Determination of Rickettsial Viability and Characterization of Macrophage Death in Cultures of Gamma-Interferon-Treated Macrophages Infected with Rickettsia prowazekii
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Authors
Vernon, Kathryn Huitt
Issue Date
2013-01-08
Type
Thesis
Language
en_US
Keywords
Rickettsia prowazekii , Macrophage , IFN-y , RAW264.7 cells , polyethylene glycol , PEGs , Osmotic lysis
Alternative Title
Abstract
Rickettsia prowazekii is an obligate intracellular, Gram-negative bacterium that is
transmitted via body lice and is the causative agent of epidemic typhus. During an
R. prowazekii infection, the bacteria target the endothelial cells lining small blood vessels, as well as macrophages. When cultured macrophage-like cells are pre-treated with gamma interferon (IFN-y) and then infected with R. prowazekii, the macrophages die
within a few hours (Turco & Winkler, 1984; Turco & Winkler, 1994). It is unknown if
the rickettsiae are killed as the macrophages die and the mechanism of cell death seen in IFN-y-treated, infected RAW264.7 cells has yet to be characterized. The research
presented here had two objectives: to determine if the rickettsiae are viable after infection
and death of IFN--pre-treated, macrophage-like RAW264.7 cells and to determine if the
osmotic lysis inhibitor polyethylene glycol (PEG) has the ability to decrease cell death in
RAW264.7 cells treated with IFN-y. Rickettsial viability was assessed by determining
the ability of the bacteria to grow in untreated Vero cells after their release from dead
IFN--treated, infected RAW264.7 cells. The rickettsiae released from the dead
IFN--treated RAW264.7 cells were able to grow in Vero cells over 49 hours, indicating
that they are viable after the death of their host cells. Sufficiently large PEGs can inhibit
osmotic lysis, which contributes to macrophage death during oncosis and/or
caspase-1- dependent pyroptosis. At 30 mM, PEGs > 2,000 daltons (nominal average
molecular weight) have a protective effect against cell death in IFN-y-treated, infected
RAW264.7 cells, while PEGs < 1,450 daltons do not have an effect on RAW264.7 cell
death.
Description
The thesis, "Determination of Rickettsial Viability and Characterization of Macrophage Death in Cultures of Gamma Interferon-Treated Macrophages Infected with Rickettsia prowazekii," by Kathryn Huitt Vernon. Embargo lifted 12/4/2015.