Identification of Fasciola hepatica gut-associated glycoproteins as potential vaccine candidates by lectin-affinity chromatography, flukicidal monoclonal antibodies, and affinity-enrichment mass spectrometry.

A significant economic impact to the agriculture and declining drug efficacy due to anthelmintic resistance lead to the search for novel intervention approaches against the zoonotic liver fluke Fasciola hepatica. A cost-effective strategy is to induce protective immunity by vaccination. However, adaptation of the parasite to evade the host immune response hampers classical vaccine development. Therefore, an ideal protective epitope would not be subjected to this evolutionary selection. Antigens, which are not exposed to the host's immune system during a natural parasite infection, but which could be attacked by vaccine antibodies, have been shown to be valid candidates, especially those expressed in the gut of blood-feeding and tissue-dwelling helminths. Overall, helminth gut-associated glycoproteins-including hidden antigens-serve as a rich source for novel anthelminthic vaccine candidates. Here, we purified F. hepatica gut-associated glycoproteins assisted by lectin-affinity chromatography and specific monoclonal antibodies (mAbs). The protective capacity was demonstrated in vitro by feeding the mAbs to cultured F. hepatica, which impaired fluke survival assessed by reduced motility, fecundity, and reduced active secretion. Furthermore, we could demonstrate a binding of different mAbs to F. hepatica gut structures, indicating that liver flukes dine from their environment. Characterisation of the complex gut-associated glycoproteins by a quantitative affinity-enrichment proteomics approach revealed a list of 36 proteins with potential for further vaccine development. Given a conservation of many of these candidates in different F. hepatica life stages indicated by available transcriptomic data, such parasite gut-associated glycoproteins serve as a rich source for novel vaccines, directed also against early developmental stages responsible for pathological liver damage.