Collectin-K1 Plays a Role in the Clearance of in Nile Tilapia ().

Collectin-K1 (CL-K1) is a multifunctional C-type lectin that has been identified as playing a crucial role in innate immunity. It can bind to carbohydrates on pathogens, leading to direct neutralization, agglutination, and/or opsonization, thereby inhibiting pathogenic infection. In this study, we investigated a homolog of CL-K1 (CL-K1) in Nile tilapia () and its role in promoting the clearance of the pathogen () and enhancing the antibacterial ability of the fish. Our analysis of bacterial load displayed that substantially reduced the amount of in tissues of the liver, spleen, anterior kidney, and brain in Nile tilapia. Furthermore, examination of tissue sections revealed that CL-K1 effectively alleviated tissue damage and inflammatory response in the liver, anterior kidney, spleen, and brain tissue of tilapia following infection. Additionally, 1 was found to decrease the expression of the pro-inflammatory factor and migration inhibitor , while increasing the expression of anti-inflammatory factor and chemokine in the spleen, anterior kidney, and brain tissues of tilapia. Moreover, statistical analysis of survival rates demonstrated that CL-K1 significantly improved the survival rate of tilapia after infection, with a survival rate of 90%. Collectively, our findings suggest that CL-K1 plays a vital role in the innate immune defense of resisting bacterial infection in Nile tilapia. It promotes the removal of bacterial pathogens from the host, inhibits pathogen proliferation in vivo, reduces damage to host tissues caused by pathogens, and improves the survival rate of the host.