Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 1997
Publication Date: N/A
Interpretive Summary: Flexibacter columnaris is the causative agent of columnaris disease in channel catfish and various species world-wide. At present no effective vaccine against this disease has been developed. One possible candidate for a columnaris vaccine is a whole-cell bacterial lysate. Two methods for the production of this whole-cell bacterial lysate are pressure and formalin treatment. This paper reports on a series of experiments conducted to identify and compare the immunodominant antigens within pressure- and formalin-killed lysates which are recognized by the immune system of channel catfish infected with F. columnaris. Various immunological and molecular biological techniques were used to separate and identify pressure- and formalin-killed bacterial whole-cell lysate antigens. Results show that the immunodominant antigens between the 2 treatments differed from one another according to preparation, but share 4 proteins: 100, 80, 66, and 60 kDa. The 60 kDa antigen was identified as a glycoprotein. It appears that formalin treatment modifies or inactivates the 60 kDa antigen in the formalin-killed and this antigen is important in the immune response to columnaris disease and the development of a vaccine.
Technical Abstract: OBJECTIVE - To identify and compare immunodominant antigens in whole-cell lysates of pressure and formalin-killed Flexibacter columnaris. PROCEDURES - Whole-cell lysates of pressure and formalin-killed F. columnaris were compared and antigens isolated by SDS-PAGE staining, immunoblotting for glycoproteins, and western blotting. Western-blotting utilized sera from naturally infected channel catfish (Ictalurus punctatus) with F. columnaris and sera from channel catfish vaccinated with experimental prototype F. columnaris vaccine (ALPHARMA Inc.). RESULTS - Whole-cell lysates of pressure and formalin-killed F. columnaris shared 4 proteins:100, 80, 66 and 60 kDa. The 60 kDa antigen was a glycoprotein. Western-blotting with naturally infected channel catfish sera showed the same proteins with both pressure and formalin-killed F. Columnaris. Vaccinated fish sera reacted only to pressure-killed lysate antigens. CONCLUSIONS - Pressure- and formalin-killed F. columnaris whole-cell lysates share 100, 80, 66 and 60 kDa proteins and are recognized by antibodies from naturally infected and formalin-killed F. columnaris vaccinated channel catfish. Formalin treatment modifies or inactivates the 60 kDa protein antigens rendering it unrecognizable to antibodies from channel catfish naturally infected with F. columnaris suggesting that formalin-killed F. columnaris may not be a usable bacterin against columnaris disease.