Recombination in human herpesvirus-8 strains from Uganda and evolution of the K15 gene

Human herpesvirus-8 (HHV-8) is believed to be the aetiological agent of Kap osi's sarcoma (KS). KS accounts for half the reported cancer cases in Ugand a, and occurs in endemic and epidemic [human immunodeficiency virus (HIV)-a ssociated] forms. We confirmed a high prevalence (74%) of HHV-8 antibodies in 114 HIV-negative Ugandan blood donors, and characterized the genomes of HHV-8 strains present in 30 adult Ugandan KS patients. Phylogenetic, analys is of the uniquely variable KI gene indicated that the majority of KS patie nts were infected by the B subtype of HHV-8, several by the A5 subtype, and one by a variant of the C subtype. Sequence analysis of nine strains at se veral other genome loci spaced out across the genome indicated that five ar e recombinants between subtypes when considered independently of previously published definitions of parental (unrecombined) genotypes. When previousl y published parental genotypes were taken into account, seven of the nine s trains appeared to be recombinants. Analysis of the K15 gene, which exists in HHV-8 in two highly diverged alleles, indicated that the P allele predom inates, with only a single strain bearing the M allele. Divergence between the M allele in the latter strain and that in the previously sequenced BC1 strain is at least as great as that between representatives of the P allele . This indicates that introduction of the M allele into extant HHV-8 subtyp es did not occur by a single, relatively recent recombination event as was concluded from a previous study in which very limited variation in the M al lele was reported.