COPA Syndrome from Diagnosis to Treatment: A Clinician's Guide

The pathogenesis, clinical presentations and treatment of monogenic systemic vasculitis

Many monogenic autoinflammatory diseases, including DADA2 (deficiency of adenosine deaminase 2), HA20 (haploinsufficiency of A20), SAVI (STING-associated vasculopathy with onset in infancy), COPA syndrome, LAVLI (LYN kinase-associated vasculopathy and liver fibrosis) and VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, present predominantly with vasculitis and constitute a substantial subgroup of vasculitic conditions associated with a 'probable aetiology'. The spectrum of monogenic vasculitis encompasses all sizes and types of blood vessel, ranging from large vessels to medium-size and small vessels, and from the arterial side to the venous side of the vasculature. Monogenic vasculitis typically starts early in life during infancy or childhood; VEXAS syndrome, which presents in late adulthood, is an exception. The activation of myeloid cells via inflammasome and nuclear factor-κB pathways, type I interferon-enhanced autoimmune mechanisms and/or dysregulated adaptive immune responses have an important role in the development of immune-mediated endothelial dysfunction and vascular damage. Genetic testing is essential for the diagnosis of underlying monogenic autoinflammatory diseases; however, the penetrance of genetic variants can vary. Increased awareness and recognition of distinctive clinical findings could facilitate earlier diagnosis and allow for more-targeted treatments.

The common HAQ STING allele prevents clinical penetrance of COPA syndrome

COPA syndrome, an autosomal-dominant inborn error of immunity, is nonpenetrant in ∼20% of individuals, with no known mediators of protection. Recent studies implicate STING in the pathogenesis of COPA syndrome. We show that the common HAQ STING allele mediates complete clinical protection. We sequenced 35 individuals with COPA mutations, 26 affected patients and 9 unaffected carriers, finding HAQ STING co-segregation with clinical nonpenetrance. Exome sequencing identified only the mutations comprising HAQ STING as variants shared by unaffected carriers and absent in patients. Experimentally, we found that HAQ STING acts dominantly to dampen COPA-dependent STING signaling. Expressing HAQ STING in patient cells rescued the molecular phenotype of COPA syndrome. Our study is the first report of a common and well-tolerated allele mediating complete clinical protection from a severe genetic disorder. Our findings redefine the diagnostic criteria for COPA syndrome, expose functional differences among STING alleles with broad scientific and clinical implications, and reveal a potential universal gene therapy approach for patients.

Targeting the Type I Interferon Pathway in Glomerular Kidney Disease: Rationale and Therapeutic Opportunities

Type I interferons (IFNs) are immunostimulatory molecules that can activate the innate and adaptive immune systems. In cases of immune dysfunction, prolonged activation of the type I IFN pathway has been correlated with kidney tissue damage in a wide range of kidney disorders, such as lupus nephritis (LN) and focal segmental glomerulosclerosis (FSGS). Genetic mutations, such as APOL1 risk variants in conjunction with elevated type I IFN expression, are also associated with higher rates of chronic kidney disease in patients with LN and collapsing FSGS. Long-term activation of the type I IFN pathway can result in chronic inflammation, leading to kidney tissue damage, cell death, and decline in organ function. Thus, therapeutic strategies targeting type I IFN could provide clinical benefits to patients with immune dysregulation who are at risk of developing impaired kidney function. Here, we present a critical review of type I IFN signaling, the consequences of chronically elevated type I IFN expression, and therapeutic strategies targeting type I IFN signaling in the context of kidney disease.

COPA Syndrome-From Pathogenesis to Treatment

Coatomer subunit α (COPA) syndrome is a mendelian autosomal dominant immune dysregulation disease characterized by early onset lung disease in the form of diffuse alveolar hemorrhaging or interstitial lung disease, frequently associated with arthritis, glomerulonephritis, and high titer autoantibodies usually mimicking other autoimmune diseases. While immunosuppressive medication has been effective in controlling arthritis, data on long-term lung disease control remains scarce, which poses a real challenge as the progression of lung disease is the main cause of poor life expectancy in COPA patients. Nevertheless, JAK inhibitor therapy seems to be the most promising therapeutic choice now.

Non-infectious mixed cryoglobulinemia as a new clinical presentation of mutation in the gene encoding coatomer subunit alpha: a case report of two adult sisters

Cryoglobulinemia is a rare disease characterized by the presence of cryoglobulins in the blood serum. It is usually caused by autoimmune, lymphoproliferative, or infectious factors. The pathogenesis of cryoglobulinemia is not well understood, therefore, genetic testing is very important. We present the case of two adult sisters with different clinical phenotypes of non-infectious cryoglobulinemic vasculitis associated with a rare genetic variant [(Hg38) 1:160323529 C>G, NP_004362.2:p.(Gly203Ala)]. One of the sisters suffered from essential mixed cryoglobulinemia, while the other suffered from cryoglobulinemia associated with systemic connective tissue disease. In both cases, genetic tests revealed a variant in the COPA gene, encoding coatomer subunit alpha. Mutations in the COPA gene are associated with COPA syndrome, an autoimmune interstitial lung, joint, and kidney monogenic disease, found mainly in children. Only 15 pathogenic COPA variants have been reported thus far which suggests that the full spectrum of disease manifestations remains unknown. Ours is the first report of the association of the COPA gene with non-infectious cryoglobulinemic vasculitis in adults. This unexpected finding may direct research into the pathogenesis of cryoglobulinemia and new treatment strategies for this rare disease.

Activated STING in the thymus alters T cell development and selection leading to autoimmunity

Classifying systemic inflammatory disorders as autoinflammatory or autoimmune provides insight into disease pathogenesis and whether treatment should target innate molecules and their signaling pathways or the adaptive immune response. COPA syndrome is a monogenic disorder of immune dysregulation that leads to interstitial lung disease and high-titer autoantibodies. Studies show constitutive activation of the innate immune molecule STING is centrally involved in disease. However, the mechanisms by which STING results in loss of T cell tolerance and autoimmunity in COPA syndrome or more common autoimmune diseases is not understood. Using CopaE241K/+ mice, we uncovered a functional role for STING in the thymus. Single cell data of human thymus demonstrates STING is highly expressed in medullary thymic epithelial cells (mTECs) involved in processing and presenting self-antigens to thymocytes. In CopaE241K/+ mice, activated STING in mTECs triggered interferon signaling, impaired macroautophagy and caused a defect in negative selection of T cells. Wild-type mice given a systemic STING agonist phenocopied the selection defect and showed enhanced thymic escape of a T cell clone targeting a self-antigen also expressed in melanoma. Our work demonstrates STING activation in TECs shapes the T cell repertoire and contributes to autoimmunity, findings important for settings that activate thymic STING.