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Vietnam is one of the countries most affected by highly pathogenic H5N1 influenza A viruses. To evaluate the potential pathogenicity in mammals of H5N1 viruses isolated from humans in Vietnam, we determined the sequences of all eight genes of 22 human isolates collected between 2003 and 2008 and compared their virulence in mice. The isolates were classified into clade 1 and clade 2.3.4 and differed in pathogenicity for mice. Whilst lysine at position 627 of PB2 (PB2-627K) is a critical virulence determinant for clade 2.3.4 viruses, asparagine at position 701 of PB2 and other unknown virulence determinants appear to be involved in the high pathogenicity of clade 1 viruses, warranting further studies to determine the factors responsible for the high virulence of H5N1 viruses in mammals.
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Journal of General Virology vol. 91 , part 10, pp. 2485–2490
Supplementary Fig. S1. Map of the provinces of northern Vietnam.
Supplementary Fig. S2. Phylogenetic relationships of the PB2, PB1, PA, NP, NA, M and NS genes of H5N1 influenza viruses isolated from patients in Vietnam.
Supplementary Fig. S3. Polymerase activity of UT3040 and UT3040II.
Supplementary Table S1. Amino acid differences between UT3040 and UT3040II viruses
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