ANTIBODY-RESPONSES TO PLASMODIUM-FALCIPARUM SPOROZOITE-STAGE, LIVER-STAGE AND BLOOD-STAGE SYNTHETIC PEPTIDES IN MIGRANT AND AUTOCHTHONOUS POPULATIONS IN MALARIA ENDEMIC AREAS

This study evaluates the differences in host immune responses to defin ed plasmodial antigens in four geographically different regions in whi ch malaria is endemic. Sera from 527 individuals were tested for the p resence of antibodies specific for three types of plasmodial antigen: liver-stage antigen (LSA-1), blood-stage antigen (SPF 70) and circumsp orozoite (CS) antigen (NANP)4. The individuals taking part in the stud y comprised: patients with transfusional malaria due to Plasmodium fal ciparum or P. vivax; non-immune migrants residing in an endemic area i n Rondonia; Amazonian Indians from the states of Para (Xingu PA) and M ato Grosso (Xingu MT); people living in a hyperendemic area in Africa (Burkina-Faso); and controls that had never been to a malaria endemic area. None of the transfusional sera displayed antibodies against spor ozoite or to liver stage antigen, although 80% of the P. falciparum tr ansfusional malaria sera contained IgG antibodies against the blood-st age peptide. A low percentage of Indians from Xingu PA and of non-immu ne migrants displayed antibodies against liver-stage (27% and 17%) and sporozoite (11% and 12%) peptides, although a greater frequency of an tibodies against blood-stage peptide (50% and 49%) was observed in bot h cases. Indians from Xingu MT exhibited a greater frequency of antibo dies against liver, sporozoite and blood-stage peptides (45%, 50% and 58%). Only hyperimmune African individuals exhibited higher percentage s of antibodies against liver- (64%) and blood-stage antigens (87%), c ontrasting with a low frequency of antibodies against the CS repeat (3 3%). Taken together, the present data confirm that Rondonian migrants and Indians from Xingu PA constitute populations with limited exposure and immunity to P. falciparum malaria infection and conversely, Xingu MT Indians and Africans have been more exposed to malaria infection. In conclusion this study indicates that the immune response to these m alaria parasite peptides can be used to assess malaria transmission in epidemiological surveys.