Bio-Therapy Human Resources Center, College of Veterinary Medicine, Gwangju 501-746, Republic of Korea.
J Microbiol. 2010 Oct;48(5):674-81. doi: 10.1007/s12275-010-0179-6. Epub 2010 Nov 3.
To protect chickens from typhoid caused by Salmonella enterica serovar Gallinarum (S. Gallinarum), the attenuated 9R strain has been used in the field as a vaccine. However, safety concerns have been raised because the mutations in 9R are undefined while its efficacy is still a question under debate. A global regulator, ppGpp, synthesized by RelA and SpoT, has been shown to induce various virulence genes in S. Gallinarum (Jeong et al., 2008). In this study, two mutant strains defective in ppGpp-synthesis were constructed in wild-type S. Gallinarum (ΔppGpp) and 9R strain (9R-ΔppGpp) backgrounds and tested as live vaccines in chickens. After oral inoculation, the LD(50) values of ΔppGpp and 9R-ΔppGpp were approximately 5×10(10) colony forming unit (CFU) similarly as 9R strain, which was ∼10(5)-fold higher than that of the wildtype S. Gallinarum strain. Immunological analyses revealed immunization with either of the two attenuated ppGpp-defective strains induced significant antibody responses, the production of antibody-secreting B cells in blood, proliferation of CD4+ and CD8+ T cells in the spleen, and splenic expression of proinflammatory cytokines, such as IFN-γ and TGF-β4, at levels comparable to the 9R strain. Chickens immunized with the mutants (1×10(8) CFU) were 80% protected against oral challenge with 1×10(9) wild-type virulent bacteria (4,000-fold LD(50) dose), similar to the level of protection achieved by 9R immunization. Based on these data, live attenuated ΔppGpp-defective strains may serve as novel vaccines to control fowl typhoid in chickens.
为了预防由肠炎沙门氏菌血清型鸡白痢（S. Gallinarum）引起的鸡伤寒，减毒 9R 菌株已在田间用作疫苗。然而，由于 9R 的突变情况尚不清楚，其效力仍存在争议，因此人们对其安全性表示担忧。ppGpp 是由 RelA 和 SpoT 合成的全局调控因子，已被证明能诱导肠炎沙门氏菌（Jeong 等人，2008 年）中的各种毒力基因。在这项研究中，在野生型鸡白痢（ΔppGpp）和 9R 菌株（9R-ΔppGpp）背景下构建了两个不能合成 ppGpp 的突变株，并将其作为活疫苗在鸡中进行了测试。经口服接种后，ΔppGpp 和 9R-ΔppGpp 的 LD(50)值与 9R 菌株相似，约为 5×10(10)个菌落形成单位（CFU），比野生型鸡白痢菌株高约 10(5)倍。免疫分析显示，免疫接种两种减毒的 ppGpp 缺陷株中的任何一种，均可诱导显著的抗体反应，在血液中产生分泌抗体的 B 细胞，在脾脏中增殖 CD4+和 CD8+T 细胞，并在脾脏中表达 IFN-γ和 TGF-β4 等促炎细胞因子，其水平与 9R 菌株相当。用突变株（1×10(8)CFU）免疫的鸡对 1×10(9)野生型毒力细菌（4000 倍 LD(50)剂量）的口服攻毒有 80%的保护作用，与 9R 免疫的保护水平相似。基于这些数据，活减毒的ΔppGpp 缺陷株可能成为控制鸡伤寒的新型疫苗。
