Vaccination experiments and studies of the humoral immune responses in cod, Gadus morhua L., to four strains of monoclonal‐defined Vibrio anguillarum

Abstract

Abstract. Vibrio anguillarum isolated from diseased cod, Gadus morhua L., were serotyped by use of a panel of monoclonal antibodies. Four serotypes could be distinguished, having different lipopolysaccharide determinants. These phenotypic differences were also reflected in the genetic map, as revealed by fingerprinting of bacterial DNA. Antisera were raised in cod after immunization with the V. anguillarum serotypes, and Western blot techniques demonstrated production of specific antibodies mainly to LPS‐antigens. The immune system in cod discriminates to a eertain degree between the four serotypes as shown by crossreactions of the immune sera in elisa. Moreover, it was also shown that natural antibodies to bacterial antigens are present in non‐immune sera, but these specificities are non‐LPS in nature. As a consequence of the heterogeneity of the V. anguillarum strains, vaccination experiments were performed under laboratory conditions to compare the effectiveness of bacterins based on either single vaccines or polyvaccines. The results from these experiments were promising since challenge with one strain demonstrated 100% protection both in fish vaccinated with the homologous serotype as well as a mixture of all the four serotypes.

Immune parameters of immunised cod ( L.)

“…A T-cell independent antibody response, for example against polymeric structures like LPS, is low 84 compared to the antibody response to T-cell dependent antigens like proteins (Miller & Clem, 1984;Miller et al, 1985;Hoel et al, 1998). Vaccination of cod using formalin-killed Vibrio anguillarum or V. salmonicida produced good specific protection against these pathogens (Espelid et al, 1991;Schrøder et al, 1992). However, the specific humoral antibody response of cod immunised with these bacteria either by immersion or by i.p.…”

“…However, the specific humoral antibody response of cod immunised with these bacteria either by immersion or by i.p. injection was relatively poor and primarily directed against the bacterial lipopolysaccharide (LPS), a T-cell independent antigen (Espelid et al, 1991). A study by also indicated that cod did not produce antibodies against a protein antigen (oxazolone ovine albumin).…”

“…However, subsequent handling during sampling and immunisation was apparently not stressful for the cod and no opportunistic infections were detected as one would expect if the cod were severely a#ected by the handling. Also, the gentler method of immersion vaccination did not produce marked specific antibody response in cod but did secure specific disease protection (Espelid et al, 1991;Shrøder et al, 1992). Extensive studies of the genetic mechanism, which creates antibody diversity, have so far not revealed an inferior mechanism in cod compared to other fish species (Pilström & Bengtén, 1996;Pilström et al, 1998;Widholm et al, 1999;Stenvik et al, 2000).…”

“…This is in spite of the fact that vaccination with an attenuated pathogen results in specific protection against that pathogen (Espelid et al, 1991;Schrøder et al, 1992).…”

The carbohydrate moiety of serum IgM from Atlantic cod (Gadus morhua L.)

“…Studies of the functional role of the carbohydrate moiety of cod IgM are hampered by two factors: (i) the inability of cod to produce specific antibodies [34,45,46] and (ii) the limited growth and poor secretion of IgM by leucocytes in vitro (B. Magnadóttir, unpublished data). Both these factors limit the possibilities of studying, for example, the influence that the carbohydrate moiety might have on antigen binding, phagocytosis of pathogens/antigen or on complement activation, and the e#ects of various glycosylation enzymes/ enzyme inhibitors on the in vitro expression of carbohydrate on IgM.…”