Distribution of chemokine receptor CCR2 and CCR5 genotypes and their relative contribution to human immunodeficiency virus type 1 (HIV-1) seroconversion, early HIV-1 RNA concentration in plasma, and later disease progression

CCR5 Promoter Polymorphism -2459G > A: Forgotten or Ignored?

C-C chemokine receptor 5 (CCR5) polymorphisms, particularly a 32-base pair deletion (∆32) in the open reading frame and −2459G > A in the promoter, are well known for their associations with HIV-1 infection and/or disease progression in a variety of studies. In this era of an HIV cure, where all the emphasis is on ∆32, it seems that −2459G > A has been forgotten or ignored. There is significant importance in the incorporation of the CCR5 −2459G > A genotype information into studies evaluating new immunologic and chemotherapeutic strategies, and those designing and implementing better treatment strategies with current antiretroviral therapy, doing so would enable a better understanding of the response to the intervention, due to a mechanistic or constitutive explanation. Until we find a strategy, whether a stem-cell transplantation or CCR5 editing approach or something else, that delivers a cure to the millions, we should make use of every piece of information that may help curtail HIV/AIDS as a threat to public health.

Cis-regulatory genetic variants in the CCR5 gene and natural HIV-1 control in black South Africans

Studies have investigated CCR5 haplotypes (HHA, HHB, HHC, HHD, HHE, HHF*1, HHF*2, HHG*1, HHG*2), defined by seven 5'UTR single nucleotide polymorphisms (SNPs), CCR2-V64I and CCR5Δ32, in HIV-1 disease. CCR5 cis-regulatory regions were sequenced, CCR2-V64I and CCR5Δ32 genotyped, and compared in HIV-1-infected black South Africans: 71 HIV-1 controllers (23 elite controllers, 37 viraemic controllers (VCs), 11 high viral load long-term non-progressors) and 74 progressors. The HHE haplotype and 3'UTR +2919 T > G SNP heterozygosity were underrepresented in total controllers and VCs vs. progressors (p = .004; p = .007 and p = .002, p_bonferroni = 0.032; p = .004, respectively). Possession of the +2919 T > G SNP (dominant mode) was associated with HIV-1 progression (controllers vs. progressors: p = .001, p_bonferroni = 0.016). The +2919 T > G SNP is in linkage disequilibrium (LD; r² = 0.73) with two 5'UTR SNPs (-2459G > A and -2135 T > C; r² = 1: 5'UTR-2SNP-hap). The 5'UTR-2SNP-hap was lower in total controllers and VCs vs. progressors (p = .003, p_bonferroni = 0.048; p = .01, respectively). Results suggest -2459G > A, -2135 T > C, and + 2919 T > G as key CCR5 variants in HIV-1 control.

Evolution of Host Target Cell Specificity During HIV-1 Infection

BACKGROUND

Many details of HIV-1 molecular virology have been translated into lifesaving antiviral drugs. Yet, we have an incomplete understanding of the cells in which HIV-1 replicates in untreated individuals and persists in during antiretroviral therapy.

METHODS

In this review we discuss how viral entry phenotypes have been characterized and the insights they have revealed about the target cells supporting HIV-1 replication. In addition, we will examine whether some HIV-1 variants have the ability to enter cells lacking CD4 (such as astrocytes) and the role that trans-infection plays in HIV-1 replication.

RESULTS

HIV-1 entry into a target cell is determined by whether the viral receptor (CD4) and the coreceptor (CCR5 or CXCR4) are expressed on that cell. Sustained HIV-1 replication in a cell type can produce viral lineages that are tuned to the CD4 density and coreceptor expressed on those cells; a fact that allows us to use Env protein entry phenotypes to infer information about the cells in which a viral lineage has been replicating and adapting.

CONCLUSION

We now recognize that HIV-1 variants can be divided into three classes representing the primary target cells of HIV-1; R5 T cell-tropic variants that are adapted to entering memory CD4+ T cells, X4 T cell-tropic variants that are adapted to entering naïve CD4+ T cells and Mtropic variants that are adapted to entering macrophages and possibly other cells that express low levels of CD4. While much progress has been made, the relative contribution that infection of different cell subsets makes to viral pathogenesis and persistence is still being unraveled.

CCR5 Revisited: How Mechanisms of HIV Entry Govern AIDS Pathogenesis

The chemokine receptor CCR5 has been the focus of intensive studies since its role as a coreceptor for HIV entry was discovered in 1996. These studies lead to the development of small molecular drugs targeting CCR5, with maraviroc becoming in 2007 the first clinically approved chemokine receptor inhibitor. More recently, the apparent HIV cure in a patient transplanted with hematopoietic stem cells devoid of functional CCR5 rekindled the interest for inactivating CCR5 through gene therapy and pharmacological approaches. Fundamental research on CCR5 has also been boosted by key advances in the field of G-protein coupled receptor research, with the realization that CCR5 adopts a variety of conformations, and that only a subset of these conformations may be targeted by chemokine ligands. In addition, recent genetic and pathogenesis studies have emphasized the central role of CCR5 expression levels in determining the risk of HIV and SIV acquisition and disease progression. In this article, we propose to review the key properties of CCR5 that account for its central role in HIV pathogenesis, with a focus on mechanisms that regulate CCR5 expression, conformation, and interaction with HIV envelope glycoproteins.

Haplotypes in CCR5-CCR2, CCL3 and CCL5 are associated with natural resistance to HIV-1 infection in a Colombian cohort

INTRODUCTION

Variants in genes encoding for HIV-1 co-receptors and their natural ligands have been individually associated to natural resistance to HIV-1 infection. However, the simultaneous presence of these variants has been poorly studied.

OBJECTIVE

To evaluate the association of single and multilocus haplotypes in genes coding for the viral co-receptors CCR5 and CCR2, and their ligands CCL3 and CCL5, with resistance or susceptibility to HIV-1 infection.

MATERIALS AND METHODS

Nine variants in CCR5-CCR2, two SNPs in CCL3 and two in CCL5 were genotyped by PCR-RFLP in 35 seropositive (cases) and 49 HIV-1-exposed seronegative Colombian individuals (controls). Haplotypes were inferred using the Arlequin software, and their frequency in individual or combined loci was compared between cases and controls by the chi-square test. A p' value ;0.05 after Bonferroni correction was considered significant.

RESULTS

Homozygosis of the human haplogroup (HH) E was absent in controls and frequent in cases, showing a tendency to susceptibility. The haplotypes C-C and T-T in CCL3 were associated with susceptibility (p'=0.016) and resistance (p';0.0001) to HIV-1 infection, respectively. Finally, in multilocus analysis, the haplotype combinations formed by HHC in CCR5-CCR2, T-T in CCL3 and G-C in CCL5 were associated with resistance (p'=0.006).

CONCLUSION

Our results suggest that specific combinations of variants in genes from the same signaling pathway can define an HIV-1 resistant phenotype. Despite our small sample size, our statistically significant associations suggest strong effects; however, these results should be further validated in larger cohorts.

CCR5 promoter activity correlates with HIV disease progression by regulating CCR5 cell surface expression and CD4 T cell apoptosis

CCR5 is the major co-receptor for HIV and polymorphisms in the CCR5 gene as well as promoter region that alter cell surface expression have been associated with disease progression. We determined the relationship between CCR5 promoter polymorphisms and CD4 decline and other immunopathological features like immune activation and CD4+ T cell apoptosis in HIV patients. CCR5 promoter haplotype HHC was significantly associated with higher CD4 counts in patients. The relative promoter activity (RPA) of each haplotype was determined in vitro and combined promoter activity based on both alleles (CRPA) was assigned to each patients. Interestingly, CCR5 CRPA correlated inversely with CD4 counts and CD4:CD8 ratio specifically in viremic patients. In normal individuals, the CRPA correlated with the number of CCR5+ CD4+ T cells in the peripheral blood suggesting an effect on CCR5 expression. In a subset of high viremic patients harboring R5 tropic HIV, there was a strong correlation between CCR5 CRPA and both CD4 counts and CD4 T cell apoptosis. Our study demonstrates that, CCR5 promoter polymorphisms correlate with CD4 T cell loss possibly by regulating CD4 T cell apoptosis in HIV patients. Furthermore, assigning CRPAs to each patient is a new method of translating genotype to phenotype.

