In the present study, we developed an O-antigen-deficient, live, attenuated Salmonella Typhimurium (ST) strain (JOL2377) and assessed its safety, macrophage toxicity, invasion into lymphoid tissues, immunogenicity, and protection against Salmonella infection in chickens. The JOL2377 induced significantly lower cytotoxicity and higher level of cytokine response in IL-2, IL-10, IL-4, and IFN- γ than the WT strain upon macrophage uptake. It did not persist in macrophages or in chicken organs and rapidly cleared without systemic infection. None of the chicken were found to secrete Salmonella in feces into the environment exacerbating its attenuation. Interestingly JOL2377 successfully arrived in immunological hot-spots such as spleen, liver and bursa of Fabricius for an efficient antigen presentation and immune stimulation. Mucosal and parenteral immunization with JOL2377 significantly elicit antigen-specific humoral (IgY) and cell mediated responses marked by peripheral blood mononuclear cell proliferation, cytokine induction, increase in T-cell responses than non-immunized control. JOL2377 did not generate significant levels of LPS specific antibodies as compared to the WT strain due to the lack of immunogenic O-antigen component from its LPS structure. Upon virulent challenge, route dependent efficacy differences were leaving the intramuscular route is superior to the oral route on reducing splenic and liver colonization of the challenge ST. The least cytotoxicity, virulence, and superior immunogenicity of JL2377 that effectively engage both humoral and IFN- γ mediated CMI responses present an ideal scenario in host immune modulation to fight against intracellular pathogen Salmonella.

在本研究中，我们开发了一种缺乏 O 抗原的活的减毒鼠伤寒沙门氏菌 (ST) 菌株 (JOL2377)，并评估了其安全性、巨噬细胞毒性、对淋巴组织的侵袭、免疫原性以及对鸡中沙门氏菌感染的保护。在巨噬细胞摄取后，JOL2377 在 IL-2、IL-10、IL-4 和 IFN-γ 中诱导显着更低的细胞毒性和更高水平的细胞因子反应。它不会在巨噬细胞或鸡器官中持续存在，并且在没有全身感染的情况下迅速清除。没有发现鸡分泌沙门氏菌在粪便中进入环境加剧了其衰减。有趣的是，JOL2377 成功到达免疫热点，如脾、肝和法氏囊，用于有效的抗原呈递和免疫刺激。用 JOL2377 进行粘膜和肠胃外免疫显着引发抗原特异性体液 (IgY) 和细胞介导的反应，其特征是外周血单核细胞增殖、细胞因子诱导、T 细胞反应比非免疫对照增加。由于缺乏来自其 LPS 结构的免疫原性 O-抗原成分，JOL2377 与 WT 菌株相比没有产生显着水平的 LPS 特异性抗体。面对恶毒的挑战，途径依赖性疗效差异显着，肌肉注射途径在减少挑战ST的脾脏和肝脏定植方面优于口服途径。JL2377 具有最低的细胞毒性、毒力和优越的免疫原性，可有效参与体液和 IFN-γ 介导的 CMI 反应，是宿主免疫调节以对抗细胞内病原体的理想方案沙门氏菌。