Unintegrated HTLV-I proviral DNA in cell lines and uncultured peripheral blood mononuclear cells from tropical spastic paraparesis (TSP/HAM) and adult T-cell leukemia (ATL) patients.

Ultrastructural studies on cell cultures derived from TSP/HAM and ATL patients, show the presence of large quantities of HTLV-I viral particles in extracellular spaces and budding at the cytoplasmic membrane. In addition, mature enveloped particles and images of endopinocytosis of virions are seen in the cytoplasm vacuoles suggesting the existence of a reinfection phenomenon. In this context, we decided to investigate some features of the replicative cycle, in particular the synthesis of unintegrated proviral forms. To increase the sensitivity of detection, we applied a procedure which combines the electrophoretic separation of closed circular forms and PCR amplification. By this procedure we produced evidence for the existence of supercoiled HTLV-I DNA in established cell lines from TSP/HAM and ATL and in patients peripheral blood mononuclear cells. These HTLV-I unintegrated proviral forms may play an important role in the physiopathology of HTLV-I associated diseases. Preliminary results of AZT/interferon treatment in ALT patients are largely superior to chemotherapy. The therapeutic effect of AZT, it known inhibitor of reverse transcriptase, may be through its inhibition of the synthesis of HTLV-I unintegrated proviral DNA.