Specifically, perturbation to the SIV Env-CT presents in vivo with delayed progression to disease in rhesus macaques, and robust control of the infection mediated by CD8+ T cells and/or NK cells in pigtail macaques, showing reduced infection in gut tissue and macrophage cells compared to wild-type SIV (25, –, 28). The gene discussed is ERVW-1; the disease is infection.