The Global control of FMD - Tools, ideas and ideals – Erice, Italy 14-17 October 2008
Appendix 75
THE RELATION ANTIBODY AND PROTECTION AFTER FOOT-AND-MOUTH DISEASE VACCINATION CANNOT BE STANDARDISED A. Dekker1*, N. Goris2, S.M. Jamal3, Y. Li4 1 2
Central Veterinary Institute of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands Epizootic Diseases Section, Virology Department, Veterinary and Agrochemical Research Centre, Groeselenberg 99, 1180 Brussels, Belgium. 3 National Veterinary Laboratory, Park Road, 45500, Islamabad, Pakistan 4 Institute for Animal Health (IAH), Ash Road, Pirbright, Surrey GU24 0NF, UK
1. INTRODUCTION Many studies have been performed into the relation antibody response and protection after footand-mouth disease (FMD) vaccination (Black et al. 1984; Pay et al. 1987; Pay et al. 1992). In every study a correlation was observed with the antibodies induced by the vaccine used in the study and protection observed after challenge. In the studies the methodology was never the same, e.g. the type of cells used in the virus neutralisation test (VNT), some studies were using ELISA and the statistical analysis. For countries not in the position to perform challenge experiments a standardised relation between antibody response after FMD vaccination and protection would be very useful. In the current study we try to standardise antibody level detection for FMD type O Manisa in two different ways, first by using a standardised commercial type PrioCHECK® FMDV Type O ELISA and secondly by inclusion of a standard 4 week post vaccination serum from a cow vaccinated with Cedivac® O Manisa FMD vaccine in both the ELISA and the VNT. 2. MATERIALS AND METHODS 2.1 Data cattle potency tests Sera were available from 6 O Manisa potency tests performed in Lelystad (The Netherlands). One of these potency tests were performed with Al(OH)3 adjuvanted vaccine in which the cattle were challenged 3 weeks after vaccination as described in the European Pharmacopoeia. In the other 5 potency tests double oil adjuvanted vaccines were tested, and because the antibody response to oil emulsion vaccines is a bit slower it was decided to challenge the cattle 4 weeks after vaccination. Sera were available from 10 O Manisa potency performed by the Belgium national laboratory (Brussels) at the animal facilities of FGI-ARRIAH using the same batch of a double oil emulsion O Manisa vaccine (Goris et al. 2007). One set of sera from a potency test performed in Pirbright. Serological tests: Sera were titrated for this study in the national reference laboratory that had performed the potency tests, both in the PrioCHECK® FMDV Type O ELISA and the VNT. In each test a titration of a standard serum was included. The units of antibody were calculated by subtracting the 10log titre of the positive control from the observed titre. Statistical analysis: Titres of the control serum were compared using ANOVA followed by a pairwise comparison using Tukey honest significant difference. Serological responses were fitted by logistic regression. In each analysis the contribution of the laboratory performing the tests was included if this resulted in a better fitting model. The latter was tested by the likelihood ratio test. All statistical analyses were performed in R (www.r-project.org). 3. RESULTS Significant differences were found in the titre of the control serum obtained in the various laboratories, in both the ELISA and the VNT. In the ELISA significant (p<0.01) lower titres in Belgium (titre = 1.72 10log) were found in comparison with the titre found in the Netherlands (titre
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