Changes in the humoral immune responses after chemotherapy in single and co-infected individuals with Schisosoma haematobium and Plasmodium falciparum.

ABSTRACT

OBJECTIVE: To determine the effects of chemotherapy on the humoral immune responses in single and coinfected individuals with Schistosoma haematobium and Plasmodium falciparum. DESIGN: Prospective assessment of the humoral immune responses after treatment with praziquantel for schistosomiasis and chloroquine for malaria. SETTING: The study was carried out in four rural schools in Goromonzi and Mtoko districts 50km and 143km away from Harare respectively where both schistosomiasis and malaria are endemic. SUBJECTS: 555 school children aged 8 to 19 years; 298 from Goromonzi and 257 from Mtoko. MAIN OUTCOME MEASURES: Standard ELISA assays were carried out on the sera for immmunoglobin A (IgA), immmunoglobin E (IgE), immmunoglobin M (IgM) and immmunoglobin G (IgG) against the Schistosoma haematobium soluble worm antigen (SWA), soluble egg antigen (SEA), cercaria antigen (CERCA) and the Plasmodium falciparum malaria antigen (MALA). Eosinophil count was also done on Giemsa stained smears. RESULTS: Treatment resulted in a decrease of sera IgA levels against SEA in those individuals that had schistosomiasis only and there was a significant increase of sera IgE against the cercaria antigen (p < 0.05). Those that had malaria whether singly or coinfected sera IgE against MALA decreased but sera IgE against SEA increased. Sera IgE against SEA increased significantly (p < 0.05) in those that had neither infections who had been given praziquantel treatment. Eosinophilia was evident in parasitic infections. CONCLUSION: Schistosomiasis is a problem in rural settings as in all the four schools > 50% of the pupils were infected, whilst those that were < 15 years of age had high egg intensities. There was a rise in sera IgE antibodies against SEA and CERCA in all the cases that were treated with praziquantel, an indication that treatment does alter the immune response favouring resistance to infection by Schistosoma haematobium. Those that had malaria singly or coinfected produced high levels of sera IgE against SEA an indication that malaria infection influences the cytokine environment to favour production of IgE isotypes against the schistosome egg antigen.