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Use of an alternative open reading frame, potentially as a result of cellular stress, drives production of an unconventional insulin epitope that is recognized by cytotoxic T cells from individuals with type 1 diabetes; these T cells kill beta cells in vitro . Identification of epitopes that are recognized by diabetogenic T cells and cause selective beta cell destruction in type 1 diabetes (T1D) has focused on peptides originating from native beta cell proteins. Translational errors represent a major potential source of antigenic peptides to which central immune tolerance is lacking 1 , 2 . Here, we describe an alternative open reading frame within human insulin mRNA encoding a highly immunogenic polypeptide that is targeted by T cells in T1D patients. We show that cytotoxic T cells directed against the N-terminal peptide of this nonconventional product are present in the circulation of individuals diagnosed with T1D, and we provide direct evidence that such CD8 + T cells are capable of killing human beta cells and thereby may be diabetogenic. This study reveals a new source of nonconventional polypeptides that act as self-epitopes in clinical autoimmune disease.

Oncolytic adenovirus therapy is believed to be a promising way to treat cancer patients. To be able to target tumor cells with an oncolytic adenovirus, expression of the adenovirus receptor on the tumor cell is essential. Different adenovirus types bind to different receptors on the cell, of which the expression can vary between tumor types. Pre-existing neutralizing immunity to human adenovirus species C type 5 (HAdV-C5) has hampered its therapeutic efficacy in clinical trials, hence several adenoviral vectors from different species are currently being developed as a means to evade pre-existing immunity. Therefore, knowledge on the expression of appropriate adenovirus receptors on tumor cells is important. This could aid in determining which tumor types would benefit most from treatment with a certain oncolytic adenovirus type. This review provides an overview of the known receptors for human adenoviruses and how their expression on tumor cells might be differentially regulated compared to healthy tissue, before and after standardized anticancer treatments. Mechanisms behind the up- or downregulation of adenovirus receptor expression are discussed, which could be used to find new targets for combination therapy to enhance the efficacy of oncolytic adenovirus therapy. Additionally, the utility of the adenovirus receptors in oncolytic virotherapy is examined, including their role in viral spread, which might even surpass their function as primary entry receptors. Finally, future directions are offered regarding the selection of adenovirus types to be used in oncolytic adenovirus therapy in the fight against cancer.

