Immune response in Santa Inês sheep during Fasciola hepatica infection

Abstract

In the present study, we describe the proliferative response and the IFN-γ, IL-10, IL-4 cytokine expression profiles in peripheral blood, and IgG production, after the experimental infection of Santa Inês sheep with 250 Fasciola hepatica metacercariae that were evaluated at 60 and 210 days post-infection(dpi). The cytokine expression profile at 60 dpi was characterized by the production of IFN-γ and IL-10, which is indicative of an initial mixed Th1/Th2 response. The modulation of the response occurred at 210 dpi with a predominance of IL-10 and IL-4 over IFN-γ. Mononuclear cells from peripheral blood stimulated with F. hepatica antigen exhibited proliferative capacity at 60 dpi, whereas the response was consistent with modulation from Th1 to Th2 in the chronic phase. The IgG antibody response was more marked at 60 days than at 210 dpi, confirming the mixed-response profile. The late modulation of the T lymphocyte response in association with the predominance of IL-10 and IL-4 at 210 dpi suggests the involvement of these cytokines after the establishment of the parasites in the bile ducts. The transition from a mixed to a regulatory response in the chronic phase was also accompanied by a reduced number of eggs per gram of feces.