H9N2 avian influenza virus in Korea: evolution and vaccination

Abstract

Low pathogenic avian influenza (LPAI) H9N2 viruses have been circulating in the Eurasian poultry industry resulting in great economic losses due to declined egg production and moderate to high mortality. In Korea, H9N2 LPAI was first documented in 1996 and it caused serious economic loss in the Korean poultry industry, including layer and broiler breeder farms. Since then, the H9N2 viruses that belong to the Korea group have been prevalent in chickens and have continuously evolved through reassortment in live bird markets. To control LPAI outbreaks, since 2007, the Korean veterinary authority has permitted the use of the inactivated oil adjuvant H9N2 LPAI vaccine. Although only oil-based inactivated vaccine using the egg-passaged vaccine virus strain (A/chicken/Korea/01310/2001) is permitted and used, several new technology vaccines have been recently suggested for the development of cost-effective and highly immunogenic vaccines. In addition, several different differentiation of infected from vaccinated animals (DIVA) strategies have been suggested using appropriate vaccines and companion serologic tests for discriminating between naturally infected and vaccinated animals. Recent reports demonstrated that the Korean LPAI H9N2 virus underwent antigenic drift and evolved into distinct antigenic groups and thus could escape from vaccine protection. Therefore, improved vaccination strategies including periodic updates of vaccine seed strains are required to achieve efficient control and eradication of LPAI H9N2 in Korea. Further, vaccination should be part of an overall integrated strategy to control the disease, including continued nation-wide surveillance, farm biosecurity, and DIVA strategy.

Molecular characterization of H9N2 avian influenza viruses isolated from vaccinated broiler chickens in northeast Iran

“…Therefore, it is important to investigate whether the circulating H9N2 viruses have undergone further significant genetic and antigenic changes with the advent of vaccination. Antigenic and phylogenetic analysis can also be effective approaches to vaccine development (Park et al 2011;Lee and Song 2013). Therefore, we characterized four H9N2 viruses recently isolated from commercial farms and the vaccine strain both antigenically and phylogenetically.…”

Antigenic Mapping of the Hemagglutinin of an H9N2 Avian Influenza Virus Reveals Novel Critical Amino Acid Positions in Antigenic Sites

“…With the massive vaccination against H9N2 infection in poultry in many countries, novel antigenic groups have emerged (34,(43)(44)(45). There is no doubt that a continuous and close surveillance on the antigenic evolution of H9N2 virus will facilitate better strategies for the control of H9N2 virus infection.…”

Rapid production of a H9N2 influenza vaccine from MDCK cells for protecting chicken against influenza virus infection

“…In the present study, we report that H 9 N 2 virus is adapted to MDCK cells for vaccine production. The circulation of H 9 N 2 viruses in the poultry industry results in great economic losses due to declines in egg production and moderate-to-high mortality (Lee and Song 2013). Our research provides a method for the rapid production of an influenza vaccine from MDCK cells to defend against influenza virus infection.…”

“…Over the last decade, several lineages of avian influenza H 9 N 2 viruses have become endemic in Asia, causing mild respiratory disease and reductions in egg production Dong et al 2010;Guan et al 2000;Lee and Song 2013;Nili and Asasi 2003;. The interspecies transmission of H 9 N 2 viruses raised concerns about the possibility of increased virulence for mammals and humans (Butt et al 2005;Cameron et al 2000;Cong et al 2007;Cong et al 2008;Guan et al 2000;Lin et al 2000), indicating that some H 9 N 2 viruses have gained the ability to replicate in mammalian cells.…”

“…Based on genetic features and/or severity of the disease in poultry, influenza viruses are classified as either highly pathogenic avian influenza virus (HPAIV) strains or low pathogenic avian influenza virus (LPAIV) strains that cause asymptomatic or moderate infections (Lee and Song 2013;Tombari et al 2011). The H 9 N 2 genotype is a stereotypical LPAIV and, since 1994, H 9 N 2 influenza viruses have become the most prevalent subtype in domestic poultry in Asia (Guo et al 2000;Lee and Song 2013;Liu et al 2003;Nili and Asasi 2003;). This has resulted in reduced egg production and increased mortality among poultry.…”