Preparturient sow vaccination with a rIde derivative: Immunogenicity and protective efficacy against Streptococcus suis serotype 14

Streptococcus (S.) suis is an important causative agent of arthritis, meningitis and septicemia affecting pigs of different age groups, including suckling piglets. Accordingly, early protection of piglets against this pathogen is highly relevant. Vaccination of piglets with the recombinant IgM degrading enzyme of S. suis , Ide Ssuis , confers protection against mortality in weaning piglets experimentally challenged with serotype ( cps ) 2 and 14 of sequence type 1 or 9 of sequence types 50 and 94. The aim of this study was to determine immunogenicity and protective efficacy in the offspring of sows prime-boost vaccinated with a recombinant variant of Ide Ssuis formulated with the adjuvant Montanide ISA 25. Sows were vaccinated 5 and 2 weeks prior to farrowing and developed high levels of serum and colostrum α-Ide Ssuis IgG antibodies, which were shown to neutralize the IgM cleaving activity of Ide Ssuis . Piglets suckled by immunized sows had significantly higher specific α-Ide Ssuis IgG antibody levels compared to control piglets until the 11th week of life. Differentiation of IgG1 and IgG2 levels revealed that α-Ide Ssuis IgG2 levels in 2-week-old suckling piglets of vaccinated sows were comparable to respective levels of prime-boost-boost vaccinated weaning piglets using a formulation with the adjuvant Emulsigen, whereas α-Ide Ssuis IgG1 were lower in suckling piglets. Results of the intranasal challenge experiment suggested protection against morbidity in the 4th week of life against S. suis cps 14, in agreement with results of bactericidal assays. In conclusion, this study further confirms Ide Ssuis as a promising antigen for vaccination of sows pre-farrowing to control S. suis diseases.