Selector adeno-associated viral (AAV) vectors are introduced for retrieving genetically engineered cells, requiring neither heterologous marker chromosomal insertions nor surrogate reporter gene expression systems.Ouabain is a plant-derived cardiac glycoside that inhibits the sodium/potassium (Na+/K+)-ATPase pump. Selector AAV vectors coupled with ouabain treatment enrich for precisely targeted gene knock-ins.Selector AAV vectors coupled with ouabain treatment foster the elimination of off-target exogenous donor DNA insertions from genetically engineered cell populations.In-linkage selector AAV vectors coupled with ouabain treatment yield engineered cell populations with high purity levels of precisely edited cells in a vector dose-independent manner.In trans selector AAV vectors coupled with ouabain treatment permit single-step multiplexing gene knock-ins in hard-to-transfect cells, facilitating complex cell engineering efforts in said cells. Adeno-associated viral (AAV) vectors are commonly used for genome editing owing to the proclivity with which their single-stranded genomes serve as homologous recombination (donor) substrates during programmable nuclease-assisted gene targeting. However, the highly recombinogenic nature of AAV genomes also facilitates their nonhomologous end joining at off-target chromosomal breaks (‘capture’) created by said nucleases, mutagens, or DNA metabolic processes. Moreover, AAV donor constructs can equally yield imprecise on-target edits resulting from end-joining recombination pathways. Here, we demonstrate that endowing AAV vectors with exogenous marker-free selectable sequences permits enrichment for cells precisely coedited at endogenous target and ATP1A1 alleles. These selector AAV vectors install ATP1A1 polymorphisms conferring resistance to the small molecule ouabain, yielding high frequencies of on-target and precisely edited cell populations. Crucially, we further report that selector AAV vectors achieve a thorough removal of heterogeneous off-target DNA species resulting from conventional AAV-based genome editing procedures. [Display omitted] The combined effects of enrichment for cells with precisely targeted gene knock-ins with the purging of cells with off-target donor DNA insertions support the adoption of ouabain-based selector adeno-associated viral (AAV) vector systems in basic research and biotechnological settings. In particular, selector AAV vector systems with in cis, in trans, and in-linkage designs form an enabling combinatorial delivery-selection platform that is most readily applicable to in vitro or ex vivo modification of mammalian cells, especially those that are refractory to chemical and physical donor transfections. Indeed, the high cytotoxicity of ouabain is expected to narrow its operational doses in the context of in vivo settings, rendering its application to these settings difficult. For applications that exclusively involve selection in cell culture systems, including transplantation of ex vivo–engineered cell products, the selector AAV–CRISPR platform is at Technology Readiness Level 4 in that it has been effectively used under controlled laboratory conditions for targeted safe harbor gene knock-ins, endogenous gene tagging, and multiplexed gene knock-ins. For applications that include in vivo selection of engineered cells, further developments are required, e.g., identification of compounds displaying wider effective dose windows than that of ouabain. In addition to the limitations associated with the use of ouabain in vivo, direct administration of selector AAV–CRISPR vectors in vivo is hindered by the lack of HR factors in postmitotic cells and tissues. Finally, in common with ‘classic’ AAV-based gene supplementation therapies, application of selector AAV vectors in therapeutic contexts will profit from improving good manufacturing practice (GMP)-grade upscaling and downstream processing of AAV vector batches to maximize cost-effectiveness and product quality, respectively. Cost-effectiveness will improve by establishing more robust transfection-independent AAV production methods, while product quality will increase by implementing downstream processes yielding thorough removal of empty and partially filled AAV particles from the final drug substance. This study establishes selector adeno-associated viral (AAV) vectors for the targeted and precise installation of chromosomal gene-sized edits. The incorporation of a marker-free co-selection system based on a cheap small molecule permits selector AAV vectors to, next to fostering targeted DNA editing, purge off-target chromosomal insertions, improving the quality of engineered cell products.

Enhancing the intracellular delivery and performance of RNA-guided CRISPR-Cas9 nucleases (RGNs) remains in demand. Here, we show that nuclear translocation of commonly used Streptococcus pyogenes Cas9 (SpCas9) proteins is suboptimal. Hence, we generated eCas9.4NLS by endowing the high-specificity eSpCas9(1.1) nuclease (eCas9.2NLS) with additional nuclear localization signals (NLSs). We demonstrate that eCas9.4NLS coupled to prototypic or optimized guide RNAs achieves efficient targeted DNA cleavage and probe the performance of SpCas9 proteins with different NLS compositions at target sequences embedded in heterochromatin versus euchromatin. Moreover, after adenoviral vector (AdV)-mediated transfer of SpCas9 expression units, unbiased quantitative immunofluorescence microscopy revealed 2.3-fold higher eCas9.4NLS nuclear enrichment levels than those observed for high-specificity eCas9.2NLS. This improved nuclear translocation yielded in turn robust gene editing after nonhomologous end joining repair of targeted double-stranded DNA breaks. In particular, AdV delivery of eCas9.4NLS into muscle progenitor cells resulted in significantly higher editing frequencies at defective DMD alleles causing Duchenne muscular dystrophy (DMD) than those achieved by AdVs encoding the parental, eCas9.2NLS, protein. In conclusion, this work provides a strong rationale for integrating viral vector and optimized gene-editing technologies to bring about enhanced RGN delivery and performance.

