Blockade of histamine receptor H1 augments immune checkpoint therapy by enhancing MHC-I expression in pancreatic cancer cells

BACKGROUND

Although immune checkpoint blockade (ICB) therapy has proven to be extremely effective at managing certain cancers, its efficacy in treating pancreatic ductal adenocarcinoma (PDAC) has been limited. Therefore, enhancing the effect of ICB could improve the prognosis of PDAC. In this study, we focused on the histamine receptor H1 (HRH1) and investigated its impact on ICB therapy for PDAC.

METHODS

We assessed HRH1 expression in pancreatic cancer cell (PCC) specimens from PDAC patients through public data analysis and immunohistochemical (IHC) staining. The impact of HRH1 in PCCs was evaluated using HRH1 antagonists and small hairpin RNA (shRNA). Techniques including Western blot, flow cytometry, quantitative reverse transcription polymerase chain reaction (RT-PCR), and microarray analyses were performed to identify the relationships between HRH1 and major histocompatibility complex class I (MHC-I) expression in cancer cells. We combined HRH1 antagonism or knockdown with anti-programmed death receptor 1 (αPD-1) therapy in orthotopic models, employing IHC, immunofluorescence, and hematoxylin and eosin staining for assessment.

RESULTS

HRH1 expression in cancer cells was negatively correlated with HLA-ABC expression, CD8+ T cells, and cytotoxic CD8+ T cells. Our findings indicate that HRH1 blockade upregulates MHC-I expression in PCCs via cholesterol biosynthesis signaling. In the orthotopic model, the combined inhibition of HRH1 and αPD-1 blockade enhanced cytotoxic CD8+ T cell penetration and efficacy, overcoming resistance to ICB therapy.

CONCLUSIONS

HRH1 plays an immunosuppressive role in cancer cells. Consequently, HRH1 intervention may be a promising method to amplify the responsiveness of PDAC to immunotherapy.

The temporal expression pattern of classical MHC class I in sleep-restricted mice: Generalizations and broader implications

The intricate relationship between sleep and leukocyte trafficking has garnered intense attention, particularly their homing dynamics to secondary lymphoid organs under normal and restricted sleep (SR). Considering the scarcity of information regarding circadian rhythms in major histocompatibility class I (MHC-I) expression in SR, we designed a study that assessed the temporal expression of MHC-I in murine lymph nodes and spleen and the subsequent effects of sleep recovery. Male C57BL/6, housed in 12:12 light/dark cycle, were grouped into control (C) and SR. SR was carried for one week before lymphoid tissues were sampled at selected time points and assessed for leukocyte number and MHC-I expression. SR resulted in 21% decrease in granulocyte and 24% increase in agranulocyte numbers. In C, MHC-I expression pattern in lymph nodes was bimodal and relatively higher than splenocytes during the animal's active phase (110.2 ± 1.8 vs 81.9 ± 3.8, respectively; p = 0.002). Splenocytes; however, showed a bimodal pattern upon SR, with higher protein levels during the rest than the activity period (154.6 + 36.2 vs 99.5 + 15.9, respectively; p = 0.002), suggesting preparedness for a potential infection. Furthermore, SR caused a significant drop in MHC-I expression at the onset of rest with 57% and 30% reduction in lymph nodes and splenocytes, respectively. However, the overall protein expression collectively taken from both lymphoid tissues remained stable, emphasizing its indispensable role in immunological homeostasis. This stability coincided with the restoration of protein levels to baseline after a short sleep recovery period, resembling a reset for MHC-I antigen presentation following a week of SR. Understanding the interplay between MHC-I expression and contextual factors could enhance treatment protocols, refining the efficacy and time precision of glucocorticoid-based therapies in immune modulation.

