181
Bivalent formalin-inactivated whole cell preparations containing Lactococcus
garvieae and Aer. hydrophila with and without Montanide ISA-763 as adjuvant
were administered by intraperitoneal injection (0.1 ml amounts containing 1 × 10
8
cells/fi sh) to rainbow trout, and challenged after 30 days with a RPS for Aer.
hydrophila of 100 % and 95.3 % for non adjuvanted and adjuvanted preparation,
respectively. At 90 days after vaccination, challenge resulted in decreased protection of the non-adjuvanted preparation against Aer. hydrophila (RPS = 85 %) but not
so for the adjuvanted product (RPS = 95 %) (Bastardo et al. 2012 ).
Attenuated live vaccines have been evaluated. Thus a rough attenuated derivative
produced by repeated sub-culturing on BHIA for 8-years was reported to confer
immune protection in rohu (Swain et al. 2010 ). Three attenuated products with
resistance to novobiocin and rifampicin were developed, and applied intraperitoneally (dose = 4 × 10
5 CFU) to channel catfi sh. The outcome was RPS values of
86–100 % (Pridgeon and Klesius 2011 ).
Concerning the method of vaccine inactivation, Lamers and de Haas ( 1983 )
deduced that heat-inactivated vaccines (60 °C/1 h) gave superior results to formalised products (0.3 % formalin). However, it was apparent that concentration of
the vaccine, in terms of the numbers of cells, was very important in eliciting an
immune response. Thus, using carp as the experimental animal, Lamers and de
Haas ( 1983 ) concluded that 10
7 –10
9 cells generated a distinct agglutinating response
whereas 10
5 cells did not. Moreover, secondary doses of vaccine were shown to be
benefi cial. Nevertheless, single doses of a formalin-inactivated vaccine (containing
10
7 –10
9 cells), administered via i.m. injection, were capable of eliciting an immune
response which was maintained for 360 days. This demonstrates that fi sh have
immunological memory (Lamers et al. 1985a ). Continuing the work, Lamers et al.
( 1985b ) vaccinated carp by bathing. Although a single immersion did not result in
signifi cant serum antibody levels, secondary vaccination after 1, 3 or 8 months gave
rise to a dramatic immune response. In particular, the highest response resulted
from using booster doses at 3 months. However at 12 months, there was no response.
The ability of Aer. hydrophila to develop biofi lms on surfaces has been exploited,
and a study with walking catfi sh (Clarias batrachus) demonstrated that cells from
biofi lms on chitin fl akes gave a higher RPS (=91–100 %) and serum antibody titre
when administered orally for 20 days compared to preparations derived from suspensions in TSB (RPS = 29–42 %) (Nayak et al. 2004 ). Similarly, Azad et al. ( 1999 )
used an oral biofi lm vaccine (dose = 10
10 and 10
13 CFU/g; the bacterial cells were
grown on chitin fl akes) for 15 days in carp and demonstrated high humoral antibody
titres and protection. A parallel study involved a biofi lm oral vaccine, which was fed
at 10
10 cells/g of fi sh/day for 20 days, to prevent disease caused by Aer. hydrophila
in snakehead ( Channa striatus ), and led to the development of signifi cant antibody
titre and an RPS of 88 % after challenge (Siriyappagouder et al. 2014 ). The question
about what is so special about biofi lms needs to be addressed.
Subcellular components, particularly LPS, offer promise as components of vaccines (Grochola et al. 2015 ). Indeed, evidence has been presented that LPS induces
cell-mediated protection (= regulates T-cell like macrophage system) in carp (Baba
et al. 1988 ). Loghothetis and Austin ( 1996 ) echoed this view about the immunogeAeromonas hydrophila
Bivalent formalin-inactivated whole cell preparations containing Lactococcus
garvieae and Aer. hydrophila with and without Montanide ISA-763 as adjuvant
were administered by intraperitoneal injection (0.1 ml amounts containing 1 × 10
8
cells/fi sh) to rainbow trout, and challenged after 30 days with a RPS for Aer.
hydrophila of 100 % and 95.3 % for non adjuvanted and adjuvanted preparation,
respectively. At 90 days after vaccination, challenge resulted in decreased protection of the non-adjuvanted preparation against Aer. hydrophila (RPS = 85 %) but not
so for the adjuvanted product (RPS = 95 %) (Bastardo et al. 2012 ).
Attenuated live vaccines have been evaluated. Thus a rough attenuated derivative
produced by repeated sub-culturing on BHIA for 8-years was reported to confer
immune protection in rohu (Swain et al. 2010 ). Three attenuated products with
resistance to novobiocin and rifampicin were developed, and applied intraperitoneally (dose = 4 × 10
5 CFU) to channel catfi sh. The outcome was RPS values of
86–100 % (Pridgeon and Klesius 2011 ).
Concerning the method of vaccine inactivation, Lamers and de Haas ( 1983 )
deduced that heat-inactivated vaccines (60 °C/1 h) gave superior results to formalised products (0.3 % formalin). However, it was apparent that concentration of
the vaccine, in terms of the numbers of cells, was very important in eliciting an
immune response. Thus, using carp as the experimental animal, Lamers and de
Haas ( 1983 ) concluded that 10
7 –10
9 cells generated a distinct agglutinating response
whereas 10
5 cells did not. Moreover, secondary doses of vaccine were shown to be
benefi cial. Nevertheless, single doses of a formalin-inactivated vaccine (containing
10
7 –10
9 cells), administered via i.m. injection, were capable of eliciting an immune
response which was maintained for 360 days. This demonstrates that fi sh have
immunological memory (Lamers et al. 1985a ). Continuing the work, Lamers et al.
( 1985b ) vaccinated carp by bathing. Although a single immersion did not result in
signifi cant serum antibody levels, secondary vaccination after 1, 3 or 8 months gave
rise to a dramatic immune response. In particular, the highest response resulted
from using booster doses at 3 months. However at 12 months, there was no response.
The ability of Aer. hydrophila to develop biofi lms on surfaces has been exploited,
and a study with walking catfi sh (Clarias batrachus) demonstrated that cells from
biofi lms on chitin fl akes gave a higher RPS (=91–100 %) and serum antibody titre
when administered orally for 20 days compared to preparations derived from suspensions in TSB (RPS = 29–42 %) (Nayak et al. 2004 ). Similarly, Azad et al. ( 1999 )
used an oral biofi lm vaccine (dose = 10
10 and 10
13 CFU/g; the bacterial cells were
grown on chitin fl akes) for 15 days in carp and demonstrated high humoral antibody
titres and protection. A parallel study involved a biofi lm oral vaccine, which was fed
at 10
10 cells/g of fi sh/day for 20 days, to prevent disease caused by Aer. hydrophila
in snakehead ( Channa striatus ), and led to the development of signifi cant antibody
titre and an RPS of 88 % after challenge (Siriyappagouder et al. 2014 ). The question
about what is so special about biofi lms needs to be addressed.
Subcellular components, particularly LPS, offer promise as components of vaccines (Grochola et al. 2015 ). Indeed, evidence has been presented that LPS induces
cell-mediated protection (= regulates T-cell like macrophage system) in carp (Baba
et al. 1988 ). Loghothetis and Austin ( 1996 ) echoed this view about the immunogeAeromonas hydrophila