GENETIC-VARIATION IN A HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-2 LIVE-VIRUSMACACA-NEMESTRINA VACCINE MODEL

Four pigtailed macaques were inoculated with an infectious, apathogeni c human immunodeficiency virus type 2 (HIV-2) molecular clone (HIV-2,) and subsequently challenged with a highly pathogenic strain, HIV-2(28 7), together with two naive control animals. After challenge, two anim als inoculated,vith a high dose of the immunizing strain were protecte d from CD4 decline and immunodeficiency. To examine the role of geneti c heterogeneity in protection, fragments of the env gene were amplifie d from peripheral blood mononuclear cell DNA and plasma RNA of challen ged animals by PCR, examined by using a heteroduplex tracking assay (H TA), and sequenced. By HTA, variation was detected principally within the V1 and V2 regions of envelope. Extent of variation in viral DNA cl ones as assessed by HTA correlated with inoculum size, as did the degr ee of variation in sequences of clones derived from viral DNA. Convers ely, a rapid reduction in the number of plasma viral RNA variants was noted by HTA at 8 weeks postinfection in protected animals; this reduc tion was not present in naive or unprotected macaques. Sequences deriv ed from plasma viral RNA were found to be more closely related than co rresponding viral DNA sequences, and protection correlated with a sign ificant reduction in variation in plasma RNA sequences in animals give n the identical inocula of HIV-2(287). Nonsynonymous mutations were si gnificantly less prevalent in the protected animals. An additional pot ential glycosylation site was predicted to be present in the V2 region in all but one clone, and amino acid signatures related to protection were identified in viral DNA and RNA clones within both the V1 and V2 regions. Examination of the role of viral variation in this HIV-2 liv e-virus vaccine model may provide valuable insights into immunopathoge nesis.