The Biology of RNA Tumour Viruses

Abstract

RNA tumour viruses, or oncoviruses as they are now called, belong to the family Retroviridae, comprising the retroviruses which also include foamy virus (Spumavirinae) and Maedi/Visna virus (Lentivirinae). Oncoviruses are divided according to a morphological classification into Type B, C and D viruses (1). Type C viruses have been isolated from or identified in numerous vertebrate hosts ranging from fish to mammals, and also from mosquitos. Oncoviruses are known to cause a variety of neoplasms in their natural host species. Thus the lymphomatous leukoses of cattle, cats, mice and chickens are typically caused by Type C oncoviruses, whereas Type B and D oncoviruses are associated with mammary carcinomas. Rare, acute neoplasms, such as sarcomas, and erythroid and myeloid leukaemias,are also recognised to result from retrovirus infection, as well as non-malignant diseases, such as osteopetrosis in chickens, anaemia in cats, and possibly autoimmune and paralytic diseases in mice. The problem of identifying retroviruses with neoplastic potential in humans remains equivocal, although tantalising items of evidence continue to be thrown up, as exemplified by Thiry’s contribution to this volume.