ERVW-1 and infection: This analysis of host genetics for HLA Class I alleles intersects with both V2 sieve analysis and the Env IgA response. (1) Vaccine efficacy for viruses with a lysine at position 169 was higher in those with at least one FcγRIIC-118l allele; (2) direct correlation of plasma Env IgA with infection risk was only when FcγRIIC-118l was present.