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[A virus called HTLV-1. Virological and molecular aspects].

A VIRAL PATHOGEN: HTLV-1, the first oncogenic retrovirus discovered in man carries, in addition to the genes coding for its structural protein, genes for capside and matrix (gag), reverse transcriptase and integrase (pol), protease and envelope (env), a unique region (termed pX) of about 2 kb situated at the position 3' of the env gene that encodes for Tax and Rex regulator proteins. TAX AND REX: These two proteins play a role in the viral cycle. Rex acts at the post-transcriptional level; Its capacity to modulate Tax expression could allow the virus to establish a chronic infection with little expression. Tax stimulates viral transcription and also plays a fundamental role in leukecernogenesis by modifying the expression of several genes crucial for cell survival and proliferation. GENETIC STABILITY: The HTLV-1 genome sequence appears to be very stable. Specifically leukernogeneic or neurotrophic strains are unlikely to exist. However, despite this genetic stability, there are molecular variants related to the geographical origin of the virus.