During the previous funding cycle we identified five monoclonal antibodies (MAbs) against the P1 surface adhesin of Streptococcus mutans that redirect the humoral immune response in mice in terms of quantity, specificity and isotype of elicited antibodies when administered with the antigen as an immune complex. This strategy has implications for vaccine design in that protective immunity is not necessarily directed at immunodomiant epitopes of pathogens and could well be improved by shifting a response toward subdominant epitopes. Results varied depending on the anti-P1 MAb tested. Two MAbs resulted in formation of antibodies more inhibitory of S. mutans adherence in vitro and two others of less inhibitory antibodies. Epitopes recognized by a panel of anti-P1 MAbs were characterized and include complex discontinuous determinants. Polyclonal antibodies from immunized mice also recognize conformational epitopes, some of which appear more biologically relevant than others. Significant positive correlations were demonstrated between the ability of anti-P1 MAbs to inhibit S. mutans adherence and IgG2a and IgG2b isotypes suggesting the relevance of cytokines involved in class switching in the development of beneficial responses. This will be explored as part of the current proposal. Binding of an anti-P1 MAb to cell-associated P1 altered its susceptibility to numerous proteases in vitro indicating an influence on protein structure and suggesting exposure of cryptic epitopes and changes in antigen processing and presentation. Studies to address this potential mechanism of immunomodulation will also be undertaken. We will continue to characterize MAb-mediated changes in humoral immune responses in immunized mice to identify correlates of protection against S. mutans adherence in vitro and colonization and cariogenicity in vivo. Immunoassays of samples from immunized mice will utilize combinations of P1 segments, or deletion constructs, known to reconstitute or destroy conformational epitopes. The anti-P1 response against conformational determinants has not been studied to date in vaccinated animals or naturally sensitized humans. Immunomodulation by anti-P1 MAbs represents a strategy to significantly improve the humoral response against S. mutans and provides a tool to dissect beneficial and non-beneficial antibodies against this widely studied candidate vaccine antigen. The characterization of epitopes recognized by anti-P1 MAbs that improve or decrease the beneficial response will provide insight into the structure of P1 required to elicit optimal protective immunity and is expected to shed light on ways to modify the protein itself to improve its protective immunogenicity without the need to immunize with immune complexes. Beyond the impact of these studies on development of a therapeutic approach against human dental caries, the well-characterized P1 antigen and MAbs against it represent an excellent model system to understand the consequences and underlying molecular mechanisms of immunomodulation and would be of general interest for any active or passive immunization approach.

National Institute of Health (NIH)
National Institute of Dental & Craniofacial Research (NIDCR)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IHD (01))
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Lunsford, Dwayne
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University of Florida
Schools of Dentistry
United States
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Tang, Wenxing; Bhatt, Avni; Smith, Adam N et al. (2016) Specific binding of a naturally occurring amyloidogenic fragment of Streptococcus mutans adhesin P1 to intact P1 on the cell surface characterized by solid state NMR spectroscopy. J Biomol NMR 64:153-64
Robinette, Rebekah A; Heim, Kyle P; Oli, Monika W et al. (2014) Alterations in immunodominance of Streptococcus mutans AgI/II: lessons learned from immunomodulatory antibodies. Vaccine 32:375-82
Batista, Milene Tavares; Souza, Renata D; Ferreira, Ewerton L et al. (2014) Immunogenicity and in vitro and in vivo protective effects of antibodies targeting a recombinant form of the Streptococcus mutans P1 surface protein. Infect Immun 82:4978-88
Robinette, Rebekah A; Oli, Monika W; McArthur, William P et al. (2011) A therapeutic anti-Streptococcus mutans monoclonal antibody used in human passive protection trials influences the adaptive immune response. Vaccine 29:6292-300
Larson, Matthew R; Rajashankar, Kanagalaghatta R; Patel, Manisha H et al. (2010) Elongated fibrillar structure of a streptococcal adhesin assembled by the high-affinity association of alpha- and PPII-helices. Proc Natl Acad Sci U S A 107:5983-8
Tavares, Milene B; Silva, Bruno M; Cavalcante, Rafael C M et al. (2010) Induction of neutralizing antibodies in mice immunized with an amino-terminal polypeptide of Streptococcus mutans P1 protein produced by a recombinant Bacillus subtilis strain. FEMS Immunol Med Microbiol 59:131-42
Brady, L Jeannine; Maddocks, Sarah E; Larson, Matthew R et al. (2010) The changing faces of Streptococcus antigen I/II polypeptide family adhesins. Mol Microbiol 77:276-86
Robinette, Rebekah A; Oli, Monika W; McArthur, William P et al. (2009) Beneficial immunomodulation by Streptococcus mutans anti-P1 monoclonal antibodies is Fc independent and correlates with increased exposure of a relevant target epitope. J Immunol 183:4628-38
Ahn, Sug-Joon; Ahn, Sang-Joon; Wen, Zezhang T et al. (2008) Characteristics of biofilm formation by Streptococcus mutans in the presence of saliva. Infect Immun 76:4259-68
Crowley, Paula J; Seifert, Trevor B; Isoda, Ryutaro et al. (2008) Requirements for surface expression and function of adhesin P1 from Streptococcus mutans. Infect Immun 76:2456-68

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