CCR5Delta32 and promoter polymorphisms are not correlated with initial virological or immunological treatment response

Individualization of antiretroviral therapy--pharmacogenomic aspect

Combination therapy with three drug regimens for human immunodeficiency virus (HIV) infection significantly suppresses the viral replication. However, this therapeutic impact is restricted by adverse drug events and response in terms of short and long term efficacy. There are multiple factors involved in different responses to antiretrovirals (ARVs) such as age, body weight, disease status, diet and heredity. Pharmacogenomics deals with individual genetic make-up and its role in drug efficacy and toxicity. In depth genetic research has provided evidence to predict the risk of developing certain toxicities for which personalized screening and surveillance protocols may be developed to prevent side effects. Here we describe the use of pharmacogenomics for optimal use of HAART (highly active antiretroviral therapy).

Factors associated with long-term CD4 cell recovery in HIV-infected patients on successful antiretroviral therapy

OBJECTIVES

The aim of the study was to study the factors associated with immunological recovery in HIV-infected patients with suppressed viral load.

METHODS

Nadir and current CD4 cell counts were recorded in 821 patients, as well as many demographic, epidemiological, lifestyle, clinical, therapeutic, genetic, laboratory, liver fibrosis and viral hepatitis parameters.

RESULTS

The median age of the patients was 44.4 years [interquartile range (IQR) 40.3-48.0 years], the median time since HIV diagnosis was 15.3 years (IQR 10.5-18.9 years), the median time of suppressed viral load was 7.0 years (IQR 4.0-10.0 years) and the median time on the current antiretroviral regimen was 2.8 years (IQR 1.4-4.7 years). The median nadir and current CD4 counts were 193.0 (IQR 84.0-301.0) and 522.0 (IQR 361.0-760) cells/μL, respectively, separated by a median period of 10.2 years (IQR 5.9-12.9 years). The median CD4 count gain during follow-up was 317.0 (IQR 173.0-508.0) cells/μL. Many variables were associated with CD4 cell gains in univariate analyses, including age, gender, epidemiology, prior clinical conditions, fibrosis stage, transient elastometry, aspartate aminotransferase (AST), nadir CD4 count and hepatitis B and C virus infections and genotypes, as well as the durations of follow-up since nadir CD4 count, overall antiretroviral treatment, current antiretroviral regimen, protease inhibitor therapy and suppression of viral load. Multivariate analysis revealed that longer duration of HIV suppression (P < 0.0001), more advanced clinical Centers for Disease Control and Prevention (CDC) stages (P < 0.0001), younger age (P = 0.0003), hepatitis C virus genotypes 1 and 4 (P = 0.003), sexual acquisition of HIV (P = 0.004), and lower transient elastometry values (P = 0.03) were independent predictors of CD4 cell gains. Overall, the model accounted for 14.2% of the variability in CD4 count.

CONCLUSIONS

In addition to the duration of HIV suppression, HIV-related diseases, HIV epidemiology, age, hepatitis C virus genotypes, and liver fibrosis were independently associated with long-term immunological recovery.

Differential evolution of a CXCR4-using HIV-1 strain in CCR5wt/wt and CCR5∆32/∆32 hosts revealed by longitudinal deep sequencing and phylogenetic reconstruction

Rare individuals homozygous for a naturally-occurring 32 base pair deletion in the CCR5 gene (CCR5∆32/∆32) are resistant to infection by CCR5-using ("R5") HIV-1 strains but remain susceptible to less common CXCR4-using ("X4") strains. The evolutionary dynamics of X4 infections however, remain incompletely understood. We identified two individuals, one CCR5wt/wt and one CCR5∆32/∆32, within the Vancouver Injection Drug Users Study who were infected with a genetically similar X4 HIV-1 strain. While early-stage plasma viral loads were comparable in the two individuals (~4.5-5 log10 HIV-1 RNA copies/ml), CD4 counts in the CCR5wt/wt individual reached a nadir of <20 CD4 cells/mm(3) within 17 months but remained >250 cells/mm(3) in the CCR5∆32/∆32 individual. Ancestral phylogenetic reconstructions using longitudinal envelope-V3 deep sequences suggested that both individuals were infected by a single transmitted/founder (T/F) X4 virus that differed at only one V3 site (codon 24). While substantial within-host HIV-1 V3 diversification was observed in plasma and PBMC in both individuals, the CCR5wt/wt individual's HIV-1 population gradually reverted from 100% X4 to ~60% R5 over ~4 years whereas the CCR5∆32/∆32 individual's remained consistently X4. Our observations illuminate early dynamics of X4 HIV-1 infections and underscore the influence of CCR5 genotype on HIV-1 V3 evolution.

