T-cell Receptor Rearrangement Research Articles

Clinicopathological and molecular genetic alterations in monomorphic–epitheliotropic intestinal T-cell lymphoma of the small intestine

BackgroundSmall intestinal monomorphic–epitheliotropic intestinal T-cell lymphoma (MEITL) is a rare aggressive T-cell lymphoma originating in the gastrointestinal tract. This study aimed to investigate the clinicopathological features, immunophenotypes, and molecular genetic changes of MEITL.MethodsThe clinicopathological data for three patients with surgically resected MEITL of the small intestine were collected. Next, immunohistochemical labeling, Epstein–Barr virus (EBV) in situ hybridization, assessment of clonal rearrangement of T-cell receptor (TCR) genes, and next-generation sequencing (NGS) were performed.ResultsOf the three patients, two were male and one was female, with ages of 61, 67, and 73 years, respectively. Clinical manifestations were predominantly abdominal pain and distension. Histopathology revealed infiltrative growth of small-to-medium-sized lymphocytes with a consistent morphology between the intestinal walls, accompanied by an obvious pro-epithelial phenomenon. The expression of CD3, CD8, CD43, CD56, TIA-1, CD103, H3K36me3, and Bcl-2 was detected, and the Ki-67 proliferation index ranged from 50% to 80%. All three patients tested negative for EBER. However, monoclonal rearrangement of the TCR gene was detected in them. NGS testing showed a JAK3 mutation in all three cases. Further, STAT5B, SETD2, and TP53 mutations were each observed in two cases, and a BCOR mutation was found in one case. All patients were treated with chemotherapy after surgery. Two patients died 7 and 15 month post-operation, and one patient survived for 5 months of follow-up.ConclusionsOur findings demonstrate that mutations in JAK3 and STAT5B of the JAK/STAT pathway and inactivation of the oncogene SETD2 markedly contribute to the lymphomagenesis of MEITL.

Peripheral T cell lymphoma initially presenting in lung biopsies: A diagnostic challenge

BackgroundPrimary or secondary pulmonary involvement by peripheral T cell lymphoma (PTCL) is rare and difficult to diagnose particularly via lung biopsies. Methods22 cases of PTCL diagnosed initially in lung biopsies between January 2006 and November 2020 were retrospectively reviewed followed at Nanjing Drum Tower Hospital and the First Affiliated Hospital of Zhengzhou University, respectively, including clinical manifestations, baseline biochemical indexes, images, histological findings and other available ancillary studies such as immunostaining, Epstein-Barr virus encoded RNA (EBER) in situ hybridization and T-cell receptor rearrangement analysis upon diagnosis. ResultsThe median age of these patients was 59 years old (range: 29–82 years) at diagnosis. The majority of them complained of fever, cough and fatigue. Computed tomography scans mainly revealed multiple ill-defined nodules/masses of various sizes and densities with or without air bronchogram. Microscopically, most lesions showed lymphoid cells with clear cytoplasm and irregular nuclear contours diffusely infiltrating alveolar septa or alveolar spaces in an inflammatory background. Several cases had a predominance of small neoplastic cells (n = 4) with atypical, irregular nuclei. One case showed a diffuse monotonous pattern of growth. Angioinvasion and necrosis were not uncommon findings. The neoplastic cells in all cases were positive for one or more T-cell markers, and negative for B-cell-lineage antigens and EBER. 19 out of 22 patients had complete follow-up information, and 17 patients were dead at the last follow-up. ConclusionsPulmonary involvement by PTCL is rare with dismal outcome. Aggressive clinical course and several clinicopathologic clues, albeit unspecific, may alert the pathologists of the possibilities of pulmonary PTCLs.

Thymic NK-Cells and Their Potential in Cancer Immunotherapy.

Natural killer (NK)-cells are innate immune cells with potent anti-tumor capacity, capable of recognizing target cells without prior exposure. For this reason, NK-cells are recognized as a useful source of cell therapy. Although most NK-cells are derived from the bone marrow (BM), a separate developmental pathway in the thymus also exists, producing so-called thymic NK-cells. Unlike conventional NK-cells, thymic NK (tNK)-cells have a combined capacity for cytokine production and a natural ability to kill tumor cells in the presence of NK-cell receptor stimulatory ligands. Furthermore, tNK-cells are reported to express CD3 subunits intracellularly, without the presence of a rearranged T-cell receptor (TCR). This unique feature may enable harnessing of these cells with a TCR to combine NK- and T-cell effector properties in one cell type. The development, phenotype, and function of tNK-cells, and potential as a cell therapy is, however, poorly explored. In this review, we provide an overview of current literature on both murine and human tNK-cells in comparison to conventional BM-derived NK-cells, and discuss the potential applications of this cellular subset in the context of cancer immunotherapy.

