Primary screening of chemically modified immunosuppressive oligonucleotides using in vitro model with spleen lymphocytes

Control of immune response following transplantation of cells, tissues, or organs includes reduction negative effects caused by acute graft-versus-host disease (GVHD) developing during bone marrow transplantation, thus being an urgent task of modern clinical practice. In this view, the management of immunological tolerance is a promising approach, in particular, the ability of immune cells (especially, dendritic cells) to induce this response using experimental models of allogeneic transplant rejection, GVHD and autoimmune disorders. Therefore, the search for compounds that can effectively activate or suppress immune cells and regulate immunological tolerance is of importance. The purpose of this work was to study the effects of synthetic immunosuppressive oligodeoxynucleotides (INH-ODN) on in vitro splenocyte proliferation and IL-12 production, in order to select the most promising compounds for subsequent in vivo experiments. We have tested several immunosuppressive agents: thiophosphate oligodeoxynucleotides (A151, ODN2088 and ODN4084-F), which include G-rich regions, as well as their analogues, i.e., thiophosphate oligodeoxynucleotides with mesylphosphoramide (ì) modifications at GpG bonds (ì-A151, ì-ODN2088 and ì-ODN4084-F). The effects of chemically modified oligonucleotides were assessed in the in vitro model of CpG-stimulated splenocytes, using CpG-ODN SD-101 in its complete thiophosphate (PS) version. Primary in vitro screening of immunosuppressive oligonucleotides by their effect on splenocyte proliferation and IL-12 production enabled us to identify the most active compounds and determine the features of sequences with the most pronounced immunosuppressive properties, as well as establish optimal concentrations of the studied oligodeoxynucleotides selected for subsequent in vivo studies.