The Hopkins HIV Report A bimonthly newsletter for healthcare providers Volume 8, Number 4, November 1996

News From ICAAC: Kaposi's Sarcoma

By Alfred J. Saah, M.D., M.P.H.

Kaposi's sarcoma herpes-like virus (KSHV) is becoming more closely linked with clinically manifest KS, but its true etiological role in the development of KS and the factors surrounding its transmission and incubation period are unknown at this time. There are, however, serological data indicating that infection with KSHV antedates the development of KS, a first step in demonstrating causality.

At ICAAC, Dr. Keolle, from Dr. Corey's group in Seattle, presented data on KSHV in saliva. Most of the data came from DNA PCR; however, several positive cultures were also reported. The table summarizes the results of the study.

Dr. Koelle and colleagues also tested saliva for EBV and HHV-6. Both are herpesviruses; the former is primarily transmitted by saliva, and the latter is thought to be transmitted by saliva. In those who were positive for KSHV and one of the other viruses, KSHV levels by PCR were 100-fold lower than EBV levels but were equivalent to levels of HHV-6. Based on these data and a few cultures from saliva, it was suggested that saliva may be an important source of transmission of KSHV.

It is not clear how to reconcile these findings with the highly circumscribed epidemiology of KS. The seroepi-demiology of KSHV antibody clearly reflects non-ubiquitous transmission, as does clinically manifest KS. Transmission by saliva would mean that KSHV infection would be much more highly prevalent, perhaps universal, like the other herpesviruses that have been discovered. However, KS is distinctly uncommon among HIV-infected injection drug users and hemophiliacs. Even among gay men, it is clear that KS is associated with higher levels of sexual activity. If saliva were an important means of transmission, KS should be seen in a higher proportion of gay men than the 20 to 30% who now develop it.

Much more work is necessary to identify the mode of transmission of KSHV. The clues at the present time point to semen as the likely vehicle of transmission of KSHV, but the sexual practices that may enhance transmission are unknown at this time. If we think back to the early days of defining the route of transmission of HIV among gay men, we can see the risk of anal receptive intercourse emerged as the predominant means of transmission, allowing us to be more rational in recommendations about saliva, tears and urine. In a similar fashion, heterosexual transmission studies showed that factors such as genital ulcer disease and lack of circumcision increased the likelihood the transmission of HIV. Similar work needs to be done in order to define the transmission of KSHV.

* The 17 who were positive in saliva and PBMC by PCR were the same individuals. However, the 2 who were PBMC PCR+ were different individuals than the 2 who were saliva PCR+ for KSHV DNA, thus making the total positive 4 of 17. +PBMC = Peripheral blood mononuclear cells.