Scabies, a parasitic skin infestation by the burrowing "itch" mite Sarcoptes scabiei, causes significant health problems for children and adults worldwide. Crusted
scabies is a particularly severe form of
scabies in which mites multiply into the millions, causing extensive skin crusting. The symptoms and signs of
scabies suggest host immunity to the
scabies mite, but the specific resistant response in humans remains largely uncharacterized. We used 4
scabies mite
recombinant proteins with sequence homology to extensively studied house dust mite
allergens to investigate a differential immune response between ordinary
scabies and the debilitating crusted form of the disease. Subjects with either disease form showed serum
IgE against recombinant S. scabiei
cysteine and
serine proteases and
apolipoprotein, whereas naive subjects showed minimal
IgE reactivity. Significantly (P < 0.05) greater serum
IgE and
IgG4 binding to mite
apolipoprotein occurred in subjects with crusted
scabies than in those with ordinary
scabies. Both subject groups showed strong proliferative responses (peripheral blood mononuclear cells) to the
scabies antigens, but the crusted
scabies group showed increased secretion of the Th2
cytokines interleukin 5 (IL-5) and
IL-13 and decreased Th1
cytokine gamma interferon (IFN-gamma) in response to the active
cysteine protease. These data confirm that a nonprotective allergic response occurs in the crusted disease form and demonstrate that clinical severity is associated with differences in the type and magnitude of the antibody and cellular responses to
scabies proteins. A quantitative
IgE inhibition assay identified
IgE immunoreactivity of
scabies mite
antigens distinct from that of
house dust mite antigens, which is potentially important for specific
scabies diagnosis and
therapy.