Engineered HCMV-infected APCs enable the identification of new immunodominant HLA-restricted epitopes of anti-HCMV T-cell immunity.

Complications due to HCMV infection or reactivation remain a challenging clinical problem in immunocompromised patients, mainly due to insufficient or absent T-cell functionality. Knowledge of viral targets is crucial to improve monitoring of high-risk patients and optimise antiviral T-cell therapy. To expand the epitope spectrum, genetically-engineered dendritic cells (DCs) and fibroblasts were designed to secrete soluble (s)HLA-A*11:01 and infected with an HCMV mutant lacking immune evasion molecules (US2-6 + 11). More than 700 HLA-A*11:01-restricted epitopes, including more than 50 epitopes derived from a broad range of HCMV open-reading-frames (ORFs) were identified by mass spectrometry and screened for HLA-A*11:01-binding using established prediction tools. The immunogenicity of the 24 highest scoring new candidates was evaluated in vitro in healthy HLA-A*11:01+/HCMV+ donors. Thus, four subdominant epitopes and one immunodominant epitope, derived from the anti-apoptotic protein UL36 and ORFL101C (A11SAL), were identified. Their HLA-A*11:01 complex stability was verified in vitro. In depth analyses revealed highly proliferative and cytotoxic memory T-cell responses against A11SAL, with T-cell responses comparable to the immunodominant HLA-A*02:01-restricted HCMVpp65NLV epitope. A11SAL-specific T cells were also detectable in vivo in immunosuppressed transplant patients and shown to be effective in an in vitro HCMV-infection model, suggesting their crucial role in inhibiting viral replication and improvement of patient's outcome. The developed in vitro pipeline is the first to utilise genetically-engineered DCs to identify naturally presented immunodominant HCMV-derived epitopes. It therefore offers advantages over in silico predictions, is transferable to other HLA alleles, and will significantly expand the repertoire of viral targets to improve therapeutic options.

Identification of an HLA-A*11:01-restricted neoepitope of mutant PIK3CA and its specific T cell receptors for cancer immunotherapy targeting hotspot driver mutations.

Hotspot driver mutations presented by human leukocyte antigens might be recognized by anti-tumor T cells. Based on their advantages of tumor-specificity and immunogenicity, neoantigens derived from hotspot mutations, such as PIK3CAH1047L, may serve as emerging targets for cancer immunotherapies. NetMHCpan V4.1 was utilized for predicting neoepitopes of PIK3CA hotspot mutation. Using in vitro stimulation, antigen-specific T cells targeting the HLA-A*11:01-restricted PIK3CA mutation were isolated from healthy donor-derived peripheral blood mononuclear cells. T cell receptors (TCRs) were cloned using single-cell PCR and sequencing. Their functionality was assessed through T cell activation markers, cytokine production and cytotoxic response to cancer cell lines pulsed with peptides or transduced genes of mutant PIK3CA. Immunogenic mutant antigens from PIK3CA and their corresponding CD8+ T cells were identified. These PIK3CA mutation-specific CD8+ T cells were subsequently enriched, and their TCRs were isolated. The TCR clones exhibited mutation-specific and HLA-restricted reactivity, demonstrating varying degrees of functional avidity. Identified TCR genes were transferred into CD8+ Jurkat cells and primary T cells deficient of endogenous TCRs. TCR-expressing cells demonstrated specific recognition and reactivity against the PIK3CAH1047L peptide presented by HLA-A*11:01-expressing K562 cells. Furthermore, mutation-specific TCR-T cells demonstrated an elevation in cytokine production and profound cytotoxic effects against HLA-A*11:01+ malignant cell lines harboring PIK3CAH1047L. Our data demonstrate the immunogenicity of an HLA-A*11:01-restricted PIK3CA hotspot mutation and its targeting therapeutic potential, together with promising candidates of TCR-T cell therapy.

Identification of HLA-A*11:01 and A*02:01-Restricted EBV Peptides Using HLA Peptidomics.

