[Enzyme-linked immunosorbent assay (ELISA) for Legionella pneumophila using 60-kDa protein antigen]

The enzyme-linked immunosorbent assay (ELISA) has been evaluated for the detection of antibodies against Legionella pneumophila. Three-grade antigens were prepared from Legionella pneumophila serogroup I. Crude antigen was made by enzyme digestion, sonication and centrifugation and then became half pure by ammonium sulfate precipitation. It was purified to form 60-kDa protein antigen by size-exclusion chromatography on a Sephacryl S400 column and ion-exchanged chromatography on a DEAE-5PW column. 60-kDa protein antigen was the most sensitive of the three antigens, but more cross reactive to K. pneumoniae type II than the other two antigens. It is suggested that crossreaction occurs on the grounds whether 60-kDa protein is antigen common to L. pneumophila serogroup I and K. pneumoniae type II or antigens of such two bacteria co-exist on 60-kDa protein.