Project description:CD8 T cells from human donors were sorted with peptide-MHC multimers based on SARS-Cov-2 epitopes. For each donor the alpha and beta chains were sequenced separately
Project description:CD4+ T cells orchestrate the adaptive immune response against pathogens and cancer by recognizing epitopes presented on MHC-II molecules. The high polymorphism of MHC-II genes represents an important hurdle towards accurate predictions of CD4+ T-cell epitopes in different individuals and different species. Here we generated and curated a dataset of 627,013 unique MHC-II ligands identified by mass spectrometry. This enabled us to determine the binding motifs of 88 MHC-II alleles across human, mouse, cattle and chicken. Analysis of these binding specificities combined with X-ray crystallography refined our understanding of the molecular determinants of MHC-II motifs and revealed a widespread reverse binding mode in MHC-II ligands. We then developed a machine learning framework to accurately predict binding specificities and ligands of any MHC-II allele. This tool improves and expands predictions of CD4+ T-cell epitopes, as demonstrated by the identification of several viral and bacterial epitopes following the aforementioned reverse binding mode.
Project description:CD8+ T cell immunity to SARS-CoV-2 has been implicated in COVID-19 severity and virus control. Here, we identified non-synonymous mutations in MHC-I restricted CD8+ T cell epitopes after deep sequencing of 747 SARS-CoV-2 virus isolates. Mutant peptides exhibited diminished or abrogated MHC-I binding, which was associated with a loss of recognition and functional responses by CD8+ T cells isolated from HLA-matched COVID-19 patients. Our findings highlight the capacity of SARS-CoV-2 to subvert CD8+ T cell surveillance through sporadically emerging escape mutations in MHC- I restricted viral epitopes.
Project description:Presentation of antigenic peptides by MHCI is central to cellular immune responses against viral pathogens. While adaptive immune responses versus SARS-CoV-2 can be of critical importance to both recovery and vaccine efficacy, how protein antigens from this pathogen are processed inside the cell to generate antigenic peptides is largely unknown. Here, we analyzed the proteolytic processing of 315 overlapping precursor peptides spanning the entire sequence of the S1 spike glycoprotein of SARS-CoV-2, by three key enzymes for the generation ofthat generate antigenic peptides, namely intracellular aminopeptidases ERAP1, ERAP2 and IRAP. Each All enzymes generated shorter peptides with sequences suitable for binding onto HLA alleles, but with marked differences corresponding to distinct specificity fingerprints. ERAP1 was the most efficient in generating peptides 8-11 residues long, the optimal length for HLA binding, while IRAP was the least efficient. The combination of ERAP1 with ERAP2 was largely highly destructive and greatly reduced limited peptides the variability of peptide sequences availableproduced for HLA-binding. Less than 710% of computationally predicted epitopes were found to be produced by enzymatic trimming experimentally, suggesting that proteolytic aminopeptidase processing may constitute a significant filter to successful epitope presentation. These experimentally generated putative epitopes could be prioritized for SARS-CoV-2 immunogenicity studies and vaccine design. We furthermore propose that this in vitro trimming approach could constitute a general filtering method to enhance the prediction robustness of predicting for viral antigenic epitopes.
Project description:CD4 T cells from human donors were sorted with peptide-MHC multimers based on specific epitopes. For each donor the alpha and beta chains were sequenced separately
Project description:Vaccine-induced immunity may impact subsequent de novo responses to drifted epitopes in SARS-CoV-2 variants, but this has been difficult to quantify due to the challenges in recruiting unvaccinated control groups whose first exposure to SARS-CoV-2 is a primary infection . Through local, statewide, and national SARS-CoV-2 testing programs, we were able to recruit cohorts of individuals who had recovered from either primary or post-vaccination infections by either the Delta or Omicron BA.1 variants. Regardless of variant, we observed greater Spike-specific and neutralizing antibody responses in post-vaccination infections than in those who were infected without prior vaccination. Through analysis of variant-specific memory B cells as markers of de novo responses, we observed that Delta and Omicron BA.1 infections led to a marked shift in immunodominance in which some drifted epitopes elicited minimal responses, even in primary infections. Prior immunity through vaccination had a small negative impact on these de novo responses, but this did not correlate with cross-reactive memory B cells, arguing against competitive inhibition of naïve B cells. We conclude that dampened de novo B cell responses against drifted epitopes are mostly a function of altered immunodominance hierarchies that are apparent even in primary infections, with a more modest contribution from pre-existing immunity, perhaps due to accelerated antigen clearance.
