Glycoconjugate vaccine containing Escherichia coli O157:H7 O-antigen linked with maltose-binding protein elicits humoral and cellular responses.

Zhongrui Ma,Huajie Zhang,Min Chen,Wenjing Shang,Xueer Zhao,Donglei Han,Weiqing Han,Faliang Zhu,Peng George Wang,John S Tregoning

doi:10.1371/journal.pone.0105215

Zhongrui Ma, Huajie Zhang + Show 8 more

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https://doi.org/10.1371/journal.pone.0105215

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Abstract

Glycoconjugate is one of the most efficacious and safest vaccines against bacterial pathogens. Previous studies of glycoconjugates against pathogen E. coli O157:H7 focused more on the humoral responses they elicited. However, little was known about their cellular responses. In this study, we exploited a novel approach based on bacterial protein N-linked glycosylation system to produce glycoconjugate containing Escherichia coli O157:H7 O-antigen linked with maltose-binding protein and examined its humoral and cellular responses in BALB/c mice. The transfer of E. coli O157:H7 O-antigen to MBP was confirmed by western blot and MALDI-TOF MS. Mice injected with glycoconjugate O-Ag-MBP elicited serum bactericidal antibodies including anti-E. coli O157:H7 O-antigen IgG and IgM. Interestingly, O-Ag-MBP also stimulated the secretion of anti-E. coli O157:H7 O-antigen IgA in intestine. In addition, O-Ag-MBP stimulated cellular responses by recruiting Th1-biased CD4+ T cells, CD8+ T cells. Meanwhile, O-Ag-MBP induced the upregulation of Th1-related IFN-γ and downregulation of Th2-related IL-4, and the upregulation of IFN-γ was stimulated by MBP in a dose-dependent manner. MBP showed TLR4 agonist-like properties to activate Th1 cells as carrier protein of O-Ag-MBP. Thus, glycoconjugate vaccine E. coli O157:H7-specific O-Ag-MBP produced by bacterial protein N-linked glycosylation system was able to elicit both humoral and Th1-biased cellular responses.

Highlights

Enterhemorrhagic Escherichia coli (EHEC) O157:H7, as a severe enteric pathogen in human, generally causes bloody diarrhea, hemorrhagic colitis and hemolytic uremic syndrome (HUS) [1,2]
A recombinant plasmid pYES1L-O-Ag responding for E. coli O157:H7 O-Ag biosynthesis with its native promoter was constructed in this study
In consideration that O-Ag is dominant in forming heterogeneous LPS profiles, and E. coli W3110 cannot synthesize its own O-Ag due to the inactivation of wbbl gene [23], the similar LPS profiles between E. coli W3110 containing pYES1L-O-Ag and that of E. coli O157:H7 verified the expression of E. coli O157:H7 O-Ag in E. coli W3110 and the chain length was controlled mainly by wzzO157 gene instead of wzzW3110 gene

Summary

Introduction

Enterhemorrhagic Escherichia coli (EHEC) O157:H7, as a severe enteric pathogen in human, generally causes bloody diarrhea, hemorrhagic colitis and hemolytic uremic syndrome (HUS) [1,2]. There is an urgent need for vaccines to prevent Escherichia coli (E. coli) O157:H7 infection. Several potential vaccines have been tested in a number of preclinical or clinical studies [5]. Glycoconjugate (O-antigen covalently linked to carrier protein) is considered one of the most efficacious and safest vaccines against bacterial pathogens. O-Ag is exposed on the very outer surface of the bacterial cell, and, as a consequence, is a target for recognition by host antibodies. O-Ag is T-lymphocyte independent antigen like other bacterial polysaccharides. O-Ag alone cannot induce a high serum IgG and sustained T cell memory [6]

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