IMMUNE RESPONSES TO HELMINTH PARASITE ANTIGENS IN MALARIA ENDEMIC POPULATIONS

Co-infection with P. falciparum and helminths in Sub-Saharan Africa could modulate the immune response towards the parasites as well as the individual susceptibility to clinical forms. Our aim is to investigate the impact of helminth infections on immune responses and susceptibility to malaria in different ethnic groups from Burkina Faso (Modiano et al. PNAS 1996). The objectives of this work are: i) to measure immunoglobulins against helminth parasite antigens in plasma samples (N=288) collected among Mossi, Fulani and Rimaibe rural communities; ii) to assess differences in relation to age, sex, village, ethnic group, infection with P. falciparum; iii) to assess correlation with antibodies against malaria antigens (CSP, MSP1, MSP2, AMA1) and total IgE. Measurements of IgG against Strongyloides, Taenia spp. and filarial infections are ongoing. A custom ELISA protocol was used to measure IgG against Schistosoma haematobium Soluble Egg Antigen (SEA). The prevalence of anti-SEA IgG is 63%, in line with the prevalence of S. haematobium infection reported for the same area of Burkina Faso (55-85%, Traore et al. Medecine d'Afrique Noire 1990). The prevalence is zero in infants, increases during childhood to reach its peak in teens, and decreases from 20 years onwards. Females show a lower prevalence than males (P=0.003). Differences in prevalence are not observed among villages or ethnic groups, but the Fulani show lower levels of anti-SEA IgG (P=0.0001) suggesting that lighter S. haematobium infections occur in the ethnic group known for a marked lower susceptibility to P. falciparum. Individuals infected with P. falciparum show higher levels of anti-SEA IgG (P=0.0002). A positive correlation exist between anti-SEA IgG, total IgE (P<0.0001) and anti-CSP IgG (P=0.009). These results suggest that common host factors may affect susceptibility to P. falciparum and S. haematobium (e.g. age, ethnicity) and warrant further investigation into the immunological cross-talk between the two parasites.