Plasmodium berghei malaria: effect of acute phase serum on immunity generated in rats by infection and by vaccination.

Acute phase serum (APS) given at the time of challenge with Plasmodium berghei inhibited the generation to immunity to the infecting plasmodia. Administered with a single dose of vaccine, it inhibited induction of immunity by the vaccine. Three weekly doses, the last given two weeks before infection, induced immunity. Administration of vaccine simultaneously with infection neither aggravated nor ameliorated the infection. These results indicate that the effect of administration of APS on immunity generated by immunization or infection is dose- and time-dependent. The depression of immunity induced by this serum is thus temporary, the host finally overcoming the depression and responding to the plasmodial antigen in the serum. The interaction of vaccine and infection observed indicates that the introduction of vaccine is not detrimental to the individual incubating infection; rather, the vaccine is rendered useless, the reducing the aggregate benefit of the immunization to the group.