Differences in local immune cell landscape between Q fever and atherosclerotic abdominal aortic aneurysms identified by multiplex immunohistochemistry.

BACKGROUND

Chronic Q fever is a zoonosis caused by the bacterium which can manifest as infection of an abdominal aortic aneurysm (AAA). Antibiotic therapy often fails, resulting in severe morbidity and high mortality. Whereas previous studies have focused on inflammatory processes in blood, the aim of this study was to investigate local inflammation in aortic tissue.

METHODS

Multiplex immunohistochemistry was used to investigate local inflammation in Q fever AAAs compared to atherosclerotic AAAs in aorta tissue specimen. Two six-plex panels were used to study both the innate and adaptive immune systems.

RESULTS

Q fever AAAs and atherosclerotic AAAs contained similar numbers of CD68 macrophages and CD3 T cells. However, in Q fever AAAs, the number of CD68CD206 M2 macrophages was increased, while expression of GM-CSF was decreased compared to atherosclerotic AAAs. Furthermore, Q fever AAAs showed an increase in both the number of CD8 cytotoxic T cells and CD3CD8FoxP3 regulatory T cells. Finally, Q fever AAAs did not contain any well-defined granulomas.

CONCLUSIONS

These findings demonstrate that despite the presence of pro-inflammatory effector cells, persistent local infection with is associated with an immune-suppressed microenvironment.

FUNDING

This work was supported by SCAN consortium: European Research Area - CardioVascualar Diseases (ERA-CVD) grant [JTC2017-044] and TTW-NWO open technology grant [STW-14716].