State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20# Dong-Dia-Jie Street, Fengtai, Beijing 100071, China.
State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20# Dong-Dia-Jie Street, Fengtai, Beijing 100071, China; Army Tuberculosis Prevention and Control Key Laboratory/Beijing Key Laboratory of New Techniques of Tuberculosis Diagnosis and Treatment, Institute for Tuberculosis Research, The 309th Hospital of Chinese PLA, 17# Hei-Shan-Hu Road, Haidian, Beijing 100091, China.
Vaccine. 2017 Dec 18;35(51):7204-7212. doi: 10.1016/j.vaccine.2017.09.068. Epub 2017 Oct 10.
Rickettsia rickettsii is the causative pathogen of Rocky Mountain spotted fever (RMSF). Adr2, YbgF and OmpB are protective antigens of R. rickettsii. In this study, 90 candidate peptides were selected from these antigens based on their high-affinity binding capacity for the MHC class II molecule H2 I-A or H2 I-E using bioinformatic methods. Six peptides were determined using ELISPOT assay to be immunodominant based on the IFN-γ recall responses of CD4 T cells from mice immunized with R. rickettsii. Six nucleotide sequences encoding the immunodominant peptides were linked in series and inserted into a plasmid for expression in Escherichia coli cells, resulting in a new, recombinant polypeptide termed GWP. After immunization and challenge, the rickettsial load or histopathological lesions in the organs of mice immunized with GWP or pooled peptides was significantly lower than that in organs of mice immunized with PBS or the individual peptide OmpB. An in vitro neutralization test revealed that sera from mice immunized with GWP, OmpB, or pooled peptides reduced R. rickettsii adherence to, and invasion of, vascular endothelial cells. Furthermore, significantly higher levels of IgG, IgG1, or IgG2a were detected in sera from mice immunized with GWP or pooled peptides, and significantly higher levels of IFN-γ or TNF-α secreted by CD4 T cells from R. rickettsii-infected mice were detected after immunization with GWP. Altogether, our results indicated that polypeptides, especially GWP, could induce a Th1-type immune response against R. rickettsii infection, which might contribute to the rational design of peptide-based vaccines for RMSF.
恙虫病东方体是落矶山斑点热（RMSF）的病原体。Adr2、YbgF 和 OmpB 是恙虫病东方体的保护性抗原。在这项研究中，我们使用生物信息学方法从这些抗原中选择了 90 个候选肽段，基于它们与 MHC Ⅱ类分子 H2 I-A 或 H2 I-E 的高亲和力结合能力。通过 ELISPOT 试验，我们确定了 6 个肽段，这些肽段是根据用 R. rickettsii 免疫的小鼠 CD4 T 细胞的 IFN-γ回忆反应来确定的，这些肽段具有免疫优势。6 个编码免疫优势肽段的核苷酸序列被串联起来并插入质粒中，在大肠杆菌细胞中表达，得到一个新的重组多肽，称为 GWP。免疫和攻毒后，与用 PBS 或单个肽段 OmpB 免疫的小鼠相比，用 GWP 或混合肽段免疫的小鼠的恙虫病负荷或器官的组织病理学损伤明显降低。体外中和试验显示，用 GWP、OmpB 或混合肽段免疫的小鼠的血清降低了 R. rickettsii 对血管内皮细胞的黏附和侵袭。此外，与用 OmpB 或混合肽段免疫的小鼠相比，用 GWP 免疫的小鼠血清中 IgG、IgG1 或 IgG2a 的水平显著升高，用 GWP 免疫后，从感染 R. rickettsii 的小鼠中分离出的 CD4 T 细胞分泌的 IFN-γ或 TNF-α水平也显著升高。总之，我们的结果表明，多肽，尤其是 GWP，可诱导针对 R. rickettsii 感染的 Th1 型免疫应答，这可能有助于合理设计 RMSF 的基于肽的疫苗。
