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Background:  Evidence is now strong that Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiologic agent of all forms of KS. Whether the different KSHV strains vary in infectiousness or virulence is still unclear. We evaluated the relationship between KSHV strains among KS symptomatic and asymptomatic HIV-infected individuals from Zambia.

Methods:  Children who presented with mucocutaneous or lymphadenopathic KS lesions and asymptomatic HIV-infected individuals were enrolled into the study. DNA was extracted from peripheral blood mononuclear cells (PBMC) and KS tissues. The KSHV K1 gene was amplified by PCR.  We have applied a heteroduplex mobility assay (HMA) analysis to determine the diversity of KSHV К1 gene variants within infected individuals, and also determinate whether there is compartmentalization of the virus in different tissues, such as PBMC and KS tissues. For each individual, at least 10 independent K1 gene clones were sequenced. DNA sequences of the K1 gene were aligned and analyzed using PAUP version 4.0b8 software.

Results:  Surprisingly, HMA showed variation among K1 gene clones obtained from the same individual. We found that different K1 clones obtained from the same subject that exhibited distinct HMA heteroduplexes also had different sequences, and the level of divergence varied in each subject. The analysis of the KSHV K1 genes from KS patients showed that viruses with diverse genotypes were present in the PBMC while restricted K1 gene variants were found in the KS tumor tissue. As KSHV genome shows variation almost exclusively in the K1 gene we compared the K1 gene sequences from 8 children with KS tumors and 10 asymptomatic individuals from Zambia. Analysis of the consensus KSHV K1 gene sequences shows that certain group of closely related virus isolates was derived from children with KS tumor lesions. The virus isolates from this group had only 0.3 to 3% variation for this region on the nucleotide level in contrast with up to 18% variation observed in comparisons to all the other strains.

Conclusions:  Our study shows that HMA and sequence analysis revealed quasispecies of KSHV in all the infected Zambian individuals. Our study also found that HHV-8 strains may be compartmentalized; with quasispecies existing in PBMC and more restricted viral genotypes in the KS tumor tissue. These results suggest that KSHV virus isolates have different pathogenic potencies.

Keywords: Kaposi's sarcoma; AIDS; K1 gene