CCR2, CCR5, and CXCL12 variation and HIV/AIDS in Papua New Guinea

Polymorphisms in chemokine receptors, serving as HIV co-receptors, and their ligands are among the well-known host genetic factors associated with susceptibility to HIV infection and/or disease progression. Papua New Guinea (PNG) has one of the highest adult HIV prevalences in the Asia-Pacific region. However, information regarding the distribution of polymorphisms in chemokine receptor (CCR5, CCR2) and chemokine (CXCL12) genes in PNG is very limited. In this study, we genotyped a total of nine CCR2-CCR5 polymorphisms, including CCR2 190G >A, CCR5 -2459G >A and Δ32, and CXCL12 801G >A in PNG (n=258), North America (n=184), and five countries in West Africa (n=178). Using this data, we determined previously characterized CCR5 haplotypes. In addition, based on the previously reported associations of CCR2 190, CCR5 -2459, CCR5 open reading frame, and CXCL12 801 genotypes with HIV acquisition and/or disease progression, we calculated composite full risk scores, considering both protective as well as susceptibility effects of the CXCL12 801 AA genotype. We observed a very high frequency of the CCR5 -2459A allele (0.98) in the PNG population, which together with the absence of Δ32 resulted in a very high frequency of the HHE haplotype (0.92). These frequencies were significantly higher than in any other population (all P-values<0.001). Regardless of whether we considered the CXCL12 801 AA genotype protective or susceptible, the risk scores were significantly higher in the PNG population compared with any other population (all P-values<0.001). The results of this study provide new insights regarding CCR5 variation in the PNG population, and suggest that the collective variation in CCR2, CCR5, and CXCL12 may increase the risk of HIV/AIDS in a large majority of Papua New Guineans.

Epigenetic mechanisms, T-cell activation, and CCR5 genetics interact to regulate T-cell expression of CCR5, the major HIV-1 coreceptor

T-cell expression levels of CC chemokine receptor 5 (CCR5) are a critical determinant of HIV/AIDS susceptibility, and manifest wide variations (i) between T-cell subsets and among individuals and (ii) in T-cell activation-induced increases in expression levels. We demonstrate that a unifying mechanism for this variation is differences in constitutive and T-cell activation-induced DNA methylation status of CCR5 cis-regulatory regions (cis-regions). Commencing at an evolutionarily conserved CpG (CpG -41), CCR5 cis-regions manifest lower vs. higher methylation in T cells with higher vs. lower CCR5 levels (memory vs. naïve T cells) and in memory T cells with higher vs. lower CCR5 levels. HIV-related and in vitro induced T-cell activation is associated with demethylation of these cis-regions. CCR5 haplotypes associated with increased vs. decreased gene/surface expression levels and HIV/AIDS susceptibility magnify vs. dampen T-cell activation-associated demethylation. Methylation status of CCR5 intron 2 explains a larger proportion of the variation in CCR5 levels than genotype or T-cell activation. The ancestral, protective CCR5-HHA haplotype bears a polymorphism at CpG -41 that is (i) specific to southern Africa, (ii) abrogates binding of the transcription factor CREB1 to this cis-region, and (iii) exhibits a trend for overrepresentation in persons with reduced susceptibility to HIV and disease progression. Genotypes lacking the CCR5-Δ32 mutation but with hypermethylated cis-regions have CCR5 levels similar to genotypes heterozygous for CCR5-Δ32. In HIV-infected individuals, CCR5 cis-regions remain demethylated, despite restoration of CD4+ counts (≥800 cells per mm(3)) with antiretroviral therapy. Thus, methylation content of CCR5 cis-regions is a central epigenetic determinant of T-cell CCR5 levels, and possibly HIV-related outcomes.

Immunogenetic influences on acquisition of HIV-1 infection: consensus findings from two African cohorts point to an enhancer element in IL19 (1q32.2)

Numerous reports have suggested that immunogenetic factors may influence HIV-1 acquisition, yet replicated findings that translate between study cohorts remain elusive. Our work aimed to test several hypotheses about genetic variants within the IL10-IL24 gene cluster that encodes interleukin (IL)-10, IL-19, IL-20, and IL-24. In aggregated data from 515 Rwandans and 762 Zambians with up to 12 years of follow-up, 190 single nucleotide polymorphisms (SNPs) passed quality control procedures. When HIV-1-exposed seronegative subjects (n = 486) were compared with newly seroconverted individuals (n = 313) and seroprevalent subjects (n = 478) who were already infected at enrollment, rs12407485 (G>A) in IL19 showed a robust association signal in adjusted logistic regression models (odds ratio = 0.64, P = 1.7 × 10⁻⁴, and q = 0.033). Sensitivity analyses demonstrated that (i) results from both cohorts and subgroups within each cohort were highly consistent; (ii) verification of HIV-1 infection status after enrollment was critical; and (iii) supporting evidence was readily obtained from Cox proportional hazards models. Data from public databases indicate that rs12407485 is part of an enhancer element for three transcription factors. Overall, these findings suggest that molecular features at the IL19 locus may modestly alter the establishment of HIV-1 infection.

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.

Dynamics of viremia in primary HIV-1 infection in Africans: insights from analyses of host and viral correlates

In HIV-1 infection, plasma viral load (VL) has dual implications for pathogenesis and public health. Based on well-known patterns of HIV-1 evolution and immune escape, we hypothesized that VL is an evolving quantitative trait that depends heavily on duration of infection (DOI), demographic features, human leukocyte antigen (HLA) genotypes and viral characteristics. Prospective data from 421 African seroconverters with at least four eligible visits did show relatively steady VL beyond 3 months of untreated infection, but host and viral factors independently associated with cross-sectional and longitudinal VL often varied by analytical approaches and sliding time windows. Specifically, the effects of age, HLA-B(⁎)53 and infecting HIV-1 subtypes (A1, C and others) on VL were either sporadic or highly sensitive to time windows. These observations were strengthened by the addition of 111 seroconverters with 2-3 eligible VL results, suggesting that DOI should be a critical parameter in epidemiological and clinical studies.

Influence of CCR5 and CCR2 genetic variants in the resistance/susceptibility to HIV in serodiscordant couples from Colombia

The main genetic factor related to HIV-1 resistance is the CCR5-Δ32 mutation; however, the homozygous genotype is uncommon. The CCR5-Δ32 mutation along with single nucleotide polymorphisms (SNPs) in the CCR5 promoter and the CCR2-V64I mutation have been included in seven human haplogroups (HH) previously associated with resistance/susceptibility to HIV-1 infection and different rates of AIDS progression. Here, we determined the association of the CCR5 promoter SNPs, the CCR5-Δ32 mutation, CCR2-V64I SNP, and HH frequencies with resistance/susceptibility to HIV-1 infection in a cohort of HIV-1-serodiscordant couples from Colombia. Seventy HIV-1-exposed, but seronegative (HESN) individuals, 57 seropositives (SP), and 112 healthy controls (HC) were included. The CCR5-Δ32 mutation and CCR2-V64I SNP were identified by PCR, and the CCR5 promoter SNPs were evaluated by sequencing. None of the individuals exhibited a homozygous Δ32 genotype; the CCR2-I allele was more frequent in HESN (34%) than HC (23%) (p=0.039, OR=1.672). The frequency of the 29G allele was higher in SP than HC (p=0.003, OR=3). HHF2 showed a higher frequency in HC (19%) than SP (9%) (p=0.027), while HHG1 was more frequent in SP (11.1%) than in HC (4.2%) (p=0.019). The AGACCAC-CCR2-I-CCR5 wild-type haplotype showed a higher frequency in SP (14.2%) than in HC (3.7%) (p=0.001). In conclusion, the CCR5-Δ32 allele is not responsible for HIV-1 resistance in this HESN group; however, the CCR2-I allele could be protective, while the 29G allele might increase the likelihood of acquiring HIV-1 infection. HHG1 and the AGACCAC-CCR2-I-CCR5 wild-type haplotype might promote HIV-1 infection while HHF2 might be related to resistance. However, additional studies are required to evaluate the implications of these findings.

