A lymphoid organ-enriched C-type lectin, functions as a pattern recognition receptor and inflammatory regulator in Litopenaeus vannamei

Crustacean C-type lectins (CTLs) constitute a versatile receptor family that play key roles in innate immune recognition. Here, a C-type lectin LvccCTL, primarily expressed in the lymphoid organs, was identified and characterized from the Pacific white shrimp Litopenaeus vannamei . LvccCTL contained a coiled-coil region and a carbohydrate-recognition domain (CRD) with a non-canonical QPV motif. LvccCTL transcripts in the lymphoid organs were significantly upregulated following pathogen challenge, particularly with Vibrio parahaemolyticus infection. The recombinant LvccCTL (rLvccCTL) bound to various PAMPs as well as to the tested bacteria and yeast. It agglutinated the tested bacteria but not yeast in a Ca 2+ -dependent manner, and such agglutinating activity could be significantly inhibited by D -galactose, LPS PGN and GLU. Knockdown of LvccCTL significantly downregulated the expression of LvALF4, key genes of NF-κB and JAK-STAT pathways, as well as inflammation- and redox-related genes, whereas it had no obvious effect on phagocytosis genes. Furthermore, LvccCTL knockdown led to elevated reactive oxygen species (ROS) levels and altered inducible nitric oxide synthase (iNOS) activities in the lymphoid organs after LPS stimulation. Collectively, these findings suggest that LvccCTL could function as a PRR in immune recognition and a regulator of inflammatory responses in shrimp lymphoid organ.