T. gondii CLPTM1 enhances in vivo virulence through activation of the NF-κB/chemokine/macrophage signaling axis

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, TGME49_205240) 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.