Acute malaria prolongs susceptibility of mice to Plasmodium berghei sporozoite infection.

The fate of immune response against sporozoite stage in malaria infection was investigated. Two groups (A and B) of mice were inoculated twice with infective sporozoites of Plasmodium berghei. The mice in group A were maintained on chloroquine prophylaxis to prevent the sporozoite infection from causing malaria. Group B animals on the other hand were allowed to develop acute malaria from the infection which was subsequently cured with chloroquine. Upon examination for stage specific immune responses, it was found that the animals in group A produced high antibody titres against sporozoites and none against erythrocytic stages. The mice in group B produced little anti-sporozoite antibodies but had high antibody titres against blood forms. Challenge infection with P. berghei sporozoites showed that group A animals had become resistant against sporozoite-induced parasitaemia, whereas the mice in group B remained susceptible. The possible significance of suppression of protective immunity by malaria in host-parasite relationship is discussed.