Glycan specificities under in vitro and in silico environments and expression of a C-type lectin-HiL from the larvae of black soldier fly, Hermetia illucens

Lectins, known as haemagglutinins, are multivalent proteins of non-immune origin, that have sugar-binding specificity and play an important role in the immune defense functions of the invertebrates. In the present study, a calcium-dependent sialic acid-specific haemagglutinin was detected and characterized from the haemolymph of the larvae of black soldier fly, Hermetia illucens . The haemagglutinin showed the highest titre value of 64 against mouse and rabbit erythrocytes following rat with a titre value of 16. The haemagglutinin was heat-labile, cation-dependent especially calcium, and sensitive to EDTA. Among the carbohydrates tested, N-acetyl-neuraminic acid (NANA) strongly inhibited the haemagglutinating activity of serum against mouse and rabbit erythrocytes with a MIC of 12.5 mM. Among the three glycoproteins tested, only thyroglobulin inhibited the activity against mouse and rabbit erythrocytes with a MIC of 3.90 µg/ml. The relative expression of lectin gene using RT-qPCR based on the primers designed to a specific amplified gene fragment of 709 bp revealed almost its equal expression in fat body, gut and haemocytes. In silico analysis on the sequence of lectin gene showed beta-galactoside binding domains. Molecular docking and molecular dynamic simulation studies uncovered a strong affinity of H. illucens haemolymph lectin to NANA among various glycans tested.