Abstract
BackgroundThe 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.MethodsForty-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).ResultsThere 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.ConclusionsExperimental 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.
Highlights
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
Sheep were randomly divided into three groups: Group 1 consisted of 5 animals which were neither immunised nor experimentally challenged (n = 5), remained as negative control group, Group 2 consisted of 20 animals (n = 20) which were experimentally infected with F. hepatica and Group 3 consisted of 20 sheep which were immunised with Recombinant F. hepatica cathepsin L1 (rFhCL1) and experimentally challenged with F. hepatica (n = 20)
This study focuses on the production of free radicals by leukocyte populations in peritoneal fluid during the early stages of fasciolosis, being the first in vivo study carried out in sheep infected and uninfected with F. hepatica
Summary
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. The majority of the vaccination studies have been focussed on the late stage of the infection when the immune response of the host is known to be already immunomodulated by the parasite towards a nonprotective Th2 response and the inhibition of protective pro-inflammatory products [8, 9]. Studies in infected and vaccinated animals during the early stage of infection, when the parasite is migrating and establishing in the liver may shed light on the initial immunological pathways of the disease
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