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Paradigm Shift Intervention Monitoring
The Health Protection Agency released
four sets of H1N1 sequences at GISAID, which was followed by a paper
with phylogenetic analysis of 41 HA sequences from the current
2010/2011 outbreak. The rapid spread of H1N1 suggests the new
sequences had escaped
from the immunological response generated against last season’s
One such change was S188T, which was adjacent to receptor binding domain position 190. When H274Y was fixed in seasonal flu, A193T was in all sequences, and it was flanked by changes at positions 187, 189, and 196. Thus, S188T was expected to aid in immunological escape and was present in 22 of the 41 sequences.
However, S186P was also present in one of the four sequences released by the HPA, A/England/118/2010, raising concerns that this change would also generate immunological escape.
The phylogenetic analysis presented in the above paper indicated S186P was in 14 of the 41 sequences.
Thus, 36 of the 41 sequences in the United Kingdom had S186P or S188T, providing a mechanism for immunological escape, and the rapid spread of H1N1 in the UK.
This parallel with the spread of seasonal H1N1 in 2008/2009 increase concerns that the addition of D225G to these drivers of pandemic H1N1 will have a catastrophic effect, which is increased by the presence of D225G on two identical recombinant sequences with S188T.
More information on these two patients, as well as release of the 37 sequences published in the phylogenetic tree would be useful.