Abstract
BackgroundScabies is a disease of worldwide significance, causing considerable morbidity in both humans and other animals. The scabies mite Sarcoptes scabiei burrows into the skin of its host, obtaining nutrition from host skin and blood. Aspartic proteases mediate a range of diverse and essential physiological functions such as tissue invasion and migration, digestion, moulting and reproduction in a number of parasitic organisms. We investigated whether aspartic proteases may play role in scabies mite digestive processes.Methodology/Principle FindingsWe demonstrated the presence of aspartic protease activity in whole scabies mite extract. We then identified a scabies mite aspartic protease gene sequence and produced recombinant active enzyme. The recombinant scabies mite aspartic protease was capable of digesting human haemoglobin, serum albumin, fibrinogen and fibronectin, but not collagen III or laminin. This is consistent with the location of the scabies mites in the upper epidermis of human skin.Conclusions/SignificanceThe development of novel therapeutics for scabies is of increasing importance given the evidence of emerging resistance to current treatments. We have shown that a scabies mite aspartic protease plays a role in the digestion of host skin and serum molecules, raising the possibility that interference with the function of the enzyme may impact on mite survival.
Highlights
Scabies is a disease of worldwide significance, caused by infestation of the skin with the ‘‘itch mite’’ Sarcoptes scabiei
No trypsin or chymotrypsin like serine protease activity was detected in the scabies mite extract, an active serine protease sequence had previously been identified among scabies mite expressed sequence tags [9]
Aspartic proteases play a key role in invasion and digestion processes in many parasitic organisms
Summary
Scabies is a disease of worldwide significance, caused by infestation of the skin with the ‘‘itch mite’’ Sarcoptes scabiei. Evidence of emerging scabies mite resistance to ivermectin [3,4,5] and permethrin [6,7] emphasises the need to develop new anti-parasite therapies. This requires further understanding of scabies mite biology and host interaction. The presence of cysteine protease activity in scabies mite extract has not been investigated multiple active as well as putatively inactive cysteine proteases have been identified among scabies mite expressed sequence tags [11] and functional analysis of these molecules is underway [12]. We investigated whether aspartic proteases may play role in scabies mite digestive processes
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