Live-attenuated Yersinia pestis vaccines.

Plague caused by Yersinia pestis is one of the most dangerous infectious diseases. There is no ideal plague vaccine available for human use, but a number of licensed killed whole-cell and live-attenuated vaccines have been available in the past. Currently, there are a number of vaccines under development, including live-attenuated, DNA and subunit vaccines, among others. This review deals with the development of live-attenuated plague vaccines. Traditionally, live-attenuated plague vaccines have been developed by multiple passages of fully virulent Y. pestis, but they have not gained general acceptance due to safety concerns. Recent attempts to construct attenuated Y. pestis strains with specifically defined mutations have opened the door for developing new candidates for live-attenuated plague vaccines, with a proper balance between safety and protective efficacy.