ABSTRACT
Liver fluke infection of cattle and sheep has important implications for animal health and welfare, farming economics, and food production in most of the world, it is considered to be among the main causes of reduced livestock productivity. The aim of the work is to study the level of protection and the immune response in experimentally infected goats vaccinated with native glutathione S-transferase [GST] of Fasciola gigantica. Fifteen male goats [6-12 months age] free from F gigantica infection were divided into 5 groups: G1 was vaccinated by native glutathione-S-transferase [GST]; G2 was vaccinated by unbound fraction proteins [UBF]; G3 [control group] was vaccinated by Friend's adjuvant; G4 and G5 were kept as control positive and control negative, respectively. Goals in G1-G3 were orally infected by 120 metacercaria of F gigantica, 15 d after vaccination. Animals in G4 received the same infecting dose. Serum samples were collected to assess the antibody levels by ELISA. Feces were examined from all goats hr 15 successive weeks post challenge. Several parameters such as fluke burden, egg output and humoral response were measured for evaluating vaccine efficacy against a challenge infection with Fasciola. F giganhica GST isolated by affinity chromatography revealed one band of 25.3 kDa using SDS-PAGE. Specific antibody levels were significantly detected in experimentally infected and vaccinated goats 2nd and 3rd week post vaccination [P1] and post challenge, reached maximum at 7th and 9th weeks, and remained constant till end of experiment. In animals of G1 and G2, versus control G3 and G4, F gigantica vaccine induced reduction of ova per gram [OPG] by 59.6% and 32.4%, respectively, and reduction of worm burden by 52.69%, and 36. 15%, respectively. The same results were obtained for G3 and G4 indicating that Freund's adjuvant had no role in immunity defense mechanism. Vaccination with F gigantica GST antigen showed higher reduction in OPG count, worm burden and flukes' size than vaccination with UBF antigen in comparison with control groups