ObjectivesTo understand the molecular features distinguishing anti-citrullinated protein antibodies (ACPA) from ‘conventional’ antibodies in rheumatoid arthritis (RA).MethodsSerum of ACPA-positive RA patients was fractionated by size exclusion chromatography and analysed for the presence of ACPA-IgG by ELISA. ACPA-IgG and non-citrulline-specific IgG were affinity purified from serum, plasma and/or synovial fluid and analysed by gel electrophoresis. Electrophoresis bands were excised, enzymatically digested and analysed by mass spectrometry. Binding affinity to citrullinated antigens was measured by ELISA and imaging surface plasmon resonance using recombinant monoclonal ACPA with molecular modifications.ResultsIn all donor samples studied (n=24), ACPA-IgG exhibited a 10–20 kDa higher molecular weight compared with non-autoreactive IgG. This feature also distinguished ACPA-IgG from antibodies against recall antigens or other disease-specific autoantibodies. Structural analysis revealed that a high frequency of N-glycans in the (hyper)variable domains of ACPA is responsible for this observation. In line with their localisation, these N-glycans were found to modulate binding avidity of ACPA to citrullinated antigens.ConclusionsThe vast majority of ACPA-IgG harbour N-glycans in their variable domains. As N-linked glycosylation requires glycosylation consensus sites in the protein sequence and as these are lacking in the ‘germline-counterparts’ of identified variable domains, our data indicate that the N-glycosylation sites in ACPA variable domains have been introduced by somatic hypermutation. This finding also suggests that ACPA-hyperglycosylation confers a selective advantage to ACPA-producing B cells. This unique and completely novel feature of the citrulline-specific immune response in RA elucidates our understanding of the underlying B cell response.

Herpesviruses are large DNA viruses which depend on many nuclear functions, and therefore on host transport factors to ensure specific nuclear import of viral and host components. While some import cargoes bind directly to certain transport factors, most recruit importin β1 via importin α. We identified importin α1 in a small targeted siRNA screen to be important for herpes simplex virus (HSV-1) gene expression. Production of infectious virions was delayed in the absence of importin α1, but not in cells lacking importin α3 or importin α4. While nuclear targeting of the incoming capsids, of the HSV-1 transcription activator VP16, and of the viral genomes were not affected, the nuclear import of the HSV-1 proteins ICP4 and ICP0, required for efficient viral transcription, and of ICP8 and pUL42, necessary for DNA replication, were reduced. Furthermore, quantitative electron microscopy showed that fibroblasts lacking importin α1 contained overall fewer nuclear capsids, but an increased proportion of mature nuclear capsids indicating that capsid formation and capsid egress into the cytoplasm were impaired. In neurons, importin α1 was also not required for nuclear targeting of incoming capsids, but for nuclear import of ICP4 and for the formation of nuclear capsid assembly compartments. Our data suggest that importin α1 is specifically required for the nuclear localization of several important HSV1 proteins, capsid assembly, and capsid egress into the cytoplasm, and may become rate limiting in situ upon infection at low multiplicity or in terminally differentiated cells such as neurons.

Aims/hypothesis The inflammatory milieu characteristic of insulitis affects translation fidelity and generates defective ribosomal products (DRiPs) that participate in autoimmune beta cell destruction in type 1 diabetes. Here, we studied the role of early innate cytokines (IFNα) and late immune adaptive events (IFNɣ) in insulin DRiP-derived peptide presentation to diabetogenic CD8+ T cells. Methods Single-cell transcriptomics of human pancreatic islets was used to study the composition of the (immuno)proteasome. Specific inhibition of the immunoproteasome catalytic subunits was achieved using siRNA, and antigenic peptide presentation at the cell surface of the human beta cell line EndoC-βH1 was monitored using peptide-specific CD8 T cells. Results We found that IFNγ induces the expression of the PSMB10 transcript encoding the β2i catalytic subunit of the immunoproteasome in endocrine beta cells, revealing a critical role in insulin DRiP-derived peptide presentation to T cells. Moreover, we showed that PSMB10 is upregulated in a beta cell subset that is preferentially destroyed in the pancreases of individuals with type 1 diabetes. Conclusions/interpretation Our data highlight the role of the degradation machinery in beta cell immunogenicity and emphasise the need for evaluation of targeted immunoproteasome inhibitors to limit beta cell destruction in type 1 diabetes. Data availability The single-cell RNA-seq dataset is available from the Gene Expression Omnibus (GEO) using the accession number GSE218316 ( https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE218316 ). Graphical Abstract

