Identification of TRDV-TRAJ V domains in human and mouse T-cell receptor repertoires.

Here, we describe the identification of two T-cell receptors (TRs) containing TRDV genes in their TRA chains, the first one in human and the second one in mouse. First, using 5'RACE on a mixed lymphocyte-tumor cell culture (MLTC), we identified TRDV1 5'-untranslated region (UTR) and complete coding sequence rearranged productively to TRAJ24. Single-cell TR RNA sequencing (RNA-seq) of the MLTC, conducted to identify additional clonotypes, revealed that the analysis software detected the hybrid TRDV-TRAJ TRA (TRA) chain but excluded it from the final results. In a separate project, we performed TR sequencing of tumor-infiltrating lymphocytes (TILs) in a murine tumor model. Here, the predominant clonotype contained a TRA chain with a TRDV2-2-TRAJ49 rearrangement. Again, the hybrid TRA chain was not reported in the final results. Transfection of both TR cDNAs resulted in cell surface localization of TR together with CD3, suggesting a productive protein in both cases. Tumor recognition of the Homo sapiens (Homsap) TRDV1-containing TR could be demonstrated by IFN Gamma ELISA ELISpot kit, whereas the Mus musculus (Musmus) TR did not recognize a tumor-derived cell line. To determine whether the TRDV-containing TRA chains we detected were rare events or whether TRDV genes are commonly incorporated into TRA chains, we queried the NCBI Sequence Read Archive for TR single-cell RNA-seq data and analyzed 21 human and 23 murine datasets. We found that especially Homsap TRDV1, Musmus TRDV1, and to some extent Musmus TRDV2-2 are more commonly incorporated into TRA chains than several TRAV genes, making those TRDV genes a relevant contribution to TRA diversity. TRDV-containing TRA chains are currently excluded from the final results of V-(D)-J dataset analyses with the CellRanger software. We provide a work-around to avoid exclusion of those hybrid TRA chains from the final analysis results.

Targeting the melanoma-associated antigen CSPG4 with HLA-C*07:01-restricted T-cell receptors.

Intorduction: Chondroitin sulfate proteoglycan 4 (CSPG4), also known as high molecular weight-melanoma associated antigen, is expressed in melanoma but also other tumor entities and constitutes an attractive target for immunotherapeutic approaches. While recent preclinical reports focused on anti-CSPG4 chimeric antigen receptors (CAR), we here explore T-cell receptor (TCR)-based approaches targeting CSPG4. Methods: The TCRs of two CSPG4-reactive T-cell clones (11C/73 and 2C/165) restricted by the highly prevalent HLA-C*07:01 allele were isolated and the respective αßTCR pairs were retrovirally expressed in CRISPR/Cas9-edited TCR-knockout T cells for functional testing. We also combined alpha and beta TCR chains derived from 11C/73 and 2C/165 in a cross-over fashion to assess for hemichain dominance. CSPG4+ melanoma, glioblastoma and lung cancer cell lines were identified and, if negative, retrovirally transduced with HLA-C*07:01. Results: Functional tests confirmed specific recognition of CSPG4+HLA-C*07:01+ target cells by the αßTCR retrieved from the parental T-cell clones and in part also by the cross-over TCR construct 2Cα-11Cß. Despite high surface expression, the 11Cα-2Cß combination, however, was not functional. Discussion: Collectively, 11C/73- and 2C/165-expressing T cells specifically and efficiently recognized CSPG4+HLA-C*07:01+ cancer cells which warrants further preclinical and clinical evaluation of these TCRs.

Conversion From Intravenous Alteplase to Tenecteplase for Treatment of Acute Ischemic Stroke Across a Large Community Hospital Health System.

