Associations Between S-IgA, Streptococcus mutans Colonization and Caries in Infants

Objective: The relationship between Streptococcus mutans infection and the development of salivary IgA responses may impact dental caries activity. The purpose of this longitudinal study was to evaluate the development of salivary IgA responses in high caries risk infants in relation to S. mutans colonization and dental caries. Method: Saliva was collected every 6 months over a 2-year period from infants (average age at enrollment 12 months) in a Black Belt community in Alabama, where access to a dentist is limited. Whole saliva was collected using cotton swabs. The swabs were centrifuged, and saliva collected and stored at -70ºC until analyzed by ELISA for total and S. mutans specific IgA levels. Decayed, missing, filled surfaces (dmfs) of primary teeth were recorded at baseline, 12 and 24 month visits. Dental plaque, saliva and tongue samples were collected and assessed for S. mutans levels using selective media and standard plating methods. Result: Among the 84 6-18 month old infants enrolled, mean IgA was 196 µg/ml (median=129µg/ml) and mean specific anti-S. mutans activity was 0.222 µg/ml (median=0.117µg/ml). Generally, total and specific IgA antibody activity increased with age.  Infants that developed caries (dmfs>0) during the 24 months (32/77) had higher anti-S. mutans activity after 12 months. Subjects colonized with S. mutans had a similar association with anti-S. mutans activity.  Conclusion: This study found that IgA development in infants increased with S. mutans colonization and the development of dental caries. Further longitudinal analyses will be needed to evaluate how mucosal immune responses are associated with caries incidence, and especially, how immune responses during the primary dentition are associated with caries incidence when permanent teeth erupt.