A partially purified antigen from Faenia rectivirgula in the diagnosis of farmer's lung disease.

An antigen fraction from Faenia rectivirgula (Micropolyspora faeni) having diagnostic significance for farmer's lung disease was isolated by Sephadex G-200 and G-100 fractionations. Antibody raised against this antigen fraction was used to make an immunoaffinity column to purify crude culture filtrate antigens of F. rectivirgula. The antigen has a molecular weight of 66,000 and an isoelectric point between pH 6.0 and 6.5. The yield of this antigen fraction was 1.02% of the total protein of the crude antigen. Although the crude antigen showed activity for several enzymes, the purified antigen showed enhanced activity for acid phosphatase and beta-glucosidase. Using this antigen fraction, an ELISA was developed for detecting circulating specific IgG antibody in farmer's lung patients. The antigen can be standardized by its immunochemical characteristics and may be used to detect circulating antibodies in the sera of patients with dependability and reproducibility.