Therapeutic effects of bovine enterovirus infection on rabbits with experimentally induced adult T cell leukaemia

A bovine enterovirus, MZ-468, showed cytopathic effects on cell line F-647a, which was established by coculture of human T cell lymphotropic virus type 1-transformed MT-2 cells and X-irradiated rabbit lymphocytes. Microcalorimetric assay showed that residual, viable, MZ-468-infected F-647a cells produced less heat than non-infected cells. The therapeutic effects of MZ-468 infection were examined in rabbits in which adult T cell-like leukaemia (ATL) had been induced by' inoculation of F-647a cells (1 X 10(8) cells). Six newborn rabbits were separated into three groups: group A was inoculated with F-647a cells only; group B was treated with MZ-468 at the time of inoculation with cells; group C was treated with the same amount of virus 24 h after the inoculation with cells and then once every 4 days. Both of the animals in group A and one in group C died 10 and 11 days, and 22 days, respectively, after the inoculation with cells. Both rabbits in group B and one in group C survived for more than 4 months. The rabbits that died were examined pathologically; leukaemic infiltrations were found in the lungs of the group B rabbits, and in the lungs, spleens and livers of both group A rabbits. Two identical experiments produced almost the same findings. These results suggest that bovine enterovirus might be used clinically to prolong the life-span of ATL patients.