Viral-mimicking protein nanoparticle vaccine for eliciting anti-tumor responses.

The immune system is a powerful resource for the eradication of cancer, but to overcome the low immunogenicity of tumor cells, a sufficiently strong CD8(+) T cell-mediated adaptive immune response is required. Nanoparticulate biomaterials represent a potentially effective delivery system for cancer vaccines, as they can be designed to mimic viruses, which are potent inducers of cellular immunity. We have been exploring the non-viral pyruvate dehydrogenase E2 protein nanoparticle as a biomimetic platform for cancer vaccine delivery. Simultaneous conjugation of a melanoma-associated gp100 epitope and CpG to the E2 nanoparticle (CpG-gp-E2) yielded an antigen-specific increase in the CD8(+) T cell proliferation index and IFN-γ secretion by 1.5-fold and 5-fold, respectively, compared to an unbound peptide and CpG formulation. Remarkably, a single nanoparticle immunization resulted in a 120-fold increase in the frequency of melanoma epitope-specific CD8(+) T cells in draining lymph nodes and a 30-fold increase in the spleen, relative to free peptide with free CpG. Furthermore, in the very aggressive B16 melanoma murine tumor model, prophylactic immunization with CpG-gp-E2 delayed the onset of tumor growth by approximately 5.5 days and increased animal survival time by approximately 40%, compared to PBS-treated animals. These results show that by combining optimal particle size and simultaneous co-delivery of molecular vaccine components, antigen-specific anti-tumor immune responses can be significantly increased.

Oral tolerance and pyruvate dehydrogenase in patients with primary biliary cirrhosis.

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized by the immunological destruction of intralobular bile ducts and serum anti-mitochondrial antibodies (AMA). Based upon previous work of oral tolerance and autoimmunity, we hypothesized that feeding the mitochondrial autoantigens of PBC would alter the clinical course and the level of antimitochondrial antibodies. The bovine pyruvate dehydrogenase complex (PDC) was purified and 5 mg fed in gelatin capsules to 6 patients with early stage PBC for 6 months. Antimitochondrial antibodies and liver biochemistries were measured at every 3 months for 12 months. The clinical trial was completed for all patients except for 1 who showed deterioration of pre-existing skin rash during treatment, which disappeared within 2 weeks after treatment was discontinued. However, after 1 year, neither the titers of AMAs nor liver biochemistries were significantly changed by this treatment. This is the first trial to test the efficacy of oral tolerance induction in PBC. However, the data, which limited in scope, did not demonstrate efficacy and further highlights the difficulties in showing continuing evidence of tolerance induction in autoimmunity.

Autoimmune cholangitis in the SJL/J mouse is antigen non-specific.

Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by intrahepatic bile duct destruction and the production of anti-mitochondrial antibodies (AMA). The absence of an animal model has been a striking impedance in defining the molecular basis of disease. Previous work has suggested that SJL/J mice immunize with the pyruvate dehydrogenase complex (PDC-E2), the major mitochondrial autoantigen of PBC, leads to the development of lymphoid cell infiltration in portal tracts and a model system coined autoimmune cholangitis. We hypothesized that this pathology would be augmented if immunization occurred in the presence of IFN-gamma injections. Accordingly, SJL/J mice were immunized with PDC-E2 and, for purpose of control, alpha-casein. Subgroups of mice were also treated with exogenous IFN-gamma. As expected, mice immunized with PDC-E2, with or without IFN-gamma, developed high titer AMAs. In contrast, mice immunized with alpha-casein, develop antinuclear antibodies. More importantly, the livers from mice immunized with PDC-E2 and/or those immunized with alpha-casein all displayed lymphoid cell infiltration to the portal tracts, irrespective of bile duct size. Indeed, there was no significant difference between the experimental and the control groups by histologic analysis. Thus, autoimmune cholangitis in these mice is antigen non-specific.

Experimental autoimmune cholangitis: a mouse model of immune-mediated cholangiopathy.

BACKGROUND: Primary biliary cirrhosis (PBC) is characterised by intra-hepatic immune-mediated cholangiopathy (non-suppurative destructive cholangitis (NSDC)). Although auto-reactive immune responses against pyruvate dehydrogenase complex (PDC) have been characterised in PBC, the lack of an animal model of the disease has limited study of the mechanisms of disease induction and the development of novel approaches to therapy. AIMS: To develop and validate a mouse model of immune-mediated cholangiopathy relevant for future use in the study of the aetio-pathogenesis and therapy of PBC. METHODS: Female SJL/J, C57BL/6, NOD and BALB/c mice were sensitised with PDC, its purified E2/E3BP component, and a PDC-E2 derived peptide p163 (a dominant T-cell epitope in humans) in complete Freund's adjuvant (CFA). Morphological changes were assessed under light microscopy by a hepatic histopathologist blinded to the experimental details. Antibody responses to PDC were studied by ELISA and PDC inhibition assay. RESULTS: An initial series of experiments was performed to survey the susceptibility of female mice of a range of strains to the induction of NSDC by i.p. sensitisation with PDC, PDC-E2/E3BP or p163 in CFA. Although each animal showed a specific antibody response following sensitisation, it was found that NSDC development (assessed at 30 weeks post-sensitisation) was restricted to SJL/J mice following sensitisation with any of the mitochondrial antigen preparations. A subsequent series of experiments was performed to examine the specificity and aetiology of this disease. Significant bile duct lesions were only seen in SJL/J animals following sensitisation with CFA containing PDC, and were absent from CFA only and un-sensitised controls. Kinetic analysis revealed that this pathology developed slowly, but a high incidence of animals with severe lesions was observed after 30 weeks. CONCLUSIONS: We have described a model of experimental autoimmune cholangitis (EAC) with immunological (anti-PDC antibodies) and histological (immune-mediated cholangiopathy) features suggestive of PBC. This model may be useful in further defining the role of self-tolerance breakdown in the development of this condition.

Analysis of peripheral blood mononuclear cell stimulated with pyruvate dehydrogenase complex, T-cell receptors from patients with primary biliary cirrhosis.

Progressive destruction of the intrahepatic bile ducts in patients with primary biliary cirrhosis (PBC) is thought to be mediated by cytotoxic T cells which recognize certain epitopes, such as the pyruvate dehydrogenase complex (PDC). To clarify the T-cell repertoire in PBC, we analyzed T-cell receptor (TCR) Vbeta-chain messages expressed in peripheral blood mononuclear cells (PBMCs) stimulated with PDC and in liver biopsy specimens. PBMCs from 12 PBC patients and 6 healthy controls were examined. The TCR Vbeta repertoires of unstimulated PBMCs and PBMCs stimulated with PDC purified from bovine heart were analyzed, using the reverse transcriptase-polymerase chain reaction (RT-PCR) and single-strand conformation polymorphism (SSCP). Liver biopsy specimens from 5 PBC patients were also analyzed. In the PBC patients, several different T-cell clones, some of which showed the same mobility, were evident in both the PDC-stimulated and unstimulated PBMCs, as demonstrated by SSCP analysis. In addition, TCR clonality of infiltrating lymphocytes in the liver was also observed in PBC patients, showing common clonal T-cell accumulation with that seen in PBMCs stimulated with PDC. These data indicate that common clonal T-cell accumulation specific for PDC may be present in both peripheral PBMCs and the liver of patients with PBC.