A WHO position paper states that allergen immunotherapy is an effective treatment for allergic diseases, and well characterized allergens should be used in immunotherapy. The house dust mite is a major cause of allergic disease. However, the biological activity of the mite extracts currently used cannot be clearly determined, since these extracts contain various impurities. The use of recombinant allergens can avoid this problem. However, there remains a risk of contamination by other impurities, such as host cell-derived proteins (HCPs). Advanced purification techniques are thus required to remove these contaminants. C8/119S is a mutant of the major house dust mite allergen Der f 2, and is expressed and accumulated as an inclusion body in Escherichia coil. The C8/119S was refolded and purified through three column chromatography steps. Using this method, we could obtain about 2 g of the purified C8/119S in one purification batch. This amount is equivalent to 100,000 of the maintenance doses required for immunotherapy based on the WHO position paper. The purity of the C8/119S was 99% or more. The antigenicity of HCPs in the C8/119S was examined by passive cutaneous anaphylaxis assays. When the C8/119S was administered at 40 mu g/kg, no local anaphylaxis was observed. C8/1195 was thus highly purified with an extremely low level of impurities, and our procedure was shown to he an effective advanced production-scale purification process for this Der 12 mutant. In this study, we established an advanced purification processes for C8/119S, then characterized the purified C8/119S and evaluated its purity. (C) 2010, The Society for Biotechnology, Japan. All rights reserved.