[Two patients with cat scratch disease]. / Twee patiënten met kattenkrabziekte.

BACKGROUND: Cat scratch disease (CSD) is caused by Bartonella henselae infection. CSD is usually characterized by self-limiting regional lymphadenopathy. However, sometimes CSD presents as a disseminated disease with multiple organ involvement. CASE DESCRIPTIONS: We describe two patients with CSD. Patient A, an 18-year old woman, was referred because of fatigue, a subfebrile temperature and axillary lymphadenopathy. Patient B, a 50-year old man, visited the emergency ward with fever, back pain and painful inguinal lymphadenopathy. MRI showed osteitis of vertebrae and hepatic abcesses. In both patients symptoms started after being scratched by a cat and both were tested positive for infection with Bartonella henselae. Patient B was treated with antibiotics. Both patients made a full recovery. CONCLUSION: Recent contact with a cat in a patient with unexplained fever and lymphadenopathy raises the possibility of CSD. Diagnosis can be confirmed by serologic testing, histopathology or PCR. Antimicrobial treatment must be considered in all cases.

Timely administration of tocilizumab improves outcome of hospitalized COVID-19 patients.

INTRODUCTION: The aim of this study was to determine the efficacy of early tocilizumab treatment for hospitalized patients with COVID-19 disease. METHODS: Open-label randomized phase II clinical trial investigating tocilizumab in patients with proven COVID-19 admitted to the general ward and in need of supplemental oxygen. The primary endpoint of the study was 30-day mortality with a prespecified 2-sided significance level of α = 0.10. A post-hoc analysis was performed for a combined endpoint of mechanical ventilation or death at 30 days. Secondary objectives included comparing the duration of hospital stay, ICU admittance and duration of ICU stay and the duration of mechanical ventilation. RESULTS: A total of 354 patients (67% men; median age 66 years) were enrolled of whom 88% received dexamethasone. Thirty-day mortality was 19% (95% CI 14%-26%) in the standard arm versus 12% (95% CI: 8%-18%) in the tocilizumab arm, hazard ratio (HR) = 0.62 (90% CI 0.39-0.98; p = 0.086). 17% of patients were admitted to the ICU in each arm (p = 0.89). The median stay in the ICU was 14 days (IQR 9-28) in the standard arm versus 9 days (IQR 5-14) in the tocilizumab arm (p = 0.014). Mechanical ventilation or death at thirty days was 31% (95% CI 24%-38%) in the standard arm versus 21% (95% CI 16%-28%) in the tocilizumab arm, HR = 0.65 (95% CI 0.42-0.98; p = 0.042). CONCLUSIONS: This randomized phase II study supports efficacy for tocilizumab when given early in the disease course in hospitalized patients who need oxygen support, especially when concomitantly treated with dexamethasone. TRIAL REGISTRATION: https://www.trialregister.nl/trial/8504.

Monocyte-derived macrophages aggravate pulmonary vasculitis via cGAS/STING/IFN-mediated nucleic acid sensing.

Autoimmune vasculitis is a group of life-threatening diseases, whose underlying pathogenic mechanisms are incompletely understood, hampering development of targeted therapies. Here, we demonstrate that patients suffering from anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) showed increased levels of cGAMP and enhanced IFN-I signature. To identify disease mechanisms and potential therapeutic targets, we developed a mouse model for pulmonary AAV that mimics severe disease in patients. Immunogenic DNA accumulated during disease onset, triggering cGAS/STING/IRF3-dependent IFN-I release that promoted endothelial damage, pulmonary hemorrhages, and lung dysfunction. Macrophage subsets played dichotomic roles in disease. While recruited monocyte-derived macrophages were major disease drivers by producing most IFN-ß, resident alveolar macrophages contributed to tissue homeostasis by clearing red blood cells and limiting infiltration of IFN-ß-producing macrophages. Moreover, pharmacological inhibition of STING, IFNAR-I, or its downstream JAK/STAT signaling reduced disease severity and accelerated recovery. Our study unveils the importance of STING/IFN-I axis in promoting pulmonary AAV progression and identifies cellular and molecular targets to ameliorate disease outcomes.

