Detection and characterization of mouse monoclonal antibodies to epidemic typhus rickettsiae.

A solid-phase immunofluorometric assay was used to detect mouse monoclonal antibodies to epidemic typhus rickettsiae, Rickettsia prowazekii (the immunizing antigen), and to murine typhus rickettsiae, Rickettsia typhi, a related antigen. Of the 649 hybridoma cultures obtained, 628 contained antibodies either to R. prowazekii or to both R. prowazekii and R. typhi. A total of 72 cultures were cloned by limiting dilution and yielded 137 antibody-producing clones. Of these, 104 produced antibodies specific for R. prowazekii, 22 produced antibodies that reacted with R. prowazekii and R. typhi, and 11 produced antibodies that reacted with R. prowazekii, R. typhi, and R. canada. The immunoglobulin isotypes of the mouse monoclonal antibodies produced were identified by a related indirect immunofluorometric assay technique with fluorescein isothiocyanate-conjugated antisera specific for each isotype. Antibodies were also evaluated by indirect fluorescent antibody tests, and antibodies from selected clones were found to neutralize rickettsial toxic activity in mice.