Human herpesvirus-6 (HHV-6) in Hodgkin's disease: cellular expression of viral antigens as compared to oncogenes met and fes, tumor suppressor gene product p53, and interleukins 2 and 6.
Patients with Hodgkin's disease (HD) frequently show elevated serum titers against human herpersvirus-6 (HHV-6) and their tissues contain significantly increased numbers of cells with HHV-6 DNA. This may coincide with similar data of Epstein-Barr virus (EBV) infections. According to in vitro studies, Hodgkin- and Reed-Sternberg (RS) cells can be infected by HHV-6 and may be coinfected by HHV-6 and EBV. Both viruses are potentially oncogenic and also may interfere with the production of various cytokines. We now demonstrate by using immunohistological methods that HHV-6 antigens are present in 77.3% of the HD lymphomas, 37% of which contain the replication-associated p41 "early-late" antigen and 63% the late membrane antigen complex gp116/64/54. Monocytic cell populations including HD and RS cells are most frequently antigen-positive, while lymphoid cells are less frequently. These cells also express IL-6 and IL-6 receptors as well as the IL-2 receptor a chain (CD25), while only occasionally the IL-2 receptor beta chain (p70). IL-6 receptors are significantly more frequently expressed than IL-6 itself. HD and RS cells constitute a significant pool of proliferating cells as reflected by their 95% positivity for PCNA, yet tumor suppressor genes are found in only 21% and the proto-oncogenes fes and met are expressed in various types of cells. The data may indicate that both viruses possibly contribute to the course of the disease through polyclonal stimulations of cell proliferation and coincident dysregulation of the cytokine network control of cell function and proliferation. A direct oncogenic effect of EBV and HHV-6 in HD appears less probable.