Identification of immunodominant CD4+ T cell antigens as vaccine candidates for protection against the infection with Rickettsia typhi and characterization of the Rickettsia typhi-specific CD8+ T cell response

在前一次资助期间，立克次体的几种抗原。伤寒沙门氏菌被鉴定出有可能引起CD4+T细胞反应，也可能引起CD8+T细胞和B细胞反应。这些抗原中的大部分已经被克隆和重组表达。现在将测试这些重组蛋白的免疫原性及其作为疫苗的潜在用途。对感染伤寒杆菌的小鼠和患者血液中的CD4+和CD8+T细胞进行重新刺激，将揭示哪些抗原在感染这种病原体的小鼠和人类中真正产生T和B细胞反应。在此背景下，将详细分析T细胞的反应，特别是关于细胞因子的产生、增殖和激活标志物的表达。还将调查针对这些抗原的抗体的产生，并确定T和B细胞表位。在这项工作的背景下，还将研究与其他立克次体，特别是普氏立克次体的可能交叉反应。为此，小鼠将感染普罗瓦泽克弧菌，并对重组抗原的免疫反应进行分析，如所述。那些在感染小鼠和患者的免疫细胞的再刺激中具有免疫优势的抗原、蛋白质片段或表位将进一步用于小鼠的免疫，并将使用上述方法研究诱导T和B细胞反应的情况。如果免疫成功，将从免疫小鼠中分离出活化的CD4+和CD8+T细胞，并过继转移到感染伤寒杆菌的BALB/c CB17 SCID小鼠中，以测试其保护作用。这项计划中的工作将揭示伤寒杆菌的哪些抗原可以诱导保护性免疫反应，从而代表候选疫苗。即将到来的资助期还将首次提供研究患者血细胞反应的机会，以便也可以测试它们与人类对伤寒杆菌的免疫反应的相关性。这将给出一种抗原是否也可以作为疫苗候选在人类身上有效的迹象。B细胞识别的抗原是开发新的诊断方法的另一个有趣的工具，但这些方法仍然受到严重限制。这些抗原可用于免疫印迹和酶联免疫吸附试验的诊断。

During the previous funding period, several antigens of Rickettsia (R.) typhi were identified that have the potential to elicit a CD4+ T cell response, possibly also CD8+ T cell and B cell responses. Most of these antigens have already been cloned and recombinantly expressed. The immunogenicity of these recombinant proteins and their potential use as vaccines will now be tested. Restimulation of CD4+ and CD8+ T cells from R. typhi-infected mice and from the blood of patients will reveal which antigens actually generate a T and B cell response in mouse and human infection with this pathogen. In this context, the T cell response will be analyzed in detail, in particular with regard to the production of cytokines, proliferation and the expression of activation markers. The production of antibodies against these antigens will also be investigated and T and B cell epitopes will be determined. In the context of this work, a possible cross-reactivity towards other rickettsiae, in particular R. prowazekii, will also be examined. For this purpose, mice will be infected with R. prowazekii and the immune response against the recombinant antigens will be analyzed as described. Those antigens, protein fragments or epitopes that are found to be immunodominant in the restimulation of immune cells from infected mice and patients will be further used for immunization of mice and the induction of a T and B cell response will be investigated using the above methods. If immunization is successful, activated CD4+ and CD8+ T cells will be isolated from the immunized mice and adoptively transferred into R. typhi-infected BALB/c CB17 SCID mice that are highly susceptible to infection with this pathogen to test their protective effects. The planned work will reveal which antigens of R. typhi can induce a protective immune response and thus represent candidate vaccines. For the first time, the upcoming funding period will also provide the opportunity to study the response of blood cells from patients, so that their relevance to the human immune response to R. typhi can also be tested. This will give an indication whether an antigen can also be effective as a vaccine candidate in humans. Antigens that are recognized by B cells are further interesting tools for developing new diagnostic methods that are still severely limited. Those antigens could be used for the development of diagnostic by Western blotting and ELISA.