Dermatitis Caused by Moths of Hylesia Genus (Lepidoptera, Saturniidae) in Northeastern States of Venezuela: II. Biochemistry and Immunoallergy of Substances Responsible for Dermal Lesions

Dart-like setae (fléchettes) shed abundantly by Hylesia metabus adult females and carrying urticant substances are responsible for the severe urticarial and papulovesicular dermatitis produced upon their contact with skin. Its pathogenesis is not well understood and knowledge about the biochemistry and immunology of the irritative substances is scarce. Histamine has been implicated in this reaction but we have been able to detect a substance in the aqueous extract of female adults, that when concentrated and applied as a patch test on human skin, produces within a short time a necrotic lesion that takes many months to heal. Enzymatic assays point at being of tryptic nature but devoid of hyaluronidase, phospholipase, and glycolytic activities. However, it is not yet clear to us whether this enzymatic-like substance is responsible for the immediate, reaginic type of skin reaction produced by the intradermal injection of a very dilute aqueous extract of the moths and / or of the late-phase cutaneous reaction that which starts 6 to 8 hours later and lasts for 2 to 3 days. This reaction is IgE mediated, as shown by passive transfer and direct RAST testing. The reaginic content of serum to moth antigens decreases when the person avoids contact with the allergen source. The IEF patterns generated by the moth extracts showed that they contain multiple protein components although the pattern generated by each extract was unique. Immunoblotting suggests that the components of these extracts with high or basic isoelectric points (pl < 8.0) might be involved in this IgE-mediated reaction. The IgE binding components of the silk worm (Bombyx mori), a closely related species, appear at different pl values.