Soluble C-type lectin LvLectin1 mediates recognition and agglutination of Ecytonucleospora hepatopenaei spores in Pacific white shrimp Litopenaeus vannamei

Ecytonucleospora hepatopenaei (formerly Enterocytozoon hepatopenaei or EHP) is an emerging microsporidian parasite that severely affects farmed shrimp by causing growth retardation and increasing susceptibility to secondary infections rather than causing high mortality. We characterized the function of Lv Lectin1, a soluble C-type lectin from L. vannamei , and investigated its role in host defense against EHP infection. Gene expression analysis revealed significant upregulation of LvLectin1 following EHP challenge. Functional assays demonstrated that recombinant Lv Lectin1 (r Lv Lectin1) agglutinates EHP spores, Candida albicans , and diverse bacterial strains. r Lv Lectin1 also inhibits EHP spore germination by promoting spore agglutination. Scanning electron microscopy and fluorescence imaging results confirmed r Lv Lectin1 binding to EHP spore surfaces. Enzyme-linked immunosorbent assay revealed high-affinity binding (Kd = 0.1681 µM), which was markedly reduced by competing monosaccharides, particularly N-acetylglucosamine (GlcNAc). These findings indicate that r Lv Lectin1 recognizes GlcNAc-containing glycans, likely chitin, on the spore surface. Consistently, GlcNAc inhibited r Lv Lectin1-mediated spore aggregation, supporting its specificity for chitin-rich structures. Furthermore, r Lv Lectin1 enhanced hemocyte encapsulation and melanization by activating the prophenoloxidase system. In contrast, RNA interference-mediated silencing of LvLectin1 increased EHP copy numbers, indicating its role in limiting pathogen proliferation. Collectively, these findings indicate that Lv Lectin1 functions as a pattern recognition protein in host defense against EHP infection.