Superinfection with Human Immunodeficiency Virus Type 2 Can Reactivate Virus Production in Baboons but Is Contained by a CD8 T Cell Antiviral Response

An animal model was used to assess whether resistance to superinfection by human immunodeficiency virus (HIV) can exist in vivo. Asymptomatic baboons (Papio cynocephalus), previously infected with HIV-2, were first challenged with homologous virus (HIV-2(UC2) or HIV-2(UC14)) and later with heterologous virus (HIV-2(UC12)). After both virus inoculations, either resistance to viral infection or a transient viremia was observed. The original virus was recovered in 3 baboons, suggesting that reactivation of a latent infection occurred on heterologous challenge and that HIV-2 superinfection is blocked by processes established during prior infection. Antibody titers measured by ELISA and virus neutralization remained at low levels. However, suppression of HIV-1 replication was observed with CD8 T cells and filtered cell culture supernatants. The soluble factor involved was not a beta-chemokine. This resistance to HIV superinfection appears to be mediated at least in part by CD8 T cells that suppress virus production.