Theiler's Murine Encephalomyelitis Virus as a Vaccine Candidate for Immunotherapy

The induction of sterilizing T-cell responses to tumors is a major goal in the development of T-cell vaccines for treating cancer. Although specific components of anti-viral CD8+ immunity are well characterized, we still lack the ability to mimic viral CD8+ T-cell responses in therapeutic settings for treating cancers. Infection with the picornavirus Theiler's murine encephalomyelitis virus (TMEV) induces a strong sterilizing CD8+ T-cell response. In the absence of sterilizing immunity, the virus causes a persistent infection. We capitalized on the ability of TMEV to induce strong cellular immunity even under conditions of immune deficiency by modifying the virus to evaluate its potential as a T-cell vaccine. The introduction of defined CD8+ T-cell epitopes into the leader sequence of the TMEV genome generates an attenuated vaccine strain that can efficiently drive CD8+ T-cell responses to the targeted antigen. This virus activates T-cells in a manner that is capable of inducing targeted tissue damage and glucose dysregulation in an adoptive T-cell transfer model of diabetes mellitus. As a therapeutic vaccine for the treatment of established melanoma, epitope-modified TMEV can induce strong cytotoxic T-cell responses and promote infiltration of the T-cells into established tumors, ultimately leading to a delay in tumor growth and improved survival of vaccinated animals. We propose that epitope-modified TMEV is an excellent candidate for further development as a human T-cell vaccine for use in immunotherapy

Anatomical and Cellular Requirements for the Activation and Migration of Virus-Specific CD8(+) T Cells to the Brain during Theiler's Virus Infection

Theiler's murine encephalomyelitis virus (TMEV) infection of the brain induces a virus-specific CD8(+) T-cell response in genetically resistant mice. The peak of the immune response to the virus occurs 7 days after infection, with an immunodominant CD8(+) T-cell response against a VP2-derived capsid peptide in the context of the D(b) molecule. The process of activation of antigen-specific T cells that migrate to the brain in the TMEV model has not been defined. The site of antigenic challenge in the TMEV model is directly into the brain parenchyma, a site that is considered immune privileged. We investigated the hypothesis that antiviral CD8(+) T-cell responses are initiated in situ upon intracranial inoculation with TMEV. To determine whether a brain parenchymal antigen-presenting cell is responsible for the activation of virus-specific CD8(+) T cells, we evaluated the CD8(+) T-cell response to the VP2 peptide in bone marrow chimeras and mutant mice lacking peripheral lymphoid organs. The generation of the anti-TMEV CD8(+) T-cell response in the brain requires priming by a bone marrow-derived antigen-presenting cell and the presence of peripheral lymphoid organs. Although our results show that activation of TMEV-specific CD8(+) T cells occurs in the peripheral lymphoid compartment, they do not exclude the possibility that the immune response to TMEV is initiated by a brain-resident, bone marrow-derived, antigen-presenting cell

Thymus leukemia antigen controls intraepithelial lymphocyte function and inflammatory bowel disease

Intestinal intraepithelial lymphocytes (IEL) bear a partially activated phenotype that permits them to rapidly respond to antigenic insults. However, this phenotype also implies that IEL must be highly controlled to prevent misdirected immune reactions. It has been suggested that IEL are regulated through the interaction of the CD8αα homodimer with the thymus leukemia (TL) antigen expressed by intestinal epithelial cells. We have generated and characterized mice genetically-deficient in TL expression. Our findings show that TL expression has a critical role in maintaining IEL effector functions. Also, TL deficiency accelerated colitis in a genetic model of inflammatory bowel disease. These findings reveal an important regulatory role of TL in controlling IEL function and intestinal inflammation

Mycophenolate mofetil but not atorvastatin attenuates atherosclerosis in lupus-prone LDLr-/- mice