Impact of CCR2 and SDF1 polymorphisms on disease progression in HIV-infected subjects in Thailand

BACKGROUND

The genotypic polymorphisms of CCR5, CCR2, and SDF1 were analyzed to determine their impact as potential confounders with regard to disease progression because of the role that host genetic factors appear to be involved in determining rates of disease progression.

METHODS

Genomic DNA was extracted from Ethylenediaminetetraacetate whole blood using Qiagen DNA extraction kit. The amplification of CCR5, CCR2, and SDF1 genes was performed by PCR.

RESULTS

Two hundred and twenty-one samples were genotyped for the CCR5, CCR2, and SDF1 mutation. Among these, all (100%) were identified as wild type for CCR5. All were then investigated considering the impact on CD4+ T-cell counts. Samples were divided into two groups based on the CD4+ T-cell numbers. It revealed that in the group of CD4+ T-cell counts ≥200 cells/μl, 15 were found for the homozygous for SDF1 gene (3'A/3'A) whereas one was found in the group of CD4+ T-cell counts <200 cells/μl. Homozygosity for the CCR2 polymorphisms (64I/64I) were five in the group of CD4+ T-cell counts ≥200 cells/μl and none were found in the group of CD4+ T-cell counts <200 cells/μl. These results demonstrated that there was a significant association between CD4+ T-cell numbers and CCR2 and SDF1 polymorphisms (P < 0.001).

CONCLUSIONS

The mutation of CCR2 and SDF1 genes showed a significant difference in the distribution of CD4+ T-cell numbers (P < 0.001) whereas mutation of chemokine coreceptor CCR5 was not appeared to be associated with the impact of CD4+ T-cell counts.

Associations of human leukocyte antigen-G with resistance and susceptibility to HIV-1 infection in the Pumwani sex worker cohort

OBJECTIVE

To determine the association between human leukocyte antigens (HLA)-G genotypes and resistance or susceptibility to HIV-1.

DESIGN

A group of sex workers in Pumwani, Kenya can be epidemiologically defined as resistant to HIV-1 infection despite frequent exposure and provide an example of natural protective immunity. HLA class I and II molecules have been shown to be associated with resistance/susceptibility to infection in this cohort. HLA-G is a nonclassical class I allele that is primarily involved in mucosal and inflammatory response, which is of interest in HIV-1 resistance.

METHODS

In this study, we used a sequence-based typing method to genotype HLA-G for 667 women enrolled in this cohort and examined the influence of HLA-G genotypes on resistance or susceptibility to HIV-1 infection.

RESULTS

The G*01 : 01:01 genotype was significantly enriched in the HIV-1-resistant women [P = 0.002, Odds ratio: 2.11, 95% confidence interval (CI): 0.259-0.976], whereas the G*01 : 04:04 genotype was significantly associated with susceptibility to HIV-1 infection (P = 0.039, OR:0.502, 95% CI:0.259-0.976). Kaplan-Meier survival analysis correlated with these results. G*01 : 01:01 genotype was associated with significantly lower rate of seroconversion (P = 0.001). Whereas, G*01 : 04:04 genotype was significantly associated with an increased rate of seroconversion (P = 0.013). The associations of these HLA-G alleles are independent of other HLA class I and II alleles identified in this population.

CONCLUSION

Our study showed that specific HLA-G alleles are associated with resistance or susceptibility to HIV-1 acquisition in this high-risk population. Further studies are needed to understand its functional significance in HIV-1 transmission.

HIV-1 dynamics: a reappraisal of host and viral factors, as well as methodological issues

The dynamics of HIV-1 viremia is a complex and evolving landscape with clinical and epidemiological (public health) implications. Most studies have relied on the use of set-point viral load (VL) as a readily available proxy of viral dynamics to assess host and viral correlates. This review highlights recent findings from population-based studies of set-point VL, focusing primarily on robust data related to host genetics. A comprehensive understanding of viral dynamics will clearly need to consider both host and viral characteristics, with close attention to (i) the timing of VL measurements, (ii) the biology of viral evolution, (iii) compartments of active viral replication, (iv) the transmission source partner as the immediate past microenvironment, and (v) proper application of statistical models.

Genetic correlates influencing immunopathogenesis of HIV infection

Variability to HIV infection, its progression as well as responsiveness to antiretroviral therapy (ART) is observed among individuals including viraemia controllers or exposed uninfected, rapid versus slow progressors and ART responders compared to non responders. This differential responsiveness/vulnerability to HIV-1 is governed by multiple host genetic factors that include HLA, cytokines, chemokines, their receptors and others. This review highlights the influence of these genetic factors on HIV/AIDS outcome; however, in India, the information in this area is very limited and most of these genetic studies have been conducted in Caucasian and South African populations. Considering, the population specific differences in the frequencies of protective or susceptibility favouring alleles and their influence on the disease outcome, it is of utmost importance to strengthen ongoing efforts towards defining largely unknown genetic propensity in Indian population, particularly by recruitment of large cohorts of well categorized exposed uninfected individuals, rapid, long term non progressors and elite viraemic controllers. Multi-parametric analysis of these potentially interactive immunogenetic variables in these cohorts may help to define potential targets for diagnostics and therapy in a population specific manner.

Human leukocyte antigen variants B*44 and B*57 are consistently favorable during two distinct phases of primary HIV-1 infection in sub-Saharan Africans with several viral subtypes

As part of an ongoing study of early human immunodeficiency virus type 1 (HIV-1) infection in sub-Saharan African countries, we have identified 134 seroconverters (SCs) with distinct acute-phase (peak) and early chronic-phase (set-point) viremias. SCs with class I human leukocyte antigen (HLA) variants B*44 and B*57 had much lower peak viral loads (VLs) than SCs without these variants (adjusted linear regression beta values of -1.08 ± 0.26 log(10) [mean ± standard error] and -0.83 ± 0.27 log(10), respectively; P < 0.005 for both), after accounting for several nongenetic factors, including gender, age at estimated date of infection, duration of infection, and country of origin. These findings were confirmed by alternative models in which major viral subtypes (A1, C, and others) in the same SCs replaced country of origin as a covariate (P ≤ 0.03). Both B*44 and B*57 were also highly favorable (P ≤ 0.03) in analyses of set-point VLs. Moreover, B*44 was associated with relatively high CD4(+) T-cell counts during early chronic infection (P = 0.02). Thus, at least two common HLA-B variants showed strong influences on acute-phase as well as early chronic-phase VL, regardless of the infecting viral subtype. If confirmed, the identification of B*44 as another favorable marker in primary HIV-1 infection should help dissect mechanisms of early immune protection against HIV-1 infection.