Epstein-Barr Virus (EBV) is closely linked to nasopharyngeal carcinoma (NPC), notably prevalent in southern China. Although type II latency of EBV plays a crucial role in the development of NPC, some lytic genes and intermittent reactivation are also critical for viral propagation and tumor progression. Since T cell-mediated immunity is effective in targeted killing of EBV-positive cells, it is important to identify EBV-derived peptides presented by highly prevalent human leukocyte antigen class I (HLA-I) molecules throughout the EBV life cycle. Here, we constructed an EBV-positive NPC cell model to evaluate the presentation of EBV lytic phase peptides on streptavidin-tagged specific HLA-I molecules. Utilizing a mass spectrometry (LC-MS/MS)-based immunopeptidomic approach, we characterized eleven novel EBV peptides as well as two previously identified peptides. Furthermore, we determined these peptides were immunogenic and could stimulate PBMCs from EBV VCA/NA-IgA positive donors in an NPC endemic southern Chinese population. Overall, this work demonstrates that highly prevalent HLA-I-specific EBV peptides can be captured and functionally presented to elicit immune responses in an in vitro model, which provides insight into the epitopes presented during EBV lytic cycle and reactivation. It expands the range of viral targets for potential NPC early diagnosis and treatment.

Missing Self-Induced Microvascular Rejection of Kidney Allografts: A Population-Based Study.

BACKGROUND: Circulating anti-HLA donor-specific antibodies (HLA-DSA) are often absent in kidney transplant recipients with microvascular inflammation (MVI). Missing self, the inability of donor endothelial cells to provide HLA I-mediated signals to inhibitory killer cell Ig-like receptors (KIRs) on recipient natural killer cells, can cause endothelial damage in vitro, and has been associated with HLA-DSA-negative MVI. However, missing self's clinical importance as a nonhumoral trigger of allograft rejection remains unclear. METHODS: In a population-based study of 924 consecutive kidney transplantations between March 2004 and February 2013, we performed high-resolution donor and recipient HLA typing and recipient KIR genotyping. Missing self was defined as the absence of A3/A11, Bw4, C1, or C2 donor genotype, with the presence of the corresponding educated recipient inhibitory KIR gene. RESULTS: We identified missing self in 399 of 924 transplantations. Co-occurrence of missing self types had an additive effect in increasing MVI risk, with a threshold at two concurrent types (hazard ratio [HR], 1.78; 95% confidence interval [95% CI], 1.26 to 2.53), independent of HLA-DSA (HR, 5.65; 95% CI, 4.01 to 7.96). Missing self and lesions of cellular rejection were not associated. No HLA-DSAs were detectable in 146 of 222 recipients with MVI; 28 of the 146 had at least two missing self types. Missing self associated with transplant glomerulopathy after MVI (HR, 2.51; 95% CI, 1.12 to 5.62), although allograft survival was better than with HLA-DSA-associated MVI. CONCLUSION: Missing self specifically and cumulatively increases MVI risk after kidney transplantation, independent of HLA-DSA. Systematic evaluation of missing self improves understanding of HLA-DSA-negative MVI and might be relevant for improved diagnostic classification and patient risk stratification.

HLA-associated protection of lymphocytes during influenza virus infection.

