Implication of the c-terminal domain of nef protein in the reversion to pathogenicity of attenuated SIVmacBK28-41 in macaques

We have analyzed the nef gene sequences amplified from 12 macaques presenti ng various patterns of infection with SIVmacBK28-41, a clone derived from a ttenuated SIVmacBK28. We have observed seven mutation hot spots at position s 56, 75, 432, 588, 680, 699, and 779. The major alteration was a thymidine insertion at position 699, leading to a frameshift in the SIVmacBK28-41 ne i gene and changing the last 15 amino acids of Nef into a 31-amino-acid-lon g C-terminal domain nearly identical to that encoded by pathogenic SIVmac23 9 and SIVmac251. The insertion was found at early time points in proviruses obtained from rapid progressor macaques, after 2 years postinfection in pr ogressors, and rarely or only after 4 years postinfection in nonprogressors . Fixation of the other mutations occurred only after insertion of thymidin e 699. Phylogenetic analysis demonstrated that the nef genes isolated from progressors evolved from the allele present in SIVmacBK28-41 to alleles pre sent in SIVmac239 or SIVmac251, whereas nef sequences from nonprogressors s tayed clustered with that of the inoculated molecular clone. These data str ess the importance of the C-terminal extremity of the Nef protein of SIVmac 239 or SIVmac251 in viral pathogenesis, (C) 2000 Academic Press.