Department of Microbiology, Immunology and Cell Biology, School of Medicine, West Virginia University, Morgantown, WV, United States.
Front Immunol. 2023 Jul 20;14:1177650. doi: 10.3389/fimmu.2023.1177650. eCollection 2023.
is a gram-negative bacterium that is the etiological agent of the tropical disease melioidosis. Currently, there is no licensed vaccine for melioidosis, but numerous candidates are being tested for protective efficacy and characterization of the elicited immune response. Our lab has previously reported the immunogenicity of a Bucl8-protein-based peptide antigen, designated L1-CRM (Cross-reacting material 197). When given subcutaneously, this vaccine formulation promoted a strong Th2 (IgG1) antibody response, however immunization did not protect from death. In this study, we hypothesized that an intranasally administered L1-CRM vaccine would induce protective mucosal immunity. To evaluate vaccine efficacy, we developed a surrogate infection model that employs outbred CD-1 mice which imitates the immunogenetic diversity of humans. Mice were immunized with either L1-CRM adjuvanted with fluorinated cyclic diguanosine monophosphate (FCDG) or with FCDG-only control. These mice were then challenged intranasally with an infectious dose of a luminescent strain of E264 two weeks post-immunization, and correlates of protection were assessed in euthanized mice on days 1, 2, 3, and 7 post-infection. Overall, intranasal vaccination, compared to subcutaneous administration, induced a stronger Th1 (IgG2a/2b) to Th2 (IgG1) antibody response and promoted anti-L1 nasal, pulmonary, and systemic IgA. Additionally, sera IgG from L1-CRM-vaccinated mice recognized whole-cell and , a select agent exempt strain Bp82. Vaccination ameliorated disease indicators, including luminescent signal and bacterial cell counts, weight and temperature loss, and organ weight, which negatively correlated with IgG2a antibody levels and mucosa-stimulating cytokines IL-13 and IL-9. L1-CRM-vaccinated mice also had earlier resolution of inflammatory and tissue-damaging cytokines compared to the FCDG-only controls. These results suggest a balanced humoral and cell-mediated response, along with mucosa-based immunity are beneficial for protection. Future efforts should further assess mucosal cellular and humoral mechanisms of protection and test such protection, using aerosolized select agent strain(s).
是一种革兰氏阴性细菌，是热带病类鼻疽病的病原体。目前，尚无针对类鼻疽病的许可疫苗，但有许多候选疫苗正在进行保护性效力和所引起免疫反应的特征描述测试。我们实验室先前曾报道过基于 Bucl8 蛋白的肽抗原 L1-CRM（交叉反应物质 197）的免疫原性。当经皮下给药时，这种疫苗配方可促进强烈的 Th2（IgG1）抗体反应，但是免疫接种并不能预防死亡。在这项研究中，我们假设经鼻内给予 L1-CRM 疫苗可诱导保护性粘膜免疫。为了评估疫苗的功效，我们开发了一种替代感染模型，该模型使用了具有人类免疫遗传多样性的远交 CD-1 小鼠。用氟代环二核苷酸（FCDG）佐剂的 L1-CRM 或仅用 FCDG 佐剂的对照免疫小鼠。两周后，在免疫后，用发光株 E264 的感染剂量经鼻内对这些小鼠进行攻击，并在感染后第 1、2、3 和 7 天处死小鼠，评估保护相关性。总体而言，与皮下给药相比，经鼻内接种可诱导更强的 Th1（IgG2a/2b）至 Th2（IgG1）抗体反应，并促进抗 L1 鼻、肺和全身 IgA。此外，L1-CRM 疫苗接种小鼠的血清 IgG 可识别全细胞和 ，这是一种豁免选择剂 Bp82 的菌株。接种疫苗可改善疾病指标，包括发光信号和细菌细胞计数、体重和体温下降以及器官重量，这些指标与 IgG2a 抗体水平和粘膜刺激细胞因子 IL-13 和 IL-9 呈负相关。与仅用 FCDG 佐剂的对照相比，L1-CRM 疫苗接种小鼠的炎症和组织损伤细胞因子的消退也更早。这些结果表明，平衡的体液和细胞介导的反应以及基于粘膜的免疫对于保护是有益的。未来的工作应进一步评估粘膜细胞和体液的保护机制，并使用雾化的选择剂菌株测试这种保护。
