T. cruzi immune evasion factors and vaccine design

描述(申请人提供)：与其他建立慢性感染的病原体一样，克氏锥虫的免疫逃避策略可能导致宿主无法控制和清除感染。对导致免疫失调和逃避的毒力因子的鉴定和表征应导致疫苗和改进化疗药物开发的关键目标。本研究以脊椎动物阶段寄生虫分泌的多克隆B细胞激活剂--克鲁兹旋毛虫的脯氨酸消旋酶(TcPRAC)为研究对象。这项研究将检验这样的假设，即亚有丝分裂原剂量的TcPRAC免疫将导致有丝分裂活性的中和，并改善挑战时对其他候选疫苗的早期病原体特异性反应。为了验证中和TcPRAC多克隆激活导致对其他靶抗原的体液反应改善的假设，将在挑战模型中评估TcPRAC和TcPRAC补体调节蛋白(CRP)的疫苗组合的有效性。克鲁兹毛滴虫CRP是一种表面蛋白，参与逃避替代的和经典的补体激活，从而促进寄生虫的早期血源性传播。其他研究表明，CRP是一种有效的候选疫苗，然而对寄生虫攻击的非特异性多克隆反应会延迟对CRP和其他候选疫苗的抗原特异性反应，从而限制了这些疫苗预防或改善慢性病的能力。为了验证中和寄生虫来源的有丝分裂原可以提高宿主免疫反应有效性的假设，将解决以下具体目标：1)体内重组TcPRAC的有丝分裂能力的表征，亚有丝分裂剂量的测定，并分析B细胞亚群和多克隆反应的位置；2)在体内TcPRAC攻击模型中分析亚有丝分裂剂量的保护能力；3)测试TcPRAC和CRP疫苗组合的有效性。通过免疫中和改变克氏毛滴虫有丝分裂原诱导的免疫失调的新尝试可能会增强该模型中其他候选疫苗的效力，并可能为其他诱导多克隆反应的病原体提供一种通用的疫苗设计方法。相关性：这项研究的目标是推进恰加斯病疫苗的开发。恰加斯病目前困扰着拉丁美洲的2000万人，另有9000万人面临感染克氏锥虫的风险，克氏锥虫是一种病原体。目前还没有疫苗可用于预防或治疗恰加斯病，拟议的研究将在实验模型中测试两种候选疫苗。

DESCRIPTION (provided by applicant): As with other pathogens that establish chronic infections, immune evasion strategies of Trypanosoma cruzi likely contribute to the failure of the host to control and clear the infection. The identification and characterization of virulence factors involved in inducing immune dysregulation and evasion should lead to critical targets for the development of vaccines and improved chemotherapeutics. This study focuses on T. cruzi proline racemase (TcPRAC), which is secreted by vertebrate stage parasites and is a polyclonal B cell activator. This study will test the hypothesis that the immunization with sub- mitogenic doses of TcPRAC will result in neutralization of the mitogenic activity and improve early pathogen-specific responses to other vaccine candidates upon challenge. To test the hypothesis that neutralization of TcPRAC polyclonal activation leads to improved humoral response to other target antigens, the efficacy of a vaccine combination of TcPRAC and the T. cruzi complement regulatory protein (CRP) will be evaluated in a challenge model. The T. cruzi CRP is a surface protein involved in evasion of the alternative and classical complement activation, thus facilitating early hematogenous spread of the parasites. Other studies have shown CRP to be an effective vaccine candidate, however non-specific polyclonal responses to parasite challenge delay antigen- specific responses to the CRP and other vaccine candidates, thus limiting the capacity of these vaccines to prevent or ameliorate the establishment of chronic disease. To test the hypothesis that neutralization of a parasite-derived mitogen can improve the efficacy of host immune responses, the following Specific Aims will be addressed: 1) Characterization of the mitogenic capacity of recombinant TcPRAC in vivo, determination of sub-mitogenic doses and analyze B cell subsets and the location of the polyclonal response; 2) Analysis of the protective capacity of sub-mitogenic doses of TcPRAC in an in vivo T. cruzi challenge model; 3) Test the efficacy a TcPRAC and CRP vaccine combination. The novel attempt to alter the immune dysregulation induced by the T. cruzi mitogen by immunologic neutralization may enhance the efficacy of other vaccine candidates in this model and may offer a general approach to vaccine design for other pathogens that induce polyclonal responses. Relevance: The goals of this research is to advance development of a vaccine for Chagas' disease. Chagas' disease currently afflicts 20 million people in Latin America and another 90 million people are at risk of infection with Trypanosoma cruzi, the causative agent. No vaccine is currently available to prevent or treat Chagas' disease and the proposed studies will test two vaccine candidates in experimental models.