Myeloperoxidase is critically involved in the induction of organ damage after renal ischemia reperfusion.

In this study the role of myeloperoxidase (MPO) in a murine (C57BL/6) model of ischemia and reperfusion (I/R)-induced renal failure was investigated. The renal function after I/R was analyzed in MPO-deficient (Mpo(-/-)) mice and compared with wild-type (WT) controls. A significant reduction in renal function loss (blood urea nitrogen) was observed after 24 hours of reperfusion of ischemically damaged kidneys in Mpo(-/-) mice compared with I/R WT controls (I/R Mpo(-/-) = 31.3 +/- 1.7 mmol/L versus I/R WT = 42.8 +/- 2.1 mmol/L, sham = 7.0 +/- 0.5 mmol/L; P = 0.003). The early reperfusion phase (2 hours of reperfusion) was characterized by a substantial increase in apoptosis and early complement activation, surprisingly similar in Mpo(-/-) and WT mice. Improved renal function in Mpo(-/-) mice after extended reperfusion was accompanied by a reduced neutrophil influx (P = 0.017) compared with WT controls. Activation and deposition of complement was not significantly reduced in Mpo(-/-) mice compared with WT controls after 24 hours of reperfusion, indicating no specific in vivo role for MPO in activating complement after renal I/R. Taken together, these results demonstrated an important contribution of MPO in the induction of organ damage after renal I/R by influencing critical factors such as neutrophil extravasation but not complement activation.

TNF-alpha bioactivity-inhibiting therapy in ANCA-associated vasculitis: clinical and experimental considerations.

Wegener's granulomatosis, microscopic polyangiitis, idiopathic necrotizing crescentic glomerulonephritis, and Churg-Strauss syndrome are associated with the presence of ANCA with specificity for myeloperoxidase or proteinase 3. Current therapy consists mainly of corticosteroids and cyclophosphamide, but because this treatment regimen is associated with considerable morbidity, other treatment modalities remain desirable. There is compelling evidence that TNF-alpha plays an important role in the pathogenesis of ANCA-associated vasculitis. Consequently, inhibition of TNF-alpha bioactivity potentially results in attenuation of disease. This review discusses whether TNF-alpha bioactivity-inhibiting drugs are useful in the treatment of ANCA-associated vasculitis. The results of in vitro and in vivo experiments, as well as clinical studies, are evaluated. Although the importance of TNF-alpha during lesion development is evident, clinical trials that use TNF-alpha blockers in patients with ANCA-associated vasculitis give mixed results. Importantly, in a large-scale, randomized trial, treatment with etanercept was found not to be effective and resulted in an excess of treatment-related morbidity. It remains to be investigated whether inhibition of TNF-alpha bioactivity is effective in a subgroup of patients.

Anti-neutrophil cytoplasmic autoantibodies and leukocyte-endothelial interactions: a sticky connection?

Anti-neutrophil cytoplasmic autoantibodies (ANCA) with specificity for myeloperoxidase (MPO) or proteinase 3 (Pr3) are associated with systemic small-vessel vasculitides (SVV). Detection of ANCA is an established clinical tool in disease diagnosis and monitoring. Based on clinical and in vitro experimental evidence, a pathogenic role for ANCA has long been suspected, however, in vivo models in which causality can be tested have been lacking. Recently, an exciting novel rat model of MPO-ANCA-associated vasculitis has been described, which provides compelling evidence that MPO-ANCA are a primary pathogenic factor in SVV by augmenting leukocyte-endothelial interactions and vascular wall damage.

The role of neutrophils in the induction of glomerulonephritis by anti-myeloperoxidase antibodies.

