Novel stomach-predominant C-type lectin (LvnCTL) triggers immune response against Vibrio parahaemolyticus and WSSV in shrimp Litopenaeus vannamei.

C-type lectins (CTLs) are members of pattern recognition receptors (PRRs), which can bind to carbohydrates on the surface of pathogens and take part in the immune response of shrimp. In this study, we identified and characterized a novel stomach-predominant C-type lectin (named LvnCTL) in Litopenaeus vannamei (L. vannamei). LvnCTL consists of a signal peptide at the N-terminal and a typical C-type lectin-like domain (CTLD) at the C-terminal. Phylogenetic analysis revealed that LvnCTL clusters into a distinct clade more closely related to vertebrate CTLs than to invertebrate CTLs. LvnCTL was highly expressed in the stomach, and its expression was significantly induced by immune stimuli and pathogen infections. Functional assays showed that silencing of LvnCTL enhanced the replication of Vibrio parahaemolyticus and white spot syndrome virus (WSSV), thereby increasing shrimp susceptibility. In contrast, recombinant LvnCTL effectively agglutinated both the Gram-negative bacterium V. parahaemolyticus and the Gram-positive bacterium Staphylococcus aureus in a Ca2+-dependent manner. Furthermore, LvnCTL silencing markedly altered the expression of immune-related genes, including antimicrobial peptides, cytokines, and prophenoloxidase (proPO) genes. Taken together, these findings suggest that LvnCTL plays a crucial role in the shrimp immune response to inhibit pathogen invasion.