Characterization and Analysis of The Nasal Microbiota and Plasmatic Extracellular Vesicles in Allergic Rhinitis: A Case-Control Study

Abstract

Background: Increasing evidence suggests a possible link between the bacterial nasal microbiota (bNM) to allergic diseases such as allergic Rhinitis (AR), as it might modulate the allergic response by acting on the onset and progression of allergic inflammation. In this case-control study, we aimed to compare the bNM between 25 AR patients and 25 matched healthy subjects (HS) as well as to evaluate possible modifications within the host-microbiota cross-talk, investigating the release pattern of both bacterial- and host-Extracellular Vesicles (EVs).Results: bNM analysis showed that Actinobacteria (AR: 2.5%-83.5%; HS: 18.6%-92.7%), Firmicutes (AR: 6.1%-63.5%; HS: 6.4%-72.2%) and Proteobacteria (AR: 0.6%-89.6%; HS 0.7%-38%) were the most abundant phyla in the study population. Diversity reduction in AR patient bNM was pointed out compared to the HS group bNM (Observed OTUs: p =0.018; PD whole tree: p =0.014). Moreover, the distribution of the weighted normalized intra-group UniFrac distances analysis showed a less uniform bacterial community within AR patients rather than HS group (nonparametric test p =0.01). Since EVs may have a central role in the cross-talk between bNM and the host, we evaluated their size and concentration in the plasma of the study subjects. AR patients were characterized by a higher concentration of EVs ranging between 130-231 nm, 257-287 nm and 323-348 nm (p <0.05). We further characterized plasmatic EVs investigating both bacterial-EVs and host-EVs subpopulations and observed that all EV subtypes mean concentrations were higher in AR patients compared to those of HS group, except for EpCAM+ EVs.Conclusion: Our results suggest that AR patients are characterized by a less diverse and wide intra-group variable bNM compared to that of HS, as well as an altered host-microbiota EV communication network. Further studies are needed to disentangle the relationship between the host and the nasal bacterial community during pathological conditions and health.