THU0019 INTRON REGIONS OF PIK3AP1 (BCAP) AND SPON2 (SPONDIN-2) GENES ARE DIFFERENTIALLY METHYLATED IN PATIENTS WITH PERIODIC FEVER, APHTHOUS STOMATITIS, PHARYNGITIS AND ADENITIS (PFAPA) SYNDROME

Background:Periodic fever, aphthous stomatitis, pharyngitis and adenitis (PFAPA) syndrome is the most common autoinflammatory disease in children, often grouped together with hereditary periodic fever syndromes, although its cause and hereditary nature remain unexplained.Objectives:We investigated whether a differential DNA methylation was present in DNA from peripheral blood mononuclear cells (PBMC) in patients with PFAPA versus a group of healthy young individuals.Methods:A whole epigenome analysis (MeDIP and MBD) was performed using pooled DNA libraries enriched for methylated genomic regions. Of identified candidate genes, two with most significantly different methylation leves were further evaluated with methylation specific restriction enzymes coupled with qPCR (MSRE-qPCR).Results:The analysis showed thatPIK3AP1andSPON2intronic gene regions are differentially methylated in patients with PFAPA. MSRE-qPCR proved as a quick, reliable and cost-effective method to confirm results from MeDIP and MBD.Conclusion:Our findings indicate that B cell adapter protein (BCAP) as PI3K binding inhibitor of inflammation and spondin-2 (SPON2) as a pattern recognition molecule and integrin ligand could play a role in etiology of PFAPA. Their role and impact of changed DNA methylation in PFAPA etiology and autoinflammation need further investigation.References:[1]Wekell P. Periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis syndrome – PFAPA syndrome. Press Medicale [Internet]. 2019;48(1):e77–87. Available from:https://doi.org/10.1016/j.lpm.2018.08.016[2]K. Theodoropoulou, F. Vanoni, and M. Hofer, “Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Cervical Adenitis (PFAPA) Syndrome: a Review of the Pathogenesis,”Curr. Rheumatol. Rep., vol. 18:18, 2016.[3]Carpentier SJ, Ni M, Duggan JM, James RG, Cookson BT, Hamerman JA. The signaling adaptor BCAP inhibits NLRP3 and NLRC4 inflammasome activation in macrophages through interactions with Flightless-1. Sci Signal. 2019;12(581).[4]He YW, Li H, Zhang J, Hsu CL, Lin E, Zhang N, et al. The extracellular matrix protein mindin is a pattern-recognition molecule for microbial pathogens. Nat Immunol. 2004;5(1):88–97.Disclosure of Interests:None declared

PTX3, a Humoral Pattern Recognition Molecule, in Innate Immunity, Tissue Repair, and Cancer

Innate immunity includes a cellular and a humoral arm. PTX3 is a fluid-phase pattern recognition molecule conserved in evolution which acts as a key component of humoral innate immunity in infections of fungal, bacterial, and viral origin. PTX3 binds conserved microbial structures and self-components under conditions of inflammation and activates effector functions (complement, phagocytosis). Moreover, it has a complex regulatory role in inflammation, such as ischemia/reperfusion injury and cancer-related inflammation, as well as in extracellular matrix organization and remodeling, with profound implications in physiology and pathology. Finally, PTX3 acts as an extrinsic oncosuppressor gene by taming tumor-promoting inflammation in murine and selected human tumors. Thus evidence suggests that PTX3 is a key homeostatic component at the crossroad of innate immunity, inflammation, tissue repair, and cancer. Dissecting the complexity of PTX3 pathophysiology and human genetics paves the way to diagnostic and therapeutic exploitation.

Properdin binding to complement activating surfaces depends on initial C3b deposition

Two functions have been assigned to properdin; stabilization of the alternative convertase, C3bBb, is well accepted, whereas the role of properdin as pattern recognition molecule is controversial. The presence of nonphysiological aggregates in purified properdin preparations and experimental models that do not allow discrimination between the initial binding of properdin and binding secondary to C3b deposition is a critical factor contributing to this controversy. In previous work, by inhibiting C3, we showed that properdin binding to zymosan and Escherichia coli is not a primary event, but rather is solely dependent on initial C3 deposition. In the present study, we found that properdin in human serum bound dose-dependently to solid-phase myeloperoxidase. This binding was dependent on C3 activation, as demonstrated by the lack of binding in human serum with the C3-inhibitor compstatin Cp40, in C3-depleted human serum, or when purified properdin is applied in buffer. Similarly, binding of properdin to the surface of human umbilical vein endothelial cells or Neisseria meningitidis after incubation with human serum was completely C3-dependent, as detected by flow cytometry. Properdin, which lacks the structural homology shared by other complement pattern recognition molecules and has its major function in stabilizing the C3bBb convertase, was found to bind both exogenous and endogenous molecular patterns in a completely C3-dependent manner. We therefore challenge the view of properdin as a pattern recognition molecule, and argue that the experimental conditions used to test this hypothesis should be carefully considered, with emphasis on controlling initial C3 activation under physiological conditions.