Clonal haematopoiesis: A common progenitor for cytotoxic peripheral T-cell lymphoma and angioimmunoblastic T-cell lymphoma.

Recent studies have shown that follicular helper T-cell lymphoma of angioimmunoblastic type (AITL), the most common nodal peripheral T-cell lymphoma (PTCL), frequently arises in a background of clonal haematopoiesis (CH), a preneoplastic condition affecting up to 40% of elderly individuals. Data on a potential CH association are limited for other PTCL. We report a unique patient who sequentially developed both cytotoxic PTCL, not otherwise specified and AITL with distinct T-cell receptor rearrangements but shared somatic mutations originating from the same CH clone, thus providing convincing evidence that CH can give rise to T-cell neoplasms of different lineage.

Application of Blood Lymphocyte Immunophenotype and TCR Gene Rearrangement in the Diagnosis of CTCL.

The immunophenotype of peripheral blood lymphocytes and T-cell receptor (TCR) gene rearrangement of cutaneous T cell lymphoma (CTCL) patients were retrospectively analyzed to explore their value in the diagnosis of CTCL. A total of fifty patients' results were enrolled from 2013 to 2021, including 29 malignant skin disorders and 21 benign skin disorders. The immunophenotype of peripheral blood lymphocytes were analyzed by flow cytometry and TCR gene rearrangement was detected by capillary electrophoresis. Lymphocyte subsets, CD4/CD8 ratio, the percentage of CD3+CD4+CD7- cells and CD45RA/CD45RO ratio was calculated between malignant and benign skin disorders. Peripheral blood lymphocyte immunophenotype and TCR gene rearrangement was compared with skin biopsy to evaluate their sensitivity and specificity. Lymphocyte subsets between malignant and benign groups have no significant difference in percentage of T cell (p > 0.05). The CD4/CD8 ratio is higher in patients with malignant lymphoma than the healthy range. The percentage of CD3+CD4+CD7- cells in malignant groups is higher than that in benign groups and CD45RA/ CD45RO ratio has significant difference between malignant and benign groups (p < 0.05). The sensitivity and specificity of TCR rearrangement for CTCL were 51.7% and 42.9%. The sensitivity and specificity of peripheral blood lymphocyte immunophenotype for CTCL were 44.8% and 33.3%. Combining the two methods, the sensitivity and specificity reached 69.0% and 38.1%, respectively. CD4/CD8 ratio of lymphocyte subsets, the proportion of CD4+CD7-T cells and CD45RA/CD45RO ratio can effectively distinguish benign and malignant dermatosis. TCR rearrangement method combined with lymphocyte immunophenotype can improve the sensitivity and specificity of CTCL diagnosis.

Genomic, Transcriptional, and Immunological Validation of Distinct Molecular Subtypes of Classic Hodgkin Lymphoma through Tissue-Based and Noninvasive Methods

