SIDEROPHORE RECEPTOR PROTEIN FROM KLEBSIELLA PNEUMONIAE AS A PROMISING IMMUNOGEN FOR SEROTYPE-INDEPENDENT THERAPEUTIC LEAD DEVELOPMENT

Abstract

Intro: Klebsiella pneumoniae causes wide range of infections including urinary tract infections, sepsis, bacteremia, pneumonia and liver abscesses. The emergence of multi drug resistance in this bacterium led to a major setback for clinical management. WHO also endorsed need for finding alternative therapy to antibiotics for the treatment of these infections. Development of vaccines and passive antibody therapy has been proven as a potent alternative to antibiotics in case of MDR, XDR and PDR Klebsiella infections. Methods: Antigen isolation, characterisation and identification through ultracentrifugation, SDS-PAGE and Triple-TOF Mass spectrometry. Cloning and expression of Fep A gene was done. Mice immunisation and challenge study with Klebsiella pneumoniae bacteria accomplished. Findings: Clinical strains of Klebsiella pneumoniae were grown in iron deficient conditions and the iron regulated outer membrane proteins were extracted and characterized through mass spectrometry for specific identification. The gene for identified protein was cloned in pET- 28a vector and expressed in E. coli. The native protein and the recombinant protein were isolated and purified and used as antigens for generation of immune response in BALB/c mice. The native protein of Klebsiella pneumoniae grown in iron deficient condition was identified as FepA (Ferrienterobactin receptor) and other siderophore receptors. This 80 kDa protein generated a significant immune response in BALB/c mice. The antiserum from mice after subsequent booster doses was collected and showed binding with FepA protein in western blot and phagocytic uptake assay of K. pneumoniae. From animal studies after bacterial challenge post immunisation in mice, signifant bacterial clearance was observed. The antiserum from mice showed binding and clearance of the Klebsiella pneumoniae bacteria in vitro and in vivo. Conclusion: The antiserum from immunised mice with FepA showed binding and clearance of the Klebsiella pneumoniae bacteria in vitro and in vivo.This study demonstrates the potential signifance of FepA as an immunogen or a therapeutic agent.