Repeat modules and N-linked glycans define structure and antigenicity of a critical enterotoxigenic E. coli adhesin

• DOI: 10.1371/journal.ppat.1012241
• Publication Date: 2024-09-16T18:02:58Z
• Authors: Zachary T. Berndsen; Marjahan Akhtar; Mahima Thapa; Tim J. Vickers; Aaron Schmitz; Jonathan L. Torres; Sabyasachi Baboo; Pardeep Kumar; Nazia Khatoon; Alaullah Sheikh; Melissa Hamrick; Jolene K. Diedrich; Salvador Martinez...; Patrick T. Garrett; John R. Yates; Jackson S. Turner; Renee M. Laird; Frédéric Poly; Chad K. Porter; Jeffrey Copps; Ali H. Ellebedy; Andrew B. Ward; James M. Fleckens...
• Keywords: Enterotoxigenic Escherichia coli; Polyclonal antibodies

Enterotoxigenic Escherichia coli (ETEC) cause hundreds of millions cases infectious diarrhea annually, predominantly in children from low-middle income regions. Notably, children, as well volunteers challenged with ETEC, diarrheal severity is significantly increased blood group A (bgA) individuals. EtpA, a secreted glycoprotein adhesin that functions lectin to promote critical interactions between ETEC and glycans on intestinal epithelia for effective bacterial adhesion toxin delivery. EtpA highly immunogenic resulting robust antibody responses following natural infection experimental challenge ETEC. To understand how directs ETEC-blood stimulates adaptive immunity, we mutated mapped its glycosylation by mass-spectrometry (MS), isolated polyclonal (pAbs) monoclonal antibodies (mAbs) vaccinated mice ETEC-infected volunteers, determined structures antibody-EtpA complexes cryo-electron microscopy. Both bgA mAbs inhibited EtpA-bgA adhesion, bound the C-terminal repeat domain highlighting this region crucial pathogen-host interaction. MS analysis uncovered extensive heterogeneous N-linked cryo-EM revealed directly engage these unique glycan containing epitopes. Finally, electron microscopy-based epitope mapping targeting numerous distinct epitopes N domains, suggesting vaccination generates against neutralizing decoy regions molecule. Collectively, anticipate data will inform our general understanding immunity relevant rational vaccine subunit design.