Introduction: The scarcity of malignant Hodgkin and Reed-Sternberg (HRS) cells has hampered comprehensive genomic profiling of classic Hodgkin lymphoma (cHL) from tumor tissue. Multiple recent studies have demonstrated that plasma cfDNA profiling facilitates molecular characterization of cHL. Leveraging noninvasive genotypes and Latent Dirichlet Allocation, we recently defined 2 genetic cHL subtypes in a large international cohort comprising 366 patients including pediatric and adult patients of all ages (Alig et al., ASH 2022 and ICML 2023). Cluster H1 comprised ~2/3 of cases and was dominated by a high somatic mutational burden, and non-silent mutations in genes canonically involved in NF-κB, JAK/STAT and PI3K signaling as well as in B2M. Conversely, cluster H2 (~1/3 of cases) was primarily characterized by recurrent somatic copy number aberrations as well as mutations in TP53 and KMT2D. Herein, we validate these previously identified genetic subtypes in external datasets as well as through orthogonal methods including tissue-based and noninvasive transcriptional and immune profiling. Methods: To validate genetic cHL subtypes, we first leveraged public cHL genotypes from 61 patients obtained through whole genome/exome sequencing (WGS/WES) of flow-sorted HRS cells (Maura et al, Blood Cancer Disc. 2023). Using our previously locked down probabilistic classifier, we assigned the H1/H2 subtype, and then correlated cluster assignments with clinical variables. To explore transcriptional differences between genetic subtypes, we profiled baseline plasma samples (n=113) from the larger plasma genotyping cohort (n=293) using EPIC-Seq (Esfahani et al, Nat Biotechnol 2022), which allows for noninvasive gene expression profiling from cfDNA fragmentation patterns at transcription start sites. Further, we used SABER (Sworder, Cancer Cell 2023) to enumerate T-cell receptor (TCR) rearrangements in cfDNA (cfTCR, n=292). Finally, to assess subtype-specific immune infiltrate patterns, we profiled cHL tumor specimens using RNA-Seq (n=64), and applied CIBERSORTx. Results: Similar to observations in our cfDNA discovery cohort, H1 was found to be the more prevalent subtype in the external validation set comprising 56% of tumors, while 44% were classified as H2. Recurrence frequencies of genetic features were comparable to and significantly correlated with those from our plasma discovery cohort ( R S=0.59 [H1] and R S=0.63 [H2], P&amp;lt;0.001 each). Of note, when considering the whole genome space, the higher mutational burden of H1 tumors could be confirmed ( P&amp;lt;0.01), and this association was independent of the tumor EBV status. In agreement with the discovery cohort, the bimodal age distribution and increased EBV positivity of the H2 subtype could also be recapitulated (31% vs 6% EBV+, P&amp;lt;0.01). To explore transcriptional differences between H1/H2 subtypes, we took advantage of the plasma enrichment of HRS cell ctDNA and utilized EPIC-Seq to noninvasively infer expression of 1,676 targeted genes. Tracking signatures derived from scRNA-Sequencing in plasma samples, we found that both HRS cells and the cHL tumor microenvironment can be successfully profiled by EPIC-Seq. Strikingly, we found substantial enrichment of a cytokine response signature in H1 tumors, while T-cell activation was among the top upregulated signatures in H2 tumors ( Fig. A). Importantly, the T-cell signature found in H2 was accompanied by a higher abundance of T-cell clones as quantified by SABER in baseline plasma samples ( P&amp;lt;0.001, Fig. B). Notably, cfTCR fragment length profiles resembled the mutant ctDNA profiles, strongly suggesting a tumor origin of the TCR rearrangements detected in plasma. Lastly, immune cell deconvolution of bulk RNA-Seq specimens indicated a higher abundance of CD8+ T-cells in H2 tumors ( P&amp;lt;0.01), further confirming our prior observations. Conclusions: Collectively, these results serve to validate H1 and H2 as distinct cHL subtypes, to confirm the characteristic genotypes defining them, and recapitulate their distinctive associations with key clinical and pathological variables including age and EBV status. We further validate the subtypes using orthogonal methods revealing dominant cytokine driven signaling in H1. Conversely, H2 tumors, which largely lack B2M mutations, despite their lower mutational burden, are rather immunogenic triggering T-cell responses.

Venetoclax and Blinatumomab for Adult Patients with Relapsed/Refractory or MRD Positive Ph-Negative B-Precursor ALL: First Results of the GMALL-Bliven Trial

