Project description:Hepatitis Delta virus (HDV) is a satellite of Hepatitis B virus with a single stranded circular RNA genome. HDV RNA genome synthesis is carried out in infected cells by cellular RNA polymerases with the assistance of the small hepatitis delta antigen (S-HDAg). Here we show that S-HDAg binds the Bromodomain (BRD) Adjacent To Zinc Finger Domain 2B (BAZ2B) protein, a regulatory subunit of BRF (BAZ2B-Associated Remodeling Factor) ISWI chromatin remodeling complexes. ShRNAs-mediated silencing of BAZ2B or its inactivation with the BAZ2B-BRD inhibitor GSK-2801 impairs HDV replication in HDV-infected human hepatocytes. S-HDAg contains a short linear interacting motif (SLiM) KacXXR, similar to the one recognized by BAZ2B-BRD in histone H3. We found that the integrity of the S-HDAg SLiM sequence is required for S-HDAg interaction with BAZ2B-BRD and for HDV RNA replication. Our results suggest that S-HDAg uses a histone mimicry strategy to co-activate the RNA Polymerase II-dependent synthesis of HDV RNA and sustain HDV replication.
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:Human CD8+ T cells are the final mediators of autoimmune β-cell destruction in type 1 diabetes. However, their target epitopes have not been demonstrated to be naturally processed and presented by β cells. We therefore performed an epitope discovery study combining HLA Class I peptidomics and transcriptomics strategies. Inflammatory cytokines increased β-cell peptide presentation in vitro, paralleling upregulation of HLA Class I expression. Peptide sources included known β-cell antigens and several insulin granule proteins. Preproinsulin yielded multiple previously described HLA-A2-restricted epitopes. Secretogranin V (SCG5/7B2), proconvertase-2, urocortin-3 and the insulin gene enhancer protein ISL-1 were identified as novel β-cell antigens, which were processed into HLA-A2-restricted epitopes recognized by circulating naïve CD8+ T cells in type 1 diabetic and healthy donors. HLA-A2-bound neo-epitopes were also represented and originated from an alternative mRNA splice isoform (SCG5-009) and from an islet amyloid polypeptide transpeptidation product. This first description of the β-cell HLA peptidome opens new avenues to understand the antigen processing pathways employed by β cells and provides a valuable tool for developing T-cell biomarkers and tolerogenic vaccination strategies.
Project description:The presentation of virus-derived peptides by HLA class I molecules on the surface of an infected cell and the recognition of these HLA-peptide complexes by, and subsequent activation of, CD8+ cytotoxic T cells provides an important mechanism for immune protection against viruses. Recent advances in proteogenomics have allowed researchers to discover a growing number of unique HLA-restricted viral peptides, resulting in a rapidly expanding repertoire of targets for immunotherapeutics (i.e. bispecific antibodies, engineered T-cell receptors (TCRs), chimeric antigen receptor T-cells (CAR-Ts)) to infected tissues. However, genomic variability between viral strains, such as Hepatitis-B virus (HBV), in combination with differences in patient HLA alleles, make it difficult to develop therapeutics against these targets. To address this challenge, we developed a novel proteogenomics approach for generating patient-specific databases that enable the identification of viral peptides based on the viral transcriptomes sequenced from individual patient liver samples. We also utilized DNA sequencing of patient samples to identify HLA genotypes and assist in target selection. Liver samples from 48 HBV infected patients, primarily from Asia, were examined to reconstruct patient-specific HBV genomes, identify regions within the human chromosomes targeted by HBV integrations and obtain a comprehensive view of HBV peptide epitopes using our HLA class-I (HLA-I) immunopeptidomics discovery platform. Two previously reported HLA associated HBV-derived peptides, HLA-A02 binder FLLTRILTI (S194-202) from the large surface antigen and HLA-A11 binder STLPETTVVRR (C141-151) from the capsid protein were validated by our discovery platform, but both were detected at a very low frequencies. In addition, we identified and validated, using heavy peptide analogues, novel strain-specific HBV-HLA associated peptides, such as GSLPQEHIVQK (P606-616) and variants. Overall, our novel approach can guide the development of bispecific antibody, TCR-T, or CAR-T based therapeutics for the treatment of HBV-related HCC and inform vaccine development.
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:Twenty-one pheromone-induced genes were selected from the literature (Zhao, Daniels et al. 2005 was the major source) as the reference set for assessing the pheromone response of CAI4 (Wild-type), cpp1Δ/Δ, cek1Δ/Δ, cek2Δ/Δ, cpp1Δ/Δ cek1Δ/Δ, cpp1Δ/Δ cek2Δ/Δ and cek1Δ/Δ cek2Δ/Δ strains.Our aim was to check whether or not these 21 pheromone-induced genes are up-regulated in response to pheromone in each mutant strain.