Immunogenicities of vaccines including the immunoglobulin M-degrading enzyme of , rIde , and protective efficacy against serotype 14 in piglets.

() is a major porcine pathogen. Some strains have a substantial zoonotic potential such as serotype () 14 as the second most important in human infections. To this date no licensed vaccine is available in Europe though subunit vaccines and bacterins have been examined by several scientific groups worldwide. Objectives of this study were to determine protective efficacy of rIde vaccination against intranasal 14 challenge in conventional weaned piglets and to investigate additionally immunogenicity of rIde vaccination in cesarean-derived colostrum-deprived (CDCD) piglets. Immunization led to reduction of bacterial multiplicity in porcine blood and delayed onset of clinical signs of 14 disease in conventional rIde -vaccinated piglets. However, significant differences were not recorded which might be related to comparable low anti-Ide antibody levels and insufficient neutralization of IgM protease activity in this animal experiment. In contrast, immunization of cesarean-derived colostrum-deprived piglets with rIde resulted in high α-rIde IgG antibody levels and a highly significant reduction of the survival factor of the 14 challenge strain in porcine blood . In conclusion, the results of this study indicate bactericidal immunity against 14 by Ide specific immunity.