Divalent flagellin immunotherapy provides homologous and heterologous protection in experimental urinary tract infections in mice

• First report of prevention of UTIs by divalent flagellin.
• Non-adjuvanted flagellin subtypes afforded good protection.
• Reverted structural integrity of kidney and bladder tissue to normal by clearing bacterial load and reducing inflammation.
• Active immunization by divalent flagellin and passive immunization by anti-flagellin sera protected mice against UTI by P. aeruginosa and E. coli.

Immunotherapy employs selected prokaryotic elements which are specially targeted because of their designated important role in the pathogenicity of the microbes. Among these is the flagellin of P. aeruginosa, which plays a major role in establishment of urinary tract infections (UTIs). In this study we envisage divalent flagellin (a combination of flagellin subtypes, ‘a’ and ‘b’) as an immunotherapeutic candidate against UTIs caused by Pseudomonas aeruginosa. Flagellin proteins were isolated from P. aeruginosa strains and characterized by MALDI-TOF. Their efficacy was checked in an ascending model of UTI. Divalent flagellin (‘a’ and ‘b’) when given together (intraperitoneally, i.p.) to female LACA mice at a concentration of 5 μg each, protected mice against pyelonephritis due to P. aeruginosa strains with no bacterial load at peak day of infection. Tissue destruction was minimum, as assessed by MDA levels and renal histopathology. Divalent flagellin immunization also drastically reduced pro-inflammatory cytokine levels (TNF α and IL-1β) in renal homogenates as determined by ELISA. It also prevented UTI caused by heterologous strain Escherichia coli. Antibodies against both flagellin proteins were assessed by ELISA. Passive immunization protected mice against UTI induced by either of the strains, P. aeruginosa and E. coli. These results confirmed homologous and heterologous protection provided by divalent flagellin.