State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong-Dia-Jie Street, Fengtai, Beijing 100071, China.
Vaccine. 2013 Nov 19;31(48):5643-50. doi: 10.1016/j.vaccine.2013.09.064. Epub 2013 Oct 8.
Surface proteins YbgF and PrsA are major seroreactive antigens of Rickettsia heilongjiangensis, the etiological agent of Far-Eastern spotted fever. This study investigated their potential immunogenicity for protective immunity.
Recombinant YbgF and PrsA were used to immunize C3H/HeN mice and rickettsial loads in immunized mouse organs were assessed after R. heilongjiangensis challenge. Anti-sera from immunized mice were applied to neutralize rickettsiae. CD4⁺ and CD8⁺ T cells isolated from R. heilongjiangensis-infected mice were stimulated with YbgF or PrsA, and proliferation and cytokine production assessed.
The IgG2a/IgG1 ratio of sera was markedly increased in YbgF-immunized mice but was unaltered in PrsA-immunized mice after immunization. The rickettsial load in YbgF-immunized mice was significantly lower than in PrsA-immunized mice after R. heilongjiangensis challenge. Incubation with anti-serum to YbgF, but not PrsA, significantly reduced the number of rickettsiae adhering to and invading endothelial cells. The proliferation level and tumor necrosis factor-α secretion level of CD4⁺ T cells from R. heilongjiangensis-infected mice were significantly higher than in uninfected mice after stimulation with YbgF but not PrsA.
YbgF is a novel protective antigen that induces a Th1-type of protective immune response against R. heilongjiangensis infection.
YbgF 和 PrsA 表面蛋白是黑龙江立克次体（远东斑疹热的病原体）的主要血清反应性抗原。本研究探讨了它们作为保护性免疫原的潜力。
用重组 YbgF 和 PrsA 免疫 C3H/HeN 小鼠，在黑龙江立克次体攻毒后评估免疫小鼠器官中的立克次体负荷。用免疫血清中和立克次体。用 YbgF 或 PrsA 刺激从黑龙江立克次体感染的小鼠中分离出的 CD4⁺和 CD8⁺T 细胞，评估增殖和细胞因子产生情况。
YbgF 免疫小鼠的 IgG2a/IgG1 比值在免疫后明显升高，而 PrsA 免疫小鼠则不变。黑龙江立克次体攻毒后，YbgF 免疫小鼠的立克次体负荷明显低于 PrsA 免疫小鼠。用抗 YbgF 血清孵育，但不用抗 PrsA 血清孵育，显著减少了附着和侵入内皮细胞的立克次体数量。与未感染小鼠相比，用 YbgF 刺激感染黑龙江立克次体的小鼠的 CD4⁺T 细胞的增殖水平和肿瘤坏死因子-α分泌水平明显更高，但用 PrsA 刺激则不然。
YbgF 是一种新的保护性抗原，可诱导针对黑龙江立克次体感染的 Th1 型保护性免疫反应。
