Mouse Beta-Defensin 3 (mBD3) peptide,a homolog of human beta-defensin 2 (hBD2),is a cysteine-rich cationic antimicrobial peptide of 41 amino acids which belongs to the defensins family. Defensin peptides are cationic peptides originally produced in various organs. They are involved in the protection against different kinds of pathogens like bacteria,fungi,and several viruses and play an important role in inflammation and wound repair. mBD3peptide showed antimicrobial activity against Gram-negative bacteria S.Aureus and S.pyogenes and against Gram-positive bacteria like certain strains of P.Aeruginosa (MIC of 8 µg/mL) and E.coli (MIC of 16 µg/mL). An antimicrobial activity has also been demonstrated against C.Albicans. The in vivo and in vitro efficiency of mBD3 peptide against viruses like influenza was also shown. mBD3 peptide can be interesting for therapeutic applications.
Technical specification
Sequence : KKINNPVSCLRKGGRCWNRCIGNTRQIGSCGVPFLKCCKR K
Background :Influenza causes significant morbidity and mortality. Mammalian β-defensins are small peptides of about 4.5-6 kDa in mass and are effectors of the innate immune response with potent antimicrobial activity. In this paper,we focused on the anti-influenza A activity of the recombinant mouse β-defensin 3 (rMBD-3) in vivo and in vitro.
Methods :The rMBD-3 peptide was added to Madin-Darby canine kidney (MDCK) cells at different stages of influenza A virus (IAV) A/PR/8/34 (H1N1) infection and its virus inhibitory properties were determined. Mice were infected with IAV and treated with rMBD-3 peptide from 12 h post-infection. The effect of rMBD-3 peptide was determined by pulmonary viral load,pathology and mortality. In addition,the expression of interleukin (IL)-12,interferon (IFN)-γ and tumour necrosis factor (TNF)-α genes in mice with or without rMBD-3 treatment was determined by semi-quantitative reverse transcriptase PCR.
Results :rMBD-3 was shown to protect MDCK cells against IAV infection and had a major role in inhibition of adsorption and uptake by cells infected with IAV. Following the addition of 100 μg/ml rMBD-3 to MDCK cells medium,approximately 80% of cells were protected from infection in vitro. rMBD-3 given by tail vein injection (10 mg/kg/day) was the most effective method to improve the survival rate of the mice. Treatment with rMBD-3 was found to up-regulate IFN-γ and IL-12 gene expression,but reduced expression of the TNF-α gene.
Conclusions :These results demonstrate that rMBD-3 possesses anti-influenza virus activity both in vivo and in vitro that might be of therapeutic use.
BACKGROUND: One component of host defense at mucosal surfaces is epithelium-derived peptides with antimicrobial activity called defensins.
OBJECTIVE: We describe in this report the isolation and characterization of a murine homologue of human beta-defensin 2 (hBD-2) called mouse beta-defensin 3 (mBD-3).
METHOD/RESULTS: The predicted amino acid sequence shows the hallmark features of other known epithelial defensins,including the ordered array of six cysteine residues. Analysis of a genomic clone of mBD-3 revealed two exons separated by a 1.7-kb intron. The mBD-3 gene is localized at the proximal portion of chromosome 8,the site where genes for mouse alpha- and beta-defensins are found. Under basal condition,mBD-3 transcripts were detected at low levels in epithelial cells of surface organs,such as the intestine and lung. After instillation of Pseudomonas aeruginosa PAO1 into mouse airways,mBD-3-specific mRNA was upregulated significantly not only in large airways but also in the small bowel and liver. Recombinant mBD-3 peptide,produced from a baculovirus expression system,showed antimicrobial activity against P. aeruginosa PAO1 (MIC of 8 micrograms/ml) and Escherichia coli D31 (MIC of 16 micrograms/ml) in a salt-dependent manner.
CONCLUSION: This study demonstrates that a murine homologue of hBD-2 is present in the respiratory system and other mucosal surfaces. These similarities between murine and human host defense apparatus provide further impetus to evaluate the mouse as a model for studying the human innate host defense system.
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