Evaluation of The Protective Immunity of 28KD-GST as a Vaccine Against Experimental Schistosoma mansoni

AbstractThe present work is concerned with the evaluation of Sm28GST as a vaccine against infection with S. mansoni using Sm28GST for immunizing BALB/c mice before challenge. Schistosoma mansoni GST was purified from adult worm homogenates by affinity chromatography. SDS-PAGE analysis of the purified antigen revealed that SmGST has molecular weight around 28 kD.- Eleven groups of 10 mice in each were used in this study.1- Group[A]: Non immunized and infected only with S. mansoni as a control group.2- Group[B]: Non Immunized non infected.3- Group [C]: Immunized with 10 ml BCG only as a control group.4- Group[ D]:. Immunized with 10 ml CFA only as a control group.5- Group [E]: Immunized with 10mg GST only as a control group..6- Group [F]: Immunized with 25mg GST.7- Group [G]: Immunized with 35 mg GST.8- Group [H]: Immunized with 25 mg GST + 10 ml CFA.9- Group[I]: Immunized with 35 mg GST + 10 ml CFA.10- Group[J]: Immunized with 25 mg GST + 10 ml BCG.11- Group[K]: Immunized with 35 mg GST + 10 ml BCG.- The first five groups [A,B,C,D&E] were considered as control group- All groups were injected subcutaneously except [C, J & K] groupswhich were injected intradermally.- The same injections were given to animal groups 2 & 4 weeks later.- Each mouse was challenged with 100 S. mansoni cercariae by tail immersion 2 weeks after last dose.- Blood samples were taken 7 weeks post infection for detection of anti-GST antibodies (IgG1&IgE) , circulating antigens. After that each mouse was sacrificed for determination of worm burden and histopthological changes.The parameters used for the assessment were the effect of vaccination on antibodies level (IgG1,IgE) ,circulating antigen ,worm load and histopthological changes in liver (granuloma number and size).The following results were obtained:1- All vaccinated groups except groups [F,C&D] showed statistically significant reduction in worm burden. The highest reduction was in group [I].2- With the exception of groups [C&D], there was significant reduction in the number of granuloma in all vaccinated groups. Also, there was significant reduction in the size of granuloma in all vaccinated groups except in group [F,C&D].3-All vaccinated groups except groups [F,C&D] showed statistically significant increase in the mean optical density of IgG1. The increase was prominent in group [I].4- All vaccinated groups except groups [F,C&D] showed statistically significant increase in the mean optical density of IgE. The increase was prominent in group [I].5- All vaccinated groups except groups [F,C&D] showed statistically significant reduction in S.mansoni circulating antigen. The highest reduction was in group [I].