Detection of antibodies to Legionella pneumophila in immune guinea pig serum by solid-phase immunofluorescence.

A semiautomated solid-phase immunofluorescence apparatus (FIAX; International Diagnostic Technology, Santa Clara, Calif.) was utilized to develop a rapid method for detection of antibody to Legionella pneumophila. The sera from guinea pigs immunized with a mixture of killed L. pneumophila and Freund complete adjuvant displayed markedly enhanced antibody activity as measured by FIAX when compared with that obtained from adjuvant-injected or unimmunized animals. A correlation was observed between FIAX net fluorescence units and microagglutination titers of serum samples obtained from immunized animals. Within-run and between-run coefficients of variation performed on selected immune serum samples were low. These results demonstrated that the FIAX method could readily and reproducibly detect Legionella-specific antibodies in the sera of actively immunized animals and suggest the possibility of a broader application of FIAX in the serological detection of exposure to L. pneumophila antigen.