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H5N1 Recombines Away from Pandemic Vaccine
Recombinomics Commentary
May 18, 2005
>> H5N1 human isolates from Viet Nam in 2005 are somewhat antigenically heterogeneous. In particular, A/Viet Nam/JPHN3021/2005 is antigenically distinct from the 2004 reference / vaccine strains A/VN/1203/04 and A/VN/1904/04. Other 2005 H5N1 human isolates exhibit more antigenic heterogeneity than did those isolated in 2004. <<
The above commentary indicates the 2005 H5N1 isolates are rapidly evolving away from the 2004 strains being used to generate a pandemic vaccine. Producing a pandemic vaccine is more difficult than human flu because of the extreme heterogeneity in the flu gene base in Asia.
H5N1 evolves via recombination, not reassortment or random mutations. The recombination is driven by dual infections, and the diverse gene pool in Asia provides many opportunities for the genes to evolve. H5N1 is present in asymptomatic ducks, chickens, and pigs, so dual infections are common. When these dual infections involve diverse genes, evolution proceeds rapidly. Thus, the 2005 isolates are more diverse than the 2004 isolates. This diversity in Vietnam suggests similar diversity exists in Thailand and Cambodia. These changes can decrease the sensitivity of PCR tests because primers become mismatched.
A serious survey of H5N1 in people throughout Asia is long overdue. H5N1 has been rapidly evolving while agencies and governments issue press releases about false negatives and lack of reassortment.
H5N1 is ready for the 2005 pandemic.
Governments around the world are clearly asleep at the switch.
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