Parasitic vaccines: an utopia or reality?

Major advances in biotechnology over the past decade have led to significant progress in antigen selection, recombinant protein production and antigen delivery in a number of host-parasite systems. Vaccination against complex metazoan parasites has become a reality with the development of recombinant vaccines against the cattle tick Boophilus microplus and the sheep cestode Taenia ovis. In the present paper progress towards the development of similar vaccines against other parasites is discussed, with gastrointestinal nematodes and schistosomes in ruminants as examples. Special emphasis is put on antigen selection strategies and on the practical requirements for successful vaccination.