Early initiation of combination antiretroviral therapy in HIV-1-infected newborns can achieve sustained virologic suppression with low frequency of CD4+ T cells carrying HIV in peripheral blood

BACKGROUND

A human immunodeficiency virus type 1 (HIV-1)-infected infant started on combination antiretroviral therapy (cART) at 30 hours of life was recently reported to have no detectable plasma viremia after discontinuing cART. The current study investigated the impact of early cART initiation on measures of HIV-1 reservoir size in HIV-1-infected children with sustained virologic suppression.

METHODS

Children born to HIV-1-infected mothers and started on cART within 72 hours of birth at 3 Canadian centers were assessed. HIV serology, HIV-1-specific cell-mediated immune responses, plasma viremia, cell-associated HIV-1 DNA and RNA, presence of replication-competent HIV-1, and HLA genotype were determined for HIV-1-infected children with sustained virologic suppression.

RESULTS

Of 136 cART-treated children, 12 were vertically infected (8.8%). In the 4 who achieved sustained virologic suppression, HIV serology, HIV-1-specific cell-mediated immune responses (Gag, Nef), and ultrasensitive viral load were negative. HIV-1 DNA was not detected in enriched CD4(+) T cells of the 4 children (<2.6 copies/10(6) CD4(+) T cells), whereas HIV-1 RNA was detected (19.5-130 copies/1.5 µg RNA). No virion-associated HIV-1 RNA was detected following mitogenic stimulation of peripheral blood CD4(+) T cells (5.4-8.0 million CD4(+) T cells) in these 4 children, but replication competent virus was detected by quantitative co-culture involving a higher number of cells in 1 of 2 children tested (0.1 infectious units/10(6) CD4(+) T cells).

CONCLUSIONS

In perinatally HIV-1-infected newborns, initiation of cART within 72 hours of birth may significantly reduce the size of the HIV-1 reservoirs. Cessation of cART may be necessary to determine whether functional HIV cure can be achieved in such children.

Evaluation of the pharmacogenetics of immune recovery in treated HIV-infected patients

INTRODUCTION

Combination antiretroviral therapy has markedly improved the survival rate and quality of life in patients infected with HIV due to the powerful suppressor effect that current antiretroviral drugs have on the viral load. Consequently, the immune system undergoes a substantial qualitative and quantitative improvement; and this leads to an increase in the absolute CD4(+) T-lymphocyte count and the restoration of lost T-cell responses against certain opportunistic pathogens. Unfortunately, not all patients who successfully suppress plasma viremia experience sufficient CD4(+) T-cell gain and these patients, in turn, are associated with worse outcomes. Pharmacogenetic studies have been used to investigate how a patient's genetic predisposition may affect their response to antiretroviral drugs.

AREAS COVERED

This article reviews the investigations that have been published on the association between host genetic determinants of CD4(+) T-cell gain in treated HIV-infected patients. Studies were identified through a PubMed database search. Longitudinal studies into pharmacogenetic association were specifically selected.

EXPERT OPINION

While the possibility of genetic predisposition to HIV therapeutics has potential, most studies provide inconsistent data. Inconsistency is often due to partial genetic evaluation, different categorization of poor immune recovery or due to small numbers of patients evaluated. Currently, studies still belong to the research laboratory stage and more studies are required to improve our understanding.

