ARS | Publication request: Passive immunization of channel catfish Ictalurus punctatus with anti-Flavobacterium columnare sera

Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 24, 2007
Publication Date: September 14, 2007
Citation: Shelby, R.A., Shoemaker, C.A., Klesius, P.H. 2007. Passive immunization of channel catfish Ictalurus punctatus with anti-Flavobacterium columnare sera. Diseases of Aquatic Organisms. 77: 143-147.

Interpretive Summary: Columnaris disease, caused by the bacterium Flavobacterium columnare, affects more than 36 fish species worldwide. This disease is particularly problematic for commercial production in pond-raised catfish and causes annual losses in the millions of dollars. We attempted to determine the basis of the humoral immune response in catfish to this disease by producing antibodies in separate groups of catfish. We produced antibody with two different types of columnaris antigen; whole killed columnaris cells and purified polysaccharide from columnaris cells. When injected into healthy catfish, both types of antigen produced antibody which could be detected by an ELISA and Western blotting assays. When these antibodies were injected into separate groups of healthy catfish partial immunity to columnaris disease was transferred. This was determined by challenge with live columnaris bacteria. Relative percent survival was 77 and 73 for catfish passively immunized with anti-LPS and anti-whole cell serum, respectively, while control fish experienced 100% mortality. This suggests that polysaccharides are an important antigenic component of F. columnare and that humoral antibody response is a key ingredient of immunity to this disease in catfish.

Technical Abstract: Passive immunization of channel catfish, Ictalurus punctatus (Rafinesque), was conducted to determine if anti-Flavobacterium columnare serum was protective when injected intraperitoneally (i.p.) into channel catfish. The anti-F. columnare serum was produced by actively immunizing (i.p. injection) channel catfish with sonicated whole cells or purified lipopolysaccharide (LPS) of F. columnare in Freund's adjuvant. Serum anti-F. columnare activity was verified by Western blotting and ELISA of serum. Normal serum and sterile culture broth were used as controls. Complement was inactivated in all sera by heating. After 48 hours, passively immunized fish were challenged with virulent F. columnare by i.p. injection. A group of unchallenged fish served as controls. The immune response of catfish to the antigenic fractions was different when examined by Western blotting. Antibody produced with whole cell antigen responded to a broad range of molecular weight components, while LPS antigens were restricted to a pair of bands near 20 kDa. Fourteen days post challenge, control fish injected with culture medium experienced 100% mortality. Relative percent survival was 77 and 73 for catfish passively immunized with anti-LPS and anti-whole cell serum, respectively. Results suggest that antibodies in the serum are involved in the protective immune response against columnaris disease in channel catfish.