Due to high infectivity and potential for airborne transmission, Francisella tularensis has been designated a category A agent of bioterrorism. One disadvantage of some old vaccines is that genetic events resulting in attenuation are unknown, preventing exclusion of reversion to virulence.
Åke Forsberg of the FOI Swedish Defence Research Agency et al. have reintroduced the two genes they suspected-based on genomic studies and functional virulence studies-of causing attenuation of live vaccine strain (LVS) for this pathogen. "Functional restoration of the genes encoding surface structures (pili) or proteins resulted in a fully virulent bacterium in a mouse infection model," says Forsberg. LVS has not previously been licensed, despite extensive use in the past, because of this missing information, says Forsberg. The research could thus enable licensing, making the vaccine more widely available, he says. "Our main focus for continuing studies is to get a deeper molecular level understanding of the role these two surface components play in pathogenesis."
(E. Salomonsson, K. Kuoppa, A.-L. Forslund, C. Zingmark, I. Golovliov, A. Sjöstedt, L. Noppa, and Åke Forsberg. 2009. Reintroduction of two deleted virulence loci restores full virulence to the live vaccine strain of Francisella tularensis. Infect. Immun. 77:3424-3431.) |
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