title: Liver fluke vaccines in ruminants: strategies, progress and future opportunities.
abstract: The development of a vaccine for Fasciola spp. in livestock is a challenge and would be advanced by harnessing our knowledge of acquired immune mechanisms expressed by resistant livestock against fluke infection. Antibody-dependent cell-mediated cytotoxicity directed to the surface tegument of juvenile/immature flukes is a host immune effector mechanism, suggesting that antigens on the surface of young flukes may represent prime candidates for a fluke vaccine. A Type 1 immune response shortly after fluke infection is associated with resistance to infection in resistant sheep, indicating that vaccine formulations should attempt to induce Type 1 responses to enhance vaccine efficacy. In cattle or sheep, an optimal fluke vaccine would need to reduce mean fluke burdens in a herd below the threshold of 30-54 flukes to ensure sustainable production benefits. Fluke infection intensity data suggest that vaccine efficacy of approximately 80% is required to reduce fluke burdens below this threshold in most countries. With the increased global prevalence of triclabendazole-resistant Fasciolahepatica, it may be commercially feasible in the short term to introduce a fluke vaccine of reasonable efficacy that will provide economic benefits for producers in regions where chemical control of new drug-resistant fluke infections is not viable. Commercial partnerships will be needed to fast-track new candidate vaccines using acceptable adjuvants in relevant production animals, obviating the need to evaluate vaccine antigens in rodent models.
authors.affiliation: Department of Agricultural Sciences and Centre for AgriBioscience, La Trobe University, Bundoora, Victoria 3083, Australia.
authors.forename: Hayley
authors.initials: H
authors.lastname: Toet
authors.affiliation: School of Applied Sciences and Engineering, Federation University, Churchill, Victoria 3842, Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Piedrafita
authors.affiliation: Department of Agricultural Sciences and Centre for AgriBioscience, La Trobe University, Bundoora, Victoria 3083, Australia. Electronic address: t.spithill@latrobe.edu.au.
authors.forename: Terry W
authors.initials: TW
authors.lastname: Spithill
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity; D000947:Antigens, Helminth / Q000276:immunology; D000954:Antigens, Surface / Q000276:immunology; D000980:Antiplatyhelmintic Agents / Q000627:therapeutic use; D001562:Benzimidazoles / Q000627:therapeutic use; D002417:Cattle; D005210:Fasciola hepatica / Q000276:immunology*; D005211:Fascioliasis / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D012418:Ruminants / Q000276:immunology* / Q000469:parasitology*; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology / Q000517:prevention & control; D034561:Sheep, Domestic / Q000276:immunology / Q000469:parasitology; D000077682:Triclabendazole; D014612:Vaccines / Q000138:chemical synthesis*
chemical_list: D000947:Antigens, Helminth; D000954:Antigens, Surface; D000980:Antiplatyhelmintic Agents; D001562:Benzimidazoles; D014612:Vaccines; D000077682:Triclabendazole
keywords: Acquired immunity; Fasciola gigantica; Fasciola hepatica; Liver fluke; Tegument proteins; Vaccine