Genetics, Pathophysiology, and Treatment of Recessive Autoinflammatory Diseases

National Human Genome Research Institute

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Abstract

During the current reporting period we have focused on the following projects: 1) Natural history of the deficiency of adenosine deaminase 2 (DADA2) In previous reporting periods we published manuscripts in the New England Journal of Medicine (2014, 2019) first describing a new disorder we named the deficiency of adenosine deaminase 2 (DADA2), which is a recessively inherited illness caused by biallelic loss-of-function mutations in ADA2 that presents with fevers, recurrent strokes, livedo racemosa, and polyarteritis nodosa, and then showing that inhibitors of tumor necrosis factor (TNF) are very effective in preventing strokes in DADA2. We currently follow what is probably the largest cohort of DADA2 patients in the world. In early 2022 we published an observational analysis of what was then a 60-patient single-center DADA2 cohort, describing the multisystem disease that may span multiple medical specialties. In this report we summarized the broad phenotypic presentation, as well as our experience with hematopoietic cell transplantation and COVID-19. Disease manifestations could be separated into three major phenotypes: inflammatory/vascular, immune dysregulatory, and hematologic. However, most patients presented with significant overlap among these three phenotype groups. The cardinal features of the inflammatory/vascular group included cutaneous manifestations and stroke. Evidence of immune dysregulation was commonly observed, including hypogammaglobulinemia, absent to low class-switched memory B cells, and inadequate response to vaccination. Despite these findings, infectious complications were exceedingly rare in this cohort. Hematologic findings including pure red cell aplasia (PRCA), immune-mediated neutropenia, and pancytopenia were observed in half of patients. We significantly extended our experience using anti-TNF agents, with no strokes observed in 2026 patient months on TNF inhibitors. Meanwhile, hematologic and immune features had a more varied response to anti-TNF therapy. Six patients received a total of 10 allogeneic hematopoietic cell transplant (HCT) procedures, with secondary graft failure necessitating repeat HCTs in three patients, as well as unplanned donor cell infusions to avoid graft rejection. All transplanted patients had been on anti-TNF agents prior to HCT and received varying degrees of reduced-intensity or non-myeloablative conditioning. All transplanted patients are still alive and have discontinued anti-TNF therapy. The long-term follow up afforded by this large single-center study underscores the clinical heterogeneity of DADA2 and the potential for phenotypes to evolve in any given patient. 2) Treatment of the deficiency of adenosine deaminase 2 (DADA2) In early 2022 we also published a manuscript examining the pathophysiology and the underlying mechanisms of TNF-inhibitor response in DADA2 patients. In this study we used flow cytometry, intracellular cytokine staining, transcriptome analysis, immunohistochemistry, and cell differentiation experiments to define an inflammatory signature in patients with DADA2 and studied their response to TNF-inhibitor treatment. We demonstrated increased inflammatory signals and overproduction of cytokines mediated by interferon and nuclear factor kappa B pathways in patients primary cells. Treatment with TNF inhibitors led to reduction in inflammation, rescued the skewed differentiation toward the proinflammatory M1 macrophage subset, and restored integrity of endothelial cells in blood vessels. We also reported 8 novel disease-associated variants in 7 patients with DADA2. We concluded that DADA2 vasculitis is strongly related to the presence of activated myeloid cells, and the endothelial cell damage is rescued with anti-TNF treatment. 3) OTULIN haploinsufficiency In a previous reporting period we published a paper in the Proceedings of the National Academy of Sciences USA, describing what was then a new autoinflammatory disease caused by biallelic loss-of-function mutations in OTULIN, which encodes a deubiquitylase that removes linear ubiquitin chains that would ordinarily stabilize proinflammatory signaling complexes. The deficiency of OTULIN causes increased NF-kappa B signaling. During the current reporting period collaborators at the Rockefeller University performed a genome-wide analysis of the exomes of 105 patients with life-threatening staphylococcal disease and 1274 controls. They found enrichment for heterozygous OTULIN variants in patients with severe staphylococcal disease. Patients who are haploinsufficient for OTULIN suffered from episodes of life-threatening necrosis, typically triggered by S. aureus infection. OTULIN haploinsufficiency caused an accumulation of linear ubiquitin in dermal fibroblasts, but tumor necrosis factor receptor-mediated nuclear factor kappa B signaling remained intact. Blood leukocytes were unaffected. The OTULIN-dependent accumulation of caveolin-1 in dermal fibroblasts, but not leukocytes, facilitated the cytotoxic damage inflicted by staphylococcal virulence factor alpha-toxin. Naturally elicited antibodies against alpha-toxin contributed to incomplete clinical penetrance. We concluded that human OTULIN haploinsufficiency underlies life-threatening staphylococcal disease by disrupting cell-intrinsic immunity to alpha-toxin in nonleukocytic cells. A manuscript reporting these findings was published in Science during the current reporting period.