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Vaccine. 2001 Oct 12;20(1-2):125-33.

Characterization of a human H9N2 influenza virus isolated in Hong Kong.

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1
Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo, Japan. taksaito@nih.go.jp

Abstract

Two H9N2 viruses were isolated, for the first time, from humans in Hong Kong in 1999. Isolation of influenza viruses with a novel subtype of the hemagglutinin (HA) drew attention of health care authorities worldwide from the view of pandemic preparedness. Sequence analysis of the HA genes reveals that HA of A/Hong Kong/1073/99 (H9N2) is most closely related to that of A/quail/HK/G1/97 (H9N2) that contains the internal genes similar to those of Hong Kong/97 (H5N1) viruses. Phylogenetic and antigenic analyses demonstrated the diversity among H9 HA. A/Hong Kong/1073/99 was shown to cause a respiratory infection in Syrian hamsters, suggesting that the virus can replicate efficiently in mammalian hosts. We developed a whole virion test vaccine with a formalin-inactivated egg-grown HK1073. Intraperitoneal administration of the vaccine twice to hamsters conferred a complete protection against challenge infection by the MDCK cell-grown homologous virus. Receptor specificity of HK1073 appeared different from that of other avian influenza viruses of H9 subtype which recognize preferentially alpha-2,3 linked sialic acid. Hemagglutination of HK1073 with guinea pig erythrocytes was inhibited by both alpha-2,3 and alpha-2,6 linked sialic acid containing polymers. These data suggested that HK1073 had acquired a broader host range, including humans. Together with data so far available, the present study suggested that isolation of the H9 influenza viruses from humans requires precaution against the emergence of a novel human influenza.

PMID:
11567756
[Indexed for MEDLINE]
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