Antigens of Rickettsia conorii recognized by seropositive healthy people from Salamanca (Central-West Spain)

The antigenic reactivity in Western immunoblotting assay of individual Rickettsia conorii components with sera of healthy people living in Salamanca Province, an endemic zone of Mediterranean spotted fever, is evaluated. Polypeptides of molecular weights 100 kDa (92.7%), 135 kDa (75.6%), 160 kDa (70.7%) and 115 kDa (48.8%) were recognized by a higher proportion of sera with indirect immunofluorescent antibody test titers ≥ 1:80. Reaction with apparent rickettsial lipopolysaccharide was found in 15 (36.6%) of these samples. The involvement of different rickettsial strains, atypical routes of inoculation, varying content of the inoculum, and host factors may be determinants of the clinical expression of the spotted fever group rickettsial infection in people who produce antibodies reactive with Rickettsia conorii antigens.