• Vaccine Name: FSC043
• Target Pathogen: Francisella tularensis
• Target Disease: Tularemia
• Vaccine Ontology ID: VO_0000339
• Type: Live Attenuated
• Preparation: Strain FSC043 is a spontaneous mutant of the SCHU S4 strain (Twine et al., 2005).
• Virulence: Attenuated (Twine et al., 2005).
• Description: FSC043 is a spontaneous mutant of strain SCHU S4 of Francisella tularensis (Twine et al., 2005).

Mouse Response

• Host Strain: BALB/c
• Persistence: To examine the relative virulence of LVS and FSC043, BALB/c mice were challenged i.d. with CFU of one or other strain and then killed on day 4 of infection, and bacterial burdens in the skin, liver, and spleen were determined. By this time, LVS was present at 100-fold-higher levels than FSC043 in the skin and liver and 20-fold-higher levels in the spleen. The BALB/c mice that were intradermally inoculated LVS showed overt signs of infection before recovering, whereas the mice inoculated with FSC043 remained healthy. When inoculated intravenously, FSC043 grew less well than virulent type A or B strains or LVS in the livers, spleens, and lungs of mice (Twine et al., 2005).
• Side Effects: Destruction of skin and inflammation was observed at the site of inoculation of FSC043 (Twine et al., 2005).
• Challenge Protocol: FSC033 was used as the challenge strain to assess the efficacy of the various live vaccines employed. For aerosol exposure, thawed bacteria were diluted in Mueller-Hinton broth; for intradermal inoculations, stocks of the strains were diluted in sterile saline. Intradermal inocula were injected into a fold of skin in the shaved mid-belly, and the blister that formed was circumscribed with indelible marker (Twine et al., 2005).
• Efficacy: All immunized mice survived and were challenged 77 days later intradermally or by aerosol with type A strain FSC033. Immunization of BALB/c mice with LVS leads to excellent protection against intradermal challenge but only weak protection against low-dose aerosol challenge. The FSC043 immunization afforded a similar degree of protection to LVS against intradermal challenge and somewhat better protection against aerosol challenge (Twine et al., 2005).