Identification and characterisation of different proteases in Lucilia sericata medicinal maggots involved in maggot debridement therapy

Maggot debridement therapy (MDT) is increasingly being used as a fast and effective treatment approach for healing chronic wounds. The removal of necrotic tissue from wounds is a fundamental step in successful treatment. Larvae of Lucilia sericata produce a cocktail of proteolytic and antimicrobial substances in the gut as well as salivary glands called excretion/secretion (ES) products. Three groups of proteolytic enzymes (serine, aspartyl and metalloproteinases) were identified in the larval ES products to date. We prepared cDNA library from the salivary glands and identified novel putative serine proteases, metalloproteinase and signal peptide protease. In situ hybridisation revealed following expression profiles in all the three larval instars during the feeding stage: serine protease 1 – frontgut and fat body including grease coupler of salivary glands; serine protease 2 – salivary glands and Malpighian tubes; serine protease 3 – salivary glands and anterior midgut; prenyl metalloproteinase and signal peptide protease – salivary glands and fat body. We also investigated the expression of chymotrypsin, previously identified protease, and found that it is produced only in the anterior part of the midgut. In conclusion, we identified five novel putative proteases of medicinal maggots and demonstrated that they could be secreted into the wound during the MDT.