HIV type 2 primary isolates induce a lower degree of apoptosis "in vitro" compared with HIV type 1 primary isolates

The HIV-2 OGH double reporter virus shows that HIV-2 is less cytotoxic and less sensitive to reactivation from latency than HIV-1 in cell culture

A better understanding of HIV-1 latency is a research priority in HIV cure research. Conversely, little is known about the latency characteristics of HIV-2, the closely related human lentivirus. Though both viruses cause AIDS, HIV-2 infection progresses more slowly with significantly lower viral loads, even when corrected for CD4+ T cell counts. Hence a direct comparison of latency characteristics between HIV-1 and HIV-2 could provide important clues towards a functional cure. Transduction of SupT1 cells with single-round HIV-1 and HIV-2 viruses with an enhanced green fluorescent protein (eGFP) reporter showed higher levels of eGFP expression for HIV-2 than HIV-1, while HIV-1 expression appeared more cytotoxic. To compare HIV-1 and HIV-2 gene expression, latency and reactivation in more detail, we have generated HIV-2 OGH, a replication deficient, near full- length, double reporter virus that discriminates latently and productively infected cells in cell culture. This construct is based on HIV-1 OGH, and to our knowledge, first of its kind for HIV-2. Using this construct we have observed a higher eGFP expression for HIV-2, but higher losses of HIV-1 transduced cells in SupT1 and Jurkat cells and a reduced sensitivity of HIV-2 for reactivation with TNF-α. In addition, we have analysed HIV-2 integration sites and their epigenetic environment. HIV-1 and HIV-2 share a preference for actively transcribed genes in gene-dense regions and favor active chromatin marks while disfavoring methylation markers associated with heterochromatin. In conclusion the HIV-2 OGH construct provides an interesting tool for studying HIV-2 expression, latency and reactivation. As simian immunodeficiency virus (SIV) and HIV-2 have been proposed to model a functional HIV cure, a better understanding of the mechanisms governing HIV-2 and SIV latency will be important to move forward. Further research is needed to investigate if HIV-2 uses similar mechanisms as HIV-1 to achieve its integration site selectivity.

Quantitative proteomics analysis reveals unique but overlapping protein signatures in HIV infections

BACKGROUND

Human immunodeficiency virus-1 (HIV-1) exploits human host factors to complete its life cycle. Hence, discovery of HIV-regulated host proteins markers would better our understanding of the virus life-cycle and its contribution to pathogenesis and discovery of objective diagnostic and prognostic molecules.

METHODS

We conducted holistic total proteomics analysis of three closely related study populations including patients with HIV type-1 (HIV-1) and HIV type-2 (HIV-2) as well as HIV-1 elite controllers (HIV-1-EC). Peripheral blood plasma (PBP) samples were subjected to label-free quantitative liquid-chromatography tandem mass-spectrometry (LC-MS/MS).

RESULTS

Over 314 unique PBP protein species were identified of which 100 (approx. 32%) were significantly differentially expressed (≥2 to ∞ - fold-change; p < 0.05) between the three sample cohorts. Of the 100 proteins, 91 were significantly changed between pairs of HIV-1 versus HIV-1-EC, while 83 of the 100 proteins differed significantly between HIV-2 and HIV-1-EC. Interestingly, 76 proteins (87.5%) overlap between the two data sets indicating that majority of these proteins share similar expression changes between HIV-1 and HIV-2 sample groups. Two of the identified proteins, XRCC5 and PSME1, were implicated in the early phase of the pathway network for HIV life cycle, while others were involved in infectious disease and disease of signal transduction. Among them were MAP2K1, RPL23A, RPS3, CALR, PRDX1, SOD2, LMNB1, PHB, and FGB. Despite the high degree of similarity in protein profiles of HIV-1 and HIV-2, six proteins differed significantly including ETFB, PHB2, S100A9, LMO2, PPP3R1 and Vif, a fragment of virion infectivity factor of HIV-1. Additionally, 15 proteins were uniquely expressed, and one of them (LSP1) is present only in HIV-1-EC but absent in HIV1 and HIV-2 and vice versa for the rest 14 proteins.

CONCLUSIONS

Altogether, we have identified HIV-specific/related protein expression changes that might potentially be capable of early diagnosis and prognosis of HIV diseases and other related infectious diseases.

