( lity to trigger strong innate and adapt...)Radiation-killed bacteria vaccine induces broad immune response in mice

"By showing that whole, irradiated bacteria can form the basis of a vaccine that elicits a strong response from both arms of the adaptive immune system, Dr. Raz and his colleagues have opened the possibility of making a variety of bacterial vaccines that combine the best features of both killed-agent and live, attenuated vaccines," says NIAID Director Anthony S. Fauci, M.D.

Earlier research in Dr. Raz's laboratory had shown that irradiated probiotics (bacteria that are beneficial to health) retain the ability to trigger innate immune system responses via proteins called toll-like-receptors. Based on that observation, says Dr. Raz, "we hypothesized that a vaccine made from whole, irradiated bacteria would retain the properties needed to evoke a broad immune response and result in a superior vaccine compared with other methods of killing the pathogen."

The investigators inactivated Listeria with lethal doses of gamma radiation and then vaccinated a group of 10 mice twice with the irradiated bacteria. Another group of 10 mice received two inoculations with heat-killed Listeria, while a third group of 10 received no vaccine. Twenty-eight days after the first vaccinations, all the mice were infected with a large dose of live Listeria (four times the amount required to kill 50 percent of infected unvaccinated animals). All the unvaccinated mice and all the mice vaccinated with heat-killed Listeria died, but 80 percent of the mice vaccinated with the irradiated bacteria survived. Further experiments showed that protection conferred by irradiated Listeria bacteria lasted for at least 12 months, indicating that the vaccine promoted the development of a "memory" T cell response.

Consistent with their earlier experiments with irradiated probiotics, Dr. Raz and his colleagues also found that irradiated Listeria retained the ability to stimulate innate immune responses via tol
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Source:NIH/National Institute of Allergy and Infectious Diseases