Using the indirect fluorescent antibody method, the production and persistence of specific antibody was demonstrated in patients inoculated with blood parasites of Plasmodium falciparum.
With P. falciparum (Thailand strain), antibody developed in response to the presence of patent parasitemias and the titers fluctuated significantly during the primary attack, apparently in a delayed direct association with fluctuation in parasite densities induced by non-curative dosages of antimalarial drugs. The rapid antibody response and long antibody persistence in the one patient with P. falciparum (Colombia strain) indicated either a possible previous exposure to malaria or a response peculiar to the strain of P. falciparum concerned.
Antibodies to the Colombia strain were shown to persist for up to 20 months after sporozoite inoculation with little or no decrease in antibody titer between 12 and 20 months.
Address: Assistant Chief, Laboratory of Parasite Chemotherapy, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland.