MHC class I and II-deficient humanized mice are suitable tools to test the long-term antitumor efficacy of immune checkpoint inhibitors and T-cell engagers.

BACKGROUND: Immunodeficient mice engrafted with peripheral blood mononuclear cells (PBMCs) are models to study new cancer immunotherapy agents. However, this approach is associated with xenograft-versus-host disease (xGVHD), which starts early after PBMC transfer and limits the duration and interpretation of experiments. Here, we explore different approaches to overcome xGVHD and better support the development of cancer immunotherapies. METHODS: Immunodeficient NOD-scid IL2Rgnull (NSG) mice were intravenously transferred with human PBMCs and subcutaneously co-engrafted with HT29 human colon carcinoma cells. Diverse strategies to reduce xGVHD while preserving the antitumor activity of human immune cells were evaluated: (1) ex vivo immune graft modification by depleting CD4+ T cells pre-transfer using magnetic beads, (2) post-transplantation cyclophosphamide administration to eliminate proliferating xenoreactive T-cell clones and (3) using major histocompatibility complex (MHC) class I and II-deficient NSG mice: (Kb Db)null (IA)null (MHC-dKO NSG). Body weight and plasma murine alanine aminotransferase levels were measured as indicators of xGVHD and tumor size was measured every 2-3 days to monitor antitumor activity. The antitumor effects and pharmacodynamics of nivolumab plus ipilimumab and an anti-epithelial cell adhesion molecule (EpCAM)/CD3 T-cell engager (αEpCAM/CD3 bispecific antibody (BsAb)) were evaluated in the model. RESULTS: CD4+ T-cell depletion attenuates xGVHD but also abrogates the antitumor activity. Cyclophosphamide limits the antitumor response and does not substantially prevent xGVHD. In contrast, xGVHD was significantly attenuated in MHC-dKO NSG recipients, while the antitumor effect of human PBMCs was preserved. Furthermore, the administration of nivolumab plus ipilimumab caused exacerbated xGVHD in conventional NSG mice, thereby precluding the observation of their antitumor effects. Severe xGVHD did not occur in MHC-dKO NSG mice thus enabling the study of complete and durable tumor rejections. Similarly, NSG mice treated with an αEpCAM/CD3 BsAb showed complete tumor regressions, but died due to xGVHD. In contrast, MHC-dKO NSG mice on treatment with the αEpCAM/CD3 BsAb achieved complete tumor responses without severe xGVHD. A significant proportion of mice rendered tumor-free showed tumor rejection on rechallenge with HT29 cells without further treatment. Finally, tumor-infiltrating CD8+ T-cell number increase, activation and CD137 upregulation were observed on αEpCAM/CD3 BsAb treatment. CONCLUSION: Humanized MHC-dKO immunodeficient mice allow and refine the preclinical testing of immunotherapy agents for which experimentation is precluded in conventional immunodeficient mice due to severe xGVHD.

IL-10 and TGF-ß, but Not IL-17A or IFN-γ, Potentiate the IL-15-Induced Proliferation of Human T Cells: Association with a Decrease in the Expression of ß2m-Free HLA Class I Molecules Induced by IL-15.

IL-15 is a homeostatic cytokine for human T and NK cells. However, whether other cytokines influence the effect of IL-15 is not known. We studied the impact that IL-10, TGF-ß, IL-17A, and IFN-γ have on the IL-15-induced proliferation of human T cells and the expression of HLA class I (HLA-I) molecules. Peripheral blood lymphocytes (PBLs) were labeled with CFSE and stimulated for 12 days with IL-15 in the absence or presence of the other cytokines. The proportion of proliferating T cells and the expression of cell surface HLA-I molecules were analyzed using flow cytometry. The IL-15-induced proliferation of T cells was paralleled by an increase in the expression of HC-10-reactive HLA-I molecules, namely on T cells that underwent ≥5-6 cycles of cell division. It is noteworthy that the IL-15-induced proliferation of T cells was potentiated by IL-10 and TGF-ß but not by IL-17 or IFN-γ and was associated with a decrease in the expression of HC-10-reactive molecules. The cytokines IL-10 and TGF-ß potentiate the proliferative capacity that IL-15 has on human T cells in vitro, an effect that is associated with a reduction in the amount of HC-10 reactive HLA class I molecules induced by IL-15.

