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.

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.

Combinatorial content of CCL3L and CCL4L gene copy numbers influence HIV-AIDS susceptibility in Ukrainian children.

OBJECTIVE: CCL3L and CCL4L genes encode HIV-suppressive chemokines, colocalize on chromosome 17q12 and have copy number variation. Copy number variation of CCL3L associates with HIV-AIDS susceptibility. Here, we determined the influence of the combinatorial content of distinct CCL3L and CCL4L genes on HIV-AIDS susceptibility. METHODS: By designing gene-specific assays, the association between doses of all CCL3L or CCL4L genes or their individual duplicated components (CCL3La/b and CCL4La/b) with HIV-AIDS susceptibility was determined in 298 perinatally exposed Ukrainian children. RESULTS: The odds of transmission was increased in children with less than two copies of CCL3L or CCL4L, compared with those with at least two copies, and 10-fold higher when both mother and offspring had less than two CCL3L or CCL4L copies, compared with mother-child pairs with at least two copies. The extent of the pair-wise correlations between CCL3La, CCL3Lb, CCL4La and CCL4Lb copy number varied extensively, with an inverse correlation between CCL4L genes that transcribe a classical chemokine (CCL4La) versus aberrantly-spliced transcripts (CCL4Lb). Children possessing only CCL4Lb progressed four times faster to AIDS than those with only CCL4La. A lower content of CCL3L and CCL4L genes that transcribe classical chemokines was associated with enhanced HIV-AIDS susceptibility. CONCLUSION: Transmission risk is greatest when mother and offspring both have low CCL3L or CCL4L gene doses. The impact on HIV-AIDS susceptibility of the chemokine gene-rich locus on 17q12 is dependent on the balance between the doses of genes conferring protective (CCL3La and CCL4La) versus detrimental (CCL4Lb) effects. Hence, the combinatorial genomic content of distinct genes within a copy number variable region may determine disease susceptibility.