Masatoshi Fujishita

An enzyme-linked immunosorbent assay method was developed for the detection of antibodies to adult T-cell leukemia-associated antigens (ATLA). This new method, which is simpler than the currently used indirect immunofluorescence technique, should be useful for mass screening of anti-ATLA antibodies.

A total of 703 sera from 10 species of monkeys were examined for the presence of antibodies to adult T-cell leukemia (ATL)-associated antigens (ATLA). ATLA represent core protein(s) of ATL virus (ATLV) and ATLV-determined polypeptides. Anti-ATLA antibodies were found in all seven macaque species tested but not in three non-macaque species. The frequencies of seropositive macaques ranged from 10 to 50%. In three macaque species (Japanese monkeys, rhesus monkeys, and crab-eating monkeys) in which sufficient numbers of animals were studied, more females than males were anti-ATLA positive and the antibody-positive rate increased with age. In Japanese monkeys, over 70% were seropositive after the age of 10 years. A family study of Japanese monkeys suggested maternal transmission of ATLV or a closely related agent. These seroepidemiological features are consistent with those of Japanese in the ATL-endemic area. Three of 10 rhesus monkeys were found to be anti-ATLA-positive 13 days after arrival in Japan, suggesting that they had been infected with ATLV in Indonesia where they were captured. Thus, ATLV appears to be prevalent among several macaque species as well as in man, and its pathogenetic role in these non-human primates should be explored in relation to ATL in man.

A rabbit lymphoid cell line (Ra-1) was established by co-cultivation with a human T-cell line (MT-2) carrying human T-cell leukemia virus (HTLV). The Ra-1 cell line is chromosomally male and is persistently infected with HTLV. Ra-1 cells, with or without mitomycin C treatment, were inoculated intravenously (i.v.) into 3 female rabbits. All 3 animals responded with the production of antibodies to HTLV antigens. Lymphocytes from one of these seroconverters were cultured in the presence of T-cell growth factor (TCGF) and HTLV particles were detected in the TCGF-grown lymphocytes which were chromosomally female. Co-cultivation of lymphocytes from the 2 other seroconverters with lymphocytes from 2 anti-HTLV-negative healthy men gave rise to the establishment of an HTLV-producing T-cell line derived from each individual. Blood transfusion from one of the HTLV-infected rabbits into 2 female rabbits also resulted in the seroconversion of both recipients. An HTLV-carrying lymphoid cell line (Ra-2) was established from one of the transfusion-related seroconverters. The Ra-2 cell line was initially TCGF-dependent but later became TCGF-independent. There results indicate that HTLV can be transmitted to rabbits. These animals may provide a suitable model system for studying the mode of transmission and pathogenicity of HTLV.