Identification of broad cross-protective immunogens using heterogeneous antiserum-based immunoproteomic approach

Bacterium is still one of the major causes of life-threatening microbial infections. The most effective way to control bacterial infections is probably vaccine prevention. However, development of bacterial vaccine, especially polyvalent vaccines that could be used to fight against a variety of bacterial serotypes and species, is challenging due to the difficulty in identifying broad cross-protective antigens for different serotypes and species of pathogenic bacteria. In the present study, we developed a new approach to identify polyvalent vaccine candidates from outer membrane (OM) proteins of Vibrio alginolyticus with the ability to fight against infections caused by different genera and families of Gram-negative bacteria. This approach combined heterogeneous antiserum-based immunoproteomics with bacterial immunization challenging method. Four of the 35 protein spots resolved in a 2-DE gel of V. alginolyticus sarcosine-insoluble fraction could be recognized not only by homogeneous antiserum, but also by heterogeneous antisera obtained from other bacterial species, genera and families. The genes encoding the four OM proteins were then cloned and expressed in E. coli BL21. The expressed recombinant proteins were used as broadly cross-protective immunogens to immunize carps for investigation of their cross-protective spectra, activities and protective abilities in carps. The carps immunized with OmpA (VA0764) and Pal (VA1061) have abilities to fight against infections not only caused by V. alginolyticus, but also by Aeromonas hydrophila and Pseudomonas fluorescens. This study provides a novel approach for the identification of broadly cross-protective antigens, and possibly polyvalent vaccines against a variety of microbial infections.