Rationale: Dysbiosis of microbial communities colonizing the human airway has been described for a variety of chronic diseases and characterization of human microbiome in states of health and disease is challenging for understanding the role of microbiome. Our goal of this study is to determine the microbiome composition at mucus using culture-dependent or -independent methods and to provide the profile of microbiome-related antiviral immune response.
Material and Methods: To account for the qualitative and quantitative diversity of commensal bacteria, nasal mucus were obtained from 17 healthy individuals using cotton mucosal swab. GS-FLX 454 pyrosequencing by using 16S rRNA gene amplification was performed and the data were assessed using high-throughput next-generation sequencing analysis. Bacterial isolation was done through culture-based analysis to infect cultured nasal epithelial cells (NEC).
Results: While Firmicutes was not prevalent at healthy nasal mucus but staphylococcus was the most abundant genus which was existed. A few species accounted for the majority of the bacteria detected at nasal mucus of healthy subjects: Staphylococcus epidermidis (35.5%), Corynebacterium pseudodiphtheriticum (14.05%) and Enterobacter aerogenes (8.26%). S. epidermidis at human nasal mucosa was separately harvested from bacterial colony at LB plate and we inoculated S. epidermidis to cultured NEC as MOI 0.25. S. epidermidis enhanced IFNs mRNA level and secreted proteins significantly from 8 hr post of infection without any viral stimulation, especially IFN-λ1, λ2/3. Both IFN-α and -β levels were not changed after S. epidermidis infection. The significant elevation of IAV PA genes expression and highest IAV viral titer showed at 2 dpi. Interestingly, the NECs which were infected with IAV and S. epidermidis showed significantly lower IAV mRNA level and viral titer with considerably higher induction of IFN-λ1 and -2/3.
Conclusion: We determined that S. epidermidis is most dominant microbiome at healthy nasal mucus and have a potential to enhance antiviral innate immune response resulting in controlling influenza viral infection through induction of type III IFNs.