RESUMEN
Staphylococcus aureus is considered to be an extracellular pathogen. However, survival of S. aureus within host cells may provide a reservoir relatively protected from antibiotics, thus enabling long-term colonization of the host and explaining clinical failures and relapses after antibiotic therapy. Here we confirm that intracellular reservoirs of S. aureus in mice comprise a virulent subset of bacteria that can establish infection even in the presence of vancomycin, and we introduce a novel therapeutic that effectively kills intracellular S. aureus. This antibody-antibiotic conjugate consists of an anti-S. aureus antibody conjugated to a highly efficacious antibiotic that is activated only after it is released in the proteolytic environment of the phagolysosome. The antibody-antibiotic conjugate is superior to vancomycin for treatment of bacteraemia and provides direct evidence that intracellular S. aureus represents an important component of invasive infections.
Asunto(s)
Antibacterianos/farmacología , Bacteriemia , Inmunoconjugados/farmacología , Inmunoconjugados/uso terapéutico , Espacio Intracelular/microbiología , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/efectos de los fármacos , Vancomicina/farmacología , Animales , Antibacterianos/uso terapéutico , Bacteriemia/tratamiento farmacológico , Bacteriemia/microbiología , Portador Sano/tratamiento farmacológico , Portador Sano/microbiología , Diseño de Fármacos , Femenino , Inmunoconjugados/química , Espacio Intracelular/efectos de los fármacos , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Staphylococcus aureus Resistente a Meticilina/patogenicidad , Ratones , Pruebas de Sensibilidad Microbiana , Fagosomas/efectos de los fármacos , Fagosomas/metabolismo , Fagosomas/microbiología , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/patología , Staphylococcus aureus/patogenicidad , Vancomicina/uso terapéuticoRESUMEN
Infection of host tissues by Staphylococcus aureus and S. epidermidis requires an unusual family of staphylococcal adhesive proteins that contain long stretches of serine-aspartate dipeptide-repeats (SDR). The prototype member of this family is clumping factor A (ClfA), a key virulence factor that mediates adhesion to host tissues by binding to extracellular matrix proteins such as fibrinogen. However, the biological siginificance of the SDR-domain and its implication for pathogenesis remain poorly understood. Here, we identified two novel bacterial glycosyltransferases, SdgA and SdgB, which modify all SDR-proteins in these two bacterial species. Genetic and biochemical data demonstrated that these two glycosyltransferases directly bind and covalently link N-acetylglucosamine (GlcNAc) moieties to the SDR-domain in a step-wise manner, with SdgB appending the sugar residues proximal to the target Ser-Asp repeats, followed by additional modification by SdgA. GlcNAc-modification of SDR-proteins by SdgB creates an immunodominant epitope for highly opsonic human antibodies, which represent up to 1% of total human IgG. Deletion of these glycosyltransferases renders SDR-proteins vulnerable to proteolysis by human neutrophil-derived cathepsin G. Thus, SdgA and SdgB glycosylate staphylococcal SDR-proteins, which protects them against host proteolytic activity, and yet generates major eptopes for the human anti-staphylococcal antibody response, which may represent an ongoing competition between host and pathogen.