Stimulation of HTLV-I expression by subtoxic dose of 3-methylcholanthrene

In vivo infection by HTLV-I is characterized by the lack of virus expression in the host's infected cells and in most cases it is clinically inapparent. The present study shows that exposure of HTLV-I-infected human T-cells to a maximal non-toxic dose of 3-MC remarkably enhances virus expression. This stimulatory effect was demonstrated by showing elevated levels of viral RNA and proteins within the cells and increased virus release to the culture medium. The enhanced virus expression was found to increase the ability of the treated cells to infect normal human peripheral lymphocytes in co-culture. Such data point to the possibility that initiation of a pathogenic process in HTLV-I-infected individuals might result from activating the expression of the latent provirus by environmental carcinogens.