Immunogenic characteristics of the outer membrane phosphoporin as a vaccine candidate against Klebsiella pneumoniae

Gaowei Hu,Yingjie Miao,Xue Chen,Xi Luo,Zhe Ma,Yongqian Fu,Wenhui Chu

doi:10.1186/s13567-022-01023-2

Abstract

In recent years, Klebsiella pneumoniae (KP) has caused disease outbreaks in different animals, resulting in serious economic losses and biosafety concerns. Considering the broad antibiotic resistance of KP, vaccines are the most effective tools against infection. However, there is still no KP vaccine available in the veterinary field. Our results indicate that the highly conserved outer membrane phosphoporin (PhoE) of KP is immunogenic in mice and elicits high titers of antibodies that were shown to be specific for PhoE by immunoblotting. Immunization with PhoE also induced robust cell-mediated immunity and elicited the secretion of high levels of IFN-γ and IL-4, suggesting the induction of mixed Th1 and Th2 responses. Sera from PhoE-immunized mice induced significantly higher complement-mediated lysis of KP cells than did sera from the PBS control mice. Finally, mice immunized with PhoE were significantly protected against KP challenge, with better survival and a reduced visceral bacterial load. Our data underscore the great potential of PhoE as a novel candidate antigen for a vaccine against KP infection.

Highlights

Klebsiella pneumoniae (KP) is an important Gramnegative zoonotic opportunistic pathogen belonging to the family Enterobacteriaceae [1]
PhoE is conserved among different KP strains and was predicted to contain potential antigenic epitopes Based on the sequence alignment, we found that the PhoE protein was highly conserved among different KP strains (Figure 1A)
The results showed that positive interferon γ (IFN-γ) and interleukin 4 (IL-4)-secreting cells were only induced in the PhoE immunized group or the inactivated whole bacteria (IWB) positive control group (p > 0.05), but not in the phosphate buffered saline (PBS) negative control group (p < 0.01; Figures 4A and B and Additional file 1)

Summary

Introduction

Klebsiella pneumoniae (KP) is an important Gramnegative zoonotic opportunistic pathogen belonging to the family Enterobacteriaceae [1]. It can infect both humans and a broad spectrum of farm animals, such as pigs, cows, chickens and fishes, leading to pneumonia, meningitis, liver abscess, inflammation of the urinary tract, wound infections and even sepsis. Inactivated vaccines require more than five vaccinations to produce a satisfactory serological response [9]. Capsular polysaccharides are good antigens for vaccine production and their conjugate vaccines are proven effective against infections caused by KP, the resulting protection was often short-lived [11]

Methods

Results

Conclusion