In humans, circulating anti-neutrophil cytoplasm autoantibodies (ANCAs) with specificity for myeloperoxidase (MPO) are strongly associated with the development of pauci-immune necrotizing and crescentic glomerulonephritis (NCGN). In mice, we have demonstrated that intravenous injection of mouse antibodies specific for mouse MPO induces NCGN that closely mimics the human disease. We now report that the development of NCGN in this experimental model is accompanied by glomerular accumulation of neutrophils and macrophages. Neutrophil infiltration was most conspicuous at sites of glomerular necrosis and crescent formation, with macrophages also most numerous in crescents. Lymphocytes, however, were sparse in acute lesions. Importantly, mice that were depleted of circulating neutrophils with NIMP-R14 rat monoclonal antibodies were completely protected from anti-MPO IgG-induced NCGN. These findings provide direct evidence that neutrophils play a major role in the pathogenesis of anti-MPO-induced NCGN in this animal model and implicate neutrophils in the induction of human ANCA disease. This raises the possibility that therapeutic strategies to reduce circulating neutrophils could be beneficial to patients with ANCA-induced NCGN.

Aggravation of anti-myeloperoxidase antibody-induced glomerulonephritis by bacterial lipopolysaccharide: role of tumor necrosis factor-alpha.

Wegener's granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome, and idiopathic pauci-immune necrotizing crescentic glomerulonephritis are associated with myeloperoxidase (MPO)-specific anti-neutrophil cytoplasmic autoantibodies (ANCAs). Clinical and experimental evidence indicates that ANCA and proinflammatory stimuli of infectious origin act synergistically to cause vasculitis. We tested this hypothesis in a recently developed mouse model of anti-MPO IgG-induced glomerulonephritis by using bacterial lipopolysaccharide (LPS) as the proinflammatory stimulus. Systemic administration of LPS dose dependently increased renal injury induced by anti-MPO IgG as demonstrated by increased glomerular crescent formation and glomerular necrosis. In the early phase, LPS enhanced anti-MPO IgG-induced glomerular neutrophil accumulation. Furthermore, a transient induction of circulating tumor necrosis factor (TNF)-alpha levels, followed by a marked increase in circulating MPO levels, was observed on administration of LPS. In vitro, anti-MPO IgG induced a respiratory burst in murine neutrophils only after priming with TNF-alpha. Finally, anti-TNF-alpha treatment attenuated, but did not prevent, the LPS-mediated aggravation of anti-MPO IgG-induced glomerulonephritis. In conclusion, our study demonstrates that ANCA and proinflammatory stimuli act synergistically to induce vasculitic disease and suggests potential benefits of inhibiting TNF-alpha bioactivity in treating human ANCA-associated necrotizing crescentic glomerulonephritis.

Antineutrophil cytoplasmic autoantibodies and pathophysiology: new insights from animal models.

PURPOSE OF REVIEW: Since the discovery of antineutrophil cytoplasmic autoantibodies (ANCA) and their association with the occurrence of several types of small-vessel vasculitis, a causal relation between the two has been suggested. Various in vitro and in vivo experimental data provide indirect evidence in support of this view. This article comprises a review of the animal models that have been used to investigate the pathogenesis of ANCA-associated vasculitis, and focuses on recent developments in this field. RECENT FINDINGS: Xiao et al. provide definite proof of the pathogenic potential of ANCA in a novel mouse model of myeloperoxidase (MPO)-ANCA-associated vasculitis, in which transfer of splenocytes or IgG from MPO-/- mice immunized with murine MPO, to naive wild-type or Rag2-/- (lacking mature B and T lymphocytes) mice causes a disease remarkably similar to its human counterpart. In addition, preliminary studies by Smyth et al. show that immunization of Wistar Kyoto rats with human MPO induces antihuman MPO antibodies that cross-react with rat MPO, as well as a disease closely resembling human small-vessel vasculitis. Another murine ANCA model is the SCG/Kj mouse. A recent publication by Neumann et al., however, puts an important limitation on the use of this mouse model for the study of ANCA-associated vasculitis, demonstrating multiple immune complex deposits in the spontaneously occurring vascular lesions. SUMMARY Recently developed animal models of MPO-ANCA-associated vasculitis convincingly demonstrate that MPO-ANCA are pathogenic. Whether similar strategies can be used to develop an appropriate model for proteinase 3-ANCA-associated vasculitis remains to be investigated.