Protection of mice against Babesia spp. and Plasmodium spp. with killed Corynebacterium parvum.

Mice which had been pre-treated with killed Corynebacterium parvum given intravenously or intraperitoneally, but not subcutaneously, were completely resistant to infection with Babesia microti or B. rodhaini, and were protected from death caused by Plasmodium vinckei or P. chabaudi infection. There is evidence that the parasites died within circulating erythrocytes. This occurred much too soon for a specific antibody response to be evoked, and no antibody could be detected by the indirect fluorescent-antibody technique. Thus it is suggested that a non-specific soluble mediator may play an important role in the protection observed.