Abstract
Objectives: Pseudomonas aeruginosa is a notorious bacterial pathogen that can cause a variety of infections with high morbidity and mortality. The increasing multi-drug resistance of this pathogen makes it urgent to develop an effective vaccine. This study aimed at evaluation of the immunoadjuvant effect of flagellin (FliC) of Salmonella enterica and incomplete Freund’s adjuvant (IFA) on the protective vaccine efficacy of P. aeruginosa recombinant iron acquisition protein (HitA). Methods: In this work, recombinant HitA, FliC and fused FliC-F-HitA proteins were expressed in Escherichia coli after cloning their respective genes into pQE31 plasmid vector. The proteins were purified using metal affinity chromatography. The immunoadjuvant effect of FliC was examined upon mixing as well as fusion with HitA antigen of P. aeruginosa in the presence of incomplete Freund’s adjuvant (IFA). This was tested by active immunization followed by challenge using P. aeruginosa murine infection model. Results: Two weeks after the last immunization dose, serum samples were tested for antibody response which showed significant HitA-specific IgG antibody response in all immunized groups compared to control groups. A significant reduction in bacterial burden of lungs from mice immunized with HitA/FliC/IFA mixture was observed after challenge. Opsonophagocytic assay and liver histopathological examination confirmed the previous results. Conclusion: Overall, HitA recombinant protein is considered a promising vaccine candidate against P. aeruginosa upon mixing with S. enterica flagellin protein FliC and IFA.
Highlights
Pseudomonas aeruginosa is an opportunistic, ubiquitous, Gram negative rod-shaped bacterium
We recently reported on the potential of HitA as a P. aeruginosa vaccine candidate in combination with Bacillus Calmette-Guérin (BCG) as an immunoadjuvant[16]
E. coli clones harboring the different constructed plasmids were confirmed by gene-specific polymerase chain reaction (PCR) reactions and DNA sequencing
Summary
Pseudomonas aeruginosa is an opportunistic, ubiquitous, Gram negative rod-shaped bacterium It can cause serious infections especially in immunocompromised patients such as cancer, burn, diabetic and cystic fibrosis patients[1]. The challenge of developing a protective vaccine against this pathogen is due to many factors such as high serotype variability of immunogenic epitopes and low immunogenicity of conserved epitopes[6], in addition to the high variability of host immune response due to different health conditions of people at risk to P. aeruginosa infection[7]. IFA is mixed with aqueous solution of antigen to form a water-in-oil emulsion It is commonly used as immunoadjuvant in animal experiments to elicit strong antibody response against co-administered vaccine antigens[10]
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