Preclinical studies in nonhuman primates were conducted, showing that immunization with the Tat protein or tat DNA in cynomologous macaques is safe, elicits a broad and specific immune response, and, most importantly, induced a long-term protection against infection with the pathogenic X4-tropic SHIV89.6P, an SIV that carries the HIV-1 tat and env genes, which rapidly causes AIDS and death in these monkeys [123,124,125,126,127,128]. The gene discussed is ERVW-1; the disease is infection.