title: Antigenic heterogeneity in high- and low-virulence strains of Rickettsia rickettsii revealed by monoclonal antibodies.
abstract: Previously it has been reported that strains of Rickettsia rickettsii that differ greatly in their ability to cause disease in guinea pigs are similar by serological and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses. In this study, we used monoclonal antibodies to the virulent R and the relatively avirulent HLP strains to investigate strain differences which might account for the disparate behavior of the strains in guinea pigs. Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of the R and HLP strains were nearly identical for polypeptides with apparent molecular weights greater than 32 kilodaltons (kDa). All of the monoclonal antibodies to a lipopolysaccharide-like antigen reacted equally well with antigen from both strains by immunoblotting. None of the antibodies to the lipopolysaccharide-like antigen protected mice against challenge with viable rickettsiae. Some antibodies reacted with both 120- and 155-kDa polypeptides of both strains in radioimmune precipitation and immunoblotting tests, and other antibodies reacted only with the homologous strain. The monoclonal antibodies cross-reacted with the heterologous strain in the enzyme-linked immunosorbent assay essentially either completely or not at all. The ability of the monoclonal antibodies to the 120- and 155-kDa polypeptides to protect mice against the two strains was correlated with the ability of the antibodies to react with the antigens in the enzyme-linked immunosorbent assay and radioimmune precipitation or immunoblotting tests. These results demonstrate that R and HLP antigens which appear identical in molecular weight differ in their compositions of antigenic determinants.
authors.forename: R L
authors.initials: RL
authors.lastname: Anacker
authors.forename: R H
authors.initials: RH
authors.lastname: List
authors.forename: R E
authors.initials: RE
authors.lastname: Mann
authors.forename: D L
authors.initials: DL
authors.lastname: Wiedbrauk
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D000942:Antigens, Bacterial / Q000032:analysis*; D001426:Bacterial Proteins / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006168:Guinea Pigs; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D012284:Rickettsia rickettsii / Q000276:immunology* / Q000472:pathogenicity; D014774:Virulence
chemical_list: D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D008070:Lipopolysaccharides