Inspection of nonhuman primate orthologs indicates that CD4 residues Q165, K166, F170, along with KIDIV (aa 171–175) are conserved in 19 of 21 Old World monkeys, including those of Asian origin that are employed in NHP models of HIV infection, but are absent in New World monkeys and other mammals (Figs 6D, 6E and S3). This evidence concerns the gene CD4 and HIV infectious disease.