Levels and complexity of IgA antibody against oral bacteria in samples of human colostrum.

Streptococcus mutans (SM) have three main virulence antigens: glucan binding protein B (gbpB), glucosyltransferase (Gtf) and antigens I/II (Ag I/II) envolved in the capacity of those bacteria to adhere and accumulate in the dental biofilm. Also, the glycosyltransferases 153 kDa of Streptococcus gordonii (SGO) and 170kDa of Streptococcus sanguinis (SSA) were important antigens associated with the accumulation of those bacterias. Streptococcus mitis (SMI) present IgA1 protease of 202 kDa. We investigated the specificity and levels IgA against those antigens of virulence in samples of human colostrum. This study involved 77 samples of colostrum that were analyzed for levels of immunoglobulian A, M and G by Elisa. The specificity of IgA against extracts of SM and initials colonizators (SSA, SMI, SGO) were analyzed by the Western blot. The mean concentration of IgA was 2850.2 (±2567.2) mg/100 mL followed by IgM and IgG (respectively 321.8±90.3 and 88.3±51.5), statistically different (p<0.05). Results showed that the majority of samples had detectable levels of IgA antibodies to extracts of bacteria antigens and theirs virulence antigens. To SM, the GbpB was significantly lower detected than others antigens of SM (p<0.05). High complexities of response to Ags were identified in the samples. There were no significant differences in the mean number of IgA-reactive Ags between the antigens (p>0.4). So, the breast milk from first hours after birth presented significant levels of IgA specific against important virulence of antigens those oral streptococci, which can disrupt the installation and accumulation process of these microorganisms in the oral cavity.

Mutans streptococcal infection induces salivary antibody to virulence proteins and associated functional domains.

The interplay between mucosal immune responses to natural exposure to mutans streptococci and the incorporation and accumulation of these cariogenic microorganisms in oral biofilms is unclear. An initial approach to explore this question would be to assess the native secretory immunity emerging as a consequence of Streptococcus mutans infection. To this end, we analyzed salivary immunoglobulin A (IgA) antibody to mutans streptococcal glucosyltransferase (Gtf) and glucan binding protein B (GbpB) and to domains associated with enzyme function and major histocompatibility complex (MHC) class II binding in two experiments. Salivas were collected from approximately 45-day-old Sprague-Dawley rats, which were then infected with S. mutans SJ32. Infection was verified and allowed to continue for 2 to 2.5 months. Salivas were again collected following the infection period. Pre- and postinfection salivas were then analyzed for IgA antibody activity using peptide- or protein-coated microsphere Luminex technology. S. mutans infection induced significant levels of salivary IgA antibody to Gtf (P < 0.002) and GbpB (P < 0.001) in both experiments, although the levels were usually far lower than the levels achieved when mucosal immunization is used. Significantly (P < 0.035 to P < 0.001) elevated levels of postinfection salivary IgA antibody to 6/10 Gtf peptides associated with either enzyme function or MHC binding were detected. The postinfection levels of antibody to two GbpB peptides in the N-terminal region of the six GbpB peptides assayed were also elevated (P < 0.031 and P < 0.001). Interestingly, the patterns of the rodent response to GbpB peptides were similar to the patterns seen in salivas from young children during their initial exposure to S. mutans. Thus, the presence of a detectable postinfection salivary IgA response to mutans streptococcal virulence-associated components, coupled with the correspondence between rat and human mucosal immune responsiveness to naturally presented Gtf and GbpB epitopes, suggests that the rat may be a useful model for defining mucosal responses that could be expected in humans. Under controlled infection conditions, such a model could prove to be helpful for unraveling relationships between the host response and oral biofilm development.