Transmission-blocking live vaccine for Chagas disease

描述(申请人提供)：到目前为止，人类寄生虫病疫苗的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，以及对它们所使用的有效宿主免疫反应和免疫逃避机制的相对缺乏了解。在许多地方，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，这意味着为狗和猫接种疫苗，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。我们建议建立克鲁兹毛滴虫的无毒株系，并将其作为疫苗进行评估，以防止克鲁兹毛滴虫从同伴或家畜向昆虫传播。利用克氏毛滴虫基因的特异性缺失，我们将培育无毒品系，选择它们作为上鞭毛虫生长良好的能力，并转化为具有感染性的准环类鞭毛虫，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，最终防止小鼠和狗在攻击强毒寄生虫系后出现可检测到的寄生虫血症。我们将优化基因敲除(KO)无毒株系，通过过度表达编码非变异的克氏锥虫蛋白的低拷贝基因，以及通过表达和分泌细菌中的异源蛋白TLR配体来提高它们的效力和安全性。这些修饰有望加速和加强对克氏锥虫的免疫反应。这种方法的一个诱人方面是，同伴动物的疫苗不必绝对防止感染--只需将这些动物血液中的寄生虫水平保持在向昆虫传播的水平以下即可。此外，这种疫苗可以以口服形式提供--使动物的广泛接种变得非常容易。

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.