Association of chemokine receptor gene (CCR2-CCR5) haplotypes with acquisition and control of HIV-1 infection in Zambians

Background

Polymorphisms in chemokine (C-C motif) receptors 2 and 5 genes (CCR2 and CCR5) have been associated with HIV-1 infection and disease progression. We investigated the impact of CCR2-CCR5 haplotypes on HIV-1 viral load (VL) and heterosexual transmission in an African cohort. Between 1995 and 2006, cohabiting Zambian couples discordant for HIV-1 (index seropositive and HIV-1 exposed seronegative {HESN}) were monitored prospectively to determine the role of host genetic factors in HIV-1 control and heterosexual transmission. Genotyping for eight CCR2 and CCR5 variants resolved nine previously recognized haplotypes. By regression and survival analytic techniques, controlling for non-genetic factors, we estimated the effects of these haplotypic variants on a) index partner VL, b) seroconverter VL, c) HIV-1 transmission by index partners, d) HIV-1 acquisition by HESN partners.

Results

Among 567 couples, 240 virologically linked transmission events had occurred through 2006. HHF*2 homozygosity was associated with significantly lower VL in seroconverters (mean beta = -0.58, log₁₀ P = 0.027) and the HHD/HHE diplotype was associated with significantly higher VL in the seroconverters (mean beta = 0.54, log₁₀ P = 0.014) adjusted for age and gender in multivariable model. HHD/HHE was associated with more rapid acquisition of infection by the HESNs (HR = 2.0, 95% CI = 1.20-3.43, P = 0.008), after adjustments for index partner VL and the presence of genital ulcer or inflammation in either partner in Cox multivariable models. The HHD/HHE effect was stronger in exposed females (HR = 2.1, 95% CI = 1.14-3.95, P = 0.018).

Conclusions

Among Zambian discordant couples, HIV-1 coreceptor gene haplotypes and diplotypes appear to modulate HIV-1 VL in seroconverters and alter the rate of HIV-1 acquisition by HESNs. These associations replicate or resemble findings reported in other African and European populations.

Concordance of CCR5 genotypes that influence cell-mediated immunity and HIV-1 disease progression rates

We used cutaneous delayed-type hypersensitivity responses, a powerful in vivo measure of cell-mediated immunity, to evaluate the relationships among cell-mediated immunity, AIDS, and polymorphisms in CCR5, the HIV-1 coreceptor. There was high concordance between CCR5 polymorphisms and haplotype pairs that influenced delayed-type hypersensitivity responses in healthy persons and HIV disease progression. In the cohorts examined, CCR5 genotypes containing -2459G/G (HHA/HHA, HHA/HHC, HHC/HHC) or -2459A/A (HHE/HHE) associated with salutary or detrimental delayed-type hypersensitivity and AIDS phenotypes, respectively. Accordingly, the CCR5-Δ32 allele, when paired with non-Δ32-bearing haplotypes that correlate with low (HHA, HHC) versus high (HHE) CCR5 transcriptional activity, associates with disease retardation or acceleration, respectively. Thus, the associations of CCR5-Δ32 heterozygosity partly reflect the effect of the non-▵32 haplotype in a background of CCR5 haploinsufficiency. The correlations of increased delayed-type hypersensitivity with -2459G/G-containing CCR5 genotypes, reduced CCR5 expression, decreased viral replication, and disease retardation suggest that CCR5 may influence HIV infection and AIDS, at least in part, through effects on cell-mediated immunity.

Persistent arthralgia induced by Chikungunya virus infection is associated with interleukin-6 and granulocyte macrophage colony-stimulating factor

Background. Chikungunya virus (CHIKV) infection induces arthralgia. The involvement of inflammatory cytokines and chemokines has been suggested, but very little is known about their secretion profile in CHIKV-infected patients.

Methods. A case-control longitudinal study was performed that involved 30 adult patients with laboratory-confirmed Chikungunya fever. Their profiles of clinical disease, viral load, and immune mediators were investigated.

Results. When patients were segregated into high viral load and low viral load groups during the acute phase, those with high viremia had lymphopenia, lower levels of monocytes, neutrophilia, and signs of inflammation. The high viral load group was also characterized by a higher production of pro-inflammatory cytokines, such as interferon-α and interleukin (IL)–6, during the acute phase. As the disease progressed to the chronic phase, IL-17 became detectable. However, persistent arthralgia was associated with higher levels of IL-6 and granulocyte macrophage colony-stimulating factor, whereas patients who recovered fully had high levels of Eotaxin and hepatocyte growth factor.

Conclusions. The level of CHIKV viremia during the acute phase determined specific patterns of pro-inflammatory cytokines, which were associated with disease severity. At the chronic phase, levels of IL-6, and granulocyte macrophage colony-stimulating factor found to be associated with persistent arthralgia provide a possible explanation for the etiology of arthralgia that plagues numerous CHIKV-infected patients.

Determinants of protection among HIV‐exposed seronegative persons: an overview

Both clinical experience and a growing medical literature indicate that some persons who have been exposed to human immunodeficiency virus (HIV) infection remain uninfected. Although in some instances this may represent good fortune, cohorts of uninfected persons have been reported who are considered at high risk for infection. In these cohorts a variety of characteristics have been proposed as mediating protection, but to date only the 32&#x2013;base pair deletion in the chemokine (C&#x2010;C motif) receptor 5 gene, which results in complete failure of cell surface expression of this coreceptor, has been associated with high&#x2010;level protection from HIV infection. With this in mind, there are probably many other factors that may individually or in combination provide some level of protection from acquisition of HIV infection. Because some of these factors are probably incompletely protective or inconsistently active, identifying them with confidence will be difficult. Nonetheless, clarifying the determinants of protection against HIV infection is a high priority that will require careful selection of high&#x2010;risk uninfected cohorts, who should undergo targeted studies of plausible mediators and broad screening for unexpected determinants of protection.

Immunogenetic basis of HIV-1 infection, transmission and disease progression

Susceptibility to HIV-1 infection and rate of disease progression to AIDS are complex traits modulated by environmental and genetic factors. Studies on large AIDS cohorts and their meta-analyses have identified numerous AIDS restriction genes that regulate HIV cell entry (particularly chemokine co-receptors and their ligands), acquired and innate immunity (major histocompatibility complex (MHC), killer immunoglobulin-like receptors (KIRs), and cytokines) and others that influence outcome of HIV infection. However, vast inter-individual variability is often observed and some rare individuals like 'long-term non-progressors (LTNPs) or exposed uninfected' (EUs) appear to be protected due to natural resistance. A better understanding of genetic basis of such a 'natural resistance' to infection would bear important implications in designing therapeutic vaccine designs. The genetic variants that could limit AIDS vary in different populations. We have studied genetic variations in the MHC, cytokines and CCR2-CCR5 loci in the Asian-Indian HIV-infected population and compared with other global populations.

CCR5 haplotypes and mother-to-child HIV transmission in Malawi

Background

CCR5 and CCR2 gene polymorphisms (SNPs) have been associated with protection against HIV transmission in adults and with delayed progression to AIDS. The CCR5 Δ32 deletion and SNP -2459G are associated with reduced expression of the CCR5 protein.

Methodology/Principal Findings

We investigated the association between infant CCR2/CCR5 diplotype and HIV mother to child transmission (MTCT) in Malawi. Blood samples from infants (n = 552) of HIV positive women who received nevirapine were genotyped using a post-PCR multiplex ligase detection reaction and haplotypes were identified based on 8 CCR2/CCR5 SNPs and the open reading frame 32 base pair deletion. Following verification of Hardy-Weinberg equilibrium, log linear regression was performed to examine the association between mutations and MTCT. Overall, protection against MTCT was weakly associated with two CCR5 SNPs, -2459G (Risk ratio [RR], 0.78; confidence interval [CI], 0.54–1.12), and the linked CCR5 -2135T (RR, 0.78; CI, 0.54–1.13). No child carried the CCR5 Δ32 SNP. Maternal Viral Load (MVL) was found to be an effect measure modifier. Among mothers with low MVL, statistically significant protection against MTCT was observed for -2459G (RR, 0.50; CI, 0.27–0.91), and -2135T (RR, 0.51; CI, 0.28–0.92). Statistically significant protection was not found at high MVL.