BACKGROUND: Heterozygosity at HLA class I loci is generally considered beneficial for host defense. We report here an element of HLA class I homozygosity that may or may not help preserve its existence in populations but which could indicate a new avenue for antiviral research. METHODS: Lymphocytes from serologically HLA-homozygous or -heterozygous donors were examined for synthesis of influenza virus proteins and RNA after exposure to virus as peripheral blood mononuclear cells. The virus-exposed lymphocytes were also examined for internalization of the virus after exposure, and for susceptibility to virus-specific cytotoxic T lymphocytes in comparison with virus-exposed monocytes/macrophages and unseparated peripheral blood mononuclear cells. Results were compared using two-tailed Fisher's exact test. RESULTS: Serologically-defined HLA-A2-homozygous lymphocytes, in contrast to heterozygous lymphocytes, did not synthesize detectable influenza virus RNA or protein after exposure to the virus. HLA-A2-homozygous lymphocytes, including both homozygous and heterozygous donors by genetic sequence subtyping, did internalize infectious virus but were not susceptible to lysis by autologous virus-specific cytotoxic T lymphocytes ("fratricide"). Similar intrinsic resistance to influenza virus infection was observed with HLA-A1- and HLA-A11-homozygous lymphocytes and with HLA-B-homozygous lymphocytes. CONCLUSIONS: A significant proportion of individuals within a population that is characterized by common expression of HLA class I alleles may possess lymphocytes that are not susceptible to influenza virus infection and thus to mutual virus-specific lysis. Further study may identify new approaches to limit influenza virus infection.

Identification of novel human leukocyte antigen-A*11:01-restricted cytotoxic T-lymphocyte epitopes derived from osteosarcoma antigen papillomavirus binding factor.

Osteosarcoma is the most common malignancy of bone that affects young people. Neoadjuvant chemotherapy and surgery have significantly improved the prognosis. However, the prognosis of non-responders to chemotherapy is still poor. To develop peptide-based immunotherapy for osteosarcoma, we previously identified CTL epitopes derived from papillomavirus binding factor (PBF) in the context of human leukocyte antigen (HLA)-A2, HLA-A24 and HLA-B55. In the present study, we identified two novel CTL epitopes, QVT (QVTVWLLEQK) and LSA (LSALPPPLHK), in the context of HLA-A11 using a sequence of screenings based on the predicted affinity of peptides, in vitro folding ability of peptide/HLA-A11 complex, reactivity of peptide/HLA-A11 tetramer and interferon (IFN)-γ production of T cells that was induced by mixed lymphocyte peptide culture under a limiting dilution condition. CTL clones directed to QVT and LSA peptides showed specific cytotoxicity against HLA-A11+ PBF+ osteosarcoma (HOS-A11) cells. In contrast, another epitope, ASV (ASVLSRRLGK), could highly induce cognate tetramer-positive CTL. This might be because the ASV peptide mimics the peptide ASV (R6Q) (ASVLSQRLGK) derived from bacterial polypeptides, ROK family proteins. However, ASV-induced CTL did not show cytokine production against the cognate peptide. In conclusion, the CTL epitopes QVT and LSA peptides might be useful for the development of immunotherapy targeting PBF for patients with osteosarcoma.

Immune reconstitution of HLA-A*0201/BMLF1- and HLA-A*1101/LMP2-specific Epstein Barr virus cytotoxic T lymphocytes within 90 days after haploidentical hematopoietic stem cell transplantation.