Major histocompatibility complex class I molecule expression by pancreatic cancer cells is regulated by activation and inhibition of the epidermal growth factor receptor

Pancreatic cancer is one of the deadliest neoplasms, with a dismal 5-year survival rate of only 10%. The ability of pancreatic cancer cells to evade the immune system hinders an anti-tumor response and contributes to the poor survival rate. Downregulation of major histocompatibility complex (MHC) class I cell-surface expression can aid in immune evasion by preventing endogenous tumor antigens from being presented to cytotoxic T cells. Earlier studies suggested that epidermal growth factor receptor (EGFR) signaling can decrease MHC class I expression on certain cancer cell types. However, even though erlotinib (a tyrosine kinase inhibitor that targets EGFR) is an approved drug for advanced pancreatic cancer treatment, the impact of EGFR inhibition or stimulation on pancreatic cancer cell MHC class I surface expression has not previously been analyzed. In this current study, we discovered that EGFR affects MHC class I mRNA and protein expression by human pancreatic cancer cell lines. We demonstrated that cell-surface MHC class I expression is downregulated upon EGFR activation, and the MHC class I level at the surface is elevated following EGFR inhibition. Furthermore, we found that EGFR associates with MHC class I molecules. By defining a role in pancreatic cancer cells for activated EGFR in reducing MHC class I expression and by revealing that EGFR inhibitors can boost MHC class I expression, our work supports further investigation of combined usage of EGFR inhibitors with immunotherapies against pancreatic cancer.

Functional MHCI deficiency induces ADHD-like symptoms with increased dopamine D1 receptor expression

Inappropriate synaptic development has been proposed as a potential mechanism of neurodevelopmental disorders, including attention-deficit hyperactivity disorder (ADHD). Major histocompatibility complex class I (MHCI), an immunity-associated molecule expressed by neurons in the brain, regulates synaptic development; however, the involvement of MHCI in these disorders remains elusive. We evaluated whether functional MHCI deficiency induced by β2m^-/-Tap1^-/- double-knockout in mice leads to abnormalities akin to those seen in neurodevelopmental disorders. We found that functional MHCI deficiency induced locomotor hyperactivity, motor impulsivity, and attention deficits, three major symptoms of ADHD. In contrast, these mice showed normal spatial learning, behavioral flexibility, social behavior, and sensorimotor integration. In the analysis of the dopamine system, upregulation of dopamine D1 receptor (D1R) expression in the nucleus accumbens and a greater locomotor response to D1R agonist SKF 81297 were found in the functional MHCI-deficient mice. Low-dose methylphenidate, used for the treatment of ADHD patients, alleviated the three behavioral symptoms and suppressed c-Fos expression in the D1R-expressing medium spiny neurons of the mice. These findings reveal an unexpected role of MHCI in three major symptoms of ADHD and may provide a novel landmark in the pathogenesis of ADHD.

Beta2-microglobulin(B2M) in cancer immunotherapies: Biological function, resistance and remedy

Cancer immunotherapies have made much headway during the past decades. Techniques including the immune checkpoint inhibition (ICI) and adoptive cell therapy (ACT) have harvested impressive efficacy and provided far-reaching tools for treating cancer patients. However, due to inadequate priming of the immune system, a certain subgroup of patients remains resistant to cancer immunotherapies during or after the treatment. β2-microglobulin (B2M) is an important subunit of major histocompatibility complex (MHC) class I which exerts substantive biological functions in tumorigenesis and immune control. Accumulating evidence has shown that alterations of B2M gene and B2M proteins contribute to poor reaction to cancer immunotherapies by dampening antigen presentation. Here, we discuss the basic biological functions of B2M, its distribution in a spectrum of cancers, and current understanding of its role in ICI, cancer vaccines and chimeric antigen receptor T cell (CAR-T) therapies. Furthermore, we summarize some promising therapeutic strategies to improve the efficacy inhibited by B2M defects.

