Oral vaccines are highly demanded by aquaculture sector that requires alternatives to injectable vaccines, involving fish handling, stress-related immunosuppression and mortalities. However, most previous attempts to obtain effective oral vaccines have failed due to a restricted tolerance mechanisms in intestine, whose mucosa is at the frontline of antigen encounter and has to balance the equilibrium between tolerance and immunity in a microbe-rich environment. Thus, the search for oral adjuvants that could augment immune responses triggered by antigens allowing them to circumvent intestinal tolerance is of great relevance. The present work focuses on the adjuvant potential of the Escherichia coli LT(R192G/L211A) toxoid (dmLT). To undertake an initial screening of the potential that dmLT has as an oral adjuvant in rainbow trout (Oncorhynchus mykiss), we have analyzed its transcriptional effects alone or in combination with Aeromonas salmonicida subsp. salmonicida or viral hemorrhagic septicemia virus (VHSV) on rainbow trout intestinal epithelial cell line RTgutGC and gut explants. Our results show that although dmLT provoked no significant effects by itself, it increased the transcription of pro-inflammatory cytokines and antimicrobial genes induced by the bacteria. In contrast, when combined with VHSV, dmLT only increased the transcription of Mx and the intracellular adhesion molecule 1 (ICAM1). Therefore, the protocol designed is an effective method to initially evaluate the effects of potential oral adjuvants, and points to dmLT as an effective adjuvant for oral antibacterial vaccines.

水产养殖部门对口服疫苗的需求很高，这需要注射疫苗的替代品，涉及鱼类处理，与压力有关的免疫抑制和死亡率。但是，由于肠道中有限的耐受机制，大多数先前获得有效口服疫苗的尝试均以失败告终，因为肠道的粘膜处于抗原接触的前沿，并且必须在富含微生物的环境中平衡耐受性和免疫力之间的平衡。因此，寻找可以增强抗原触发的免疫反应，使其绕过肠耐受的口服佐剂具有重大意义。目前的工作侧重于大肠杆菌的佐剂潜力LT（R192G / L211A）类毒素（dmLT）。为了初步筛查dmLT作为虹鳟（Oncorhynchus mykiss）口服佐剂的潜力，我们已经分析了其单独或与沙门氏气单胞菌组合的转录作用。鲑科或虹鳟鱼肠上皮细胞系RTgutGC和肠外植体上的病毒性出血性败血病病毒（VHSV）。我们的结果表明，尽管dmLT本身没有引起明显的作用，但它增加了细菌诱导的促炎性细胞因子和抗菌基因的转录。相反，当与VHSV结合使用时，dmLT仅增加Mx和细胞内粘附分子1（ICAM1）的转录。因此，设计的方案是初步评估潜在口服佐剂效果的有效方法，并指出dmLT作为口服抗菌疫苗的有效佐剂。