T. cruzi immune evasion factors and vaccine design

描述（由申请人提供）：与其他引起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。对诱导免疫失调和逃避的毒力因素的识别和表征，应成为开发疫苗和改进化疗的关键靶点。克氏T. proline消旋酶（TcPRAC）是一种多克隆B细胞激活剂，由脊椎动物阶段寄生虫分泌。本研究将验证以下假设：亚有丝分裂剂量的TcPRAC免疫将导致有丝分裂活性的中和，并在挑战时改善对其他候选疫苗的早期病原体特异性反应。为了验证TcPRAC多克隆活化的中和导致对其他靶抗原的体液反应改善的假设，将在一个挑战模型中评估TcPRAC和克氏T.补体调节蛋白（CRP）联合疫苗的效果。克氏T. CRP是一种表面蛋白，参与逃避替代和经典补体激活，从而促进寄生虫的早期血行传播。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延迟了对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疾病的能力。为了验证寄生虫来源的有丝分裂原中和可以提高宿主免疫应答的功效，我们将研究以下具体目标：1)在体内表征重组TcPRAC的有丝分裂能力，确定亚有丝分裂剂量，分析B细胞亚群和多克隆应答的位置；2)亚有丝分裂剂量TcPRAC对体内克氏t细胞攻击模型的保护能力分析；3)检验TcPRAC与CRP联合疫苗的疗效。通过免疫中和改变克氏锥虫丝裂原诱导的免疫失调的新尝试可能会提高该模型中其他候选疫苗的功效，并可能为其他诱导多克隆反应的病原体的疫苗设计提供一般方法。相关性：这项研究的目标是促进恰加斯病疫苗的开发。恰加斯病目前折磨着拉丁美洲的2000万人，另有9000万人面临感染病原体克氏锥虫的风险。目前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.