GenomicCloning andComplete Sequence Analysis ofa Highly Divergent African HumanImmunodeficiency VirusIsolate

Analysis ofthecomplete sequenceofa humanimmunodeficiency virus (HIV)isolate (Ant7O) obtained from a Cameroonian patient indicates thatthis virus isthemostdivergent strain within theHIV-1family hitherto described. Comparison ofthePolprotein, usually highly conserved within theHIV-1family, showsonlyabout 73%similarity withtheHIVmnisolate, whereas forthemore variable proteins suchasenvelope, similarities of50%orlower arefound. Theprincipal neutralizing determinant (V3loop) andtheimmunodominant region within gp4lalsocontain some unusual substitutions, which may haveimplications forprotein function aswell asforserological assaysbased on these regions. Phylogenetic analyses showthatthis isolate occupies aunique position relative tothehumanHIV-1isolates andtherecently described SIVcpz virus, indicating thatthis Cameroonian isolate may provide us withnew insights intotheorigins oftheHIV-1family. Twodistinct typesofthehumanimmunodeficiency viruses (HIV)havebeendescribed astheresponsible etiologic agents ofAIDS(5,9,10,21,22,56,61). Although bothtypes, HIV-1 andHIV-2, cause a dysfunction oftheimmunesystemand induce similar clinical symptomsininfected persons,they are genetically distinct (11). Inaddition tothethree major genesgag,pol, andenv-common toall retroviruses, genescoding for regulatory proteins arefoundintheHIVgenome (3,11,27, 45). Thesesupplementary genes arefoundinbothvirus types exceptforthedouble-spliced vpuandvpxopen reading frames, which areunique toHIV-1andHIV-2, respectively. Epidemiological studies haveshownthattheprevalence of