Higher homologous and lower cross-reactive Gag-specific T-cell responses in human immunodeficiency virus type 2 (HIV-2) than in HIV-1 infection

Clonotypic architecture of a Gag-specific CD8+ T-cell response in chronic human HIV-2 infection

The dynamics of T-cell receptor (TCR) selection in chronic HIV-1 infection, and its association with clinical outcome, is well documented for an array of MHC-peptide complexes and disease stages. However, the factors that may contribute to the selection and expansion of CD8+ T-cells in chronic HIV-2 infection, especially at clonal level remain unclear. To address this question, we undertook a detailed molecular characterization of the clonotypic architecture of an HLA-B*3501 restricted Gag -specific CD8+ T-cell response in donors chronically infected with HIV-2 using a combination of flow cytometry, tetramer-specific CD8+ TCR clonotyping and in vitro assays. We show that the response to the NY9 epitope is hierarchical and narrow in terms of T-cell receptor alpha (TCRA) and beta (TCRB) gene usage yet clonotypically diverse. Furthermore, clonotypic dominance in shared origin cytotoxic T lymphocyte (CTL) clones was associated with a greater magnitude of cytokine production and antigen sensitivity at limiting antigen dilution as well as enhanced cross-reactivity for known HIV-2 variants. Hence, our data suggest that effector mobilization and expansion in human chronic HIV-2 infection may be linked to the qualitative features of specific CD8+ T-cell clonotypes, which could have implications for viral control and disease outcome. This article is protected by copyright. All rights reserved.

HIV-1 is more dependent on the K182 capsid residue than HIV-2 for interactions with CPSF6

The HIV-1 capsid (CA) utilizes CPSF6 for nuclear entry and integration site targeting. Previous studies demonstrated that the HIV-1 CA C-terminal domain (CTD) contains a highly conserved K182 residue involved in interaction with CPSF6. In contrast, certain HIV-2 strains possess a substitution at this residue (K182R). To assess whether CA-CPSF6 interaction via the CA CTD is conserved among primate lentiviruses, we examined resistance of several HIV-1- and HIV-2-lineage viruses to a truncated form of CPSF6, CPSF6-358. The results demonstrated that viruses belonging to the HIV-2-lineage maintain interaction with CPSF6 regardless of the presence of the K182R substitution, in contrast to the case with HIV-1-lineage viruses. Our structure-guided mutagenesis indicated that the differential requirement for CA-CPSF6 interaction is regulated in part by residues near the 182nd amino acid of CA. These results demonstrate a previously unrecognized distinction between HIV-1 and HIV-2, which may reflect differences in their evolutionary histories.

HIV-2 and its role in conglutinated approach towards Acquired Immunodeficiency Syndrome (AIDS) Vaccine Development

Acquired Immunodeficiency Syndrome (AIDS) is one of the most critically acclaimed endemic diseases, caused by two lentiviruses HIV-1 and 2. HIV-2 displays intimate serological and antigenic resemblance to Simian Immunodeficiency Virus (SIV) along with less pathogenicity, lower infectivity and appreciable cross reactivity with HIV-1 antigens. The present era is confronted with the challenge to fabricate a vaccine effective against all clades of both the species of HIV. But vaccine development against HIV-1 has proven highly intricate, moreover the laborious and deficient conventional approaches has slackened the pace regarding the development of new vaccines. These concerns may be tackled with the development of HIV-2 vaccine as a natural control of HIV-1 that has been found in ancestors of HIV-2 i.e. African monkeys, mangabeys and macaques. Thereby, suggesting the notion of cross protection among HIV-2 and HIV-1. Assistance of bioinformatics along with vaccinomics strategy can bring about a quantum leap in this direction for surpassing the bottleneck in conventional approaches. These specifics together can add to our conception that HIV-2 vaccine design by in silico strategy will surely be a constructive approach for HIV-1 targeting.

Expression analysis of LEDGF/p75, APOBEC3G, TRIM5alpha, and tetherin in a Senegalese cohort of HIV-1-exposed seronegative individuals

Background

HIV-1 replication depends on a delicate balance between cellular co-factors and antiviral restriction factors. Lens epithelium-derived growth factor (LEDGF/p75) benefits HIV, whereas apolipoprotein B mRNA-editing catalytic polypeptide-like 3G (APOBEC3G), tripartite motif 5alpha (TRIM5α), and tetherin exert anti-HIV activity. Expression levels of these proteins possibly contribute to HIV-1 resistance in HIV-1-exposed populations.

Methodology/Principal Findings

We used real-time PCR and flow cytometry to study mRNA and protein levels respectively in PBMC and PBMC subsets. We observed significantly reduced LEDGF/p75 protein levels in CD4+ lymphocytes of HIV-1-exposed seronegative subjects relative to healthy controls, whereas we found no differences in APOBEC3G, TRIM5α, or tetherin expression. Untreated HIV-1-infected patients generally expressed higher mRNA and protein levels than healthy controls. Increased tetherin levels, in particular, correlated with markers of disease progression: directly with the viral load and T cell activation and inversely with the CD4 count.

Conclusions/Significance

Our data suggest that reduced LEDGF/p75 levels may play a role in resistance to HIV-1 infection, while increased tetherin levels could be a marker of advanced HIV disease. Host factors that influence HIV-1 infection and disease could be important targets for new antiviral therapies.

Intracellular detection of differential APOBEC3G, TRIM5alpha, and LEDGF/p75 protein expression in peripheral blood by flow cytometry

Expression studies on specific host proteins predominantly use quantitative PCR and western blotting assays. In this study, we optimized a flow cytometry-based assay to study intracellular expression levels of three important host proteins involved in HIV-1 replication: apolipoprotein B mRNA-editing catalytic polypeptide-like 3G (APOBEC3G), tripartite motif 5alpha (TRIM5α), and lens epithelium-derived growth factor (LEDGF/p75). An indirect intracellular staining (ICS) method was optimized using antibodies designed for other applications like enzyme-linked immunosorbent assay (ELISA), confocal imaging, and western blotting. The median fluorescence intensity (MFI) value--a measure for the protein expression level--increased upon higher antibody concentration and longer incubation time, and was reduced following preincubation with recombinant proteins. Staining of stably transfected or knock-down cell lines supported the method's specificity. Moreover, confocal microscopy analysis of peripheral blood mononuclear cells (PBMC), when stained according to the ICS method, confirmed the localization of APOBEC3G and TRIM5α in the cytoplasm, and of LEDGF/p75 in the nucleus. Also, stimulation with mitogen, interferon-alpha, or interferon-beta resulted in detectable, albeit weak, increases in intracellular expression of APOBEC3G and TRIM5α. After optimization, the method was applied to healthy control and HIV-1 infected subjects. For all subjects studied, the memory subset of CD4+ T cells showed significantly higher expression levels of APOBEC3G, TRIM5α, and LEDGF/p75, while the CD16+ subset of monocytes was characterized by higher expression levels of LEDGF/p75. In addition, we observed that therapy-naïve HIV-1 patients tended to have lower expression levels of APOBEC3G and TRIM5α than HIV-1 negative controls. In summary, our data provide proof-of-principle for the detection of specific host factors at the level of a single cell, which may prove useful for our further understanding of their role in virus-host interactions.