The effect of combined polymorphisms in chemokines and chemokine receptors on the clinical course of HIV-1 infection in a Brazilian population

Polymorphisms in genes that encode chemokines or their receptors can modulate susceptibility to human immunodeficiency virus (HIV) infection and disease progression. The objective of this study was to assess the frequency of polymorphisms CCR5-Δ32, CCR2-64I, CCR5-59029A and SDF1-3'A and their role in the course of HIV infection in a Southern Brazilian population. Clinical data were obtained from 249 patients for an average period of 6.4 years and genotypes were determined by standard polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism. Survival analyses were conducted for three outcomes: CD4+ T-cell counts below 200 cells/µL, acquired immune deficiency syndrome (AIDS) or death. The frequency of the polymorphisms CCR5-Δ32, CCR2-64I, CCR5-59029A and SDF1-3'A were 0.024, 0.113, 0.487 and 0.207, respectively. CCR5-Δ32 was associated with a reduction in the risk for CD4+ T-cell depletion and with an increased risk for death after AIDS diagnosis. CCR2-64I was associated with a reduction in the risk for developing AIDS. SDF1-3'A was also associated with decreased risk for AIDS, but its effect was only evident when CCR2-64I was present as well. These results highlight the possibility of using these markers as indicators for the prognosis of disease progression and provide evidence for the importance of analysing the effects of gene polymorphisms in a combined fashion.

Risk of all-cause mortality in HIV infected patients is associated with clinical, immunologic predictors and the CCR5 Δ32 deletion

Objective

Investigation of the interplay between the CCR5 Δ32/wt genotype and demographic, epidemiological, clinical and immunological factors associated with mortality in the cART era.

Design

Longitudinal data from 507 HIV-infected patients following the Δ32 allele detection were analyzed.

Methods

Cumulative 15 years mortality was calculated using Kaplan-Meyer methodology. Hazard ratios were estimated using univariate Cox models. Basing on Akakie information criteria and statistical significance multivariate Cox model was constructed and effect plots presenting adjusted hazard ratio time-dependency were drawn. Analysis of the association of all-cause mortality and CCR5 Δ32/wt genotype prior to the antiretroviral treatment (cART) initiation (n = 507) and on the therapy (n = 422) was also performed.

Results

A mortality rate of 2.66 (CI 2.57–3.19) per 100 person-years was observed. Univariate analysis factors modifying the risk of death included the CCR5 genotype, gender, history of cART, AIDS diagnosis and also CD4 lymphocyte nadir, zenith, the latest CD4 count and stable levels >500 cells/µl. For multivariate analysis the following predictors were selected: CCR5 genotype (HR for wt/wt 2.53, CI 1.16–5.53, p = 0.02), gender (HR for males 1.91, 95%CI 1.1–3.36, p = 0.023), introduction of combined antiretroviral treatment (HR 4.85, CI 3.0–7.89, if untreated or treated <1 month, p<0.0001) CD4 count of 500 cells/µl for six months or more (HR 4.16, CI 1.95–8.88 if not achieved, p = 0.028), the latest CD4 count (HR 5.44, CI 3.39–8.74 for <100 cells/µl, p<0.0001) and history of AIDS (HR 1.69, CI 1.03–2.79, p = 0.039). Among untreated individuals the Δ32/wt genotype was associated with notably better survival (p = 0.026), while among cART treated individuals the Δ32 mutation did not correlate significantly with higher survival rates (p = 0.23).

Conclusions

The Δ32 CCR5 allele is associated with a reduction of the risk of all-cause mortality in HIV (+) patients alongside clinical and immunologic predictors such as AIDS, history of cART, lymphocyte CD4 cell count and gender.

Chemokine (C-C motif) receptor 5 -2459 genotype in patients receiving highly active antiretroviral therapy: race-specific influence on virologic success

BACKGROUND

In patients receiving highly active antiretroviral therapy (HAART), antiretroviral drug-metabolizing enzyme and transporter gene polymorphisms, as well as chemokine receptor gene polymorphisms, may influence response to treatment.

METHODS

In a North American, treated, adherent human immunodeficiency virus (HIV)-positive cohort (self-identified whites, n = 175; blacks, n = 218), we investigated whether CYP2B6 (516G>T, 983T>C), UGT2B7 (IVS1+985A>G, 802C>T), MDR1 3435C>T, chemokine (C-C motif) receptor 2 (CCR2) 190G>A, and CCR5 (-2459G>A, Δ32) polymorphisms influenced the time to achieve virologic success (TVLS).

