High incidence of human type-C retrovirus (HTLV) in family members of a HTLV-positive Japanese T-cell leukemia patient.

Sera and peripheral blood cells of an adult T-cell leukemia patient and several clinically normal members of his family from the northwest coast of Japan were examined for evidence of infection with human T-cell leukemia (lymphoma) virus (HTLV). The sera of the patient and his parents had antibodies to HTLV, whereas these antibodies were absent in the sera of the patient's brother and sister. T-cell lines were established from the peripheral blood lymphocytes of all of the family members, and all except the patient's sister expressed HTLV antigens (p19, p24, and reverse transcriptase) and type-C virus particles. Not only the fresh peripheral blood lymphocytes from the patient but also those from his clinically normal mother showed abnormal morphology of the kind characteristic of some patients with T-cell leukemia. These studies are consistent with previous evidence indicative of a high rate of HTLV infection within families, and they show that people whose sera are negative for antibodies may still be infected by HTLV. In addition, the results indicate that infection of T cells by HTLV can be associated with morphological transformation of the cells without other signs of leukemia.