BACKGROUND: Recent evidence suggests tenecteplase at an intravenous dose of 0.25 mg/kg is as safe and efficacious as intravenous alteplase standard dose and demonstrates a more favorable pharmacokinetic profile for treatment of acute ischemic stroke. OBJECTIVE: The purpose was to compare the safety and efficacy of alteplase versus tenecteplase for the treatment of acute ischemic stroke at a large community hospital health system following conversion in the preferred formulary thrombolytic. METHODS: Prior to converting, medication safety and operationalization analyses were conducted. A multicenter, retrospective medical record review was performed for patients who received alteplase 6 months prior to formulary thrombolytic conversion and for tenecteplase 6 months post-conversion for the treatment of acute ischemic stroke. Primary outcomes included the rate of symptomatic intracranial and extracranial hemorrhage complications. Secondary outcomes included door-to-needle time, reduction in National Institute Health Stroke Scale at 24 hours and at discharge, order-to-administration time, and thrombolytic errors. The rates of hemorrhage were compared using binomial regression. RESULTS: Of the 287 patients reviewed, 115 received alteplase and 172 received tenecteplase. Symptomatic intracranial hemorrhagic complications occurred in 1 patient (1%) who received alteplase compared with 3 patients (2%) who received tenecteplase (P = 0.9). There was no statistical difference in rates of symptomatic intracranial or extracranial hemorrhagic complications. CONCLUSION AND RELEVANCE: Conversion from alteplase to tenecteplase can be safely and effectively achieved at a large community hospital health system with differing levels of stroke certification. There were also additional cost savings and practical advantages including workflow benefits.

A bicistronic vector backbone for rapid seamless cloning and chimerization of αßT-cell receptor sequences.

To facilitate preclinical testing of T-cell receptors (TCRs) derived from tumor-reactive T-cell clones it is necessary to develop convenient and rapid cloning strategies for the generation of TCR expression constructs. Herein, we describe a pDONR™221 vector backbone allowing to generate Gateway™ compatible entry clones encoding optimized bicistronic αßTCR constructs. It harbors P2A-linked TCR constant regions and head-to-head-oriented recognition sites of the Type IIS restriction enzymes BsmBI and BsaI for seamless cloning of the TCRα and TCRß V(D)J regions, respectively. Additional well-established TCR optimizations were incorporated to enhance TCR functionality. This included replacing of the human αßTCR constant regions with their codon-optimized murine counterparts for chimerization, addition of a second interchain disulfide bond and arrangement of the TCR chains in the order ß-P2A-α. We exemplified the utility of our vector backbone by cloning and functional testing of three melanoma-reactive TCRs in primary human T cells.

Life-threatening disseminated enterovirus infection during combined rituximab and ibrutinib maintenance treatment for mantle cell lymphoma: a case report.

BACKGROUND: Rituximab is a well-established component of treatment regimens for B-cell non-Hodgkin lymphoma. Rituximab binds the CD20 antigen on the surface of B lymphocytes, causing an enhanced clearance of malignant and benign B cells. Thus, rituximab leads to depletion of normal B lymphocytes as well, which can cause substantial immunodeficiency. Ibrutinib inhibits the Bruton tyrosine kinase and thereby B-cell activity. It is used for the treatment of different B-lymphocyte malignancies, such as mantle cell lymphoma. Recently, the combination of both drugs has been tested in various clinical scenarios. CASE PRESENTATION: We present a case of disseminated enterovirus infection resulting from combined rituximab and ibrutinib maintenance treatment in a 57-year-old Caucasian patient. with mantle cell lymphoma. Initially presenting with myositis symptoms, further diagnostic investigation revealed myocarditis, enteritis, myeloencephalitis, and hepatitis. These organ manifestations led to potentially life-threatening complications such as rhabdomyolysis, delirium, and heart rhythm disturbances. After treatment with high-dose intravenous immunoglobulins, virus clearance was achieved and organ functions could be restored. CONCLUSIONS: This case emphasizes the risk of combined therapy with rituximab/ibrutinib for severe immune-related side effects with the necessity of continuous patient monitoring. High-dose intravenous therapy should be considered as treatment for severe enterovirus infection. In severe enterovirus infections, we recommend subtyping for the development of efficient preventive and therapeutic strategies.

NPM-ALK-reactive T-cell responses in children and adolescents with NPM-ALK positive anaplastic large cell lymphoma.

