Nanobody mediated inhibition of attachment of F18 Fimbriae expressing Escherichia coli.

Kristof Moonens,Henri De Greve,Annelies Coddens,Eric Cox,Han Remaut,Els Pardon,Maia De Kerpel,Eric Cascales

doi:10.1371/journal.pone.0114691

Kristof Moonens, Henri De Greve + Show 6 more

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https://doi.org/10.1371/journal.pone.0114691

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Abstract

Post-weaning diarrhea and edema disease caused by F18 fimbriated E. coli are important diseases in newly weaned piglets and lead to severe production losses in farming industry. Protective treatments against these infections have thus far limited efficacy. In this study we generated nanobodies directed against the lectin domain of the F18 fimbrial adhesin FedF and showed in an in vitro adherence assay that four unique nanobodies inhibit the attachment of F18 fimbriated E. coli bacteria to piglet enterocytes. Crystallization of the FedF lectin domain with the most potent inhibitory nanobodies revealed their mechanism of action. These either competed with the binding of the blood group antigen receptor on the FedF surface or induced a conformational change in which the CDR3 region of the nanobody displaces the D″-E loop adjacent to the binding site. This D″-E loop was previously shown to be required for the interaction between F18 fimbriated bacteria and blood group antigen receptors in a membrane context. This work demonstrates the feasibility of inhibiting the attachment of fimbriated pathogens by employing nanobodies directed against the adhesin domain.

Highlights

In farming industry enterotoxigenic Escherichia coli (ETEC) and Shiga toxin producing E. coli (STEC) are important pathogens [1, 2] causing serious mortality and severe production losses [3]
A llama was immunized with FedF15–165 and specific nanobodies were selected by panning the immune library, derived from the llama peripheral blood lymphocytes, in two consecutive rounds using the phage display technology [21]
The amount of bacteria adhering to the villi lining were counted, the results are summarized in Fig. 1 and showed that three categories of nanobodies could be distinguished

Summary

Introduction

In farming industry enterotoxigenic Escherichia coli (ETEC) and Shiga toxin producing E. coli (STEC) are important pathogens [1, 2] causing serious mortality and severe production losses [3]. Common to both classes of pathogenic E. coli is the presence of two crucial virulence factors: (1) adherence factors In piglets ETEC and STEC strains expressing F18 fimbriae are associated with respectively post-weaning diarrhoea and edema disease [4, 5]. STEC lack a secretory mechanism for Stx and the release of Stx occurs through lambdoid phage-mediated lysis [10]

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