Dirty way to skip jabs

Ready-to-eat sachets of genetically engineered soil bacteria may soon provide an easy and cheap way of vaccinating against some diseases, research suggests.

Researchers at London University's Royal Holloway and Bedford New College are about to start animal trials of new oral vaccines that they hope may provide "trauma-free" vaccine delivery for the future.

The researchers, led by biochemist Simon Cutting, are focusing their attentions on a common bacterium, Bacillus subtilis, which is found in the soil. It forms robust, heat-stable spores that can survive in the human stomach and that can be engineered to deliver antigens.

Dr Cuttingsaid that most previous attempts to produce effective oral vaccines have failed. "The problem has always been that if you eat the vaccine it is destroyed within the stomach," he explains. "There are some cases, such as polio, where it survives, but many when that is not the case."

The spores produced by Bacillus subtilis are so hardy that they should last dozens of years even in the most hostile of environments, Dr Cutting suggests. "This bacterium is not a pathogen," he says. "In fact, the spores are completely harmless. The bacteria are already sold over the counter as a probiotic in many countries. Once in the gut it will germinate. It does not know it is not in its normal soil habitat."

Dr Cutting's team, which is funded by the Wellcome Trust, has managed to genetically engineer the bacterium by fusing it with antigenic genes they want it to express. These include HIV and tetanus genes. When the bacteria enter the gut, they will express antigens of these diseases.

Now the search is on to see if immune responses to these diseases are produced in animals fed with these novel vaccines.