Structural changes reveal bird flu pandemic potential
15 November 2006
As the H5N1 strain of bird flu has spread from Asia, across parts of Europe and into Africa, scientists at the MRC’s National Institute for Medical Research have been collaborating with researchers in Japan to figure out the structural changes in the virus that have allowed some strains to spread from poultry to people.
Usually if a flu virus has an H5 component it only infects birds; it can infect humans but it is difficult for it to pass from person to person. This means a change in the H5 molecule on the surface of a bird flu virus is needed for it to be able to multiply effectively in a human nose and acquire the potential to spread and cause a pandemic.
In a paper published today in Nature, the Japanese and MRC collaborators reveal changes in H5 that allow strains of the virus to recognise human as well as bird cells. The most effective mutations were at amino acid positions 182 and 192.The research teams looked at strains of H5N1 that had killed people in Thailand, Vietnam and Cambodia and identified these amino acid changes as possible useful markers in assessing changes in the pandemic potential of circulating H5N1 viruses.
One of the scientists who took part in the research at NIMR, Dr Steve Gamblin said:
‘‘Since 2001 we have determined the 3-dimensional structures of H5 molecules from viruses that have infected birds and humans. We analysed their receptor binding properties with a view to understanding the influence of mutations on the ability of the viruses to pass from human to human. Together with analysis of N1, these studies are an integral part of H5N1 surveillance at NIMR. Our studies of the 3-dimensional structure of N1 are aimed at explaining drug resistance and the development of additional drug candidates.’’
The Director of the World Influenza Centre at NIMR, Dr Alan Hay said:
‘‘The work at NIMR on determining the protein structures of the H5 component of these virus strains provides the basis for understanding their potential to infect people. Details of the mutant structures reveal a virus’s capacity, firstly to infect a person, and secondly, whether changes during infection of one person might increase its capacity to spread to another. Analysing the effects of these changes is a valuable tool in H5N1 influenza surveillance to gain a better understanding of the potential of H5N1 viruses to cause a pandemic.’’
Original reference: Haemagglutinin mutations responsible for the binding of H5N1 influenza A viruses to human-type receptors. Published in Nature on 16 November 2006.
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