The Role of Schistosoma Mansoni Eggs in Protection against Plasmodium Berghei Infected Mice

Abstract

The co-occurrence of malaria and schistosomiasis is common in tropical regions of the world. Malaria remains a global burden with no vaccine discovered yet. These necessitated the need to look at the immune responses that could be triggered in a coinfection setting. Malaria induces a strong Th1 response while schistosomiasis skews the response to a Th2. This study examined the role of Schistosoma mansoni eggs on malaria disease progression in BALB/c mice infected with Plasmodium berghei. The objectives were to determine the immune correlates to protection. Two groups of mice were used: the experimental and control groups. Experimental were injected with a triple dose of S. mansoni eggs at ten day interval before being challenged with P. berghei while controls were infected with P. berghei only. Five mice from both groups at each time point were euthanized and spleen and serum collected. Mice were euthanized at day 3, 6, 9 and 12 post-challenge with P. berghei. Parasitaemia was monitored daily using Giemsa stained blood smears. Results showed that experimental mice exhibited lower levels of P. berghei parasitaemia (15.52%) as compared to the controls (23.06%). IgG levels were high in the experimental mice compared to controls following stimulation by soluble egg antigen (SEA). Differences in IgG levels between the two study groups were not significant (p>0.05). Levels of IFN- ? and IL-4 were high in the experimental mice than the control group though the difference was not significant (p=0.213). S. mansoni eggs did not induce significant differences in cytokine and IgG levels; nevertheless they contributed to delaying death in the experimental mice by two days by enhancing levels of IgG and IL-4. These findings provide grounds for further studies in non-human primates to better understand the immunomodulatory role of schistosome eggs on malaria progression.

Keywords: Schistosoma mansoni, Plasmodium berghe, iSoluble egg Antigen