RESULTS

No difference in TVLS was observed between races. In Kaplan-Meier analyses, only 516G>T (log-rank P = .045 for comparison of GG, GT, and TT and P = .02 GG + GT vs TT) and -2459G>A (log-rank P = .04 for GG, GA, and AA and P = .02 for GG + GA vs AA) genotypes were significantly associated with TVLS in black patients but not in white patients. However, in the Cox proportional hazards model that included age, sex, baseline CD4(+) T cell count, and baseline viral load, no significant association was observed between 516G>T and TVLS, whereas the association between -2459G>A and TVLS remained significant even after including CCR2 190G>A as well as all the drug-metabolizing enzyme and transporter genotypes.

CONCLUSIONS

These findings suggest that CCR5 -2459G>A genotype had a strong, race-specific influence on TVLS in this cohort. Understanding the possible mechanisms underlying this influence requires further studies.

Is long-term virological response related to CCR5 Delta32 deletion in HIV-1-infected patients started on highly active antiretroviral therapy?

OBJECTIVE

The aim of the study was to determine whether the chemokine (C-C motif) receptor 5 (CCR5) Delta32 deletion is associated with long-term response to combination antiretroviral treatment (cART) in HIV-1-infected patients.

METHODS

The genetic substudy of the Agence Nationale de Recherche sur le SIDA (ANRS) CO8 APROCO-COPILOTE cohort included 609 patients who started protease inhibitor-containing cART in 1997-1999. Patients were considered to have a sustained virological response if all plasma HIV RNA measurements in the period considered were <500 HIV-1 RNA copies/ml, allowing for a single blip. Virological response was compared between patients heterozygous for CCR5 Delta32 (Delta32/wt) and wild-type patients (wt/wt) from month 4 to year 3 and from month 4 to year 5. Logistic regression analysis was used to adjust for baseline demographical data, HIV RNA, CD4 cell count, antiretroviral exposure status, time spent on antiretroviral therapy at years 3 and 5 and adherence to treatment (month 4 to year 3 or 5).

RESULTS

A sustained virological response was more frequent in Delta32/wt than in wt/wt patients from month 4 to year 3, with 66%vs. 52% of patients, respectively, showing a sustained response (P=0.02); after adjustment for potential confounders, the association of Delta32 with a sustained response was nearly significant (P=0.07). A sustained virological response was also more frequent in Delta32/wt patients up to year 5, with 48% showing a sustained response vs. 35% of wt/wt patients (P=0.01); after adjustment, Delta32 remained significantly associated with a sustained virological response up to year 5 (P=0.04). There was no association with CD4 response.

CONCLUSION

The Delta32 deletion in Delta32/wt patients is associated with a beneficial virological response to cART in the long term. Whether this association is a direct effect of the Delta32 deletion remains unclear and requires confirmation in further observational studies.

The effects of RANTES/CCR5 promoter polymorphisms on HIV disease progression in HIV-infected Koreans

Recent studies have reported that two single nucleotide polymorphisms (SNPs) in the RANTES gene promoter region, -403G/A and -28C/G, are associated with a slower rate of decline in CD4(+) T-cell number, whereas genetic polymorphisms within the CCR5 promoter are linked to acceleration of AIDS progression. In this study, we investigated the distribution of SNPs in the RANTES and CCR5 promoters and the association between these SNPs and HIV-1 disease progression in HIV-infected Koreans. Twenty-seven long-term non-progressors (LTNPs), 29 AIDS patients and 39 HIV-uninfected persons were enrolled in this study. SNPs for the RANTES and CCR5 promoters were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and a direct sequencing method. In the analysis of RANTES promoter polymorphisms, the genotypic and allelic frequencies of the RANTES -28G mutation were significantly lower in HIV-infected patients than in HIV-uninfected persons (P = 0.005 and P = 0.001, respectively). The genotypic frequencies of RANTES -28G and -403A mutations did not differ significantly between LTNPs and AIDS patients. The frequencies of three CCR5 promoter polymorphisms, designated 59029 G/A, 59353T/C, and 59402G/A, did not differ significantly between HIV-uninfected and HIV-infected patients. However, the allelic frequency of CCR559353C was significantly higher in AIDS patients than in LTNPs (P = 0.003). These results suggest that RANTES-28G and CCR5 59353C mutations might be associated with HIV infection or pathogenesis in the Korean population.

