Arizona State University scientists engineer bacterial vaccine delivery system

Arizona State University scientists have successfully engineered a strain of Salmonella bacteria capable of acting as a delivery system for vaccine antigens.

The ASU team used the bacteria to protect mice against a lethal influenza strain, but they believe the approach is adaptable enough to be used against many different pathogens, according to

"The technology that we're describing in this paper can be used to develop a vaccine against any virus, any parasite, any fungus, whereas this was never possible before the development of recombinant attenuated bacterial strains like those produced in our lab," Dr. Roy Curtiss, the team's leader, said.

Researchers have sought to use bacteria as a delivery mechanism for vaccines over many years. Success remained elusive because the bacteria generally used to carry the antigen die quickly in the human body before a robust immune response develops.

Most disease causing bacteria, however, have adapted to survive in even the most hostile human regions, such as the mouth, nose and gut. They also produce a rapid immune response. The ASU scientists were able to engineer a form of Salmonella that is too weak to cause illness and able to survive for a time in the host.

The engineered Salmonella has been modified in such a way that it will self-destruct after a few generations, a critical safety feature that keeps the bacteria from proliferating out of control. To create the strain, Curtiss and his colleagues modified the bacteria so that it can only survive by consuming a non-naturally occurring sugar. When the sugar runs out, the bacteria essentially implode.

"Now we have the opportunity to produce vaccines against such pathogens," Wei Kong, an ASU researcher said. "Further, the technique permits large quantities of DNA vaccine to be produced rapidly at low cost, freeze-dried and stockpiled to be used when needed."