HLA-B influences integrin beta-1 expression and pancreatic cancer cell migration

Human leukocyte antigen (HLA) class I molecules present antigenic peptides to cytotoxic T cells, causing lysis of malignant cells. Transplantation biology studies have implicated HLA class I molecules in cell migration, but there has been little evidence presented that they influence cancer cell migration, a contributing factor in metastasis. In this study, we examined the effect of HLA-B on pancreatic cancer cell migration. HLA-B siRNA transfection increased the migration of the S2-013 pancreatic cancer cells but, in contrast, reduced migration of the PANC-1 and MIA PaCa-2 pancreatic cancer cell lines. Integrin molecules have previously been implicated in the upregulation of pancreatic cancer cell migration, and knockdown of HLA-B in S2-013 cells heightened the expression of integrin beta 1 (ITGB1), but in the PANC-1 and MIA PaCa-2 cells HLA-B knockdown diminished ITGB1 expression. A transmembrane sequence in an S2-013 HLA-B heavy chain matches a corresponding sequence in HLA-B in the BxPC-3 pancreatic cancer cell line, and knockdown of BxPC-3 HLA-B mimics the effect of S2-013 HLA-B knockdown on migration. In total, our findings indicate that HLA-B influences the expression of ITGB1 in pancreatic cancer cells, with concurrent distinctions in transmembrane sequences and effects on the migration of the cells.

Efficient preparation of human and mouse CD1d proteins using silkworm baculovirus expression system

CD1d is a major histocompatibility complex (MHC) class I-like glycoprotein and binds to glycolipid antigens that are recognized by natural killer T (NKT) cells. To date, our understanding of the structural basis for glycolipid binding and receptor recognition of CD1d is still limited. Here, we established a preparation method for the ectodomain of human and mouse CD1d using a silkworm-baculovirus expression system. The co-expression of human and mouse CD1d and β2-microglobulin (β2m) in the silkworm-baculovirus system was successful, but the yield of human CD1d was low. A construct of human CD1d fused with β2m via a flexible GS linker as a single polypeptide was prepared to improve protein yield. The production of this single-chained complex was higher (50 μg/larva) than that of the co-expression complex. Furthermore, differential scanning calorimetry revealed that the linker made the CD1d complex more stable and homogenous. These results suggest that the silkworm-baculovirus expression system is useful for structural and biophysical studies of CD1d in several aspects including low cost, easy handling, biohazard-free, rapid, and high yielding.

Molecular polymorphism and expression of MHC I α, II α, II β and II invariant chain in the critically endangered Dabry's sturgeon (Acipenser dabryanus)

The major histocompatibility complex (MHC) is a key player in the regulation of immune responses through presenting foreign antigens to T lymphocytes. In this study, three MHC genes, namely, MHC I α, II α, II β and the II invariant chain (Ii), were identified and characterized in the critically endangered Dabry's sturgeon (Acipenser dabryanus). A tissue distribution study showed that the MHC and Ii transcripts were widely expressed in various tissues. The highest expression levels of MHC I α, II α and Ii were found in the gill, while MHC II β was primarily expressed in the spleen. Challenge of A. dabryanus with a pathogenic bacterium in vivo resulted in significant upregulation of both MHC and Ii expression, indicating potential roles of these genes in immune response. Phylogenetic analysis showed that A. dabryanus MHC grouped with other teleost MHC genes and sequences from Polyodon spathula and A. dabryanus had an intermingling of alleles. According to the split time between paddlefishes and sturgeons, this result indicated that trans-species MHC lineages in Chondrostei were much older than those in tetrapods. The molecular polymorphisms of the complete open reading frame regions of the MHC genes were analysed in several A. dabryanus individuals. MHC II α and II β were highly polymorphic in different individuals, while MHC I α was more conserved. The ratio of non-synonymous substitution occurred at a significantly higher frequency than synonymous substitution in peptide-binding regions (PBR) of MHC II α and II β, demonstrating the existence of positive selection at peptide-binding sites. Our study suggested potential roles of the MHC chains in immune response to pathogen microbial infection, and the numerous alleles identified in this study will help further genetic management and molecular marker-assisted selective breeding programmes in A. dabryanus.

