Colonization of dermal arterioles by Neisseria meningitidis provides a safe haven from neutrophils

Neisseria meningitidis, a human-specific bacterium, is responsible for meningitis and fatal fulminant systemic disease. Bacteria colonize blood vessels, rapidly causing devastating vascular damage despite a neutrophil-rich inflammatory infiltrate. How this pathogen escapes the neutrophil response is unknown. Using a humanized mouse model, we show that vascular colonization leads to the recruitment of neutrophils, partially reducing bacterial burden and vascular damage. This partial effect is due to the ability of bacteria to indiscriminately colonize capillaries, venules and arterioles, as observed in human samples. In venules, potent neutrophil recruitment allows efficient bacterial phagocytosis. In contrast, in infected capillaries and arterioles adhesion molecules such as E-Selectin are not expressed on the endothelium and intravascular neutrophil recruitment is minimal. These results show that colonization of capillaries and arterioles by N. meningitidis create an intravascular niche that preclude the action of neutrophils, resulting in immune escape and subsequent fulminant progression of the infection.