Wild isolates of Plasmodium falciparum malaria show decreased sensitivity to in vitro inhibition of parasite growth mediated by autologous host antibodies.

Abstract

Antigenic diversity in field populations of Plasmodium falciparum parasites may delay the acquisition of protective immunity to malaria, the development of which may thus require repeated exposure to infection over a prolonged period of time. In this study we show that P. falciparum parasites may vary in their sensitivity to antibody-mediated invasion/growth inhibition in vitro. Wild isolates of P. falciparum from children living in an endemic area of Burkina Faso were tested for their sensitivity to the growth inhibitory effects of antibodies originating from the same (autologous) and from other donors (heterologous). A significantly lower invasion inhibition activity was obtained when the isolates and antibodies were tested in autologous compared with heterologous combinations. The lower sensitivity to growth inhibition by autologous antibodies may be due to immune pressure in vivo, selecting from a heterogeneous parasite population those with a low expression of the antigens recognized by the host's antibodies. Alternatively, the parasites cultured from each child might represent expanding parasite populations, mainly constituting strains not earlier seen by the immune system of that specific host. The results reinforce the concern about Plasmodium antigenic diversity as a major obstacle towards the development of an effective malaria vaccine.