Identification and characterization of novel immunogenic outer membrane proteins of Haemophilus parasuis serovar 5

Haemophilus parasuis is the aetiological agent of Glässer's disease, which is responsible for cases of fibrinous polyserositis, polyarthritis and meningitis in young pigs. To develop more effective vaccines, an immunoproteome-based approach was used to analyze the outer membrane proteins of H. parasuis serovar 5. A total of 15 proteins with high immunogenicity were identified and all were showed to be immunogens for the first time in H. parasuis. Further analyses of 8 selected proteins revealed that (1) significantly higher level of serum antibodies against 6 proteins was detected with convalescent sera and immunized sera; (2) antisera against 5 of the selected proteins could effectively inhibit H. parasuis growth in mouse blood; and (3) 4 proteins could induce protective response of the vaccinated mice against H. parasuis. The results suggest these 4 proteins (PalA, Omp2, D15 and HPS_06257) have strong potential to be vaccine candidates.