Bacterial Small RNAs in Bronchiolitis

Bronchiolitis is a lower respiratory infection caused by many viruses, including respiratory syncytial virus (RSV) and rhinovirus (RV). It is the leading cause of U.S. infant hospitalization, and having been hospitalized for bronchiolitis (severe bronchiolitis) is a risk factor for later developing asthma. Severity, immune responses, and risk for asthma development have been shown to vary greatly among severe bronchiolitis patients without clear explanation. Additionally, there is variability in the dominance of several bacterial species of the lung microbiome correlating with severity and viral etiology, adding to this heterogeneity. We sought to identify how four bacterial species affect bronchiolitis heterogeneity by examining bacterial small RNAs (sRNAs), regulatory RNAs that are carried to other cells by extracellular vesicles (EVs) as a means of intracellular, and potentially interkingdom, communication. We devised two techniques: a method to isolate species-specific bacterial EVs from human samples, and another to isolate EVs from pure bacterial culture. From four species, we identified over 1,000 novel sRNAs carried within bacterial EVs. Several sRNAs of each species were in higher abundance in either the bacterial cell or EV, supporting EVs as intentional communicative vessels. Next, we determined that the majority (58-87%) of the bacterial sRNAs identified in this study were present within nasal swab samples of infants with RSV- and RV-only bronchiolitis. Very few bacterial sRNAs were associated with bronchiolitis severity and other characteristics, suggesting bacterial sRNAs are not driving the differences seen in these characteristics. However, 30 sRNAs were differentially expressed between RSV- and RV-only bronchiolitis. We computationally identified the human targets of the sRNAs and predicted their function. sRNAs associated with RSV-only bronchiolitis were predicted to inhibit IL-17A signaling, while RV-only bronchiolitis-associated sRNAs were predicted to inhibit several cytokine and cytoskeleton signaling pathways. Finally, we aimed to identify the effects of bacterial EVs isolated from pure culture on airway epithelial cell cytokine production during an induced viral infection, but cell culture experiments were inconclusive. These bacterial sRNA-human mRNAs interactions need to be validated in vitro and investigated further, but suggest that bacterial sRNAs impact immune response differences between RSV- and RV-only bronchiolitis.

Author

• Krohmaly, Kylie Isabelle

Language

• English

Date created

• 2024

Type of Work

• Dissertation

License

• All rights reserved

Rights statement

• In Copyright

GW Unit

• Microbiology & Immunology

Degree

• Ph.D.

Advisor

• Freishtat, Robert J

Committee Member(s)

• Preciado, Diego
• Bosque, Alberto
• Leitenberg, David

Persistent URL

•  https://scholarspace.library.gwu.edu/etd/ks65hd08r