Differentially expressed host long intergenic noncoding RNA and mRNA in HIV-1 and HIV-2 infection

Non-coding RNAs and mRNAs have been implicated in replication, pathogenesis and host response in HIV infection. However, the impact of long intergenic non-coding RNAs (lincRNAs) on HIV-1 and HIV-2 infection is not known. In this study, we have analyzed expression profiles of lincRNAs and mRNAs in monocyte derived macrophages (MDMs) infected with HIV-1/HIV-2 using microarrays. Our study identified many differentially expressed lincRNAs and mRNAs in MDMs infected with HIV-1/HIV-2 compared to uninfected MDMs. Genes involved in glutathione metabolism and lysine degradation were differentially regulated only in HIV-1 infected MDMs. In HIV-2 infected MDMs, CUL 2, SFRS9, and RBBP4 genes were differentially expressed. Furthermore, we found that plasma levels of lincRNA: chr2: 165509129-165519404 and lincRNA: chr12: 57761837-57762303 were better indicators of HIV-1 infection while lincRNA: chr10:128586385-128592960, XLOC_001148 and lincRNA: chr5:87580664-87583451, were better indicators of HIV-2 infection. In summary, our study has demonstrated that there is substantial alteration in lincRNA and mRNA expression in response to HIV-1/HIV-2 infection. These differentially expressed lincRNAs and mRNAs could serve as prognostic and diagnostic biomarkers of HIV infection and help in the identification of new targets for therapy.

Identification of Host Micro RNAs That Differentiate HIV-1 and HIV-2 Infection Using Genome Expression Profiling Techniques

While human immunodeficiency virus type 1 and 2 (HIV-1 and HIV-2) share many similar traits, major differences in pathogenesis and clinical outcomes exist between the two viruses. The differential expression of host factors like microRNAs (miRNAs) in response to HIV-1 and HIV-2 infections are thought to influence the clinical outcomes presented by the two viruses. MicroRNAs are small non-coding RNA molecules which function in transcriptional and post-transcriptional regulation of gene expression. MiRNAs play a critical role in many key biological processes and could serve as putative biomarker(s) for infection. Identification of miRNAs that modulate viral life cycle, disease progression, and cellular responses to infection with HIV-1 and HIV-2 could reveal important insights into viral pathogenesis and provide new tools that could serve as prognostic markers and targets for therapeutic intervention. The aim of this study was to elucidate the differential expression profiles of host miRNAs in cells infected with HIV-1 and HIV-2 in order to identify potential differences in virus-host interactions between HIV-1 and HIV-2. Differential expression of host miRNA expression profiles was analyzed using the miRNA profiling polymerase chain reaction (PCR) arrays. Differentially expressed miRNAs were identified and their putative functional targets identified. The results indicate that hsa-miR 541-3p, hsa-miR 518f-3p, and hsa-miR 195-3p were consistently up-regulated only in HIV-1 infected cells. The expression of hsa-miR 1225-5p, hsa-miR 18a* and hsa-miR 335 were down modulated in HIV-1 and HIV-2 infected cells. Putative functional targets of these miRNAs include genes involved in signal transduction, metabolism, development and cell death.

Analysis of Host Gene Expression Profile in HIV-1 and HIV-2 Infected T-Cells

HIV replication is closely regulated by a complex pathway of host factors, many of them being determinants of cell tropism and host susceptibility to HIV infection. These host factors are known to exert a positive or negative influence on the replication of the two major types of HIV, HIV-1 and HIV-2, thereby modulating virus infectivity, host response to infection and ultimately disease progression profiles characteristic of these two types. Understanding the differential regulation of host cellular factors in response to HIV-1 and HIV-2 infections will help us to understand the apparent differences in rates of disease progression and pathogenesis. This knowledge would aid in the discovery of new biomarkers that may serve as novel targets for therapy and diagnosis. The objective of this study was to determine the differential expression of host genes in response to HIV-1/HIV-2 infection. To achieve this, we analyzed the effects of HIV-1 (MN) and HIV-2 (ROD) infection on the expression of host factors in PBMC at the RNA level using the Agilent Whole Human Genome Oligo Microarray. Differentially expressed genes were identified and their biological functions determined. Host gene expression profiles were significantly changed. Gene expression profiling analysis identified a subset of differentially expressed genes in HIV-1 and HIV-2 infected cells. Genes involved in cellular metabolism, apoptosis, immune cell proliferation and activation, cytokines, chemokines, and transcription factors were differentially expressed in HIV-1 infected cells. Relatively few genes were differentially expressed in cells infected with HIV-2.

