The role of interleukin IL-4, IL-10 and interferon gamma cytokines on natural Fasciola hepatica infection was investigated by quantifying the mRNA levels in liver tissue from chronically infected cattle. IL-4 and IL-10 had higher expression relative to interferon gamma in the liver tissue of infected animals when compared with the control group. The higher levels of IL-10 and IL-4 observed in the present study suggest a synergism between these cytokines, as well as involvement in the suppression of TH1 cell responses and a consequent induction of decreased interferon gamma expression in chronic cattle fascioliasis. The cytokine ratios were positively correlated, indicating a predominance of IL-4 in the chronic phase of infection with respect to interferon gamma and IL-10. Interferon gamma was predominant expressed in the controls, suggesting the involvement of IL-10 in modulating the immune response in favor of IL-4 in infected animals. Our results suggest that the TH2 polarized host immune response previously observed in experimental infection may also be responsible for establishing chronic phase and the maintenance of the natural infection of cattle from endemic areas that are in continuous contact with parasite.

The development of Fasciola hepatica from two species of definitive hosts, i.e. cattle (Bos taurus) and a marmoset (Callithrix penicillata) in the snail Lymnaea columella was determined based on the production of rediae and cercariae and snail survival rate. More rediae and cercariae at 60-74 days post-infection were produced by snails infected by cattle-derived miracidia (cattle group) than by those infected by marmoset-derived miracidia (marmoset group). Among the L. columella parasitized by the marmoset group, the survival rate and the percentage of positive snails were higher than among those parasitized by the cattle group. Eggs of F. hepatica released in cattle faeces were significantly bigger than those released in marmoset faeces. Miracidia originating from parasites that completed their development in cattle were more efficient in infecting the intermediate host. These results suggest that vertebrate-host origin influences the eggs produced by the parasite and the infection rates in the snail host L. columella.

No 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.