Location
Philadelphia, PA
Start Date
17-4-2026 1:30 PM
End Date
17-4-2026 2:30 PM
Description
Introduction: Coxiella burnetii is a Gram-negative, obligate intracellular bacterium that spreads to humans via inhalation, and can cause a severe disease called ‘Q Fever’. Clinical presentations of Q Fever include fever, hepatitis, pneumonia, and endocarditis. Upon entering human lungs, Coxiella, infects the alveolar macrophages and resides intracellularly in a Coxiella-containing vacuole (CCV). Coxiella utilizes its type 4 secretion system (T4SS) to release effector proteins into the host cell cytoplasm and manipulates several host cell processes including lipid metabolism. Particularly, Coxiella alters the metabolism of the lipid storage organelles, lipid droplets (LDs). Breakdown of host LDs leads to the production of arachidonic acid, a precursor of lipid immune mediators prostaglandin E2 (PGE2) and leukotriene B4 (LTB4). Our lab has shown a LD breakdown-dependent increase in PGE2 production in Coxiella-infected alveolar macrophages, and we aim to see if there is an increase in other immune mediators derived from arachidonic acid.
Objective: Our objective is to measure levels of LTB4 in Coxiella-infected alveolar macrophages to observe if the established relationship between Coxiella and PGE2 extends to other products of the arachidonic acid pathway.
Methods: Mouse alveolar macrophages were infected with wild-type (WT) Coxiella and a T4SS-mutant to identify changes in the absence of Coxiella virulence. Coxiella-infected and uninfected alveolar macrophages were treated with a LD breakdown inhibitor, atglistatin, allowing us to investigate the specific role of LDs. ELISA was performed to measure PGE2 and LTB4 levels Additionally, quantitative Real Time PCR was performed to measure ALOX5, a gene that codes for the LTB4 synthesis enzyme, lipooxygenase.
Results: Preliminary ELISA does not show a statistically significant increase in LTB4 in Coxiella-infected cells compared to uninfected controls. Additionally, blocking LD breakdown with an ATGL inhibitor does not change LTB4 levels. However, PCR has shown an increase in ALOX5 gene levels in Coxiella-infected cells compared to uninfected cells, suggesting an association with LTB4. More ELISA data is currently being collected to further investigate this connection.
Conclusion: Although our lab has previously observed a LD breakdown-dependent increase in PGE2 in Coxiella-infected cells compared to uninfected cells, we have not observed any changes to LTB4 production. Increase in ALOX5 gene expression in WT Coxiella-infected alveolar macrophages suggests an increase in the LTB4 pathway at the transcriptional level. This indicates that LD breakdown may increase LTB4 levels in Coxiella-infected cells. While early ELISA data is still inconclusive, we hope that with further data collection, we will see a more clear relationship.
Embargo Period
6-2-2028
Mammalian lipid droplet breakdown-dependent immune mediator production in Coxiella-infected cells
Philadelphia, PA
Introduction: Coxiella burnetii is a Gram-negative, obligate intracellular bacterium that spreads to humans via inhalation, and can cause a severe disease called ‘Q Fever’. Clinical presentations of Q Fever include fever, hepatitis, pneumonia, and endocarditis. Upon entering human lungs, Coxiella, infects the alveolar macrophages and resides intracellularly in a Coxiella-containing vacuole (CCV). Coxiella utilizes its type 4 secretion system (T4SS) to release effector proteins into the host cell cytoplasm and manipulates several host cell processes including lipid metabolism. Particularly, Coxiella alters the metabolism of the lipid storage organelles, lipid droplets (LDs). Breakdown of host LDs leads to the production of arachidonic acid, a precursor of lipid immune mediators prostaglandin E2 (PGE2) and leukotriene B4 (LTB4). Our lab has shown a LD breakdown-dependent increase in PGE2 production in Coxiella-infected alveolar macrophages, and we aim to see if there is an increase in other immune mediators derived from arachidonic acid.
Objective: Our objective is to measure levels of LTB4 in Coxiella-infected alveolar macrophages to observe if the established relationship between Coxiella and PGE2 extends to other products of the arachidonic acid pathway.
Methods: Mouse alveolar macrophages were infected with wild-type (WT) Coxiella and a T4SS-mutant to identify changes in the absence of Coxiella virulence. Coxiella-infected and uninfected alveolar macrophages were treated with a LD breakdown inhibitor, atglistatin, allowing us to investigate the specific role of LDs. ELISA was performed to measure PGE2 and LTB4 levels Additionally, quantitative Real Time PCR was performed to measure ALOX5, a gene that codes for the LTB4 synthesis enzyme, lipooxygenase.
Results: Preliminary ELISA does not show a statistically significant increase in LTB4 in Coxiella-infected cells compared to uninfected controls. Additionally, blocking LD breakdown with an ATGL inhibitor does not change LTB4 levels. However, PCR has shown an increase in ALOX5 gene levels in Coxiella-infected cells compared to uninfected cells, suggesting an association with LTB4. More ELISA data is currently being collected to further investigate this connection.
Conclusion: Although our lab has previously observed a LD breakdown-dependent increase in PGE2 in Coxiella-infected cells compared to uninfected cells, we have not observed any changes to LTB4 production. Increase in ALOX5 gene expression in WT Coxiella-infected alveolar macrophages suggests an increase in the LTB4 pathway at the transcriptional level. This indicates that LD breakdown may increase LTB4 levels in Coxiella-infected cells. While early ELISA data is still inconclusive, we hope that with further data collection, we will see a more clear relationship.