Immunogenicity and In Vitro and In Vivo Protective Effects of Antibodies Targeting a Recombinant Form of the Streptococcus mutans P1 Surface Protein

Abstract

b 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.

Sublingual immunization with the phosphate‐binding‐protein (PstS) reduces oral colonization by Streptococcus mutans

“…We also determined if the vaccination would confer active protective immunity to oral colonization by the S. mutans NG8 strain. For this proposal, 3 weeks after the last dose, mice were submitted to oral prophylaxis and inoculated with S. mutans , as previously reported (Batista et al ., ). As observed in the previous experiment, a decrease in the number of bacteria recovered from the oral cavity was reproducibly observed in mice immunized with rPstS alone or co‐administered with the mucosal adjuvant, compared with the control group, indicating that anti‐PstS antibodies recognized the native protein expressed on the bacterium surface (Fig.…”

“…Furthermore, we noticed that rPstS alone induced a Th2 profile, with higher levels of IgG1 and IL‐6; however, the co‐administration with LTK4R incremented the levels of the IgG2a antibody subclass and IFN‐γ. This profile trend for LTK4R has been observed by other authors (Rodrigues et al ., ; Batista et al ., ).…”

“…Specific IgG antibodies, raised after sublingual immunization with rPstS, impaired oral colonization of naive mice and conferred partial protection from oral colonization in vaccinated mice. Serum neutralization data were comparable to the levels obtained in a previous study performed by our group using P1 39–512 protein as the target antigen (Batista et al ., ). However, when comparing animals immunized with P1 39–512 or PstS in the presence of the same adjuvant, we observed that both antigens reduced the oral colonization of vaccinated mice challenged with the S. mutans NG8 strain.…”

“…The antibody activities against in vivo tooth colonization were tested in mice according to the protocol described by Batista et al . (). Cells from the S. mutans NG8 strain were treated and pre‐incubated with pooled sera (diluted 1 : 100) from immunized groups.…”

Dental caries vaccine: are we there yet?

“…The requirement of adequate adjuvants and the routes of administration were investigated. Liposomes (phospholipid membrane vesicles), alum, bacterial flagellin and enterotoxins as adjuvants also proved to be better in eliciting an immune response (Childers et al 1999;Batista et al 2014;Yang et al 2017). Based on these findings, research expanded to DNA/recombinant vaccines.…”