QUALITATIVE DIFFERENCES IN THE IMMUNE-RESPONSE OF RABBIT, MOUSE AND SEA BASS, DICENTRARCHUS-LABRAX, L TO PHOTOBACTERIUM-DAMSELA SUBSP PISCICIDA, THE CAUSATIVE AGENT OF FISH PASTEURELLOSIS

Sera raised in rabbits, mice and sea bass against Photobacterium damse la subsp. piscicida (Ph.d.p.) cultured both in normal laboratory mediu m and under iron-limited conditions were analysed by Western blot. Ser a collected from sea bass after injection with both live and heat-kill ed Ph.d.p. cells were also analysed. All analysed sera reacted with tw o groups of Ph.d.p. cell antigens, one (an array of products) assigned as a high molecular weight group and another (lipopolysaccharide and/ or lipoprotein) assigned as a low molecular weight group. Each serum t ested differed in its reaction by Western blot. Cells cultured under i ron-limited conditions demonstrated, both qualitatively and quantitati vely, elevated immunogenicity. Great variation among the sera was evid ent with reference to the recognition of antigens in the high molecula r weight group of Ph.d.p. products, with the sea bass serum raised aga inst live cells demonstrating reaction against a wider range of cell m aterial. Lipopolysaccharide and/or lipoprotein situated in the low mol ecular weight group products appeared to be the most immunogenic mater ial in the bacterial cell. A 15.5 kDa antigen was recognised only from seabass serum raised against live cells. The findings of this study a re discussed in relation to future vaccine development. (C) 1997 Acade mic Press Limited.