Biphasic Regulation of TLR7 / MyD88 / IRF7 ‐ IFN ‐β Axis by Toxoplasma gondii Facilitates Immune Evasion

ABSTRACT Toxoplasma gondii ( T. gondii ) is a remarkably successful intracellular parasite, largely because of its ability to manipulate host immune response. Toll‐like receptor 7 (TLR7), a sensor for single‐stranded RNA, plays a crucial role in resistance to viral infections, but its function during T. gondii infection remains unclear. In this study, we investigated the role and regulation of the TLR7/MyD88/IRF7 signaling pathway during T. gondii infection. RNA‐seq, qRT‐PCR, and Western blot analyses revealed significant downregulation of Tlr7 expression in RAW264.7 cells at 24 h post‐infection (hpi). Additionally, treatment with the TLR7 agonist imiquimod suppressed T. gondii proliferation in vitro and prolonged survival in infected mice. Time‐course analysis uncovered a biphasic regulation of the TLR7/MyD88/IRF7 pathway: during the early infection phase (8 hpi in vitro or 12 hpi in vivo), these components were rapidly upregulated, along with a significant increase in IFN‐β mRNA levels. However, as the infection progressed (12–24 hpi in vitro or 24–96 hpi in vivo), the expression of these pathway components and IFN‐β declined. Crucially, siRNA‐mediated knockdown of Tlr7 abolished this biphasic regulation and significantly suppressed downstream Irf7 and Ifnb1 expression, establishing TLR7 as essential for pathway activation and IFN‐β induction. This biphasic regulation of the pathway by T. gondii in RAW264.7 cells has not been previously reported. This study helps elucidate the role of Toll‐like receptors during T. gondii infection of the host and provides a new strategy for the treatment of T. gondii .