Swine Flu Update
by ilene - January 12th, 2010 12:32 am
By Ilene
Previous series of swine flu updates by me here.
Transmission of Fatal H1N1 D225G/N Accelerates Concerns
Courtesy of Dr. Henry Niman, Recombinomics Commentary
Recently released H1N1 HA sequences have significantly accelerated pandemic concerns. These sequences have either D225G, D225N, or both and produce a case fatality rate at or near 100% in many countries….
By the 100% fatality rate, Dr. Niman means that they are finding these changes in the tested fatal cases in some countries. Keep in mind, these are small numbers of cases. It does not mean that all cases with these changes prove fatal. It might be more clear to say a large portion of the fatal cases show these changes in the infecting viruses.
[the] transmission and expansion of these fatal sequences in eastern Europe, including Russia have increased concerns, as has the "low reactor" status as determined by Mill Hill for a tested Ukraine sequence.
Some of the earliest sequences with D225G were in the United States last spring and were generally mild. However, initial cases in the US were generally mild, which may have reflected low viral loads infecting a naïve population…
"Low reactors" status means that the virus is not triggering the immune response expected due to changes in the structure of certain viral proteins (here, the influenza hemagglutinin proteins). Immune responses target specific proteins and the target proteins’ structure is critical to the immune response. Not all changes in a protein will greatly reduce its immunogenicity (ability to stimulate the immune response) but certain changes will. The change from the wild-type (common) HA protein to the HA protein with the D225G marker appears to have this adverse effect--i.e., the altered viruses will not provoke the stronger immune response generated in response to the wild-type virus and/or the swine flu vaccine.
These observations are cause for concern, not alarm. The changes in the H1N1 virus are natural and predictable; Dr. Niman predicted these changes would occur.
There already was interest in position 225 for a number of reasons. D225N was in seasonal H3N2 and linked to the fixing [establishment of widespread] of adamantine resistance (S31N), while D225G was in 1918 and 1919 samples and linked to a change in receptor binding domain specificities which would target subsets of cells in the lung. In addition, the polymorphism [genetic change] was jumping from one genetic background to