Characterization of Sarcoptes scabiei Tropomyosin and Paramyosin: Immunoreactive Allergens in Scabies

Scabiesis a human skin disease due to the burrowing ectoparasite Sarcoptes scabiei var. hominisresulting in intense itching and inflammation and manifesting as a skin allergy. Because of insufficient mite material and lack of in vitro propagation system for antigen preparation, scabiesis a challenging disease to develop serological diagnostics. For allergen characterization, full-length S. scabiei tropomyosin(Sar s 10) was cloned, expressed in pET-15b, and assessed for reactivity with IgEantibodies from human sera. IgEbinding was observed to Sar s 10 with sera collected from subjects with ordinary scabies, house dust mite(HDM)-positive and naive subjects and a diagnostic sensitivity of < 30% was observed. S. scabiei paramyosin (Sar s 11) was cloned, and expressed in pET-28a in three overlapping fragments designated Sspara1, Sspara2, and Sspara3. IgEand IgG binding was observed to Sspara2 and Sspara3 antigens with sera collected from ordinary scabies, and HDM-positive subjects, but no binding was observed with sera collected from naive subjects. Sspara2 displayed excellent diagnostic potential with 98% sensitivity and 90% specificity observed for IgEbinding and 70% sensitivity for IgG. In contrast, the diagnostic sensitivity of Sspara3 was 84% for IgEbinding and 40% for IgG binding. In combination, Sspara2 and Sspara3 provided an IgEsensitivity of 94%. This study shows that IgEbinding to Sspara2 and Sspara3 is a highly sensitive method for diagnosis of scabiesinfestation in clinical practice. The developed enzyme-linked immunosorbent assay helps direct future development of a specific diagnostic tool for scabies.