Immunoproteomics selection of cross-protective vaccine candidates from Riemerella anatipestifer serotypes 1 and 2

Riemerella anatipestifer (RA) is one of the most important bacterial pathogens of ducks and other avian species worldwide. Current approaches for controlling RA are hindered by the absence of effective vaccines, particularly cross-protective vaccines. In this present study, an immunoproteomics approach was used to identify cross-protective vaccine candidates against RA serotype 1 strain RAf63 and serotype 2 strain RAf153. First, whole-cell and secreted proteins of RAf153 and RAf63 were separated by two-dimensional gel electrophoresis. Then, western blotting of the proteome was performed using duck convalescent serum against RAf153, followed by matrix-assisted laser desorption/ionization time of flight mass spectrometry and peptide mass fingerprinting. Finally, common immunoreactive proteins from RAf153 and RAf63 were identified as cross-protective vaccine candidates, and so these were cloned and expressed recombinantly. The cross-protection abilities of purified recombinant protein vaccines were tested against homologous and heterologous virulent strains in a challenge model that followed vaccination. Six proteins were identified as cross-protective vaccine candidates. Three of these proteins showed reactivity with convalescent sera after prokaryotic expression, and the recombinant outer membrane protein A (OmpA) showed high protective indices against challenges with RAf153 (60%) and RAf63 (50%). In summary, we have developed a high-throughout, accurate, rapid and efficient method for the successful selection of cross-protective vaccine candidates.