Testosterone impairs efficacy of protective vaccination against P. chabaudi malaria.

Vaccination with surface membranes isolated from Plasmodium chabaudi-infected erythrocytes can protect B10.A mice from the lethal outcome of P. chabaudi malaria. However, the efficacy depends on gender and testosterone levels. Thus, vaccination protects over 90% of female mice, but only about 55% of male mice and only about 34% of female mice when pretreated with testosterone for 4 weeks. The suppressive testosterone effect remains imprinted in females even at 10 weeks after the testosterone treatment. These data indicate that not only genetic but also environmental factors restrict the host's immune response to a malaria vaccine.