Orientia tsutsugamushi Ank5 promotes NLRC5 cytoplasmic retention and degradation to inhibit MHC class I expression.

How intracellular bacteria subvert the major histocompatibility complex (MHC) class I pathway is poorly understood. Here, we show that the obligate intracellular bacterium Orientia tsutsugamushi uses its effector protein, Ank5, to inhibit nuclear translocation of the MHC class I gene transactivator, NLRC5, and orchestrate its proteasomal degradation. Ank5 uses a tyrosine in its fourth ankyrin repeat to bind the NLRC5 N-terminus while its F-box directs host SCF complex ubiquitination of NLRC5 in the leucine-rich repeat region that dictates susceptibility to Orientia- and Ank5-mediated degradation. The ability of O. tsutsugamushi strains to degrade NLRC5 correlates with ank5 genomic carriage. Ectopically expressed Ank5 that can bind but not degrade NLRC5 protects the transactivator during Orientia infection. Thus, Ank5 is an immunoevasin that uses its bipartite architecture to rid host cells of NLRC5 and reduce surface MHC class I molecules. This study offers insight into how intracellular pathogens can impair MHC class I expression.

Cellular stress increases DRIP production and MHC Class I antigen presentation.

Background: Defective ribosomal products (DRiPs) are non-functional proteins rapidly degraded during or after translation being an essential source for MHC class I ligands. DRiPs are characterized to derive from a substantial subset of nascent gene products that degrade more rapidly than their corresponding native retiree pool. So far, mass spectrometry analysis revealed that a large number of HLA class I peptides derive from DRiPs. However, a specific viral DRiP on protein level was not described. In this study, we aimed to characterize and identify DRiPs derived from a viral protein. Methods: Using the nucleoprotein (NP) of the lymphocytic choriomeningitis virus (LCMV) which is conjugated N-terminally to ubiquitin, or the ubiquitin-like modifiers FAT10 or ISG15 the occurrence of DRiPs was studied. The formation and degradation of DRiPs was monitored by western blot with the help of a FLAG tag. Flow cytometry and cytotoxic T cells were used to study antigen presentation. Results: We identified several short lived DRiPs derived from LCMV-NP. Of note, these DRiPs could only be observed when the LCMV-NP was modified with ubiquitin or ubiquitin-like modifiers, but not in the wild type form. Using proteasome inhibitors, we could show that degradation of LCMV-NP derived DRiPs were proteasome dependent. Interestingly, the synthesis of DRiPs could be enhanced when cells were stressed with the help of FCS starvation. An enhanced NP118-126 presentation was observed when the LCMV-NP was modified with ubiquitin or ubiquitin-like modifiers, or under FCS starvation. Conclusion: Taken together, we visualize for the first time DRiPs derived from a viral protein. Furthermore, DRiPs formation, and therefore MHC-I presentation, is enhanced under cellular stress conditions. Our investigations on DRiPs in MHC class I antigen presentation open up new approaches for the development of vaccination strategies.

Energy landscapes of peptide-MHC binding.

Molecules of the Major Histocompatibility Complex (MHC) present short protein fragments on the cell surface, an important step in T cell immune recognition. MHC-I molecules process peptides from intracellular proteins; MHC-II molecules act in antigen-presenting cells and present peptides derived from extracellular proteins. Here we show that the sequence-dependent energy landscapes of MHC-peptide binding encode class-specific nonlinearities (epistasis). MHC-I has a smooth landscape with global epistasis; the binding energy is a simple deformation of an underlying linear trait. This form of epistasis enhances the discrimination between strong-binding peptides. In contrast, MHC-II has a rugged landscape with idiosyncratic epistasis: binding depends on detailed amino acid combinations at multiple positions of the peptide sequence. The form of epistasis affects the learning of energy landscapes from training data. For MHC-I, a low-complexity problem, we derive a simple matrix model of binding energies that outperforms current models trained by machine learning. For MHC-II, higher complexity prevents learning by simple regression methods. Epistasis also affects the energy and fitness effects of mutations in antigen-derived peptides (epitopes). In MHC-I, large-effect mutations occur predominantly in anchor positions of strong-binding epitopes. In MHC-II, large effects depend on the background epitope sequence but are broadly distributed over the epitope, generating a bigger target for escape mutations due to loss of presentation. Together, our analysis shows how an energy landscape of protein-protein binding constrains the target of escape mutations from T cell immunity, linking the complexity of the molecular interactions to the dynamics of adaptive immune response.

