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Vaccine. 2016 Jan 4;34(2):218-224. doi: 10.1016/j.vaccine.2015.11.037. Epub 2015 Nov 25.

Generation of a reassortant avian influenza virus H5N2 vaccine strain capable of protecting chickens against infection with Egyptian H5N1 and H9N2 viruses.

Author information

1
Center of Scientific Excellence for Influenza Viruses, National Research Centre, Giza, Egypt.
2
Microbiology Department, Ain Shams University, Egypt.
3
Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, United States.
4
Center of Scientific Excellence for Influenza Viruses, National Research Centre, Giza, Egypt. Electronic address: mohamedahmedali2004@yahoo.com.
5
Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, United States. Electronic address: ghazi.kayali@stjude.org.

Abstract

BACKGROUND:

Avian influenza H5N1 viruses have been enzootic in Egyptian poultry since 2006. Avian influenza H9N2 viruses which have been circulating in Egyptian poultry since 2011 showed high replication rates in embryonated chicken eggs and mammalian cells.

METHODS:

To investigate which gene segment was responsible for increasing replication, we constructed reassortant influenza viruses using the low pathogenic H1N1 PR8 virus as backbone and included individual genes from A/chicken/Egypt/S4456B/2011(H9N2) virus. Then, we invested this finding to improve a PR8-derived H5N1 influenza vaccine strain by incorporation of the NA segment of H9N2 virus instead of the NA of H5N1. The growth properties of this virus and several other forms of reassortant H5 viruses were compared. Finally, we tested the efficacy of this reassortant vaccine strain in chickens.

RESULTS:

We observed an increase in replication for a reassortant virus expressing the neuraminidase gene (N2) of H9N2 virus relative to that of either parental viruses or reassortant PR8 viruses expressing other genes. Then, we generated an H5N2 vaccine strain based on the H5 from an Egyptian H5N1 virus and the N2 from an Egyptian H9N2 virus on a PR8 backbone. This strain had better replication rates than an H5N2 reassortant strain on an H9N2 backbone and an H5N1 reassortant on a PR8 backbone. This virus was then used to develop a killed, oil-emulsion vaccine and tested for efficacy against H5N1 and H9N2 viruses in chickens. Results showed that this vaccine was immunogenic and reduced mortality and shedding.

DISCUSSION:

Our findings suggest that an inactivated PR8-derived H5N2 influenza vaccine is efficacious in poultry against H5N1 and H9N2 viruses and the vaccine seed replicates at a high rate thus improving vaccine production.

KEYWORDS:

Avian influenza virus; Reverse genetics; Vaccine

PMID:
26620838
PMCID:
PMC4698237
DOI:
10.1016/j.vaccine.2015.11.037
[Indexed for MEDLINE]
Free PMC Article

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