Immunological Investigation of Malaria in Ghana

Abstract

A comprehensive immunological survey of malaria in rural and urban populations in Ghana is reported. Sera from Ghanaians resident in Ghana and Ghanaian students resident in the United Kingdom and Germany, pregnant women, blood donors and from patients with acute malaria, nephrotic syndrome, tropical splenomegaly, Burkitt's lymphoma, schistosomiasis, onchocerciasis and tuberculosis were included. Control sera were obtained from healthy adult Caucasians, Caucasians with connective tissue and parasitic diseases other than malaria, non-immune Caucasians with primary malaria infections and Nigerians. Serum from monkeys (Macaca mulatta) infected with P.knowlesi were also tested. Infecting parasites were identified by examination of blood slides. Malarial antibodies were detected by enzyme immunoassay (ELISA) and immunofluorescence (IFA). Antibodies to M.tuberculosis, V.cholerae, T.pallidum, E .histolytica, T.gondii, T.gambiense, T.rhodesiense, S.mansoni and T.canis were determined by a 'rapid' IFA test. Onchocercal antibodies were determined by ELISA using 0.gutturosa antigen. Antibodies to Epstein Barr Viral Capsid Antigen (VCA) and hepatitis B surface antigen (HBsAg) were measured by IFA and passive haemagglutination inhibition respectively. Serum levels of IgG, IgA, IgM, IgE, albumin, complement C3, C3 converted products, immune complexes and autoimmune antibodies were measured. All data were analysed by computer. The value of ELISA in the diagnosis and epidemiology of malarial infection was demonstrated in this study and the results showed good correlation with those obtained by immunofluorescence. Both tests were employed in the studies of malaria in rural and urban populations. The analysis of parasitological and serological indices obtained for the 2 populations confirmed the endemicity of malaria in Ghana: Plasmodium falciparum was the predominant species) prevalence rates were higher in the rural than the urban population) antibody levels in both populations showed an agerelated increase. The overall sero-epidemiological findings thus conformed to the classical concept of the acquisition of malarial immunity and suggested that a stable state of malaria prevails in Ghana. This survey revealed a high incidence of autoantibodies, raised levels of soluble immune complexes and evidence of in vivo complement activation in malaria. It has been suggested that in malaria, antigen-antibody complexes stimulate immune effector mechanisms. Products of these might interfere with the development of protective immunity and result in the initiation of immune complex diseases and its perpetuation. The findings reported would support this hypothesis.