Immunosurveillance by cytotoxic T cells requires that cells generate a diverse spectrum of peptides for presentation by major histocompatibility complex (MHC) class I molecules. Those peptides are generated by proteolysis, which begins in the cytoplasm and continues in the endoplasmic reticulum by the unique aminopeptidase ERAAP. The overall extent to which trimming by ERAAP modifies the peptide pool and the immunological consequences of ERAAP deficiency are unknown. Here we show that the peptide-MHC repertoire of ERAAP-deficient mice was missing many peptides. Furthermore, ERAAP-deficient cells presented many unstable and structurally unique peptide-MHC complexes, which elicited potent CD8+ T cell and B cell responses. Thus, ERAAP is a 'quintessential editor' of the peptide-MHC repertoire and, paradoxically, its absence enhances immunogenicity.

Intracellular aminopeptidases endoplasmic reticulum aminopeptidases 1 and 2 (ERAP1 and ERAP2), and as well as insulin-regulated aminopeptidase (IRAP) process antigenic epitope precursors for loading onto MHC class I molecules and regulate the adaptive immune response. Their activity greatly affects the antigenic peptide repertoire presented to cytotoxic T lymphocytes and as a result can regulate cytotoxic cellular responses contributing to autoimmunity or immune evasion by viruses and cancer cells. Therefore, pharmacological regulation of their activity is a promising avenue for modulating the adaptive immune response with possible applications in controlling autoimmunity, in boosting immune responses to pathogens, and in cancer immunotherapy. In this study we exploited recent structural and biochemical analysis of ERAP1 and ERAP2 to design and develop phosphinic pseudopeptide transition state analogs that can inhibit this family of enzymes with nM affinity. X-ray crystallographic analysis of one such inhibitor in complex with ERAP2 validated our design, revealing a canonical mode of binding in the active site of the enzyme, and highlighted the importance of the S2' pocket for achieving inhibitor potency. Antigen processing and presentation assays in HeLa and murine colon carcinoma (CT26) cells showed that these inhibitors induce increased cell-surface antigen presentation of transfected and endogenous antigens and enhance cytotoxic T-cell responses, indicating that these enzymes primarily destroy epitopes in those systems. This class of inhibitors constitutes a promising tool for controlling the cellular adaptive immune response in humans by modulating the antigen processing and presentation pathway. molecular structure | adaptive immunity | major histocompatibility molecules | specificity | kinetics

The aminopeptidase, ERAP1, trims peptides for MHC class I presentation, influencing the degree and specificity of CD8+ T cell responses. Single nucleotide polymorphisms (SNP) within the exons encoding ERAP1 are associated with autoimmune diseases and cervical carcinoma, but it is not known whether they act independently or as disease-associated haplotypes. We sequenced ERAP1 from 20 individuals and show that SNP occur as distinct haplotypes in the human population, and that these haplotypes encode functionally distinct ERAP1 alleles. Using a wide range of substrates, we are able to demonstrate that for any given substrate, distinct ERAP1 alleles can have “normal”, “hypo-”, or “hyper-” functional; and that each allele has a trend bias towards one of these three activities. Thus, the repertoire of peptides presented at the cell surface for recognition by CTL is likely to depend on the precise combination of both MHC class I and ERAP1 alleles expressed within an individual, and has important implications for predisposition to disease.

Activating the immune system to trigger a specific response is a major challenge in vaccine development. In particular, activating sufficient cytotoxic T lymphocyte-mediated cellular immunity, which is crucial for the treatment of many diseases including cancer and AIDS, has proven to be especially challenging. In this study, antigens were encapsulated in acid-degradable polymeric particle carriers to cascade cytotoxic T lymphocyte activation. To target dendritic cells, the most potent antigen-presenting cells, the particle carriers, were further conjugated with monoclonal antibodies. A series of ex vivo and in vivo studies have shown increased receptor-mediated uptake of antibody-conjugated particles by dendritic cells as well as migration of particle-carrying dendritic cells to lymph nodes and stimulation of naïve T cells leading to enhanced cellular immune response as confirmed by specific cell lysis and IFN-␥ secretion.acid-degradable particle ͉ drug delivery ͉ targeted vaccine

For more than 40 y, expression of HLA-B27 has been strongly associated with the chronic inflammatory disease Ankylosing Spondylitis (AS); however, the mechanisms underlying this association are still unknown. Single nucleotide polymorphisms within the aminopeptidase endoplasmic reticulum aminopeptidase 1 (ERAP1), which is essential for trimming peptides before they are presented to T cells by major histocompatibility complex (MHC) class I molecules, have been linked with disease. We show that ERAP1 is a highly polymorphic molecule comprising allotypes of single nucleotide polymorphisms. The prevalence of specific ERAP1 allotypes is different between AS cases and controls. Both chromosomal copies of ERAP1 are codominantly expressed, and analysis of allotype pairs provided clear stratification of individuals with AS versus controls. Functional analyses demonstrated that ERAP1 allotype pairs seen in AS cases were poor at generating optimal peptide ligands for binding to murine H-2K b and -D b and the AS-associated HLA-B*2705. We therefore provide strong evidence that polymorphic ERAP1 alters protein function predisposing an individual to AS via its influence on the antigen processing pathway.

When nonprofit organizations operate in a field of service that might otherwise be provided by government or by for-profit organizations, such as schools, hospitals, or museums, their decisions on the type and amount of services to be delivered are motivated by factors that are quite distinctive. Because they must operate on a break-even basis with revenues raised on a voluntary basis, nonprofit organizations typically take on activities from which they derive no satisfaction in order to subsidize activities that they regard as of higher value. As a result, the mix of services they offer and the charges they impose will generally be quite different from those of a government institution or a for-profit organization.

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SummaryThe MHC class I and II antigen processing and presentation pathways display peptides to circulating CD8 + cytotoxic and CD4 + helper T cells respectively to enable pathogens and transformed cells to be identified. Once detected, T cells become activated and either directly kill the infected / transformed cells (CD8 + cytotoxic T lymphocytes) or orchestrate the activation of the adaptive immune response (CD4 + T cells). The immune surveillance of transformed/tumour cells drives alteration of the antigen processing and presentation pathways to evade detection and hence the immune response. Evasion of the immune response is a significant event tumour development and considered one of the hallmarks of cancer. To avoid immune recognition, tumours employ a multitude of strategies with most resulting in a down-regulation of the MHC class I expression at the cell surface, significantly impairing the ability of CD8 + cytotoxic T lymphocytes to recognize the tumour. Alteration of the expression of key players in antigen processing not only affects MHC class I expression but also significantly alters the repertoire of peptides being presented. These modified peptide repertoires may serve to further reduce the presentation of tumour-specific/associated antigenic epitopes to aid immune evasion and tumour progression. Here we review the modifications to the antigen processing and presentation pathway in tumours and how it affects the anti-tumour immune response, considering the role of tumour-infiltrating cell populations and highlighting possible future therapeutic targets.