High incidence of antibodies to HTLV-I tax in blood relatives of adult T cell leukemia patients

Adult T cell leukemia (ATL) is caused by the human T cell leukemia virus type I (HTLV-I). Although the mechanisms of the leukemogenic process are unknown, the tax gene may have a role in this process. Because clustering occurs with HTLV-Iand ATL, members of ATL families were examined for antibodies to the tax protein and compared with matched HTLV-I-positive blood donors. To investigate the antibody response to this protein, a plasmid, pBHX-4, was con-structed to express a recombinant tax protein (r-tax). For ATL patients and their HTLV-I anti-body-positive blood relatives, the rate of seroreactivity with the r-tax protein was 67.3 % (35/52), compared with 51.6%(97/188)for HTLV-Iantibody-positive control blood donors (P<.05). The difference between direct offspring of ATL patients and matched HTLV-Iblood donors was even greater (84.2 % [16/19] vs.44.2 % [42/95]; P <.(05). Thus, tax antibody positivity in direct offspring of ATL patients may reflect differences in time or route of HTLV-I infection. Alternatively, it might reflect genetic differences in host susceptibility or virus strain. Human T cell leukemia virus type 1 (HTLV-I) is the etio-logic agent of adult T cell leukemia (ATL) [1, 2]. It is not clear how the virus causes this disease. The HTLV-I proviru