RESUMO
Ehrlichia chaffeensis and Ehrlichia canis are tick-transmitted rickettsial pathogens that cause human and canine monocytic ehrlichiosis respectively. We tested the hypothesis that these pathogens express unique proteins in response to their growth in vertebrate and tick host cells and that this differential expression is similar in closely related Ehrlichia species. Evaluation of nine E. chaffeensis isolates and one E. canis isolate demonstrated that protein expression was host cell-dependent. The differentially expressed proteins included those from the p28/30-Omp multigene locus. E. chaffeensis and E. canis proteins expressed in infected macrophages were primarily the products of the p28-Omp 19 and 20 genes or their orthologues. In cultured tick cells, E. canis expressed only the p30-10 protein, an orthologue of the E. chaffeensis p28-Omp 14 protein which is the only protein expressed by E. chaffeensis propagated in cultured tick cells. The expressed Omp proteins were post-translationally modified to generate multiple molecular forms. E. chaffeensis gene expression from the p28/30-Omp locus was similar in tick cell lines derived from both vector (Amblyomma americanum) and non-vector (Ixodes scapularis) ticks. Differential expression of proteins within the p28/p30-Omp locus may therefore be vital for adaptation of Ehrlichia species to their dual host life cycle.
Assuntos
Proteínas da Membrana Bacteriana Externa/metabolismo , Ehrlichia canis/metabolismo , Ehrlichia chaffeensis/metabolismo , Macrófagos/microbiologia , Carrapatos/microbiologia , Sequência de Aminoácidos , Animais , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Bactérias/análise , Proteínas de Bactérias/genética , Northern Blotting , Western Blotting , Linhagem Celular , Cromatografia Líquida/métodos , Ehrlichia canis/genética , Ehrlichia canis/crescimento & desenvolvimento , Ehrlichia chaffeensis/genética , Ehrlichia chaffeensis/crescimento & desenvolvimento , Eletroforese em Gel Bidimensional/métodos , Feminino , Regulação Bacteriana da Expressão Gênica/genética , Glicoproteínas/química , Glicoproteínas/metabolismo , Espectrometria de Massas/métodos , Dados de Sequência Molecular , Família Multigênica/genética , Fosforilação , Proteômica/métodos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Carrapatos/citologiaRESUMO
Ehrlichia chaffeensis, a tick-transmitted rickettsial agent, causes human monocyte/macrophage-tropic ehrlichiosis. In this study, proteomic approaches were used to demonstrate host cell-specific antigenic expression by E. chaffeensis. The differentially expressed antigens include those from the 28-kDa outer membrane protein (p28-Omp) multigene locus. The proteins expressed in infected macrophages are the products of p28-Omp19 and p28-Omp20 genes, whereas in tick cells, the protein expressed is the p28-Omp14 gene product. The differentially expressed proteins are posttranslationally modified by phosphorylation and glycosylation to generate multiple expressed forms. Host cell-specific protein expression is not influenced by growth temperatures and is reversible. Host cell-specific protein expression coupled with posttranslational modifications may be a hallmark for the pathogen's adaptation to a dual-host life cycle and its persistence.