Conclusions/Significance

Results from this study suggest that CCR5 SNPs -2459G and -2135T associated with reduced receptor expression protect against MTCT of HIV at low MVLs, whereas high MVLs may over-ride differences in coreceptor availability.

HIV Type 1 Superinfection with a Dual-Tropic Virus and Rapid Progression to AIDS: A Case Report

BACKGROUND

The occurrence of human immunodeficiency virus type 1 (HIV-1) superinfection has implications for vaccine development and our understanding of HIV pathogenesis and transmission.

METHODS AND RESULTS

We describe a subject from the Multicenter AIDS Cohort Study who was superinfected with a dual-tropic (CXCR4/CCR5-utilizing) HIV-1 subtype B strain between 0.8 and 1.3 years after seroconversion who had rapid progression to AIDS; the subject developed Pneumocystis pneumonia 3.4 years after seroconversion, as well as multiple other opportunistic infections. The superinfecting strain rapidly became the predominant population virus, suggesting that the initial and superinfecting viruses in this individual differed in virulence. However, we found no molecular epidemiological evidence in the HIV database to suggest that this strain had been found in other individuals. In addition, this subject's HIV-1 viral load and pattern of human leukocyte antigen and coreceptor polymorphisms only partially explained his rapid disease progression.

CONCLUSIONS

Additional studies are needed to determine whether superinfection itself and/or infection with a dual-tropic virus causes rapid disease progression, or whether certain individuals who are innately more susceptible to rapid disease progression also lack the ability to resist the challenge of a second infection. This case appears to support the latter hypothesis.

CCL3L1 and CCL4L1: variable gene copy number in adolescents with and without human immunodeficiency virus type 1 (HIV-1) infection

As members of the chemokine family, macrophage inflammatory protein 1 alpha (MIP-1alpha) and MIP-1beta are unique in that they both consist of non-allelic isoforms encoded by different genes, namely chemokine (C-C motif) ligand 3 (CCL3), CCL4, CCL3-like 1 (CCL3L1) and CCL4L1. The products of these genes and of CCL5 (encoding RANTES, i.e., regulated on activation, normal T expressed and secreted) can block or interfere with human immunodeficiency virus type 1 (HIV-1) infection through competitive binding to chemokine (C-C motif) receptor 5 (CCR5). Our analyses of 411 adolescents confirmed that CCL3 and CCL4 genes occurred invariably as single copies (two per diploid genome), whereas the copy numbers of CCL3L1 and CCL4L1 varied extensively (0-11 and 1-6 copies, respectively). Neither CCL3L1 nor CCL4L1 gene copy number variation showed appreciable impact on susceptibility to or control of HIV-1 infection. Within individuals, linear correlation between CCL3L1 and CCL4L1 copy numbers was moderate regardless of ethnicity (Pearson correlation coefficients=0.63-0.65, P<0.0001), suggesting that the two loci are not always within the same segmental duplication unit. Persistently low serum MIP-1alpha and MIP-1beta (in the pg/ml range) compared with high CCL5 concentration (ng/ml range) implied that multi-copy genes CCL3L1 and CCL4L1 conferred little advantage in the intensity of expression among uninfected or infected adolescents.

Understanding the recent evolution of the human genome: insights from human-chimpanzee genome comparisons

The sequencing of the chimpanzee genome and the comparison with its human counterpart have begun to reveal the spectrum of genetic changes that has accompanied human evolution. In addition to gross karyotypic rearrangements such as the fusion that formed human chromosome 2 and the human-specific pericentric inversions of chromosomes 1 and 18, there is considerable submicroscopic structural variation involving deletions, duplications, and inversions. Lineage-specific segmental duplications, detected by array comparative genomic hybridization and direct sequence comparison, have made a very significant contribution to this structural divergence, which is at least three-fold greater than that due to nucleotide substitutions. Since structural genomic changes may have given rise to irreversible functional differences between the diverging species, their detailed analysis could help to identify the biological processes that have accompanied speciation. To this end, interspecies comparisons have revealed numerous human-specific gains and losses of genes as well as changes in gene expression. The very considerable structural diversity (polymorphism) evident within both lineages has, however, hampered the analysis of the structural divergence between the human and chimpanzee genomes. The concomitant evaluation of genetic divergence and diversity at the nucleotide level has nevertheless served to identify many genes that have evolved under positive selection and may thus have been involved in the development of human lineage-specific traits. Genes that display signs of weak negative selection have also been identified and could represent candidate loci for complex genomic disorders. Here, we review recent progress in comparing the human and chimpanzee genomes and discuss how the differences detected have improved our understanding of the evolution of the human genome.

Polymorphism in the CCR5 gene promoter and HIV-1 infection in North Indians

The clinical course and outcome of human immunodeficiency virus-1 (HIV-1) infection are highly variable among individuals. CCR5 is the primary coreceptor that mediates entry of HIV-1 (R5) into permissive host cells. In this study, five SNPs (59029G/A, 59353T/C, 59356C/T, 59402A/G, and 59653C/T) in the promoter region and a deletion of 32 bp (Delta32) in the CCR5 gene were evaluated in 180 chronically HIV-1-infected North Indians. The study showed the following: (1) the protective CCR5 Delta32 allele was absent; (2) the frequency of CCR5*59402A allele in the HIV-infected people (66.4%) was higher than in healthy subjects (57.1%, p = 0.027) and in the CDC stage C patients (76%) versus stages A and B patients together (60%; p = 0.002); (3) homozygous CCR5*59402 AA genotype was significantly increased in the seropositive subjects (46.1%) compared with healthy control subjects (30.2%; p = 0.008) and in the CDC stage C patients (59.2%) compared with stage A and B subjects (37.6%, p = 0.007); and (4) an increased frequency of homozygous ACCAC haplotype was present in the seropositive stage C patients (32.4%) versus 15.6% in patients in stages A plus B (p = 0.013). These observations suggest an association of CCR5*59402A with increased likelihood of acquisition of HIV-1 and development of AIDS in the Asian Indian population. Further studies are required to confirm these findings and understand the effect of CCR5 polymorphisms on the outcome of HIV-1 infection.

High prevalence of the CCR5Delta32 HIV-resistance mutation among Estonian HIV type 1-infected individuals

The aim of this survey was to investigate human immunodeficiency virus type 1 (HIV-1) coreceptor, chemokine receptor 5 (CCR5), polymorphism among Estonian HIV-1-infected individuals. Homozygous CCR5Delta32 genotypes have been associated with resistance to HIV-1 infection; however, inconsistent evidence exists as to whether a single copy of a mutant allele among heterozygotes confers protection from HIV-1 infection. In an Estonian population the frequency of the CCR5Delta32 allele has been found to be among the greatest observed to date. Ironically, Estonia is concomitantly characterized by a very high HIV-1 prevalence. We compared the allele frequencies in a healthy control population to the HIV-positive group. The frequency of heterozygous individuals did not differ significantly between the HIV-positive group and the control population. Allele frequencies were analyzed among different risk groups as well as groups with different HIV genetic backgrounds. We did not find a difference between CCR5Delta32 allele frequencies among intravenous drug users (IDUs) and sexually infected persons. Likewise, the distribution of CCR5Delta32 allele frequencies among patients infected with different subtypes did not differ while data from "pure" subtypes A, B, and CRF06_cpx were pooled and evaluated against unique recombinant forms.

