Rapid progression to AIDS in HIV+ individuals with a structural variant of the chemokine receptor CX3CR1.

Human immunodeficiency virus (HIV) enters cells in vitro via CD4 and a coreceptor. Which of 15 known coreceptors are important in vivo is poorly defined but may be inferred from disease-modifying mutations, as for CCR5. Here two single nucleotide polymorphisms are described in Caucasians in CX3CR1, an HIV coreceptor and leukocyte chemotactic/adhesion receptor for the chemokine fractalkine. HIV-infected patients homozygous for CX3CR1-I249 M280, a variant haplotype affecting two amino acids (isoleucine-249 and methionine-280), progressed to AIDS more rapidly than those with other haplotypes. Functional CX3CR1 analysis showed that fractalkine binding is reduced among patients homozygous for this particular haplotype. Thus, CX3CR1-I249 M280 is a recessive genetic risk factor in HIV/AIDS.

Association between polymorphism in the chemokine receptor CX3CR1 and coronary vascular endothelial dysfunction and atherosclerosis.

Fractalkine, a chemokine expressed by inflamed endothelium, induces leukocyte adhesion and migration via the receptor CX3CR1, and the CX3CR1 polymorphism V249I affects receptor expression and function. Here we show that this polymorphism is an independent risk factor for atherosclerotic coronary artery disease (CAD). Genotyping of the CX3CR1-V249I polymorphism was performed in a cohort of 339 white individuals who underwent cardiac catheterization (n=197 with and n=142 without CAD, respectively). In 203 patients, intracoronary acetylcholine 15 microg/min) and sodium nitroprusside (20 microg/min) were administered to test endothelium-dependent and -independent coronary vascular function, respectively. Change in coronary vascular resistance (DeltaCVR) was measured as an index of microvascular dilation. An association was observed between presence of the CX3CR1 I249 allele and reduced prevalence of CAD, independent of established CAD risk factors (odds ratio=0.54 [95% confidence interval, 0.30 to 0.96], P=0.03). Angiographic severity of CAD was also lower in these subjects (P=0.01). Furthermore, endothelium-dependent vasodilation was greater in these individuals compared with individuals homozygous for the CX3CR1-V249 allele (DeltaCVR during acetylcholine = -46+/-3% versus -36+/-3%, respectively, P=0.02), whereas DeltaCVR with sodium nitroprusside was similar in both groups (-55+/-2% versus -53+/-2%, P=0.45). The association between CX3CR1 genotype and endothelial function was independent of established risk factors and presence of CAD by multivariate analysis (P=0.02). Thus, the CX3CR1 I249 allele is associated with decreased risk of CAD and improved endothelium-dependent vasodilation. This suggests that CX3CR1 may be involved in the pathogenesis of CAD.

Effect of chemokine receptor gene polymorphisms on the response to potent antiretroviral therapy.

BACKGROUND: Both the natural history of HIV infection and the response to antiretroviral therapy are heterogeneous. Polymorphisms in chemokine receptor genes modulate the natural history of HIV-1 infection. In comparison with subjects with other genotypes, the prognosis for HIV-1-infected CCR5-delta32 heterozygotes is more favorable and that for CCR5 promoter allele 59029A homozygotes is less favorable. METHODS: HIV-1-infected adults with a CD4+ lymphocyte count > or = 200 cells x 10(6)/l and a plasma HIV RNA level > or = 1000 copies/ml were treated with indinavir, zidovudine and lamivudine for 6 months. HIV RNA levels were measured at 4-week intervals. Genotyping for chemokine receptor gene polymorphisms (CCR5-delta32, CCR5 59029A/G, CCR2-641) was performed. We examined whether the time to first HIV RNA < 200 copies/ml, frequency of viral suppression failure (HIV RNA > or = 200 copies/ml between weeks 16 and 28 of therapy), or reduction from the pre-treatment HIV RNA level differed by genotype. RESULTS: Time to first HIV RNA < 200 copies/ml was not predicted by genotype. Among 272 Caucasian patients, viral suppression failure was more common among patients with the CCR5 +/+ ¿ CCR2+/+ ¿ CCR5-59029 A/A genotype (28%) than among all other subjects combined (relative risk, 2.0; P = 0.06). After 24 weeks of therapy, genotype groups differed in the reduction of the HIV RNA level from baseline (P = 0.02); patients with the CCR5 +/+ ¿ CCR2+/+ ¿ CCR5-59029 A/A genotype had a mean reduction of 2.12 log10 copies/ml compared to 2.64 log10 copies/ml among all other groups combined. CONCLUSION: Polymorphisms in chemokine receptor genes may explain some of the heterogeneity in sustaining viral suppression observed among patients receiving potent antiretroviral therapy.

