vaccination against vhs in rainbow trout: experiments and perspectives related … ·...
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Vaccination against VHS in rainbow trout:
Experiments and perspectives related to practical fish farming
Niels LorenzenDanish Institute for Food and Veterinary Research
Nv ~ non-structural protein
Topics
• Traditional VHS vaccines
• DNA vaccines –Principle
–Safety
• Results from the lab
• Testing under fish farm conditions
• What is the origin of VHS?
Bacterial vaccines are produced by fermentation in simplegrowth substrate.
Bacteria in substrate
Fermentation
Vaccines against viruses?
Vaccines against viruses
• Traditional vaccines:Inactivated virus or attenuated virus
- usually too expensive or not safe enoughfor aquaculture
DNA vaccines: the principle
Virus particle Surface protein (G)
Gene cloning
Vaccine plasmid
De bedøvede fisk vaccineres med plasmid i rygmuskularturen
Vaccination
DNA vaccines: the principle
Virus particle Surface protein (G)
Gene cloning
Vaccine plasmid
De bedøvede fisk vaccineres med plasmid i rygmuskularturen
Vaccination
Plasmid DNA is easy to produce in bacteria
Fermentation
Purification
E.coli
DNA vaccines: the principle
Virus particle Surface protein (G)
Gene cloning
Vaccine plasmid
De bedøvede fisk vaccineres med plasmid i rygmuskularturen
Vaccination
GMO
Fermentation
Purification of plasmid
Not GMO
E.coli
DNA vaccination: Princip
Virus particle Surface protein (G)
Gene cloning
Vaccine plasmid
Vaccination byIntramuscularinjection
Fermentation +Purification
DNA vaccination of fish: intramuscular injection
Production of VHSV G-protein in fish cells
Fishcell
Transport to cell surface
Muscle of fish vaccinated with overdose of DNA vaccine -3 weeks after vaccination -
E. Lorenzen et al. Fish Shellfish Immunol.( 2005) 19:27-41
-5 weeks after vaccination -
E. Lorenzen et al. Fish Shellfish Immunol.( 2005) 19:27-41
Advantages of DNA vaccines
• High safety – no risk of disease, no GMO • Rapid and long-lasting protection • High stability• Simple to procedure
Disadvantages of DNA vaccines
• Injection vaccination not practical for small fish.
• Licensing/commercialisation complicated/expensive.
• Consumers acceptance important (in some countries).
Challenge experiments with DNA-vaccinated fish
in the laboratory
Challenge of vaccinated fish
VHS virus
Efficacy of the VHS DNA vaccine when tested in rainbow trout fingerlings at 12°C:
•Time-course•Specificity
0
20
40
60
80
100
cum
ulat
ive
mor
talit
y (%
)
0 5 10 15 20 days post challenge
8d,vhsG 19d,vhsG 28d,vhsG 61d,vhsG
112d,vhsG 168d,vhsG 168d,pcDNA3
Time-course studyBased on E. Lorenzen et al J. Aquat. Anim. Health. 12, 167-180, 2000
Time-course of protection following DNA vaccination against VHSV and IHNV
0
20
40
60
80
100
0 4 8 12 16 20 24Weeks post vaccination
RP
S
Non-specific mechanismsSpecific mechanismsTotal protection
Weeks postVaccination
IFN↑ Antibody ↑
106
N Lorenzen et al. Fish & Shellfish Immunology (2002) 12: 439-453.
The VHS DNA vaccine protects turbot against nodavirus challenge 8 days post vaccination
0
10
20
30
40
50
60
0 5 10 15 20 25
Time post challenge (days)
Cum
ulat
ive
mor
talit
y (%
) pVHSV-GpcDNA3.1(Contr.)pAHNV-C
Sommerset et al, Vaccine, 2003
Conclusions :
• The VHS DNA vaccine induces early non-specific as well as long-lasting specific protection.
• The VHS DNA vaccine seems to have an adjuvant- like effect
Field trialExperimental setup
• Vaccination at two different VHS-freefarms
Field trialExperimental setup
• Vaccination at two different VHS-freefarms
• Transfer of vaccinated fish to net-cages on farms with clinical VHS.
Collaborative project
• DFVF• Danish Aquaculture Association• GeneCare• The Danish Veterinary and Food Administration
Supported by Danish Ministry of Food, Agriculture and Fisheries
The Henriksen Foundation
Results from field-challenge with VHS:
High variability among cages: - high survival of vaccinated fish in
some cages- high mortality of all fish in other cages (other diseases than VHS)
Conclusions
• The DNA vaccine works under field conditions – but does not protect against other diseases.
• Experimental setup with net cages is not optimal.
• Next experiment should include vaccination of all fish in several ponds or all fish on selected farms in endemic zones.
Dansk AkvakulturVHS
First observation in Denmark in 1950
1965:520 Farms infected
2004:41 Farms infected
In Denmark, the strategy is still VHS-eradication byStamping-out
Very important to avoid re-introduction of virus
What is the origin of VHS virus?
VHS virus has been found more than 70 marine fish species
Based on Skall et al J Fish Dis. 2005 Sep;28(9):509-29
VHS in Europe might originate from the Baltic Sea
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DK4p168-1997IRF130297-1997DK4p101-1997FRL59-1987
UK86094-1994DK1p52-1996DK1p53-1996
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Who was the ancestor of VHSV in Europe?
EU
US
EU
EU
50 years
500 years
50 years 50 years
K. Einer-Jensen et al. J Gen Virol. (2004) 85:1167-79.
I
III
In order to avoid VHS:Always be careful when fish are
moved from one place to another!
Acknowledgements
• European Commission• The Danish Ministry for Food,
Agriculture and Fisheries• The Henriksen Foundation