Blood plasma proteomics for detecting potential biomarkers for tick resistance in a tropically adapted beef cattle...

Tick infestation is one of the main challenges in tropical beef cattle production, leading to significant economic losses. Knowledge of the molecular factors underlying natural tick resistance in cattle contributes to genetic selection through the identification of biomarkers that can be used to accurately identify animals resistant to ticks. Although several genes associated with resistance to ticks have been identified, the molecular mechanisms underlying tick resistance are yet to be elucidated. This study investigated the biological processes, pathways, and key proteins involved in the resistance to the tick Rhipicephalus (Boophilus) microplus in a tropically adapted beef cattle breed. Tick resistance was evaluated in 162 Caracu cows. Blood samples were collected from a subset of 16 extreme animals, including eight with a high tick load (SUS) and eight with a low tick load (RES), for proteomic analysis by LC-MS/MS.

A total of 172 and 34 proteins were exclusively identified in plasma samples from the SUS and RES groups, respectively. In addition, 14,034 proteins were detected in the blood plasma of both groups, of which 51 and 101 proteins were significantly increased in plasma samples of the SUS and RES groups, respectively. Among the top 20 proteins with the highest absolute log-fold change values, those encoded by the RNASE1, TNS2, NOXO1, ZNRF3, APOA4, KMT2B, RPS6KA5, PON1, C4BPA, SETD2, HP, TMEM63A, MAST2, and SETD1B genes were highlighted based on their functions that may contribute to a response to tick infestation. Functional enrichment analysis revealed 36 biological processes, 35 molecular functions, and 16 pathways to be significant (P < 0.05), highlighting those related to hemostasis, vesicular transport, cell proliferation and migration, calcium, actin, lipids, scavenger receptors, hydrogen peroxide, tyrosine, and insulin-like growth factor, which may contribute to tick resistance. In addition, PPI network analysis revealed several proteins involved in complement and coagulation systems, hematopoiesis, and immune response as important nodes, based on their centrality and edges.

The identification of differentially abundant proteins between RES and SUS animals, as well as their relationships and roles in key biological processes and molecular pathways detected, contribute to improving our understanding of the mechanisms underlying tick resistance in naturally adapted cattle breeds. Furthermore, the differentially abundant proteins detected in this study are potential biomarkers for the response to R. microplus infestation.