Mouse leukaemia, a dichotomy of virus neutralizing and cytotoxic antibodies

Abstract

Mice exposed to subliminal doses of live, or to large doses of properly inactivated mouse leukaemia viruses, or cells, will develop antibodies. These antibodies can be detected by virus neutralization (1, 2, 3, 4) and cytotoxic tests (5, 6, 7), among other techniques. I t is not known how these serologic faculties are correlated. Studies in progress suggest tha t the virusneutralizing and cytotoxic antibodies are not identical. The following is a preliminary report on these studies. An immune serum was obtained from mice with adoptive immunity. The cell donors were low leukaemia Timco (Texas Inbred Mouse Company, Houston) S~dss mice vaccinated with photodynamieally inactivated Rauseher mouse leukaemia virus. The technique of photodynamic inactivation of this virus has recently been reported (4, 8). A cell-free spleen extract of leukaemic mice is mixed with high dilution of methylene blue and the mixture is transill~minated with visible light for 25 minutes a t 37 ~ C. Due to photooxidation, the virus loses its infectivity. In the experiment described here, 3 doses of such inactivated virus were injected intraperitoneally into young adult mice a t 3-week intervals. The second dose of the vaccine was given together with Freund's complete adjuvant. These mice produced both virus neutralizing and cytotoxic antibodies. The pooled and inactivated (56 ~ C for 20 minutes) serum neutralized more than 102 LDs0 of the Rauscher virus (8). In the cytotoxic test, 15 per cent of Rauscher leukaemic spleen cells responded with swelling and pinkish