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- Golovlev, Igor, et al.
(author)
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A Delta clpB Mutant of Francisella tularensis Subspecies holarctica Strain, FSC200, Is a More Effective Live Vaccine than F. tularensis LVS in a Mouse Respiratory Challenge Model of Tularemia
- 2013
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In: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:11, s. e78671-
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Journal article (peer-reviewed)abstract
- Francisella tularensis subsp. tularensis is a highly virulent pathogen for humans especially if inhaled. Consequently, it is considered to be a potential biothreat agent. An experimental vaccine, F. tularensis live vaccine strain, derived from the less virulent subsp. holarctica, was developed more than 50 years ago, but remains unlicensed. Previously, we developed a novel live vaccine strain, by deleting the chaperonin clpB gene from F. tularensis subsp. tularensis strain, SCHU S4. SCHU S4 Delta clpB was less virulent for mice than LVS and a more effective vaccine against respiratory challenge with wild type SCHU S4. In the current study, we were interested to determine whether a similar mutant on the less virulent subsp. holarctica background would also outperform LVS in terms of safety and efficacy. To this end, clpB was deleted from clinical holarctica strain, FSC200. FSC200 Delta clpB had a significantly higher intranasal LD50 than LVS for BALB/c mice, but replicated to higher numbers at foci of infection after dermal inoculation. Moreover, FSC200 Delta clpB killed SCID mice more rapidly than LVS. However, dermal vaccination of BALB/c mice with the former versus the latter induced greater protection against respiratory challenge with SCHU S4. This increased efficacy was associated with enhanced production of pulmonary IL-17 after SCHU S4 challenge.
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| 2. |
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| 3. |
- Lindgren, Marie, et al.
(author)
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Identification of Mechanisms for Attenuation of the FSC043 Mutant of Francisella tularensis SCHU S4
- 2014
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In: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 82:9, s. 3622-3635
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Journal article (peer-reviewed)abstract
- Previously, 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 Delta fupA 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 Delta pdpC and Delta pdpC Delta pdpE 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.
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| 4. |
- Twine, Susan M, et al.
(author)
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Roles for wbtC, wbtI, and kdtA genes in lipopolysaccharide biosynthesis, protein glycosylation, virulence, and immunogenicity in Francisella tularensis strain SCHU S4
- 2012
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In: Pathogens. - : MDPI. - 2076-0817. ; 1:1, s. 12-29
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Journal article (peer-reviewed)abstract
- Using a strategy of gene deletion mutagenesis, we have examined the roles of genes putatively involved in lipopolysaccharide biosynthesis in the virulent facultative intracellular bacterial pathogen, Francisella tularensis subspecies tularensis, strain SCHU S4 in LPS biosynthesis, protein glycosylation, virulence and immunogenicity. One mutant, ∆wbtI, did not elaborate a long chain O-polysaccharide (OPS), was completely avirulent for mice, and failed to induce a protective immune response against challenge with wild type bacteria. Another mutant, ∆wbtC, produced a long chain OPS with altered chemical and electrophoretic characteristics. This mutant showed markedly reduced glycosylation of several known glycoproteins. Additionally this mutant was highly attenuated, and elicited a protective immune response against systemic, but not respiratory challenge with wild type SCHU S4. A third mutant, ∆kdtA, produced an unconjugated long chain OPS, lacking a detectable core structure, and which was not obviously expressed at the surface. It was avirulent and elicited partial protection against systemic challenge only.
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