Immunoproteomic discovery of Mycobacterium bovis antigens, including the surface lipoprotein Mpt83 as a T cell antigen useful for vaccine development.

Tuberculosis (TB) is one of the leading causes of death from infectious diseases, killing approximately 1.3 million people worldwide in 2022 alone. The current vaccine for TB contains a live attenuated bacterium, Mycobacterium bovis BCG (Bacille Calmette-Guérin). The BCG vaccine is highly effective in preventing severe forms of childhood TB but does not protect against latent infection or disease in older age groups. A new or improved BCG vaccine for prevention of pulmonary TB is urgently needed. In this study, we infected murine bone marrow derived dendritic cells from C57BL/6 mice with M. bovis BCG followed by elution and identification of BCG-derived MHC class I and class II-bound peptides using tandem mass spectrometry. We identified 1436 MHC-bound peptides of which 94 were derived from BCG. Fifty-five peptides were derived from MHC class I molecules and 39 from class II molecules. We tested the 94 peptides for their immunogenicity using IFN- γ ELISPOT assay with splenocytes purified from BCG immunized mice and 10 showed positive responses. Seven peptides were derived from MHC II and three from MHC class I. In particular, MHC class II binding peptides derived from the mycobacterial surface lipoprotein Mpt83 were highly antigenic. Further evaluations of these immunogenic BCG peptides may identify proteins useful as new TB vaccine candidates.

Immunogenetic profiles of 9 human herpes virus envelope glycoproteins.

Human herpes viruses (HHV) are ubiquitous and have been implicated in numerous long-term health conditions. Since the association between viral exposure and long-term health impacts is partially influenced by variation in human leukocyte antigen (HLA) genes, we evaluated in silico the binding affinities of 9 HHV envelope glycoproteins with 127 common HLA Class I and Class II molecules. The findings show substantial variability in HHV binding affinity across viruses, HLA Class, HLA genes, and HLA alleles. Specific findings were as follows: (1) the predicted binding affinities of HHVs were characterized by four distinct groupings-[HHV1, HHV2], [HHV3, HHV4, HHV5], [HHV6A], [HHV6B, HHV7, HHV8]-with relatively lower binding affinities for HHV1, HHV2, and HHV6a compared to other HHVs; (2) significantly higher binding affinity was found for HLA Class I relative to Class II; (3) analyses within each class demonstrated that alleles of the C gene (for Class I) and DRB1 gene (for Class II) had the highest binding affinities; and (4) for each virus, predicted binding affinity to specific alleles varied, with HHV6a having the lowest affinity for HHV-HLA complexes, and HHV3, HHV4, and HHV5 having the highest. Since HLA-antigen binding is the first step in initiating an immune response to foreign antigens, these relative differences in HHV binding affinities are likely to influence long-term health impacts such that the cells infected with viruses associated with higher binding affinities across common HLA alleles may be more reduced in numbers, thereby lowering the potential for long-term sequelae of their infections.

Torque teno viruses exhaust and imprint the human immune system via the HLA-E/NKG2A axis.

The ubiquitous Torque teno virus (TTV) establishes a chronically persistent infection in the human host. TTV has not been associated with any apparent disease, but, as part of the human virome, it may confer a regulatory imprint on the human immune system with as yet unclear consequences. However, so far, only few studies have characterized the TTV-specific immune responses or the overall immunological imprints by TTV. Here, we reveal that TTV infection leads to a highly exhausted TTV-specific CD8+ T-cell response, hallmarked by decreased IFN-γ production and the expression of the inhibitory NKG2A-receptor. On a functional level, we identified a panel of highly polymorphic TTV-encoded peptides that lead to an expansion of regulatory NKG2A+ natural killer, NKG2A+CD4+, and NKG2A+CD8+ T cells via the stabilization of the non-classical HLA-E molecule. Our results thus demonstrate that TTV leads to a distinct imprint on the human immune system that may further regulate overall human immune responses in infectious, autoimmune, and malignant diseases.

