Abstract
Crustin are a family of antimicrobial peptides that play an important role in protecting against pathogens infection in the innate immune system of crustaceans. Previously, we identified several novel types of crustins, including type VI and type VII crustins. However, their immune functions were still unclear. In the present study, the immune function of type VII crustin LvCrustinVII were investigated in Litopenaeus vannamei. LvCrustinVII was wildly expressed in all tested tissues, with relatively high expression levels in hepatopancreas, epidermis and lymphoid organ. Upon Vibrio parahaemolyticus infection, LvCrustinVII was significantly upregulated in hepatopancreas. Recombinant LvCrustinVII (rLvCrustinVII) showed strong inhibitory activities against Gram-negative bacteria Vibrio harveyi and V. parahaemolyticus, while weak activities against the Gram-positive bacteria Staphylococcus aureus. Binding assay showed that rLvCrustinVII could bind strongly to V. harveyi and V. parahaemolyticus, as well as the cell wall components Glu, LPS and PGN. In the presence of Ca2+, rLvCrustinVII could agglutinate V. parahaemolyticus and enhance hemocyte phagocytosis. The present data partially illustrate the immune function of LvCrustinVII, which enrich our understanding on the functional mechanisms of crustins and provide useful information for application of this kind of antimicrobial peptides.
Highlights
In recent years, aquaculture develops rapidly in China, but it faces serious problems with disease outbreaks
V. parahaemolyticus and greatly enhance phagocytosis of shrimp hemocytes in the presence of Ca2+. These results suggest that LvCrustinVII might exert dual functions as Antimicrobial peptides (AMPs) and opsonin in host immune system to fight against pathogens infection
In order to know whether it participates in host immune defense, the immune responses of LvCrustinVII were detected in shrimp after Vibrio parahaemolyticus infection
Summary
Aquaculture develops rapidly in China, but it faces serious problems with disease outbreaks. Many antibiotics are used to deal with this problem [1]. Due to the failure of most conventional antibiotics to counteract “superbugs” and the dwindling supply of new ones, there is an urgent need to develop other antibacterial drugs [3,4]. AMPs have the advantages of less resistance, least toxicity to the host, broad spectrum activity and rapid killing ability [6,7]. These properties make them the best alternative to fight against bacteria [8]. Many research groups have focused on AMPs and greatly improved our understanding of how AMPs exert their antibacterial effects [9,10]
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