Development of novel, safe and efficacious Coxiella burnetii vaccine

 描述(申请人提供)：虽然Q热首次被诊断是在近80年前，但仍然没有一种有效的疫苗可以长期预防伯氏梭菌感染，并且对于反复加强接种是安全的。我们已经确定，仅有CD4或CD8T细胞(没有B细胞)就足以保护机体免受伯氏杆菌毒力I期的侵袭，而且CD8T细胞的反应与组织损伤程度较低有关。其他研究表明，针对伯氏梭菌内毒素I期的抗体可能也是有效的，应该在任何新的疫苗配方中加以考虑。已知的第一阶段伯氏梭菌脂多糖对其受体TLR4和人类对伯氏梭菌的下游免疫反应有不同的影响，从而降低了小鼠作为人类Q热模型的实用性。为了克服小鼠的这一缺陷，我们将利用hTLR4/MD2转基因小鼠模型(表达人TLR4/MD2)，我们最近表明，这种模型比野生型小鼠更容易受到低剂量的伯氏弧菌感染。这只新的小鼠将使我们能够更好地分析体内对伯氏梭菌内毒素I期的反应及其作为疫苗抗原的用途。为了开发一种新的Q热疫苗，我们计划使用一种新型的递送平台，使用P22病毒样颗粒(P22 VLP)，即使在缺乏特定抗原的情况下也能诱导佐剂样反应，以非特异性地保护小鼠免受不同病毒和细菌病原体的攻击，并将与这些病原体相关的组织发病率降至最低。P22 VLP可以被独特地设计成在内表面和外表面表达抗原，我们已经证明这会分别导致保护性CD8T细胞和B细胞反应的选择性增强。具体地说，我们的初步结果表明，P22 VLP可以被改造成有效地诱导抗原特异性的非破坏性免疫反应，从而满足可许可的伯氏弧菌疫苗的要求。因此，我们假设VLP可以被设计成产生一种有效的伯氏弧菌疫苗，该疫苗仅在肺部局部诱导保护性和非破坏性的适应性免疫反应(如CD8T细胞和抗体反应)。由于VLP引起的免疫反应的非破坏性性质，我们进一步假设该疫苗对于重复给药是安全的。为了验证这一假设，我们将追求以下具体目标。目的1)构建一种可诱导CD8 T细胞介导保护作用的VLP载体。这将通过鉴定伯氏梭菌免疫优势CD8 T细胞表位来完成，该表位将在P22 VLP的内表面表达。目的2)构建能诱导抗内毒素抗体介导的保护性免疫反应的VLP载体。在人源化的TLR4/MD2小鼠中，将确定VLP递送的I期伯氏杆菌脂多糖的疗效，该疫苗构建在P22 VLP的内部表达免疫优势CD8 T细胞表位，而相同VLP的外部表达LPS。

 DESCRIPTION (provided by applicant): Although Q fever was first diagnosed nearly 80 years ago; an efficacious vaccine that provides long- term protection from C. burnetii infection and is safe for repeated booster administrations is still unavailable. We have determined that either CD4 or CD8 T cells alone (without B cells) are sufficient for protection from virulent phase I C. burnetii and that the CD8 T cell response is associated with less deleterious tissue damage. Others have shown that antibodies to phase I C. burnetii LPS may be efficacious as well, and should be considered in any new vaccine formulation. Phase I C. burnetii LPS is known to differently affect its receptor, TLR4, and the downstream immune responses to C. burnetii in mice and humans, diminishing the utility of mice as a model of Q fever in humans. To overcome this deficiency in mice, we will utilize an hTLR4/MD2 transgenic mouse model (expressing human TLR4/MD2), which we have recently shown is more susceptible than wildtype mice to low dose C. burnetii infection. This new mouse will allow us to better analyze the in vivo response to phase I C. burnetii LPS and its utility as a vaccine antigen. To develop a new vaccine for Q fever, we plan on using a novel delivery platform that uses P22 virus-like particles (P22 VLPs), which even in the absence of specific antigen induce adjuvant-like responses that nonspecifically protect mice from different viral and bacterial pathogens and minimize tissue morbidity associated with these pathogens. The P22 VLP can be uniquely engineered to express antigens on both the internal and external surfaces, which we have shown leads to selective enhancement of protective CD8 T cell and B cell responses, respectively. Specifically, our preliminary results suggest that P22 VLPs can be engineered to effectively induce antigen-specific non-damaging immune responses that could accommodate the requirements for a licensable C. burnetii vaccine. Thus, we hypothesize that VLPs can be engineered to generate an effective C. burnetii vaccine that induces only the protective and non-damaging adaptive immune responses (such as both CD8 T cell and antibody responses) locally in the lungs. Due to the non-damaging nature of the immune response elicited by the VLPs, we further hypothesize that this vaccine will be safe for repeatable administration. To test this hypothesis, we will pursue the following Specific Aims. Aim 1) Generate a VLP construct that induces CD8 T cell-mediated protection. This will be done by identification of C. burnetii immunodominant CD8 T cell epitopes that will be expressed on the internal surface of the P22 VLPs. Aim 2) Generate a VLP construct that induces anti-LPS antibody-mediated protection. The efficacy of VLP-delivered phase I C. burnetii LPS will be determined in humanized TLR4/MD2 mice immunized with VLP constructs expressing immunodominant CD8 T cell epitopes on the inside of the P22 VLPs and LPS on the outside of the same VLPs.