Exploiting non-canonical translation to identify new targets for T cell-based cancer immunotherapy

Cryptic MHC I-associated peptides (MAPs) are produced via two mechanisms: translation of protein-coding genes in non-canonical reading frames and translation of allegedly non-coding sequences. In general, cryptic MAPs are coded by relatively short open reading frames whose translation can be regulated at the level of initiation, elongation or termination. In contrast to conventional MAPs, the processing of cryptic MAPs is frequently proteasome independent. The existence of cryptic MAPs derived from allegedly non-coding regions enlarges the scope of CD8 T cell immunosurveillance from a mere ~2% to as much as ~75% of the human genome. Considering that 99% of cancer-specific mutations are located in those allegedly non-coding regions, cryptic MAPs could furthermore represent a particularly rich source of tumor-specific antigens. However, extensive proteogenomic analyses will be required to determine the breath as well as the temporal and spatial plasticity of the cryptic MAP repertoire in normal and neoplastic cells.

Changes in Expressions of Major Histocompatibility Complex Class I, Paired-Immunoglobulin-Like Receptor B, and Cluster of Differentiation 3ζ in Motor Cortical Representations of the Brachial Plexus After Avulsion in Rats

OBJECTIVE

Major histocompatibility complex class I (MHCI), paired-immunoglobulin-like receptor B (PirB), and cluster of differentiation 3ζ (CD3ζ) negatively regulate neuronal plasticity in developing and adult brains. The aim of this study was to evaluate expressive changes of these factors in motor cortical representations of the brachial plexus (MCRBP) after total brachial plexus root avulsion (tBPRA).

METHODS

A total of 45 rats were randomly and equally divided into 3 groups for evaluating mRNA and protein expression levels of MHCI, PirB, and CD3ζ: 7 days, 3 months, and control. In the 7-day and 3-month groups, expressions were examined at 7 days and 3 months, respectively, after left tBPRA. In the control group, the brachial plexus was uninjured. Three rats from each group were used for examining expressions of MHCI, PirB, and CD3ζ proteins by immunofluorescence labeling, 6 rats for quantification of MHCI, PirB, and CD3ζ mRNAs by real-time quantitative polymerase chain reaction, and the remaining 6 animals for quantification of MHCI, PirB, and CD3ζ proteins by Western blotting.

RESULTS

In the original MCRBP, mRNA and protein expression levels of MHCI, PirB, and CD3ζ were down-regulated 7 days postinjury compared with control (P < 0.01). Interestingly, mRNA and protein expression levels of these factors were up-regulated at 3 months compared with 7 days (P < 0.01), excepting PirB protein, whose expression was not increasing (P > 0.05). Recovery of protein expressions were initiated from near the border region of the original MCRBP.

CONCLUSIONS

MHCI, PirB, and CD3ζ may participate in motor cortical reorganization after tBPRA.

Cancer stem cells: The potential role of autophagy, proteolysis, and cathepsins in glioblastoma stem cells

One major obstacle in cancer therapy is chemoresistance leading to tumor recurrence and metastasis. Cancer stem cells, in particular glioblastoma stem cells, are highly resistant to chemotherapy, radiation, and immune recognition. In case of immune recognition, several survival mechanisms including, regulation of autophagy, proteases, and cell surface major histocompatibility complex class I molecules, are found in glioblastoma stem cells. In different pathways, cathepsins play a crucial role in processing functional proteins that are necessary for several processes and proper cell function. Consequently, strategies targeting these pathways in glioblastoma stem cells are promising approaches to interfere with tumor cell survival and will be discussed in this review.