Improved virological response to highly active antiretroviral therapy in HIV-1-infected patients carrying the CCR5 ?32 deletion

BACKGROUND

Patients heterozygous for the C-C chemokine receptor 5 (CCR5) Delta32 deletion spontaneously progress less rapidly to AIDS and death than do wild-type patients. We investigated whether the CCR5 Delta32 deletion has an impact on immunological, virological and clinical responses to highly active antiretroviral therapy (HAART) in HIV-1-infected patients.

PATIENTS AND METHODS

We included in the study 565 HIV-1-infected patients from the French HIV-1 infected cohort with documented date of seroconversion (SEROCO)/haemophiliacs HIV-1 infected (HEMOCO) cohorts, who started HAART after 1996. We investigated virological responses to HAART at 6 months (defined as a plasma HIV-1 RNA measurement below the threshold of detection or a 2 log HIV-1 RNA decrease) and at 12 months (defined as a plasma HIV-1 RNA measurement below the threshold of detection) and clinical response to HAART by Kaplan-Meier survival curves, with AIDS and death as outcomes.

RESULTS

The Delta32 heterozygous patients (n=83; 15%) had a better virological response to HAART than wild-type patients (73 vs 53% at 6 months, P=0.01; and 60 vs 44% at 12 months, P=0.01). This better virological response was still observed after adjustment for antiretroviral status (whether or not patients were naïve to antiretroviral therapy), year of HAART initiation, number of new antiretroviral drugs and baseline viral load. There was no statistical difference between heterozygous patients and wild-type patients in terms of survival and AIDS-free survival.

CONCLUSIONS

CCR5 Delta32 heterozygous patients were more likely to have a virological response to HAART than wild-type patients at 6 and 12 months. However, this virological response did not produce better immunological and clinical responses. The long-term impact of the Delta32 deletion on survival in HIV-1-infected treated patients should be investigated in a meta-analysis.

Analysis of CCR5, CCR2, CX3CR1, and SDF1 polymorphisms in HIV-positive treated patients: impact on response to HAART and on peripheral T lymphocyte counts

Although polymorphisms of chemokine genes (SDF1, stromal cell-derived factor-1 and RANTES, regulated on activation, normal T cell expressed and secreted) and chemokine-receptor genes (CCR5, CCR2, CX(3)CR1) were shown to be associated with sensitivity to HIV infection and untreated HIV disease progression, their association with the response to highly active antiretroviral therapy (HAART) remains unclear. To explore the possible influence of such polymorphisms on the evolution of AIDS in treated patients, we have studied SDF1-3'A, CCR5Delta32, CCR2-64I, CX(3)CR1-249I, and CX(3)CR1-280M polymorphisms in HIV-infected patients under HAART (n = 169). We studied the evolution of plasma virus load and peripheral T lymphocyte counts in these patients up to 3 years after the initiation of HAART. We observed that some of the genetic polymorphisms studied had an impact on the evolution of these two parameters. After 1 year of HAART, patients with a virological response (undetectable plasma HIV-1 RNA) have a higher frequency of the homozygous SDF1-3'A genotype than other patients (p = 0.005). Similarly, patients with a CD4 increase of over 200/mm(3) from baseline after 1 year of HAART display higher frequencies of homozygous SDF1-3'A (p = 0.035) and homozygous CX(3)CR1-280M genotypes (p = 0.04) than other patients. Moreover, we showed that the CX(3)CR1- 280M allele was associated with higher peripheral CD4+ T cell counts not only in HIV+ patients but also in healthy controls (p = 0.003).

