Location
Philadelphia, PA
Start Date
1-5-2024 1:00 PM
End Date
1-5-2024 4:00 PM
Description
Coxiella burnetii is an obligate intracellular bacterium that typically infects livestock. In humans, inhalation of Coxiella results in Q fever presented as atypical pneumonia, which may relapse after a prolonged latent period, leading to potentially fatal endocarditis. Our goal is to determine the mechanisms Coxiella employs to survive long-term in the host. While the bacterium initially infects alveolar macrophages, in endocarditis patients, Coxiella is found in foamy macrophages that are rich in neutral lipid storage organelles called lipid droplets (LDs). Our previous studies show that Coxiella manipulates host LD metabolism via the Type 4 Secretion System (T4SS), a major virulence factor that secretes bacterial effector proteins into the host cell cytoplasm to manipulate cellular processes. Additionally, blocking LD breakdown almost completely inhibits bacterial growth, suggesting that LD-derived lipids are critical for Coxiella’s intracellular survival. LD breakdown releases arachidonic acids, precursors for the lipid immune mediator prostaglandin E2 (PGE2), which promotes an immunosuppressive environment within alveolar macrophages. We hypothesize that Coxiella manipulates host cell LD metabolism to create a PGE2-mediated immunosuppressive environment and promote long-term survival in the host. To test this, we quantified PGE2 production during infection with and without LD breakdown inhibitor, atglistatin. ELISA at 24 and 48 hours post-infection showed an LD breakdown-dependent significant increase in PGE2 levels. Fluorescence microscopy revealed that blocking PGE2 production using FDA-approved COX-2 inhibitors significantly decreased Coxiella intracellular growth, which was rescued with the addition of exogenous PGE2. Similarly, direct inhibition of PGE2 with mPGES-1 inhibitor reduced Coxiella intracellular growth. Decreased PGE2 protein levels observed in COX-2 and mPGES-1 inhibitor-treated cells indicate that Coxiella intracellular growth is PGE2-dependent. Collectively, our studies show that LD-dependent PGE2 production promotes Coxiella survival in macrophages. Ongoing studies are identifying the contribution of LDs and PGE2 to immunosuppression during Coxiella infection.
Embargo Period
12-13-2024
Role of lipid droplets and prostaglandinE2 in Coxiella burnetii intracellular growth
Philadelphia, PA
Coxiella burnetii is an obligate intracellular bacterium that typically infects livestock. In humans, inhalation of Coxiella results in Q fever presented as atypical pneumonia, which may relapse after a prolonged latent period, leading to potentially fatal endocarditis. Our goal is to determine the mechanisms Coxiella employs to survive long-term in the host. While the bacterium initially infects alveolar macrophages, in endocarditis patients, Coxiella is found in foamy macrophages that are rich in neutral lipid storage organelles called lipid droplets (LDs). Our previous studies show that Coxiella manipulates host LD metabolism via the Type 4 Secretion System (T4SS), a major virulence factor that secretes bacterial effector proteins into the host cell cytoplasm to manipulate cellular processes. Additionally, blocking LD breakdown almost completely inhibits bacterial growth, suggesting that LD-derived lipids are critical for Coxiella’s intracellular survival. LD breakdown releases arachidonic acids, precursors for the lipid immune mediator prostaglandin E2 (PGE2), which promotes an immunosuppressive environment within alveolar macrophages. We hypothesize that Coxiella manipulates host cell LD metabolism to create a PGE2-mediated immunosuppressive environment and promote long-term survival in the host. To test this, we quantified PGE2 production during infection with and without LD breakdown inhibitor, atglistatin. ELISA at 24 and 48 hours post-infection showed an LD breakdown-dependent significant increase in PGE2 levels. Fluorescence microscopy revealed that blocking PGE2 production using FDA-approved COX-2 inhibitors significantly decreased Coxiella intracellular growth, which was rescued with the addition of exogenous PGE2. Similarly, direct inhibition of PGE2 with mPGES-1 inhibitor reduced Coxiella intracellular growth. Decreased PGE2 protein levels observed in COX-2 and mPGES-1 inhibitor-treated cells indicate that Coxiella intracellular growth is PGE2-dependent. Collectively, our studies show that LD-dependent PGE2 production promotes Coxiella survival in macrophages. Ongoing studies are identifying the contribution of LDs and PGE2 to immunosuppression during Coxiella infection.
Comments
Presented by Nell Guarino.