291
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 ). Moreover, the immunogenicity of T3SS was
evaluated in rainbow trout by administering two formalin-inactivated whole cell
products one of which was an isogenic strain with a deletion of the T3SS gene by
i.p. injection with challenge 8-weeks later. Survival was better with the with the
product based on the isogenic strain with which proteomics revealed that deletion
resulted in expression of all the components of T3SS, some of which were immunosuppressive. The conclusion reached was that vaccines containing T3SS proteins
led to decreased protection (Bergh et al. 2013 ). However, Schwenteit et al. ( 2015 )
constructed mutant strains secreting AsaP1-toxoid instead of the toxin (AsaP1 = a
metalloendopeptidase, which is expressed as a 37-kDa pre-pro-peptide and processed to a 19-kDa active peptide). An inactivated whole cell vaccine based on the
AsaP1(Y309F)-toxoid mutant (this had weak caseinolytic activity and was processed to the 19-kDa peptide) protected Arctic charr against challenge, with the
level of protection stated to be comparable with a commercial product (Schwenteit
et al. 2015 ).
The commercial interest in polyvalent vaccines has resulted in several products,
which are regularly used in Europe and elsewhere. The benefi t 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 cohabitation
(Hoel et al. 1998 ). 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.
1998 ).
Concerning the use of rough and smooth strains for vaccine preparation, discrepancies 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 fi sh that 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 fi sh. He concluded, therefore, that protective immunogens were common to both virulent and avirulent cultures. Chicken egg yolk powder containing
immunoglobulin, IgY, was used in the fi sh-rearing water to successfully control to
ulcer disease in koi carp (Gan et al. 2015 ).
McCarthy et al. ( 1983 ) reported that, in general, only rough variants conferred
protective immunity. A parallel result emanated from the work of Olivier et al.
( 1985a ), who ascertained that avirulent cells were less effective immunogens than
their virulent counterparts. Both of these groups regarded the A-layer protein as the
antigen that probably conferred a protective response by the fi sh. In another develAeromonas 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 ). Moreover, the immunogenicity of T3SS was
evaluated in rainbow trout by administering two formalin-inactivated whole cell
products one of which was an isogenic strain with a deletion of the T3SS gene by
i.p. injection with challenge 8-weeks later. Survival was better with the with the
product based on the isogenic strain with which proteomics revealed that deletion
resulted in expression of all the components of T3SS, some of which were immunosuppressive. The conclusion reached was that vaccines containing T3SS proteins
led to decreased protection (Bergh et al. 2013 ). However, Schwenteit et al. ( 2015 )
constructed mutant strains secreting AsaP1-toxoid instead of the toxin (AsaP1 = a
metalloendopeptidase, which is expressed as a 37-kDa pre-pro-peptide and processed to a 19-kDa active peptide). An inactivated whole cell vaccine based on the
AsaP1(Y309F)-toxoid mutant (this had weak caseinolytic activity and was processed to the 19-kDa peptide) protected Arctic charr against challenge, with the
level of protection stated to be comparable with a commercial product (Schwenteit
et al. 2015 ).
The commercial interest in polyvalent vaccines has resulted in several products,
which are regularly used in Europe and elsewhere. The benefi t 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 cohabitation
(Hoel et al. 1998 ). 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.
1998 ).
Concerning the use of rough and smooth strains for vaccine preparation, discrepancies 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 fi sh that 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 fi sh. He concluded, therefore, that protective immunogens were common to both virulent and avirulent cultures. Chicken egg yolk powder containing
immunoglobulin, IgY, was used in the fi sh-rearing water to successfully control to
ulcer disease in koi carp (Gan et al. 2015 ).
McCarthy et al. ( 1983 ) reported that, in general, only rough variants conferred
protective immunity. A parallel result emanated from the work of Olivier et al.
( 1985a ), who ascertained that avirulent cells were less effective immunogens than
their virulent counterparts. Both of these groups regarded the A-layer protein as the
antigen that probably conferred a protective response by the fi sh. In another develAeromonas salmonicida