Inhibition of experimental autoimmune encephalomyelitis by tolerance-promoting DNA vaccination focused to dendritic cells

The DNA co-vaccination using Sm antigen and IL-10 as prophylactic experimental therapy ameliorates nephritis in a model of lupus induced by pristane

Introduction

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies such as anti-Sm. Studies in patients with SLE and murine models of lupus reveal that the most critical anti-Sm autoantibodies are predominantly direct against D1_(83–119), D2, and B´/B epitopes.

Objectives

The present study aimed to analyze the induction of antigen-specific tolerance after prophylactic immunization with a DNA vaccine encoding the epitopes: D1_83-119, D2, B´/B, and B´/B_COOH in co-vaccination with IFN-γ or IL-10 in a murine model of lupus induced by pristane.

Material and methods

To obtain endotoxin-free DNA vaccines, direct cloning techniques using pcDNA were performed: D1_83-119, D2, B´/B, B´/B_COOH, IFN-γ, or IL-10. Lupus was induced by 0.5 mL of pristane via intraperitoneal in BALB/c female mice. Immunoprecipitation with K562 cells was metabolically labeled with ³⁵S and ELISA to detect serum antibodies or mice IgG1, IgG2a isotypes. ELISA determined IL-10 and IFN-γ from splenocytes supernatants. Proteinuria was assessed monthly, and lupus nephritis was evaluated by immunofluorescence, and electron microscopy.

Results

The prophylactic co-vaccination with D2/IL-10 reduced the expression of kidney damage observed by electron microscopy, direct immunofluorescence, and H & E, along with reduced level of anti-nRNP/Sm antibodies (P = 0.048).

Conclusion

The prophylactic co-vaccination of IL-10 with D2 in pristane-induced lupus ameliorates the renal damage maybe by acting as prophylactic DNA tolerizing therapy.

Emerging Therapeutics for Immune Tolerance: Tolerogenic Vaccines, T cell Therapy, and IL-2 Therapy

Autoimmune diseases affect roughly 5-10% of the total population, with women affected more than men. The standard treatment for autoimmune or autoinflammatory diseases had long been immunosuppressive agents until the advent of immunomodulatory biologic drugs, which aimed at blocking inflammatory mediators, including proinflammatory cytokines. At the frontier of these biologic drugs are TNF-α blockers. These therapies inhibit the proinflammatory action of TNF-α in common autoimmune diseases such as rheumatoid arthritis, psoriasis, ulcerative colitis, and Crohn's disease. TNF-α blockade quickly became the "standard of care" for these autoimmune diseases due to their effectiveness in controlling disease and decreasing patient's adverse risk profiles compared to broad-spectrum immunosuppressive agents. However, anti-TNF-α therapies have limitations, including known adverse safety risk, loss of therapeutic efficacy due to drug resistance, and lack of efficacy in numerous autoimmune diseases, including multiple sclerosis. The next wave of truly transformative therapeutics should aspire to provide a cure by selectively suppressing pathogenic autoantigen-specific immune responses while leaving the rest of the immune system intact to control infectious diseases and malignancies. In this review, we will focus on three main areas of active research in immune tolerance. First, tolerogenic vaccines aiming at robust, lasting autoantigen-specific immune tolerance. Second, T cell therapies using Tregs (either polyclonal, antigen-specific, or genetically engineered to express chimeric antigen receptors) to establish active dominant immune tolerance or T cells (engineered to express chimeric antigen receptors) to delete pathogenic immune cells. Third, IL-2 therapies aiming at expanding immunosuppressive regulatory T cells in vivo.

Nucleic Acid-Based Approaches for Tumor Therapy

Within the last decade, the introduction of checkpoint inhibitors proposed to boost the patients' anti-tumor immune response has proven the efficacy of immunotherapeutic approaches for tumor therapy. Furthermore, especially in the context of the development of biocompatible, cell type targeting nano-carriers, nucleic acid-based drugs aimed to initiate and to enhance anti-tumor responses have come of age. This review intends to provide a comprehensive overview of the current state of the therapeutic use of nucleic acids for cancer treatment on various levels, comprising (i) mRNA and DNA-based vaccines to be expressed by antigen presenting cells evoking sustained anti-tumor T cell responses, (ii) molecular adjuvants, (iii) strategies to inhibit/reprogram tumor-induced regulatory immune cells e.g., by RNA interference (RNAi), (iv) genetically tailored T cells and natural killer cells to directly recognize tumor antigens, and (v) killing of tumor cells, and reprograming of constituents of the tumor microenvironment by gene transfer and RNAi. Aside from further improvements of individual nucleic acid-based drugs, the major perspective for successful cancer therapy will be combination treatments employing conventional regimens as well as immunotherapeutics like checkpoint inhibitors and nucleic acid-based drugs, each acting on several levels to adequately counter-act tumor immune evasion.

