Evaluation of Therapeutic Efficiency of Stylicin against Vibrio parahaemolyticus Infection in Shrimp Penaeus vannamei through Comparative Proteomic Approach

The shrimp immune system defends and protects against infection by its naturally expressing antimicrobial peptides. Stylicin is a proline-rich anionic antimicrobial peptide (AMP) that exhibits potent antimicrobial activity. In this study, stylicin gene was isolated from Penaeus vannamei, cloned into vector pET-28a ( +), and overexpressed in Escherichia coli SHuffle T7 cells. The protein was purified and tested for its antibiofilm activity against shrimp pathogen Vibrio parahaemolyticus. It was resulted that the recombinant stylicin significantly reduced the biofilm formation of V. parahaemolyticus at a minimum inhibitory concentration (MIC) of 200 µg. Cell aggregation was observed by using scanning electron microscopy and confocal laser scanning microscopy, and it was resulted that stylicin administration significantly affects the cell structure and biofilm density of V. parahaemolyticus. In addition, real-time PCR confirmed the downregulation (p < 0.05) of genes responsible for growth and colonization. The efficacy of stylicin was tested by injecting it into shrimp challenged with V. parahaemolyticus and 7 days after infection, stylicin-treated animals recovered and survived better in both treatments (T2-100 µg stylicin, - 68.8%; T1-50 µg stylicin, 60%) than in control (7%) (p < 0.01). Comparative proteomic and mass spectrometry analysis of shrimp hemolymph resulted that the expressed proteins were involved in cell cycle, signal transduction, immune pathways, and stress-related proteins representing infection and recovery, and were significantly different in the stylicin-treated groups. The result of this study suggests that the stylicin can naturally boost immunity and can be used as a choice for treating V. parahaemolyticus infections in shrimp.

Identification and expression analysis of a novel stylicin antimicrobial peptide from Kuruma shrimp (Marsupenaeus japonicus)

Antimicrobial peptides (AMPs) are important components of the innate immune system and function as the first line of defense against invading pathogens. In current study we identified, cloned and characterized a novel stylicin AMP from Kuruma shrimp Marsupenaeus japonicus (Mj-sty). The full-length cDNA of Mj-sty was 428 bp with an open reading frame of 315 bp that encoded 104 amino acids. The theoretical molecular mass of mature Mj-sty was 8.693 kDa with an isoelectric point (pI) of 4.79. A proline-rich N-terminal region and a C-terminal region contained 13 cysteine residues were identified. Genomic sequence analysis with respect to its cDNA showed that Mj-sty was organized into two exons interrupted by one intron. Tissue-specific expression revealed that Mj-sty was mainly transcribed in gills and hemocytes. Expression of Mj-sty in early developmental stages demonstrated that Mj-sty mRNA were present from fertilized eggs to post-larvae of 17 days (PL17), and the expression levels showed a significant variation in different developmental stages. After challenge of white spot syndrome virus (WSSV), the time-dependent expression pattern of Mj-sty in both gills and hepatopancrease showed down-regulation at the early hours of infection, subsequently up-regulation and down-regulation, and then up-regulation at the end hours to almost the half of the controls. The results indicate that Mj-sty is potentially involved in the ontogenesis and immune responses against WSSV.