Calprotectin Expression in Adventitial Layer of Cattle and Sheep Echinococcus granulosus sensu stricto Cysts

Cystic echinococcosis (CE) is a globally distributed zoonotic disease caused by <i>Echinococcus granulosus</i> sensu lato, forming fluid-filled cysts in humans and livestock. These cysts consist of three layers: an inner germinal layer and a middle laminar layer of parasitic origin, and an outer adventitial layer derived from the host's immune response. The adventitial layer typically contains immune cells such as T and B lymphocytes, macrophages, and other inflammatory cells. Notably, differences have been reported in the cellular composition of this layer depending on the host species. However, the variation in calprotectin expression-a protein specific to phagocytes-between cattle and sheep CE cysts has not been previously described. This study assessed calprotectin expression using immunohistochemistry with anti-calprotectin antibodies on adventitial tissue sections from cattle and sheep CE cysts. The results showed a significantly higher calprotectin expression in the adventitial layer of cattle cysts compared to sheep. This difference was not associated with the fertility or anatomical location of the cysts. These findings suggest that the host species influences the level of calprotectin expression in the adventitial layer, contributing to our understanding of host-specific immune responses in CE.