The combined recombinant cathepsin L1H and cathepsin B3 vaccine against Fasciola gigantica infection.

Protections against Fasciola gigantica infection in mice immunized with the individual and combined cathepsin L1H and cathepsin B3 vaccines were assessed. The vaccines comprised recombinant (r) pro-proteins of cathepsin L1H and B3 (rproFgCatL1H and rproFgCatB3) and combined proteins which were expressed in Pichia pastoris. The experimental trials were performed in ICR mice (n = 10 per group) by subcutaneous injection with 50 μg of the recombinant proteins combined with Alum or Freund's adjuvants. At two weeks after the third immunization, mice were infected with 15 F. gigantica metacercariae per mouse by oral route. The percents of protection of rproFgCatL1H, rproFgCatB3 and combined vaccines against F. gigantica were approximately 58.8 to 75.0% when compared with adjuvant-infected control. These protective effects were similar among groups receiving vaccines with Alum or Freund's adjuvants. By determining the levels of IgG1 and IgG2a in the immune sera, which are indicative of Th1 and Th2 immune responses, it was found that both Th1 and Th2 humoral immune responses were significantly increased in vaccinated groups compared with the control groups, with higher levels of IgG1 (Th2) than IgG2a (Th1). Mice in vaccinated groups showed reduction in liver pathological lesions when compared with control groups. This study indicates that the combined rproFgCatB3 and rproFgCatL1H vaccine had a high protective potential than a single a vaccine, with Alum and Freund's adjuvants showing similar level of protection. These results can serve as guidelines for the testing of this F. gigantica vaccine in larger economic animals.