The role of KIR and HLA polymorphism in HIV acquisition: association and in vitro functional studies (VIR1P.1159)

Abstract Polymorphism in the genes that encode the HLA antigens and the KIR receptors on NK cells influence both adaptive and innate immunity. We analyzed the role of HLA and KIR polymorphisms in HIV acquisition by comparing 405 HIV+ and 523 HIV- men in the Chicago MACS cohort. We found no significant association with any HLA allele, in contrast to the well established strongly protective effect of HLA-B*57:01 for HIV disease progression. The inhibitory KIR ligands are HLA class I epitopes and fall into the groups: HLA-C1,C2, HLA-Bw4, and HLA-A3/A11. Association analyses of individual KIR genes in the presence/absence of their cognate HLA ligand revealed that one KIR/HLA ligand genotype combination was protective for HIV acquisition. The HLA ligand genotype C1/C1 was protective compared to C1/C2 and C2/C2 but only with genotype KIR2DL3+/KIR2DL2- (OR = 1.76, p = 0.007). This KIR genotype marks homozygosity for the centromeric KIR A haplotype, which is more inhibitory, has fewer genes, and less diverse than KIR B haplotypes. Since C2 is the ligand for the KIR2DL1 receptor, and C1 is the ligand for the KIR2DL3 receptor, the protective association observed with C1/C1 homozygotes suggests that a lack of signaling via the strongly inhibitory KIR2DL1 receptor in addition to signaling via the KIR2DL3 receptor is protective. In vitro assays of NK cells from KIR2DL3 homozygous individuals demonstrate that C1/C1 vs C1/C2 and C2/C2 (C2+) genotypes are more active in terms of cytokine release.