RESUMO
Rickettsia helvetica is an obligate intracellular Gram-negative microorganism found in Ixodes ricinus ticks. When R. helvetica was first discovered in 1979, little was known about its physiology and it fell into oblivion until it recently was suspected of being pathogenic to humans. However, all efforts to isolate R. helvetica from patients have been unsuccessful, although serological responses against R. helvetica can be demonstrated. The aim of our study was to investigate the protein profile of R. helvetica and study the antigenicity of its proteins using two-dimensional (2D) immunoblot in order to characterize the immunological response against R. helvetica infection. Our results show that in addition to the known PS120 and OmpB antigenic R. helvetica proteins, three other antigens exist: a 60 kDa GroEL protein, a 10 kDa GroES protein and a hitherto unknown 35 kDa hypothetical protein that has similarities with ORF-RC0799 of Rickettsia conorii. Furthermore, the lipopolysaccharide showed strong antigenicity. In this study, we present the first proteome map and the first 2D immunoblot profile of R. helvetica and finally we present the 35 kDa R. helvetica as an additional antigen to the previously known rickettsial antigens.
Assuntos
Antígenos de Bactérias/imunologia , Ixodes/microbiologia , Rickettsia/imunologia , Animais , Antígenos de Bactérias/química , Antígenos de Bactérias/isolamento & purificação , Centrifugação com Gradiente de Concentração , DNA Bacteriano/química , DNA Bacteriano/genética , Eletroforese em Gel Bidimensional , Immunoblotting , Ponto Isoelétrico , Peso Molecular , Reação em Cadeia da Polimerase , Proteômica/métodos , Rickettsia/química , Rickettsia/genética , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
Sweden is an area potentially endemic for spotted fever rickettsioses. Rickettsia helvetica has been isolated from its tick vector Ixodes ricinus, and in a handful of cases linked to human disease. This study demonstrates for the first time in Sweden the transmission of rickettsial infection after a tick bite and the attack rate in an endemic area. We present three cases of documented rickettsial infection and a prospective serological study of Swedish recruits who were trained in the area where the patients lived and showed seroconversion to spotted fever rickettsiae. All patients showed a four-fold increase in antibody titer to the spotted fever rickettsia, R. helvetica, and immunohistochemical examination revealed rickettsia-like organisms in the walls of skin capillaries and veins. Electron microscopy showed organisms resembling R. helvetica and immunogold labeling with two anti-rickettsial antibodies demonstrated specific labeling of the rickettsial organisms in the skin biopsy specimens. Eight of the thirty-five recruits showed a four-fold increase in IgG titer reflecting a high rate of exposure. The results of this study demonstrate that spotted fever rickettsioses should be taken into consideration in the diagnosis of tick-transmitted infections in Sweden.
