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Open Access Research

Improved hatchability and efficient protection after in ovo vaccination with live-attenuated H7N2 and H9N2 avian influenza viruses

Yibin Cai12, Haichen Song3, Jianqiang Ye12, Hongxia Shao12, Rangarajan Padmanabhan124, Troy C Sutton12 and Daniel R Perez12*

Author Affiliations

1 Department of Veterinary Medicine, University of Maryland, College Park, 8075 Greenmead Drive, College Park, MD 20742-3711, USA

2 Virginia-Maryland Regional College of Veterinary Medicine, 8075 Greenmead Drive, College Park, MD 20742-3711, USA

3 Synbiotics Co. 8075 Greenmead Drive, College Park, MD 20742-3711, USA

4 Department of Animal and Avian Sciences, University of Maryland College Park, 1413 Animal Sciences Center, College Park, MD 20742-2311, USA

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Virology Journal 2011, 8:31  doi:10.1186/1743-422X-8-31

Published: 21 January 2011

Abstract

Mass in ovo vaccination with live attenuated viruses is widely used in the poultry industry to protect against various infectious diseases. The worldwide outbreaks of low pathogenic and highly pathogenic avian influenza highlight the pressing need for the development of similar mass vaccination strategies against avian influenza viruses. We have previously shown that a genetically modified live attenuated avian influenza virus (LAIV) was amenable for in ovo vaccination and provided optimal protection against H5 HPAI viruses. However, in ovo vaccination against other subtypes resulted in poor hatchability and, therefore, seemed impractical. In this study, we modified the H7 and H9 hemagglutinin (HA) proteins by substituting the amino acids at the cleavage site for those found in the H6 HA subtype. We found that with this modification, a single dose in ovo vaccination of 18-day old eggs provided complete protection against homologous challenge with low pathogenic virus in ≥70% of chickens at 2 or 6 weeks post-hatching. Further, inoculation of 19-day old egg embryos with 106 EID50 of LAIVs improved hatchability to ≥90% (equivalent to unvaccinated controls) with similar levels of protection. Our findings indicate that the strategy of modifying the HA cleavage site combined with the LAIV backbone could be used for in ovo vaccination against avian influenza. Importantly, with protection conferred as early as 2 weeks post-hatching, with this strategy birds would be protected prior to or at the time of delivery to a farm or commercial operation.