Identification of immunogenic HLA class I and II neoantigens using surrogate immunopeptidomes.

Neoantigens arising from somatic mutations are tumor specific and induce antitumor host T cell responses. However, their sequences are individual specific and need to be identified for each patient for therapeutic applications. Here, we present a proteogenomic approach for neoantigen identification, named Neoantigen Selection using a Surrogate Immunopeptidome (NESSIE). This approach uses an autologous wild-type immunopeptidome as a surrogate for the tumor immunopeptidome and allows human leukocyte antigen (HLA)-agnostic identification of both HLA class I (HLA-I) and HLA class II (HLA-II) neoantigens. We demonstrate the direct identification of highly immunogenic HLA-I and HLA-II neoantigens using NESSIE in patients with colorectal cancer and endometrial cancer. Fresh or frozen tumor samples are not required for analysis, making it applicable to many patients in clinical settings. We also demonstrate tumor prevention by vaccination with selected neoantigens in a preclinical mouse model. This approach may benefit personalized T cell-mediated immunotherapies.

Sex and disease regulate major histocompatibility complex class I expression in human lung epithelial cells.

Major histocompatibility complex class I (MHC I) molecules present peptides to CD8+ T-cells for immunosurveillance of infection and cancer. Recent studies indicate lineage-specific heterogeneity in MHC I expression. While respiratory diseases rank among the leading causes of mortality, studies in mice have shown that lung epithelial cells (LECs) express the lowest levels of MHC I in the lung. This study aims to answer three questions: (i) Do human LECs express low levels of MHC I? (ii) Is LEC MHC I expression modulated in chronic respiratory diseases? (iii) Which factors regulate MHC I levels in human LECs? We analyzed human LECs from parenchymal explants using single-cell RNA sequencing and immunostaining. We confirmed low constitutive MHC I expression in human LECs, with significant upregulation in chronic respiratory diseases. We observed a sexual dimorphism, with males having higher MHC I levels under steady-state conditions, likely due to differential redox balance. Our study unveils the complex interplay between MHC I expression, sex, and respiratory disease. Since MHC I upregulation contributes to the development of immunopathologies in other models, we propose that it may have a similar impact on chronic lung disease.

Nilotinib boosts the efficacy of anti-PDL1 therapy in colorectal cancer by restoring the expression of MHC-I.

BACKGROUND: Although immune checkpoint inhibitors (ICIs) have revolutionized the landscape of cancer treatment, only a minority of colorectal cancer (CRC) patients respond to them. Enhancing tumor immunogenicity by increasing major histocompatibility complex I (MHC-I) surface expression is a promising strategy to boost the antitumor efficacy of ICIs. METHODS: Dual luciferase reporter assays were performed to find drug candidates that can increase MHC-I expression. The effect of nilotinib on MHC-I expression was verified by dual luciferase reporter assays, qRT-PCR, flow cytometry and western blotting. The biological functions of nilotinib were evaluated through a series of in vitro and in vivo experiments. Using RNA-seq analysis, immunofluorescence assays, western blotting, flow cytometry, rescue experiments and microarray chip assays, the underlying molecular mechanisms were investigated. RESULTS: Nilotinib induces MHC-I expression in CRC cells, enhances CD8+ T-cell cytotoxicity and subsequently enhances the antitumor effects of anti-PDL1 in both microsatellite instability and microsatellite stable models. Mechanistically, nilotinib promotes MHC-I mRNA expression via the cGAS-STING-NF-κB pathway and reduces MHC-I degradation by suppressing PCSK9 expression in CRC cells. PCSK9 may serve as a potential therapeutic target for CRC, with nilotinib potentially targeting PCSK9 to exert anti-CRC effects. CONCLUSION: This study reveals a previously unknown role of nilotinib in antitumor immunity by inducing MHC-I expression in CRC cells. Our findings suggest that combining nilotinib with anti-PDL1 therapy may be an effective strategy for the treatment of CRC.

Modulation of MHC expression by interferon-gamma and its influence on PBMC-mediated cytotoxicity in canine mast cell tumour cells.

