Systematic proteomic and small RNA profiling of extracellular vesicles from cattle infected with a naturally occurring buparvaquone-resistant strain of Theileria annulata and from uninfected controls.

Background: Extracellular vesicles (EVs) play a pivotal role in host-parasite interactions, particularly in facilitating parasite pathogenesis and immune modulation, and are crucial mediators of intercellular communication. Theileria annulata, an apicomplexan parasite, induces severe alterations in host cells, promoting uncontrolled proliferation, resistance to apoptosis, and immune evasion. Although EVs contribute to these processes, the proteins and small RNA cargo involved in T. annulata infection remain incompletely characterized. In particular, little is known about EV profiles in infections caused by drug-resistant field strains.

Methods: In this study, we conducted systematic proteomic and small RNA profiling of EVs derived from naturally occurring buparvaquone-resistant T. annulata (Xinjiang Kashi strain) infected and uninfected bovine sera to investigate infection-induced alterations. Additionally, EVs were isolated from T. annulata-infected bovine immune cells to determine the protein and microRNA (miRNA) compositions of EVs secreted by specific immune cell types. Label-free liquid chromatography-tandem mass spectrometry proteomics and small RNA sequencing were employed to identify EV-associated proteins and miRNAs, followed by functional enrichment analysis to explore key host-parasite regulatory pathways.

Results: Our analysis identified 2580 proteins and 6635 miRNAs in EVs derived from T. annulata-infected bovine serum and immune cell types, many of which are implicated in parasite development, host invasion, and immune modulation. Significant alterations were observed in the EV cargo from infected sera, including enrichment of vesicular proteins and miRNAs associated with immune regulation, metabolic reprogramming, and host-pathogen interactions. Furthermore, functional enrichment analyses highlighted key pathways such as ECM-receptor interactions, oxidative phosphorylation, and proton transport, underscoring the role of EVs in host immune modulation. Supplementary analysis of EVs from infected immune cells provided further insights into the cell type-specific contributions.

Conclusions: This study comprehensively characterized the infection-induced changes in serum-derived EVs associated with a naturally occurring buparvaquone-resistant T. annulata infection. It offers novel insights into how T. annulata exploits EVs to manipulate host responses. The identification of unique EV-associated proteins and miRNAs highlights their potential as biomarkers and therapeutic targets for Theileria infections. These findings contribute to a deeper understanding of host-parasite interactions and lay the foundation for future investigations into EV-mediated pathogenesis and immune evasion.