Department of Molecular Medicine, Morsani School of Medicine, University of South Florida, Tampa, Florida, USA.
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA.
Infect Immun. 2018 Oct 25;86(11). doi: 10.1128/IAI.00489-18. Print 2018 Nov.
The symptoms of infection (CDI) are attributed largely to two toxins, TcdA and TcdB. Significant efforts have been devoted to developing vaccines targeting both toxins through parenteral immunization routes. However, is an enteric pathogen, and mucosal/oral immunization would be particularly useful to protect the host against CDI, considering that the gut is the main site of disease onset and progression. Moreover, vaccines directed only against toxins do not target the cells and spores that transmit the disease. Previously, we constructed a chimeric vaccine candidate, mTcd138, comprised of the glucosyltransferase and cysteine proteinase domains of TcdB and the receptor binding domain of TcdA. In this study, to develop an oral vaccine that can target both toxins and colonization/adhesion factors, we expressed mTcd138 in a nontoxigenic (NTCD) strain, resulting in strain NTCD_mTcd138. Oral immunization with spores of NTCD_mTcd138 provided mice full protection against infection with a hypervirulent strain, UK6 (ribotype 027). The protective strength and efficacy of NTCD_mTcd138 were further evaluated in the acute CDI hamster model. Oral immunization with spores of NTCD_mTcd138 also provided hamsters significant protection against infection with 2 × 10 UK6 spores, a dose 200-fold higher than the lethal dose of UK6 in hamsters. These results imply that the genetically modified, nontoxigenic strain expressing mTcd138 may represent a novel mucosal vaccine candidate against CDI.
感染（CDI）的症状主要归因于两种毒素，TcdA 和 TcdB。人们已经投入大量努力通过肠外免疫途径开发针对这两种毒素的疫苗。然而，是一种肠道病原体，黏膜/口服免疫将特别有助于保护宿主免受 CDI 的侵害，因为肠道是疾病发生和进展的主要部位。此外，仅针对毒素的疫苗不能针对传播疾病的细胞和孢子。先前，我们构建了一种嵌合疫苗候选物 mTcd138，它由 TcdB 的葡糖基转移酶和半胱氨酸蛋白酶结构域以及 TcdA 的受体结合结构域组成。在这项研究中，为了开发一种可以针对两种毒素和定植/黏附因子的口服疫苗，我们在非产毒（NTCD）菌株中表达了 mTcd138，导致产生了 NTCD_mTcd138 菌株。用 NTCD_mTcd138 的孢子进行口服免疫，为小鼠提供了针对高毒力 菌株 UK6（型 027）感染的完全保护。在急性 CDI 仓鼠模型中进一步评估了 NTCD_mTcd138 的保护强度和功效。用 NTCD_mTcd138 的孢子进行口服免疫，也为仓鼠提供了针对 2×10 UK6 孢子感染的显著保护，这一剂量是 UK6 在仓鼠中的致死剂量的 200 倍。这些结果表明，表达 mTcd138 的遗传修饰非产毒 菌株可能代表了一种针对 CDI 的新型黏膜疫苗候选物。