Immunotherapy is a promising alternative treatment for canine mast cell tumour (MCT). However, evasion of immune recognition by downregulating major histocompatibility complex (MHC) molecules might decline treatment efficiency. Enhancing MHC expression through interferon-gamma (IFN-γ) is crucial for effective immunotherapy. In-house and reference canine MCT cell lines derived from different tissue origins were used. The impacts of IFN-γ treatment on cell viability, expression levels of MHC molecules, as well as cell apoptosis were evaluated through the MTT assay, RT-qPCR and flow cytometry. The results revealed that IFN-γ treatment significantly influenced the viability of canine MCT cell lines, with varying responses observed among different cell lines. Notably, IFN-γ treatment increased the expression of MHC I and MHC II, potentially enhancing immune recognition and MCT cell clearance. Flow cytometry analysis in PBMCs-mediated cytotoxicity assays showed no significant differences in overall apoptosis between IFN-γ treated and untreated canine MCT cell lines across various target-to-effector ratios. However, a trend towards higher percentages of late and total apoptotic cells was observed in the IFN-γ treated C18 and CMMC cell lines, but not in the VIMC and CoMS cell lines. These results indicate a variable response to IFN-γ treatment among different canine MCT cell lines. In summary, our study suggests IFN-γ's potential therapeutic role in enhancing immune recognition and clearance of MCT cells by upregulating MHC expression and possibly promoting apoptosis, despite variable responses across different cell lines. Further investigations are necessary to elucidate the underlying mechanisms and evaluate IFN-γ's efficacy in in vivo models.

Myasthenia gravis: the future is here.

Myasthenia gravis (MG) stands as a prototypical antibody-mediated autoimmune disease: it is dependent on T cells and characterized by the presence of autoantibodies targeting proteins located on the postsynaptic surface of skeletal muscle, known as the neuromuscular junction. Patients with MG exhibit a spectrum of weakness, ranging from limited ocular muscle involvement to life-threatening respiratory failure. Recent decades have witnessed substantial progress in understanding the underlying pathophysiology, leading to the delineation of distinct subcategories within MG, including MG linked to AChR or MuSK antibodies as well as age-based distinction, thymoma-associated, and immune checkpoint inhibitor-induced MG. This heightened understanding has paved the way for the development of more precise and targeted therapeutic interventions. Notably, the FDA has recently approved therapeutic inhibitors of complement and the IgG receptor FcRn, a testament to our improved comprehension of autoantibody effector mechanisms in MG. In this Review, we delve into the various subgroups of MG, stratified by age, autoantibody type, and histology of the thymus with neoplasms. Furthermore, we explore both current and potential emerging therapeutic strategies, shedding light on the evolving landscape of MG treatment.

Next-generation sequencing reveals additional HLA class I and class II alleles associated with type 1 diabetes and age at onset.

Introduction: Type 1 diabetes is an autoimmune disease with an significant genetic component, played mainly by the HLA class II genes. Although evidence on the role of HLA class I genes in developing type 1 diabetes and its onset have emerged, current HLA screening is limited to determining DR3 and DR4 haplotypes. This study aimed to investigate the role of HLA genes on type 1 diabetes risk and age of onset by extensive typing. Methods: This study included 115 children and young adults with type 1 diabetes for whom typing of HLA-A, -B, -C, -DRB1, -DRB3/4/5, -DQA1, -DQB1, -DPA1 and -DPB1 genes was conducted using Next Generation Sequencing. Results: We observed that 13% of type 1 diabetes subjects had non-classical HLA haplotypes that predispose to diabetes. We also found that compared to type 1 diabetes subjects with classical HLA haplotypes, non-classical HLA subjects had a significantly higher frequency of HLA-B*39:06:02 (p-value=0.01) and HLA-C*07:02:01 (p-value=0.03) alleles, known to be involved in activating the immune response. Non-classical HLA subjects also presented peculiar clinical features compared to classical HLA subjects, such as multiple diabetic antibodies and the absence of other autoimmune diseases (i.e., coeliac disease and thyroiditis). We also observed that subjects with early onset had a higher frequency of DQ2/DQ8 genotype than late-onset individuals. Moreover, subjects with late-onset had a higher frequency of alleles HLA-B*27 (p-value=0.003), HLA-C*01:02:01 (p-value=0.027) and C*02:02:02 (p-value=0.01), known to be associated with increased protection against viral infections. Discussion: This study reveals a broader involvement of the HLA locus in the development and onset of type 1 diabetes, providing insights into new possible disease prevention and management strategies.

