The development and characterization of an E. coli O25B bioconjugate vaccine

Abstract

Extraintestinal pathogenic Escherichia coli (ExPEC) cause a wide range of clinical diseases such as bacteremia and urinary tract infections. The increase of multidrug resistant ExPEC strains is becoming a major concern for the treatment of these infections and E. coli has been identified as a critical priority pathogen by the WHO. Therefore, the development of vaccines has become increasingly important, with the surface lipopolysaccharide constituting a promising vaccine target. This study presents genetic and structural analysis of clinical urine isolates from Switzerland belonging to the serotype O25. Approximately 75% of these isolates were shown to correspond to the substructure O25B only recently described in an emerging clone of E. coli sequence type 131. To address the high occurrence of O25B in clinical isolates, an O25B glycoconjugate vaccine was prepared using an E. coli glycosylation system. The O antigen cluster was integrated into the genome of E. coli W3110, thereby generating an E. coli strain able to synthesize the O25B polysaccharide on a carrier lipid. The polysaccharide was enzymatically conjugated to specific asparagine side chains of the carrier protein exotoxin A (EPA) of Pseudomonas aeruginosa by the PglB oligosaccharyltransferase from Campylobacter jejuni. Detailed characterization of the O25B-EPA conjugate by use of physicochemical methods including NMR and GC-MS confirmed the O25B polysaccharide structure in the conjugate, opening up the possibility to develop a multivalent E. coli conjugate vaccine containing O25B-EPA.

The role of vaccines in combating antimicrobial resistance (AMR) bacteria

“…Pfizer’s TcdA and TcdB toxoid vaccine and Valneva’s VLA84 already in their phase III trials, are both very immunogenic and have proved to be effective ( de Bruyn et al, 2021 , Stevens et al, 2021 ). ExPEC, a vaccine based on adhesion protein FimH and an adjuvant ( Kowarik et al, 2021 , Palmioli et al, 2021 ) and ExPEC4V, a vaccine based on O antigens ( Jiang et al, 2021 , Verboom et al, 2021 ), are in their phase I trials against the AMR pathogenic extra intestinal E. coli. StaphVAX, V710 and SA4ag, developed against S. aureus have been analyzed for efficacy in clinical trials ( Fernandez et al, 2021 ; Scully et al, 2021 ).…”

Preclinical Immunogenicity and Efficacy of Optimized O25b O-Antigen Glycoconjugates To Prevent MDR ST131 E. coli Infections

“…Native O antigens can be cleaved from bacterial lipopolysaccharide (LPS) by acid hydrolysis, and isolated E. coli O antigens have been conjugated to the Pseudomonas exotoxin A (EPA) carrier protein by chemical cross-linking ( 15 ). Alternatively, a bioconjugation platform was developed allowing conjugation of O antigens to EPA using a recombinant E. coli platform ( 16 , 17 ). In this case, the O-polysaccharide is assembled on its carrier lipid and enzymatically transferred to specific residues of the protein carrier via an N-glycosidic linkage ( 18 ).…”

Glycan and Protein Analysis of Glycoengineered Bacterial E. coli Vaccines by MALDI-in-Source Decay FT-ICR Mass Spectrometry

“… 14 − 17 This technology has been recently used to develop glycoconjugate vaccine candidates against E. coli serotypes O1, O2, O6A, and O25B by coupling the serotype-specific O-antigens to exotoxin A from Pseudomonas aeruginosa (EPA). 16 , 18 − 20 …”

“…This characteristic has been successfully used for the development of bacterial vaccines. 16 , 20 , 26 …”