Therapeutic effect and immune mechanism of chitosan-gentamicin conjugate on Pacific white shrimp (Litopenaeus vannamei) infected with Vibrio parahaemolyticus

To explore the disease resistance mechanism of chitosan conjugates, chitosan-gentamicin conjugate (CS-GT) was synthesized and systematically characterized, the immune mechanism of CS-GT on Litopenaeus vannamei infected with Vibrio parahaemolyticus was further explored. The results showed that imine groups in CS-GT were effectively reduced. Dietary supplementation of CS-GT can significantly increase the survival rate, total hemocyte counts, the antioxidant and immune related enzyme activity levels of shrimps (P < 0.05), which are all dose-dependent under the experimental conditions. In addition, CS-GT can protect the hepatopancreas from invading bacteria and alleviate inflammation. Particularly, CS-GT promotes the expressions of legumain (LGMN), lysosomal acid lipase (LIPA) and Niemann-Pick type C2 (NPC2) up-regulated. It is speculated that CS-GT may stimulate the lysosome to phagocytose pathogens more effectively. In conclusions, shrimps fed with CS-GT can produce immune response via lysosome and greatly improve the disease resistance to Vibrio parahaemolyticus.