Identification and Characterization of an Arginine Kinase as a Major Allergen from Silkworm <i>(Bombyx mori)</i> Larvae

<i>Background:</i> The silkworm, <i>Bombyx mori</i>, is an important insect in the textile industry and its pupa are used in Chinese cuisine and traditional Chinese medicine. The silk, urine and dander of silkworms is often the cause of allergies in sericulture workers and the pupa has been found to be a food allergen in China. Recent studies have focused on reporting cases of silkworm allergies, but only a few studies have addressed the specific allergens present in the <i>B. mori</i> silkworm.<i> Methods:</i> We collected sera from 10 patients with a positive skin prick test to silkworm crude extract (SCE) and analyzed these samples by Western blot and ELISA. The cDNA of arginine kinase from the <i>B. mori</i> silkworm was also cloned and expressed in high yield in <i>Escherichia coli. </i>Allergenicity and cross-allergenicity of the recombinant <i>B. mori</i> arginine kinase (r<i>Bm</i>AK) were investigated by ELISA inhibition assay. <i>Results:</i> Collected sera all reacted to a 42-kDa protein in a Western blot with SCE as the antigen. Preincubation of sera with r<i>Bm</i>AK eliminated the reactivity of the patients’ sera to this 42-kDa band. All patient sera also exhibited positive reactivity to SCE in an ELISA assay. <i>Bm</i>AK also demonstrated cross-reactivity with a recombinant AK from cockroach. <i>Conclusion:</i> Arginine kinase from the <i>B. mori</i> silkworm is a major allergen and crossreacts with cockroach AK.