The Function and Modification of Human Defensin 5.

The antibacterial and antiviral functions of human defensin 5 lay the foundation for its role as a core host protective component. In addition, HD5 also has the function of inhibiting tumor proliferation and immune regulation. However, everything has two sides; cytotoxic and proinflammatory properties may exist, while HD5 performs physiological functions. Accordingly, the modification and engineering of HD5 are particularly important. Therefore, this review summarizes the role of HD5 in various aspects of host defense, as well as modification of HD5 to ameliorate the biological activity, with a view to promoting the clinical use of HD5.

Identification and characterization of two arasin-like peptides in red swamp crayfish Procambarus clarkii.

Antimicrobial peptides (AMPs) are small effectors in host defense by directly targeting microorganisms or by indirectly modulating immune responses. In the present study, two arasin like AMPs, named as Pc-arasin1 and Pc-arasin2, were identified in red swamp crayfish Procambarus clarkii with sequence similarity to the arasins found in Hyas araneus. Both Pc-arasins consisted of signal peptide, N-terminal proline-rich region and C-terminal region containing four conserved cysteine residues. The similarity of two Pc-arasins was 44.44%, and Pc-arasin2 contained several additional residues in the N-terminus. Multiple alignment of arasin family suggested the conservation of the C-terminus and the variation of the N-terminus of Pc-arasins. Both AMPs were found hemocytes-specific, and the expression could be induced the challenge of bacteria, espeacially by the pathogenic bacterium Aeromonas hydrophila. Knockdown of each Pc-arasin expression by double strand RNA would suppress the host immunity against A. hydrophila, and the commercially synthetic Pc-arasins could rescue the knockdown consequence. Both synthetic peptide showed broad antimicrobial activity towards 3 Gram-positive bacterium and 3 Gram-negative bacterium, and the minimal inhibitory concentrations varied from 6.25 µM to 50 µM. These results presented new data about the sequence, expression and function of arasin family, and emphasized the role of this family in host immune response against bacterial pathogens. The characterization of Pc-arasins also provided potential of therapeutic agent development for disease control in aquaculture based on these two newly identified AMPs.

Molecular cloning and characterization of a C-type lectin from the cotton bollworm, Helicoverpa armigera.

C-type lectins participate in pathogen recognition and other defense responses in innate immunity as well as in cell-cell interactions. A new cDNA encoding a 335-residue polypeptide containing two tandem C-type lectin domains was cloned from the haemocytes of Helicoverpa armigera (Ha-lectin). Northern hybridizations revealed that the mRNA of Ha-lectin was expressed constitutively in haemocytes, and was up-regulated following injections of bacteria, yeast, or virus. Ha-lectin expression was also induced in the fat body when larvae were injected with bacteria, yeast or 20-hydroxyecdysone and a non-steroidal ecdysone agonist, RH-2485. The Ha-lectin was detected in granular haemocytes. The recombinant protein (rHa-lectin) expressed in Escherichia coli had hemagglutinating and sugar-binding activities. The native Ha-lectin protein was identified in haemocytes and plasma using a polyclonal antiserum raised against rHa-lectin by immunoblotting techniques. All together, our results suggest that the Ha-lectin gene is involved in innate immunity, and may also participate in the molting process.