This analysis of host genetics for HLA Class I alleles intersects with both the V1/V2 IgG response and the Env IgA response. (1) Vaccine efficacy for viruses with a lysine at position 169 was higher in those with the HLA A* 02 allele; (2) there was a direct correlation between plasma C1 Env IgA response and infection rate in the A* 02 (−) subgroup, but not the A* 02 (+) subgroup. The gene discussed is ERVW-1; the disease is infection.