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Commentary
Avian Genes In
Clade 2.3.2.1 H5N1 Guangdong China Isolate
Recombinomics
Commentary 22:15
June 6, 2012
The above comments name the sub-clade of the latest human H5N1 case from China, but fail to describe H5 changes that are associated with adaptation to humans, such as those described in recent and upcoming H5N1 transmission in ferrets. The two published papers included gene segments that were not avian, but such acquisitions have not been reported previously in H5N1 isolates from Asia. The closest example of a natural H5N1 isolates with non-avian genes was the PB2 gene from a chicken in Qalubiya, Egypt, A/chicken/Egypt/Q1182/2010, which had recombined sequences largely from seasonal H1N1 and H1N1pdm09.
The recent transmission study by Kawaoka, published in Nature, placed a clade 1 H5 on an H1N1pdm09 genetic background and obtained droplet transmission in a subset of ferrets, while Donis obtained similar transmission with an H5 placed on a clade 1 genetic background as well as an N2 from seasonal H3N2.
However, the Kawaoka studies identified an initial H5 change N158D in a subset of the ferrets, which was also likely in similar studies by Fouchier which will soon be published in Science. As noted, N158D and associated loss of the glycosylation at position 160, is widespread in clade 2.2 in the Middle East. However, N158D is also widespread in wild bird clade 2.3.2.1 sequences, including the published sequence from the prior case in Guangdong, A/Shenzhen/1/2011, from late 2011.
Those sequences also had receptor binding domain changes V223I and M230I, which have been fixed in clade 2.3.2.1.
Therefore, release of sequences from the case described above would be useful.
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