Table_2_Nano selenium-enriched probiotic Lactobacillus enhances alum adjuvanticity and promotes antigen-specific systemic and mucosal immunity.doc

Nano selenium-enriched probiotics have been identified to improve immune responses, such as alleviating inflammation, antioxidant function, treatment of tumors, anticancer activity, and regulating intestinal flora. However, so far, there is little information on improving the immune effect of the vaccine. Here, we prepared nano selenium-enriched Levilactobacillus brevis 23017 (SeL) and heat-inactivated nano selenium-enriched L. brevis 23017 (HiSeL) and evaluated their immune enhancing functions on the alum-adjuvanted, inactivated Clostridium perfringens type A vaccine in mouse and rabbit models, respectively. We found that SeL enhanced immune responses of the vaccine by inducing a more rapid antibody production, eliciting higher immunoglobulin G (IgG) antibody titers, improving secretory immunoglobulin A (SIgA) antibody level and cellular immune response, and regulating Th1/Th2 immune response, thus helping to induce better protective efficacy after challenge. Moreover, we confirmed that the immunoenhancement effects are related to regulating oxidative stress, cytokine secretion, and selenoprotein expression. Meanwhile, similar effects were observed in HiSeL. In addition, they show enhanced humoral immune response at 1/2 and 1/4 standard vaccine doses, which confirms their prominent immune enhancement effect. Finally, the effect of improving vaccine immune responses was further confirmed in rabbits, which shows that SeL stimulates the production of IgG antibodies, generates α toxin–neutralizing antibodies rapidly, and reduces the pathological damage to intestine tissue. Our study demonstrates that nano selenium-enriched probiotics improve the immune effect of the alum adjuvants vaccine and highlight its potential usage in remedying the disadvantages of alum adjuvants.

纳米富硒益生菌（nano selenium-enriched probiotics）已被证实可改善免疫应答，包括缓解炎症、增强抗氧化功能、肿瘤治疗、抗癌活性以及调节肠道菌群。然而截至目前，关于其提升疫苗免疫效果的相关研究仍较为匮乏。本研究制备了纳米富硒短乳杆菌23017（Levilactobacillus brevis 23017，SeL）与热灭活纳米富硒短乳杆菌23017（HiSeL），并分别在小鼠与兔模型中评估其对铝佐剂灭活A型产气荚膜梭菌疫苗的免疫增强功能。研究发现，SeL可通过诱导更快的抗体生成、诱导更高水平的免疫球蛋白G（IgG）抗体滴度、提升分泌型免疫球蛋白A（SIgA）抗体水平与细胞免疫应答，并调节Th1/Th2免疫平衡，从而有助于攻毒后获得更优异的保护效力。此外，本研究证实该免疫增强效应与调节氧化应激、细胞因子分泌以及硒蛋白表达相关；同时，热灭活形式的HiSeL也展现出相似的效果。进一步实验显示，在疫苗剂量为标准剂量的1/2与1/4时，二者仍可增强体液免疫应答，验证了其突出的免疫增强效果。最终，该疫苗免疫增强效应在兔模型中得到进一步验证：SeL可刺激IgG抗体生成，快速产生α毒素中和抗体，并减轻肠道组织的病理损伤。本研究表明，纳米富硒益生菌可改善铝佐剂疫苗的免疫效果，凸显其在弥补铝佐剂固有缺陷方面的应用潜力。