Eveline Weerdenburg, Jan Grijpstra, Suzanne P. M. Welten, Miranda M. C. van Beers, Peter Burghout, Elise S. Hovingh, Pepijn G.J.T.B. Wijnands, Leslie van der Fits, Garima Tiwari, L.J. Feitsma, Stephan Theisgen, Chakkumkal Anish, Kellen Fae, Jeroen Geurtsen, Jan Poolman
Abstract Extraintestinal pathogenic Escherichia coli (ExPEC) is a major cause of urinary tract infections (UTIs) and invasive disease. Rising antimicrobial resistance highlights the need for preventive strategies such as vaccination. The conserved D-mannose-specific adhesin FimH is essential during early UTI pathogenesis, making it an attractive vaccine target. We rationally designed a FimH lectin domain antigen stabilized in a low-affinity, tense conformation by two amino-acid substitutions ( LA FimH LD ), thereby exposing epitopes within the mannose-binding pocket relevant for functional immunity. Multiple vaccine formats incorporating LA FimH LD were generated, including fimbrial tip constructs, carrier protein fusions or conjugates and a nanoparticle. In rats, monomeric LA FimH LD induced functional antibody responses comparable to a clinically tested FimCH reference, while four LA FimH LD variants elicited superior inhibition of ExPEC binding to human bladder cells. A multimeric LA FimH LD –CRM 197 conjugate further demonstrated robust functional immunogenicity in minipigs. These data show enhanced FimH vaccine potency and identify candidates for UTI prevention.