Genetic characterization and pathogenicity assessment of highly pathogenic H5N1 avian influenza viruses isolated from migratory wild birds in 2011, South Korea

College of Medicine and Medical Research Institute, Chungbuk National University, 12 Gaeshin-Dong Heungduk-Ku, Cheongju 361-763, Republic of Korea.
Virus Research (Impact Factor: 2.32). 07/2011; 160(1-2):305-15. DOI: 10.1016/j.virusres.2011.07.003
Source: PubMed


The continued spread of a highly pathogenic avian influenza (HPAI) H5N1 virus among wild birds and poultry has posed a potential threat to human public health. In the present study, we report the isolation of HPAI H5N1 viruses (A/Md/Korea/W401/11 and A/Md/Korea/W404/11) from fecal samples of migratory birds. Genetic and phlyogenetic analyses demonstrated that these viruses are genetically identical possessing gene segments from avian virus origin and showing highest sequence similarities (as high as 99.8%) to A/Ws/Hokkaido/4/11 and 2009-2010 Mongolian-like clade 2.3.2 isolates rather than previous Korean H5N1 viruses. Both viruses possess the polybasic motif (QRERRRK/R) in HA but other genes did not bear additional virulence markers. Pathogenicity of A/Md/Korea/W401/11 was assessed and compared with a 2006 clade 2.2 HPAI H5N1 migratory bird isolate (A/EM/Korea/W149/06) in chickens, ducks, mice and ferrets. Experimental infection in these hosts showed that both viruses have high pathogenic potential in chickens (2.3-3.0 LD(50)s) and mice (3.3-3.9 LD(50)s), but A/Md/Korea/W401/11 was less pathogenic in duck and ferret models. Despite recovery of both infection viruses in the upper respiratory tract, efficient ferret-to-ferret transmission was not observed. These data suggest that the 2011 Korean HPAI wild bird H5N1 virus could replicate in mammalian hosts without pre-adaptation but could not sustain subsequent infection. This study highlights the role of migratory birds in the perpetuation and spread of HPAI H5N1 viruses in Far-East Asia. With the changing pathobiology caused by H5N1 viruses among wild and poultry birds, continued surveillance of influenza viruses among migratory bird species remains crucial for effective monitoring of high-pathogenicity or pandemic influenza viruses.

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Available from: Philippe Noriel Q. Pascua, Jun 03, 2014
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    • "In studies of chickens experimentally infected with HPAI H5N1, immunohistochemical and histopathological analysis detected viral antigens in vascular epithelial cells, alveolar macrophages and the parenchyma of all major internal organs: lung, colon, brain, spleen, liver, kidney and heart. The presence of viral antigen staining in organ tissue sections was accompanied by severe inflammation and apoptosis (Isoda et al., 2006; Jeong et al., 2009; Karpala et al., 2011; Kwon et al., 2011; Suarez et al., 1998; Suzuki et al., 2009; Wasilenko et al., 2009). Identification of the molecular determinants of H5N1 transmission and virulence in poultry is critical for future influenza surveillance and therapeutic development. "
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