Li Siqi, Seo Hyesuk, Upadhyay Ipshita, Zhang Weiping
Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.
Microorganisms. 2023 Oct 1;11(10):2473. doi: 10.3390/microorganisms11102473.
The increasing prevalence and association with moderate-to-severe diarrhea make enterotoxigenic (ETEC) adhesins CS7, CS12, CS14, CS17, and CS21 potential targets of ETEC vaccines. Currently, there are no vaccines licensed to protect against ETEC, a top cause of children's diarrhea and travelers' diarrhea. Recently, a polyvalent adhesin protein (adhesin MEFA-II) was demonstrated to induce antibodies that inhibited adherence from these five ETEC adhesins and reduced the enterotoxicity of ETEC heat-stable toxin (STa), which plays a key role in causing ETEC-associated diarrhea. To improve adhesin MEFA-II for functional antibodies against STa toxin and the other ETEC toxin, heat-labile toxin (LT), we modified adhesin MEFA-II by adding another STa toxoid and an LT epitope; we examined the new antigen immunogenicity (to five adhesins and two toxins) and more importantly antibody functions against ETEC adherence and STa and LT enterotoxicity. Data show that mice intramuscularly immunized with the new antigen (adhesin MEFA-IIb) developed robust IgG responses to the targeted adhesins (CS7, CS12, CS14, CS17, and CS21) and toxins (STa and LT). Mouse antibodies inhibited the adherence of ETEC strains expressing any of these five adhesins but failed to neutralize STa or LT enterotoxicity. In further studies, rabbits intramuscularly immunized with adhesin MEFA-IIb developed robust antigen-specific antibodies; when challenged with an ETEC isolate expressing CS21 adhesin (JF2101, CS21, and STa), the immunized rabbits showed a significant reduction in intestinal colonization by ETEC bacteria. These data indicate that adhesin MEFA-IIb is broadly immunogenic and induces functional antibodies against the targeted ETEC adhesins but not the toxins.
产肠毒素大肠杆菌（ETEC）黏附素CS7、CS12、CS14、CS17和CS21的患病率不断上升，且与中重度腹泻相关，这使其成为ETEC疫苗的潜在靶点。目前，尚无获批用于预防ETEC的疫苗，ETEC是儿童腹泻和旅行者腹泻的主要病因。最近，一种多价黏附素蛋白（黏附素MEFA-II）被证明可诱导抗体，抑制这五种ETEC黏附素的黏附，并降低ETEC热稳定毒素（STa）的肠毒性，STa在导致ETEC相关腹泻中起关键作用。为了改进黏附素MEFA-II，以产生针对STa毒素和其他ETEC毒素（不耐热毒素，LT）的功能性抗体，我们通过添加另一种STa类毒素和一个LT表位对黏附素MEFA-II进行了修饰；我们检测了新抗原的免疫原性（针对五种黏附素和两种毒素），更重要的是检测了抗体针对ETEC黏附以及STa和LT肠毒性的功能。数据显示，用新抗原（黏附素MEFA-IIb）进行肌肉注射免疫的小鼠对靶向黏附素（CS7、CS12、CS14、CS17和CS21）和毒素（STa和LT）产生了强烈的IgG反应。小鼠抗体抑制了表达这五种黏附素中任何一种的ETEC菌株的黏附，但未能中和STa或LT的肠毒性。在进一步的研究中，用黏附素MEFA-IIb进行肌肉注射免疫的兔子产生了强烈的抗原特异性抗体；当用表达CS21黏附素的ETEC分离株（JF2101、CS21和STa）进行攻击时，免疫的兔子显示ETEC细菌在肠道中的定植显著减少。这些数据表明，黏附素MEFA-IIb具有广泛的免疫原性，可诱导针对靶向ETEC黏附素而非毒素的功能性抗体。
