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Host-Pathogen Dynamics: The Role of Extracellular Vesicles and Neutrophil Extracellular Traps in Pneumocystis Pneumonia

Sayson, Steven Earl
http://orcid.org/0000-0002-7461-0704
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712918114090523

Abstract Details

2024, PhD, University of Cincinnati, Medicine: Pathobiology and Molecular Medicine.
Pneumocystis jirovecii pneumonia (PjP) poses a considerable clinical challenge, especially in immunocompromised individuals due to conditions like HIV/AIDS, organ transplantation, and immune-compromising malignancies. Clinical manifestations of PjP range from dyspnea to life-threatening respiratory failure. A significant obstacle is the absence of a facultative culture system for Pneumocystis spp., limiting research on its metabolism, pathogenesis, and therapeutic strategies. Pneumocystis spp. primarily rely on their mammalian hosts for essential nutrients, necessitating in vivo infection models. Each species infects a specific mammalian host, whereas P. jirovecii (Pj) is the species affecting humans, and P. murina (Pm) and P. carinii (Pc) serve as surrogate mouse or rat models for PjP. Extracellular vesicles (EVs) have long been observed in the alveolar lumen in both uninfected and P. carinii-infected rat lungs. We hypothesized that Pc obtains nutrients through host EVs to supplement its metabolic needs. Our research demonstrates active EV uptake by Pc, suggesting their potential role in nutrient acquisition. However, bronchial alveolar lavage fluid (BALF) EVs from Pc-infected rats exhibited toxic effects on Pc viability in vitro, revealing complex host-pathogen interactions. We identified evidence suggesting that Pc and Pm secrete EVs, including electron-dense cell wall-containing EVs and the EV proteome containing of major surface glycoproteins, which are a Pneumocystis-specific superfamily of membrane proteins. While the Pneumocystis EV proteome shows homology to other fungal EV proteomes, further research is required to comprehensively identify the proteome. The precise functions of these EVs remain uncertain but may function in supportive roles EVs play in other fungal organisms. This includes contributing to proper biofilm formation, as observed in Candida albicans and Pichia fermentans. BALF EVs from Pc-infected rats and Pm-infected mice showed an enrichment of proteins involved in NETosis. RNA sequencing of Pm-infected mouse lungs revealed increased expression of NLRP3 inflammasome- and NETosis-related genes, suggesting a potential link to excessive inflammation and lung injury. This led us to hypothesize that neutrophils construct NLRP3 inflammasomes, undergo NETosis, and secrete neutrophil extracellular traps (NETs) during Pm pneumonia. Elevated neutrophil elastase (NE) and myeloperoxidase (MPO) and immunofluorescence staining of NETs in the lungs of the Pm-infected mice validated our findings. To show the specific involvement of neutrophils, isolated Ly-6G+ neutrophils were stimulated with Pm and showed increased NET secretion, as detected by DNA-MPO complex ELISA. However, these NETs did not affect Pm viability in vitro. Our research is the first investigation into EV dynamics during Pneumocystis pneumonia, indicating that BALF EVs from infected rats exert detrimental effects on Pc growth. Furthermore, we showed active EV uptake by Pc, which may be potentially used as a nutrient acquisition mechanism. Our findings also showed neutrophil responses to Pm lead to NLRP3 inflammasome formation and NET secretion, which can lead to the excessive inflammation and lung injury. This work lays the groundwork for in-depth studies on host-pathogen EV responses and neutrophil immune responses during Pneumocystis pneumonia.
Melanie Cushion, Ph.D. (Committee Chair)
David Askew, Ph.D. (Committee Member)
George Smulian, M.D. (Committee Member)
Scott Langevin, Ph.D. (Committee Member)
Michael Borchers, Ph.D. (Committee Member)
105 p.
Microbiology
Pneumocystis pneumonia; infectious diseases; fungi; Exosomes; Extacellular vesicles

Recommended Citations

Citations

  • Sayson, S. E. (2024). Host-Pathogen Dynamics: The Role of Extracellular Vesicles and Neutrophil Extracellular Traps in Pneumocystis Pneumonia [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712918114090523

    APA Style (7th edition)

  • Sayson, Steven Earl. Host-Pathogen Dynamics: The Role of Extracellular Vesicles and Neutrophil Extracellular Traps in Pneumocystis Pneumonia. 2024. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712918114090523.

    MLA Style (8th edition)

  • Sayson, Steven Earl. "Host-Pathogen Dynamics: The Role of Extracellular Vesicles and Neutrophil Extracellular Traps in Pneumocystis Pneumonia." Doctoral dissertation, University of Cincinnati, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712918114090523

    Chicago Manual of Style (17th edition)

ucin1712918114090523
105
© 2024, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.
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