Introduction Prognosis of adult patients with relapsed/refractory (R/R) B-precursor acute lymphoblastic leukemia (BCP-ALL) remains poor. Monotherapy with Blinatumomab in ALL induced a complete remission (CR) in 44% of patients and measurable residual disease (MRD) negative molecular remission (MOL-CR) in 33%. Median overall survival of 7.7 months remains unsatisfactory. In the MRD setting, median survival was 36 months in the context of subsequent allogeneic stem cell transplantation (SCT). The combination of Blinatumomab with Venetoclax may be an effective option in ALL. Objectives In this multicenter phase 1 clinical trial the GMALL study group evaluates the safety of Blinatumomab in combination with Venetoclax in R/R or MRD positive BCP-ALL (NCT05182385). Using RNA sequencing, functional intracellular BH3 profiling, T cell immunomonitoring and effector cell cytotoxicity assays we aim to further elucidate synergy of this combination. Methods The BLIVEN trial includes patients with CD19-positive Ph-negative BCP-ALL aged 18 years and older, with no upper age limit. Eligible patients had either R/R ALL (bone marrow blasts &amp;gt;5%) or molecular failure/relapse (MRD &amp;gt;1xE-04). To assess safety, we determined maximum tolerated dose (MTD) as primary endpoint of the phase I part of the trial as designated recommended phase 2 dose (RP2D). Key secondary endpoint was the MOL-CR rate. Treatment consisted of oral Venetoclax in continuous dosing on day -7 to day 42 of target doses ranging between 200-800 mg once daily, and Blinatumomab as continuous intravenous infusion of 28 µg/d 4 weeks on and 2 weeks off, starting on day 1. For patients with R/R ALL, a cautionary dose step of 9 µg/d Blinatumomab was implemented for one week. MRD was analyzed in the reference laboratory using real-time quantitative PCR (RQ-PCR) of immunoglobulin and T-cell receptor (IG/TR) rearrangements. Results Between February 2022 and May 2023 a total of 7 patients were enrolled in the phase I part at four German centers (Figure 1). Venetoclax target doses were 400 mg (n=3), 600 mg (n=3), and 800 mg (n=1). Median age was 48.5 years (range 22 - 72 years). MRD assessment was available in 7/7 patients. Molecular BCP-ALL subtypes were identified by RNA sequencing in 5/5 analyzed patients, including ZNF384-rearranged ALL (n=2), BCR::ABL1-like (n=2; IGH::CRLF2 rearranged), and KMT2A-rearranged ALL (n=1). Three of seven patients were treated for hematological relapse, while 4/7 patients had molecular failure/relapse at time of enrolment. Among patients with R/R ALL, 2/3 were refractory to front-line therapy with intensive GMALL induction/consolidation therapy, while 1/3 suffered relapse shortly after failure of second allogeneic SCT. CTCAE grade IV neutropenia was identified as adverse reaction related to Venetoclax in one patient. Neutropenia resolved before dose limiting toxicity (DLT) evaluation time (i.e. 42 days after Venetoclax initiation). Overall, no DLT was identified throughout the trial and MTD was not reached. No treatment interruption was noted during cycle 1. Two of seven patients received one treatment cycle of BLIVEN only due to treatment failure, 5/7 patients received two treatment cycles. Response assessment was available for 7/7 patients. Treatment with Blinatumomab/Venetoclax of R/R ALL resulted in CR in 1/3 patients, with the responding patient showing a MOL-CR. The MOL-CR rate in molecular failure/relapse patients was 3/4. Conclusion Salvage therapy with Blinatumomab and Venetoclax exhibited good tolerability without treatment-related mortality. No treatment withdrawals were attributed to safety concerns. Two patients did not respond to BLIVEN combination therapy. Interestingly, both patients exhibited IGH::CRLF2 fusion transcripts.The remaining 5 patients obtained MRD responses, including complete MRD responses, of which 2/2 occurred in ZNF384 rearranged BCP-ALL. Further follow-up and larger patient numbers are needed to establish the potential benefit of this regimen in molecular driver subtypes of BCP-ALL. Enrollment to complete phase I of the BLIVEN trial is currently ongoing. Updated results including RP2D will be presented at the meeting. Acknowledgments This is an independent academic early phase I clinical trial conducted under the sponsor role of the Goethe University, Frankfurt, Germany. It received financial support and supply of Venetoclax by AbbVie Inc..

Clinical Features and Outcomes in Large Granular Lymphocyte Leukemia-Associated Pure Red Cell Aplasia with STAT3 Mutation

