Association between microbiome and plasma proteome profile in COPD

<b>Background:</b> COPD is associated with airway inflammation and bacterial colonisation. Whether the airway microbiome is related to systemic protein levels is unknown. <b>Aim:</b> We investigated the relationship between the COPD sputum microbiome and contemporaneous proteome profile. <b>Methods:</b> 31 COPD subjects at stable stage were recruited as part of the COPD-BEAT study. Microbial profile from sputum and proteomic profile from plasma were obtained through 16S rDNA sequencing and mass spectrophotometry respectively. Proteomic profiles were investigated all identified bacterial genera exceeding 1% of the cumulative microbiome with bacterial abundance dichotomised by high and low expression against the median. <b>Results:</b> Altogether 377 proteins were significantly differentially expressed between high and low abundance of the bacterial genera included. Pathway analysis of these proteins revealed that the complement and coagulation cascades pathway was most frequently correlated with specific bacterial genera; notably, <i>Moraxella</i> and <i>Veillonella</i> were, respectively, positively and negatively associated. There was also a reciprocal relationship between the abundances of these genera (r= -0.38; p= 0.03). There was no significant correlation between proteins identified in this pathway and clinical characteristics. <b>Conclusion:</b> The complement and coagulation cascades pathway was up-regulated in response to airway presence of <i>Moraxella</i> genera that night suggest an activation of systemic innate immunity in response to <i>Moraxella</i> rather than impaired systemic immunity driving airway colonisation.