Key discovery in bird flu fight
The deadly bird flu virus may have a remedy, according to an international study led by a mainland scientist.
Professor Paul Zhou, a researcher with the Institut Pasteur of Shanghai under the Chinese Academy of Sciences and team leader of the study, said yesterday that they had found an antibody that could 'neutralise' almost every known variation of the H5N1 virus - and probably future mutations.
Their paper was published in the Journal of Virology, an international, peer-reviewed journal, this month.
Microbiologist and bird flu expert Professor Guan Yi, from the University of Hong Kong, said it was very good academic work but whether the findings would translate into a clinically effective and commercially viable vaccine remained uncertain.
Zhou said the antibody was developed by his PhD student Hu Hongxing from the blood samples of a H5N1 patient in Shenzhen who recovered miraculously from the brink of death after receiving an injection of blood plasma from an immune Anhui patient in 2006.
The hospital in Shenzhen distributed the blood samples to some research institutes in the hope that scientists could develop antibodies for the virus, which has killed about half of those infected by it.
But to develop the antibodies, researchers needed to build tens of thousands of culture wells, find out which contained effective antibodies, study their nature and verify the results. That had been a daunting challenge for scientists, Zhou said.
'It's like searching for a needle at the bottom of the Pacific,' he said.
A complicating factor was that the culture wells were only good for a few days' study. If that 'window' was missed, important clues would be lost in the chaos of overgrown cells.
Zhou's team developed a unique screening method that enabled them to study tens of thousands of candidates in a few days. In the course of five years' hard work they discovered several promising antibodies.
One of them, 65C6, caught the researchers' attention because it targeted a specific location on the globular head of a viral strain that had previously been ignored by the scientific community.
The targeted location is very 'conservative' in H5N1 viruses, meaning it can be found on almost every subspecies and it is highly resistant to changes such as mutation. 'The conservative nature of the target implies that the antibody can neutralise known subspecies of the virus and its future mutations,' Zhou said.
Experiments on mice showed that the antibody had 'therapeutic efficacy against highly pathogenic avian influenza H5N1 viruses', the paper said. The only exception was a variation called 'subclade 7.2', which had been isolated from birds, but not humans.
The research was funded by the French Health Ministry, the National Natural Science Foundation of China and the Li Ka Shing Foundation in Hong Kong, among others.
Prominent British virologist Sir John Skehel and Professor Vincent Deubel, from Institut Pasteur in Cambodia, were the co-authors of the paper. Professor Zhang Linqi of Tsinghua University and Professor Zhou Boping of Shenzhen Third Hospital also contributed to the research.
Guan said the research was of high quality and might lead to more useful discoveries but the virus strains used to test the antibody were a bit outdated, with the newest from 2008. 'At the University of Hong Kong we have isolated new strains that appeared in 2010 and 2011. It is unknown whether the antibody would be effective on the newest subspecies in the field,' he said.
'Without such knowledge, drug companies may feel reluctant to take the results to clinical trials and commercial production.'
Zhou said there were several bird flu vaccines on the market but they all targeted specific variations of the virus. 'Our antibody can be used to develop a pan-vaccine,' he said. 'And medicines that cure infected patients.'
The global death toll from avian influenza since 2003, according to the World Health Organisation