Background Large granular lymphocyte leukemia (LGLL) is a rare disease frequently complicated with pure red cell aplasia (PRCA) [1, 2]. STAT3 mutations have been describled in 30-40% of LGLL patients [3]. The aim of this work was to evaluate whether STAT3 mutations might be associated with specific clinical features and outcomes in LGLL-associated PRCA. Methods and results From January 2016 to July 2023, 81 patients with LGLL-associated PRCA were enrolled in the China Eastern Cooperation Group for Anemia (CECGA) database (ChiCTR2100043485). As an initial step in the STAT3 mutational analysis, we screened all patients with Sanger sequencing or Next-generation sequencing (NGS). The initial dose of CsA was 3-5mg/kg/day, and the serum concentration was adjusted to be 150-200ng/mL based on adverse reactions. After 12 months of maintenance, the dosage was slowly reduced. Cyclophosphamide combined with prednisone (CP) regimen was used as a salvage therapy for patients who failed to CsA. The initial dose of cyclophosphamide and prednisone were 100mg/day and 0.5-1mg/kg/day, respectively. Among the 81 cases, 26% of them were positive for STAT3 mutations. The clinical characteristics of patients with or without STAT3 mutation were summarized in Table 1. Patients with STAT3 mutations had a higher reticulocyte percentage (0.88% vs 0.28%, P=0.039) and red cell distribution width-coefficient of variation (18.8% vs 15.8%, P=0.008) than patients without STAT3 mutations. Y640F mutation were found in 9 of 21 cases. Subgroup analysis showed that patients with Y640F mutation were associated with younger age (44 vs 65 years old, P=0.007) and higer lymphocyte percentage in peripheral blood (63.7% vs 34.4%, P=0.033). Deep sequencing of rearranged T-cell receptor Vβ complementarity-determining region 3 by NGS was conducted in 61 patients. The predominant V-gene of LGLL clonotypes belonged to the TRBV06 family gene was detected in 12 (25%) patients. The expression of TRBV06 family gene was a litter lower in patients with STAT3 mutation than non-mutant groups (8% vs 31%, P=0.189). The complete response rate (CRR) [31% (5/16) vs 33% (19/58), P=0.909] and overall response rate (ORR) [56% (9/16) vs 50% (29/58), P=0.658] of cyclosporine (CsA) treatment were similar in patients with STAT3 mutations or not. In STAT3 mutant group, the CRR [54% (7/13) vs 31% (5/16), P=0.274] and ORR [85% (11/13) vs 56% (9/16), P=0.130] of CP regimen tended to be better than CsA . 6 patients (67%) relapsed among the 9 patients who responded to CsA in STAT3 mutant group. In patients without STAT3 mutation, 19 of 29 (66%) CsA-responders relapsed. There was no siginificant difference in the relapse-free survival between the two group (Figure 1). Discussion/Conclusions In summary, STAT3 mutation was frequently recognized in LGLL-associated PRCA, and the hotspot site was Y640F. Patients with STAT3 mutations responded to CsA as well as those without the mutation. CP regimen could be used as a salvage therapy for patients who failed to CsA. Reference 1. Balasubramanian SK, Sadaps M, Thota S, et al. Rational management approach to pure red cell aplasia. Haematologica. 2018, 103(2): 221-230. 2. Wu X, Cheng L, Liu X, et al. Clinical characteristics and outcomes of 100 adult patients with pure red cell aplasia. Ann Hematol. 2022, 101(7):1493-1498. 3. Barilà G, Teramo A, Calabretto G, et al. Stat3 mutations impact on overall survival in large granular lymphocyte leukemia: a single-center experience of 205 patients. Leukemia. 2020, 34: 1116-1124.

Flow Sorting, Whole Genome Amplification and Next-Generation Sequencing as Combined Tools to Study Heterogeneous Acute Lymphoblastic Leukemia.

Next-generation sequencing (NGS) methods have been introduced for immunoglobulin (IG)/T-cell receptor (TR) gene rearrangement analysis in acute lymphoblastic leukemia (ALL) and lymphoma (LBL). These methods likely constitute faster and more sensitive approaches to analyze heterogenous cases of ALL/LBL, yet it is not known whether gene rearrangements constituting low percentages of the total sequence reads represent minor subpopulations of malignant cells or background IG/TR gene rearrangements in normal B-and T-cells. In a comparison of eight cases of B-cell precursor ALL (BCP-ALL) using both the EuroClonality NGS method and the IdentiClone multiplex-PCR/gene-scanning method, the NGS method identified between 29% and 139% more markers than the gene-scanning method, depending on whether the NGS data analysis used a threshold of 5% or 1%, respectively. As an alternative to using low thresholds, we show that IG/TR gene rearrangements in subpopulations of cancer cells can be discriminated from background IG/TR gene rearrangements in normal B-and T-cells through a combination of flow cytometry cell sorting and multiple displacement amplification (MDA)-based whole genome amplification (WGA) prior to the NGS. Using this approach to investigate the clonal evolution in a BCP-ALL patient with double relapse, clonal TR rearrangements were found in sorted leukemic cells at the time of second relapse that could be identified at the time of diagnosis, below 1% of the total sequence reads. These data emphasize that caution should be exerted when interpreting rare sequences in NGS experiments and show the advantage of employing the flow sorting of malignant cell populations in NGS clonality assessments.

