Serogroup-specific and serogroup-cross-reactive epitopes of Legionella pneumophila.

A panel of monoclonal antibodies was used to serotype 343 Legionella pneumophila isolates, using the indirect immunofluorescence test and ELISA. In addition, the isolates were typed by means of absorbed rabbit antisera to provide a reference procedure. As shown by a comparison of reaction patterns, serogroup-specific monoclonal antibodies were found for serogroups 1, 2, 3, 4, 6, 7, 8, and 10. Monoclonal subtypes were found to exist within serogroups 1, 2, 5, and 6. Using the monoclonal antibody panel introduced for serogroups 1 to 8 and 10, it was possible to serotype or subtype 92% of the isolates tested. The remaining isolates belonged to serogroups 9, 11 to 14 and to a monoclonal subtype of serogroup 5. 8 monoclonal antibodies recognized serogroup-cross-reactive epitopes. Except for serogroups 1, 7, and 11, all others shared a common antigenic determinant. Another common epitope was shared by strains of serogroups 2 and 3. Additional cross-reactivity was associated in particular with strains of serogroups 5, 8, and 10.