Antibody-independent inhibition of Plasmodium falciparum in vitro cultures

Abstract

The sera of 100 Colombian individuals of African origin living in a malaria-endemic area of the Pacific coast were studied with regard to their capacity to inhibit Plasmodium falciparum cultures in vitro. Antimalarial antibody levels determined by indirect immunofluorescence were higher in the group of infected individuals than in the noninfected individuals, and inhibitory activity assessed by the inhibition of parasite incorporation of 3H-hypoxanthine in vitro was present in the sera of both the infected and noninfected patients. We believe that the noninfected patients were probably immune. The sera of some of the infected patients had high inhibitory capacities for the P. falciparum FCB-1 isolate. When the inhibitory effects of some of the sera were tested by using four parasite isolates from different regions of the world, striking differences among them were found.

Immune effector mechanisms in malaria

“…Because the goal of immunity to asexual stages is to stop the invasion of red cells and parasite growth, one might expect the ability of an individual's serum to inhibit these two processes in vitro to be a good marker of immunity to malaria. Both immune sera (55–59) and purified antibodies (60–63) have been reported to inhibit parasite growth in vitro , but this was not associated with immunity to clinical malaria (44,64,65). The observation that antibodies purified from otherwise strongly inhibitory sera may actually enhance parasite growth (58,59,66) suggests that growth inhibition in serum might, in part, be mediated by non‐antibody host factors or perhaps even residual anti‐malaria drug.…”