A longitudinal follow up of natural immune responses to plasmodium falciparum infection in children living in endemic area of western Kenya
The mechanisms of naturally acquired immunity to malaria are not clearly understood. In order to understand the development of natural immune responses to malaria, I carried out a longitudinal follow up of young children less than 2 years of age in an area of western Kenya, which is holoendemic for malaria. In this study, parasitaemia, body temperature, haemoglobin levels and cellular immune response to plasmodium falciparum exo-antigens and a recombinant antigen representing the 19 KD C-terminal domain of the merozoite surface protein (MSP-1 19 kDa antigen) of 49 infants were followed at monthly intervals. The proliferative responses were measured by thymidine incorporation assay of peripheral blood mononuclear cells (PBMCs) isolated from finger prick blood. This response was measured longitudinally at 3-6 time points response was measured longitudinally analysis of proliferative responses to MSP-1 19kDa antigen indicated that most of the children 36/49 (73.47percent) responded at least once with a stimulation index value more than 2. Although many of these children had detectable levels parasitaemia at several time points, they showed positive proliferative responses only a few times during the entire testing period. This finding suggests that cellular immune responses to MSP-1 19 kDa and exo-antigens are not long lasting. No correlation was observed between response to MSP-1 19 kDa/exo-antigens and the preveiling infection status. Levels of IL-4 (a TH2 cytokine) and IFN- (a TH1 cytokine) were measured in plasma samples and in culture supernatants collected from a subset of the study group. PBMCs from 79 infants were stimulated with MSP-1 19kDa antigen and exo antigens and the resulting supernatant tested for IL-4 and IFN-. The results of this study show that a larger number of infants responded to MSP-1 19 kDa/exo-antigens by production of IL-4 than IFN-. Analysis of plasma samples also showed more individuals with detectable IL-4 than IFN-. There was however no correlation betweein either in vitro cytokine production or cytokine prevalence in plasma and the prevailing infection status.
- MST-Zoological Sciences