H1N1 virus lacks Spanish flu’s killer protein

Molecule responsible for extent of 1918 pandemic is missing in today’s swine variant

BOSTON — The H1N1 swine flu just doesn’t have what it takes to be a real killer, a new study of the 1918 Spanish flu suggests.

Scientists have been studying the 1918 Spanish flu virus to find out what made it so deadly. The virus caused a pandemic that killed 20 million to 40 million people — making it one of the most devastating epidemics in history.

The Spanish flu virus had a killer combination of surface proteins called neuraminidase (the N in H1N1) and hemagglutinin (the H in H1N1), and another protein called PB1-F2, says Peter Palese, a virologist at Mount Sinai School of Medicine in New York City. The combination of those three proteins made the virus a million times more virulent than an average seasonal influenza virus, he and his colleagues found.

While the two surface proteins are important, it’s really PB1-F2 that gave the Spanish flu its punch, Palese told scientists gathered June 14 for Genetics 2010: Model Organisms to Human Biology, a meeting of the Genetics Society of America. Now, he and his colleagues have discovered that the viral protein prevents the body from making an important antiviral compound called interferon. Without interferon to hold it back, the virus is able to replicate quickly and completely overwhelm the body’s defenses by three days after infection, Palese reported.

Other vicious pandemic influenza strains, such as those of 1957 and 1968, also possessed PB1-F2. But the 2009 H1N1 swine flu virus lacks the protein. “It’s telling us that this virus is not as virulent as other pandemic influenza viruses,” Palese says.