Adhesion of Neisseria meningitidis to Dermal Vessels Leads to Local Vascular Damage and Purpura in a Humanized Mouse Model

Abstract

Septic shock caused by Neisseria meningitidis is typically rapidly evolving and often fatal despite antibiotic therapy. Further understanding of the mechanisms underlying the disease is necessary to reduce fatality rates. Postmortem samples from the characteristic purpuric rashes of the infection show bacterial aggregates in close association with microvessel endothelium but the species specificity of N. meningitidis has previously hindered the development of an in vivo model to study the role of adhesion on disease progression. Here we introduced human dermal microvessels into SCID/Beige mice by xenografting human skin. Bacteria injected intravenously exclusively associated with the human vessel endothelium in the skin graft. Infection was accompanied by a potent inflammatory response with the secretion of human inflammatory cytokines and recruitment of inflammatory cells. Importantly, infection also led to local vascular damage with hemostasis, thrombosis, vascular leakage and finally purpura in the grafted skin, replicating the clinical presentation for the first time in an animal model. The adhesive properties of the type IV pili of N. meningitidis were found to be the main mediator of association with the dermal microvessels in vivo. Bacterial mutants with altered type IV pili function also did not trigger inflammation or lead to vascular damage. This work demonstrates that local type IV pili mediated adhesion of N. meningitidis to the vascular wall, as opposed to circulating bacteria, determines vascular dysfunction in meningococcemia.

Host Specificity of Bacterial Pathogens

“…Although studies of infection in humanized mice have only recently begun, this approach promises to provide unprecedented insights into mechanisms of host interaction with human pathogens including hepatitis viruses, HIV, CMV, EpsteinBarr virus, dengue virus, N. meningitidis, and Plasmodium falciparum (e.g., Bente 2005;Jimé-nez-Díaz 2009;Smith et al 2010;Berges and Rowan 2011;Sato et al 2011;Zeisel et al 2011;Melican et al 2013).…”

Humanized Mouse Model to Study Bacterial Infections Targeting the Microvasculature

“…The strain had been engineered to express green fluorescent protein (GFP) from a chromosomal insertion 18 . Bacterial colony forming unit counts are established by counting the number of colonies on the agar plates and calculating either CFU/ml of blood or CFU/mg of tissue from the known volumes plated.…”

“…Human vessels were stained using a marker for human endothelium, either CD31 (PECAM-1) or the lectin Ulex europaeus agglutinin (UEA) 18,22 . The UEA was conjugated to rhodamine allowing one-step staining (Figures 2A-C).…”

“…In this protocol, we describe a humanized mouse model in which human skin, including the dermal microvasculature, is transplanted onto immunocompromised mice 18,19 . This results in functional human vessels, perfused with the mouse circulation.…”

CD147 est un récepteur essentiel à la colonisation vasculaire par le méningocoque

“…Enfin, des souches de méningocoque appartenant à des séro-groupes distincts exprimaient ce même phénotype d'adhérence dépendante de CD147, suggérant que le rôle de CD147 dans l'adhérence du méningocoque aux cellules endothéliales était conservé pour les souches pathogènes de ménin-gocoque génétiquement différentes. Dans ce modèle, les vaisseaux du greffon humain s'anastomosent au réseau sanguin de la souris, permettant l'irrigation des vaisseaux humains par la circulation sanguine de la souris hôte [10,11]. Du fait de la stricte spécificité du méningo-coque pour l'homme, l'injection par voie parentérale de méningocoques chez la souris conduit à la colonisation sélective des vaisseaux humains du greffon, et à l'apparition consécutive de lésions cutanées similaires à celles qui sont observées chez l'homme ( Figure 1B).…”