Project description:The appended raw files, csv files and other documents were deposited in the public domain in support for the publication "Expanding the MAPPs assay to accommodate MHC-II pan re-ceptors for improved predictability of potential T cell epitopes" by Katharina Hartman, Guido Steiner, Michel Siegel, Cary M. Looney, Timothy P. Hickling, Katharine Bray-French, Sebastian Springer, Celine Marban-Doran and Axel Ducret.
The abstract is as follows: A critical step in the immunogenicity cascade is attributed to human leukocyte antigen (HLA) II presentation triggering T cell immune responses. The liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based major histocompatibility complex (MHC) II-associated peptide proteomics (MAPPs) assay is implemented during preclinical risk assessments to identify bio-therapeutic-derived T cell epitopes. Although studies indicate HLA-DP and HLA-DQ alleles are linked to immunogenicity, most MAPPs studies are restricted to HLA-DR as the dominant HLA II genotype due to lack of well-characterized immunoprecipitating antibodies. Herein we ad-dress this issue by testing various commercially-available clones of MHC-II pan (CR3/43, WR18, and Tu39), HLA-DP (B7/21), and HLA-DQ (SPV-L3 and 1a3) antibodies in the MAPPs assay, and characterizing identified peptides according to binding specificity. Our results reveal that HLA II receptor-precipitating reagents with similar reported specificities differ based on clonality and that MHC-II pan antibodies do not entirely exhibit pan-specific tendencies. Since no individual antibody clone is able to recover the complete HLA II peptide repertoire, we recommend a mixed strategy of clones L243, WR18, and SPV-L3 in a single immunoprecipitation step for more robust compound-specific peptide detection. Ultimately, our optimized MAPPs strategy im-proves the predictability and additional identification of T cell epitopes in immunogenicity risk assessments.
The dataset is divided in two sections, one supporting the figures 1-4, the other one supporting the figure 5-6. The collective data has aslo be used to generate the supplementary tables S1-S9.
Project description:Global containment of COVID-19 still requires accessible and affordable vaccines for low- and middle-income countries (LMICs). Recently approved vaccines provide needed interventions, albeit at prices that may limit their global access. Subunit vaccines based on recombinant proteins are suited for large-volume microbial manufacturing to yield billions of doses annually, minimizing their manufacturing cost. These types of vaccines are well-established, proven interventions with multiple safe and efficacious commercial examples. Many vaccine candidates of this type for SARS-CoV-2 rely on sequences containing the receptor-binding domain (RBD), which mediates viral entry to cells via ACE2. Here we report an engineered sequence variant of RBD that exhibits high-yield manufacturability, high-affinity binding to ACE2, and enhanced immunogenicity after a single dose in mice compared to the Wuhan-Hu-1 variant used in current vaccines. Antibodies raised against the engineered protein exhibited heterotypic binding to the RBD from two recently reported SARS-CoV-2 variants of concern (501Y.V1/V2). Presentation of the engineered RBD on a designed virus-like particle (VLP) also reduced weight loss in hamsters upon viral challenge.
Project description:In this project, we used MS-based immunopeptidomics and T-cell screening assays to identify SARS-CoV-2 epitopes. The MS identified epitopes were further valdiated for CD8 T cell immunogenecity. PBMC from a large number of patients infected with SARS-CoV-2 were used for valdiation of MS identifed and predected CD 8 T cell epotipes.