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Background: The majority of vaccination studies against infection with F. hepatica in a natural host have been conducted at the late stage of the infection when the host's immune response is already immunomodulated by the parasite towards a Th2 non-protective response. This study was aimed at analysing the dynamic of the cell populations present in peritoneal liquid and the production of free radicals by the peritoneal leukocytes in infected and vaccinated sheep with recombinant cathepsin L1 of F. hepatica (rFhCL1) in early stages of the infection. Methods: Forty-five sheep were divided into three groups: Group 1 remained as negative control (n = 5), Group 2 (n = 20) was challenged with F. hepatica and Group 3 (n = 20) was vaccinated with rFhCL1 and challenged with F. hepatica. After the slaughtering, peritoneal lavages were carried out at 1, 3, 9 and 18 days post-infection (dpi) to isolate peritoneal cell populations. Flow cytometry was conducted to assess levels of hydrogen peroxide (H2O2) and nitric oxide (NO). Results: There was a significant increase in the total number of leukocytes at 9 and 18 dpi in infected and vaccinated groups. Production of H2O2 was significantly increased in peritoneal granulocytes in both infected and vaccinated groups. Production of nitric oxide showed a significant rise in the granulocytes and monocytes/macrophages in infected and vaccinated sheep. The NO production by granulocytes at 3 and 9 dpi was significantly higher in the vaccinated than in the infected animals. Conclusions: Experimental infection induced an increase in the total number of leukocytes within the abdominal cavity at 9 and 18 dpi, being more noticeable in vaccinated animals. Production of H2O2 occurred mainly in granulocytes of vaccinated and infected animals. Production of NO was incremented in vaccinated and non-vaccinated animals in all peritoneal cells. Vaccinated animals produced significant higher level of H2O2 and NO than infected animals. [ABSTRACT FROM AUTHOR]

Fluke burdens, faecal egg output and hepatic damage were assessed in goats immunised with recombinant cathepsin L1 (rCL1) plus Quil A (n = 7) or Quil A alone (control: n = 7) and challenged with Fasciola hepatica. There were no significant differences in fluke burdens (56 ± 26 vs. 92 ± 53), average fluke length (20.9 ± 3.0 vs. 21.0 ± 3.4 mm) or faecal egg output (525 ± 533 vs. 758 ± 677.8 eggs per gram at 17 weeks post-infection) between vaccinated and infected control groups, respectively, but high individual variability was evident. Morphometric and histopathological studies showed reduced hepatic damage in the vaccinated group compared to the infected control, but high individual variability was also recorded. Further vaccine trials in goats should be carried out using a larger number of animals to evaluate rCL1 as a vaccine for fasciolosis in goats. [ABSTRACT FROM AUTHOR]