Molecular epidemiology of Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 strains from Russian patients with classic, posttransplant, and AIDS-associated Kaposi's sarcoma.

We report the molecular characterization of 38 new Kaposi's sarcoma-associated herpesvirus (KSHV) strains from Russian patients with either classic (25 cases), epidemic/AIDS-associated (7 cases), or posttransplant/immunosuppressed patients (6 cases), or Kaposi's sarcoma (KS). While a complete sequence of the K1 gene (870 bp) was obtained from 30 strains, only partial sequences of the hypervariable regions VR1 (372 bp) and/or VR2 (381 bp) of the K1 gene were obtained from eight strains of KS paraffin blocks. Sequence comparison and phylogenetic studies indicate that the novel KSHV strains belong to either the A subtype (28 cases) or the C subtype (10 cases). Within the 28 strains of A subtype, 24 (86%) belong to the large A' subgroup, mostly A1 and A1' clades, and 4 belong to the A" subgroup, mostly A3 clade. Within the 10 strains of subtype C, 4 were of C' subgroup, and 6 of the C". Some molecular variants of subtype A' were observed, with 3 strains exhibiting an insertion of a single amino acid at the position 65 and 2 strains (both from AIDS-KS) with an unique deletion of 17 amino acids in the VR2 region. Polymerase chain reaction-based subtyping of the K14.1 genomic region indicated that most (23/32) of the novel strains belonged to the P subtype. The results indicate that despite a wide genetic diversity of A and C K1 subtypes of KSHV strains present in Russia, most are closely related and belong to the A1 or A1' molecular clades suggesting a common origin. This study also expands the data regarding the absence of any correlation between a K1 molecular subtype and a specific KS type (classic, epidemic, or posttransplant), as well as between the K1 and K14.1 molecular subtypes.