H5N1 Threat Puts Human Flu Back In Spotlight

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Anti-flu drugs

The emergence of the avian influenza virus H5N1 that is currently devastating chicken flocks in many countries and threatening to unleash a worldwide epidemic among humans has triggered a renewed interest among scientists in studying influenza A viruses, according to investigators at St. Jude Children's Research Hospital. This renewed interest could lead to new discoveries of immune system response to viruses that could lead to better drugs and vaccines, the researchers write in a review article that appears in the May issue of Nature Immunology.

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"Until recently, many immunologists were relatively uninterested in studying influenza immunity because there were already effective vaccines," said Peter Doherty, Ph.D., member of the St. Jude Department of Immunology and co-recipient of the 1996 Nobel Prize for Medicine. "The current resurgence of interest in influenza immunology reflects the threat that H5N1 could evolve into a virus that spreads easily among humans. Over the years, influenza A viruses have been one of the most important models for studying how the immune system responds to viral infections. Further study of this virus and the immune response to it will no doubt help us prepare for this latest threat."

Influenza A viruses infect a wide range of animals and cause influenza outbreaks among humans. Scientists categorize influenza A viruses according to the identity of two specific proteins on their surface, HA and NA. There are 16 known subtypes of HA (H) proteins and 9 subtypes of NA (N) proteins, which are used to name the viruses, such as H5N1. The virus uses the HA protein to attach itself to a cell it is about to infect. Newly made viruses inside infected cells use NA to escape from the cell and spread.

"Studies of influenza A led to the design of Relenza

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