A significant proportion of classic Hodgkin lymphoma recurrences represents clonally unrelated second primary lymphoma

AbstractDespite high cure rates in classic Hodgkin lymphoma (cHL), relapses are observed. Whether relapsed cHL represents second primary lymphoma or an underlying T-cell lymphoma (TCL) mimicking cHL is underinvestigated. To analyze the nature of cHL recurrences, in-depth clonality testing of immunoglobulin (Ig) and T-cell receptor (TCR) rearrangements was performed in paired cHL diagnoses and recurrences among 60 patients, supported by targeted mutation analysis of lymphoma-associated genes. Clonal Ig rearrangements were detected by next-generation sequencing (NGS) in 69 of 120 (58%) diagnoses and recurrence samples. The clonal relationship could be established in 34 cases, identifying clonally related relapsed cHL in 24 of 34 patients (71%). Clonally unrelated cHL was observed in 10 of 34 patients (29%) as determined by IG-NGS clonality assessment and confirmed by the identification of predominantly mutually exclusive gene mutations in the paired cHL samples. In recurrences of >2 years, ∼60% of patients with cHL for whom the clonal relationship could be established showed a second primary cHL. Clonal TCR gene rearrangements were identified in 14 of 125 samples (11%), and TCL-associated gene mutations were detected in 7 of 14 samples. Retrospective pathology review with integration of the molecular findings were consistent with an underlying TCL in 5 patients aged >50 years. This study shows that cHL recurrences, especially after 2 years, sometimes represent a new primary cHL or TCL mimicking cHL, as uncovered by NGS-based Ig/TCR clonality testing and gene mutation analysis. Given the significant therapeutic consequences, molecular testing of a presumed relapse in cHL is crucial for subsequent appropriate treatment strategies adapted to the specific lymphoma presentation.

Newborn Screening for Severe Combined Immunodeficiency

Newborn screening (NBS) for Severe Combined Immunodeficiency (SCID) has been successfully implemented in all 50 United States and Puerto Rico from 2008-2018. This life-saving screening tool has drastically improved overall survival of babies diagnosed with SCID from 74% to 96%. TREC is a stable, circular DNA molecule that is produced during the process of T-cell receptor (TCR) rearrangement and is the target of the quantitative PCR screen on Guthrie cards. Low TRECs are a marker of low naive T cell numbers. This new screening process has facilitated discovery of new genes that cause SCID, new data on patients with SCID, as well as other causes of infant lymphopenia. This new information has prompted the Primary Immune Disease Treatment Consortium to re-classify the diagnosis of SCID in 2022. Providers who are first recipients of a positive screen must understand laboratory methods of the screen, treatment recommendations and options for those with SCID as well as other relevant causes of a positive screen such as 22q11 syndrome, Ataxia Telangiectasia, prematurity. These topics are crucial to cover when reporting results to a family who is receiving unexpected news on their otherwise well appearing newborn. Prompt medical evaluation and prophylaxis have been shown to improve survival and outcomes, and providers play an essential role in relaying this information and care to families. While TREC screen has proven to be a valuable screening tool for conditions with lymphopenia, over 500 immune deficiency diseases exist, and expansion to include these diseases on the NBS could be possible with Next Generation Sequencing in the future.

ScRNA-seq revealed the special TCR β & α V(D)J allelic inclusion rearrangement and the high proportion dual (or more) TCR-expressing cells

