Immune responses and immunoprotection in crustaceans with special reference to shrimp.

Abstract

Crustacean aquaculture, dominated by shrimp, is a highly profitable food-produc-ing sector in the world. However, a variety of biotic and abiotic stressors can haveadverse effect on the immune system of shrimp making them susceptible to diseases.Although a vertebrate-like adaptive immune system is lacking in shrimp, an effi-cient innate immune system renders protection against invading pathogens. Theinnate immune system comprises two distinct but overlapping components, thecellular and humoral, and these are regulated through several signal transductionpathways. The signal pathways are initiated by the recognition of pathogen-associ-ated molecular patterns by germline-encoded pattern recognition receptors leadingto the production of different effector molecules that act against the pathogens.RNAi-mediated post-transcriptional gene silencing and microRNA regulation ofimmune response have also been found to be functional in shrimp. Similarly, apop-tosis and apoptosis-related genes are also reported, besides interferon (IFN) sys-tem-like antiviral regulatory mechanism. Further, some form of immune memory,termed ‘immune priming’ or ‘innate immunity with specificity’ and ‘quasi-immuneresponse’ is recorded in shrimp and these abilities have been exploited in verifyingthe immunoprotection against different pathogens. Antigens developed eitherdirectly from the pathogens or through recombinant proteins have been tested forimmune-protective ability. RNAi-mediated protection has also been demonstratedagainst different shrimp viruses. This review summarizes the available scientificinformation on immune responses and the immunoprotection trials carried out incrustaceans with a focus on shrimp. The available research evidences indicate thepotential of developing effective immunoprophylactic measures in shrimp.