Characterization of a C-type lectin (OnCLEC10A) in Oreochromis niloticus functioning as a pattern recognition receptor with antibacterial properties.

C-type lectins (CTLs) constitute a superfamily of Ca2+-dependent carbohydrate-recognition proteins involved in pathogen recognition and elimination. In the present study, a C-type lectin family 10 member from Oreochromis niloticus (tentatively named OnCLEC10A) was identified and functionally characterized. OnCLEC10A contained a single Ca2+-dependent carbohydrate recognition domain with a conserved Gln-Pro-Asp (QPD) motif. Recombinant OnCLEC10A (rOnCLEC10A) protein exhibited strong bacterial binding and agglutination activities towards lipopolysaccharide (LPS) and peptidoglycan (PGN), as well as bacteria including Aeromonas hydrophila, Aeromonas veronii, Streptococcus agalactiae, and Staphylococcus aureus. The expression of OnCLEC10A was significantly upregulated in blood, brain, gill, head kidney, heart, intestine, liver and spleen following S. agalactiae challenge. Furthermore, blood cells transfected with pcDNA3.1+-OnCLEC10A exhibited enhanced phagocytic activity against S. agalactiae. OnCLEC10A prevention significantly improved the survival rate of O. niloticus and elevated the expression levels of inflammatory factors under bacterial challenge. Collectively, these findings suggest that OnCLEC10A plays an important role in host defense by mediating pathogen recognition and promoting antibacterial immune responses in O. niloticus.