Seroconversion to Antibodies against Kaposi's Sarcoma–Associated Herpesvirus–Related Latent Nuclear Antigens before the Development of Kaposi's Sarcoma

Abstract

Background If Kaposi’s sarcoma–associated her- pesvirus (KSHV) is the cause of Kaposi’s sarcoma, serologic evidence of infection should be present in patients before the disease develops. Methods Using an immunoblot assay for two la- tent nuclear antigens of KSHV, we tested serum sam- ples from homosexual male patients with the ac- quired immunodeficiency syndrome (AIDS) with and without Kaposi’s sarcoma, HIV-infected men with he- mophilia, HIV-seronegative blood donors, and HIV- seronegative patients with high titers of antibodies against Epstein–Barr virus (EBV). Serial serum sam- ples obtained from patients with Kaposi’s sarcoma before the diagnosis of the disease were tested for evidence of seroconversion. Results Of 40 patients with Kaposi’s sarcoma, 32 (80 percent) were positive for antibodies against KSHV antigens by the immunoblot assay, as com- pared with only 7 of 40 homosexual men (18 per- cent) without Kaposi’s sarcoma immediately before the onset of AIDS. Of 122 blood donors, 22 EBV- infected patients, and 20 HIV-infected men with hemophilia, none were seropositive. When studied by the immunoblot assay over a period of 13 to 103 months, 21 of the 40 patients with Kaposi’s sarcoma (52 percent) seroconverted 6 to 75 months before the clinical appearance of Kaposi’s sarcoma. The median duration of antibody seropositivity for KSHV-related latent nuclear antigens before the diagnosis of Kapo- si’s sarcoma was 33 months. Conclusions In most patients with Kaposi’s sarco- ma and AIDS, seroconversion to positivity for anti- bodies against KSHV-related nuclear antigens occurs before the clinical appearance of Kaposi’s sarcoma. This supports the hypothesis that Kaposi’s sarcoma results from infection with KSHV