niman wrote:
The Kawaoka paper looked at the sequences in ferrets infected with N158D, N224K, Q226L. One ferret with high titer H5 had T318I, and that change stabilized the virus and has been discussed in detail. However, 5/6 of the sequences had another change, A242S, as described in the paper:
To determine whether additional mutations occurred in the HA of HA(N158D/N224K/Q226L)/CA04 during transmission, viral RNA was analysed from nasal washes of inoculated and contact ferrets (Fig. 4 and Supplementary Table 4). On day 5 after infection, the A242S and T318I mutations in HA were present in five (pairs 1, 3, 4, 5 and 6) and one (pair 2) of the six inoculated animals, respectively. Viruses derived from the contact animals of pair 1 on day 7 after contact had two changes in HA (K193N and A242S) (Fig. 1a), whereas those derived from the contact animals of pair 2 contained a single change in HA (T318I) (Fig. 1b), indicating that additional changes in HA occurred during the infection of ferrets with HA(N158D/N224K/Q226L)/CA04. No mutations in the remaining genes were detected in any of these viruses from nasal washes compared with the CA04 virus sequences.
Since the H5 sequence has N at position 240, A242S creates a glycosylation site at position 240, which is also created by A240T, which was also seen in the Kawaoka paper (in ferrets inoculated with T318I Supplemental table 5). A240S is present in a limited number of H5N1 sequences, including 4 in Egypt. However, A240T is common in Egypt.
Supplemental tables
http://www.nature.com/nature/journal/va ... 831-s1.pdf
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