Rationale Recent clinical and preclinical studies have demonstrated that systemic lupus erythematosus (SLE) is associated with an increased risk for cardiovascular disease (CVD). However, unlike in the general population, little is known regarding the efficacy of atheroprotective interventions in patients with SLE. The current study aims to determine the benefit of lymphocyte inhibition on reducing the atherosclerotic burden in SLE-susceptible LDLr-deficient mice. Methods Female LDLr-/- mice were lethally irradiated and reconstituted with bone marrow from C57Bl/6 mice (LDLr.B6) or the SLE-susceptible B6.Sle1.2.3 mice (LDLr.Sle). At 16 weeks post transplant, mice were treated with atorvastatin (10 mg/kg), mycophenolate mofetil (MMF; 40 mg/kg), or both (MMF-A) for 8 weeks, after which the extent of atherosclerosis and the presence of SLE were assessed. Results Following 8 weeks of treatment, we observed that atorvastatin-mediated reduction in cholesterol levels attenuated atherogenesis in LDLr.B6 mice but failed to significantly reduce atherosclerotic lesion size in LDLr.Sle mice, in spite of a significant reduction in serum cholesterol levels. Treatment with MMF and MMF-A attenuated atherogenesis in LDLr.B6 and LDLr.Sle mice. In addition, MMF-containing regimens inhibited recruitment of CD4+ T cells to atherosclerotic lesions in LDLr.Sle mice. In these mice, MMF also reduced the proportion of activated splenic T cells, as well as interleukin 10 secretion by T cells. With regard to lupus activity, MMF had no overt effect on anti-double-stranded DNA (dsDNA) antibody titres or kidney function and pathology. Conclusions The current study demonstrates that reduction of cholesterol levels alone is not atheroprotective in lupus-mediated atherogenesis. This is the first study to demonstrate that MMF reduces the atherosclerotic burden in a model of lupus-accelerated atherosclerosis. Our results suggest that MMF treatment may prove beneficial in preventing CVD in patients with SL

Activation of invariant natural killer T cells by lipid excess promotes tissue inflammation, insulin resistance, and hepatic steatosis in obese mice

Obesity triggers a low-grade systemic inflammation, which plays an important role in the development of obesity-associated metabolic diseases. In searching for links between lipid accumulation and chronic inflammation, we examined invariant natural killer T (iNKT) cells, a subset of T lymphocytes that react with lipids and regulate inflammatory responses. We show that iNKT cells respond to dietary lipid excess and become activated before or at the time of tissue recruitment of inflammatory leukocytes, and that these cells progressively increase proinflammatory cytokine production in obese mice. Such iNKT cells skew other leukocytes toward proinflammatory cytokine production and induce an imbalanced proinflammatory cytokine environment in multiple tissues. Further, iNKT cell deficiency ameliorates tissue inflammation and provides protection against obesity-induced insulin resistance and hepatic steatosis. Conversely, chronic iNKT cell stimulation using a canonical iNKT cell agonist exacerbates tissue inflammation and obesity-associated metabolic disease. These findings place iNKT cells into the complex network linking lipid excess to inflammation in obesity and suggest new therapeutic avenues for obesity-associated metabolic disorders

Generation of epitope specific CD8+ T-cell responses with TMEV-L/OVA.

<p>(A) FACS analysis of brain infiltrating lymphocytes (BIL) from mice infected with TMEV-L/OVA for 6 days. The proportion of OVA₂₅₇ specific T-cells increases in the absence of viral specific CD8+ T-cells (p<0.001). (B) In vitro cytotoxic activity of BIL as measured by a 4 hour chromium release assay using VP2₁₂₁ and OVA₂₅₇ peptide pulsed targets. (C) OVA₂₅₇ specific in vivo killing of labeled target cells in 6 day TMEV-L/OVA infected mice was increased compared to TMEV-wt (p = <0.001).</p

Induction of diabetes with TMEV-L/OVA using RIP-OVA mice given OT-1 T-cell transfer.

<p>Representative pancreatic islets from RIP-OVA mice given TMEV-wt (A) or TMEV-L/OVA (B) without OT-1 transfer. (C) Pancreatic islet infiltration observed in OT-1 transferred RIP-OVA receiving TMEV-L/OVA vaccine compared to TMEV-wt vaccine (D). (E) Blood glucose levels observed in RIP-OVA mice given TMEV-wt or TMEV-L/OVA vaccines. Increased blood glucose was observed on day 6 (p = 0.007), 7 (p<0.001), 8 (p<0.001) and 9 (p<0.001) in mice receiving both OT-1 transfer and TMEV-L/OVA vaccine compared to transfer with TMEV-wt.</p