Vaccination with cathepsin L mimotopes of Fasciola hepatica in goats reduces worm burden, morphometric measurements, and reproductive structures.

Fasciolosis is a worldwide emergent zoonotic disease that significantly constrains the productivity of livestock. We conducted an experimental trial with four groups of five goats each, vaccinated with 1 × 1013 phage particles of cathepsin L1 (CLI: DPWWLKQ), CL1 (SGTFLFS), and CL2 (PPIRNGK) mimotopes combined with Quil A adjuvant. Animals received a booster four weeks later. The control group received phosphate-buffered saline. All animals were infected with 200 Fasciola hepatica metacercariae at week six and euthanised 16 weeks later. The percentage of significant worm reduction in CL1 (DPWWLKQ), CL1 (SGTFLFS), and CL2 (PPIRNGK) compared to the control group were 55.40%, 70.42% (P < 0.05), and 32.39%, respectively. Vaccinated animals showed a significant reduction in faecal egg production and egg viability. A significant reduction in the total biomass of parasites recovered was observed in the CL1 (DPWWLKQ) and CL1 (SGTFLFS) groups. In goats vaccinated with CL2 (PPIRNGK), fluke length and width were smaller than those in the control group. Furthermore, animals receiving CL mimotopes showed a significant reduction in the total area of reproductive structures. Goats immunised with phage-displayed mimotopes produced significantly high titres of specific IgG1 and IgG2 isotypes, indicating a mixed Th1/Th2 response. The liver fluke burdens in goats vaccinated with CL1 (DPWWLKQ) and CL1 (SGTFLFS) were significantly correlated with IgG and IgG1 levels.

Cathepsin L1 mimotopes with adjuvant Quil A induces a Th1/Th2 immune response and confers significant protection against Fasciola hepatica infection in goats.

Thirty goats were randomly allocated in five groups of six animals each, for immunization with 1 × 10(14) phage particles of clones 11, 13, and 13 with Quil A adjuvant and wild-type M13KE phage at the beginning and 4 weeks later. The control group received phosphate-buffered saline. All groups were challenged with 200 metacercariae at week 6 and slaughtered 14 weeks later. The mean worm burdens after challenge were reduced by 46.91% and 79.53% in goats vaccinated with clones 13 and 13 with Quil A (P < 0.05), respectively; no effect was observed in animals immunized with clone 11 and M13KE phage. Animals receiving clones 11, 13, and 13 with Quil A showed a significant reduction in eggs output. Vaccinated animals produced parasite-specific total IgG antibody which were boosted after challenge with metacercariae of F. hepatica. Furthermore, levels of anti-phage total IgG increased rapidly within 2 weeks of the first vaccination and were always significantly higher in all vaccinated goats than in the infected control group. The fluke burden of goats immunized with clones 13 and 13 with Quil A was significantly correlated with IgG2 and total IgG. Goats vaccinated with phage clones produced significantly high titres of IgG1 and IgG2 antibodies indicating a mixed Th1/Th2 response. These data indicate that cathepsin L1 mimotopes has a potential as a vaccine candidate against Fasciola hepatica, whose efficacy will be evaluated in other host species, including those of veterinary importance.