Host genetics of HIV-1 susceptibility

Genetic variation in the promoter region of pro-inflammatory cytokine TNF-α in perinatal HIV transmission from Mumbai, India

Various host factors such as cytokines and HLA, regulate the immune system and influence HIV transmission to infants exposed to HIV-1 through their mothers. Tumor Necrosis Factor Alpha (TNF-α) is a strong pro-inflammatory mediator and thought to influence vulnerability to HIV infection (and/or) transmission. Polymorphisms in regulatory regions are known to govern the production of this cytokine. However, the association of these variations in perinatal HIV transmission is yet to be established. Present study aimed to evaluate if polymorphisms in promoter region of TNF-α gene is associated with perinatal HIV transmission. With informed consent from parents, infants' blood was collected for HIV screening and SNPs analysis at 2 loci: TNF (rs1800629) and TNF (rs361525) using PCR-SSP method. HIV positive (n = 27) and negative (n = 54) children at the end of 18th month follow up were considered for this study. GG genotype, responsible for low expression of TNF (rs1800629) was significantly (p = 0.005) higher in uninfected children, while higher GA genotype frequency was observed in infected children. The 'G' allele frequency was significantly higher in negative children (p = 0.016). We conclude that genotypic variants of TNF (rs1800629) are a likely contributor to perinatal HIV transmission. This provides new insights in markers of differential susceptibility to perinatal HIV transmission.

Host genetic factors associated with symptomatic primary HIV infection and disease progression among Argentinean seroconverters

BACKGROUND

Variants in HIV-coreceptor C-C chemokine receptor type 5 (CCR5) and Human leukocyte antigen (HLA) genes are the most important host genetic factors associated with HIV infection and disease progression. Our aim was to analyze the association of these genetic factors in the presence of clinical symptoms during Primary HIV Infection (PHI) and disease progression within the first year.

METHODS

Seventy subjects diagnosed during PHI were studied (55 symptomatic and 15 asymptomatic). Viral load (VL) and CD4 T-cell count were evaluated. HIV progression was defined by presence of B or C events and/or CD4 T-cell counts <350 cell/mm3. CCR5 haplotypes were characterized by polymerase chain reaction and SDM-PCR-RFLP. HLA-I characterization was performed by Sequencing.

RESULTS

Symptoms during PHI were significantly associated with lower frequency of CCR5-CF1 (1.8% vs. 26.7%, p = 0.006). Rapid progression was significantly associated with higher frequency of CCR5-CF2 (16.7% vs. 0%, p = 0.024) and HLA-A*11 (16.7% vs. 1.2%, p = 0.003) and lower frequency of HLA-C*3 (2.8% vs. 17.5%, p = 0.035). Higher baseline VL was significantly associated with presence of HLA-A*11, HLA-A*24, and absence of HLA-A*31 and HLA-B*57. Higher 6-month VL was significantly associated with presence of CCR5-HHE, HLA-A*24, HLA-B*53, and absence of HLA-A*31 and CCR5-CF1. Lower baseline CD4 T-cell count was significantly associated with presence of HLA-A*24/*33, HLA-B*53, CCR5-CF2 and absence of HLA-A*01/*23 and CCR5-HHA. Lower 6-month CD4 T-cell count was associated with presence of HLA-A*24 and HLA-B*53, and absence of HLA-A*01 and HLA-B*07/*39. Moreover, lower 12-month CD4 T-cell count was significantly associated with presence of HLA-A*33, HLA-B*14, HLA-C*08, CCR5-CF2, and absence of HLA-B*07 and HLA-C*07.

CONCLUSION

Several host factors were significantly associated with disease progression in PHI subjects. Most results agree with previous studies performed in other groups. However, some genetic factor associations are being described for the first time, highlighting the importance of genetic studies at a local level.

Common genetic variation and the control of HIV-1 in humans

To extend the understanding of host genetic determinants of HIV-1 control, we performed a genome-wide association study in a cohort of 2,554 infected Caucasian subjects. The study was powered to detect common genetic variants explaining down to 1.3% of the variability in viral load at set point. We provide overwhelming confirmation of three associations previously reported in a genome-wide study and show further independent effects of both common and rare variants in the Major Histocompatibility Complex region (MHC). We also examined the polymorphisms reported in previous candidate gene studies and fail to support a role for any variant outside of the MHC or the chemokine receptor cluster on chromosome 3. In addition, we evaluated functional variants, copy-number polymorphisms, epistatic interactions, and biological pathways. This study thus represents a comprehensive assessment of common human genetic variation in HIV-1 control in Caucasians.