CCR2-64I and CXCL12 3′A alleles confer a favorable prognosis to AIDS patients undergoing HAART therapy

BACKGROUND

The chemokine receptor polymorphisms CCR5Delta32, CXCL12 3'A, CCR2-64I and CCR5-59029 G/A have been demonstrated to affect HIV-1 infection and progression.

OBJECTIVE

We studied the impact of the above polymorphisms on the effectiveness of a 30-month treatment with highly active antiretroviral therapy (HAART) in 149 HIV-1 patients.

STUDY DESIGN

We stratified the patients according to CD4 CDC criteria and applied Kaplan-Meier analysis using the following end-point criteria: (a) the time from HAART initiation to undetectable viral load (VL) counts (VL<50 copies/ml), (b) the duration of undetectable VL status and (c) the time required for CD4+ T-cell counts to pass over the 500 cells/ml threshold.

RESULTS

Our results in the second group (CD4 201-500) revealed that patients with the CCR2-64I allele achieved undetectable VL counts at 3.5+/-0.48 months as compared to 10.26+/-1.42 months in the control group (p=0.018). The VL remained undetectable for 28+/-2 months, in contrast to 20+/-2 months in the control group (p=0.048). Patients carrying CXCL12 3'A restored the CD4 population faster than the control group (9+/-2 and 14+/-2 months, respectively, p=0.023). The CCR5Delta32 and CCR5-59029 G/A alleles did not appear to affect the parameters studied.

CONCLUSIONS

Our results suggest that patients carrying either CCR2-64I or CXCL12 3'A have a more favorable prognosis during HAART treatment.

Association of the CCR5Δ32 Mutation with Clinical Response and >5-year Survival following Initiation of First Triple Antiretroviral Regimen

Objective

The CCR5Δ32 mutation is associated with slower HIV disease progression in untreated infection. However, it remains controversial as to whether CCR5Δ32 is a relevant prognostic marker in the context of highly active antiretroviral therapy (HAART). Here we investigate associations between CCR5Δ32 and HAART outcomes in a large, population-based cohort of >1000 antiretroviral-naive individuals initiating triple therapy over a median >5 year follow-up.

Methods

CCR5Δ32 genotypes were determined using PCR and DNA sequencing in a cohort of 1188 antiretroviral-naive individuals initiating triple therapy in British Columbia. Associations between CCR5Δ32 and baseline (pre-therapy) sociodemographic and clinical parameters were investigated in a cross-sectional analysis. Cox proportional hazards regression was used to investigate the effect of CCR5Δ32 on clinical outcomes following therapy initiation. The endpoints that were evaluated included time to plasma viral load (pVL) suppression <400 copies HIV RNA/ml, subsequent time to pVL rebound ≥400 copies/ml, time to CD4+ cell decline below baseline, and time to non-accidental death over a median >5 year follow-up.

Results

CCR5Δ32 genotypes were available for 1174 of 1188 individuals (98.8%): 171 (14.6%) CCR5wt/Δ32 and 1003 (85.4%) CCR5wt/wt. At baseline, CCR5wt/Δ32 individuals had higher CD4+ cell counts ( P=0.04), lower plasma viral loads ( P=0.06) and were slightly older than CCR5wt/wt individuals ( P=0.04). In multivariate analyses controlling for baseline parameters and adherence estimates, we observed a significant association between CCR5wt/Δ32 and a shorter time to initial pVL suppression <400 copies/ml (multivariate hazard ratio [HR]: 1.20; 95% confidence interval [CI]: 1.01-1.44). No associations were observed between CCR5Δ32 and other clinical outcomes including subsequent time to pVL rebound or time to CD4+ cell decline below baseline. In univariate analyses, we observed a significant association between CCR5wt/Δ32 genotype and improved survival over the median >5 year period following initiation of HAART ( P=0.03). However, this association did not remain significant in multivariate analyses after adjusting for baseline factors including adherence (multivariate HR: 0.64; 95% CI: 0.38-1.07; P=0.09)

Conclusion

Results indicate that, after controlling for adherence, the CCR5Δ32 mutation is likely not a clinically significant predictor of longer-term clinical responses or survival in the context of HAART.

