Toxoplasma sporozoite genes that determine environmental resistance and invasion of host cells.

项目摘要 弓形虫寄生虫可在免疫功能低下的患者和胎儿中引起严重疾病， 是美国食源性死亡的第二大原因。感染始于摄入排出的卵囊。 猫的粪便或在摄入被组织囊污染的肉类后。卵囊在人体内非常稳定 环境，抵抗大多数灭活程序，并具有高度传染性。因为家畜会得到 感染来自卵囊的子孢子，基于子孢子或子孢子蛋白的疫苗可能是 有效地保护牲畜和人类。目前，唯一可用的疫苗是减毒活疫苗。 仅被批准用于绵羊。然而，这种疫苗作为该病的遗传基础存在严重缺陷。 衰减是未知的，这会带来恢复风险，一旦产生，就需要立即使用 因为它是以活的速殖子为基础的，而活的速殖子不能长时间在宿主细胞外生存。尽管是一个批评者 弓形虫传播的步骤，卵囊内的子孢子研究不足，主要是因为它们不是 可以在体外培养，在体内很难获得。因此，迫切需要鉴定子孢子基因。 对其入侵宿主细胞至关重要的产品，这可能导致发现疫苗靶标。 此外，如果知道子孢子对极端环境的抵抗力的遗传基础，它可能会 有可能利用这一点来使其他弓形虫生命阶段，如速殖子或其他病原体 活的细胞外，这可以延长基于活寄生虫的疫苗的保质期。我们的整体 目的是确定弓形虫特异参与环境抗性的基因和 子孢子的传染性。我们的中心假设是：1)子孢子特异的微线蛋白(MIC) 是它们入侵宿主细胞的关键；2)晚期胚胎发生丰富蛋白(LEA)，已知 在各种植物中提供对干旱、高盐度和冰冻等环境胁迫的抵抗力 生物，确定子孢子对环境应激源的抵抗力。在我们的第一个目标中，我们将确定 LEAs在保护子孢子免受环境胁迫中的作用。在我们的第二个目标中，我们将测试 假设在子孢子中特异表达的MIC参与宿主细胞的入侵。 与细胞外存活和宿主附着/入侵有关的子孢子基因的鉴定 细胞，将为设计能够预防弓形虫感染人和动物的疫苗铺平道路。

Project Summary The parasite Toxoplasma gondii can cause severe disease in immunocompromised patients and fetuses and is the second leading cause of foodborne deaths in the USA. Infection starts after ingestion of oocysts shed in cat feces or after ingestion of meat contaminated with tissue cysts. Oocysts are extremely stable in the environment, resistant to the most inactivation procedures, and highly infectious. Because livestock get infected by sporozoites derived from oocysts, a vaccine based on sporozoites or sporozoite proteins could be effective in protecting livestock and humans. Currently, the only vaccine available is a live attenuated vaccine only approved for use in sheep. However, this vaccine has serious shortcomings as the genetic basis for the attenuation is not known, which poses reversion risks, and it needs to be used immediately once produced because it is based on live tachyzoites, which are not viable for long outside host cells. Despite being a critical step for Toxoplasma transmission, sporozoites inside oocysts are under-studied, largely because they are not cultivatable in vitro and difficult to access in vivo. There is, therefore, a critical need to identify sporozoite gene products that are critical for its invasion of host cells, which could lead to the discovery of vaccine targets. Furthermore, if the genetic basis for the extreme environmental resistance of sporozoites was known it might be possible to exploit this to make other Toxoplasma life stages, such as tachyzoites, or other pathogens more viable extracellularly, which could enhance the shelf-life of vaccines based on live parasites. Our overall objectives are to identify Toxoplasma genes that are specifically involved in the environmental resistance and infectivity of sporozoites. Our central hypotheses are that 1) sporozoite-specific micronemal proteins (MICs) are critical for their invasion into host cells; 2) late embryogenesis abundant proteins (LEAs), which are known to provide resistance to environmental stresses such as drought, high salinity, and freezing in a variety of organisms, determine sporozoite resistance to environmental stressors. In our first aim we will determine the role of LEAs in the protection of sporozoites against environmental stressors. In our second aim we will test the hypothesis that MICs that are specifically expressed in sporozoites are involved in the invasion of host cells. The identification of sporozoite genes that play a role in extracellular survival and attachment/invasion of host cells, will pave the way for designing vaccines that can prevent Toxoplasma infection of humans and animals.