Suppression of murine experimental autoimmune encephalomyelitis by interleukin-2 receptor targeted fusion toxin, DAB389IL-2

DAB389IL-2 recombinant fusion toxin effect on lymphocyte- and macrophage-producing cytokine subpopulation cells in experimentally induced demyelinating disease in mice

CONTEXT

We have reported previously that DAB389IL-2 recombinant fusion toxin targets IL-2R bearing CD4⁺ cells, and suppresses demyelinating disease in acute (A) - and chronic (C) - experimental autoimmune encephalomyelitis (EAE) animal models of multiple sclerosis.

OBJECTIVES

The present study was undertaken to investigate the effect of DAB389IL-2 treatment on various cytokine-secreting cell populations in A-EAE and C-EAE mice.

MATERIALS AND METHODS

The effects of DAB389IL-2 at doses of 200-, 800-, or 1600 kU administered i.v. on days 11-13 and 15 on the clinical score and cytokine-secreting cell populations were examined using flow cytometry.

RESULTS

C-EAE mice treated with 1600kU DAB389IL-2, but not A-EAE mice treated with 800 kU had significantly reduced disease. The CD3+CD25+ sub-population in spleens and spinal cords of A-EAE mice treated with 800 kU DAB389IL-2 a was increased, whereas in C-EAE mice treated with 1600 kU this population was increased. DAB₃₈₉IL-2 treatment reduced CD3⁺CD4⁺, CD3⁺CD8⁺, CD4⁺CD8⁺, CD3⁺IL-2⁺, CD3⁺IFN-γ⁺ and CD3⁺TNF-α⁺ T cell subpopulations in the spinal cord in A-EAE, and C-EAE mice on day 16. CD11b+ macrophages that were IL-2-, IFN-γ-, and TNF-α- positive were reduced in A-EAE mice. DAB389IL-2 treatment reduced CD19⁺ B-cells positive for IL-2 or CD11b⁺ in the spinal cord in acute and chronic disease. DAB389IL-2 treatment also reduced lymph node CD3⁺CD8⁺, CD4⁺CD8⁺, CD3⁺CD25⁺ populations on day 16, and lymph node CD3⁺IL-10⁺ and peripheral blood CD3⁺CD25⁺ populations on day 24.

DISCUSSION AND CONCLUSIONS

Our study demonstrates that DAB₃₈₉IL-2 fusion toxin suppresses EAE in a dose-dependent manner, and alters inflammatory cell sub-populations during disease development.

Bacterial toxin's DNA vaccine serves as a strategy for the treatment of cancer, infectious and autoimmune diseases

DNA vaccination -a third generation vaccine-is a modern approach to stimulate humoral and cellular responses against different diseases such as infectious diseases, cancer and autoimmunity. These vaccines are composed of a gene that encodes sequences of a desired protein under control of a proper (eukaryotic or viral) promoter. Immune response following DNA vaccination is influenced by the route and the dose of injection. In addition, antigen presentation following DNA administration has three different mechanisms including antigen presentation by transfected myocytes, transfection of professional antigen presenting cells (APCs) and cross priming. Recently, it has been shown that bacterial toxins and their components can stimulate and enhance immune responses in experimental models. A study demonstrated that DNA fusion vaccine encoding the first domain (DOM) of the Fragment C (FrC) of tetanus neurotoxin (CTN) coupled with tumor antigen sequences is highly immunogenic against colon carcinoma. DNA toxin vaccines against infectious and autoimmune diseases are less studied until now. All in all, this novel approach has shown encouraging results in animal models, but it has to go through adequate clinical trials to ensure its effectiveness in human. However, it has been proven that these vaccines are safe, multifaceted and simple and can be used widely in organisms which may be of advantage to public health in the near future. This paper outlines the mechanism of the action of DNA vaccines and their possible application for targeting infectious diseases, cancer and autoimmunity.

