• Vaccine Name: sodB(Ft)
• Target Pathogen: Francisella tularensis
• Target Disease: Tularemia
• Product Name: LVS sodB mutant
• Vaccine Ontology ID: VO_0000263
• Type: Live Attenuated
• SodB from F. tularensis SCHU S4 gene engineering:
  • Type: Protein
  • Description:
  • Detailed Gene Information: Click Here.
• Preparation: sodBFt is made by amplifying a region of the sodB gene by PCR. The full-length sodB gene is also amplified. These amplified fragments are cloned separately into a PCR cloning vector and excised by digestion with restriction enzymes. The digested fragments are ligated simultaneously to an XbaI/SalI-digested pPV shuttle vector to yield pPV-sodB. The PstI site upstream of the start codon is used as a marker for screening of mutant colonies. pPV-sodB is then transformed in Escherichia coli S17-1 and transferred into F. tularensis LVS via conjugation. The mutants are selected on modified chocolate agar plates supplemented with Isovitalex, L-cysteine hydrochloride, 1% hemoglobin, 2 µg/ml chloramphenicol, and 100 µg/ml polymyxin B. Colonies obtained on the chloramphenicol plates following the first recombination event are analyzed by PCR, followed by the digestion of PCR products with PstI enzyme. The positive mutant colonies are selected for a second recombination event by plating on medium containing 5% sucrose. Chloramphenicol sensitivity and sucrose resistance following the second recombination event are confirmed by PCR and PstI digestion of the amplified products. The positive mutant clone is referred to as sodBFt (Bakshi et al., 2006).
• Virulence: sodB(Ft) has increased sensitivity to paraquat and hydrogen peroxide (H₂O2), the redox cycling compounds, as well as with reduced virulence in both C57BL/6 and BALB/c mice (Bakshi et al., 2006).
• Description: sodBFt is a live vaccine strain mutant of Francisella tularensis with reduced Fe-superoxide dismutase gene expression (Bakshi et al., 2006).

Mouse Response

• Host Strain: C57BL/6, BALB/c
• Vaccination Protocol: Mice were immunized i.n. with 5 × 10^3 CFU of LVS or sodBFt in a volume of 20 μl PBS (10 μl/nare). Unvaccinated mice, which served as a control, received an equal volume of PBS (Bakshi et al., 2008).
• Persistence: (Bakshi et al., 2006)
• Side Effects: None were noted (Bakshi et al., 2006).
• Challenge Protocol: Mice immunized with 5 × 10^3 CFU of either LVS or sodBFt were challenged i.n. with 1 × 10^1 CFU (10LD100) of SchuS4 on day 21 post-immunization (Bakshi et al., 2008).
• Efficacy: sodBFt vaccinated C57BL/6 mice not only had a significantly extended MTD (median time to death) as compared to LVS vaccinated or unvaccinated mice, but, 40% (4/10) of the sodBFt vaccinated mice survived the challenge. All naïve C57BL/6 mice challenged with a similar dose of SchuS4 strain succumbed to infection within 6–8 days post-challenge (Bakshi et al., 2008).