The larval stage of the cestode Echinococcus multilocularis is the causative agent of alveolar echinococcosis, a lethal disease if untreated. To date, drug treatment options are limited, non-curative and need improvement. In this project we investigated the proteomic composition of in vitro generated metacestodes that are the disease-causing stage of the parasite. We analysed the composition of the vesicle tissue (VT), the vesicle fluid (VF), as well as the changes in the surrounding culture medium (CM). Further we compared the composition of VF ex vivo material from infected mice. As antigen B (AgB) subunits were the most prominent proteins in both VFs and CM, we followed up on these specific proteins and assessed the possibility of re-uptake of AgB into the metacestode, by targeted proteomics against HA-tagged AgB. Six proteomic analyses were performed: 1_ VF and VT 2_ CM (in vitro samples) 3_ VF ex vivo samples from infected mice 4_ HA-AgB8 calibration (in vitro samples) 5_ HA-AgB8/1 uptake (in vitro samples) 6_ HA-AgB8/2 uptake (in vitro samples)