The oncoantigen nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) induces cellular and humoral immune responses in patients with NPM-ALK-positive anaplastic large cell lymphoma (ALCL). We characterize the NPM-ALK-specific T-cell responses in a cohort of pediatric and adolescent ALCL-patients in remission without Human Leucocyte Antigen (HLA)-preselection. First, we assessed NPM-ALK-reactive T-cell responses and their HLA-class I restriction in patients by using dendritic cells (DCs) transfected with in vitro transcribed (IVT) NPM-ALK-RNA for CD8 (n = 20) or CD3 (n = 9) T-cell stimulation. NPM-ALK-specific T-cells were detected in twelve of 29 patients (nine of 20 with CD8-selected and three of nine with CD3-selected cells). Recognition of NPM-ALK was restricted by HLA-C alleles in six of eight, and by HLA-B alleles in four of eight analyzed patients. No NPM-ALK-reactivity was detected in 20 healthy individuals. Second, in order to define possible immunogenic NPM-ALK-epitope regions, DCs pulsed with pools of overlapping long NPM-ALK-peptides were used to stimulate T-cells in further 22 patients and ten controls. Responsive T-cells were detected in 15 patients and in five controls. A peptide pool located in the middle of the kinase domain induced ALK-reactive T-cells in 14 of 15 responsive patients. We could narrow to single peptides between p327-p370 of NPM-ALK in four patients. In conclusion, using IVT-RNA, 40% of NPM-ALK-positive ALCL-patients in remission had detectable NPM-ALK-specific T-cell responses which were mainly restricted by HLA-B and -C alleles. Peptide stimulation of T-cells revealed responses in almost 70% of patients and allowed describing an immunogenic region located in the ALK-kinase domain.

Evolution of melanoma cross-resistance to CD8+ T cells and MAPK inhibition in the course of BRAFi treatment.

The profound but frequently transient clinical responses to BRAFV600 inhibitor (BRAFi) treatment in melanoma emphasize the need for combinatorial therapies. Multiple clinical trials combining BRAFi and immunotherapy are under way to further enhance therapeutic responses. However, to which extent BRAFV600 inhibition may affect melanoma immunogenicity over time remains largely unknown. To support the development of an optimal treatment protocol, we studied the impact of prolonged BRAFi exposure on the recognition of melanoma cells by T cells in different patient models. We demonstrate that autologous CD8+ tumor-infiltrating lymphocytes (TILs) efficiently recognized short-term (3, 7 days) BRAFi-treated melanoma cells but were less responsive towards long-term (14, 21 days) exposed tumor cells. Those long-term BRAFi-treated melanoma cells showed a non-proliferative dedifferentiated phenotype and were less sensitive to four out of five CD8+ T cell clones, present in the preexisting TIL repertoire, of which three recognized shared antigens (Tyrosinase, Melan-A and CSPG4) and one being neoantigen-specific. Only a second neoantigen was steadily recognized independent of treatment duration. Notably, in all cases the impaired T cell activation was due to a time-dependent downregulation of their respective target antigens. Moreover, combinatorial treatment of melanoma cells with BRAFi and an inhibitor of its downstream kinase MEK had similar effects on T cell recognition. In summary, MAP kinase inhibitors (MAPKi) strongly alter the tumor antigen expression profile over time, favoring evolution of melanoma variants cross-resistant to both T cells and MAPKi. Our data suggest that simultaneous treatment with MAPKi and immunotherapy could be most effective for tumor elimination.

HLA class I loss in metachronous metastases prevents continuous T cell recognition of mutated neoantigens in a human melanoma model.

