Divergent KSHV/HHV-8 subtype D strains in New Caledonia and Solomon Islands, Melanesia

Abstract : KSHV/HHV-8 is the etiological agent of Kaposi's sarcoma, primary effusion lymphoma and most multicentric Castleman's disease cases. KSHV exhibits a high genetic variability comprising five genotypes (A-E). Few data are yet available concerning the situation of KSHV, its genetic variability and the associated diseases in Melanesia. We performed a study on 626 natives Melanesians from New Caledonia and Vanikoro Island to evaluate KSHV seroprevalence and characterize molecularly the viral strains. Plasma from 343 males and 283 females (age range: 15-86 years, mean age: 60) were tested for KSHV latent antibodies by an immunofluorescence assay (IFA) using BC-3 cells. DNAs extracted from peripheral blood buffy-coat of KSHV seropositive individuals were amplified to obtain a 737-bp fragment of the ORF-K1 gene. Phylogenetic analyses were then performed. Among 626 samples, 148 were IFA positive (dilution≥1:80). The overall seroprevalence was 23.6% (25.2% in New Caledonia, 17.5% in Vanikoro). Fifteen (8 men and 7 women, mean age 69 years) out of 148 DNA samples were found PCR positive. All ORF-K1 sequences belonged to KSHV genotype D. A geographic clustering according to the island of origin of KSHV infected persons was clearly observed with sequences from New Caledonia clustering with most Vanuatu strains. New Caledonia and Vanikoro are endemic for KSHV with a high diversity of genotype D variants. These strains were probably introduced into New Caledonia during multiple waves of migrations of Melanesian and Polynesian individuals that have colonized this archipelago.