Rabies, HIV, cancer and malaria could all be prevented with pills in the future, if a new technique using specially modified viruses to deliver vaccines is adopted, according to scientists speaking today (Tuesday, 05 April 2005) at the Society for General Microbiology's 156th Meeting at Heriot-Watt University, Edinburgh.
"We can take a special type of virus which only infects bacteria, called a bacteriophage, and replace some of its DNA with vaccine DNA, and then use the phage to deliver vaccines in a highly efficient way," says Dr John March of the Moredun Research Institute, Penicuik, near Edinburgh.
A vaccine packaged in this way is cheap, simple to make, stable, and environmentally safe according to the researchers. Because the phage vaccine can be safely stored at room temperature as a dry powder, it should be possible to turn it into a pill form and deliver it as an oral vaccine. Since the phages can mass produce themselves the system would be very cheap, and easy to store and administer, making it ideal for use in the developing world to protect against diseases such as HIV/AIDS and malaria.
"We have already tested oral delivery of these vaccines, and the data suggest that they work," says Dr March. "We have successful test results from mice, rabbits and sheep - animals in which conventional DNA vaccines do not work - so we are confident that the technique will work for people. Bacteriophages have been used as medicines in eastern Europe since the 1930s to fight bacterial infections, so we have a long history of their safe use in humans, and of large scale manufacturing."
The phage vaccines have several advantages over traditional 'naked' DNA vaccines - they can contain much larger sections of DNA, triggering a more effective immune response. Because the phage vaccine is protected within a virus shell it can be targeted at specific cells in the body, and the shell stops it breaking down and becoming ineffective.