Chemokine RANTES promoter polymorphism affects risk of both HIV infection and disease progression in the Multicenter AIDS Cohort Study.

OBJECTIVE: To examine whether polymorphism in the RANTES gene is associated with HIV disease outcome. DESIGN: RANTES, a ligand of the major HIV co-receptor, CCR5, is known to block HIV-CCR5 interactions. Recently, two single nucleotide polymorphisms in the RANTES gene promoter region, designated -403G/A and -28C/G, have been described. Both polymorphisms can affect in-vitro promoter activity, and the RANTES -403A, -28G haplotype has been associated with a slower CD4 cell count decline rate in a Japanese cohort. METHODS: We compared RANTES compound genotype frequencies between HIV-positive and exposed-uninfected participants of the Multicenter AIDS Cohort Study (MACS) and rates of progression to AIDS for MACS seroconverters. RESULTS: We found that the two most common RANTES promoter compound genotypes, G1 (-403G/G, -28C/C) found in 67% of Caucasians, and G4 (-403G/A, -28C/C) found in 23% of Caucasians, were associated with altered risk of HIV transmission and progression, particularly in individuals who lacked the protective CCR5 mutation, CCR5delta32. In this study, individuals with a G4 compound genotype were more likely to acquire HIV than individuals with a G1 compound genotype (OR 1.72, P = 0.016) and the risk increased when individuals possessing CCR5delta32 were omitted from consideration (OR 2.13, P = 0.005). Among seroconverters lacking CCR5delta32, those who had the G4 compound genotype progressed significantly slower to AIDS-1993 than those with the G1 compound genotype (median time to AIDS 7.6 versus 5.4 years; RH 0.65; P = 0.007). CONCLUSIONS: These data implicate the RANTES-403A allele as a risk factor for HIV transmission and as a protective factor for HIV progression.

CCR5 promoter polymorphism and HIV-1 disease progression. Multicenter AIDS Cohort Study (MACS).

BACKGROUND: The rate of progression to AIDS varies among individuals infected with HIV-1. Factors responsible include two inherited human alleles, CCR5 delta32 and CCR2-641, which alter the protein-coding regions for the HIV-1 coreceptors/chemokine receptors CCR5 and CCR2b. We tested the hypothesis that polymorphisms of the CCR5 promoter might affect the rate of progression of HIV-1 infected people to AIDS. METHODS: We used directed heteroduplex analysis to identify polymorphism in the CCR5 promoter. Promoter-variants were compared in vitro with a chloramphenicol acetyltransferase reporter gene, and in vivo by genotyping HIV-1 seroconvertors discordant at polymorphous loci. FINDINGS: An A/G polymorphism was identified at basepair 59029 (Genbank U95626) in the CCR5 promoter. Both promoter alleles were common (43-68% allelic frequency for 59029-A depending on race). When in-vitro promoter activity was measured, 59029-G had 45% lower activity than 59029-A (p=0.05). In a cohort of HIV-1 seroconvertors lacking both CCR5 delta32 and CCR2-641, 59029-G/G individuals progressed to AIDS on average 3.8 years more slowly than 59029-A/A individuals (p=0.004). 59029-G/A discordance did not correlate with discordant rates of infection. INTERPRETATION: Our results are consistent with the hypothesis that CCR5 is important in HIV-1 pathogenesis. CCR5 59029-G/G appears to be protective relative to CCR5 59029-A/A, and about twice as protective relative to CCR5 delta32 or CCR2-641. This effect may be the result of reduced CCR5 mRNA production. These results identify the first site in the CCR5 promoter that may be a useful target for treatment of HIV-1 infection.

