T. cruzi immune evasion factors and vaccine design

描述（由申请方提供）：与建立慢性感染的其他病原体一样，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。参与诱导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的化学治疗剂的开发的关键目标。本研究以T. cruzi脯氨酸消旋酶（TcPRAC），其由脊椎动物阶段寄生虫分泌并且是多克隆B细胞活化剂。本研究将检验以下假设：用亚促有丝分裂剂量的TcPRAC免疫接种将导致促有丝分裂活性的中和，并改善攻毒后对其他候选疫苗的早期病原体特异性应答。为了检验TcPRAC多克隆活化的中和导致对其它靶抗原的体液应答改善的假设，TcPRAC和T. cruzi补体调节蛋白（CRP）将在激发模型中进行评价。霸王cruziCRP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。其他研究已经显示CRP是有效的候选疫苗，然而，对寄生虫攻击的非特异性多克隆应答延迟了对CRP和其他候选疫苗的抗原特异性应答，从而限制了这些疫苗预防或改善慢性疾病形成的能力。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应答效力的假设，将解决以下具体目的：1）表征重组TcPRAC体内促有丝分裂能力，确定亚促有丝分裂剂量，分析B细胞亚群和多克隆应答的位置; 2）亚促有丝分裂剂量的TcPRAC在体内T. cruzi攻击模型; 3）测试TcPRAC和CRP疫苗组合的功效。本实验是改变T.通过免疫中和的Cruzi有丝分裂原可以增强该模型中其他候选疫苗的效力，并且可以为诱导多克隆应答的其他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南美锥虫病疫苗的开发。南美锥虫病目前在拉丁美洲影响着2 000万人，另有9 000万人面临感染致病因子克氏锥虫的风险。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.