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

在之前的资助期内，发现了几种有可能引起CD4+ T细胞反应的伤寒立克次体抗原，也可能引起CD8+ T细胞和B细胞反应。这些抗原中的大多数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。重新刺激斑疹伤寒感染小鼠和患者血液中的CD4+和CD8+ T细胞，将揭示在感染斑疹伤寒的小鼠和人类中，哪些抗原实际上产生了T细胞和B细胞反应。在这种情况下，将详细分析T细胞反应，特别是关于细胞因子的产生、增殖和激活标记物的表达。针对这些抗原的抗体的产生也将被研究，T细胞和B细胞的表位将被确定。在这项工作的背景下，对其他立克次体，特别是普拉兹氏立克体可能的交叉反应性也将进行研究。为此，将小鼠感染proproazekii，并按照描述分析对重组抗原的免疫反应。在感染小鼠和患者的免疫细胞的再刺激中发现具有免疫优势的抗原、蛋白片段或表位将进一步用于小鼠的免疫，并使用上述方法研究诱导T和B细胞反应。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，并过继地转移到感染斑疹伤寒的高度易感的BALB/c CB17 SCID小鼠中，以测试其保护作用。计划中的工作将揭示伤寒致病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。即将到来的资助期也将首次为研究患者血细胞的反应提供机会，从而也可以测试它们与人类对斑疹伤寒的免疫反应的相关性。这将提示抗原是否也可作为人类有效的候选疫苗。B细胞识别的抗原是开发新诊断方法的另一个有趣的工具，这些方法仍然受到严重限制。这些抗原可用于免疫印迹法和酶联免疫吸附法的诊断。

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.