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Vaccine. 2019 Sep 30;37(42):6154-6161. doi: 10.1016/j.vaccine.2019.08.074. Epub 2019 Sep 5.

Bioengineering a highly productive vaccine strain in embryonated chicken eggs and mammals from a non-pathogenic clade 2·3·4·4 H5N8 strain.

Author information

1
Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, 08826 Seoul, Republic of Korea.
2
Department of Microbiology and Immunology, Emory University School of Medicine, 1510 Clifton Road, Atlanta, GA 30322, USA.
3
Avian Disease Division, Animal and Plant Quarantine Agency, 177, Hyeoksin 8-ro, Gyeongsangbuk-do 39660, Republic of Korea.
4
Laboratory of Avian Diseases, College of Veterinary Medicine, Konkuk University, 05029 Seoul, Republic of Korea.
5
Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, 08826 Seoul, Republic of Korea; Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, 08826 Seoul, Republic of Korea.
6
Laboratory of Poultry Medicine, Department of Farm Animal Medicine, College of Veterinary Medicine, Seoul National University, 08826 Seoul, Republic of Korea; Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, 08826 Seoul, Republic of Korea; Farm Animal Clinical Training and Research Center (FACTRC), GBST, Seoul National University, Kangwon-do, Republic of Korea. Electronic address: kwonhj01@snu.ac.kr.

Abstract

The clade 2·3·4·4 H5Nx is a highly pathogenic avian influenza (HPAI) virus, which first appeared in China and has spread worldwide since then, including Korea. It is divided into subclades a - d, but the PR8-derived recombinant clade 2·3·4·4 a viruses replicate inefficiently in embryonated chicken eggs (ECEs). High virus titer in ECEs and no mammalian pathogenicity are the most important prerequisites of efficacious and safer vaccine strains against HPAI. In this study, we have synthesized hemagglutinin (HA) and neuraminidase (NA) genes based on the consensus amino acid sequences of the clade 2·3·4·4a and b H5N8 HPAIVs, using the GISAID database. We generated PR8-derived H5N8 recombinant viruses with single point mutations in HA and NA, which are related to efficient replication in ECEs. The H103Y mutation in HA increased mammalian pathogenicity as well as virus titer in ECEs, by 10-fold. We also successfully eradicated mammalian pathogenicity in H103Y-bearing H5N8 recombinant virus by exchanging PB2 genes of PR8 and 01310 (Korean H9N2 vaccine strain). The final optimized H5N8 vaccine strain completely protected against a heterologous clade 2·3·4·4c H5N6 HPAIV in chickens, and induced hemagglutination inhibition (HI) antibody in ducks. However, the antibody titer of ducks showed age-dependent results. Thus, H103Y and 01310PB2 gene have been successfully applied to generate a highly productive, safe, and efficacious clade 2·3·4·4 H5N8 vaccine strain in ECEs.

KEYWORDS:

Clade 2·3·4·4; H103Y; H5N8; Highly pathogenic avian influenza; Vaccine

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