Comprehensive analysis of DNA methylation and gene expression in orally tolerized T cells

T cell anergy is known to be a crucial mechanism for various types of immune tolerance, including oral tolerance. The expression of several anergy-specific genes was reportedly up-regulated in anergic T cells, and played important roles in the cells. However, how the genes were up-regulated has not been understood. In this study, we comprehensively analyzed the altered gene expression and DNA methylation status in T cells tolerized by oral antigen in vivo. Our results showed that many genes were significantly up-regulated in the orally tolerized T cells, and most of the genes found in this study have not been reported previously as anergy related genes; for example, ribosomal protein L41 (FC = 3.54E06, p = 3.70E-09: Fisher's exact test; the same applies hereinafter) and CD52 (FC = 2.18E05, p = 3.44E-06). Furthermore, we showed that the DNA methylation statuses of many genes; for example, enoyl-coenzyme A delta isomerase 3 (FC = 3.62E-01, p = 3.01E-02) and leucine zipper protein 1 (FC = 4.80E-01, p = 3.25E-02), including the ones distinctly expressed in tolerized T cells; for example, latexin (FC = 3.85E03, p = 4.06E-02 for expression; FC = 7.75E-01, p = 4.13E-01 for DNA methylation) and small nuclear ribonucleoprotein polypeptide F (FC = 3.12E04, p = 4.46E-04 for expression; FC = 8.56E-01, p = 5.15E-01 for DNA methylation), changed during tolerization, suggesting that the distinct expression of some genes was epigenetically regulated in the tolerized T cells. This study would contribute to providing a novel clue to the fine understanding of the mechanism for T cell anergy and oral tolerance.

Inhibition of antigen-specific immune responses by co-application of an indoleamine 2,3-dioxygenase (IDO)-encoding vector requires antigen transgene expression focused on dendritic cells

We have previously shown that particle-mediated epidermal delivery (PMED) of plasmids encoding β-galactosidase (βGal) under control of the fascin-1 promoter (pFascin-βGal) yielded selective production of the protein in skin dendritic cells (DCs), and suppressed Th2 responses in a mouse model of type I allergy by inducing Th1/Tc1 cells. However, intranasal challenge of mice immunized with pFascin-βGal induced airway hyperreactivity (AHR) and neutrophilic inflammation in the lung. The tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) has been implicated in immune suppression and tolerance induction. Here we investigated the consequences of co-application of an IDO-encoding vector on the modulatory effect of DNA vaccination by PMED using pFascin-βGal in models of eosinophilic allergic and non-eosinophilic intrinsic airway inflammation. IDO-encoding plasmids and pFascin-βGal or pCMV-βGal were co-applied to abdominal skin of BALB/c mice without, before or after sensitization with βGal protein. Immune responses in the lung were analysed after intranasal provocation and airway reactivity was determined by whole body plethysmography. Co-application of pCMV-IDO with pFascin-βGal, but not pCMV-βGal inhibited the Th1/Tc1 immune response after PMED. Moreover, AHR in those mice was attenuated following intranasal challenge. Therapeutic vaccination of βGal-sensitized mice with pFascin-βGal plus pCMV-IDO slightly suppressed airway inflammation and AHR after provocation with βGal protein, while prophylactic vaccination was not effective. Altogether, our data suggest that only the combination of DC-restricted antigen and ubiquitous IDO expression attenuated asthma responses in mice, most probably by forming a tryptophan-depleted and kynurenine-enriched micromilieu known to affect neutrophils and T cells.

DNA Vaccines-How Far From Clinical Use?

Two decades ago successful transfection of antigen presenting cells (APC) in vivo was demonstrated which resulted in the induction of primary adaptive immune responses. Due to the good biocompatibility of plasmid DNA, their cost-efficient production and long shelf life, many researchers aimed to develop DNA vaccine-based immunotherapeutic strategies for treatment of infections and cancer, but also autoimmune diseases and allergies. This review aims to summarize our current knowledge on the course of action of DNA vaccines, and which factors are responsible for the poor immunogenicity in human so far. Important optimization steps that improve DNA transfection efficiency comprise the introduction of DNA-complexing nano-carriers aimed to prevent extracellular DNA degradation, enabling APC targeting, and enhanced endo/lysosomal escape of DNA. Attachment of virus-derived nuclear localization sequences facilitates nuclear entry of DNA. Improvements in DNA vaccine design include the use of APC-specific promotors for transcriptional targeting, the arrangement of multiple antigen sequences, the co-delivery of molecular adjuvants to prevent tolerance induction, and strategies to circumvent potential inhibitory effects of the vector backbone. Successful clinical use of DNA vaccines may require combined employment of all of these parameters, and combination treatment with additional drugs.