PLASMODIUM-BERGHEI - SUPPRESSION OF ANTIBODY-RESPONSE TO SPOROZOITE STAGE BY ACUTE BLOOD STAGE INFECTION

Abstract

Mice infected with the erythrocytic stages of P. berghei show impaired host response to immunization with irradiated sporozoites of the same malarial parasite. The stage-specific anti-sporozoite response was measured by indirect immunofluorescence upon adsorption of the sera with parasitized red blood cells. P. berghei-infected mice immunized with irradiated sporozoites on the 4th day of a blood-induced malaria infection developed normal anti-sporozoite antibody [Ab] response. This Ab response was short-lived compared with the Ab response in normal mice immunized with a similar dose of irradiated sporozoites. The immune response was severely depressed when the animals were immunized on day 7 or later after malaria infection. No sporozoite-immunized animals, including those which responded to the 1st immunization, developed a secondary Ab response on reinoculation with irradiated sporozoites. A fully established anti-sporozoite immune response, obtained after multiple immunizations with irradiated sporozoites and which resulted in stage-specific protection of the animals, was not affected by a superimposed blood stage malaria infection. Titers of the anti-sporozoite Ab in these animals were unaltered in spite of high parasitemias. Malaria parasitemia reduction by chloroquine treatment abolished immunosuppressive effects of the disease. Anti-sporozite immunity and immunosuppression in man in malaria endemic areas are discussed.