T lymphocytes against tumor-specific mutated neoantigens can induce tumor regression. Also, the size of the immunogenic cancer mutanome is supposed to correlate with the clinical efficacy of checkpoint inhibition. Herein, we studied the susceptibility of tumor cell lines from lymph node metastases occurring in a melanoma patient over several years towards blood-derived, neoantigen-specific CD8+ T cells. In contrast to a cell line established during early stage III disease, all cell lines generated at later time points from stage IV metastases exhibited partial or complete loss of HLA class I expression. Whole exome and transcriptome sequencing of the four tumor lines and a germline control were applied to identify expressed somatic single nucleotide substitutions (SNS), insertions and deletions (indels). Candidate peptides encoded by these variants and predicted to bind to the patient's HLA class I alleles were synthesized and tested for recognition by autologous mixed lymphocyte-tumor cell cultures (MLTCs). Peptides from four mutated proteins, HERPUD1G161S, INSIG1S238F, MMS22LS437F and PRDM10S1050F, were recognized by MLTC responders and MLTC-derived T cell clones restricted by HLA-A*24:02 or HLA-B*15:01. Intracellular peptide processing was verified with transfectants. All four neoantigens could only be targeted on the cell line generated during early stage III disease. HLA loss variants of any kind were uniformly resistant. These findings corroborate that, although neoantigens represent attractive therapeutic targets, they also contribute to the process of cancer immunoediting as a serious limitation to specific T cell immunotherapy.

Melanoma Lesions Independently Acquire T-cell Resistance during Metastatic Latency.

Melanoma often recurs after a latency period of several years, presenting a T cell-edited phenotype that reflects a role for CD8(+) T cells in maintaining metastatic latency. Here, we report an investigation of a patient with multiple recurrent lesions, where poorly immunogenic melanoma phenotypes were found to evolve in the presence of autologous tumor antigen-specific CD8(+) T cells. Melanoma cells from two of three late recurrent metastases, developing within a 6-year latency period, lacked HLA class I expression. CD8(+) T cell-resistant, HLA class I-negative tumor cells became clinically apparent 1.5 and 6 years into stage IV disease. Genome profiling by SNP arrays revealed that HLA class I loss in both metastases originated from a shared chromosome 15q alteration and independently acquired focal B2M gene deletions. A third HLA class I haplotype-deficient lesion developed in year 3 of stage IV disease that acquired resistance toward dominant CD8(+) T-cell clonotypes targeting stage III tumor cells. At an early stage, melanoma cells showed a dedifferentiated c-Jun(high)/MITF(low) phenotype, possibly associated with immunosuppression, which contrasted with a c-Jun(low)/MITF(high) phenotype of T cell-edited tumor cells derived from late metastases. In summary, our work shows how tumor recurrences after long-term latency evolve toward T-cell resistance by independent genetic events, as a means for immune escape and immunotherapeutic resistance. Cancer Res; 76(15); 4347-58. ©2016 AACR.

Exome Sequencing to Predict Neoantigens in Melanoma.

The ability to use circulating peripheral blood cells and matched tumor sequencing data as a basis for neoantigen prediction has exciting possibilities for application in the personalized treatment of cancer patients. We have used a high-throughput screening approach, combining whole-exome sequence data, mRNA microarrays, and publicly available epitope prediction algorithm output to identify mutated proteins processed and displayed by patient tumors and recognized by circulating immune cells. Matched autologous melanoma cell lines and peripheral blood mononuclear cells were used to create mixed lymphocyte tumor cell cultures, resulting in an expansion of tumor-reactive T cells to use for mutated peptide screening. Five patients were investigated, three of whom had a durable complete response (CR; 15+ years) in an autologous melanoma-pulsed dendritic cell clinical trial. We identified seven mutated antigens in total that stimulated T-effector memory cells in two of the five patients. While the procedure did not result in clinically applicable neoantigens for all patients, those identified were likely important in tumor clearance, leading to durable CR. The nature of the screening process allows results to be obtained rapidly and is easily applicable to a wide variety of different tumor types.

Melanomas resist T-cell therapy through inflammation-induced reversible dedifferentiation.