Acute Retroviral Syndrome

The acute retroviral syndrome (ARS), also known as primary HIV infection, acute HIV infection, and HIV seroconversion syndrome, is the earliest clinical manifestation of HIV infection. Early detection of HIV allows for medical and behavioral interventions critical to the management of HIV. This article reviews the clinical features and current management of individuals with ARS.

Genetics of resistance to HIV infection: Role of co-receptors and co-receptor ligands

Susceptibility to HIV infection and AIDS progression is variable among individuals and populations, and in part genetically determined. Genetic variants of genes encoding HIV co-receptors and their chemokine ligands have been described, and some of these variants were associated with resistance to HIV infection and/or disease progression. We review here the reported data regarding the variants of the CCR5, CCR2, CX3CR1, MIP-1alpha/CCL3, MIP-1beta/CCL4, RANTES/CCL5 and SDF-1/CXCL12 genes. The Delta32 deletion mutant of CCR5, resulting in a non-functional receptor not reaching the cell surface, is unambiguously associated with strong, although incomplete, resistance to HIV infection for homozygotes, and retarded progression for heterozygotes. Specific haplotypes encompassing the CCR5 and CCR2 loci, and the copy number of the CCL3L1 gene, have also been convincingly correlated with delayed progression. For other gene variants, involving CXCL12/SDF-1 and CX3CR1, conclusive evidence for their relevance in the frame of HIV susceptibility is still lacking.

Host genetics and viral infections: immunology taught by viruses, virology taught by the immune system

Viruses are prototypic obligate intracellular pathogens, and are therefore, by necessity, highly pre-adapted to surviving the host immune response. Nevertheless, host genetic factors remain an important determinant of disease outcome, particularly in the case of viruses that have encountered humans in the more recent past (e.g. human immunodeficiency virus). Recent studies have identified an increasingly rich network of functionally relevant polymorphic immune factors, including major MHC alleles, killer immunoglobulin-like receptors and functional chemokine receptor polymorphisms. Moreover, genetic variation is increasingly appreciated beyond the single genotype level, incorporating extended haplotypes as well as regions of segmental genetic duplication. These issues can be considered within an evolutionary perspective that acknowledges the crucial role of adaptive host-viral relationships in shaping both host and pathogen genetic diversity.

Cohort- and time-specific associations of CTLA4 genotypes with HIV-1 disease progression

BACKGROUND

CTLA4 in the chromosome 2q33 region encodes cytotoxic T-lymphocyte (CTL) associated antigen 4, which downregulates CTL responses. We examined the relationships between common CTLA4 variants and several outcomes of HIV-1 infection in adults and adolescents.

METHODS

We studied 765 HIV-1-infected persons: 558 Caucasian seroconverters from three cohorts (MACS, ACS, and DCG) and 207 infected adolescents (mostly female) from another cohort (REACH) of mixed ethnicity. Single nucleotide polymorphisms in CTLA4 promoter (-1147C/T, -658C/T, -318C/T), coding sequence (49A/G) and the 3' untranslated region (CT60A/G) were resolved by PCR-based techniques. Repeated measures and survival analyses were used to test allelic and haplotypic associations with HIV-1 viral load (VL) and time to AIDS, respectively.

RESULTS

Individuals carrying -318T or the (-1147) T-(-318) T haplotype had elevated HIV-1 VL in MACS and REACH but reduced VL in DCG and ACS participants. Time-dependent associations of CTLA4-318T with VL were observed in MACS and REACH (P = 0.03-0.09). In Cox regression models adjusted for age and established contributory markers in CCR5 and HLA class I genes, CTLA4-318T was associated with rapid progression to AIDS in MACS (relative hazard 1.69; 95% confidence interval, 1.15-2.49; P < 0.01) as opposed to a non-significant slower disease progression in ACS and no appreciable association in DCG.

CONCLUSIONS

Association of CTLA4 genotypes with clinical and virological outcomes following HIV-1 infection appeared to vary with time and among the cohorts. Further analyses in conjunction with other biologically and positionally related genes, such as CD28 and ICOS, may help explain the disparate findings.

Polymorphisms in the CC-chemokine receptor-2 (CCR2) and -5 (CCR5) genes and risk of coronary heart disease among US women

OBJECTIVE

Genetic variation in CC-chemokine receptor-2 (CCR2) and -5 (CCR5), and their common haplotypes, acting through inflammatory responses, may affect atherosclerosis and risk of coronary heart disease (CHD).

METHOD AND RESULTS

We examined seven common variants in the CCR2 and CCR5 loci and risk of CHD among women in the Nurses' Health Study. During 8 years of follow-up, we documented 248 incident cases of nonfatal myocardial infarction and fatal CHD, and matched controls 2:1 based on age and smoking. The distribution of alleles was similar between cases and controls. The haplotype-specific odds ratios (ORs) were not statistically significant nor was the globally-adjusted p-value (p=0.61). However, there was a statistically significant association for CCR5-Delta32 and A58755G (rs2856758) between cases and controls comparing age of onset <55 and >or=55 years. For Delta32, the OR for having the variant was 0.12 (0.02-0.76) for age <55, and 1.14 (0.69-1.88) for age >or=55 years (p, interaction=0.04). The CCR5-Delta32 was in linkage disequilibrium with 58755G, and a similar association was observed for having the 58755G.

CONCLUSIONS

In this population, CCR2-CCR5 haplotypes were not associated with risk of CHD. However, our data suggest a strong inverse association for certain CCR5 variants and early age of CHD onset.

CCR5, RANTES and CX3CR1 polymorphisms: possible genetic links with acute heart rejection

BACKGROUND

The inflammation response is modulated by the elaborated chemokine-chemokine receptor system, which also plays an important role in the development of acute rejection (AR). In this study, we hypothesized that functional genetic variants of some of these modulatory proteins might influence the outcome of AR.

METHODS

In a retrospective analysis of a cohort of heart transplanted patients (n=158), we examined eight polymorphisms in four genes implicated in this inflammatory process: RANTES, CCR5, CCR2 and CX3CR1. On the basis of timing occurrence, AR episodes (grade>or= 3A) were classified in "early" (0-3 months posttransplantation; EAR) or "late" outcomes (4-12 months posttransplantation; LAR).

RESULTS

The incidences of EAR and LAR were 57.6% and 41%, respectively. Number of LAR episodes was significantly higher in subjects that have already experienced one or more EAR episodes, as compared to subjects that had no EAR (median [25%-75%]: 4 () vs. 1 [1-2.5] respectively; P<0.0001). Statistical univariate analysis showed that none of the mentioned polymorphisms were correlated with EAR or LAR. However, allele-allele association analysis showed that subjects carrying both the CX3CR1 249I allele and CCR5 No-E haplotypes were significantly at lower risk of experiencing EAR (OR=0.2 [95%-CI=0.1-0.5], P=0.001). In contrast subjects carrying both the CCR5 E haplotype and the RANTES -403A allele were significantly at higher risk to develop LAR (OR=8.1 [95%-CI=2.3-28.7], P=0.002).

CONCLUSIONS

This exploratory study in heart transplantation suggests that the outcomes of EAR and LAR episodes may be influenced by genetic variant interactions such as "CX3CR1 249I*CCR5 No-E" and "CCR5 E*RANTES -403A."

