RESUMO
Streptococcus mutans is a major etiologic agent of dental caries, a prevalent worldwide infectious disease and a serious public health concern. The surface-localized S. mutans P1 adhesin contributes to tooth colonization and caries formation. P1 is a large (185-kDa) and complex multidomain protein considered a promising target antigen for anticaries vaccines. Previous observations showed that a recombinant P1 fragment (P1(39-512)), produced in Bacillus subtilis and encompassing a functional domain, induces antibodies that recognize the native protein and interfere with S. mutans adhesion in vitro. In the present study, we further investigated the immunological features of P1(39-512) in combination with the following different adjuvants after parenteral administration to mice: alum, a derivative of the heat-labile toxin (LT), and the phase 1 flagellin of S. Typhimurium LT2 (FliCi). Our results demonstrated that recombinant P1(39-512) preserves relevant conformational epitopes as well as salivary agglutinin (SAG)-binding activity. Coadministration of adjuvants enhanced anti-P1 serum antibody responses and affected both epitope specificity and immunoglobulin subclass switching. Importantly, P1(39-512)-specific antibodies raised in mice immunized with adjuvants showed significantly increased inhibition of S. mutans adhesion to SAG, with less of an effect on SAG-mediated bacterial aggregation, an innate defense mechanism. Oral colonization of mice by S. mutans was impaired in the presence of anti-P1(39-512) antibodies, particularly those raised in combination with adjuvants. In conclusion, our results confirm the utility of P1(39-512) as a potential candidate for the development of anticaries vaccines and as a tool for functional studies of S. mutans P1.
Assuntos
Adesinas Bacterianas/imunologia , Anticorpos Antibacterianos/imunologia , Cárie Dentária/prevenção & controle , Proteínas de Membrana/imunologia , Infecções Estreptocócicas/prevenção & controle , Vacinas Estreptocócicas/imunologia , Streptococcus mutans/imunologia , Adesinas Bacterianas/genética , Adjuvantes Imunológicos/administração & dosagem , Aglutininas/metabolismo , Animais , Anticorpos Antibacterianos/sangue , Bacillus subtilis/genética , Aderência Bacteriana , Cárie Dentária/imunologia , Feminino , Proteínas de Membrana/genética , Camundongos Endogâmicos BALB C , Boca/microbiologia , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Saliva/metabolismo , Infecções Estreptocócicas/imunologia , Vacinas Estreptocócicas/administração & dosagem , Vacinas Estreptocócicas/genética , Streptococcus mutans/genética , Vacinas Sintéticas/administração & dosagem , Vacinas Sintéticas/genética , Vacinas Sintéticas/imunologiaRESUMO
Bacillus subtilis spores have been used as safe and heat-resistant antigen delivery vectors. Nonetheless, the oral administration of spores typically induces weak immune responses to the passenger antigens, which may be attributed to the fast transit through the gastrointestinal tract. To overcome this limitation, we have developed B. subtilis spores capable of binding to the gut epithelium by means of expressing bacterial adhesins on the spore surface. The resulting spores bound to in vitro intestinal cells, showed a longer transit through the mouse intestinal tract, and interacted with Peyer's patch cells. The adhesive spores increased the systemic and secreted antibody responses to the Streptococcus mutans P1 protein, used as a model antigen, following oral, intranasal, and sublingual administration. Additionally, P1-specific antibodies efficiently inhibited the adhesion of the oral pathogen Streptococcus mutans to abiotic surfaces. These results support the use of gut-colonizing B. subtilis spores as a new platform for the mucosal delivery of vaccine antigens.