Research Center of Avian Diseases, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan, China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, Sichuan, China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan, China.
Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan, China.
Vaccine. 2021 Jan 15;39(3):588-595. doi: 10.1016/j.vaccine.2020.12.002. Epub 2020 Dec 17.
Salmonella enterica serovar Typhimurium is a major food-borne pathogen that can cause self-limited gastroenteritis or life-threatening invasive diseases in humans. There is no licensed S. Typhimurium vaccine for humans to date. In this study, we attempted to construct a live attenuated vaccine strain of S. Typhimurium based on three genes, namely, the two global regulator genes fnr and arcA and the flagellin subunit gene fliC. The S. Typhimurium three-gene mutant, named SLT39 (ΔfnrΔarcAΔfliC), exhibited a high level of attenuation with a colonization defect in mouse tissues and approximately 10-fold decreased virulence compared with that of the wild-type strain. To evaluate the immunogenicity and protection efficacy of STL39, mice were inoculated twice with a dose of 10 CFU or 10 CFU at a 28-day interval, and the immunized mice were challenged with a lethal dose of the wild-type S. Typhimurium strain one month post second immunization. Compared with mock immunization, SLT39 immunization with either dose elicited significant serum total IgG, IgG1 and IgG2a and faecal IgA responses against inactivated S. Typhimurium antigens at a comparable level post second immunization, whereas the 10 CFU group induced higher levels of duodenal and caecal IgA than the 10 CFU group. Furthermore, the bacterial loads in mouse tissues, including Peyer's patches, spleen and liver, significantly decreased in the two SLT39 immunization groups compared to those in the control group post challenge. Additionally, all mice in the SLT39 (10 CFU) group and 80% of the mice in the SLT39 (10 CFU) group survived the lethal challenge, suggesting full protection and 80% protection efficacy, respectively. Thus, the S. Typhimurium fnr, arcA and fliC mutant proved to be a potential attenuated live vaccine candidate for prevention of homologous infection.
肠炎沙门氏菌血清型 Typhimurium 是一种主要的食源性病原体，可导致人类自限性胃肠炎或危及生命的侵袭性疾病。目前尚无针对人类的沙门氏菌 Typhimurium 许可疫苗。在这项研究中，我们试图基于两个全局调控基因 fnr 和 arcA 和鞭毛亚基基因 fliC 构建肠炎沙门氏菌的减毒活疫苗株。命名为 SLT39（ΔfnrΔarcAΔfliC）的沙门氏菌三基因突变体在小鼠组织中表现出高水平的衰减和定植缺陷，与野生型菌株相比，其毒力降低了约 10 倍。为了评估 STL39 的免疫原性和保护效果，小鼠用 10 CFU 或 10 CFU 剂量接种两次，间隔 28 天，第二次免疫后一个月，用野生型沙门氏菌 Typhimurium 菌株的致死剂量攻毒免疫小鼠。与模拟免疫相比，两种剂量的 SLT39 免疫均在第二次免疫后诱导出针对灭活沙门氏菌 Typhimurium 抗原的显著血清总 IgG、IgG1 和 IgG2a 和粪便 IgA 反应，而 10 CFU 组诱导的十二指肠和盲肠 IgA 水平高于 10 CFU 组。此外，与对照组相比，在攻毒后，两个 SLT39 免疫组的小鼠组织（包括派尔集合淋巴结、脾脏和肝脏）中的细菌负荷显著降低。此外，SLT39（10 CFU）组的所有小鼠和 SLT39（10 CFU）组的 80%的小鼠均能耐受致死性攻毒，分别提示完全保护和 80%的保护效力。因此，沙门氏菌 fnr、arcA 和 fliC 突变体被证明是预防同源感染的潜在减毒活疫苗候选物。
