Identification of multiple simian immunodeficiency virus (SIV)-specific CTL epitopes in sooty mangabeys with natural and experimentally acquired SIV infection

Host immune responses to SIV infection in sooty mangabeys are likely to be an important determinant of how such nonhuman primate species maintain asym ptomatic lentivirus infection. We have previously described two patterns of asymptomatic SIV infection in sooty mangabeys: low viral loads with vigoro us SIV-specific CTL activity in SIVmac239-infected sooty mangabeys, and hig h viral loads with generally weak or absent SIV-specific CTL activity in na turally infected sooty mangabeys, To define the specificity of the CTL resp onse in SIV-infected mangabeys, we characterized CTL epitopes in two natura lly infected and three SIVmac239-infected sooty mangabeys, Compared with th at in SIVmac239-infected mangabeys, the yield of SIV-specific CTL clones wa s significantly lower in naturally infected sooty mangabeys. All CTL clones were phenotypically CD3(+) CD8(+), and lysis was MHC restricted. Seven SIV CTL epitopes were identified in five sooty mangabeys: one in Gag and three each in Nef and Envelope (Env). The CTL epitopes mapped to conserved regio ns in the SIV genome and were immunodominant. Several similar or identical CTL epitopes were recognized by both naturally infected and SIVmac239-infec ted mangabeys that shared class I MHC alleles, To our knowledge, this is th e first report of SIV-specific CTL epitopes in sooty mangabeys, Longitudina l studies of viral load and sequence variation in CTL epitopes may provide useful information on the role of CTL in control or persistence of sn infec tion in sooty mangabeys.