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A reovirus challenge model applicable in commercial broilers after live vaccination
A A W M van Loon1, B Suurland, P van der Marel
1Intervet International BV, P.O. Box 31, 5830 AA Boxmeer, The Netherlands. Adriaan.vanloon@intervet.com
Avian Pathology : Journal of the W.V.P.A
|November 12, 2002
Summary
A new reovirus challenge model accurately detects vaccine efficacy in chickens. This improved method uses specific monoclonal antibodies to differentiate between vaccine and challenge viruses, ensuring reliable results in broiler chickens.
Area of Science:
- Veterinary Virology
- Immunology
Background:
- Traditional reovirus challenge models in chickens have significant drawbacks, including subjective lesion scoring, difficulty inducing lesions in broilers, and animal suffering.
- Existing models struggle to differentiate between vaccine and challenge viruses, limiting their use for evaluating live attenuated vaccines.
- Alternative methods like virus reisolation or microscopic lesion scoring have limitations in specificity and correlation with challenge outcomes.
Purpose of the Study:
- To develop an improved reovirus challenge model for assessing vaccine efficacy in chickens.
- To create a model that can specifically detect challenge virus and differentiate it from vaccine virus.
- To evaluate the efficacy of an attenuated reovirus vaccine in specific pathogen-free (SPF) White Leghorn chickens and commercial broilers, including those with maternal immunity.
Main Methods:
- Developed a novel challenge model involving isolation of reovirus from various organs.
- Utilized a monoclonal antibody for specific detection and differentiation of challenge virus from vaccine virus.
- Conducted in vivo studies in SPF White Leghorn chickens and commercial broilers to assess vaccine efficacy under challenge conditions.
Main Results:
- The new model successfully detected challenge virus in unvaccinated control groups but not in vaccinated chickens.
- Vaccinated chickens demonstrated protection against reovirus challenge, even with maternal immunity.
- No reovirus antibodies were detected in protected birds at the time of challenge, suggesting a role for cellular immunity.
Conclusions:
- The developed reovirus challenge model is an improvement over existing methods, offering specific detection of challenge virus.
- The attenuated reovirus vaccine is effective in protecting chickens, including those vaccinated at one day old with maternal immunity.
- Protection induced by the vaccine may involve cellular immunity, as humoral immunity was not detected at the time of challenge.