Adoptive cell transfer therapies (ACTs) with cytotoxic T cells that target melanocytic antigens can achieve remissions in patients with metastatic melanomas, but tumours frequently relapse. Hypotheses explaining the acquired resistance to ACTs include the selection of antigen-deficient tumour cell variants and the induction of T-cell tolerance. However, the lack of appropriate experimental melanoma models has so far impeded clear insights into the underlying mechanisms. Here we establish an effective ACT protocol in a genetically engineered mouse melanoma model that recapitulates tumour regression, remission and relapse as seen in patients. We report the unexpected observation that melanomas acquire ACT resistance through an inflammation-induced reversible loss of melanocytic antigens. In serial transplantation experiments, melanoma cells switch between a differentiated and a dedifferentiated phenotype in response to T-cell-driven inflammatory stimuli. We identified the proinflammatory cytokine tumour necrosis factor (TNF)-α as a crucial factor that directly caused reversible dedifferentiation of mouse and human melanoma cells. Tumour cells exposed to TNF-α were poorly recognized by T cells specific for melanocytic antigens, whereas recognition by T cells specific for non-melanocytic antigens was unaffected or even increased. Our results demonstrate that the phenotypic plasticity of melanoma cells in an inflammatory microenvironment contributes to tumour relapse after initially successful T-cell immunotherapy. On the basis of our work, we propose that future ACT protocols should simultaneously target melanocytic and non-melanocytic antigens to ensure broad recognition of both differentiated and dedifferentiated melanoma cells, and include strategies to sustain T-cell effector functions by blocking immune-inhibitory mechanisms in the tumour microenvironment.

Acute myeloid leukemia (AML)-reactive cytotoxic T lymphocyte clones rapidly expanded from CD8(+) CD62L((high)+) T cells of healthy donors prevent AML engraftment in NOD/SCID IL2Rgamma(null) mice.

OBJECTIVE: Current in vitro techniques for isolating leukemia-reactive cytotoxic T lymphocytes (CTLs) from healthy donors are of relatively low efficiency and yield responder populations with unknown biological significance. This study aimed at the development of a more reliable approach, allowing generation and expansion of acute myeloid leukemia (AML)-reactive CTLs using primary in vitro stimulation. MATERIALS AND METHODS: We established allogeneic mini-mixed lymphocyte-leukemia cultures (mini-MLLCs) by stimulating donor CD8(+) T cells with human leukocyte antigen (HLA) class I-matched AML blasts in microtiter plates. Before culture, CD8(+) T cells were separated into CD62L((high)+) and CD62L((low)+/neg) subsets enriched for naive/central memory and effector memory cells, respectively. RESULTS: In eight different related and unrelated donor/AML pairs, numerous CTL populations were isolated that specifically lysed myeloid leukemias in association with various HLA-A, -B, or -C alleles. These CTLs expressed T-cell receptors of single Vbeta-chain families, indicating their clonal origin. The majority of CTL clones were obtained from mini-MLLCs initiated with CD62L((high)+) cells. Using antigen-specific stimulation, multiple CTL populations were amplified to 10(8)-10(10) cells within 6 to 8 weeks. Three of four representative CTL clones were capable of completely preventing engraftment of human primary AML blasts in nonobese diabetic/severe combined immune deficient IL2Rgamma(null) mice. CONCLUSION: The mini-MLLC approach allows the efficient in vitro expansion of AML-reactive CTL clones from CD8(+)CD62L((high)+) precursors of healthy donors. These CTLs can inhibit leukemia engraftment in immunodeficient mice, suggesting their potential biological relevance.

Inhibitory effect of RNA pool complexity on stimulatory capacity of RNA-pulsed dendritic cells.

Tumor cells that show downregulation of their tumor-associated antigens (TAAs) may be able to escape immune-mediated elimination. Therefore, efficient vaccine strategies attempt to target multiple TAAs simultaneously. This is easily achieved in dendritic cell (DC)-based vaccines by introducing antigens in the form of RNA. Although insufficient message may hinder adequate expression of individual TAAs when using total-tumor RNA, high amounts of individual RNAs as pools yield DCs presenting high numbers of specific peptide-major histocompatibility complex ligands with epitopes derived from different TAAs. We used the transfer of RNAs encoding the well-defined melanoma TAAs tyrosinase, Melan-A, CDK4mut, gp100, SNRP116mut, and GPNMBmut to characterize DCs at the levels of transfected RNA, expressed protein and peptide-major histocompatibility complex ligand presentation. TAA-encoding RNA was rapidly degraded in the DCs, allowing only a single surge in protein expression shortly after transfection. We compared the functional capacity of DCs transfected with pools of 3 versus 6 RNAs. Whereas functional assays demonstrated a decrease in stimulatory capacity of DCs transfected with a pool of 3 RNAs by only 30% as compared with single RNAs, a 60% loss was seen with 6 RNAs. We conclude that larger RNA pools result in diminished presentation of individual epitopes and suggest that smaller pools of RNA be transfected into separate DC populations which are then pooled to create multiplex vaccines.