Low-level CD4+ T cell activation is associated with low susceptibility to HIV-1 infection

Different features have been associated with low susceptibility to HIV type 1 (HIV-1) infection in exposed seronegative individuals. These include genetic make-up such as homozygosity for the CCR5-Delta32 allele and the presence of HIV-specific CTLs. We studied immune activation and immune responsiveness in relation to HIV-1 susceptibility in 42 high-risk seronegative (HRSN) participants of the Amsterdam Cohort Studies and 54 men from the same cohort who were seronegative at the moment of analysis but later became HIV seropositive. HRSN had higher naive (CD45RO CD27) CD4 and CD8 T cell numbers and lower percentages of activated (HLADR CD38, CD70) CD4 and proliferating (Ki67) CD4 and CD8 T cells, irrespective of previous episodes of sexually transmittable infections. Furthermore, whole blood cultures from HRSN showed lower lymphoproliferative responses than healthy laboratory controls. These data suggest that low levels of immune activation and low T cell responsiveness may contribute to low HIV susceptibility.

Distribution of CCR2-64I and SDF1-3'A alleles and HIV status in 7 ethnic populations of Cameroon

Limited information is available on the prevalence among rural Africans of host genetic polymorphisms conferring resistance to HIV-1 infection or slowing HIV disease progression. We report the allelic frequencies of the AIDS-related polymorphisms CCR2-64I, SDF1-3'A, and CCR5-Delta32 in 321 volunteers from 7 ethnic groups in Cameroon. Allelic frequencies differed among the 7 ethnic groups, ranging from 10.8% to 31.3% for CCR2-64I and 0.0% to 7.1% for SDF1-3'A. No CCR5-Delta32 alleles were found. HIV seroprevalence was 6.9% in the total population and peaked at younger ages in girls and women than in boys and men. Among 15- to 54-year-olds, HIV seroprevalence varied from 2.0% to 11.1% among the village populations. Conditional logistic regression analysis using data from boys and men aged 15 to 54 years showed the number of CCR2-64I alleles to be a significant risk factor for HIV seropositivity (odds ratio per allele adjusted for age and matched on ethnic group = 6.3, 95% confidence interval: 1.3-30.3); this association was not found in women. The findings are consistent with the hypothesis that CCR2-64I alleles may delay HIV disease progression without affecting susceptibility to infection among men. We did not observe this relation among women, and other factors, such as multiple pregnancies or maternal stressors (eg, breastfeeding), may have masked any protective effect of CCR2-64I alleles. Further study of this issue among women is warranted. SDF1-3'A did not differ between HIV-seropositive and HIV-seronegative individuals but was associated with increasing age among HIV-seronegative women, suggesting a protective effect against HIV-1 infection.

Combined effect of CCR5-Delta32 heterozygosity and the CCR5 promoter polymorphism -2459 A/G on CCR5 expression and resistance to human immunodeficiency virus type 1 transmission

Exposed seronegative individuals (ES) with persistent high-risk sexual behavior may be less susceptible to human immunodeficiency virus type 1 (HIV-1) infection because they carry the chemokine receptor (CR) gene alleles CCR5 open reading frame (ORF) Delta32, CCR5 promoter -2459G, or CCR2 ORF 64I (CCR2-64I), all of which have been found to diminish HIV-1 infectivity and/or disease progression. To investigate this, we determined the haplotypes for these three genetic loci in 93 ES and 247 low-risk control individuals. To test if protective haplotypes exert their effect by modulating CR expression, we measured the protein expression of CCR5 and CXCR4 on circulating CD4+ T cells and CD14+ monocytes in 71 ES and 92 controls. To avoid investigator bias, the analysis was performed without knowledge of each subject's risk and genotype. The CCR5 -2459G allele was significantly enriched in ES Caucasian men, who constituted the majority (84%) of the ES cohort, compared to the control Caucasian men (P = 0.02). This increase was mostly attributable to a higher frequency of the -2459 A/G versus the -2459 A/A genotype in individuals heterozygous for the delta32 allele (P = 0.012). No protective influence of the CCR2-64I allele was observed. The haplotypes CCR5 ORF delta32/CCR5 -2459A (in complete linkage disequilibrium) and CCR5 ORF wt/CCR5 -2459G had a cumulative negative effect on the expression of CCR5, since we measured significantly reduced CCR5 densities on both T-helper cells and monocytes only when both haplotypes were present. Densities of CCR5 on lymphocytes and monocytes were correlated (r = 0.59; P < 0.0001), indicating concordance of CCR5 expression patterns across different cell types. We conclude that the CCR5 ORF delta32/wt-CCR5 -2459 A/G genotype combination offers an advantage in resisting sexual HIV-1 transmission and that this effect is mediated by a relative paucity of CCR5 on potential target cells of HIV-1.

Cytokine and chemokine gene polymorphisms among ethnically diverse North Americans with HIV-1 infection

Twenty-four common single nucleotide polymorphisms (SNPs) in 10 cytokine and chemokine genes were defined in 579 North Americans at high risk of HIV-1 infection due to sexual behavior and injection drug use. Among the 3 major ethnic (African-American, Hispanic/Latino, and other) groups involved, HIV-1-seropositive individuals differed significantly from ethnically matched HIV-1-seronegative individuals (odds ratios = 2.13-4.82; P = 0.003-0.05) for several SNPs and haplotypes defined at the IL4, IL4R, IL6, IL10, CCL5 (RANTES), and CXCL12 (SDF1) loci. In addition, the homozygous IL4-590T/T genotype was associated with higher (+87-131 cells/microL) CD4 T-cell counts in HIV-1-infected and AIDS-free adolescents not receiving antiretroviral therapy (adjusted P = 0.004). No SNPs at IFNG, IL2, IL12B, TNF, or CCL2 (MCP1) showed any association with HIV-related outcomes. Additional typing for IL1A, IL1B, IL1R1, IL1RN, and TGFB1 SNPs also failed to demonstrate any influence on HIV-1 infection or virologic/immunologic control in more selected patient groups. Coupled with previous findings, our data suggest that heritable IL4 and IL10 variations may contribute to the acquisition or progression of HIV infection and that the effects of other targeted loci in the cytokine and chemokine system cannot be established unequivocally in the study populations.

HIV/AIDS: a minority health issue

HIV infection among racial and ethnic minorities is an ongoing health crisis. The disproportionate impact of HIV infection on racial and ethnic minorities has affected communities already struggling with many social and economic challenges, such as poverty, substance abuse, homelessness,unequal access to health care, and unequal treatment once in the health care system. Superimposed on these challenges is HIV infection, the transmission of which is facilitated by many of these factors. Although the epidemic is disproportionately affecting all racial and ethnic minorities, within these minority populations women are particularly affected. The care and management of racial and ethnic minorities who have HIV infection has been complicated by the unequal access to health care and the unequal treatment once enrolled in health care. Health insurance status, lack of concordance between the race of the patient and the provider, and satisfaction with the quality of their care all impact on treatment outcomes in this population. In addition, the provider must be aware of the many comorbid conditions that may affect the delivery of care to minority patients living with HIV infection: depression, substance and alcohol abuse, and posttraumatic stress disorders. The impact of these comorbid conditions on the therapeutic relationship, including treatment and adherence, warrants screening for these disorders and treating them when identified. Because the patient provider relationship has been repeatedly identified as a predictor of higher adherence, developing and maintaining a strong therapeutic alliance is critical. Participation of racial and ethnic minorities in HIV clinical trials, as in other disease states, has been very poor. Racial and ethnic minorities have been chronically underrepresented in HIV clinical trials, despite their overrepresentation in the HIV epidemiology. This underrepresentation seems to be the result of a combination of factors including (1) provider bias in referring to clinical trials, (2) mistrust of clinical research, (3) past poor experience with the health care system, and (4) the conspiracy theories of HIV disease. The paucity of minority health care professionals and minority investigators in HIV research further affects minority participation in clinical research. To improve racial and ethnic minority participation in clinical trials a sustained effort is necessary at multiple levels. Increased recruitment and retention is an ongoing need, and one that will not be satisfactorily addressed until there are better community-academic and research partner-ships, and the research questions posed also address issues of concern and significance to the affected community. Reduction in barriers to participation in clinical trials, especially given the many competing needs of racial and ethnic minority patients, is also needed. Multidisciplinary HIV care teams and research staff with training in cultural competency and cultural sensitivity may also be helpful. Prevention of HIV infection remains essential, especially among those seeking care for HIV infection. Despite several published recommendations for the inclusion of HIV prevention in the clinical care setting, studies have documented how few providers actually achieve this goal, especially those who care for disadvantaged patients. Although there are many barriers to discussing HIV risk behaviors and prevention strategies in an office visit,including time constraints and potential provider discomfort in discussing these matters, clinical visits represent an important opportunity to reinforce HIV prevention and possibly decrease further HIV transmission.