MEST promotes immune escape in gastric cancer by downregulating MHCI expression via SHP2.

BACKGROUND: Immune escape is a major obstacle to T-cell-based immunotherapy for cancers such as gastric cancer (GC). Mesoderm-specific transcript (MEST) is a tumor-promoting factor that regulates multiple oncogenic signaling pathways. However, the role of MEST-mediated immune escape is unclear. METHODS: Bioinformatics analysis of MEST expression and enrichment pathways were performed Quantitative reverse transcription PCR (qPCR) or western blot was used to detect the expression of MEST, Src homology region 2-containing protein tyrosine phosphatase 2 (SHP2), Major histocompatibility class I (MHCI)-related genes. Cell function was assessed by Cell Counting Kit (CCK)-8, Transwell, Lactate dehydrogenase (LDH) kit, flow cytometry, enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry (IHC). Xenograft nude mice and immune-reconstructed mice were used to test the effects of different treatments on tumor growth and immune escape in vivo. RESULTS: MEST was upregulated in GC and promoted tumor proliferation, migration, and invasion. Rescue experiments revealed that TNO155 treatment or knockdown of SHP2 promoted the killing ability of CD8+ T cells and the expression of granzyme B (GZMB) and interferon-gamma (IFN-γ), and MEST overexpression reversed the effect. In vivo experiments confirmed that MEST promoted tumor growth, knockdown of MEST inhibited immune escape in GC, and that combination treatment with anti-PD-1 improved anti-tumor activity. CONCLUSION: In this study, we demonstrated that MEST inhibited IFN-γ secretion from CD8+ T cells by up-regulating SHP2, thereby downregulating MHCI expression in GC cells to promote immune escape and providing a new T cell-based therapeutic potential for GC.

Prognostic Impact of Human Lymphocyte Antigen (HLA) Class I Expression in Patients With Breast Cancer.

BACKGROUND/AIM: Various biomarkers are utilized in the field of breast cancer. Human lymphocyte antigen (HLA) class I molecules have a critical role in cancer immune surveillance. Therefore, this study aimed to assess the HLA class I expression and analyze the correlation with clinicopathologic factors in breast cancer. PATIENTS AND METHODS: We investigated the clinical pathology archives of 150 consecutive patients with breast cancer who underwent a curative operation at the Sapporo Medical University, Japan, from January 2012 to December 2014. Immunohistochemical staining was used to evaluate HLA class I expression and CD8-positive T cell infiltration. The Pearson χ2 test was used to assess HLA class I expression level and clinicopathological parameters. The Kaplan-Meier method was used to evaluate survival and the log-rank test to analyze the differences between survival curves. RESULTS: Patients with dull/negative HLA class I had significantly poor disease-free survival (DFS) compared with those with positive HLA class I (p=0.0073). Univariate analyses revealed that pT, pN, positive lymphatic invasion, and dull/negative HLA class I were significantly associated with DFS. Multivariate analyses revealed dull/negative HLA class I as an independent poor prognostic factor (hazard ratio=2.75, 95% confidence interval=1.30-5.80, p=0.008). CONCLUSION: HLA class I expression level may have a very sensitive prognostic effect on patients with breast cancer.

Association of immune evasion in myeloid sarcomas with disease manifestation and patients' survival.

Introduction: Myeloid sarcomas (MS) comprise rare extramedullary manifestations of myeloid neoplasms with poor patients' outcome. While the clinical relevance of the tumor microenvironment (TME) is well established in many malignancies, there exists limited information in MS. Methods: The expression of the human leukocyte antigen class I (HLA-I) antigens, HLA-I antigen processing and presenting machinery (APM) components and the composition of the TME of 45 MS and paired bone marrow (BM) samples from two independent cohorts were assessed by immunohistochemistry, multispectral imaging, and RNA sequencing (RNAseq). Results: A significant downregulation of the HLA-I heavy chain (HC; 67.5%) and ß2-microglobulin (ß2M; 64.8%), but an upregulation of HLA-G was found in MS compared to BM samples, which was confirmed in a publicly available dataset. Moreover, MS tumors showed a predominantly immune cell excluded TME with decreased numbers of tissue infiltrating lymphocytes (TILs) (9.5%) compared to paired BM (22.9%). RNAseq analysis of a subset of 10 MS patients with preserved and reduced HLA-I HC expression revealed 150 differentially expressed genes and a significantly reduced expression of inflammatory response genes was found in samples with preserved HLA-I expression. Furthermore, low HLA-I expression and low TIL numbers in the TME of MS cases were linked to an inferior patients' outcome. Discussion: This study demonstrated a high prevalence of immune escape strategies in the pathogenesis and extramedullary spread of MS, which was also found in patients without evidence of any BM pathology, which yields the rational for the development of novel individually tailored therapies for MS patients.

