The effect of storing hybrid bass (Morone saxatilis × M. chrysops) sera at freezing temperatures on antibody titers

The effect of storing hybrid bass sera at freezing temperatures on their enzyme-linked immunosorbent assay (ELISA) titers was determined, and the precipitate formed during storage was characterized. Frozen bass sera from fish vaccinated with bacterial sonicate showed no titer in either of two groups—one immunized with bacterial sonicate and the other with sonicate emulsified in adjuvant. Fresh sera exhibited average titers of 1:32 in both groups and 1:20 in convalescent serum. bass antisera to bovine serum albumin showed maximum ELISA OD when sera were used after a short storage at 4 °C. Storage at freezing temperatures (−20 and −73 °C) reduced the OD value substantially. Sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis of the cryoprecipitate formed after freezing hybrid bass sera showed protein bands at 85 and 38 kDa, most probably the heavy and light chains, respectively, of bass IgM. Bands at 55, 52, 28, and 26 kDa may represent fibrinogen subunits. It is possible that the cryoprecipitate is composed of a fibrinogen net, which traps the tetrameric IgM molecules and precipitates them during frozen storage.