Fasciola hepatica: characterization of somatic and excretory-secretory antigens of adult flukes recognized by infected sheep.

The immune response of sheep to somatic components and excretory/secretory products of adult Fasciola hepatica, was studied during an experimental infection. Antibodies against adult fluke somatic and excretory/secretory antigens were detected by thin layer immunoassay from the second week post infection. Similarly, the results of Western blot analysis showed specific recognition of several components as early as two weeks after infection. However, an increase in the number and intensity of bands with time of infection was observed in the patterns of antigenic recognition. Most notorious was the strong reactivity of all infected sheep sera towards components of 20-23 kDa in the somatic preparation and components of 23-27 kDa in the excretory/secretory products of adult F. hepatica, specially noticeable after the sixth week post-infection. Since these polypeptides were recognized by all infected animals, they could play an important role in the diagnosis of sheep fascioliasis.