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Le dépistage néonatal (DNN) de la mucoviscidose, grâce à une prise en charge multidisciplinaire très précoce des nourrissons, est optimal en termes de pronostic pour les patients. Depuis 20 ans, il a connu une expansion internationale spectaculaire. Les performances du DNN national français réalisé depuis 2002 sont en accord avec les standards européens pour la valeur prédictive positive (0,31 pour un minimum de 0,30) et la spécificité (0,95 pour un minimum de 0,95) ; nous soulignons le nombre très faible de cas non conclus, un pourcentage très élevé de test de la sueur réalisés (95,5 %) et d’identification des mutations (96,6 %), un ratio de cas de mucoviscidose par rapport aux cas de diagnostic incertain de 6,3:1, ainsi qu’une stratégie efficace pour repérer les faux négatifs. Une nouvelle organisation du DNN français vient de se mettre en place, il est capital de maintenir l’efficacité du processus, du nouveau-né en maternité jusqu’au diagnostic dans des centres de référence ou de compétences de la mucoviscidose avec un recueil exhaustif des données et leur validation. Par ailleurs, une proposition de changement d’algorithme introduisant le dosage du polypeptide d’activation pancréatique est soumise aux nouvelles instances du DNN. L’annonce d’un diagnostic positif reste difficile et peu standardisée, si bien qu’une plateforme de simulation est en cours de mise en place. Nous détaillons ici les bonnes pratiques et les difficultés de réalisation du test de la sueur, avec les seuils de chlorures récemment redéfinis, ainsi que les modalités du conseil génétique.

Murine macrophages have been classified as either susceptible or nonsusceptible to killing by anthrax lethal toxin (LT) depending upon genetic background. While considered resistant to LT killing, we found that bone marrow-derived macrophages (BMMs) from DBA/2, AKR, and C57BL/6 mice were slowly killed by apoptosis following LT exposure. LT killing was not restricted to in vitro assays, as splenic macrophages were also depleted in LT-injected C57BL/6 mice. Human macrophages, also considered LT resistant, similarly underwent slow apoptosis in response to LT challenge. In contrast, LT triggered rapid necrosis and a broad protein release in BMMs derived from BALB/c and C3H/HeJ, but not C57BL/6 mice. Released proteins included processed interleukin-18, confirming reports of inflammasome and caspase-1 activation in LT-mediated necrosis in macrophages. Complete inhibition of caspase-1 activity was required to block LT-mediated necrosis. Strikingly, minimal residual caspase-1 activity was sufficient to trigger significant necrosis in LT-treated macrophages, indicating the toxicity of caspase-1 in this process. IL-18 release does not trigger cytolysis, as IL-18 is released late and only from LT-treated macrophages undergoing membrane perturbation. We propose that caspase-1-mediated macrophage necrosis is the source of the cytokine storm and rapid disease progression reported in LT-treated BALB/c mice.

Numerous early events in anthrax lethal toxin (LT)-mediated cell killing have been described, including uptake of LT and MAPKK cleavage. However, critical downstream events in LT killing remain to be identified. In this study we show that LT cause mitochondrial dysfunction in murine J774A.1 macrophages, as indicated by a continuous drop in both mitochondrial membrane potential and SDH activity over 90 min of LT exposure. This was further supported by ultrastructural analysis revealing LT-induced swelling of mitochondria. Mitochondrial impairment and cytolysis were controlled by proteasomes: Proteasome inhibitors restored mitochondrial activity and rescued cells from cytolysis, even when added immediately prior to membrane perturbation, suggesting a link between mitochondrial impairment and cytolysis. The addition of KCl delayed LT-mediated cytolysis, but could not block mitochondrial impairment or rescue cells. KCl treatment precluded events linked to cytolysis, including a precipitous drop in ATP levels and ubiquitinated proteins, revealing that they are epiphenomena in LT killing. This is the first study that indicates mitochondrial targeting by anthrax lethal toxin. We present evidence that mitochondrial dysfunction and membrane perturbation are key events in LT killing, and are controlled by proteasomes and KCl.