Retroviruses and malignant lymphoma.

Retroviruses are single stranded RNA viruses that possess a unique enzyme, reverse transcriptase. This enzyme facilitates the synthesis of double stranded DNA intermediates able to integrate into the genome of the host cell. Although primarily a means of remaining latent, this integration can have the effect of transforming the cell to malignant growth, either by activation of growth control genes in cis or trans, or by insertion of an integrated oncogene. Malignant lymphomas caused by retroviruses occur in animals from mice to man, and have increasing economic and clinical significance. HTLV-1 is the causative agent of adult T-cell leukemia/lymphoma which is endemic in certain discrete locations of the world and has been implicated in a variety of other disorders. The fact that the virus seems to be spreading through groups of intravenous drug abusers in much the same way as the AIDS virus is a cause for concern.