The immune response in immunized and naturally infected rainbow trout (Salmo gairdneri) to Diplostomum spathaceum as detected by enzyme-linked immunosorbent assay (ELISA).

The enzyme-linked immunosorbent assay (ELISA) procedure was modified and adapted for detection of circulating antibodies in rainbow trout (Salmo gairdneri) against metacercariae of the digenean trematode Diplostomum spathaceum, the causative agent for diplostomiasis. Rainbow trout (Salmo gairdneri) were injected with sonicated metacercariae representing 10, 40, and 100 metacercariae per fish. Three weeks after immunization the average titers for trout injected with 10, 40, and 100 metacercariae were 874, 841, and 525, and by six weeks the titers had fallen to 299, 349, and 203, respectively. Nine weeks after initial immunization, two remaining fish initially immunized with 100 metacercariae per fish were injected with a booster of 50 sonicated metacercariae per fish. Four weeks later the average titer was 1204. Serum samples from naturally infected wild fish tested for the presence of circulating antibodies against Diplostomum spathaceum showed 25 of 27 with positive titers.

Characterization of immunoglobulins from the brown bullhead (Ictalurus nebulosus) produced against a naturally occurring bacterial pathogen, Aeromonas hydrophila.

The primary immune response in the brown bullhead (Ictalurus nebulosus) to intramuscularly injected, chloroform-killed Aeromonas hydrophila reached an agglutination titer of 128 in 3 wk, and the response to the bacteria plus adjuvant reached a titer of 512 in 5 wk. Anti-Aeromonas hydrophila antibodies from brown bullheads were excluded from Sephadex G-200 and had an immunoelectrophoretic migration pattern toward the cathode. Cleavage of the macromolecule by 2-ME reduction and iodoacetamide alkylation yielded subunits that were resumptively heavy chains of about 50,500 daltons and light chains of about 22,500 daltons. Bullhead antibodies were assumed to be tetrameric in configuration and therefore to have an approximate molecular weight of 600,000 daltons assuming a J chain is present in both early (6 wk) and late (20 wk) immune sera. The agglutinating activity of the antibody was completely eliminated by exposure to 65 degrees C for 30 min. Immunoelectrophoresis showed a single antibody component that moved toward the cathode. The structure and molecular weight of bullhead antibodies appears similar to that observed in channel catfish and other closely related teleost fish.