HIV-1 and HIV-2 differentially mature plasmacytoid dendritic cells into IFN-producing cells or APCs

HIV-1 causes a progressive impairment of immune function. HIV-2 is a naturally attenuated form of HIV, and HIV-2 patients display a slow-progressing disease. The leading hypothesis for the difference in disease phenotype between HIV-1 and HIV-2 is that more efficient T cell-mediated immunity allows for immune-mediated control of HIV-2 infection, similar to that observed in the minority of HIV-1-infected long-term nonprogressors. Understanding how HIV-1 and HIV-2 differentially influence the immune function may highlight critical mechanisms determining disease outcome. We investigated the effects of exposing primary human peripheral blood cells to HIV-1 or HIV-2 in vitro. HIV-2 induced a gene expression profile distinct from HIV-1, characterized by reduced type I IFN, despite similar upregulation of IFN-stimulated genes and viral restriction factors. HIV-2 favored plasmacytoid dendritic cell (pDC) differentiation into cells with an APC phenotype rather than IFN-α-producing cells. HIV-2, but not HIV-1, inhibited IFN-α production in response to CpG-A. The balance between pDC maturation into IFN-α-producing cells or development of an APC phenotype differentiates the early response against HIV-1 and HIV-2. We propose that divergent paths of pDC differentiation driven by HIV-1 and HIV-2 cause the observed differences in pathogenicity between the two viruses.

Comparing HIV-1 and HIV-2 infection: Lessons for viral immunopathogenesis

HIV-1 and HIV-2 share many similarities including their basic gene arrangement, modes of transmission, intracellular replication pathways and clinical consequences: both result in AIDS. However, HIV-2 is characterised by lower transmissibility and reduced likelihood of progression to AIDS. The underlying mechanistic differences between these two infections illuminate broader issues of retroviral pathogenesis, which remain incompletely understood. Comparisons between these two infections from epidemiological, clinical, virologic and immunologic viewpoints provide a basis for hypothesis generation and testing in this 'natural experiment' in viral pathogenesis. In terms of epidemiology, HIV-2 remains largely confined to West Africa, whereas HIV-1 extends worldwide. Clinically, HIV-2 infected individuals seem to dichotomise, most remaining long-term non-progressors, whereas most HIV-1 infected individuals progress. When clinical progression occurs, both diseases demonstrate very similar pathological processes, although progression in HIV-2 occurs at higher CD4 counts. Plasma viral loads are consistently lower in HIV-2, as are average levels of immune activation. Significant differences exist between the two infections in all components of the immune system. For example, cellular responses to HIV-2 tend to be more polyfunctional and produce more IL-2; humoral responses appear broader with lower magnitude intratype neutralisation responses; innate responses appear more robust, possibly through differential effects of tripartite motif protein isoform 5 alpha. Overall, the immune response to HIV-2 appears more protective against disease progression suggesting that pivotal immune factors limit viral pathology. If such immune responses could be replicated or induced in HIV-1 infected patients, they might extend survival and reduce requirements for antiretroviral therapy.

HIV-2: the forgotten AIDS virus

HIV type 2 (HIV-2), a closely related retrovirus discovered a few years after HIV type 1, causes AIDS in only a minority of infected individuals. Determining why HIV-2 causes asymptomatic infection in most patients could further our understanding of HIV immunopathogenesis. Studies to date have suggested that both enhanced immune responses and lower viral replication could play a role. We summarize the important findings to date and highlight areas that warrant further exploration.

HIV immunopathogenesis and strategies for intervention

Therapeutic options aimed at tackling the HIV pandemic face many obstacles. The lack of readily accessible and affordable therapies means that most of those affected go untreated. The array of escape mechanisms used by HIV has undermined the efficiency of many antiviral products and continually represents a barrier to the development of an effective vaccine. Recent developments have seen a shift away from a cytopathic viral model of HIV pathogenesis towards the crucial role of immunopathogenic features--notably generalised immune activation--in the development of AIDS. As conventional vaccine strategies have sought to promote viral neutralisation and suppressive cellular responses, novel strategies that aim to address HIV immunopathogenesis should be sought. We review current opinion on HIV-induced pathogenic immune activation and strategies aimed at eliminating HIV, including a potential role for non-neutralising antibodies as part of a therapeutic vaccine option.