Shrimp lectin–conjugated copper sulfide nanoparticles enhance immune response and gene expression in Etroplus suratensis infected with Aeromonas hydrophila

Lectins are hemagglutinating glycoproteins which act as pathogen recognition receptors that can bind to the pathogen-associated molecular patterns. Shrimp lectin (Md-Lec) is a lectin that is reported to have antimicrobial property. In this study, the CuS nanoparticles (CuS NPs) which were previously reported to have wide range of antimicrobial activity were conjugated with Md-Lec. Thus, their minimum inhibitory concentration (MIC) against aquatic pathogens was reduced four times than that of their individual activity. Moreover, antibacterial and antibiofilm assay was performed with Md-Lec, pCuS NPs, and Md-Lec conjugated with pCuS NPs (Md-Lec-pCuS NPs) against Aeromonas hydrophila at 25, 50, and 100 μg/mL. The hydrophobicity index and EPS (extracellular polysaccharide) production of A. hydrophila were decreased after treating with Md-Lec-pCuS NPs. The non-specific immune parameters—lysozyme assay, peroxidase assay, and respiratory burst activity—were elevated considerably in the infected fishes that are treated with Md-Lec-pCuS NPs at their MIC. Further, immune gene (COX2, MyD88, and LEC) expression analysis at different time intervals was also done in the infected Etroplus suratensis that are treated with Md-Lec-pCuS NPs at 3.13 μM concentration. The results reveal that the immune gene expression was upregulated at the 6th hour of infection in the infected fish that are treated with Md-Lec-pCuS NPs (3.13 μM) and thus it can be used as a therapeutic agent which can act as an immunostimulant for the production of disease-free fishes in aquaculture industry. [Figure not available: see fulltext.]