Human retroviruses and neoplastic disease.

Human retroviral infections result in significant neoplastic disease. Human T cell lymphotropic virus I (HTLV-I), the first human retrovirus to be discovered, is associated with the development of acute T cell leukemia with characteristic hypercalcemia and skin lesions after many years of chronic infection of CD4+ cells. HTLV-I also produces myelopathy. A minor T cell immunodeficiency occurs in HTLV-I acute T cell leukemia with associated strongyloidiasis and Pneumocystis carinii pneumonia. Human T cell lymphotropic virus II (HTLV-II) is found to be endemic in Amerindians and intravenous drug users (IVDUs) and has been linked to some cases of hairy-cell leukemia. HTLV-II infects the CD8+ population, with significant cell-associated viremia. Clinical neurological disease is rare, with one patient with myelopathy having been described. Immunodeficiency does not seem to occur. Human immunodeficiency virus 1 (HIV-1) produces aggressive large cell and Burkitt's lymphoma in as many as 10% of HIV-1-infected patients. More than 20% of homosexual men infected with HIV-1 develop Kaposi's sarcoma (KS). The pathogenesis of KS is better understood through studying KS-like cell lines that induce angiogenic factors. In some patients HIV-1 and HTLV-I or HTLV-II infections occur concomitantly. HIV-1 accelerates the tumorigenesis of HTLV-I and produces unusual skin diseases when combined with HTLV-II. Immunodeficiency occurs in all HIV-1-infected patients.