Orally Fed Recombinant Lactococcus lactis Displaying Surface Anti-Fimbrial Nanobodies Protects Piglets against Escherichia coli Causing Post-Weaning Diarrhea

Emmanuel Okello,Joseph Erume,Henri De Greve,Kristof Moonens

doi:10.3390/agriculture11030186

Abstract

Post-weaning diarrhea (PWD) and edema disease (ED), caused by enterotoxigenic and Shiga toxin producing Escherichia coli (ETEC and STEC) strains, are important diseases of newly weaned piglets worldwide. The objective of this study is to develop a passive immunization strategy to protect piglets against PWD and ED using recombinant Lactococcus lactis added to piglet diet at weaning. The Variable Heavy chain domains of Heavy chain antibodies (VHHs) or Nanobodies (Nbs), directed against the fimbrial adhesins FaeG (F4 fimbriae) and FedF (F18 fimbriae) of E. coli were cloned and expressed on the surface of L. lactis. In vitro, the recombinant L. lactis strains agglutinated and inhibited adhesion of cognate F4 or F18 fimbriae expressing E. coli to pig villous preparation. In vivo, the anti-F4 L. lactis protected weaned piglets against a challenge with an F4-positive ETEC strain. Piglets supplemented with oral anti-F4 L. lactis showed reduced fecal E. coli shedding. We concluded that the surface expressed Nanobodies on L. lactis neutralized the adhesins of targeted E. coli and abrogated gut colonization, the first step in disease pathogenesis. As a proof of concept, we demonstrated the potential of passive immunization with recombinant L. lactis as a viable alternative to antibiotic prophylaxis in preventing piglet-post-weaning diarrhea.

Highlights

Post-weaning diarrhea (PWD) and edema disease (ED) caused by enterotoxigenic andShiga toxin producing Escherichia coli (ETEC and STEC) are a major cause of economic losses to pig farmers worldwide [1]
The objective of this study is to develop a passive immunization strategy to protect piglets against PWD and ED using recombinant Lactococcus lactis added to piglet diet at weaning
As a proof of concept, we demonstrated the potential of passive immunization with recombinant L. lactis as a viable alternative to antibiotic prophylaxis in preventing piglet-post-weaning diarrhea

Summary

Introduction

Post-weaning diarrhea (PWD) and edema disease (ED) caused by enterotoxigenic andShiga toxin producing Escherichia coli (ETEC and STEC) are a major cause of economic losses to pig farmers worldwide [1]. The strains express toxins that induce secretory diarrhea or edema disease by interfering with water and electrolyte transport across epithelial cells, or toxic endothelial cell apoptosis, respectively [8,9,10]. The peak antibody levels occur at 1 week (F4-specific IgA) and 3 weeks (F18-specific IgA) post infection respectively [12]. This immune response is dependent on receptor recognition of the antigen, since the receptor negative piglets tolerate fimbriae as normal food antigens [13]. The experimental immunization of piglets orally with purified F4 fimbriae or the adhesive subunit (FaeG) induced protective F4-specific mucosal immune response in piglets [16,17]. Oral immunization with purified F18-fimbriae induced specific immune responses to the major subunit FedA, but the immune response against the FedF adhesin was weak and non-protective against F18+ E. coli challenge [18]

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