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The bacterial lung tissue microbiome in the pathogenesis of chronic obstructive pulmonary disease

University of British Columbia

Rationale: Several laboratories have shown that the decline in lung function in Chronic Obstructive Pulmonary Disease (COPD) is associated with increased formation of tertiary lymphoid follicles. This provides direct histological evidence in support of the hypothesis that the decline in lung function is associated with activation of an adaptive immune response. The antigens responsible for driving this immune activation remain poorly understood. The recent realization that the human lung contains a bacterial microbiome that changes in association with the presence of COPD suggests the hypothesis that bacteria arising from within this microbiome might be responsible for activating the adaptive immune response in COPD. Approach: The research described in this thesis examines the lung tissue bacterial microbiome from patients with mild to moderate COPD as well as patients with very severe COPD. The bacterial microbiome from these studies utilized either nested or touchdown PCR followed by 454™ pyrotag sequencing of specific variable regions on the 16S rRNA gene. Changes in the microbiome were examined in relation to histological estimates of emphysematous destruction of the lung and inflammatory immune cell infiltration associated with this tissue remodeling process. Finally, Haemophilus influenzae, a bacterium identified from this microbiome, known to cause inflammation was compared to the host tissue repair process. Results: The different bacterial community was present in control and mild (GOLD 1) compared to moderate (GOLD 2) COPD. The community composition was also different between donor lung tissue and very severe (GOLD 4) COPD. Further, the analysis identified a list of 10 OTUs that discriminated between lung tissue affected by GOLD 4 COPD and controls. In addition, the data presented here indicate that the host immune response to these organisms precedes the structural changes associated with COPD. Conclusion: Collectively, these data confirm that there is a small but diverse microbiome in the normal human lung that becomes less diverse in COPD. Furthermore, the disappearance/appearance of certain OTUs can discriminate between control and COPD affected lung tissue and that some of these OTUs are associated with the inflammatory immune cell infiltration and tissue destruction that occurs in COPD.

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2015-08-19

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/54530

Experimental Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/