Design and Properties of the Francisella tularensis Strain 15 NIIEG without the sodC Gene

The aim of the study was to create and study the immunogenic properties of Francisella tularensis strain 15 NIIEG without the sodC gene encoding CuZn-dependent superoxide dismutase. Materials and methods. Deletion of the sodC gene from the chromosome of the tularemia microbe was performed applying the allelic exchange method using the suicide plasmid vector pGM5. The modified chromosome fragment without the structural part of the sodC gene was constructed by combining amplicons synthesized via PCR using two pairs of primers. Electroporation was used to transfer plasmids into Escherichia coli and F. tularensis bacteria. BALB/c mice were used for immunization and infection. To assess the reactogenicity of the strains for mice, the average weight of animals in groups was determined. Results and discussion. The allelic exchange method was used to create the F. tularensis 15ΔsodC strain, in the chromosome of which a 545 bp fragment with the structural part of the sodC gene was missing. This strain did not differ in virulence and reactogenicity from the original strain 15 NIIEG, but mice immunized with the deleted version of the vaccine strain more easily tolerated the experimental infection caused by the natural strain F. tularensis subsp. mediasiatica A-678. It has been suggested that deletion of the sodC gene may improve the immunogenic properties of the tularemia microbe strain in the targeted design of a promising candidate for the creation of a modern tularemia vaccine with reduced reactogenicity.