BACKGROUND: Genetic factors significantly influence caries development and the colonization of oral bacteria, which could explain why some individuals are more prone or resistant to caries. Human leukocyte antigen (HLA) class II is a component in the adaptive immune system that has been associated with the colonization of oral bacteria such as Streptococcus mutans. This study aimed to investigate the association between specific alleles and genotypes of HLA-DRB1 on subgroup level and the colonization of S. mutans in a group of Swedish children.

METHODS: Blood samples from 357 children were analyzed for HLA using next generation sequencing. Saliva samples were collected and analyzed for S. mutans, after which the subjects were divided into three groups: low, moderate, and high levels of colony forming units (CFU). The frequency of DRB1 alleles and genotypes was compared between the three groups. In addition, colonization levels, including the extremely high and low S. mutans CFU in individuals with alleles DRB1*0401, *0404, and *0301 were compared to the rest of the material.

RESULTS: Individuals with DRB1*0401 were significantly associated with the extremely high CFU levels, since CFU levels > 100 were observed in 4.3% of individuals with DRB1*0401, compared to none among those without the allele (p = 0.009, Fisher's exact test). No statistical association was noted between the low, moderate, and high S. mutans groups and specific alleles or genotypes.

CONCLUSIONS: The findings suggest a potential relation between HLA class II alleles and the colonization of S. mutans. Specifically, carrying the DRB1*0401 allele may be a predisposing factor for higher levels of colonization.