MHCI promotes developmental synapse elimination and aging-related synapse loss at the vertebrate neuromuscular junction

Synapse elimination at the developing neuromuscular junction (NMJ) sculpts motor circuits, and synapse loss at the aging NMJ drives motor impairments that are a major cause of loss of independence in the elderly. Here we provide evidence that at the NMJ, both developmental synapse elimination and aging-related synapse loss are promoted by specific immune proteins, members of the major histocompatibility complex class I (MHCI). MHCI is expressed at the developing NMJ, and three different methods of reducing MHCI function all disrupt synapse elimination during the second postnatal week, leaving some muscle fibers multiply-innervated, despite otherwise outwardly normal synapse formation and maturation. Conversely, overexpressing MHCI modestly accelerates developmental synapse elimination. MHCI levels at the NMJ rise with aging, and reducing MHCI levels ameliorates muscle denervation in aged mice. These findings identify an unexpected role for MHCI in the elimination of neuromuscular synapses during development, and indicate that reducing MHCI levels can preserve youthful innervation of aging muscle.

Trafficking of MHC molecules to the cell surface creates dynamic protein patches

Major histocompatibility complex class I (MHC-I) molecules signal infection or transformation by engaging receptors on T lymphocytes. The spatial organization of MHC-I on the plasma membranes is important for this engagement. We and others have shown that MHC-I molecules, like other membrane proteins, are not uniformly distributed, but occur in patches in the plasma membrane. Here, we describe the temporal details of MHC-I patch formation and combine them with the spatial details, which we have described earlier, to yield a comprehensive quantitative description of patch formation. MHC-I is delivered to the plasma membrane in clathrin-coated vesicles, arriving at a rate of ∼2.5×10(-3) μm(-1) min(-1) (or about two arrivals per minute over the whole cell). The vesicles dock and fuse at non-random, apparently targeted, locations on the membrane and the newly delivered MHC-I molecules form patches that are a few hundred nanometers in diameter. The patches are maintained at steady state by a dynamic equilibrium between the rate of delivery and the rate of hindered diffusion of MHC-I molecules out of the patches (caused by components of the actin cytoskeleton).

Expression and alternative splicing of classical and nonclassical MHCI genes in the hippocampus and neuromuscular junction

The major histocompatibility complex class I (MHCI) is a large gene family, with over 20 members in mouse. Some MHCIs are well-known for their critical roles in the immune response. Studies in mice which lack stable cell-surface expression of many MHCI proteins suggest that one or more MHCIs also play unexpected, essential roles in the establishment, function, and modification of neuronal synapses. However, there is little information about which genes mediate MHCI's effects in neurons. In this study, RT-PCR was used to simultaneously assess transcription of many MHCI genes in regions of the central and peripheral nervous system where MHCI has a known or suspected role. In the hippocampus, a part of the CNS where MHCI regulates synapse density, synaptic transmission, and plasticity, we found that more than a dozen MHCI genes are transcribed. Single-cell RT-PCR revealed that individual hippocampal neurons can express more than one MHCI gene, and that the MHCI gene expression profile of CA1 pyramidal neurons differs significantly from that of CA3 pyramidal neurons or granule cells of the dentate gyrus. MHCI gene expression was also assessed at the neuromuscular junction (NMJ), a part of the peripheral nervous system (PNS) where MHCI plays a role in developmental synapse elimination, aging-related synapse loss, and neuronal regeneration. Four MHCI genes are expressed at the NMJ at an age when synapse elimination is occurring in three different muscles. Several MHCI mRNA splice variants were detected in hippocampus, but not at the NMJ. Together, these results establish the first profile of MHCI gene expression at the developing NMJ, and demonstrate that MHCI gene expression is under tight spatial and temporal regulation in the nervous system. They also identify more than a dozen MHCIs that could play important roles in regulating synaptic transmission and plasticity in the central and peripheral nervous systems.

