A Novel Gene of Inhibits the Parasitic Invasion and Proliferation and Attenuates Virulence via Immune Response Modulation.

() is an obligate intracellular apicomplexan protozoan that can parasitize most warm-blooded animals and cause severe diseases in immunocompromised individuals or fetal abnormalities in pregnant woman. The treatment of toxoplamosis has been limited by effective drugs. Our previous work indicated that the novel gene of may serve as a vaccine antigen candidate. To further investigate the molecular functions of in highly virulent (RH strain), a gene deletion mutant RH strain (KO-) was established using CRISPR-Cas9. The phynotype of KO- was analyzed by plaque, invasion, and replication assays as well as virulence assays. The results indicated that the targeted deletion of the gene significantly inhibited parasite growth and replication in the host cells as well as attenuated parasite virulence in the mouse model. Notably, the percentage of pro-inflammatory factors of interferon gamma (IFN-γ) and interlukin-17A (IL-17A) and anti-inflammatory factor of interlukin-10 (IL-10) in the lymph nodes were upregulated in mice infected with the KO- strain. Our data suggested that the gene plays an important role in the process of the parasite's life cycle and virulence in mice. In addition, it also plays an important role in the host's immunity reaction, mainly via Th1 and Th17 cellular immunity, not Th2.