Abstract T. gondii is a globally prevalent intracellular parasite that poses significant public health challenges. However, its virulence mechanisms remain poorly understood. Here, we identified cleft lip and palate transmembrane protein 1 (CLPTM1, TGME49₂05240) as a critical virulence factor and systematically characterized its role. The CLPTM1 deletion strain (Δclptm1) grows normally in vitro but completely loses virulence in vivo, with 100% survival of infected mice and no brain cyst formation. Serum IL-6 levels and tissue pathology in major organs were significantly reduced in Δclptm1 -infected mice, indicating attenuated systemic inflammation and tissue damage. Transcriptomic analysis revealed that Δclptm1 infection markedly downregulated key chemokine genes (CCL5, CCR7 and CCL22) in macrophages. This trend was further supported by the reduced expression of these chemokines and decreased F4/80⁺ macrophage infiltration in liver and lung tissues. Concomitantly, diminished phosphorylation of IκB-α, along with decreased levels of p65 and its activated form pp65, suggests that CLPTM1 promotes chemokine expression by facilitating the activation of the NF-κB signaling pathway. Consistently, pp65 expression in liver and lung tissues was markedly reduced in the Δclptm1 -infected group. Here, we delineate a mechanistic axis whereby CLPTM1 influences T. gondii virulence through the activation of the host NF-κB/chemokine/macrophage pathway, thereby promoting inflammation and immune cell infiltration. This study provides new insight into T. gondii pathogenesis and lays a foundation for the future development of diagnostic, therapeutic, and vaccine strategies against toxoplasmosis.
He et al. (Mon,) studied this question.