News: 1918 Virus Matches 2009 H1N1 Strain

Science
26 March 2010  Vol 327, Issue 5973, Pages 1543-1678
http://www.sciencemag.org/current.dtl

News of the Week
Swine Flu Pandemic: What’s Old Is New: 1918 Virus Matches 2009 H1N1 Strain
Jon Cohen

The “novel” H1N1 swine influenza virus that last year caused the first human pandemic in 4 decades has one feature that is hardly novel: Its surface protein, hemagglutinin (HA)—which spikes cells and starts an infection—closely matches the HA in the H1N1 virus responsible for the 1918 pandemic. Separated by 91 years, the two strains of the highly mutable virus ought to be vastly different. This newfound similarity answers many mysteries about the 2009 pandemic, including why it largely spared the elderly. The new findings, reported online this week in Science and Science Translational Medicine, also suggest intriguing explanations for how the 1918 influenza virus has evolved since it swept across the globe in several waves, killing more than 50 million people by the winter of 1919. And the investigators are proposing provocative—some say far-fetched—vaccination strategies to preempt future pandemics. Science Express Index

Published Online March 25, 2010
Reports

Structural Basis of Preexisting Immunity to the 2009 H1N1 Pandemic Influenza Virus
Rui Xu,1, Damian C. Ekiert, Jens C. Krause, Rong Hai, James E. Crowe, Jr., Ian A. Wilson

The 2009 H1N1 swine flu is the first influenza pandemic in decades. The crystal structure of the hemagglutinin from the A/California/04/2009 H1N1 virus shows that its antigenic structure, particularly within the Sa antigenic site, is extremely similar to human H1N1 viruses circulating early in the 20th century. The co-crystal structure of the 1918 HA with 2D1, an antibody from a survivor of the 1918 Spanish flu that neutralizes both 1918 and 2009 H1N1 viruses, reveals an epitope that is conserved in both pandemic viruses. Thus, antigenic similarity between the 2009 and 1918-like viruses provides an explanation for the age-related immunity to the current influenza pandemic.

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