MUTATION-RATES IN LTR OF HTLV-1 IN HAM TSP PATIENTS AND THE CARRIERS ARE SIMILARLY HIGH TO TAX/REX-CODING SEQUENCE/

The genomic sequence of human T-cell leukemia virus type 1 (HTLV-1) is highly conserved, although minor sequence variations enable classific ation of the isolates into several subgroups. We previously reported, however, that the Tax-coding sequence of HTLV-1 genome is highly varia ble in a random fashion within individuals with HAM/TSP and asymptomat ic carriers. Here, we describe frequent base substitutions in the LTR sequence similarly to those in Tax-coding sequence. These observations indicate that frequent mutations are not unique to the sequence encod ing the most effective antigen for cytotoxic T lymphocytes, but also s een in the LTR, a non-coding sequence. Thus, frequent mutations seem t o occur during the viral replication process rather than the selection of fare mutants by immune surveillance.