MODERN IMMUNOLOGICAL APPROACHES TO ASSESS MALARIA TRANSMISSION AND IMMUNITY AND TO DIAGNOSE PLASMODIAL INFECTION

The present paper reviews our recent data concerning the use of immuno logical methods employing monoclonal antibodies and synthetic peptides to study malaria transmission and immunity and to diagnose plasmodial infection. As concerns malaria transmission, we studied the main vect ors of human malaria and the plasmodial species transmitted in endemic areas of Rondonia state, Brazil. The natural infection of anopheline was evaluated by immunoradiometric assay (IRMA) using monoclonal antib odies to an immunodominant sporozoite surface antigen (CS protein) dem onstrated to be species specific. Our results showed that among six sp ecies of Anopheles found infected, An. darlingi was the main vector tr ansmitting Plasmodium falciparum and P. vivax malaria in the immediate vicinity of houses. In order to assess the level of anti-CS antibodie s we studied, by IRMA using the synthetic peptide corresponding to the repetitive epitope of the sporozoite CS protein, sera of individuals living in the same areas where the entomological survey has been perfo rmed. In this assay the prevalence of anti-CS antibodies was very low and did not reflect the malaria transmission rate in the studied areas . In relation to malaria diagnosis, a monoclonal antibody specific to an epitope of a 50 kDa exoantigen, the major component of supernatant collected at the time of schizont rupture, was used as a probe for the detection of P. falciparum antigens. This assay seemed to be more sen sitive than parasitological examination for malaria diagnosis since it was able to detect plasmodial antigens in both symptomatic and asympt omatic individuals with negative thick blood smear at different interv als after a last parasitologically confirmed attack of malaria.