Virologic and immunologic response to highly active antiretroviral therapy

Highly active antiretroviral therapy (HAART) delays clinical progression by suppressing viral replication, measured by a substantial reduction in HIV RNA, allowing the immune system to reconstitute, measured in most studies by an increase in CD4 cells. These virologic and immunologic consequences do not occur uniformly among HAART users. Markers of HIV disease stage at the time of HAART initiation are critical determinants of the progression while receiving HAART. In this report, we review studies describing the heterogeneous virologic and immunologic progression after the initiation of HAART, discuss methodologic concerns in the study of the response of biomarkers, and update findings obtained in the Multicenter AIDS Cohort Study, which show that CD4 cell count, history of antiretroviral therapy, and age at the time of initiation are independent determinants of response.

HIV and the CCR5-Δ32 resistance allele

The combination of molecular biology, epidemiology, virology, evolutionary and population genetics has enabled us to understand the delicate interplay between HIV and the CCR5-Delta32 HIV resistance allele. We here review and collect from the different approaches to show how they can be combined to elucidate the interaction between host and pathogen genetics in this system. We will present an overview of the normal role of CCR5, its involvement in HIV, the molecular biology of the CCR5-Delta32 allele and its probable origins. By focusing on this well-documented and important system we hope to demonstrate the power that such a "holistic" approach might offer in the study of infectious diseases.

Update on the Virologic and Immunologic Response to Highly Active Antiretroviral Therapy

Highly active antiretroviral therapy (HAART) delays clinical progression by suppressing viral replication, measured by a substantial reduction in HIV RNA, allowing the immune system to reconstitute, measured in most studies by an increase in CD4 cells. These virologic and immunologic consequences do not occur uniformly among HAART users. Markers of HIV disease stage at the time of HAART initiation are critical determinants of the progression while receiving HAART. In this report, we review studies describing the heterogeneous virologic and immunologic progression after the initiation of HAART, discuss methodologic concerns in the study of the response of biomarkers, and update findings obtained in the Multicenter AIDS Cohort Study, which show that CD4 cell count, history of antiretroviral therapy, and age at the time of initiation are independent determinants of response.

The pharmacogenetics of antiretroviral therapy: a review of studies to date

Although the ever-expanding armamentarium of antiretroviral drugs has significantly decreased the morbidity and mortality due to human immunodeficiency virus infection, patients and clinicians are increasingly faced with the problems of inadequate or toxic response to therapy that may be genetically mediated. Significant evidence now exists that interindividual differences, such as efficacy of therapy, hypersensitivity reactions, and metabolic complications as a result of antiretroviral therapy, are in part genetically determined. This article reviews the significant studies published to date in the area of the pharmacogenetics of antiretroviral therapy and summarizes current trends, as well as areas where further research is needed.

Influence of polymorphisms within the CX3CR1 and MDR-1 genes on initial antiretroviral therapy response

OBJECTIVE

Single nucleotide polymorphisms (SNP) in the genes encoding the human CX3CR1 chemokine receptor and the P-glycoprotein multidrug transporter have been associated with accelerated disease progression in untreated individuals and implicated in therapeutic response, respectively. This retrospective study assessed the influence of SNP in the CX3CR1 and MDR-1 genes on initial virological and immunological response in 461 HIV-infected, antiretroviral-naive individuals initiating antiretroviral therapy in British Columbia, Canada.

METHODS

CX3CR1 and MDR-1 SNP were determined by PCR amplification of human DNA from plasma, followed by DNA sequencing. Time to virological success [time to HIV plasma viral load (pVL) < or = 500 copies/ml], virological failure (subsequent time to the second of two consecutive pVL > or = 500) and immunological failure (time to the second consecutive CD4 cell count below baseline) were analyzed by Kaplan-Meier methods.

