an A layer grown in iron depleted and iron supplemented conditions plus cells

An a layer grown in iron depleted and iron

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an A-layer) grown in iron-depleted and iron-supplemented conditions plus cells of Aer. bestiarum in TSB successfully protected goldfish against ulcer disease (RPS > 90%) when administered by immersion (-5 X 10^ cells/ml for 60 sec) fol- lowed by oral boosting over 7 days after 28 days (5 x 10^ cells/g of feed) (Robertson et ai, 2005). Avirulent cells, with altered A-layer, have also been proposed as candidates for live vaccines (Thornton et ai, 1991). However, a compHcation to the various developmental studies comes from the fascinating work of Norqvist et al. (1989), who used live attenuated cells of a different bacterial taxon, namely V. salmonicida, and reported their effectiveness at controlHng infections by Aer. salmonicida. A detailed study revealed that a 28 kDa outer-membrane pore-forming protein (= porin) from Aer. salmonicida led to the development of protective immunity in rainbow trout (Lutwyche et al., 1995). The commercial interest in polyvalent vaccines has resulted in several products, which are regularly used in Europe and elsewhere. The benefit of this approach to controlling furunculosis may be illustrated by the observation that Vibrio antigens, particularly V. salmonicida, appear to enhance the humoral immune response to Aer. salmonicida (Hoel et al, 1997). Moreover, vaccination with V. salmonicida antigens led to protection against Aer. salmonicida following challenge by co-habitation (Hoel et al, 1998a). This approach could well overcome the perceived problem that Aer. salmonicida is a weak antigen (Tatner, 1989). Also, this cross-protection may explain the often superior protection afforded by polyvalent vaccines (Hoel et al., 1998a). Concerning the use of rough and smooth strains for vaccine preparation, dis- crepancies are apparent among results obtained by different groups of investigators. Michel (1979) reported that there was no difference in the effectiveness of vaccines prepared with either rough or smooth cultures, when administered orally or via i.p. injection to rainbow trout. In fact, neither type of vaccine was protective. Yet, circulating antibodies were present in fish which received the vaccines via injection. Cipriano (1982a), examining the effectiveness of vaccines prepared from virulent and avirulent cultures, determined an equal level of protection from passive immunisation of brook trout. Similar agglutinin titres, i.e. 1:512, were found in both groups of vaccinated fish. He concluded, therefore, that protective immunogens were common to both virulent and avirulent cultures. In contrast, McCarthy et al. (1983) reported
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