PINK1 is a target of T cell responses in Parkinson's disease

Parkinson's disease (PD) is associated with autoimmune T cells that recognize the protein alpha-synuclein in a subset of individuals. Multiple neuroantigens are targets of autoinflammatory T cells in classical central nervous system autoimmune diseases such as multiple sclerosis (MS). Here, we explored whether additional autoantigenic targets of T cells in PD. We generated 15-mer peptide pools spanning several PD-related proteins implicated in PD pathology, including GBA, SOD1, PINK1, parkin, OGDH, and LRRK2. Cytokine production (IFNγ, IL-5, IL-10) against these proteins was measured using a fluorospot assay and PBMCs from patients with PD and age-matched healthy controls. This approach identified unique epitopes and their HLA restriction from the mitochondrial-associated protein PINK1, a regulator of mitochondrial stability, as an autoantigen targeted by T cells. The T cell reactivity was predominantly found in male patients with PD, which may contribute to the heterogeneity of PD. Identifying and characterizing PINK1 and other autoinflammatory targets may lead to antigen-specific diagnostics, progression markers, and/or novel therapeutic strategies for PD.

A GMCSF-Neuroantigen Tolerogenic Vaccine Elicits Systemic Lymphocytosis of CD4+ CD25high FOXP3+ Regulatory T Cells in Myelin-Specific TCR Transgenic Mice Contingent Upon Low-Efficiency T Cell Antigen Receptor Recognition

Previous studies showed that single-chain fusion proteins comprised of GM-CSF and major encephalitogenic peptides of myelin, when injected subcutaneously in saline, were potent tolerogenic vaccines that suppressed experimental autoimmune encephalomyelitis (EAE) in rats and mice. These tolerogenic vaccines exhibited dominant suppressive activity in inflammatory environments even when emulsified in Complete Freund's Adjuvant (CFA). The current study provides evidence that the mechanism of tolerance was dependent upon vaccine-induced regulatory CD25⁺ T cells (Tregs), because treatment of mice with the Treg-depleting anti-CD25 mAb PC61 reversed tolerance. To assess tolerogenic mechanisms, we focused on 2D2-FIG mice, which have a transgenic T cell repertoire that recognizes myelin oligodendrocyte glycoprotein peptide MOG35-55 as a low-affinity ligand and the neurofilament medium peptide NFM13-37 as a high-affinity ligand. Notably, a single subcutaneous vaccination of GMCSF-MOG in saline elicited a major population of FOXP3⁺ Tregs that appeared within 3 days, was sustained over several weeks, expressed canonical Treg markers, and was present systemically at high frequencies in the blood, spleen, and lymph nodes. Subcutaneous and intravenous injections of GMCSF-MOG were equally effective for induction of FOXP3⁺ Tregs. Repeated booster vaccinations with GMCSF-MOG elicited FOXP3 expression in over 40% of all circulating T cells. Covalent linkage of GM-CSF with MOG35-55 was required for Treg induction whereas vaccination with GM-CSF and MOG35-55 as separate molecules lacked Treg-inductive activity. GMCSF-MOG elicited high levels of Tregs even when administered in immunogenic adjuvants such as CFA or Alum. Conversely, incorporation of GM-CSF and MOG35-55 as separate molecules in CFA did not support Treg induction. The ability of the vaccine to induce Tregs was dependent upon the efficiency of T cell antigen recognition, because vaccination of 2D2-FIG or OTII-FIG mice with the high-affinity ligands GMCSF-NFM or GMCSF-OVA (Ovalbumin323-339), respectively, did not elicit Tregs. Comparison of 2D2-FIG and 2D2-FIG-Rag1 ^-/- strains revealed that GMCSF-MOG may predominantly drive Treg expansion because the kinetics of vaccine-induced Treg emergence was a function of pre-existing Treg levels. In conclusion, these findings indicate that the antigenic domain of the GMCSF-NAg tolerogenic vaccine is critical in setting the balance between regulatory and conventional T cell responses in both quiescent and inflammatory environments.

Tolerogenic vaccines for Multiple sclerosis

Tolerogenic vaccines represent a new class of vaccine designed to re-establish immunological tolerance, restore immune homeostasis, and thereby reverse autoimmune disease. Tolerogenic vaccines induce long-term, antigen-specific, inhibitory memory that blocks pathogenic T cell responses via loss of effector T cells and gain of regulatory T cell function. Substantial advances have been realized in the generation of tolerogenic vaccines that inhibit experimental autoimmune encephalomyelitis in a preclinical setting, and these vaccines may be a prequel of the tolerogenic vaccines that may have therapeutic benefit in Multiple Sclerosis. The purpose here is to provide a snapshot of the current concepts and future prospects of tolerogenic vaccination for Multiple Sclerosis, along with the central challenges to clinical application.

Virus-specific and autoreactive T cell lines isolated from cerebrospinal fluid of a patient with chronic rubella panencephalitis

Using a recently described technique for expanding of human T lymphocyte populations from cerebrospinal fluid (CSF), we investigated the local cellular immune response in a patient with chronic rubella panencephalitis. A total of 328 T cell lines (TCLs) was established by seeding CSF cells at limiting dilution into histoplates in the presence of irradiated feeder cells and phytohemagglutinin (PHA)-containing conditioned medium. 80% of TCLs expressed the CD4+CD8-, 5% the CD4-CD8+ phenotype and 15% of TCLs contained different proportions of CD4+ and CD8+ cells. Of 191 TCLs analyzed, 85 were cytotoxic, as shown by their lectin-dependent cytotoxicity against allogeneic uninfected target cells. Eight of them demonstrated specificity for the autologous, rubella virus-infected target cells. When tested for antigen-specific proliferative activity, 26 TCLs responded to rubella antigen, 16 TCLs reacted to myelin basic protein (MBP), four TCLs to proteolipid protein (PLP), four to galactocerebrosides and two to actin. Fourteen out of 16 MBP-specific TCLs also responded, to a minor degree, to rubella antigen and/or actin. The results showed that the persisting rubella infection had given rise to autoreactive T cells. Virus-induced autoreactivity to brain antigens may be an important pathogenetic mechanism in other chronic inflammatory disorders of the CNS.