A clinical trial of a DNA vaccine (SCIB1) that targets dendritic cells in vivo in fully resected melanoma patients; a vaccine to prevent disease recurrence?

Background: SCIB1 is a DNA vaccine encoding a human IgG1 antibody with CDRs that contain four epitopes from two melanoma antigens (three from gp100 and one from TRP2). The vaccine elicits potent anti-tumour responses by stimulating high frequency, high avidity T-cells via both direct and cross-presentation of antibody. A clinical study in stage III/IV melanoma patients, all with tumour present at study entry, showed that 2-8mg doses could induce T-cell responses in 7/9 patients with no associated toxicity. Encouragingly overall survival was 31 months. This study addresses the question as to whether SCIB1 can be used as an adjuvant therapy in fully resected melanoma patients to prevent further disease. Methods: Sixteen patients with fully resected stage III (n=9) or stage IV (n=7) melanoma were immunised with 4mg of SCIB1 by intramuscular electroporation at 3 weekly intervals and subsequently at 3 and 6 months. Patients could continue treatment for 5 years. Results: All 16 patients showed vaccine-epitope-specific T-cell responses (i.e. proliferation ex vivo and/or γIFN Elispot responses in-vitro). Twelve patients responded to all four epitopes, two patients to three epitopes, one to two epitopes and one to a single epitope. Five patients remain in the continuation phase - all show strong T-cell memory responses following boosting. At present, median survival time is 37 months from trial entry and 41.5 months from diagnosis of metastases. Overall survival is 100% for both groups. Five patients relapsed at 1, 4, 14, 17 and 18 months but have shown no further recurrences at follow-up. Conclusion: These results show that a DNA vaccine encoding epitopes from melanoma antigens can induce measurable T-cell responses and, furthermore, it may confer protection from recurrence of melanoma with little associated toxicity. SCIB1 deserves further evaluation as an adjuvant therapy

Oxidative protein folding in bacteria

Ten years ago it was thought that disulphide bond formation in prokaryotes occurred spontaneously. Now two pathways involved in disulphide bond formation have been well characterized, the oxidative pathway, which is responsible for the formation of disulphides, and the isomerization pathway, which shuffles incorrectly formed disulphides. Disulphide bonds are donated directly to unfolded polypeptides by the DsbA protein; DsbA is reoxidized by DsbB. DsbB generates disulphides de novo from oxidized quinones. These quinones are reoxidized by the electron transport chain, showing that disulphide bond formation is actually driven by electron transport. Disulphide isomerization requires that incorrect disulphides be attacked using a reduced catalyst, followed by the redonation of the disulphide, allowing alternative disulphide pairing. Two isomerases exist in Escherichia coli , DsbC and DsbG. The membrane protein DsbD maintains these disulphide isomerases in their reduced and thereby active form. DsbD is kept reduced by cytosolic thioredoxin in an NADPH-dependent reaction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75150/1/j.1365-2958.2002.02851.x.pd

Homocitrullination of lysine residues mediated by myeloid derived suppressor cells in the tumour environment is a target for cancer immunotherapy

Background: Homocitrullination is the post translational modification of lysine that is recognized by T cells. Methods: This study identified homocitrullinated peptides from aldolase, enolase, cytokeratin and Bip and used HLA transgenic mice to assess immunogenicity by ELISpot assay. Vaccine efficacy was assessed in tumour therapy studies using HLA matched B16 melanoma expressing constitutive or IFNγ inducible MHC-II as represented by most human tumours. To determine the mechanism behind the therapy, immune cell infiltrates were analysed using flow cytometry and therapy studies in the presence of MPO inhibitor and T cell depletion performed. We assessed the T cell repertoire to homocitrullinated peptides in cancer patients and healthy donors using flow cytometry. Results: Homocitrulline peptide vaccination stimulated strong CD4 T cell responses and induced significant anti-tumour therapy in an established tumour model. The anti-tumour response was dependent upon CD4 T-cells and the effect was driven mainly via direct tumour recognition, as responses were only observed if the tumours were induced to express MHC-II. In vitro proliferation assays show that healthy donors and cancer patients have an oligoclonal CD4 T-cell repertoire recognizing homocitrullinated peptides. Inhibition of cyanate generation, which mediates homocitrullination, by myeloperoxidase (MPO) inhibition reduced tumour therapy by the vaccine induced T cells (P=0.0018). Analysis of the tumour microenvironment (TME) suggested that myeloid-derived suppressor cells (MDSCs) were a potential source of MPO. The selected B16 melanoma model showed MDSC infiltration. and was appropriate to see if the homocitrulline vaccine could overcome the immunosuppression associated with MDSCs. The vaccine was very effective (90% survival) as the induced CD4 T cells directly targeted the homocitrullinated tumour and likely reversed the immunosuppressive environment. Conclusion: We propose that MPO, potentially produced by MDSCs, catalyses the build-up of cyanate in the TME which diffuses into tumour cells causing homocitrullination of cytoplasmic proteins which are degraded and, in the presence of IFNγ, presented by MHC-II for direct CD4 T-cell recognition. Homocitrullinated proteins are a new target for cancer vaccines and may be particularly effective against tumours containing high levels of MPO expressing MDSCs

State of the world’s plants and fungi 2020

Kew’s State of the World’s Plants and Fungi project provides assessments of our current knowledge of the diversity of plants and fungi on Earth, the global threats that they face, and the policies to safeguard them. Produced in conjunction with an international scientific symposium, Kew’s State of the World’s Plants and Fungi sets an important international standard from which we can annually track trends in the global status of plant and fungal diversity