Abstract
In this study we analysed the effects of prophylactic biolistic DNA vaccination with plasmids encoding the encephalitogenic protein myelin oligodendrocyte glycoprotein (MOG) on the severity of a subsequently MOGp35-55-induced EAE and on the underlying immune response. We compared the outcome of vaccination with MOG-encoding plasmids alone or in combination with vectors encoding the regulatory cytokines IL-10 and TGF-ß1, respectively. MOG expression was restricted to skin dendritic cells (DCs) by the use of the DC-specific promoter of the fascin1 gene (pFscn-MOG). For comparison, the strong and ubiquitously active CMV promoter was employed (pCMV-MOG), which allows MOG expression in all transfected cells. Expression of IL-10 and TGF-ß1 was controlled by the CMV promoter to yield maximal synthesis (pCMV-IL10, pCMV-TGFß). Co-application of pFscn-MOG and pCMV-IL10 significantly ameliorated EAE pathology, while vaccination with pCMV-MOG plus pCMV-IL10 did not affect EAE outcome. In contrast, vaccination with either of the two MOG-encoding plasmids in combination with pCMV-TGFß significantly attenuated the clinical EAE symptoms. Mechanistically, we observed diminished infiltration of Th17 and Th1 cells as well as macrophages/DCs into the CNS, which correlated with decreased MOGp35-55-specific production of IL-17 and IFN-ϫ by spleen cells and reduced peptide-specific T cell proliferation. Our findings suggest deletion of or anergy induction in MOG-specific CD4+ T cells by the suppressive vaccination platform employed. MOG expression driven by the DC-specific fascin1 promoter yielded similar inhibitory effects on EAE progression as the ubiquitously active viral CMV promoter, when coapplying pCMV-TGFß. Our finding that pCMV-IL10 promoted tolerogenic effects only, when coapplied with pFscn-MOG, but not pCMV-MOG suggests that IL-10 affected only directly transfected DCs (pFscn-MOG), but not neighbouring DCs that engulfed MOG-containing vesicles derived from transfected keratinocytes (pCMV-MOG). Thus, due to its DC-restricted expression, the fascin1 promoter might be an interesting alternative to ubiquitously expressed promoters for vaccination strategies.
Highlights
Multiple sclerosis (MS) is an inflammatory and demyelinating condition of the central nervous system (CNS), characterized by parenchymal infiltration of immune cells composed largely of T cells and macrophages [1]
To protect mice via biolistic DNA vaccination from EAE development, induced by their treatment with MOGp35-55 peptide/complete Freunds adjuvant (CFA) and pertussis toxin, we generated myelin oligodendrocyte glycoprotein (MOG)-encoding expression plasmids and plasmids encoding the immunoregulatory cytokine TGF-ß1 and IL10, respectively, which were reported earlier to induce a tolerogenic state in dendritic cells (DCs) and T cells [20,21]
Following activation and differentiation in the periphery these T cell populations migrate to the CNS, where they are reactivated antigen- by CNS-resident APCs leading to an inflammatory response with ensuing progressive pathology [33,34]
Summary
Multiple sclerosis (MS) is an inflammatory and demyelinating condition of the central nervous system (CNS), characterized by parenchymal infiltration of immune cells composed largely of T cells and macrophages [1]. High similarities in terms of CNS immune cell infiltration, myelin destruction, neuronal death and subsequently paralysis as seen in MS patients, can be experimentally induced in laboratory rodents by immunization with CNS-derived antigens [3]. This form of disease induction, known as experimental autoimmune encephalomyelitis (EAE), is frequently used when attempting to study disease pathogenesis and testing innovative treatments. DCs may play a major role in the context of MS and its experimental model, as they shape the T cell repertoire, as well as activate and differentiate myelin-specific autoreactive T cells, which initiate disease pathology [5]
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