Anti-Salmonella Activity Modulation of Mastoparan V1—A Wasp Venom Toxin—Using Protease Inhibitors, and Its Efficient Production via an Escherichia coli Secretion System

Abstract

A previous study highlighted that mastoparan V1 (MP-V1), a mastoparan from the venom of the social wasp <i>Vespula vulgaris</i>, is a potent antimicrobial peptide against <i>Salmonella</i> infection, which causes enteric diseases. However, there exist some limits for its practical application due to the loss of its activity in an increased bacterial density and the difficulty of its efficient production. In this study, we first modulated successfully the antimicrobial activity of synthetic MP-V1 against an increased <i>Salmonella</i> population using protease inhibitors, and developed an <i>Escherichia coli</i> secretion system efficiently producing active MP-V1. The protease inhibitors used, except pepstatin A, significantly increased the antimicrobial activity of the synthetic MP-V1 at minimum inhibitory concentrations (determined against 10⁶ cfu/mL of population) against an increased population (10⁸ cfu/mL) of three different <i>Salmonella</i> serotypes, Gallinarum, Typhimurium and Enteritidis. Meanwhile, the <i>E. coli</i> strain harboring <i>OmpA SS::MP-V1</i> was identified to successfully secrete active MP-V1 into cell-free supernatant, whose antimicrobial activity disappeared in the increased population (10⁸ cfu/mL) of <i>Salmonella</i> Typhimurium recovered by adding a protease inhibitor cocktail. Therefore, it has been concluded that our challenge using the <i>E. coli</i> secretion system with the protease inhibitors is an attractive strategy for practical application of peptide toxins, such as MP-V1.