This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Qin, A. Articles by Mann, B. J. Search for Related Content PubMed PubMed Citation Articles by Qin, A. Articles by Mann, B. J.

 Previous Article  |  Next Article 

Infection and Immunity, January 2009, p. 152-161, Vol. 77, No. 1
0019-9567/09/$08.00+0     doi:10.1128/IAI.01113-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Identification of an Essential Francisella tularensis subsp. tularensis Virulence Factor

Aiping Qin,¹ David W. Scott,¹ Jennifer A. Thompson,² and Barbara J. Mann^1,2*

Department of Medicine,¹ Department of Microbiology, University of Virginia, Charlottesville, Virginia 22908²

Received 5 September 2008/ Returned for modification 16 October 2008/ Accepted 22 October 2008

Francisella tularensis, the highly virulent etiologic agent of tularemia, is a low-dose intracellular pathogen that is able to escape from the phagosome and replicate in the cytosol. Although there has been progress in identifying loci involved in the pathogenicity of this organism, analysis of the genome sequence has revealed few obvious virulence factors. We previously reported isolation of an F. tularensis subsp. tularensis strain Schu S4 transposon insertion mutant with a mutation in a predicted hypothetical lipoprotein, FTT1103, that was deficient in intracellular replication in HepG2 cells. In this study, a mutant with a defined nonpolar deletion in FTT1103 was created, and its phenotype, virulence, and vaccine potential were characterized. A phagosomal integrity assay and lysosome-associated membrane protein 1 colocalization revealed that FTT1103 mutant bacteria were defective in phagosomal escape. FTT1103 mutant bacteria were maximally attenuated in the mouse model; mice survived, without visible signs of illness, challenge by more than 10¹⁰ CFU when the intranasal route was used and challenge by 10⁶ CFU when the intraperitoneal, subcutaneous, or intravenous route was used. The FTT1103 mutant bacteria exhibited dissemination defects. Mice that were infected by the intranasal route had low levels of bacteria in their livers and spleens, and these bacteria were cleared by 3 days postinfection. Mutant bacteria inoculated by the subcutaneous route failed to disseminate to the lungs. BALB/c or C57BL/6 mice that were intranasally vaccinated with 10⁸ CFU of FTT1103 mutant bacteria were protected against subsequent challenge with wild-type strain Schu S4. These experiments identified the FTT1103 protein as an essential virulence factor and also demonstrated the feasibility of creating defined attenuated vaccines based on a type A strain.

---

* Corresponding author. Mailing address: University of Virginia Health System, P.O. Box 801364, Charlottesville, VA 22908. Phone: (434) 924-9666. Fax: (434) 924-0075. E-mail: bjm2r{at}virginia.edu

Published ahead of print on 3 November 2008.

Editor: R. P. Morrison

---

Infection and Immunity, January 2009, p. 152-161, Vol. 77, No. 1
0019-9567/09/$08.00+0     doi:10.1128/IAI.01113-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Sharma, J., Li, Q., Mishra, B. B., Pena, C., Teale, J. M. (2009). Lethal pulmonary infection with Francisella novicida is associated with severe sepsis. J. Leukoc. Biol. 86: 491-504 [Abstract] [Full Text]