Effective vaccines against highly pathogenic avian influenza H5N1 viruses are an urgent and global public-health priority. However, there are a number of problems with current vaccine manufacturing strategies. To produce a H5N1 vaccine using standard methods would involve first growing a virus strain in millions of fertilised chicken eggs and then harvesting, purifying, and killing the virus. It takes at least 6 months to make a conventional egg-derived vaccine and scientists estimate that 4 billion fertilised eggs would be needed to produce enough pandemic vaccine for 1.2 billion people worldwide at high-risk. However, in the event of a pandemic, ensuring the availability of fertilised chicken eggs would be problematic since H5N1 viruses are highly virulent in poultry. An egg-based vaccine would also not be useful for stockpiling, as it would not be able to protect against different strains of the virus. Therefore, alternative vaccine-manufacturing strategies are needed.
Suryaprakash Sambhara (The Centers for Disease Control and Prevention, Atlanta, GA, USA), Suresh Mittal (Purdue University, West Lafayette, IN, USA), and their colleagues genetically engineered an adenovirus (a common cold virus) to produce a protein called haemugglutinin subtype 5 (H5HA)--a component of the H5N1 influenza virus. The team injected one group of mice with the H5HA vaccine and another with saline as a negative control. They found that the immunised mice, despite having low or no neutralising antibodies against H5N1 viruses, were nonetheless protected from death and weight loss when infected with H5N1 viruses isolated from people in 2003 and 2004. The researchers found that unlike the conventional H5N1 vaccines, which do not activate the cellular arm of the immune system, the human adenovirus H5HA vaccine generated specific T cells (a type of white blood cell) that helped clear the virus.
Dr Sambhara and Professor Mittal state: "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."
Contact: Dr Suryaprakash Sambhara, Influenza Branch, Mail Stop G16, 1600 Clifton Road, Atlanta, Georgia, 30333, USA. sambhara@cdc.gov The Centers for Disease Control and Prevention press office T) 404 639 3286
Prof. Suresh Mittal, Veterinary Pathobiology, Purdue University, West Lafayette, IN 47907. T) 765-496-2894 mittal@purdue.edu
Purdue University, Media Relations, Susan A. Steeves T) 765 496 7481 ssteeves@purdue.edu
Journal
The Lancet