In promising strategy to fight pandemic, vaccine made from survivors' blood shown to treat disease
Joseph Hall
health reporter
An international team of researchers has used antibodies derived from Vietnamese survivors of the avian flu to successfully treat and prevent the disease in mice.
And the promising and unique strategy for fighting a pandemic could be fast-tracked into human trials and provide a new tool in public health efforts to control any outbreak, according to a scientific paper published today in the Public Library of Science's online journal PloS Medicine.
After inoculating 60 mice with one of the monoclonal antibodies, 58 survived. All the mice in the control group died within 10 days. The other three antibodies made from the human blood provided "robust" protection, even 24 hours after the mice were infected.
"That was really quite remarkable because the virus actually replicates ... very rapidly in the mice," said study author Dr. Kanta Subbarao, a senior investigator with the U.S. National Institute of Allergy and Infectious Diseases in Bethesda, Md. "So we were very intrigued to see how effective treatment was after the virus was administered."
The research marks the first time human antibodies have been used to fight the H5N1 virus, which has loomed for several years as a pandemic threat. The antibody strategy has been given fast-track funding in the United Kingdom by the Welcome Trust, the world's largest medical research charity.
"It's promising because these are human antibodies and ... you can go directly from this experiment to a clinical trial," said Bhagirath Singh, a professor of microbiology at the University of Western Ontario's Schulich School of Medicine.
Avian flu has killed millions of poultry birds around the world and infected at least 306 humans since it first appeared in 1997. The World Health Organization reports that 185 people have died.
For the study, researchers took blood samples from four Vietnamese adults who were infected with avian flu between January 2004 and February 2005 and recovered.
In a process similar to one used to create a SARS vaccine, Swiss scientists extracted antibody-producing white blood cells – called memory B cells – and treated them so they produced massive amounts of antibody.
Subbarao's lab screened 11,000 samples and identified a handful that neutralized H5N1 viruses. The Swiss researchers were able to use these to tease out B cells that produced effective antibodies and created four monoclonal antibodies.
The key to the success of the passive antibody strategy depends on how much the H5N1 virus mutates over time.
Influenza viruses often change on a yearly basis to evade death by immune responses built up during previous flu outbreaks.
The Vietnamese antibodies proved effective against at least two different strains of the H5N1 virus – one that appeared in 2004, the other in 2005 – indicating they might provide ongoing protection over time.
Original Source