Contrasting evolution of the human leukocyte N-formylpeptide receptor subtypes FPR and FPRL1R.

N-formylpeptides are phagocyte chemoattractants that act by binding to two structurally related receptors, FPR (formylpeptide receptor) and FPRL1R (FPR-like-1 receptor), which are encoded by the human genes FPR1 and FPRL1. Single nucleotide polymorphisms (SNPs) in the FPR coding region have been reported and two have been associated with the disease juvenile periodontitis; however, their frequency and linkage relationships are unknown. Here we systematically analyzed polymorphism in the open reading frames of FPR1 and FPRL1 by direct sequencing of cloned alleles from random blood donors from North America. For FPR1 we detected five non-synonymous SNPs and two synonymous SNPs in a sample of 26 chromosomes one each from 17 Caucasian and nine black random blood donors. Although all five non-synonymous SNPs were common in Caucasians, Blacks, and Asians, notable differences in allele frequency were found for each SNP in the different racial groups, suggesting differential selective pressures. We found that the FPR1 polymorphisms are linked in 15 common haplotypes. No polymorphisms were detected in FPRL1 after sampling 44 chromosomes from 36 random blood donors from the same three racial groups. Thus FPR1 and FPRL1, though they originated from a common gene, appear to have undergone markedly different evolutionary events.

Coreceptor choice and T cell depletion by R5, X4, and R5X4 HIV-1 variants in CCR5-deficient (CCR5delta32) and normal human lymphoid tissue.

Coreceptor utilization by HIV-1 is an important determinant of pathogenesis. However, coreceptor selectivity is defined in vitro, while in vivo critical pathogenic events occur in lymphoid tissues. Using pharmacological inhibitors, we recently provided evidence that coreceptor selectivity by the R5X4 dual-tropic isolate 89.6 was more restricted in ex vivo infected lymphoid tissue than in vitro [S. Glushakova, Y. Yi, J. C. Grivel, A. Singh, D. Schols, E. De Clercq, R. G. Collman, and L. Margolis (1999). J. Clin. Invest. 104, R7-R11]. Here we extend those observations using CCR5-deficient (CCR5Delta32) lymphoid tissue as well as additional primary isolates. We definitively show that neither CCR5 nor secondary coreceptors used in vitro mediate 89.6 infection in lymphoid tissue. We also demonstrate that restricted coreceptor use in lymphoid tissue ex vivo compared with in vitro utilization occurs with other dual-tropic primary isolates and is not unique to 89.6. For all strains tested that are dual tropic in vitro, severe CD4 T cell depletion in lymphoid tissue correlated with preferential CXCR4 use in this ex vivo system.

Polymorphism in the fractalkine receptor CX3CR1 as a genetic risk factor for coronary artery disease.

Coronary atherosclerosis is a major cause of death in industrialized countries. Monocytes, which play a key role in atherosclerosis, migrate into the vessel wall, presumably guided by specific chemoattractant and adhesion molecules. A compelling candidate for this role is the chemokine receptor CX3CR1, which is expressed on monocytes and acts as either a chemotactic receptor or an adhesion molecule, depending on whether its ligand, fractalkine, is presented free or membrane bound. A common variant of CX3CR1 was recently identified, encoded by the alleles I249 and M280, which form a common I(249)M(280) haplotype. When CX3CR1 genotypes were analyzed in 151 patients with acute coronary syndromes and in 249 healthy controls, CX3CR1 I249 heterozygosity was associated with a markedly reduced risk of acute coronary events, independent of established acquired coronary risk factors (eg, smoking, diabetes). The adjusted odds ratio for this allele was 0.43 (95% confidence interval, 0.26-0.72; P =.001). Consistent with this, functional analysis of peripheral blood mononuclear cells showed that CX3CR1 I249 heterozygosity was associated with a significant decrease in the number of fractalkine binding sites per cell. The results show that CX3CR1 I249 is an independent genetic risk factor for coronary artery disease and that CX3CR1 may be involved in the pathogenesis of atherosclerotic disease. (Blood. 2001;97:1925-1928)