Distinct distribution of rare US genotypes of Kaposi's sarcoma-associated herpesvirus (KSHV) in South Texas: Implications for KSHV epidemiology

Genotypes of Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) from patie nts with KS in South Texas were examined. Open-reading frame (ORF)-K1 and O RF-K15 DNA segments from 16 KSHV isolates were amplified by polymerase chai n reaction, and KSHV subtypes were assigned on the basis of sequence variat ions. K1 genotyping showed that 75% exhibited C subtype and 25% exhibited A subtype. K15 genotyping showed that 56% exhibited M form, of which 89% exh ibited C3 K1 subtype and 44% exhibited P form. A unique isolate was found a nd was classified as C6 clade. All of the M KSHV isolates had been obtained from human immunodeficiency virus-negative classic KS patients >50 years o f age, of whom 78% were Hispanic. Conversely, all KS patients with AIDS wer e <36 years of age and exhibited P form KSHV. These findings indicate that C3/M KSHV genotypes are more prevalent in South Texas (50%) than in other U S regions (3%) and that M form KSHV likely existed in this region long befo re the AIDS epidemic.