GP5,the major glycoprotein of PRRSV,is considered as one possible target of neutralizing antibodies,which however appear only late in infection.This was attributed to the presence of a "decoy epitope" located near a hypervariable region in the N-terminal domain of GP5.This region also harbors the predicted signal peptide cleavage sites and (dependent on the virus strain) a variable number of potential N-glycosylation sites.However,molecular processing of GP5 has not been addressed experimentally so far.It was not known whether and where the signal peptide is cleaved and thus whether the "decoy epitope" is present in virus particles.In addition,since signal peptide cleavage and N-glycosylation happen co-translationally they could influence each other,i.e.insertion and deletion of glycosylation sites in the hypervariable region might affect signal peptide cleavage and hence the presence of the "decoy-epitope".