[Characterization of structure and antigenic activity of lipopolysaccharides of genus Francisella]

Wild-type representatives of Francisella genus (F. tularensis, F. novicida, F. novicida-like, and F. philomiragia) produce S-type lipopolysaccharides (LPS) possessing different antigenic activity and common antigenic determinants in the core oligosaccharide. Electrophoretic analysis showed that F. philomiragia produced S-LPS containing two major molecular components with minor fractions between them, whereas S-LPS of F. tularensis, F. novicida, and F. novicida-like are characterized by the typical frequency distribution of molecules. A characteristic feature of Francisella LPS was the ability to form the dominant molecular components with similar electrophoretic mobility of major fractions of the original F. philomiragia LPS upon long storage in water solution. Natural virulent F. tularensis strains produce at least two types of S-LPS. Polysaccharide chains of type I S-LPS possess O-species-specific antigens, whereas the polysaccharide part of type II S-LPS has nonspecific antigenic epitopes. A decrease of F. tularensis virulence can be associated with impaired production of both S-LPS types or loss of S-LPS with O-species-specific antigenic activity.