COMPARISON OF WHOLE-CELL ANTIGENS OF PRESSURE-KILLED AND FORMALIN-KILLED FLEXIBACTER-COLUMNARIS FROM CHANNEL CATFISH (ICTALURUS-PUNCTATUS)

Objective-To identify and compare immunodominant antigens in whole-cel l lysates of pressure-and formalin-killed Flexibacter columnaris. Anim als-Sera from naturally infected and vaccinated channel catfish. Proce dures-Whole-cell lysates of pressure- and formalin-killed F columnaris were compared, and antigens were isolated by sodium dodecyl sulfate-p olyacrylamide gel electrophoresis. The antigens were identified by sta ining, western blotting, and specific monoclonal antibodies to glycopr oteins. Western blotting was performed, using sera from channel catfis h (Ictalurus punctatus) with naturally acquired F columnaris infection and sera from channel catfish vaccinated with an experimental prototy pe F columnaris vaccine. Results-Whole-cell lysates of pressure and fo rmalin-killed F columnaris shared 4 proteins: 100, 80, 66, and 60 kd. The 60-kd antigen was a glycoprotein. Western blotting, using sera fro m naturally infected channel catfish, revealed the same proteins for p ressure-and formalin-killed F columnaris. Sera from vaccinated fish re acted only to pressure-killed lysate antigens. Conclusions-Pressure- a nd formalin-killed F columnaris whole-cell lysates share 100-, 80-, 66 -, and 60-kd proteins and are recognized by antibodies from naturally infected catfish and those vaccinated with formalin-killed F columnari s, Formalin treatment modifies or inactivates the 60-kd protein antige ns, rendering them unrecognizable to antibodies from channel catfish n aturally infected with F columnaris, suggesting that formalin-killed F columnaris may not be suitable for use as a bacterin against columnar is disease.