Paradigm Shift Intervention Monitoring
twitter
Live feed of underlying pandemic map data here
Commentary
Receptor Binding
Domain Changes in Texas
Recombinomics
Commentary 10:55
December 14, 2009
Although H274Y has been detected recently in Texas, and the Texas sequences are the same sub-clade as multiple sequences from the Houston or Harris County area, there were no examples of H274Y in the 137 NA sequences, confirming that requirement of most isolates in the spring of Tamiflu exposure to select for a sub-clade circulating below detection limits.
Similarly, detection of receptor binding domain changes were also rare. In the spring there were examples of isolates with D225G in Texas and California, and in some cases the samples were mixtures, such as the vaccine target, California/7. However, only one of the 137 HA sequences, A/Texas/42291877/2009, had D225G (as a mixed signal). Similarly, only one sequence had D225N. A/Texas/43132503/2009 and three sequences had D225E (A/Texas/45061755/2009, A/Texas/45061670/2009, A/Texas/45034157/2009).
These data support sequences by others which shows that the receptor binding domain changes are rarely detected, even in areas where it was detected shortly after swine H1N1 jumped to humans. However, these detection issues may be related in part to receptor binding specificities and such sequences may be more prevalent in the lower respiratory tract. Similarly the association with fatal cases has been more prevalent in the summer and fall, which may be linked to viral load. In the spring H1N1 was entering the human population, and low levels of virus may have been able to infect the naïve population. Increased immunity would lead to selection of higher levels of virus, which may have contributed to the more frequent detection in fatal cases.
Of recent concern has been the association of D225G with H274Y which has been reported in France and the United States. Increase surveillance, including samples from infected organs in fatal cases, would be useful.
.
Media Links
Recombinomics
Presentations
Recombinomics
Publications
Recombinomics
Paper
at Nature Precedings