Dissection and molecular analysis of alloreactive CD8+ T cell responses in allogeneic haematopoietic stem cell transplantation.

We applied a cDNA expression screening procedure with cryopreserved non-clonal CD8+ T cell populations (Lennerz et al., Proc. Natl. Acad. Sci. USA 102:16013-8, 2005) to the identification of candidate antigens for graft-versus-host disease (GvHD) and graft-versus-leukaemia (GvL) effects in allogeneic haematopoietic stem cell transplantation (allo-HSCT). In a patient-donor model system with HLA class I disparities, we identified an HLA-B*44 mismatch allele, HLA-B*4405, as the dominant target of alloreactive T cells expanded in vitro from donor peripheral blood mononuclear cells (PBMC). HLA-B*4405-reactive T cells were detectable after multiple in vitro stimulations in the patient's post-HSCT PBMC. In a patient-donor model with full HLA compatibility, the major target antigen of donor lymphocytes stimulated in vitro with the respective patient's pre-HSCT PBMC was restricted by HLA-A*0201 and was encoded by TRIM22-442 C, a newly detected polymorphic allele of the tripartite motif family member TRIM22 (synonym: STAF50), preferentially expressed in cells of the haematopoietic system. An arginine(R)-to-cysteine(C) exchange at position 442 generated an immunogenic T cell epitope equivalent to a minor histocompatibility antigen (mHag). TRIM22-442C-specific T cells persisted long-term in the patient's post-HSCT PBMC. Approximately, 1.3% of Caucasians carry TRIM22.442 C in association with HLA-A*0201. In particular, the knowledge of a large and diverse panel of such mHags may be crucial for further improvement of donor selection and adoptive T cell transfer strategies. The procedure applied herein will help to accelerate and facilitate their identification.

An open-label, prospective phase I/II study evaluating the immunogenicity and safety of a ras peptide vaccine plus GM-CSF in patients with non-small cell lung cancer.

Mutations of the ras gene have been reported in 20-40% of NSCLC patients. If present, they are critical for the malignant phenotype of these tumors. Therefore, targeting them by specific vaccination is a promising therapeutic approach. In a clinical trial we screened for ras mutations in patients with NSCLC. Patients with ras-positive tumors were immunized six times intradermally with a mixture of seven peptides representing the most common ras mutations. Objectives of the study were the feasibility, efficacy and safety of the vaccination. In addition, the induction of a specific immune reaction was investigated by DTH tests, and the induction of peptide-specific T cells was tested in ex vivo IFN-gamma-ELISPOT assays. Five of 18 patients had ras mutations at codon 12. Four of these patients, all with adenocarcinomas (stage I: n=3, stage IV: n=1) entered the study. The patient with stage IV disease withdrew prematurely after the third application because of disease progression associated with pulmonary embolism. Ras-specific T cells were not detected ex vivo. However, one patient developed a positive DTH reaction after the fifth vaccination that increased after the sixth vaccination. Our results are in line with earlier trials reporting ras mutations in 20-40% of NSCLC patients. Vaccination with mutated ras peptides is feasible and well tolerated. One patient revealed a positive DTH test. An ex vivo detectable T cell response was not induced in any of the patients.

Rapid identification of an HLA-B*1501-restricted vaccinia peptide antigen.

