Prevention of peroral and congenital acquisition of Toxoplasma gondii by antibody and activated macrophages.

Intramuscular administration of Toxoplasma gondii lysate antigens to mice produced titers of T. gondii-specific antibody (measured by Sabin-Feldman dye test) greater than or equal to 1:1,024 in their sera. Intravenous administration of heat-killed Propionibacterium acnes to mice produced peritoneal macrophages with enhanced microbicidal capacity against T. gondii. Mice with high antibody titers or activated peritoneal macrophages or both had reduced numbers of Toxoplasma cysts in their brains 30 days after peroral challenge. Specific antibody and activated macrophages appeared to act together to significantly (P = 0.01) reduce the numbers of Toxoplasma cysts. A reduction in tissue infection as a result of these treatments was also demonstrated by subinoculation of brain tissue. A high antibody titer alone did not protect against congenital infection. Mice treated with P. acnes delivered reduced numbers of T. gondii-infected pups (P greater than 0.05). Treatment that produced high titers of Toxoplasma antibody and activated macrophages provided significant protection against congenital infection (P less than 0.05).