Host-Pathogen Interactions in a Cystic Fibrosis Polymicrobial Infection Model

ABSTRACT
Cystic fibrosis (CF) is characterized by the formation of thick mucus in the lung leading to chronic
infection of various pathogens that are prone to developing antibiotic tolerance. Despite effective
modulator therapy (HEMT) that improves lung function and many clinical outcomes, HEMT does
not eliminate chronic, antibiotic-tolerant lung infections, the major cause of morbidity and mortality
in CF. Although most people with CF (pwCF) have multispecies lung infections, almost all
published studies focus on single-species infection models. Thus, polymicrobial-host interactions
in CF are not completely understood, especially under physiologically relevant conditions such as
anoxia typical of mucus plugs.
The overarching goal of our work is to use in vitro models to gain insight into how polymicrobial
infections develop in pwCF. Bacterial pathogens have been shown to secrete membrane vesicles
(bEVs) that diffuse through the CF mucus to deliver virulence factors such as DNA, RNA, and
proteins to their targets. As recent studies have shown that the first exposure to bacterial products
alters DNA methylation and gene silencing that affect subsequent exposures, our hypothesis is
that pwCF develop chronic infections in part due to epigenetic changes caused by preexposure
to CF pathogens that reduce the HBEC immune response to infection over time. This application
aims to characterize the effects of an in vitro model of CF polymicrobial infection on human
bronchial epithelial cells (HBEC) with preexposure to bEVs secreted by the common CF pathogen
Staphylococcus aureus. The polymicrobial culture contains four prevalent and abundant CF
pathogens: Pseudomonas aeruginosa, S. aureus, Streptococcus sanguinis, and Prevotella
melanogenica. Using transcriptomic and proteomic analysis, cytokine analysis, ATAC-Seq, and
DNA methylation analysis, this study aims to elucidate the host HBEC response to treatment with
bEVs. This study will contribute to our understanding of host-pathogen interactions in the CF lung
and potentially identify novel therapeutic targets during infection.
This project will provide the applicant with a broad range of both bioinformatic and lab techniques
that will provide a strong foundation for her long-term goal of becoming an academic researcher.

Grant Number: 5F31HL172440-02
NIH Institute/Center: NIH
Principal Investigator: Lily Charpentier