We identified a modified vaccinia virus Ankara (MVA)-peptide recognized by T cells of a vaccinated patient, applying a modified expression-based procedure. CD8(+) T cells reactive with MVA were expanded from peripheral blood of a patient after MVA-vaccination. The restricting HLA-elements and the antigen were determined applying stably HLA-class I-transfected K562 cells that were either infected wit MVA or transfected with a panel of MVA open reading frames (ORF). The T cells recognized the ORF 28R (K7R) gene product in association with HLA-B*1501 and the peptide-coding region was localized applying truncated in vitro transcribed mRNA. The 9-mer peptide encoded (ORF 28(25-33), SIIDLIDEY) was identified that was also recognized by ex vivo CD8(+) T cells from the patient and further healthy individuals.

A neoepitope generated by an FLT3 internal tandem duplication (FLT3-ITD) is recognized by leukemia-reactive autologous CD8+ T cells.

The FLT3 receptor tyrosine kinase is expressed in more than 90% of acute myelogeneous leukemias (AMLs), up to 30% of which carry an internal tandem duplication (ITD) within the FLT3 gene. Although varying duplication sites exist, most FLT3-ITDs affect a single protein domain. We analyzed the FLT3-ITD of an AML patient for encoding HLA class I-restricted immunogenic peptides. One of the tested peptides (YVDFREYEYY) induced in vitro autologous T-cell responses restricted by HLA-A*0101 that were also detectable ex vivo. These peptide-reactive T cells recognized targets transfected with the patient's FLT3-ITD, but not wild-type FLT3, and recognized the patient's AML cells. Our results demonstrate that AML leukemic blasts can in principle process and present immunogenic FLT3-ITD neoepitopes. Therefore, FLT3-ITD represents a potential candidate target antigen for the immunotherapy of AML.

Rapid molecular dissection of viral and bacterial immunomes.

The development of preventive or therapeutic recombinant vaccines and the generation of serodiagnostic assays for infectious diseases depend essentially on the availability of molecularly defined antigens. A major bottleneck for the identification of suitable target antigens for many pathogens is the isolation of sufficient amounts of material for subsequent genomic or proteomic screening. Applying a highly efficient expression cloning strategy to the human pathogens vaccinia virus (VV) and Chlamydia pneumoniae (CP), we demonstrate that sub-nanogram amounts of isolated nucleic acids can be utilized to determine comprehensive sets of immunodominant antigens. Remarkably, the approach not only confirmed the immunogenicity of previously reported antigens but also disclosed novel vaccine candidates conserved in orthopoxviruses, including antigenic envelope proteins and immunodominant CTL epitopes. Moreover, as illustrated for CP infection, we show that a panel of novel antigens can be readily selected from the initially discovered pool to build up pathogen-specific seroassays. The established approach is rapid, making it an attractive procedure for the comprehensive dissection of immunomes of known human pathogens and newly emerging infectious agents.

Proteasome-inhibited dendritic cells demonstrate improved presentation of exogenous synthetic and natural HLA-class I peptide epitopes.

The design and successful clinical implementation of cancer vaccines targeting the induction of T-cell mediated immunity is a rapidly evolving field that is hampered by an empirical selection of antigen and adjuvant. In particular, vaccines using defined tumor-associated peptide epitopes elicit only a restricted T-cell repertoire in a minority of patients. In this regard, vaccines comprising the whole spectrum of antigens presented by individual autologous tumors would be advantageous. In an in vitro model, we evaluated the capacity of naturally processed Epstein-Barr virus-transformed B-lymphoblastoid-cell line (LCL)-derived peptides to activate virus-specific CD8+ T cells of seropositive healthy individuals. While bulk peptides obtained by mild acid elution from LCL contained multiple T-cell epitopes, this complex mixture of peptides was poorly immunogenic, even when presented by mature dendritic cells (DC). Pretreatment of DC with proteasome inhibitors strongly enhanced the immunogenicity of single viral synthetic as well as bulk LCL peptides. This was most likely achieved by facilitating the loading of exogenous epitopes onto DC-associated HLA-class I complexes in the face of significant inter-peptide competition for such loading. Our results suggest that proteasome inhibitors may be used to increase the antigenicity of mature DC pulsed with exogenous synthetic or naturally processed peptide epitopes in vaccination trials.