Proteomic profiling of hydatid cyst fluid obtained in mouse strains exhibiting different susceptibility to secondary cystic echinococcosis.

Cystic echinococcosis (CE), caused by Echinococcus granulosus sensu lato (s.l.), is a neglected tropical disease affecting over one million people worldwide. The proteomic composition of hydatid cyst fluid (HCF) varies depending on the host species and cyst location, influencing its diagnostic potential; however, the impact of intra-species host genetic variation on HCF remains poorly understood. To address this, we conducted comparative proteomic analyses of HCF from experimental secondary CE in mouse strains differing in infection susceptibility: BALB/c, C57BL/6, and CD1. Nine HCF pools (three per strain) were analyzed using high-resolution nanoLC-MS/MS coupled to Orbitrap mass spectrometry. Across all samples, 466 distinct proteins were identified, including 204 and 262 of parasite and host origin, respectively. The HCF from CD1 mice exhibited a markedly distinct proteomic profile compared with BALB/c and C57BL/6, containing 401 core proteins versus 330 and 292, respectively. A shared set of 256 proteins was consistently detected across all strains, among which 58 showed significant differences in abundance; predominantly between CD1 and the inbred strains. Several host serpin family proteins varied notably in abundance among strains. These findings suggest that host genetic background may influence the composition and relative abundance of HCF proteins, particularly those related to immune function. The identification of invariant proteins across genetically diverse hosts supports their potential as reliable immunodiagnostic markers, while variable expression of parasite serpins is consistent with possible roles in host adaptation and disease progression, though further validation is warranted.