RT Journal Article SR Electronic(1) A1 Hiromoto, Yasuaki A1 Yamazaki, Yoshinao A1 Fukushima, Tatsunobu A1 Saito, Takehiko A1 Lindstrom, Stephen E. A1 Omoe, Katsuhiko A1 Nerome, Reiko A1 Lim, Wilina A1 Sugita, Shigeo A1 Nerome, Kuniaki YR 2000 T1 Evolutionary characterization of the six internal genes of H5N1 human influenza A virus JF Journal of General Virology, VO 81 IS 5 SP 1293 OP 1303 DO https://doi.org/10.1099/0022-1317-81-5-1293 PB Microbiology Society, SN 1465-2099, AB The entire nucleotide sequences of all six internal genes of six human H5N1 influenza A viruses isolated in Hong Kong in 1997 were analysed in detail from a phylogenetic point of view and compared with the evolutionary patterns of the haemagglutinin and neuraminidase genes. Despite being isolated within a single year in the same geographical location, human H5N1 viruses were characterized by a variety of amino acid substitutions in the ribonucleoprotein complex [PB2, PB1, PA and nucleoprotein (NP)] as well as the matrix (M) proteins 1 and 2 and nonstructural (NS) proteins 1 and 2. The presence of previously reported amino acid sequences specific for human strains was confirmed in the PB2, PA, NP and M2 proteins. Nucleotide and amino acid sequence identities of the six internal genes of H5N1 viruses examined here were separated into at least two variant groups. In agreement with the above result, phylogenetic trees of the six internal genes of human H5N1 viruses were generally composed of two minor clades. Additionally, variable dendrogram topologies suggested that reassortment among viruses contributed further to the genetic variability of these viruses. As a result, it became clear that human H5N1 viruses are characterized by divergent gene constellations, suggesting the possible occurrence of genetic reassortment between viruses of the two evolutionary lineages., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-81-5-1293