Scabies mite inactivated protease paralogues

Scabies is a disease of considerable importance in the developing world and among disadvantaged people such as the Aborigines in Australia, as it underlies streptococcal skin infections. It has been neglected at the molecular level until very recently. However, 43,776 expressed sequence tags have now been generated at the Australian Genome Research Facility from a cDNA library we constructed. Unexpectedly, in a search for homologues of house dust mite allergens among these sequences, we discovered large families of serine and cysteine protease genes with genetically inactivated catalytic sites. These are strong candidates for parasite defences against host immunity as we did not find them in a house dust mite cDNA library. Some possible modes of action are discussed.