Human herpesvirus type 6 and cytomegalovirus in AIDS-associated Kaposi's sarcoma: no evidence for an etiological association.

Epidemiological studies indicate that acquired immune deficiency syndrome (AIDS)-associated Kaposi's sarcoma (KS) may be caused by an infectious, preferentially sexually transmitted agent. Herpesviruses infections are common sexually transmitted diseases in homosexual men, who are also the main risk group for developing Kaposi's sarcoma. To evaluate a possible role of human herpesvirus-6 (HHV-6) and cytomegalovirus (CMV) in the development of AIDS-associated KS, we investigated cutaneous AIDS-associated KS in 26 AIDS patients using the polymerase chain reaction (PCR) and immunohistochemistry (IHC) to detect the presence of HHV-6 and CMV. Human herpesvirus-6 was detected in nine of 26 Kaposi's sarcoma specimens (all cases were HHV-6 subtype B) and in eight of 27 normal skin specimens from human immunodeficiency virus (HIV) seropositive and HIV seronegative patients (one case was HHV-6 subtype A and seven cases were HHV-6 subtype B). In two of four patients showing HHV-6 in KS of the skin, the virus also was detected in other investigated tissues, such as heart, lung, liver, kidney, and adrenals. Cytomegalovirus was detected only in AIDS-associated KS (seven of 26 KS specimens) and not in normal skin tissues of HIV-seropositive and HIV-seronegative patients. Cytomegalovirus was detected in other organs of those patients showing CMV in Kaposi's sarcoma. Our data indicate that the presence of HHV-6 and CMV in AIDS-associated KS most likely reflects disseminated viral infection. Human herpesvirus-6 and CMV may be cofactors but not the only causative agents for the development of AIDS-associated KS.