Partial purification and characterization of the major species-specific protein antigens of Rickettsia typhi and Rickettsia prowazekii identified by rocket immunoelectrophoresis

Abstract

Species-specific antigens from Rickettsia typhi and Rickettsia prowazekii were readily solubilized by French pressure cell extraction or sonication of Renografin density gradient-purified rickettsiae and were identified by rocket immunoelectrophoresis. As measured by quantitative rocket immunoelectrophoresis, the species-specific typhus rocket antigens (STRAs) appeared to be proteins; they were denatured by heating at 560C for 30 min but not by 50°C treatment, and they were sensitive to pronase and trypsin but were not affected by periodate oxidation, glycosidases of various specificities, phospholipase A, or lipase. STRAs from both R. typhi and R. prowazekii were separated from common antigens by DE52 column chromatography of 100,000-x-g supernatant fractions of rickettsial extracts. The purified STRAs were characterized by crossed immunoelectrophoresis, by polyacrylamide gel electrophoresis on Davis and sodium dodecyl sulfate gels, and by an enzyme-linked immunosorbent assay. The two purified STRAs were proteins with similar native electrophoretic mobilities in agarose and polyacrylamide gels, and these proteins had similar polypeptide pattems on sodium dodecyl sulfate gels. Most of the STRA activity migrated as a single protein band on sodium dodecyl sulfate-polyacrylamide and Davis polyacrylamide gels, although minor protein bands with STRA activity were also detected. The major STRA proteins constituted 10 to 15% of the total cellular protein of R. typhi and R. prowazekii. According to sensitive enzyme-linked immunosorbent assay titrations, the STRA of R. prowazekii had substantial cross-reactivity with rabbit antiserum prepared against R. typhi, as shown also by rocket immunoelectrophoresis, whereas the STRA of R. typhi reacted only very weakly with antiserum prepared against R. prowazekii according to the enzyme-linked immunosorbent assay and not at all according to rocket immunoelectrophoresis.

Evasion of autophagy mediated by Rickettsia surface protein OmpB is critical for virulence

“…Alternatively, OmpB may camouflage the bacterial surface, either directly and/or via its role in formation of a capsule-like halo. In support of these hypotheses, OmpB makes up more than 10% of the cellular protein mass 35 and is thus abundant enough for a camouflaging role. Moreover, a role for the OmpB-dependent capsule-like halo would be consistent with speculation that the capsule O-antigen shields Francisella tularensis from ubiquitylation 23 .…”

Antigenic relationships among the rickettsiae of the spotted fever and typhus groups

“…Antibodies to this protein were mainly species-specific and groupspecific; weaker reactions occurred with 135-kDa antigens of the heterologous groups. The prominence in Coomassie blue-stained gels and the patterns of migration and immunoreactivity suggest that the protective species-specific antigens (SPA) of the typhus rickettsiae described by Dasch et al [6,15] belong to this family of antigens.…”

Cloning and Sequencing of the Gene Encoding the Candidate HtrA of Rickettsia typhi

“…Together with R. prowazekii, R. typhi belongs to the typhus group of rickettsiae. Both bacteria possess crystalline surface layer proteins as their outermost component of the cell envelope, which elicit dominant antibody reactions demonstrated by rocket immunoelectrophoresis (3). Previously, we cloned and characterized this gene of R. typhi (5).…”