Open AccessConstruction and Characterization of an Attenuated Purine Auxotroph in aFrancisella tularensisLive Vaccine Strain
Author(s) -
Roger D. Pechous,
Jean Celli,
Renee M. Penoske,
Stanley F. Hayes,
Dara W. Frank,
Thomas C. Zahrt
Publication year - 2006
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.00666-06
Subject(s) - francisella tularensis , tularemia , biology , attenuated vaccine , virulence , microbiology and biotechnology , francisella , virology , mutant , phagolysosome , auxotrophy , phagocytosis , phagosome , genetics , gene
Francisella tularensis is a facultative intracellular pathogen and is the etiological agent of tularemia. It is capable of escaping from thephagosome, replicating to high numbers in the cytosol, and inducingapoptosis in macrophages of a variety of hosts.F. tularensis has received significant attention recently due to its potential use asa bioweapon. Currently, there is no licensed vaccine againstF.tularensis , although a partially protective live vaccine strain(LVS) that is attenuated in humans but remains fully virulent for micewas previously developed. AnF. tularensis LVS mutant deletedin thepurMCD purine biosynthetic locus was constructed andpartially characterized by using an allelic exchange strategy. TheF. tularensis LVS ΔpurMCD mutant wasauxotrophic for purines when grown in defined medium and exhibitedsignificant attenuation in virulence when assayed in murine macrophagesin vitro or in BALB/c mice. Growth and virulence defects werecomplemented by the addition of the purine precursor hypoxanthine or byintroduction ofpurMCDN intrans . TheF.tularensis LVS ΔpurMCD mutant escaped from thephagosome but failed to replicate in the cytosol or induce apoptoticand cytopathic responses in infected cells. Importantly, micevaccinated with a low dose of theF. tularensis LVSΔpurMCD mutant were fully protected against subsequentlethal challenge with the LVS parental strain. Collectively, theseresults suggest thatF. tularensis mutants deleted in thepurMCD biosynthetic locus exhibit characteristics that maywarrant further investigation of their use as potential live vaccinecandidates.