Transmission-blocking live vaccine for Chagas disease

描述（由申请人提供）：迄今为止，人类寄生虫病的疫苗开发尚未取得丰硕成果，部分原因是这些真核病原体的遗传复杂性，以及相对缺乏对宿主有效免疫反应的了解，以及它们使用的免疫逃避机制。在许多地点，克氏锥虫对昆虫的传播——以及随后对人的传播——几乎完全取决于家中是否有感染克氏锥虫的狗或猫。从逻辑上讲，这意味着给狗和猫接种疫苗，使它们不会感染细菌，这可能是预防人类感染的一种非常有效的工具。我们建议开发克氏锥虫的无毒系，并评价其作为预防克氏锥虫从同伴或家畜传播给昆虫的疫苗。利用克氏T. cruzi基因的特异性缺失，我们将开发无毒的系，选择它们生长良好的能力，并转化为感染性的亚环锥乳鞭毛虫，在体外感染细胞系，在小鼠体内诱导强烈的T细胞和抗体反应，最终，在小鼠和狗体内防止发生可检测的寄生虫血症。我们将优化基因敲除（KO）无毒系，通过过表达编码非变异克氏t细胞蛋白的低拷贝基因以及从细菌中表达和分泌外源蛋白TLR配体来提高其效力和安全性。这些修饰有望加速和增强对克氏锥虫的免疫反应。这种方法的诱人之处在于，伴侣动物的疫苗不必绝对预防感染——只需将这些动物血液中的寄生虫水平控制在昆虫传播水平以下即可。此外，这种疫苗可以口服形式，使动物的广泛接种变得相当容易。

DESCRIPTION (provided by applicant): Vaccine development for human parasitic diseases has not been a fruitful endeavor to date, in part due to the genetic complexity of these eukaryotic pathogens and the relative lack of understanding of effective host immune responses to, and immune evasion mechanisms used by them. In many sites, the transmission of Trypanosoma cruzi to insects - and subsequently to the people - is nearly totally determined by the presence or absence of T. cruzi infected dogs or cats in the home. Logistically what this means is that vaccination of dogs and cats so that they are not infectious to bugs could be a highly effective tool for the prevention human infections. We propose the development of avirulent lines of T. cruzi and their evaluation as vaccines to prevent the transmission of T. cruzi from companion or livestock animals to insects. Using the specific deletion of T. cruzi genes we will develop avirulent lines, selecting for their ability to grow well as epimastigotes and to convert to infective metacyclic trypomastigotes, to infect cells lines in vitro, to induce strong T cell and antibody responses in vivo in mice and ultimately, to prevent the development of detectable parasitemia in mice and dogs following challenge with virulent parasite lines. We will optimize the gene knockout (KO) avirulent lines to enhance their potency and safety by overexpression of low copy genes encoding non-variant T. cruzi proteins as well as by the expression and secretion of the heterologous protein TLR ligands from bacteria. These modifications are expected to accelerate and potentiate the immune response to T. cruzi. Among the enticing aspects of this approach is that a vaccine for companion animals would not have to absolutely prevent infection - just keep parasite levels in the blood of these animals below the level of transmissibility to insects. Additionally, such a vaccine could be delivered in an oral form - making widespread vaccination of animals quite easy.