Effect of HTLV-III on the macromolecular synthesis in HTLV-I carrying cell line, MT-4

Upon infection of human T-cell leukemia virus type I (HTLV-I)-carrying human T-cell lines such as MT-4, HTLV-III, a probable etiologic agent of acquired immune deficiency syndrome (AIDS) caused fast and strong cytopathic effects leading ultimately to the death of the cells. Such effects were preceded by the rapid induction of HTLV-III antigens. Cell lines not infected with HTLV-I could, however, be subcultured after infection with HTLV-III, although they were also positive for HTLV-III antigens. To understand this cytopathogenicity of HTLV-III in HTLV-I bearing cells, macromolecular synthesis, including DNA synthesis and total protein synthesis, and also IL-2 receptor expression were investigated kinetically. In infected MT-4 cells DNA synthesis was markedly inhibited by HTLV-III after the HTLV-III antigen synthesis became evident. This inhibition occurred before cell damage was detected in terms of viable cell-growth, but after induction of HTLV-III antigen. Puromycin, at 40 micrograms/ml, caused no toxic changes in MT-4 cells over 3 days but prevented viral antigen synthesis and virus-induced cytopathic effect. Protein synthesis and IL-2 receptor expression were also inhibited at 4 and 5 days post infection. The degree of the effects and their kinetics suggest that they are the secondary effects of cytotoxicity by HTLV-III infection.