CXCL12 and AIDS: Homozygosity for the Δ32 (rs333) allele of CCR5 was found to provide protection against infection with CCR5-tropic HIV clades [5,6], and homozygous “A” alleles in the 3’ untranslated region of CXCL12 (C-X-C motif chemokine 12, also known as stromal cell-derived factor 1, SDF-1) was discovered to delay AIDS progression [7].