Sexual transmission places the receptive partner at the greatest risk. Having multiple sexual partners is considered a very high risk behavior. The cellular receptor for HTLV is unknown. It is likely that HTLV can penetrate and infect many different cell types, however productive infection is observed in only a few cell types. HTLV establishes a lifelong persistent infection which usually remains subclinical, but occasionally produces disease after an incubation period ranging from ten to forty years.
Clinical manifestations vary.
The molecular mechanisms that HTLV uses to transform T cells is unknown. HTLV carries no viral oncogene. The oncogenic potential of the virus is linked to the regulatory gene tax , which transactivates transcription of proviral LTR, cellular oncogenes, and the cellular gene encoding the growth factor inerleukin-2 receptor. This can cause a cascade of events that has the potential to lead to cancer by inducing autocrine stimulation of T-cell proliferation. Most HTLV infections remain asymptotic.