RESULTS

Frequencies of CX3CR1 amino acid haplotypes were 249V 280T (0.75), 249I 280M (0.15), and 249I 280T (0.1). Frequencies of MDR-1 nucleotide polymorphisms were 3435C (0.47) and 3435T (0.53). There was no effect detected for SNP in CX3CR1 or MDR-1 on time to virological success, nor of CX3CR1 and MDR-1 SNP on time to virological and immunological failure, respectively ( P > 0.1). There was a trend to earlier virological failure in the MDR-1 3435C/C genotype group ( P = 0.07), and a statistically significant trend to earlier immunological failure in individuals with the CX3CR1 249I polymorphism ( P = 0.02). These remained significant after correcting for baseline age, sex, pVL, CD4 cell count, type of therapy, and adherence ( P < or = 0.05).

CONCLUSION

Polymorphisms in MDR-1 and CX3CR1 may be associated with accelerated virological and immunological therapy failure, respectively.

The effect of race/ethnicity on the outcome of highly active antiretroviral therapy for human immunodeficiency virus type 1-infected patients

We performed a population-based cohort study to assess the impact of nonwhite origin on the outcome of highly active antiretroviral therapy (HAART) for a Danish cohort of human immunodeficiency virus (HIV)-infected patients. A total of 389 whites and 135 nonwhites started receiving HAART before 1 April 2001. After 1 year of treatment, 78% of nonwhites and 76% of whites achieved a virus load of <500 HIV RNA copies/mL. No major differences were found between the 2 groups with respect to achievement of a virus load of <500 copies/mL (relative risk [RR], 0.94; 95% confidence interval [CI], 0.74-1.18), risk of clinical progression (RR, 0.63; 95% CI, 0.32-1.24), or response measured by total CD4+ cell count. One year after fulfilling Danish recommendations for initiation of HAART, 91% of nonwhites and 93% of whites had started receiving HAART. Race and ethnic origin play no major role in the outcome associated with HAART if access to health care is free.

No association between GB virus-C viremia and virological or immunological failure after starting initial antiretroviral therapy

INTRODUCTION

Co-infection with GBV-C ('Hepatitis G' virus) appears to be associated with slower disease progression in HIV-infected, untreated individuals. We wished to determine whether detection of GBV-C RNA was associated with differential response to HIV therapy in a population-based cohort of 461 individuals initiating antiretroviral therapy between June 1996 and August 1998, in British Columbia, Canada.

METHODS

The presence of GBV-C RNA in plasma was identified by nested RT-PCR, using detection of HIV RNA as a positive control. Time to virological success [achieving HIV plasma viral load (pVL) < or = 500 copies/ml], virological failure (subsequent confirmed pVL > 500 copies/ml) and immunological failure (confirmed CD4 cell count below baseline) were assessed by Kaplan-Meier methods and Cox proportional hazard regression.

RESULTS

Of the 441 individuals for whom results were available, 90 (20.4%) had detectable plasma GBV-C RNA. GBV-C RNA was significantly associated with a lower HIV pVL at baseline (P = 0.004). In univariate and multivariate Cox models, GBV-C RNA positive and negative individuals did not differ with respect to time to virological success [risk ratio (RR), 0.98; 95% confidence interval (CI), 0.75-1.27], time to virological failure (RR, 1.10; 95% CI, 0.74-1.65), or time to immunological failure (RR, 1.09; 95% CI, 0.73-1.63). There was no correlation between detection of GBV-C RNA and mutations in the human chemokine receptors CCR5 and CX CR1, or HIV viral tropism as predicted by the HIV envelope sequence (P > 0.1).

CONCLUSION

GBV-C viremia is relatively common in individuals seeking treatment for HIV infection; however, it does not appear to have any effect on initial antiretroviral therapy response.

Virologic and Immunologic Response to Highly Active Antiretroviral Therapy

Highly active antiretroviral therapy (HAART) delays clinical progression to AIDS by suppressing viral replication, allowing the immune system to reconstitute. These virologic and immunologic consequences do not occur uniformly among HAART users; markers of HIV disease stage at the time of HAART initiation are critical determinants of the progression while under HAART. In this paper, we review studies describing the heterogeneous virologic and immunologic progression following the initiation of HAART, and update findings obtained in the Multicenter AIDS Cohort Study that show that CD4 cell count and history of antiretroviral therapy at the time of initiation are independent determinants of response.