Bla g 6, a German cockroach allergen, shows homology to muscle protein troponin C. It contains four calciumbinding domains at 20-30, 56-67, 96-107, and 132-143 amino acid (aa) residues, and its immunoglobulin E (IgE) reactivity is dependent upon calcium ion level. However, the IgE binding epitopes of Bla g 6 have not been investigated. This study aimed to analyze the IgE binding epitopes from the five peptide fragments of Bla g 6. The full-length of three Bla g 6 isoallergens (Bla g 6.0101, Bla g 6.0201, and Bla g 6.0301) and five peptide fragments (P1: aa 1-111, P2: aa 1-95, P3: aa 33-111, P4: aa 80-151, and P5: aa 33-151) of Bla g 6.0101 were generated by polymerase chain reaction (PCR) and expressed in Escherichia coli. Enzyme-linked immunosorbent assay (ELISA) was performed on 24 patients' sera that adjusted the final concentration 10 mM of CaCl2 to determine the IgE activities of Bla g 6. Eight sera (33.3%), 9 sera (37.5%), and 11 sera (45.8%) showed IgE reactivity to Bla g 6.0101, Bla g 6.0201, and Bla g 6.0301, respectively. Among the sera from the positive IgE reactivity, three patients' sera were selected and the IgE reactivity was measured by ELISA with the five peptide fragments of Bla g 6. Based on IgE responses, one patient's serum exhibited the strongest IgE reactivity. We assumed that the aa between 96-151 residues, including the calcium binding domains III and IV, would be important for IgE binding. These results may provide information that will yield safe diagnostic methods and immunotherapeutics.
All Science Journal Classification (ASJC) codes
- Structural Biology