmentioning

confidence: 75%

“…Because host cell entry is the ratelimiting step in HIV-1 replication (3,44,65) and entry is potentially limited by receptor binding and fusion (46,61), we hypothesized that early-and chronic-infection viruses had differences in receptor attachment and fusion kinetics. Previous studies suggest that sensitivity to receptor inhibitors correlates with the affinity of the viral envelope for the host cell receptor (59,66 (49). HXB-2 E370D pseudotypes (IC 50 , 1.3 g/ml Ϯ 1.1 g/ml) had approximately 13-fold greater sensitivity to soluble CD4 than wild-type HXB-2 pseudotypes (IC 50 , 27.3 g/ml Ϯ 3.4 g/ml).…”

Section: Resultsmentioning

confidence: 99%

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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

Etemad

Fellows

Kwambana-Adams

et al. 2009

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...

“…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.…”

Section: Vol 85 2011 Ibalizumab Susceptibility Of Hiv-1 3873mentioning

confidence: 99%

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

Toma¹,

Weinheimer

Stawiski³

et al. 2011

Ibalizumab (formerly TNX-355) is a first-in-class, monoclonal antibody inhibitor of CD4-mediated human immunodeficiency type 1 (HIV-1) entry. Multiple clinical trials with HIV-infected patients have demonstrated the antiviral activity, safety, and tolerability of ibalizumab treatment. A 9-week phase Ib study adding ibalizumab monotherapy to failing drug regimens led to transient reductions in HIV viral loads and the evolution of HIV-1 variants with reduced susceptibility to ibalizumab. This report characterizes these variants by comparing the phenotypic susceptibilities and envelope (env) sequences of (i) paired baseline and ontreatment virus populations, (ii) individual env clones from selected paired samples, and (iii) env clones containing site-directed mutations. Viruses with reduced susceptibility to ibalizumab were found to exhibit reduced susceptibility to the anti-CD4 antibody RPA-T4. Conversely, susceptibility to soluble CD4, which targets the HIV-1 gp120 envelope protein, was enhanced. No changes in susceptibility to the fusion inhibitor enfuvirtide or the CCR5 antagonist maraviroc were observed. Functionally, viruses with reduced ibalizumab susceptibility also displayed high levels of infectivity relative to those of paired baseline viruses. Individual env clones exhibiting reduced ibalizumab susceptibility contained multiple amino acid changes in different regions relative to the paired baseline clones. In particular, clones with reduced susceptibility to ibalizumab contained fewer potential asparagine-linked glycosylation sites (PNGSs) in variable region 5 (V5) than did paired ibalizumab-susceptible clones. The reduction in ibalizumab susceptibility due to the loss of V5 PNGSs was confirmed by site-directed mutagenesis. Taken together, these findings provide important insights into resistance to this new class of antiretroviral drug.