Pregnancy boosts vaccine-induced Bovine Neonatal Pancytopenia-associated alloantibodies

Although maternal vaccination is generally considered to be safe, the occurrence of Bovine Neonatal Pancytopenia (BNP) in cattle shows that maternal vaccination may pose a risk to the offspring. Pregsure BVD-induced maternal alloantibodies cause BNP in newborn calves. The occurrence of BNP years after last Pregsure BVD vaccination indicates that alloantibody levels may remain high in dams. Since pregnancy induces alloantibodies we hypothesized that pregnancy boosts the vaccine-induced alloantibody response. Alloantibody levels in Pregsure BVD-vaccinated dams increased from conception towards the end of gestation and declined after parturition. In parallel, BVDV-antibody levels remained constant, indicating that there is specific boosting of alloantibodies. Since the rise in alloantibodies coincides with pregnancy and other alloantigen sources were excluded, we concluded that fetal alloantigens expressed during pregnancy boost the alloimmune response in the dam. These results help explain why BNP cases occur even years after Pregsure BVD has been taken off the market.

Correlation of Single Nucleotide Polymorphism 35-Kb Upstream of HLA-C and Clinical Profile of Multidrug-Resistant Tuberculosis

INTRODUCTION

The SNP HLA-C-35 kb (rs9264942) may contribute to the host immune defense mechanism by affecting the cell surface expression pattern of HLA-C and antigen presentation to CD8+ cytotoxic cells. Thus, this SNP may contribute to intracellular multidrug-resistant (MDR)-tuberculosis (TB) infection.

AIM

To examine the association between the SNP HLA-C-35 kb (rs9264942) and the clinical profile of MDR-TB infection.

SETTINGS AND DESIGN

MDR-TB-positive patients were followed from May 2012 to December 2013 to observe the progression of MDR-TB infection. Non-TB individuals and non-MDR-TB individuals were also recruited as controls.

MATERIALS AND METHODS

The patients' HLA-C-35 kb (rs9264942) status was determined by PCR.

RESULTS

The C allele was slightly more frequent in the MDR-TB patients than in the non-MDR TB patients (OR= 1.28; 95% CI: 0.701 - 2.328). The C allele was found to be more frequent in the MDR-TB patients exhibiting pulmonary fibrosis (OR= 2.13; 95% CI: 0.606 - 7.480) or pulmonary infiltrates (OR= 3.17; 95% CI: 0.690 - 14.598) and among the MDR-TB patients who were classified as underweight (OR= 8.00; 95% CI: 1.261 - 50.770). The CC genotype was associated with the treatment after failure of category II group (OR= 4.17; 95% CI: 1.301 - 13.346).

CONCLUSION

The C allele SNP HLA-C-35 kb (rs9264942) may contribute to the clinical profile in MDR-TB infection.

The role of placental MHC class I expression in immune-assisted separation of the fetal membranes in cattle

The bovine fetus, like that of other species, is a semi-allograft and the regulation of materno-fetal alloimmunity is critical to prevent its immunological rejection. In cattle, a materno-fetal alloimmune response may be beneficial at parturition. It is hypothesized that upregulation of major histocompatibility complex (MHC) class I on the fetal membranes toward the end of gestation induces a maternal alloimmune response that activates innate immune effector mechanisms, aiding in the loss of the adherence between the fetal membranes and the uterus. Loss of fetal-maternal adherence is pivotal for the timely expulsion of the fetal membranes and the absence (or reduction) of the maternal immune response may lead to retained fetal membranes, a common reproductive disorder of cattle. Currently, there is no effective treatment for retained fetal membranes and a better understanding of materno-fetal alloimmune-assisted separation of the fetal membranes may lead to novel targets for the treatment of retained fetal membranes. In this review, the regulation of materno-fetal alloimmunity during pregnancy in cattle, with a focus on placental MHC class I expression, and the importance of maternal alloimmunity for the timely separation of the fetal membranes, are discussed.