BACKGROUND: Haploidentical hematopoietic stem cell transplant (haplo-HSCT) recipients are at high risk for Epstein Barr virus (EBV)-related diseases. EBV-specific CD8+ cytotoxic T cells can control EBV-infected B cell expansion; however, no studies have investigated EBV-specific immune reconstitution after HSCT, particularly haplo-HSCT. Therefore, in this study, we aimed to characterize EBV-specific immune cell reconstitution after haplo-HSCT. METHODS: HLA-A*1101 and HLA-A*0201 pentamers folded with immunodominant EBV peptides were used to detect EBV-specific CD8+ T cells by flow cytometry in peripheral blood mononuclear cells from 19 haplo-HSCT recipients and the results were compared with those in controls. We also compared the EBV-specific pentamer-binding cell frequencies in patients with or without EBV-related diseases by flow cytometry. RESULTS: Pentamer-binding EBV-specific CD8+ T cells were detected at + 30, + 60 and + 90 days after haplo-HSCT in EBV-seropositive patients subjected to haplo-HSCT from an EBV-seropositive donor. The frequencies of the HLA-A*0201/BMLF1-GLC pentamer in haplo-HSCT patients at + 30 days were significantly lower than those in HLA-A*0201-positive healthy controls (p = 0.019) and patients at + 60 days (p = 0.003). The frequencies of the HLA-A*1101/LMP2-SSC pentamer at + 30, + 60, and + 90 days were significantly decreased compared with those in healthy controls (p = 0.009, 0.019, and 0.039, respectively); however, the frequencies of the HLA-A*1101/LMP2-SSC pentamer did not differ significantly among patients at + 30, + 60, and + 90 days (p = 0.886). There was a significant difference in the frequency of the HLA-A*0201/BMLF1-GLC pentamer at + 60 days between patients with and without EBV-related diseases (p = 0.024). Patients with EBV-related diseases showed lower percentages of HLA-A*0201/BMLF1-GLC specific CD8+ T cells. CONCLUSIONS: Haplo-HSCT recipients could generate EBV-specific CD8+ T cells within + 30 days after transplantation. The HLA-A*0201/BMLF1-GLC pentamer cell frequency at + 60 days may be a useful indicator for monitoring EBV-related diseases in patients after haplo-HSCT. Transfusion with EBV-CTLs within 60 days after haplo-HSCT may have prophylactic effects against EBV-related diseases.

Identification of novel HLA-A11-restricted T-cell epitopes in the Ebola virus nucleoprotein.

The Ebola virus (EBOV) is a very contagious virus that is highly fatal in humans and animals. The largest epidemic was in West Africa in 2014, in which over 11,000 people died. However, to date, there are no licensed vaccines against it. Studies show that CD4+ and CD8+ T-cell responses, especially cytotoxic T-lymphocyte (CTL) responses, play key roles in protecting individuals from EBOV infection. Since HLA-restricted epitope vaccines are likely to be effective and safe immunization strategies for infectious diseases, the present study screened for CTL epitopes in the EBOV-nucleoprotein that are restricted by HLA-A11 (a common allele in Chinese people). Predictive computer analysis of the amino-acid sequence of EBOV-nucleoprotein identified ten putative HLA-A11-restricted epitopes. ELISPOT assay of immunized HLA-A11/DR1 transgenic mice showed that five (GR-9, VR-9, EK-9, PK-9, and RK-9) induced effective CTL responses. Additional epitope analyses will aid the design of epitope vaccines against EBOV.

Differential escape of HCV from CD8+ T cell selection pressure between China and Germany depends on the presenting HLA class I molecule.

Adaptation of hepatitis C virus (HCV) to CD8+ T cell selection pressure is well described; however, it is unclear if HCV differentially adapts in different populations. Here, we studied HLA class I-associated viral sequence polymorphisms in HCV 1b isolates in a Chinese population and compared viral substitution patterns between Chinese and German populations. We identified three HLA class I-restricted epitopes in HCV NS3 with statistical support for selection pressure and found evidence for differential escape pathways between isolates from China and Germany depending on the HLA class I molecule. The substitution patterns particularly differed in the epitope VTLTHPITK1635-1643 , which was presented by HLA-A*03 as well as HLA-A*11, two alleles with highly different frequencies in the two populations. In Germany, a substitution in position seven of the epitope was the most frequent substitution in the presence of HLA-A*03, functionally associated with immune escape and nearly absent in Chinese isolates. In contrast, the most frequent substitution in China was located at position two of the epitope and became the predominant consensus residue. Moreover, substitutions in position one of the epitope were significantly enriched in HLA-A*11-positive individuals in China and associated with different patterns of CD8+ T cell reactivity. Our study confirms the differential escape pathways selected by HCV that depended on different HLA class I alleles in Chinese and German populations, indicating that HCV differentially adapts to distinct HLA class I alleles in these populations. This result has important implications for vaccine design against highly variable and globally distributed pathogens, which may require matching antigen sequences to geographic regions for T cell-based vaccine strategies.

Molecular Pathways for Immune Recognition of Preproinsulin Signal Peptide in Type 1 Diabetes.