Lentiviral vectors have become popular tools for stable genetic modification of mammalian cells. In some applications of lentiviral vector-transduced cells, infectious-lentiviral particles should be absent. Quantification of the free-vector particles that remain from the inoculum can be difficult. Therefore a formula was established that yields an estimation of the ‘Reduction Ratio.’ This ratio represents the loss of titer based on a number of vector-inactivating effects. In this study, we evaluated several parameters and assumptions that were used in the current formula. We generated new data on the stability and trypsin sensitivity of lentiviral vectors pseudotyped with eight heterologous envelope proteins and the loss of vectors by washing or passaging the cell cultures. Our data demonstrate that the loss of virus titer under the influence of trypsin as well as the half-life of the particles in tissue culture medium is dependent on the vector’s envelope protein. While VSV-G-envelope-pseudotyped particles were unsensitive to trypsin, the titer of vectors pseudotyped with other envelope proteins decreased 2–110-fold. The half-life in culture medium ranged from 8 to 40 h for the different envelope-pseudotyped vectors, with 35 h for VSV-G-envelope-pseudotyped vector particles. Additionally, we found that removal of the culture medium from Ø35 mm to Ø10 cm dishes reduces the amount of vector particles in the culture by 50-fold and 20-fold, respectively. Together these data can be used to more precisely estimate the maximum number of free lentiviral vector particles in cell cultures.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy which shows unparalleled therapeutic resistance due to its genetic and cellular heterogeneity, dense stromal tissue, and immune‐suppressive tumour microenvironment. Oncolytic virotherapy has emerged as a new treatment modality which uses tumour‐specific viruses to eliminate cancerous cells. Non‐human primate adenoviruses of the human adenovirus B (HAdV‐B) species have demonstrated considerable lytic potential in human cancer cells as well as limited preexisting neutralizing immunity in humans. Previously, we have generated a new oncolytic derivative of the gorilla‐derived HAdV‐B AdV‐lumc007 named ‘GoraVir’. Here, we show that GoraVir displays oncolytic efficacy in pancreatic cancer cells and pancreatic‐cancer‐associated fibroblasts. Moreover, it retains its lytic potential in monoculture and co‐culture spheroids. In addition, we established the ubiquitously expressed complement receptor CD46 as the main entry receptor for GoraVir. Finally, a single intratumoural dose of GoraVir was shown to delay tumour growth in a BxPC‐3 xenograft model at 10 days post‐treatment. Collectively, these data demonstrate that the new gorilla‐derived oncolytic adenovirus is a potent oncolytic vector candidate that targets both pancreatic cancer cells and tumour‐adjacent stroma. Oncolytic adenovirus ‘GoraVir’ has strong lytic potential in both pancreatic cancer cells and cancer‐associated fibroblasts, which may be facilitated by its use of CD46 for viral entry. Moreover, GoraVir demonstrates superior oncolytic efficacy compared to HAdV‐C5 in spheroid cultures as well as in vivo. This shows that GoraVir exhibits unique oncolytic properties and seems a promising candidate for the treatment of pancreatic cancer.

Non-human primate (NHP)-derived adenoviruses have formed a valuable alternative for the use of human adenoviruses in vaccine development and gene therapy strategies by virtue of the low seroprevalence of neutralizing immunity in the human population. The more recent use of several human adenoviruses as oncolytic agents has exhibited excellent safety profiles and firm evidence of clinical efficacy. This proffers the question whether NHP-derived adenoviruses could also be employed for viral oncolysis in human patients. While vaccine vectors are conventionally made as replication-defective vectors, in oncolytic applications replication-competent viruses are used. The data on NHP-derived adenoviral vectors obtained from vaccination studies can only partially support the suitability of NHP-derived adenoviruses for use in oncolytic virus therapy. In addition, the use of NHP-derived adenoviruses in humans might be received warily given the recent zoonotic infections with influenza viruses and coronaviruses. In this review, we discuss the similarities and differences between human- and NHP-derived adenoviruses in view of their use as oncolytic agents. These include their genome organization, receptor use, replication and cell lysis, modulation of the host’s immune responses, as well as their pathogenicity in humans. Together, the data should facilitate a rational and data-supported decision on the suitability of NHP-derived adenoviruses for prospective use in oncolytic virus therapy.