Letter raises possibility of human-adapted H5N1 in Canada case
An H5N1 avian flu virus that killed a Canadian woman in January had two uncommon mutations that may have helped increase its ability to bind to human cells, researchers from Singapore and Canada reported yesterday in a letter in Emerging Infectious Diseases.
The woman, who had visited China before her illness in December, had neurologic symptoms and no known contact with poultry. She remains Canada’s only H5N1 patient.
The investigators note two previously reported mutations, R189K and G221R, in the hemagglutinin protein in the virus isolated from the patient. They write that both mutations are found in the immediate receptor-binding pocket, and G225R has been known to change specificity of an H3N2 virus toward human erythrocytes. The authors note that the two receptor-binding pocket mutations were not seen in the most closely related Asian H5N1 sequences.
They write, “Our results suggest that G225R could incur a relative predicted increase in binding to the human-like receptors. . . . The role of R193K is less clear with a slight predicted tendency of favoring avian-like receptors.”