RESUMO
We used wild-type and isogenic mutant strains of group A Streptococcus (GAS) that expressed M protein, capsule, or both to study the function of M protein and the hyaluronic acid capsular polysaccharide in attachment of GAS to human keratinocytes. Types 6 and 24, but not type 18, M protein were found to mediate attachment of GAS to soft palate or skin keratinocytes, but this interaction was prevented by the hyaluronic acid capsule on highly encapsulated, or mucoid, strains. Monoclonal antibody to CD44, the principal hyaluronic acid-binding receptor on keratinocytes, inhibited attachment of both highly encapsulated and poorly encapsulated wild type strains of GAS, but not the attachment of acapsular mutants. Transfection of K562 cells with cDNA encoding human CD44 conferred the capacity to bind each of six wild-type strains of GAS, but not to bind acapsular mutants. Because, in contrast to other potential adhesins, the group A streptococcal capsule is both highly conserved and surface-exposed, it may serve as a universal adhesin for attachment of diverse strains of GAS to keratinocytes of the pharyngeal mucosa and the skin.
Assuntos
Antígenos de Bactérias , Aderência Bacteriana/fisiologia , Proteínas da Membrana Bacteriana Externa , Proteínas de Bactérias/metabolismo , Proteínas de Transporte , Receptores de Hialuronatos/metabolismo , Ácido Hialurônico/metabolismo , Queratinócitos/imunologia , Queratinócitos/microbiologia , Streptococcus pyogenes/metabolismo , Adesinas Bacterianas/genética , Adesinas Bacterianas/metabolismo , Aderência Bacteriana/genética , Proteínas de Bactérias/classificação , Proteínas de Bactérias/genética , Sequência de Bases , Células Cultivadas , Primers do DNA/genética , Humanos , Receptores de Hialuronatos/genética , Ácido Hialurônico/genética , Queratinócitos/metabolismo , Ligantes , Microscopia de Fluorescência , Mutação , Reação em Cadeia da Polimerase , Infecções Estreptocócicas/etiologia , Streptococcus pyogenes/genética , Streptococcus pyogenes/patogenicidade , TransfecçãoAssuntos
Ácido Hialurônico/metabolismo , Queratinócitos/microbiologia , Streptococcus pyogenes/metabolismo , Streptococcus pyogenes/patogenicidade , Animais , Aderência Bacteriana/fisiologia , Linhagem Celular , Doenças do Tecido Conjuntivo/microbiologia , Modelos Animais de Doenças , Humanos , Queratinócitos/ultraestrutura , Camundongos , Microscopia Eletrônica , Dermatopatias Bacterianas/microbiologia , Infecções Estreptocócicas/microbiologia , Streptococcus pyogenes/ultraestrutura , Virulência/fisiologiaRESUMO
It has been suggested that entry of pathogenic bacteria, including streptococci, into epithelial cells may represent an early stage of invasive infections. We found that poorly encapsulated wild-type strains and unencapsulated mutants of group A Streptococcus entered cultured human keratinocytes with high efficiency, while strains that produced large amounts of hyaluronic acid capsule did not, regardless of M-protein type or clinical source of the isolate. However, encapsulated streptococci produced extensive local necrosis and systemic infection in a mouse model of skin infection, while an isogenic acapsular strain did not. The results implicate the hyaluronic acid capsule as a virulence factor in soft tissue infection. Entry of poorly encapsulated group A Streptococcus into human epithelial cells does not appear to represent an initial step in invasive disease; rather, the capacity of encapsulated strains to avoid uptake by epithelial cells is associated with enhanced virulence in skin and soft tissue infection.