An MHC class I immune evasion gene of Marek׳s disease virus

Marek׳s disease virus (MDV) is a widespread α-herpesvirus of chickens that causes T cell tumors. Acute, but not latent, MDV infection has previously been shown to lead to downregulation of cell-surface MHC class I (Virology 282:198-205 (2001)), but the gene(s) involved have not been identified. Here we demonstrate that an MDV gene, MDV012, is capable of reducing surface expression of MHC class I on chicken cells. Co-expression of an MHC class I-binding peptide targeted to the endoplasmic reticulum (bypassing the requirement for the TAP peptide transporter) partially rescued MHC class I expression in the presence of MDV012, suggesting that MDV012 is a TAP-blocking MHC class I immune evasion protein. This is the first unique non-mammalian MHC class I immune evasion gene identified, and suggests that α-herpesviruses have conserved this function for at least 100 million years.

Relationship between Poor Immunogenicity of HLA-A2-Restricted Peptide Epitopes and Paucity of Naïve CD8(+) T-Cell Precursors in HLA-A2-Transgenic Mice

We examined the immunogenicity of H-2 class I-restricted and HLA-A2-restricted epitopes through peptide immunization of HLA-A2-transgenic mice that also express mouse H-2 class I molecules. All four of the tested epitopes restricted by H-2 class I robustly elicited T-cell responses, but four of seven epitopes restricted by HLA-A2 did not induce T-cell responses, showing that HLA-A2-restricted peptide epitopes tend to be poorly immunogenic in HLA-A2-transgenic mice. This finding was confirmed in HLA-A2-transgenic mice infected with a recombinant vaccinia virus expressing hepatitis C virus proteins. We examined the precursor frequency of epitope-specific naïve CD8(+) T cells in HLA-A2-transgenic and conventional C57BL/6 mice and found that the poor immunogenicity of HLA-A2-restricted peptide epitopes is related to the paucity of naïve CD8(+) T-cell precursors in HLA-A2-transgenic mice. These results provide direction for the improvement of mouse models to study epitope repertoires and the immunodominance of human T-cell responses.

MHC binding prediction with KernelRLSpan and its variations

Antigenic peptides presented to T cells by MHC molecules are essential for T or B cells to proliferate and eventually differentiate into effector cells or memory cells. MHC binding prediction is an active research area. Reliable predictors are demanded to identify potential vaccine candidates. The recent kernel-based algorithm KernelRLSpan (Shen et al., 2013) shows promising power on MHC II binding prediction. Here, KernelRLSpan is modified and applied to MHC I binding prediction, which we refer to as KernelRLSpanI. Besides this, we develop a novel consensus method to predict naturally processed peptides through integrating KernelRLSpanI with two state-of-the-art predictors NetMHCpan and NetMHC. The consensus method achieved top performance in the Machine Learning in Immunology (MLI) 2012 Competition,(3) group 2. We also introduce our progress of improving our MHC II binding prediction method KernelRLSpan by diffusion map.

Priming of autoreactive CD8(+) T cells is inhibited by immunogenic peptides which are competitive for major histocompatibility complex class I binding

In the present study, we investigated if priming of autoreactive CD8⁺ T cells would be inhibited by competitive peptides for major histocompatibility complex (MHC) class I binding. We used a mouse model of vitiligo which is induced by immunization of K^b-binding tyrosinase-related protein 2 (TRP2)-180 peptide. Competitive peptides for K^b binding inhibited IFN-γ production and proliferation of TRP2-180-specific CD8⁺ T cells upon ex vivo peptide restimulation, while other MHC class I-binding peptides did not. In mice, the capability of inhibition was influenced by T-cell immunogenicity of the competitive peptides. The competitive peptide with a high T-cell immunogenicity efficiently inhibited priming of TRP2-180-specific CD8⁺ T cells in vivo, whereas the competitive peptide with a low T-cell immunogenicity did not. Taken together, the inhibition of priming of autoreactive CD8⁺ T cells depends on not only competition of peptides for MHC class I binding but also competitive peptide-specific CD8⁺ T cells, suggesting that clonal expansion of autoreactive T cells would be affected by expansion of competitive peptide-specific T cells. This result provides new insights into the development of competitive peptides-based therapy for the treatment of autoimmune diseases.