Pharmacogenetics of Anti-HIV Drugs

Pharmacogenetics holds promise in HIV treatment because of the complexity and potential toxicity of multidrug therapies that are prescribed for long periods. Thus far, few candidate genes have been examined for a limited number of allelic variants, but a number of confirmed associations have already emerged. A change in paradigm emerges from the availability of the HapMap, the wealth of data on less-common genetic polymorphisms, and new genotyping technology. This review presents a comprehensive analysis of the existing literature on pharmacogenetic determinants of antiretroviral drug exposure, drug toxicity, as well as genetic markers associated with the rate of disease progression. It is expected that larger-scale comprehensive genome approaches will profoundly change the landscape of knowledge in the future.

HIV controllers: how do they tame the virus?

HIV controllers are rare, chronically HIV-1-infected patients in whom viral replication is undetectable in the absence of antiretroviral treatment. Most such patients are nonetheless infected by replication-competent viruses. An effective, multifunctional HIV-specific CD8(+) T-cell response is thought to be central to viral control in these individuals. The mechanisms underlying this spontaneous control of HIV infection and the particular characteristics of the CD8(+) T-cell response in HIV controllers are the focus of intensive investigations, because they should help to unravel the pathogenesis of AIDS and to provide new clues for the design of effective vaccine strategies. In this review, we examine recent findings from these studies.

A whole-genome association study of major determinants for host control of HIV-1

Understanding why some people establish and maintain effective control of HIV-1 and others do not is a priority in the effort to develop new treatments for HIV/AIDS. Using a whole-genome association strategy, we identified polymorphisms that explain nearly 15% of the variation among individuals in viral load during the asymptomatic set-point period of infection. One of these is found within an endogenous retroviral element and is associated with major histocompatibility allele human leukocyte antigen (HLA)-B*5701, whereas a second is located near the HLA-C gene. An additional analysis of the time to HIV disease progression implicated two genes, one of which encodes an RNA polymerase I subunit. These findings emphasize the importance of studying human genetic variation as a guide to combating infectious agents.

Genomics meets HIV-1

Genomics is now a core element in the effort to develop a vaccine against HIV-1. Thanks to unprecedented progress in high-throughput genotyping and sequencing, in knowledge about genetic variation in humans, and in evolutionary genomics, it is finally possible to systematically search the genome for common genetic variants that influence the human response to HIV-1. The identification of such variants would help to determine which aspects of the response to the virus are the most promising targets for intervention. However, a key obstacle to progress remains the scarcity of appropriate human cohorts available for genomic research.

HIV/AIDS epidemiology, pathogenesis, prevention, and treatment

The HIV-1 pandemic is a complex mix of diverse epidemics within and between countries and regions of the world, and is undoubtedly the defining public-health crisis of our time. Research has deepened our understanding of how the virus replicates, manipulates, and hides in an infected person. Although our understanding of pathogenesis and transmission dynamics has become more nuanced and prevention options have expanded, a cure or protective vaccine remains elusive. Antiretroviral treatment has transformed AIDS from an inevitably fatal condition to a chronic, manageable disease in some settings. This transformation has yet to be realised in those parts of the world that continue to bear a disproportionate burden of new HIV-1 infections and are most affected by increasing morbidity and mortality. This Seminar provides an update on epidemiology, pathogenesis, treatment, and prevention interventions pertinent to HIV-1.

Cellular cofactors and HIV-1 infection in vivo

Recent studies have demonstrated that substantial levels of HIV-1 replication occur in vivo in what appear to be ‘resting’ CD4+ T lymphocytes. This contrasts with numerous studies in vitro, in which resting T cells are not permissive for productive infection as a result of a number of barriers to infection, particularly during the early stages of the viral life cycle. The barriers in vitro are likely to be the result of limiting levels of cellular cofactors that mediate viral replication, and these cofactors are apparently present at adequate levels in resting cells in vivo. Although a number of HIV-1 cofactors are now known, it is important to identify additional cofactors and to characterize the expression pattern and mechanisms that regulate cofactor function in infected CD4+ T lymphocytes in vivo. It may ultimately become possible to manipulate the expression levels of essential HIV-1 cofactors in vivo and thereby recapitulate for therapeutic benefit the barriers to infection that exist in resting T cells in vitro.