Vaccines against Francisella tularensis.

Francisella tularensis is one of the most pathogenic pathogens known, especially when disseminated as a small particle aerosol. Because of this, it was developed into a biological warfare agent by several states during the 20th century. Nowadays, concerns remain about the potential of this pathogen to cause widespread disease, tularemia, in the hands of terrorists. This has resurrected interest in methods to combat it. This article reviews the current status of vaccine development efforts against tularemia. To date most of our understanding of tularemia vaccine efficacy has been derived from the clinical and experimental use of a pragmatically attenuated live vaccine strain of F. tularensis subspecies holarctica. However, this vaccine which has been in existence for more than 50 years is still beset by regulatory issues that continue to hamper its licensure. These issues and possible solutions are highlighted, along with more modern molecular approaches to vaccine development against this highly virulent pathogen.