1. Queensland Institute of Medical Research and The Australian Center for International and Tropical Health and Nutrition, Brisbane, Australia
2. ^*Australian Genome Research Facility, University of Queensland, Brisbane, Australia
3. ^†Menzies School of Health Research, Darwin, Australia

Correspondence: David J. Kemp, Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, Herston, Qld, 4029, Australia. Email: daveK@qimr.edu.au

Received 8 April 2003; Revised 3 July 2003; Accepted 8 July 2003; Published online 8 December 2003.

Abstract

Parasitic infestation of the skin by the mite Sarcoptes scabiei is a significant problem worldwide, particularly in socially disadvantaged communities. A multigene family of at least 24 homologs of a serine protease allergen have been identified in S. scabiei. Surprisingly, the products of all but one of these genes are predicted to be catalytically inactive, due to mutations at a critical triad of amino acids at the active site. We discuss the possibility that these genes for inactivated proteases have been conserved because they mediate a novel host defense evasion strategy that the mite has evolved as an adaptation to parasitism of the epidermis. The identification of this family, and elucidation of its value to the parasite, may present an unanticipated approach to protective vaccination.