siRNA targeting variant C1858T of gene ptpn22
Dr Alessandra Fierabracci, IRCCS- Ospedale Pediatrico Bambino Gesù
IRCCS-Ospedale Pediatrico Bambino Gesù
Autoimmune diseases affect various organs or systems and their incidence is increasing worldwide. Autoimmune disorders are characterized by an abnormal reaction of the immune system, causing the human body to mistakenly attack normal cells and tissues. The potential pathophysiological role generated in various autoimmune conditions, including T1D (type 1 diabetes) and APS3v (autoimmune polyendocrine syndrome type 3 variant), by the C1858T polymorphism of the PTPN22 gene (tyrosine phosphatase protein N22) has recently aroused particular interest. PTPN22 gene encode for the Lyp protein and the variant C1858T causes in Lyp the replacement of the amino acid residue Arginine (Arg, R) in position 620 with tryptophan (Trp, W) (R620W). It is hypothesized that the subtle signal defects induced by the LypR620W variant could have implications for the tolerance that occurs in the thymus and this leads to the positive selection of autoimmune cells over-reacting against the body that would otherwise be negatively selected. Furthermore, in diabetic patients carrying the C1858T variant of PTPN22, were observed 1) altered B cell homeostasis and 2) altered response mediated by the Toll-Like receptor (TLR) 9, confirming the influence of the variant on both innate and adaptive immune responses. Therefore, the silencing of LypR620W represents a valid target to restore the normal immune function in subjects carrying the C1858T variant.
The invention fits in the innovative immunotherapeutic approaches of autoimmune diseases and concerns lipoplexes that interfere with the C1858T variant in order to bring Lyp expression to normal levels and thus restore the normal activity of the immune system. The innovative immunotherapy developed is based on short interfering RNAs (siRNA) for the selective inhibition of the allelic variant C1858T of PTPN22. The siRNAs consist of two antisense chains that recognize the target RNA to silence its expression in the cells where the siRNAs are incorporated. Systemic siRNA injection has been shown to be a viable approach for treating diseases related to gene defects however. To overcome siRNA degradation and transport difficulties, OPBG studies have led to the generation of lipoplexes, that are carrier agents consisting of lipophilic particles (liposomes) carrying the siRNAs within cells. The efficacy of the administration of lipoplexes in the downregulated PTPN22 gene has been demonstrated in preliminary studies in vitro and in vivo. We are now working on making the siRNA-liposome complexes more efficient to achieve the specific silencing of the Lyp variant in T lymphocytes. The use of OPBG lipoplexes can be extended also to the prevention of pathogenesis and ultimately achieve the treatment of autoimmune disorders in subjects carrying the variant C1858T. As regard of T1D, the treatment with lipoplexes would also preserve the pancreatic beta cells and improve the metabolic course of the disease.
Autoimmune diseases associated to C1858T variant: TD1, thyroiditis, myasthenia gravis, multiple sclerosis, SLE, Wegener’s granulomatosis, rheumatoid arthritis, juvenile idiopathic arthritis, celiac disease, vitiligo, Sjӧgren syndrome, Addison disease, alopecia, giant cell arteritis, polymyositis.
The patent reached a technology readiness level of 3 and we expect to complete the preclinical studies in about two years.
The patent has been granted in Italy on May 26th, 2020. The international application is now in the Regional Phase and it has been extended to Europe and USA.
PMID 15004560, PMID28437437