T. cruzi immune evasion factors and vaccine design

描述（由申请人提供）：与引起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。涉及诱导免疫失调和逃避的毒力因子的识别和表征应该为开发疫苗和改进化疗药物提供关键目标。本研究重点关注克氏锥虫脯氨酸消旋酶 (TcPRAC)，它由脊椎动物阶段寄生虫分泌，是一种多克隆 B 细胞激活剂。本研究将检验以下假设：使用亚有丝分裂剂量的 TcPRAC 进行免疫将导致有丝分裂活性中和，并在受到攻击时改善对其他候选疫苗的早期病原体特异性反应。为了检验 TcPRAC 多克隆激活的中和可改善对其他靶抗原的体液反应这一假设，将在攻击模型中评估 TcPRAC 和克氏锥虫补体调节蛋白 (CRP) 疫苗组合的功效。克氏锥虫 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，但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形成的能力。为了检验中和寄生虫源性有丝分裂原可以提高宿主免疫反应功效的假设，将解决以下具体目标：1）表征重组 TcPRAC 体内的有丝分裂能力，确定亚有丝分裂剂量并分析 B 细胞亚群和多克隆反应的位置； 2) 体内克氏锥虫攻击模型中亚有丝分裂剂量 TcPRAC 的保护能力分析； 3) 测试 TcPRAC 和 CRP 疫苗组合的功效。通过免疫中和来改变克氏锥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功效，并可能为诱导多克隆反应的其他病原体的疫苗设计提供通用方法。相关性：这项研究的目标是推进恰加斯病疫苗的开发。目前，拉丁美洲有 2000 万人患有恰加斯病，另有 9000 万人面临感染病原体克氏锥虫的风险。目前还没有疫苗可以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.