Readaptation of a low-virulence influenza H9 escape mutant in mice: the role of changes in hemagglutinin as revealed by site-specific mutagenesis
In our earlier studies, we showed that an escape mutant of mouse-adapted H9N2 influenza virus carrying a T198N amino acid change in heamagglutinin (HA) has a lowered virulence for mice. The readaptation of this mutant to mice was associated with N198S or N198D reverse mutations. In this study, single-gene reassortants having HA gene of the wild-type virus, its low-virulence escape mutant, or a readapted variant were generated by site-specific mutagenesis and assayed for virulence. The results showed that antibody-selected mutations in the HA of H9 influenza virus can decrease mortality and virus accumulation in mouse lungs, though not in nasal turbinates, and the effect may be compensated by reverse mutations in the course of passaging.
KeywordsInfluenza Virus Amino Acid Change Virus Accumulation Escape Mutant Swine Influenza Virus
This study was supported by Contract HHSN266200700005C with the National Institute of Allergy and Infectious Diseases, by the American Lebanese Syrian Associated Charities (ALSAC), by Russian Federation For Basic Research grant #07-04-00005, and by NATO Collaborative Linkage Grant 979155.
- 5.Guo Y, Li J, Cheng X (1999) Discovery of humans infected by avian influenza A (H9N2) virus. Chin J Exp Clin Virol 13:105–108 (Zhonghua Shi Yan He Lin Chuang Bing Du Xue Za Zhi)Google Scholar
- 13.Lin YP, Shaw M, Gregory V, Cameron K, Lim W, Klimov A, Subarrao K, Guan Y, Krauss S, Shortridge K, Webster R, Cox N, Hay A (2000) Avian-to-human transmission of H9N2 subtype influenza A viruses: relationship between H9N2 and H5N1 human isolates. Proc Natl Acad Sci USA 97:9654–9658CrossRefPubMedGoogle Scholar
- 14.Okamatsu M, Sakoda Y, Kishida N, Isoda N, Kida Y (2008) Antigenic structure of the hemagglutinin of H9N2 influenza viruses. Arch Virol 83:1572–1578Google Scholar
- 18.Reed LJ, Muench H (1938) A simple method for estimating 50% endpoints. Am J Hyg 27:493–497Google Scholar
- 20.Rudneva IA, Timofeeva TA, Shilov AA, Kochergin-Nikitsky KS, Varich NL, Ilyushina NA, Gambaryan AS, Krylov PS, Kaverin NV (2007) Effect of gene constellation and postreassortment amino acid change on the phenotypic features of H5 influenza reassortants. Arch Virol 152:1139–1145CrossRefPubMedGoogle Scholar
- 21.World Health Organization Epidemic and Pandemic Alert and Response (2009) Swine flu illness in the United States and Mexico, update 2 (Online) http://www.who.int/csr/don/2009_04_26/en/index.htm