Attempts to Immunize Monkeys Against Plasmodium knowlesi by using Heat-Stable, Serum-Soluble Antigens

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  • Vector Biology and Control Division, Bureau of Tropical Diseases, Center for Disease Control, Public Health Service, U. S. Department of Health, Education, and Welfare, Atlanta, Georgia 30333

Thirty-six Macaca mulatta monkeys were immunized with different concentrations and regimens of heat-stable, serum-soluble (S-) antigens of Plasmodium knowlesi prior to challenge with the homologous parasite via sporozoite inoculation. Fewer deaths and reduced maximum parasitemias occurred in those animals inoculated with 10 to 40 mg of S-antigen compared to nonimmunized monkeys or those receiving only Freund's adjuvant. Protection was incomplete, however, suggesting that antibodies to S-antigens may have a limited role in protection of hosts to malarial infection.