Reexamination of the coding potential of the HTLV-1 pX region

The human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T cell leukemia (ATL) and tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). In addition to tax and rex genes eight additional open reading frames are present in the pX region of HTLV-1. The possibility that these open reading frames can encode a protein in human cell lines persistently infected by HTLV-1 or in COS-1 cells transfected with a pX expressor plasmid was investigated. The results presented here indicate that tax and rex are the only proteins detected. Moreover, antibodies against proteins in vitro translated by five of the additional open reading frames of the pX region were not found in sera of ATL and TSP/HAM patients, further indicating that those proteins are not usually made in infected cells.