DNA vaccination using schistosoma mansoni fimbrin gene on naive and infected praziquantel-treated mice

ABSTRACT

DNA immunization represents a promising vaccine strategy that has been reasonably successful, and will likely play a greater role in vaccine research development against Schistosoma mansoni [S. mansoni]. S. mansoni fimbrin [Smfim] gene which encodes a putative actin bundling tegumental and immunogenic protein has been cloned into the eukaiyotic expression vector pcDNAI/Amp and used for intra-muscular DNA vaccination of Swiss albino mice. Two experimental models were used to study its role on protection against S. mansoni infection in naive mice [model 1] and to explore its effect on infected praziquantel [PZQ]-treated mice [model 2] using different immunological, parasitological and histopathological parameters. In the first model, Smfim-vaccinated mice showed high anti-Smfim IgG titer and acquired a significant protection [43.2%; p< 0.01] with reduction of ova count in both hepatic and intestinal tissues [59.2% and 5 1.1% respectively, p< 0.01], significant reduction of granuloma count [24.1%; p< 0.01] and granuloma diameter [18.3%control group. This indicates a good impact on the pathology of the disease. In the second model, PZQ-treated mice had higher anti-Smfim IgG titer [p< 0.05] compared to infected untreated control animals which may be due to unmasking of the tegumental antigen. Although, infected Smfim-vaccinated mice had higher collagen content [27.93 +/- 1.75] and prominent involution granulomas [74%] compared to PZQ-treated animals. PZQ-treated Smfim-vaccinated group had striking histological criteria. The percent of parenchymal granulomas has been significantly decreased [p< 0.001] with no fibrous granulomas and the collagen content reduced significantly. In conclusion, Smfim DNA vaccination has a protective and an anti-pathological effect in naive mice. The improved pathological status in vaccinated praziquantel-treated animals compared to infected vaccinated group, proposed an immunological and pathological modulating effect of PZQ treatment