Date on Master's Thesis/Doctoral Dissertation

5-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Microbiology and Immunology

Degree Program

Microbiology and Immunology, PhD

Committee Chair

Lawrenz, Matthew

Committee Co-Chair (if applicable)

Uriarte, Silvia

Committee Member

Uriarte, Silvia

Committee Member

Abu Kwaik, Yousef

Committee Member

Ceresa, Brian

Committee Member

Warawa, Jonathan

Author's Keywords

macrophage; neutrophil; host-pathogen; bacteria; effector; LTB4

Abstract

Yersinia pestis has gained widespread infamy due to the historic outbreak during the middle ages, referred to as The Black Death. Infection with Y. pestis typically begins with deposition of Y. pestis into the dermis (bubonic plague) or respiratory tract (pneumonic plague). Tissue resident macrophages are the first innate immune cell encountered by Y. pestis. Macrophages are likely a way for Y. pestis to avoid neutrophils early in infection when the neutrophil neutralizing Type Three Secretion System is not expressed. This work focuses on which Rab host proteins are manipulated by Y. pestis, and how neutrophils are forced to remain silent when all alarms and the arsenal they possess should be triggered. Through an RNAi screen 8 Rab proteins were found to be important for intracellular Y. pestis survival. The Rab proteins were prioritized based on the impact gene knockdown had on Y. pestis intracellular survival. Overexpressed Rab2b and Rab20 co-localized to the YCV, while overexpressed Rab13 did not. Indicating Rab13 may regulate Y. pestis intracellular survival in a contact independent manner. Survival within macrophages likely provides Y. pestis time to express the type three secretion system. Using deletion and addition mutants, I found that Y. pestis uses the type three secretion system effectors, YopE, YopH, YopJ, and YpkA to inhibit neutrophil degranulation, in addition to inhibiting LTB4 production in human neutrophils also by YopT. Unlike human neutrophils, LTB4 is not produced in response to Y. pestis in mouse neutrophils or macrophages and the zinc binding protein, calprotectin is released in vivo, but not by human neutrophils. Together, the Rab data and neutrophil exocytic responses contribute to our understanding of how Y. pestis manipulates host phagocytic cells to create a permissive environment in which to survive and replicate.

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