Placental CCR5 polymorphisms in relation to fetal growth

The placenta mediates fetal growth, and its development and function are influenced by immune interactions at the maternal-fetal interface. The cysteine-cysteine chemotactic cytokine receptor type 5 (CCR5) gene codes for a pro-inflammatory protein receptor expressed in the placenta on syncytiotrophoblasts and Hofbauer cells. Associations of the placental-fetal genotype at CCR5 and birth outcomes have not been examined. Furthermore, influence of CCR5 polymorphisms on nearby DNA methylation in the placenta and in the context of infection is understudied. We assessed two functional polymorphisms in CCR5, a 32 base pair deletion (Δ32) in the open reading frame and an A/G promoter point mutation (rs1799987) in EPIC (n = 233) a cohort consisting of complicated and uncomplicated pregnancies ascertained in Vancouver BC and found that the variant alleles were associated with birth weight (p = 0.007 and p = 0.01 respectively). We validated the association of rs1799987 with birthweight (p = 0.003) in the published NICHD dataset of normative term births (n = 286). These variant associations were, however, not present in CARMA-Preg (n = 200) a cohort enriched for HIV-exposure. Interestingly, we found rs1799987 was associated with altered DNA methylation (DNAme) at multiple CpGs spanning over 275 kb, overlapping both the CCR2 and CCR5 genes. DNAme in this region was, however, not associated with birthweight. Further investigations are needed to validate the association of CCR5 variants with fetal growth. Such studies must consider the population structure and demographics, as well as the large haplotype blocks spanning this region, which make it difficult to assign a causal relationship to specific variants.