Identification of lipid A deacylase as a novel, highly conserved and protective antigen against enterohemorrhagic Escherichia coli

Maricarmen Rojas-Lopez,Marco Soriani,Mariagrazia Pizza,Valentina Brandi,Grégory Jubelin,Manuele Martinelli,Fabio Polticelli,Mickaël Desvaux,Roberto Rosini

doi:10.1038/s41598-019-53197-z

Maricarmen Rojas-Lopez, Marco Soriani + Show 7 more

Open Access

https://doi.org/10.1038/s41598-019-53197-z

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Abstract

Enterohemorrhagic E. coli (EHEC) is a major cause of large outbreaks worldwide associated with hemorrhagic colitis and hemolytic uremic syndrome. While vaccine development is warranted, a licensed vaccine, specific for human use, against EHEC is not yet available. In this study, the reverse vaccinology approach combined with genomic, transcriptional and molecular epidemiology data was applied on the EHEC O157:H7 genome to select new potential vaccine candidates. Twenty-four potential protein antigens were identified and one of them (MC001) was successfully expressed onto Generalized Modules for Membrane Antigens (GMMA) delivery system. GMMA expressing this vaccine candidate was immunogenic, raising a specific antibody response. Immunization with the MC001 candidate was able to reduce the bacterial load of EHEC O157:H7 strain in feces, colon and caecum tissues after murine infection. MC001 is homologue to lipid A deacylase enzyme (LpxR), and to our knowledge, this is the first study describing it as a potential vaccine candidate. Gene distribution and sequence variability analysis showed that MC001 is present and conserved in EHEC and in enteropathogenic E. coli (EPEC) strains. Given the high genetic variability among and within E. coli pathotypes, the identification of such conserved antigen suggests that its inclusion in a vaccine might represent a solution against major intestinal pathogenic strains.

Highlights

Enterohemorrhagic E. coli (EHEC) is a major cause of large outbreaks worldwide associated with hemorrhagic colitis and hemolytic uremic syndrome
Virulence factors expressed as recombinant proteins such as Shiga toxin (Stx), intimin, E. coli secreted protein A (EspA), and avirulent ghost cells of EHEC O157:H7 have been tested using different immunization routes and adjuvant combinations in several animal models with encouraging results[10]
The PSORT algorithm was applied to predict the subcellular localization of the 5675 coding sequences (CDS) annotated in the genome

Summary

Introduction

Enterohemorrhagic E. coli (EHEC) is a major cause of large outbreaks worldwide associated with hemorrhagic colitis and hemolytic uremic syndrome. A recent in silico approach aimed to develop DNA based vaccine identified new EHEC antigens, including among others a putative pilin subunit, T3SS structural protein (escC) gene, and an outer membrane protein encoded by the bacteriophage Bp933W gene lomW11,12. Previous studies have identified new promising vaccine candidates demonstrating the potential of exploiting the reverse vaccinology concept[11,12,13,14,15,16]. This strategy has been performed on a completely sequence genome of an extraintestinal neonatal meningitis E. coli isolate (NMEC) leading to the identification of 230 potential antigens. A conserved zinc metallopeptidase, SslE, was one of the most protective antigens by conferring protection in three different murine models[15,17,18]

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