Antigens and antibodies involved in humoral immunity to plasmodium falciparum

• Malaria plasmodiidae cause more death and disease than any other known human pathogen. The parasite still threatens half of the world population {2.5 billion) and 300 million people are considered to become infected every year. More than 1 million African children annually die from malaria and there are an estimated 80 million clinical cases/year in the world. How protection or immunity to the parasites is mounted in humans is still partially unknown, although both cellular and antibody mediated immunity has been implied. This thesis describes several aspects of the humoral immune response to Plasmodium falciparurn in humans. Sera from individuals with different degrees of exposure to the parasite or with clinical immunity were used to study antibodies to P. falciparum antigens by means of ELISA, indirect immunofluorescence, immunoprecipiation and immunoblotting. Antibodies of IgM and all four IgG isotypes were detected both in sera from immune donors and in those with their first infection. However, whereas high titered sera contained antibodies of IgM and IgG1-4 isotypes, IgG2 and IgG4 antibodies were frequently missing in low titered sera. This could indicate that the isotype expression, on the average, follows the downstreams order of the Igh-C genes and is correlated with the intensity of immunization as occurring in infection. Using the same methods for a detailed investigation of sera from children and adults living in a holoendemic area of Liberia, no (or weak) correlations between age-dependent acquisition of P.falciparum immunity and overall antibody activities or isotype expression were seen.

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