CYTOTOXIC T-CELL RESPONSE AND AIDS-FREE SURVIVAL IN SIMIAN IMMUNODEFICIENCY VIRUS-INFECTED MACAQUES

Objective: To determine whether cytotoxic T lymphocytes have a benefic ial effect during infection with the simian immunodeficiency virus (SI V) in macaques. Design and methods: We followed up 12 rhesus macaques experimentally infected with SIV. Cytotoxic T lymphocytes were detecte d in nine macaques, who were subdivided into a group of high responder s (n = 6), with a sustained and polymorphic response directed against most SIV proteins, and a second group of weak responders (n = 3), in w hich the responses were only transient and directed against only a few proteins. A third group was characterized by the absence of any cytot oxic T-lymphocyte response (n = 3). Proliferative responses closely pa ralleled cytotoxic responses in intensity and evolution. Results: Clin ical profiles and CD4 cell counts were markedly linked to cytotoxic ac tivity; five out of six that responded to multiple proteins were still healthy 2 years after SIV infection, with two of them presenting a de crease in circulating CD4 cells concomitant with the disappearance of the cytotoxic T-lymphocyte response. Conversely, five non-responder or weak-responder macaques developed overt disease after 4-21 months. Co nclusions: These data suggest that a cytotoxic response may predict a better clinical outcome.