The study that has grabbed the attention of the news media over the past 48 hours, indicating that the H7 subtypes of avian flu may be adapting to human receptor cells, appears in this week's issue of PNAS (Proceedings of the National Academy of Science).
Below is the abstract from the published study, slightly reformatted for easier web reading. The entire article is available online here.
Jessica A. Belser*,, Ola Blixt, Li-Mei Chen*, Claudia Pappas*, Taronna R. Maines*, Neal Van Hoeven*, Ruben Donis*, Julia Busch, Ryan McBride, James C. Paulson, Jacqueline M. Katz*, and Terrence M. Tumpey*,
*Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333; Emory University, Atlanta, GA 30322; and Departments of Physiological Chemistry and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037
Edited by Peter Palese, Mount Sinai School of Medicine, New York, NY, and approved March 21, 2008 (received for review February 7, 2008)
Avian H7 influenza viruses from both the Eurasian and North American lineage have caused outbreaks in poultry since 2002, with confirmed human infection occurring during outbreaks in The Netherlands, British Columbia, and the United Kingdom. The majority of H7 infections have resulted in self-limiting conjunctivitis, whereas probable human-to-human transmission has been rare.
Here, we used glycan microarray technology to determine the receptor-binding preference of Eurasian and North American lineage H7 influenza viruses and their transmissibility in the ferret model. We found that highly pathogenic H7N7 viruses from The Netherlands in 2003 maintained the classic avian-binding preference for 2–3-linked sialic acids (SA) and are not readily transmissible in ferrets, as observed previously for highly pathogenic H5N1 viruses.
However, H7N3 viruses isolated from Canada in 2004 and H7N2 viruses from the northeastern United States isolated in 2002–2003 possessed an HA with increased affinity toward 2–6-linked SA, the linkage type found prominently on human tracheal epithelial cells.
We identified a low pathogenic H7N2 virus isolated from a man in New York in 2003, A/NY/107/03, which replicated efficiently in the upper respiratory tract of ferrets and was capable of transmission in this species by direct contact. These results indicate that H7 influenza viruses from the North American lineage have acquired sialic acid-binding properties that more closely resemble those of human influenza viruses and have the potential to spread to naïve animals.