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Novel H5N1Receptor Binding Domains in Northern Vietnam
Recombinomics Commentary
May 18, 2005
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The HA gene of viruses isolated from humans in Viet Nam in the first 3 months of 2005 showed several amino acid changes relative to 2004 viruses. None of the changes in the HA were common to all of the 2005 viruses analysed so far. However, the most commonly observed changes are located close to the receptor binding site and could potentially modulate receptor binding specificity. <<
The above commentary indicates H5N1 may be changing its receptor binding domain to achieve more efficient human-to-human transmission. It is not swapping its H5 for a human H3. It is changing H5 to recognize human receptors. Thus, it will still be H5 and immunity in humans will be limited, yet it will have more efficient human-to-human transmission. These changes are generated via additional recombination and the high density of H5N1 in asymptomatic ducks, chickens, and pigs provides many opportunities to mix and match pieces of genes via recombination.
The gene pool in Vietnam is extremely unstable, which leads to dual infections, recombination, and the multiple amino acid changes described above. The genetic instability leads to more dual infections and more recombination. These are not random mutations, and reassortment with human genes has still not been found for H5N1.
H5N1 genes are changing, not shuffling, and the changes include the recptor binding domain, leading to more efficient human-to-human transmission.
Clearly only H5N1 is prepared for the 2005 bird flu pandemic.
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