BFD2 mediates inflammation, apoptosis, and pre-anxiety-like behaviors induced by acute Toxoplasma gondii infection.

Toxoplasma gondii infection induces anxiety in hosts during the chronic stage; however, its role in pre-anxiety-like behaviors during the acute stage remains poorly understood. This study investigates the role of Bradyzoite Formation Deficient 2 (BFD2), a transcription factor essential for tachyzoite-to-bradyzoite differentiation, in inflammation, apoptosis, and behavioral changes during acute T. gondii infection. Using CRISPR/Cas9-mediated gene editing, we generated a Bfd2 knockout strain (ME49∆bfd2) and observed reduced parasite proliferation and plaque formation, indicating BFD2's role in promoting T. gondii survival. RNA sequencing analysis of infected BV2 cells revealed that Bfd2 deletion significantly downregulated inflammatory responses, with reduced expression of key inflammatory markers (interleukin 1 beta ((IL-1β), interferon gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α)) during acute infection. Next, we used western blotting, real-time quantitative PCR (qPCR) and enzyme-linked immunosorbent assays (ELISAs) to verify that BFD2 improves the inflammation induced by acute stage T. gondii infection. In vivo studies confirmed that BFD2 exacerbates brain inflammation and neuronal apoptosis specifically during the acute stage, with no significant effects during the chronic stage. Behavior was assessed using the elevated plus maze test and open field test. Compared with the uninfected group and ME49∆bfd2 group, the ME49 group mice showed an increased percentage of distance in the open arms and time in the open arm. The results showed that the total distance traveled, distance in the center, and time in the center were significantly decreased in the ME49 group, and the total distance traveled (mm) had no significant changes in the ME49∆bfd2. These demonstrated that BFD2 contributes to pre-anxiety-like behaviors in mice during acute stage T. gondii infection. These findings highlight BFD2 as a critical regulator of acute-stage inflammation, neuronal damage, and behavioral alterations, providing insights to develop targeted interventions against T. gondii infection.