Background: Observational studies show increasing evidence for role of respiratory microbiota; both bacteria and virus in respiratory infections emphasizing the importance of in vitro model systems to test the role of imbalanced microbiota towards disease symptom exacerbations.
Aim Development of an in-vitro model system to assess the effect of upper respiratory tract multispecies microbial communities comprising of commensals, potential pathogens and virus on human respiratory epithelium.
Methods: Microbial communities for “Healthy” and “Diseased” state were represented by commensal bacteria of Staphylococcus epidermidis & Corynebacterium spp (C. amycolatum, C. accolens, C. pseudodiptheriticum and C. propinquum) and potential pathogens Staphylococcus aureus & Haemophilus influenzea respectively. The microbial communities (single bacteria and combinations) were co-cultured with differentiated human respiratory epithelial cells (Calu-3) and this co-culture model was then used to assess differences in host response on exposure to either “healthy” / “disease” associated microbiota or their mixture. In addition, Human rhinovirus (HRV) and TNF alpha were added to the above-mentioned co-culture model to study host’s response to viral infection and inflammation stimulation respectively.
Results: Successful co-culture of bacteria (single and combination) with Calu-3 cells for up to 72 hrs without any cytotoxic effect (LDH assay) and barrier integrity impairment was achieved. Significantly reduced/increased levels of IL-6 and IL-8 were observed by commensals and pathogens respectively.
TNF alpha stimulation of the established co-culture of Cau-3 cells and microbial communities resulted in increased cytokine production of IL-6 by 3-4 folds and IL-8 by 2 folds in addition to impaired barrier integrity of epithelial cells after 24 and 48 hours of treatment.
Infection of microbial communities and epithelial cells co-culture with HRV resulted in significantly increased IL-6 by 3-4 folds and IL-8 by 2 folds along with impaired barrier integrity of epithelial cells after 24 and 48 hours of treatment.
Changes in the microbial composition resulting from different treatments and viral counts in the presence of different bacteria (single/combination) were also assessed.