Partial immunity to Fasciola hepatica in mice after vaccination with FhSAP2 delivered as recombinant protein or DNA construct.

INTRODUCTION We recently reported the biochemical characterization of a novel Fasciola hepatica recombinant antigen termed FhSAP2, which has previously shown to elicit protection to F. hepatica infection in rabbits. Further we reported that intramuscular (IM) injections of BALB/c mice with a pFLAG-CMV(-2) vector carrying cDNA encoding for FhSAP2 (cDNA-FhSAP2) induce high levels of immune response. The aim of the present study is to ascertain whether the immune response induced by this DNA construct may induce protection in mice against subsequent infection with F. hepatica metacercariae (mc). In addition, protection following subcutaneous (SC) injections with recombinant FhSAP2 was evaluated. METHODS Mice received three IM injections with 100 microg of cDNA-FhSAP2 or three SC injections with 20 microg of FhSAP2. Four weeks after the last vaccination mice were challenged orally with 5 F. hepatica me and euthanized 45 days after challenge. RESULTS Mean worm burdens found in mice vaccinated with cDNA-FhSAP2 was reduced by 83.3% and the mean worm burdens found in mice vaccinated with the recombinant protein was reduced by 60% when compared with controls. All vaccinated animals had less liver damage than challenge controls. Vaccination with cDNA-FhSAP2 seems to favor a mixed Th1/Th2-antibody dependent with higher predominance of Th1-regulated antibody response. CONCLUSIONS The vaccination with cDNA-FhSAP2 or recombinant FhSAP2 may protect hosts against F. hepatica infections. The vaccination with cDNA form of FhSAP2 appeared to be a little more efficient preventingthe infection. The predominance of Th1-dependent antibodies in the vaccinated animals may be responsible for the protection but this should be confirmed by Th1-cytokines determinations.