IDENTIFICATION OF IMMUNOREACTIVE PROTEINS IN Streptococcus agalactiae ISOLATED FROM NILE TILAPIA

 Streptococcus agalactiaeor Group B streptococcus is a causative agent of streptococcosis disease in numerous fish species. In Thailand, there are 2 major serotype of S. agalactiae, serotype Ia and III which display differently in their virulence. Hence, the identification of protein which potentially displays immunogenicity in animal might serve as an important target of vaccine candidate. In this study, immunoproteomics analysis of S.agalactiaeserotype Ia and III was identified by pull-down analysis with S. agalactiae(serotype III) anti-sera. The immunoreactive proteins were fractionated on SDS-PAGE (one-dimensional electrophoresis gel: 1-DE) prior identify the protein by Mass spectrometry. There are 44 immunoreactive proteins uniquely identified from S. agalactiaeserotype Ia and 64 immunoreactive proteins uniquely isolated from S. agalactiaeserotype III.

However, there are 10 immunoreactive proteins that shared immunoreactiveity between both serotype. The immunoreactiveity of two candidate immunoreactive proteins, pyruvate  kinase (pyk), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), were verified by Western blot analysis demonstrated specific immunoreactivity to serotype III antisera. The biological processes and molecular function revealed the majority of identified immunoreactive proteins were identified in a group of metabolic process and functioned in catalytic activities, respectively. Several proteins were localized in cytoplasmic and cytoplasmic membrane. The potential interaction networks of those immunoreactive proteins were generated which obligate the bacterial virulence. The protective effects of vaccine candidates are being tested. These identified proteins may serve as potential new target for vaccine development against piscine S. agalactiae.