Echinococcus granulosus antigen 5: a novel immunomodulator that targets NF-κB signaling to suppress inflammation in THP-1 monocyte.

Chronic infection by Echinococcus granulosus leads to the establishment of fluid-filled cysts (hydatid cysts) in the liver or lungs of infected hosts, which can escape destruction by the host immune system for long periods. Ag5 is abundantly expressed in the cyst fluid of the fine-grained E. granulosus and plays an important role in immune tolerance in cystic echinococcosis. However, the role that Ag5 plays in monocytes is not fully known. Here, the expression characteristics and function of Ag5 were explored in human monocytic THP-1 cells by various assays. The findings of the present study revealed that Ag5 inhibited the polarization of THP-1 cells into macrophages and reduced the expression profiles of intracellular pro-inflammatory factors such as TNF-α, IL-1β, and IL-6 through the NF-κB pathway. These findings suggest that Ag5 plays a crucial role in E. granulosus's ability to suppress host immune responses and support the long-term survival of the parasite.