弓形虫是一种全球分布的寄生原虫，人类感染以Ⅱ型虫株为主。自噬作为保守的细胞内溶酶体降解过程，可被先天和获得性免疫同时利用抵抗胞内病原体。我们前期发现，Ⅱ型虫株TgCDPK3表达量高于I型虫株，并和宿主自噬蛋白Atg3和Atg5相互作用，但TgCDPK3具体作用机制尚未报道。我们提出：Ⅱ型虫株可能通过TgCDPK3与Atg3和Atg5相互作用，诱导IRGs和GBPs在纳虫泡周围募集，阻止虫体免疫逃逸。为此拟开展：构建TgCDPK3基因敲除ME49株，观察敲除TgCDPK3基因对弓形虫毒力的影响；构建Atg3、Atg5缺陷细胞株，明确TgCDPK3在宿主细胞自噬中的作用及调控机制；阐明TgCDPK3通过Atg3和Atg5调控宿主细胞自噬促进IRGs和GBPs在纳虫泡周围募集。该研究拟揭示TgCDPK3在Ⅱ型虫株免疫逃逸过程中的重要地位，为阐明弓形虫感染宿主免疫机制和分子疫苗研制奠定基础。

Toxoplasma gondii (T.gondii) is a worldwide parasitic protozoan, and type Ⅱ strains of T. gondii easily establish latent infections in humans. As a conserved intracellular degradation pathway that targets cellular constituents to lysosomes, autophagy can be used by innate and acquired immunity to combat intracellular pathogens. In previous studies, we found that TgCDPK3 expressed significantly high in type Ⅱ strain compared with type Ⅰ strain and TgCDPK3 interacted with Atg3 and Atg5. But the mechanism has not been elucidated. Therefore, we assume that TgCDPK3 could induce autophagy through the interaction with Atg3 and Atg5 in type Ⅱ strain. Ultimately, The recruitment of IRGs and GBPs onto PV (parasitophorous vacuole) would prevent the parasite from immune escape. To verify this hypothesis, we will do the following studies. Firstly, we will construct TgCDPK3-deficient ME49 strain and detect the influence on both cells and animals. Secondly, we will construct Atg3-deficient and Atg5-deficient cells and explore the role of TgCDPK3 in autophagy. Finally, we will clarify that TgCDPK3 could induce autophagy and promote the recruitment of IRGs and GBPs onto PV through Atg3 and Atg5. The fulfillment of this project helps to explain the role of TgCDPK3 in the immune escape of type Ⅱ strain and lay a foundation for elucidate the host immune mechanism of toxoplasma infection and the development of vaccine.