Protection, liver function and humoral immune response in sheep vaccinated with mimotopes of cathepsin L1 and L2 experimentally infected with Fasciola hepatica

Abstract

Protection, liver function and humoral immune response were assessed in sheep vaccinated with mimotopes of cathepsin L1 and/or L2 and challenged with Fasciola hepatica metacercariae. Twenty sheep were randomly allocated in four groups of five animals each, for immunization with 1 x 10¹⁴ phage particles of cathepsin L1 (YVYRWVEAECVA), cathepsin L2 (YVYEGRSRVRRP), cathepsin L1/L2 (YVYRWVEAECVA and YVYEGRSRVRRP) and phosphate buffered saline (PBS, control group), without adjuvant at weeks 0 and 2. All groups were challenged with 300 metacercariae at week 6 and slaughtered at week 22. Sheep vaccinated with cathepsin L1 mimotopes had a reduction in fluke burden of 50.11% when compared to control group, whereas animals vaccinated with cathepsin L2 and L1/L2 the reduction was 35.82% and 13.85% respectively. This difference was not significant. Animals receiving cathepsin L2 and L1/L2 showed a significant reduction in eggs output. The sheep vaccinated with phage clones produced significantly higher titres of IgG antibodies than the sheep in the control group. No significant differences in serum glucose, levels of GLDH and GGT were observed between the control group and the vaccinated sheep.