RLpMIEC: High-Affinity Peptide Generation Targeting Major Histocompatibility Complex-I Guided and Interpreted by Interaction Spectrum-Navigated Reinforcement Learning.

Major histocompatibility complex (MHC) plays a vital role in presenting epitopes (short peptides from pathogenic proteins) to T-cell receptors (TCRs) to trigger the subsequent immune responses. Vaccine design targeting MHC generally aims to find epitopes with a high binding affinity for MHC presentation. Nevertheless, to find novel epitopes usually requires high-throughput screening of bulk peptide database, which is time-consuming, labor-intensive, more unaffordable, and very expensive. Excitingly, the past several years have witnessed the great success of artificial intelligence (AI) in various fields, such as natural language processing (NLP, e.g., GPT-4), protein structure prediction and engineering (e.g., AlphaFold2), and so on. Therefore, herein, we propose a deep reinforcement-learning (RL)-based generative algorithm, RLpMIEC, to quantitatively design peptide targeting MHC-I systems. Specifically, RLpMIEC combines the energetic spectrum (namely, the molecular interaction energy component, MIEC) based on the peptide-MHC interaction and the sequence information to generate peptides with strong binding affinity and precise MIEC spectra to accelerate the discovery of candidate peptide vaccines. RLpMIEC performs well in all the generative capability evaluations and can generate peptides with strong binding affinities and precise MIECs and, moreover, with high interpretability, demonstrating its powerful capability in participation for accelerating peptide-based vaccine development.

Is HLA-E with its receptors an immune checkpoint or an antigenic determinant in allo-HCT?

Hematopoietic cell transplantation (HCT) represents a potentially curative therapeutic approach for various hematologic and non-hematologic malignancies. Human leukocyte antigen (HLA) matching is still the central selection criterion for HCT donors. Nevertheless, post-transplant complications, in particular graft-versus-host disease (GvHD), relapse of disease and infectious complications, represent a major challenge and contribute significantly to morbidity and mortality. Recently, non-classical HLA class I molecules, especially HLA-E, have gained increasing attention in the context of allogeneic HCT. This review aims to summarize the latest findings on the immunomodulatory role of HLA-E, which serves as a ligand for receptors of the innate and adaptive immune system. In particular, we aim to elucidate how (i) polymorphisms within HLA-E, (ii) the NKG2A/C axis and (iii) the repertoire of peptides presented by HLA-E jointly influence the functionality of immune effector cells. Understanding this intricate network of interactions is crucial as it significantly affects NK and T cell responses and thus clinical outcomes after HCT.

The neonatal Fc receptor (FcRn) is a pan-arterivirus receptor.

Arteriviruses infect a variety of mammalian hosts, but the receptors used by these viruses to enter cells are poorly understood. We identified the neonatal Fc receptor (FcRn) as an important pro-viral host factor via comparative genome-wide CRISPR-knockout screens with multiple arteriviruses. Using a panel of cell lines and divergent arteriviruses, we demonstrate that FcRn is required for the entry step of arterivirus infection and serves as a molecular barrier to arterivirus cross-species infection. We also show that FcRn synergizes with another known arterivirus entry factor, CD163, to mediate arterivirus entry. Overexpression of FcRn and CD163 sensitizes non-permissive cells to infection and enables the culture of fastidious arteriviruses. Treatment of multiple cell lines with a pre-clinical anti-FcRn monoclonal antibody blocked infection and rescued cells from arterivirus-induced death. Altogether, this study identifies FcRn as a novel pan-arterivirus receptor, with implications for arterivirus emergence, cross-species infection, and host-directed pan-arterivirus countermeasure development.