Stabilisation of the gut microbiota and reduction of ETEC proliferation in piglets using two bivalent VHH constructs

Post-weaning diarrhea (PWD) in piglets presents a widespread problem in industrial pig production and is caused by enterotoxigenic E. coli (ETEC) strains. Current solutions, such as antibiotics and medicinal zinc oxide, are unsustainable and face bans, resulting in a dire need for novel solutions. Thus, in this study, we propose and evaluate a protein-based feed additive, comprising bivalent heavy chain variable domain (VHH) constructs. We demonstrate in vitro that these constructs bind to ETEC toxins and fimbriae, whilst not affecting bacterial growth rate. Furthermore, in a pig study, we show that oral administration of these constructs after ETEC challenge reduced ETEC proliferation, and potentially stabilised the commensal microbiota when compared to challenged control piglets. These data suggest that such VHH constructs may find utility in industrial pig production as a feed additive for tackling ETEC and reducing the risk of PWD in piglet populations.仔猪断奶后腹泻（Post-weaning diarrhea, PWD）是工业化生猪养殖中的普遍难题，其致病原为产肠毒素大肠杆菌（enterotoxigenic E. coli, ETEC）菌株。当前常用解决方案如抗生素与药用氧化锌均不具备可持续性，且面临禁用风险，因此亟需开发新型防控手段。本研究提出并评估了一种基于蛋白质的饲料添加剂，其成分为双价重链可变域（bivalent heavy chain variable domain, VHH）构建体。体外实验证实，该类构建体可结合ETEC毒素与菌毛，且不会影响细菌生长速率。生猪养殖试验进一步显示，相较于攻毒对照组仔猪，在ETEC攻毒后口服该构建体可抑制ETEC增殖，并可能稳定共生微生物群结构。上述数据表明，此类VHH构建体有望作为饲料添加剂应用于工业化生猪养殖，用于防控ETEC感染并降低仔猪断奶后腹泻的发病风险。