US scientists have used the common cold to develop a promising new vaccine against deadly bird flu.
It is hoped the breakthrough could provide a lifeline in the event of a human pandemic threatening millions of lives. The vaccine was made by genetically modifying an adenovirus, one of the causes of the common cold. The altered virus produced a protein that is a component of H5N1 bird flu. Mice injected with the protein were protected from death and weight loss when exposed to viruses taken from humans infected by H5N1 in 2003 and 2004. Unlike other experimental H5N1 vaccines, the new drug triggered the generation of specific immune system T-cells that helped clear the virus. The research was led by Dr Suryaprakash Sambhara, from the Centre for Disease Control and Prevention in Atlanta, Georgia, and Professor Suresh Mittal, from Purdue University in West Lafayette, Indiana. They wrote in an early online edition of The Lancetmedical journal: "This approach is a feasible vaccine strategy against existing and newly emerging viruses of highly pathogenic avian influenza to prepare against a potential pandemic. "This approach also provides a viable option for potential vaccine stockpiling for the influenza pandemic." Since 2003, a total of 160 people have been infected with H5N1 birdflu and 85 have died. Most victims have been from eastern Asia, but 12 cases and four deaths have been recorded in Turkey. So far there has been no evidence of person-to-person transmission, and most human cases have involved close contact with infected poultry. But experts fear it is only a matter of time before the virus turns into a form that can transfer between people. The devastating consequences could mirror the Spanish Flu pandemic of 1918 which killed between 20 million and 40 million people. Coping with such a catastrophe will necessitate the rapid production of vaccines adapted to different sub-strains. The conventional method of manufacturing a vaccine from viruses grown in chicken eggs takes at least six months. Scientists estimate that four billion fertilised eggs would be needed to produce enough pandemic vaccine for the 1.2 billion people at high risk around the world. An added problem is that H5N1 is highly virulent in poultry, which could impact on the availability of chicken eggs. Also, an egg-based vaccine would not be able to protect against numerous different strains of the virus.