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Commentary
All Three H7N9
China Cases Have N9 Deletion
Recombinomics
Commentary 03:00
April 1, 2013
The sequences have much in common with the initial H5N1 cases in Hong Kong in 1997. The internal genes are most closely related to Eurasian H9N2 sequences, which was also seen in the 1997 H5N1 which had internal genes closely related to H9N2 and H6N1 wild bird isolates. Similarly, the cases have PB2 E627K which was also seen for a subset of the Hong Kong cases.
A similarity with the H5N1 that emerged in late 2003 is a deletion on the NA stalk. For H5N1, there was a 60 BP deletion. All three of the 2013 H7N9 sequences have a 15 BP deletion beginning at position 205. However, the HA cleavage site for the H7N9 cases has two basic amino acids, while the 1997 and 2003 H5N1 had seven basic amino acid. Thus, the H7M9 may not be as lethal to poultry as H5N1, but for humans two of the three confirmed cases have died, and a third case is in critical condition.
Although all three human H7N9 are closely related to each other, Shanghai/1/2013 is distinct from Shanghai/2/2013 and Anhui/1/2013, which are more closely related to each other. The H7 is most closely related to H7N3 isolates, while the N9 is most closely related to H11N9. However, these bird isolates do not have a PB2 with E627K or a 15 BP deletion in the N9 stalk.
These adaptations as well as the novel constellation of genes, raise serious pandemic concerns.
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