Objectives: Kaposi's sarcoma-associated herpesvirus (KSHV), a newly discovered human gammaherpesvirus, is found in the majority of KS lesions from patients with and without AIDS. Peripheral blood mononuclear cells (PBMC) were examined for KSHV DNA to determine whether viral infection precedes onset of this neoplasm.

Design: Randomized and blinded case-control study of prospectively collected PBMC samples from ongoing cohort studies.

Methods: Paired PBMC drawn before and after KS onset from 21 AIDS-KS patients were compared to paired PBMC from 23 high-risk HIV-infected homo-/bisexual patients who did not develop KS and to a single PBMC sample from 19 low-risk, HIV-infected hemophiliac patients. Extracted DNA samples were amplified by polymerase chain reaction (PCR) using two non-overlapping nested primer sets to control for potential PCR contamination.

Results: In all comparisons, patients who went on to develop KS were significantly more likely to show evidence of KSHV infection prior to onset of KS than either control group. Of PBMC samples from AIDS-KS patients drawn prior to KS, 52% were positive for KSHV DNA whereas both high- and low-risk control groups had lower rates of PBMC infection (9-13%). KSHV infection can precede KS onset by up to 21 months among AIDS-KS patients.

Conclusions: AIDS-KS patients are significantly more likely to show evidence of KSHV infection in PBMC prior to KS onset than control HIV-infected patients. Because identical PBMC samples from cases and controls were examined blindly, these results are not caused by a bias in tissue sampling. Homo-/bisexual and hemophiliac AIDS patients who do not develop KS appear to have a low prevalence of infection. These findings indicate that KSHV infection is specifically associated with the subsequent development of KS in AIDS patients.