Identification of mechanisms for attenuation of the FSC043 mutant of Francisella tularensis SCHU S4

  1. Get@NRC: Identification of mechanisms for attenuation of the FSC043 mutant of Francisella tularensis SCHU S4 (Opens in a new window)
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Journal titleInfection and Immunity
Pages36223635; # of pages: 14
Subjectlysosome associated membrane protein 1; bacterial gene; bacterial growth; bacterial strain; bacterial virulence; bacterium mutant; cell division; cytotoxicity; deletion mutant; down regulation; Francisella tularensis; Francisella tularensis FSC043; Francisella tularensis SCHU S4; gene construct; gene expression; gene mutation; gene replication; genetic analysis; macrophage; microarray analysis; microbial attenuation; mouse; phagosome; phenotype; protein analysis; protein expression; protein localization; proteomics; Bacterial Proteins; Cell Line; Mice, Inbred C57BL; Tularemia
AbstractPreviously, we identified a spontaneous, essentially avirulent mutant, FSC043, of the highly virulent strain SCHU S4 of Francisella tularensis subsp. tularensis. We have now characterized the phenotype of the mutant and the mechanisms of its attenuation in more detail. Genetic and proteomic analyses revealed that the pdpE gene and most of the pdpC gene were very markedly downregulated and, as previously demonstrated, that the strain expressed partially deleted and fused fupA and fupB genes. FSC043 showed minimal intracellular replication and induced no cell cytotoxicity. The mutant showed delayed phagosomal escape; at 18 h, colocalization with LAMP-1 was 80%, indicating phagosomal localization, whereas the corresponding percentages for SCHU S4 and the ΔfupA mutant were <10%. However, a small subset of the FSC043-infected cells contained up to 100 bacteria with LAMP-1 colocalization of around 30%. The unusual intracellular phenotype was similar to that of the ΔpdpC and ΔpdpC ΔpdpE mutants. Complementation of FSC043 with the intact fupA and fupB genes did not affect the phenotype, whereas complementation with the pdpC and pdpE genes restored intracellular replication and led to marked virulence. Even higher virulence was observed after complementation with both double-gene constructs. After immunization with the FSC043 strain, moderate protection against respiratory challenge with the SCHU S4 strain was observed. In summary, FSC043 showed a highly unusual intracellular phenotype, and based on our findings, we hypothesize that the mutation in the pdpC gene makes an essential contribution to the phenotype.
Publication date
PublisherASM Journals
AffiliationNational Research Council Canada (NRC-CNRC); Human Health Therapeutics
Peer reviewedYes
NPARC number21272756
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Record identifier18a2ea9a-1933-4412-b735-15646ac641ca
Record created2014-12-03
Record modified2016-05-09
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