The effect of RANTES chemokine genetic variants on early HIV-1 plasma RNA among African American injection drug users

HIV-1 plasma RNA is a prognostic indicator of HIV-1, and increased levels of HIV-1 plasma RNA are associated with rapid progression to AIDS. Because chemokines and chemokine receptors are involved in the binding and entry of HIV-1, possible effects of host genetics on viral RNA levels should be visible in early infection. HIV-1 plasma RNA was measured within 2 years of seroconversion in 198 seroincident injection drug users followed in the AIDS Link to Intravenous Experience cohort. Genetic variants were identified in the chemokine receptors (CCR2, CCR5, and CCR5 promoter) and the chemokine RANTES using TaqMan and restriction fragment length polymorphism assays. Linear regression of RANTES haplotypes on early HIV-1 plasma RNA identified individuals homozygous for the RANTES R1 haplotype as having a lower viral load by almost one-half log10 unit compared with those bearing non-RANTES R1 haplotypes (-0.43, 95% confidence interval: -0.74, -0.12). Genetic variants in RANTES may downregulate RANTES gene expression and increase early HIV-1 plasma RNA. Because RANTES is a critical chemokine and competitively inhibits HIV-1 by binding to its receptor CCR5, treatment to enhance RANTES expression may assist in delaying the progression of AIDS by decreasing the initial viral load.

Influence of host genetic variation on susceptibility to HIV type 1 infection

For this review of genetic susceptibility to human immunodeficiency virus type 1 infection, far more information was available on factors involved in acquisition of the virus by an uninfected "recipient" than on propagation by the infected "donor." Genetic variation presumably alters transmission from an infected host primarily by regulating the replication of virus and the concentration of particles circulating in blood and mucosal secretions of the potential donor. Thus, the effects of host genetic variation on transmission are inextricably bound to the well-established and powerful effects on virus load at different stages of infection. Teasing apart the effects in both donors and recipients has been and will continue to be quite difficult.

Association of CCR5 human haplogroup E with rapid HIV type 1 disease progression

The combination of unique single nucleotide polymorphisms in the CCR5 regulatory and in the CCR2 and CCR5 coding regions, defined nine CCR5 human haplogroups (HH): HHA-HHE, HHF*1, HHF*2, HHG*1, and HHG*2. Here we examined the distribution of CCR5 HH and their association with HIV infection and disease progression in 36 HIV-seronegative and 76 HIV-seropositive whites from North America and Spain [28 rapid progressors (RP) and 48 slow progressors (SP)]. Although analyses revealed that HHE frequencies were similar between HIV-seronegative and HIV-seropositive groups (25.0% vs. 32.2%, p > 0.05), HHE frequency in RP was significantly higher than that in SP (48.2% vs. 22.9%, p = 0.002). Survival analysis also showed that HHE heterozygous and homozygous were associated with an accelerated CD4 cell count decline to less than 200 cells/microL (adjusted RH 2.44, p = 0.045; adjusted RH = 3.12, p = 0.037, respectively). These data provide further evidence that CCR5 human haplogroups influence HIV-1 disease progression in HIV-infected persons.

Bioluminescence resonance energy transfer reveals ligand-induced conformational changes in CXCR4 homo- and heterodimers

Homo- and heterodimerization have emerged as prominent features of G-protein-coupled receptors with possible impact on the regulation of their activity. Using a sensitive bioluminescence resonance energy transfer system, we investigated the formation of CXCR4 and CCR2 chemokine receptor dimers. We found that both receptors exist as constitutive homo- and heterodimers and that ligands induce conformational changes within the pre-formed dimers without promoting receptor dimer formation or disassembly. Ligands with different intrinsic efficacies yielded distinct bioluminescence resonance energy transfer modulations, indicating the stabilization of distinct receptor conformations. We also found that peptides derived from the transmembrane domains of CXCR4 inhibited activation of this receptor by blocking the ligand-induced conformational transitions of the dimer. Taken together, our data support a model in which chemokine receptor homo- and heterodimers form spontaneously and respond to ligand binding as units that undergo conformational changes involving both protomers even when only one of the two ligand binding sites is occupied.

Insights into the role of host genetic and T-cell factors in resistance to HIV transmission from studies of highly HIV-exposed Thais

Studies of resistance to HIV-1 transmission are likely to be valuable for the design of vaccines and other efforts to prevent HIV. Here, we review the T-cell and genetic factors associated with resistance to HIV-1 transmission in studies of highly exposed but persistently seronegative (HEPS) women from northern Thailand. Women were enrolled in two sex-worker studies and in a discordant couple study. We performed Cr51 cytotoxic T lymphocyte (CTL), interferon-gamma (IFN-gamma) ELISPOT, and proliferation assays as well as genetic studies, including HLA-class I typing. CTL and ELISPOT studies showed a skewing of T-cell responses to conserved HIV-1 proteins in HEPS, but not in HIV-1-seropositive women. T-cell responses were extremely long-lived in some HEPS women. In the two sex-worker studies, HLA-A11 was associated with resistance to HIV-1 transmission. These data provide promise for the ability of CTL to control HIV and emphasize the importance of developing HIV vaccines that stimulate strong, long-lasting Tcell responses.

Dominant Effects of CCR2-CCR5 Haplotypes in HIV-1 Disease Progression

Three haplotypes for the CCR2-CCR5 region previously have been shown to affect AIDS progression; however, it is not known if the protective and accelerating effects of the haplotypes are relatively constant throughout infection or exert their effects early or late in HIV type 1 infection. The authors report the relative contributions to AIDS progression of CCR2 64I, CCR5 Delta32, and the CCR5 promoter haplotype +.P1.+ in the GRIV cohort, which included patients representing the extremes of the distribution for AIDS progression: rapid progressors (RP) who developed CD4 T-cell counts of <300/ mm within 3 years after the last HIV-1-seronegative test and slow progressors (SP) who were HIV-1 infected for > or =8 years with CD4 T-cell counts of >500/mm. Comparing the RP with a seroconverter control group including intermediate progressors to AIDS, we observed the early protective effect of CCR5 Delta32 (odds ratio = 0.25; P = 0.007) was similar in strength to the early susceptible effect of CCR5 +.P1.+ (odds ratio = 2.1, P = 0.01). Comparison of the intermediate control group to the SP showed weaker and less significant odd ratios, suggesting that the effect of these factors tended to be stronger on early progression; the tendency towards a disproportionately early effect was significant for CCR5 Delta32 (P = 0.04) but not for CCR5 +.P1.+ (P = 0.12). Follow-up of SP demonstrated that these polymorphisms have little effect after 8 years, because the subset of SP who had progression after study entry had the same genotype distribution as the global population of SP, suggesting that factors other than CCR5 or CCR2 genetic variants must be responsible for the long-term maintenance of nonprogression.