Immunogenicity and prediction of epitopic region of antigen Ag I/II and glucosyltransferase from Streptococcus mutans

Antibodies generated against dextransucrase exhibit potential anticariostatic properties in Streptococcus mutans

Streptococcus mutans is a common principal causative agent of dental caries. In this communication, we describe that the antibodies raised against purified dextransucrase effectively inhibited the growth of S. mutans. The purified enzyme showed 58-fold enrichment, 17.5% yield and a specific activity of 3.96 units/mg protein. Purified IgG fraction of the antibody showed significant affinity with the antigenic protein. Immunotritation of the enzyme with dextransucrase antibody showed a gradual increase in inhibition of dextransucrase activity. The growth of S. mutans was also inhibited by 85% in the presence of 28 μg of IgG fraction of the antibody. Antibodies also impaired glucosyltransferase activity (72.8%) and biofilm formation by 92.6% in S. mutans. Western blot analysis revealed no cross reactivity with the various tissues of mice, rat, rabbit and humans. Dot blot analysis showed little reactivity with Lactobacillus acidophilus and Staphylococcus aureus and there was no reactivity with other bacterial strains like Enterococcus faecalis, Escherichia coli and Salmonella typhimurium. These findings suggest that antibody raised against dextransucrase exhibit inhibitory effects on the growth of S. mutans and biofilm formation with no reactivity with various mammalian tissues, thus it could be an effective anticariogenic agent.

Dental caries vaccine: are we there yet?

Dental caries, caused by Streptococcus mutans, is a common infection. Caries vaccine has been under investigation for the last 40 years. Many in vitro and in vivo studies and some human clinical trials have determined many pertinent aspects regarding vaccine development. The virulence determinants of Strep. mutans, such as Ag I/II, responsible for adherence to surfaces, glucosyltransferase, responsible for the production of glucan, and the glucan-binding protein, responsible for the attachment of glucan to surfaces, have been known to elicit an antigen-specific immune response. It is also known that more than one antigen or a functional part of the genome responsible for these virulence determinants provide a better host response compared with the monogenic vaccine or complete genome of a specific antigen. To enhance the host response, the use of adjuvants has been studied and the routes of antigen administration have been investigated. In recent years, some promising vaccines such as pGJA-P/VAX, LT derivative/Pi_39-512 , KFD2-rPAc and SBR/GBR-CMV-nirB have been developed and tested in animals. New virulence targets need to be explored. Multicentre collaborative studies and human clinical trials are required and some interest from funders and public health experts should be generated to overcome this hurdle. SIGNIFICANCE AND IMPACT OF THE STUDY: Dental caries is an irreversible, multifactorial opportunistic infection. The treatment is costly, making it a public health problem. Despite many years of promising laboratory research, animal studies and clinical trials, there is no commercially available vaccine today. The research objectives have become more refined from lessons learnt over the years. Multigenic DNA/recombinant vaccines, using the best proved adjuvants with a delivery system for the nasal or sublingual route, should be developed and researched with multicentre collaborative efforts. In addition, new vaccine targets can be identified. To overcome the economic hurdle, funders and public health interest should be stimulated.

Self-assembling anticaries mucosal vaccine containing ferritin cage nanostructure and glucan-binding region of S. mutans glucosyltransferase effectively prevents caries formation in rodents

Anticaries protein vaccines that induce a mucosal immune response are not effective. Therefore, development of effective and convenient anticaries vaccines is a priority of dental research. Here we generated self-assembling nanoparticles by linking the glucan-binding region of Streptococcus mutans glucosyltransferase (GLU) to the N-terminal domain of ferritin to determine whether these novel nanoparticles enhanced the immunogenicity of an anticaries protein vaccine against GLU in rodents. We constructed the expression plasmid pET28a-GLU-FTH and purified the proteins from bacteria using size-exclusion chromatography. BALB/c mice were used to evaluate the ability of GLU-ferritin (GLU-FTH) nanoparticles to induce GLU-specific mucosal and systemic responses. The protective efficiency of GLU-FTH nanoparticles was compared with that of GLU alone or a mixture of GLU and poly(I:C) after administering an intranasal infusion to Wistar rats. The phagocytosis and maturation of dendritic cells (DCs) exposed in vitro to the nanoparticles were assessed using flow cytometry. The GLU-FTH nanoparticle vaccine elicited significantly higher levels of GLU-specific antibodies compared with GLU or a mixture of GLU and poly(I:C). Immunization with GLU-FTH achieved lower caries scores compared with those of the other vaccines. Administration of GLU-FTH nanoparticles enhanced phagocytosis by DCs and their maturation. Thus, self-assembling GLU-FTH is a highly effective anticaries mucosal vaccine that enhanced antibody production and inhibited S. mutans infection in rodents.