ROUTE OF TRANSMISSION OF KAPOSI'S SARCOMA ASSOCIATED HERPESVIRUS

Abstract

Background: Risk of Kaposi's sarcoma is strongly associated with infection with Kaposi's sarcoma associated herpesvirus (KSHV), but the route of transmission of this virus is unclear. Although the sero-epidemiology of KSHV is consistent with sexual transmission, the reason why it is more prevalent among homosexual men is uncertain. Methods: The study enrolled 202 men with AIDS in Sydney, Australia, between 1991-1993. Subjects were followed until 1996-to-determine whether KS developed. At baseline, subjects were interviewed regarding sexual behaviour and history of sexually transmissible diseases. Frozen serum was available on 51 of 71 subjects with KS (72%) and 78 of 131 subjects without KS (60%). Serum was tested for antibodies to KSHV latent nuclear antigen (LNA) by immunofluoresence assay. Serology for syphilis (TPHA), HSV2, and hepatitis A was measured blind to knowledge of KSHV and KS status. A case-control analysis was performed, comparing those seropositive for KSHV to those seronegative. Results: Ninety six percent of study participants reported male homosexual contact. Of those tested for KSHV, 26% (33) were seropositive. Insertive oro-anal contact with casual partners in the period prior to awareness of HIV infection was related to risk of KSHV seropositivity (OR 2.5, 95% CI 1.1-5.8). A variety of sexual practices in the period after the onset of HIV-related symptoms was also associated with KSHV seropositivity. The most strongly related activity in this period was oro-anal intercourse with regular partners (OR 8.4, 95% CI 1.5-46). KSHV seropositive men were non-significantly more likely to report a history of a variety of sexually transmissible infections, and this reached significance for a history of anal warts (p = 0.02). KSHV serology was related to serology for HSV2(OR 3.6, 95% CI 1.3-12), but not for Hepatitis A (OR 1.8, 95% CI 0.74-4.6) or syphilis (OR 1.3, 95% CI 0.45-3.61). Conclusions: The association in this study of antibodies to KSHV LNA with insertive oro-anal intercourse support the hypothesis that KSHV may be sexually transmitted by the fecal-oral route. Other data, based on sexual behaviour, history of sexually transmissible diseases, and serology to HSV2, suggest that other forms of sexual contact may also be potential routes of transmission of this agent.