The roles of human viruses in the pathogenesis of lymphoma

There are two families of viruses that contribute to lymphomagenesis in humans: herpesviruses and retroviruses. The two herpesviruses are the Epstein-Barr virus (EBV) and human herpesvirus-8 (HHV-8). EBV is an extremely well-characterized transforming agent: nine viral proteins contribute to transformation in vitro. In contrast, in vivo, the pattern of EBV gene expression varies with different types of malignancies. EBV is associated with endemic Burkitt's lymphoma, acquired immune deficiency syndrome (AIDS)-related lymphoma, post-transplantation lymphoproliferative disease, Hodgkin's disease (HD), and rare T-cell lymphomas. We have summarized studies on the different patterns of viral gene expression and signaling in different EBV-related malignancies, which have begun to reveal how EBV variably contributes to the malignant phenotype in different diseases. HHV-8 is associated with primary effusion lymphomas in patients with AIDS, and the rapidly accumulating information on this virus is summarized. Human T-cell leukemia virus-1 (HTLV-1) is a retrovirus which is the causative agent of adult T-cell leukemia/lymphoma (ATL). The specific mechanism of HTLV-1-mediated T-cell transformation is unclear, but the effects of HTLV-1 on interleukin-2 signaling are reviewed.