Pairwise comparison of isogenic HIV-1 viruses: R5 phenotype replicates more efficiently than X4 phenotype in primary CD4+ T cells expressing physiological levels of CXCR4

Immune activation correlates with and predicts CXCR4 co-receptor tropism switch in HIV-1 infection

HIV-1 cell entry is mediated by binding to the CD4-receptor and chemokine co-receptors CCR5 (R5) or CXCR4 (X4). R5-tropic viruses are predominantly detected during early infection. A switch to X4-tropism often occurs during the course of infection. X4-tropism switching is strongly associated with accelerated disease progression and jeopardizes CCR5-based HIV-1 cure strategies. It is unclear whether host immunological factors play a causative role in tropism switching. We investigated the relationship between immunological factors and X4-tropism in a cross-sectional study in HIV-1 subtype C (HIV-1C)-infected patients and in a longitudinal HIV-1 subtype B (HIV-1B) seroconverter cohort. Principal component analysis identified a cluster of immunological markers (%HLA-DR⁺ CD4⁺ T-cells, %CD38⁺HLA-DR⁺ CD4⁺ T-cells, %CD38⁺HLA-DR⁺ CD8⁺ T-cells, %CD70⁺ CD4⁺ T-cells, %CD169⁺ monocytes, and absolute CD4⁺ T-cell count) in HIV-1C patients that was independently associated with X4-tropism (aOR 1.044, 95% CI 1.003–1.087, p = 0.0392). Analysis of individual cluster contributors revealed strong correlations of two markers of T-cell activation (%HLA-DR⁺ CD4⁺ T-cells, %HLA-DR⁺CD38⁺ CD4⁺ T-cells) with X4-tropism, both in HIV-1C patients (p = 0.01;p = 0.03) and HIV-1B patients (p = 0.0003;p = 0.0001). Follow-up data from HIV-1B patients subsequently revealed that T-cell activation precedes and independently predicts X4-tropism switching (aHR 1.186, 95% CI 1.065–1.321, p = 0.002), providing novel insights into HIV-1 pathogenesis and CCR5-based curative strategies.

Molecular Features of the V1-V4 Coding Region of Sexually Transmitted Human Immunodeficiency Virus Type 1

Background

Investigations into which human immunodeficiency virus type 1 (HIV-1) sequence features may be selected for transmission during sexual exposure have been hampered by the small number of characterized transmission pairs in individual studies.

Methods

To boost statistical power to detect differences in glycosylation, length, and electrical charge in the HIV-1 V1-V4 coding region, we reanalyzed all available 2485 env sequences derived from 114 subjects representing 58 transmission pairs from previous studies using mixed-effects linear regression and an approach to approximate the unobserved transmitted virus.

Results

The recipient partner had a shorter V1-V4 region and fewer potential N-linked glycosylation sites (PNGS) than sequences from the source partner. We also detected a trend toward more PNGS and lower isoelectric points in transmitted sequences with source partner and the evolutionary tendency to shorten V1-V4 sequences, reduce the number of PNGS, and lower isoelectric points in the recipient following transmission.

Conclusions

By using all available well-characterized env sequences from transmission pairs via sexual exposure, we were able to identify several important virologic factors that may be important in the development of biomedical preventive interventions.

Dectin-1/TLR2 and NOD2 agonists render dendritic cells susceptible to infection by X4-using HIV-1 and promote cis-infection of CD4(+) T cells

HIV-1 pathogenesis is intimately linked with microbial infections and innate immunity during all stages of the disease. While the impact of microbial-derived products in transmission of R5-using virus to CD4⁺ T cells by dendritic cells (DCs) has been addressed before, very limited data are available on the effect of such compounds on DC-mediated dissemination of X4-tropic variant. Here, we provide evidence that treatment of DCs with dectin-1/TLR2 and NOD2 ligands increases cis-infection of autologous CD4⁺ T cells by X4-using virus. This phenomenon is most likely associated with an enhanced permissiveness of DCs to productive infection with X4 virus, which is linked to increased surface expression of CXCR4 and the acquisition of a maturation profile by DCs. The ensuing DC maturation enhances susceptibility of CD4⁺ T cells to productive infection with HIV-1. This study highlights the crucial role of DCs at different stages of HIV-1 infection and particularly in spreading of viral strains displaying a X4 phenotype.

Asymmetric HIV-1 co-receptor use and replication in CD4(+) T lymphocytes

Susceptibility to infection by the human immunodeficiency virus type-1 (HIV-1), both in vitro and in vivo, requires the interaction between its envelope (Env) glycoprotein gp120 Env and the primary receptor (R), CD4, and Co-R, either CCR5 or CXCR4, members of the chemokine receptor family. CCR5-dependent (R5) viruses are responsible for both inter-individual transmission and for sustaining the viral pandemics, while CXCR4-using viruses, usually dualtropic R5X4, emerge in ca. 50% of individuals only in the late, immunologically suppressed stage of disease. The hypothesis that such a major biological asymmetry is explained exclusively by the availability of cells expressing CCR5 or CXCR4 is challenged by several evidences. In this regard, binding of the HIV-1 gp120 Env to the entry R complex, i.e. CD4 and a chemokine R, leads to two major events: virion-cell membrane fusion and a cascade of cell signaling. While the fusion/entry process has been well defined, the role of R/Co-R signaling in the HIV-1 life cycle has been less characterized. Indeed, depending on the cellular model studied, the capacity of HIV-1 to trigger a flow of events favoring either its own latency or replication remains a debated issue. In this article, we will review the major findings related to the role of HIV R/Co-R signaling in the steps following viral entry and leading to viral spreading in CD4⁺ T lymphocytes.