The signal peptide region of preproinsulin (PPI) contains epitopes targeted by HLA-A-restricted (HLA-A0201, A2402) cytotoxic T cells as part of the pathogenesis of ß-cell destruction in type 1 diabetes. We extended the discovery of the PPI epitope to disease-associated HLA-B*1801 and HLA-B*3906 (risk) and HLA-A*1101 and HLA-B*3801 (protective) alleles, revealing that four of six alleles present epitopes derived from the signal peptide region. During cotranslational translocation of PPI, its signal peptide is cleaved and retained within the endoplasmic reticulum (ER) membrane, implying it is processed for immune recognition outside of the canonical proteasome-directed pathway. Using in vitro translocation assays with specific inhibitors and gene knockout in PPI-expressing target cells, we show that PPI signal peptide antigen processing requires signal peptide peptidase (SPP). The intramembrane protease SPP generates cytoplasm-proximal epitopes, which are transporter associated with antigen processing (TAP), ER-luminal epitopes, which are TAP independent, each presented by different HLA class I molecules and N-terminal trimmed by ER aminopeptidase 1 for optimal presentation. In vivo, TAP expression is significantly upregulated and correlated with HLA class I hyperexpression in insulin-containing islets of patients with type 1 diabetes. Thus, PPI signal peptide epitopes are processed by SPP and loaded for HLA-guided immune recognition via pathways that are enhanced during disease pathogenesis.

Identification of HLA-B*58:01:21, a novel allele in a Korean individual.

B*58:01:21 has a single nucleotide change, c.264A>G (ACA→ACG at codon 88) compared with B*58:01:01:01.

Identification of the novel HLA-A*11:141 allele in a Chinese bone marrow donor.

HLA-A*11:141 has 1 nucleotide change from HLA-A*11:01:01 at position 470G>C.

HLA-A*11:256Q, a novel HLA-A*11 variant, detected in a Taiwanese individual.

Nucleotide deletions from residues 409 to 417 of HLA-A*11:02:01 results in a novel allele, HLA-A*11:256Q.

Detection of a novel HLA-A*11 variant, A*11:255, in a Taiwanese individual.

One nucleotide substitution at residue 532 of HLA-A*11:02:01 results in a novel allele, HLA-A*11:255.

Two new HLA class I alleles described in a Spanish individual, HLA-A*11:01:01:04 and HLA-B*35:330.

Two new HLA class I alleles, HLA-A*11:01:01:04 and HLA-B*35:330, were characterized in a Spanish patient.

Two new HLA class I alleles - A*11:241 and C*08:132.

HLA-A*11:241 differs from A*11:01:01:01 (215G > A, exon 2, R48Q); HLA-C*08:132 from C*08:02:01:01 (587 T > A exon 3, L172Q).

HLA-A*11:134, a novel HLA-A*11 variant, identified by sequence-based typing in a Taiwanese individual.

A one nucleotide replacement in codon 31 of HLA-A*11:01:01 results in a novel allele, HLA-A*11:134.

Recognition of a novel HLA-A*11 variant, HLA-A*11:196, in a Taiwanese unrelated bone marrow stem cell donor.

One nucleotide substitution at residue 484 of HLA-A*11:01:01:01 results in a novel allele, HLA-A*11:196.

HLA-A*11:235Q, a novel HLA-A*11 variant, detected in a Taiwanese individual.

Nucleotide deletions from residue 120 to 125 of HLA-A*11:01:01:01 result in a novel allele, HLA-A*11:235Q.

Genomic full-length sequence of a novel HLA-A*11:01:01:02 allele was identified in a Chinese bone marrow donor.

Here, we report genomic full-length sequence of a novel HLA-A*11:01:01:02 allele identified in a Chinese individual. HLA-A*11:01:01:02 has three nucleotide differences from HLA-A*11:01:01:01, including 99 C>G of intron 1, 655 C>T and G deletion in position 656 of intron 2.