Penaeus vannamei serine proteinase inhibitor 7 (LvSerpin7) acts as an immune brake by regulating the proPO system in AHPND-affected shrimp

• Published in: Developmental and comparative immunology 2020-05, Vol.106, p.103600, Article 103600
• Main Authors: Apitanyasai, Kantamas, Chang, Che-Chih, Ng, Tze Hann, Ng, Yen Siong, Liou, Jiun-Hung, Lo, Chu-Fang, Lin, Shih-Shun, Wang, Han-Ching
• Format: Article
• Language: English
• Subjects: AHPND; Bacteria; Decapoda; Gene expression; Hemocytes; Hemolymph; Immunity; Infections; Litopenaeus vannamei; Necrosis; Phenoloxidase; Prophenoloxidase; Proteinase; Proteinase inhibitors; Serine; Serine proteinase; Serine proteinase inhibitors; Serpin; Shrimp; Stomach; Toxicity; Transcription; Waterborne diseases
• ISSN: 0145-305X; 1879-0089
• DOI: 10.1016/j.dci.2019.103600

Acute hepatopancreatic necrosis disease (AHPND) is a recently emerged disease in aqua cultured shrimp that is caused by virulent strains of Vibrio parahaemolyticus (VP). Our previous study used transcriptomics to identify key pathogenic factors in the stomach of AHPND-infected shrimp (Litopenaeus vannamei), and here we used a different subset of the same data to construct a gene-to-gene expression correlation network to identify immune-responsive genes. LvSerpin7 was found to have the highest number of correlations after infection, and it also showed a significant increase in mRNA expression. LvSerpin7 is expressed in all tissues but its expression levels are highest in hemocytes. After successfully silencing LvSerpin7 transcript prior to AHPND challenge, mortality was significantly increased relative to the controls and reached 100% within 36 h post infection. Compared to the controls, the phenoloxidase (PO) activity also increased in both hemolymph and stomach. Recombinant LvSerpin7 inhibited shrimp PO activity in vitro, and we also found that rLvSerpin7 inhibited the growth of AHPND-causing bacteria. These results suggest that LvSerpin7 might reduce the toxic effects that result from unregulated activation of the PO defense system by AHPND-causing bacteria. •Serine proteinase inhibitor 7 (Serpin7) may play a key factor in shrimp failed to be affected by AHPND.•Lvserpin7 was significantly increased after shrimp were challenged with Vibrio parahaemolyticus AHPND-causing strain 5HP.•Lvserpin7 silencing in shrimp led to the increase in AHPND-causing mortality and the phenoloxidase (PO) activity.•Recombinant LvSerpin7 inhibited shrimp PO activity in vitro.•LvSerpin7 might reduce the toxic effects from the overactive PO defense system by AHPND-causing bacteria.