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 superinfectio n by human immunodeficiency virus (HIV) can exist in vivo. Asymptomati c baboons (Papio cynocephalus), previously infected with HIV-2, were f irst challenged with homologous virus (HIV-2(UC2) or HIV-2(UC14)) and later with heterologous virus (HIV-2(UC12)). After both virus inoculat ions, either resistance to viral infection or a transient viremia was observed. The original virus was recovered in 3 baboons, suggesting th at reactivation of a latent infection occurred on heterologous challen ge and that HIV-2 superinfection is blocked by processes established d uring prior infection. Antibody titers measured by ELISA and virus neu tralization remained at low levels. However, suppression of HIV-1 repl ication was observed with CD8 T cells and filtered cell culture supern atants. The soluble factor involved was not a beta-chemokine. This res istance to HIV superinfection appears to be mediated at least in part by CD8 T cells that suppress virus production.