PSIV-18 Proteomics analysis reveals potential biomarkers for tick resistance in Caracu beef cattle.

Abstract Rhipicephalus (Boophilus) microplus tick causes large economic losses in beef cattle production, mainly in regions under tropical climates. The evaluation of tick resistance in breeding programs requires individual phenotype collection based on tick counts, which is an extremely laborious process. The knowledge of the genomic architecture of resistance to ticks can contribute to identify biomarkers, which could be used to identify animals resistant to tick. This study aimed to investigated key pathways and potential biomarkers involved in resistance against tick in Caracu. A total of 162 cows have their resistance to tick evaluated through direct counts of tick telogens during 18 months. A subset of 16 extreme animals, including the eight with high tick load (susceptible group) and eight with low tick load (resistant group), had their blood plasma samples used for proteomic analysis by liquid chromatography coupled to tandem mass spectrometry in a data-dependent acquisition mode. Proteins with fold-change ratios ≥ 2 and ≤ 0.5 were considered as differentially abundant (P < 0.05). The differentially abundant proteins were used to perform functional enrichment analysis by DAVID tool (P < 0.05). The protein-protein interaction (PPI) network of proteins differentially regulated was evaluated by STRING tool, with a medium confidence score (0.4). A total of 152 differentially abundant proteins were detected between the two experimental groups. Among the top proteins with the highest absolute log-fold change values, those encoded by the APOA4, C4BPA, HP, KMT2B, MAST2, NOXO1, PON1, RNASE1, RPS6KA5, SETD1B, SETD2, TMEM63A, TNS2, and ZNRF3 genes were highlighted based on their functions. The functional enrichment analysis revealed several Gene Ontology terms and pathways that may be associated with tick resistance, such as those linked to hemostasis, cell proliferation and migration, calcium, actin, and lipids. PPI network analysis also revealed several proteins acting in complement and coagulation systems, hematopoiesis, and immune response as important nodes based on their centrality and edges. The identification of differentially abundant proteins and its relationship, as well as of their roles in key pathways contribute to improve the knowledge of the mechanisms behind the tick resistance in naturally adapted cattle breeds. In addition, differently abundant proteins detected in this study are potential biomarkers for response to tick resistance.