Asian ladybugs (Harmonia axyridis): A new seasonal indoor allergen

BackgroundHarmonia axyridis, the Asian ladybug (ALB), was repeatedly introduced between 1916 and 1990. These beetles are intolerant to cold and move indoors during the winter.ObjectiveTo investigate sensitization to ALB.MethodsProteins in ALB extracts were purified by gel filtration and ion exchange chromatography. Purified fractions were screened for IgE antibody using the streptavidin CAP technique in sera from 20 patients with allergy living in ALB-infested houses. Two proteins were fully purified. Serum antibodies were also assessed in sera from 68 adult patients with asthma.ResultsFifteen of the 20 sera had measurable IgE antibody, 7 with high titers, > 10 IU/mL, to ALB extract. The 2 proteins, Har a 1, 10 kd, and Har a 2, 55 kd, bound IgE antibody in 65% and 75% of the sera, respectively. Sequencing revealed a novel N-terminal sequence for Har a 1. Sequencing of Har a 2 demonstrated homology to a dehydrogenase from the red flour beetle. Although sera from 18 of the patients with asthma were positive for IgE antibody to ALB, they were also positive to Blatella germanica. These subjects did not report exposure to H axyridis, and inhibition studies with B germanica blocked ≥ 95% of ALB IgE antibody binding.ConclusionTwo proteins of ALB have been purified and used to demonstrate that patients exposed to this beetle can develop high-titer IgE antibody. Cross-reactivity with B germanica was found but was significant only among patients primarily exposed to cockroaches.Clinical implicationsAsian ladybug has become an important seasonal indoor allergen in the United States.