1. Department of Biotechnology University of Malakand
Potency assessment of FMD vaccine using standardized serological assays
Syed M. Jamal
Department of Biotechnology
University of Malakand
Pakistan

2. Potency test for FMD vaccine
European Pharmacopoeia
Challenge protection studies in cattle
Determination of PD50
Limitations of Potency test:
Varying outcome
Disease security hazards
Costly
One valency in any given trial
Animal welfare

3. Serological based methods Alternatives to challenge-protection test provided that a correlation is established between antibody titre and protection
Advantages:
1. No logistic problems
2. No disease security hazards
3. Relatively in-expensive
4. More than one valency at given time
5. Simultaneous testing of several vaccines

4. Studies on correlation between antibody titre and protection
Mackowiak et al., 1962
van Bekkum, 1970
Sutmoller and Vieira, 1980
Pay and Hingley, 1987
van Maanen and Terpstra, 1989
Amadori et al., 1991
Pay and Hingley, 1992a,b
Dus Santos et al., 2000
Barnett et al., 2003

5. Test results often vary considerably between laboratories
Correlation between antibody titre and level of protection accepted worldwide
Test results often vary considerably between laboratories
difference between route and dose of challenge virus
the condition of cattle
the interval between vaccination and challenge
the type of serological test
sensitivity of cells used in neutralization test

6. Objectives
Standardization of antibody titres against O/Manisa for determination of vaccine potency using:
A standardized commercial PrioCHECK FMDV type O ELISA
Inclusion of a standard 4 week post-vaccination serum from a cow vaccinated with O/Manisa FMD vaccine in both the ELISA and VNT
The idea was to evaluate how serology to determine protection can be standardised; by standardising the test (all using the same ELISA kit) or by introducing a standard serum, irrespective of the test used. The latter is more promising, although differences still remain, but that might also be due to differences in vaccines used, vaccination challenge interval (4 weeks in the Netherlands, but 3 weeks in the other potency tests).

7. Materials and Methods
Serum samples from 18 potency tests performed at:
Belgium (n=10)
The Netherlands (n=6)
The United Kingdom (n=2)
Standard control serum (4 week post-vaccination serum from O/Manisa vaccinated cow)
Serum samples were tested in respective laboratories using:
Neutralization test
ELISA (PrioCHECK)
Unit/standardized antibody titres determined by subtracting the log titre of a standard control serum from that of the test serum
Results were analysed using logistic regression
Serum samples collected on the day of challenge.
Cell used in Pirbright=IBRS-2
Cells used in Ukkal, BHK
Cells used in Lelystad=Primary Porcine kidney cells

8. RESULTS: Antibody titres v/s protection
Significant difference in antibody titres among laboratories
The slope of the curve steeper in VNT compared to ELISA
Pirbright
Ukkal
Lelystad
Pirbright
Ukkal
Lelystad

9. Standardized/Units antibody titres v/s protection
Unit antibody titres reduced variation among laboratories
BUT
Significant difference still present
Pirbright
Ukkal
Lelystad
Pirbright
Ukkal
Lelystad

10. Conclusions
Inclusion of the standard serum reduced variation between the laboratories.
However, significant differences were still present, which could be due to differences in vaccine composition.
Inclusion of a standard serum is a good way to make results between laboratories more comparable.
Cattle vaccinated with 1/3rd dose of a standard FMD vaccine (containing 3 PD50) should have antibody titre at least as high as that of a standard serum representing 50% protection.

11. Acknowledgements CVI-lelystad, the Netherlands CODA-CERVA, Belgium
Pirbright Institute, United Kingdom
Thanks to the EuFMD for supporting my participation in the OS18