Emerging immunopharmacological targets in multiple sclerosis

Inflammatory demyelination of the central nervous system (CNS) is the hallmark of multiple sclerosis (MS), a chronic debilitating disease that affects more than 2.5 million individuals worldwide. It has been widely accepted, although not proven, that the major pathogenic mechanism of MS involves myelin-reactive T cell activation in the periphery and migration into the CNS, which subsequently triggers an inflammatory cascade that leads to demyelination and axonal damage. Virtually all MS medications now in use target the immune system and prevent tissue damage by modulating neuroinflammatory processes. Although current therapies such as commonly prescribed disease-modifying medications decrease the relapse rate in relapsing-remitting MS (RRMS), the prevention of long-term accumulation of deficits remains a challenge. Medications used for progressive forms of MS also have limited efficacy. The need for therapies that are effective against disease progression continues to drive the search for novel pharmacological targets. In recent years, due to a better understanding of MS immunopathogenesis, new approaches have been introduced that more specifically target autoreactive immune cells and their products, thus increasing specificity and efficacy, while reducing potential side effects such as global immunosuppression. In this review we describe several immunopharmacological targets that are currently being explored for MS therapy.

Apotransferrin inhibits interleukin-2 expression and protects mice from experimental autoimmune encephalomyelitis

Transferrin (Tf) has a major role in T cell activation and proliferation. Here, we investigated whether Tf exerts immunomodulatory effects on T cells and in development of T-cell driven experimental autoimmune encephalomyelitis (EAE). While treatment of concanavalin A-stimulated splenocytes with apotransferrin (ApoTf) did not affect release of IL-1β, TNF, IFN-γ, IL-17, IL-4, and IL-10, it markedly and dose-dependently down-regulated synthesis of IL-2 in these cells. ApoTf also inhibited IL-2 generation in purified CD3+ T cells and the effect was accompanied with down-regulation of MAPK p44/42 and NFκB signaling. Despite impeded IL-2 release, proliferation of splenocytes was not inhibited by ApoTf. Importantly, ApoTf ameliorated EAE in mice and significantly reduced ex vivo IL-2 production in proteolipid protein-specific lymphocytes. Thus ApoTf may be a promising beneficial agent for multiple sclerosis.

The IL-2 diphtheria toxin fusion protein denileukin diftitox modulates the onset of diabetes in female nonobese diabetic animals in a time-dependent manner and breaks tolerance in male nonobese diabetic animals

Denileukin diftitox, also known as DAB(389)IL-2 or Ontak, is a fusion protein toxin consisting of the full-length sequence of the IL-2 protein and as toxophore the truncated diphtheria toxin. As a consequence, it delivers the toxic agent to CD25-bearing cells, whereby CD25 represents the high-affinity α-subunit of the IL-2 receptor. Initially it was developed for the treatment of patients with cutaneous T cell lymphoma. Meanwhile, denileukin diftitox is also used as an adjuvant in other tumor therapies and neoplastic disorders. In this study, to our knowledge we report for the first time that denileukin diftitox has also dramatic effects regarding the pathology of type 1 diabetes using the NOD mouse model. Repeated injections of denileukin diftitox into female NOD mice at 12 wk of age led to a clear acceleration of disease onset, whereas injection at 7 wk of age did not. Using male NOD mice, which are much less susceptible to diabetes, we demonstrate that the injection of denileukin diftitox leads to a dramatic development of type 1 diabetes within days after injection, thereby obviously breaking pre-existing tolerance mechanisms. This is accompanied by an increased IFN-γ production of autoreactive splenic cells and a decreased presence of regulatory CD4(+)CD25(+)Foxp3(+) T cells. In contrast, transfer of CD4(+)CD25(+)Foxp3(+) T cells could correct the defect after denileukin diftitox treatment. Furthermore, whereas IFN-γ production was increased in the pancreata of treated animals, insulin expression was strongly reduced. These finding should be considered when denileukin diftitox is used for the treatment of patients suffering from tumors and/or autoimmune disorders.