With the advent of emerging resistance against anthelmintic drugs, vaccination is often put forward as the most rational and cost-effective alternative to control infections with parasitic worms. In recent years, 2 experimental vaccines against the bovine parasites Ostertagia ostertagi and Cooperia oncophora were developed that are based on the use of activation-associated secreted proteins (ASP) released by adult worms. The further development and commercialisation of these two experimental vaccines faces one fundamental challenge, i.e. the large scale, cost-effective production of the antigens. Despite the protective capacities of the purified native ASPs, so far no protection was obtained after immunisation of calves with different recombinant versions of these antigens. This indicates that the native ASPs trigger the bovine immune system in a unique manner. Recent research has shown that the N-linked glycans present on the native proteins play a role in the vaccine-induced immunity. The aim of this PhD project is to unravel how these sugars exactly steer the immune response and subsequently use this information to direct recombinant expression work.