Allelic exclusion, one lymphocyte expresses one antigen receptor, is a fundamental mechanism of immunological self-tolerance and highly specific immune responses to pathogens. However, the phenomenon of V(D)J allelic inclusion (incomplete allelic exclusion or allelic escape) rearrangement and dual TCR T cells have been discovered by multiple laboratories. Despite continuous new discoveries, the proportion and underlying mechanism of dual TCR has been puzzling immunologists. In this study, we observed the presence of single T cells expressing multiple TCR chains in all samples, with the proportion of 15%, 10%, and 20% in the human thymus, human peripheral blood, and mouse lymphoid organs, respectively. The proportion of T cells possessing multiple T-cell receptors (TCR) varied significantly in different physiological states and developmental stages. By analyzing RSS category, RSS direction, and V(D)J gene position at TR locus of T cells which contain multiple TCR chains, we creatively found that one of TCR β (or TCR α) should originate from the transcription of V(D)J combination in T-cell receptor excision circle (TREC) formed after the twice successful rearrangement in the same chromosome. Moreover, human V30 (or mouse V31) gene may participate in reverse recombination and transcription to prevent allelic exclusion. In general, high proportion of T cells with multiple TCR at the transcriptome level was first made public, and we proposed a novel mechanism of secondary (or more) TCR rearrangement on a single chromosome. Our findings also indicated that the single-cell sequencing data should be classified according to the single, multiple, and abnormal TCR when analyzing the T-cell repertoire.

Serological and Molecular Characterization of Hepatitis C Virus-Related Cryoglobulinemic Vasculitis in Patients without Cryoprecipitate.

Prolonged B cells stimulation due to the Hepatitis C virus (HCV) can result in autoimmunity, stigmatized by rising levels of cryoglobulins (CGs), the rheumatoid factor (RF), and free light chains (FLC) of immunoglobulins (Ig) associated with a range of symptoms, from their absence to severe cryoglobulinemic vasculitis and lymphoma. Here, we aimed to identify an immunological signature for the earliest stages of vasculitis when cryoprecipitate is still not detectable. We firstly analyzed the IgG subclasses, FLC, and RF in 120 HCV-RNA-positive patients divided into four groups according to the type of cryoprecipitate and symptoms: 30 asymptomatic without cryoprecipitate (No Cryo), 30 with vasculitis symptoms but without CGs that we supposed were circulating but still not detectable (Circulating), 30 type II and 30 type III mixed cryoglobulinemia (Cryo II and Cryo III, respectively). Our results revealed that patients with supposed circulating CGs displayed a pattern of serological parameters that closely resembled Cryo II and Cryo III, with a stronger similarity to Cryo II. Accordingly, we analyzed the groups of Circulating and Cryo II for their immunoglobulin heavy chain (IgH) and T-cell receptor (TCR) gene rearrangements, finding a similar mixed distribution of monoclonal, oligoclonal, and polyclonal responses compared to a control group of ten HCV-RNA-negative patients recovered from infection, who displayed a 100% polyclonal response. Our results strengthened the hypothesis that circulating CGs are the origin of symptoms in HCV-RNA-positive patients without cryoprecipitate and demonstrated that an analysis of clonal IGH and TCR rearrangements is the best option for the early diagnosis of extrahepatic complications.

CELL‐FREE DNA KINETICS DECIPHER POTENTIAL MECHANISMS OF ACTION OF IBRUTINIB COMBINATION THERAPY IN MANTLE CELL LYMPHOMA (MCL)

Introduction: The European MCL Network trial TRIANGLE (NCT02858258) evaluated the addition of ibrutinib to standard treatment with autologous stem cell transplantation (ASCT) (arm A+I) in comparison to ASCT alone (arm A) and ibrutinib plus chemoimmunotherapy without ASCT (arm I) demonstrating significant and clinically relevant superiority of additional ibrutinib on outcome. Cell-free (cf)DNA captures tumor genetics and can be used to assess disease kinetics and minimal residual disease (MRD). We used capture based targeted sequencing for genotyping and MRD monitoring in cfDNA in the TRIANGLE trial to gain insight into the mechanisms of action of Ibrutinib and to identify patients (pts) with high risk of relapse. Methods: Peripheral blood (PB) and plasma samples from 57 pts with a PB infiltration of ≥10% at baseline (BL) and samples at mid induction (MI, n = 57) and end of induction (EoI, n = 53) were sequenced using the EuroClonality (EC)-NDC assay (Univ8® Genomics UK) to detect immunoglobulin and T-cell receptor (IG/TR) rearrangements, structural- (SV) and single nucleotide variants (SNVs) in 72 genes. Bioinformatics by ARResT/Interrogate with adaptations for cfDNA. Pts were considered MRD+ by detecting ≥1 read of a lymphoma-specific IG, SV or SNV. MRD in PB was analyzed by ASO-qPCR. Results: cfDNA levels were high at BL (mean 93 ng/mL) and MI (124 mg/mL) and decreased at EoI (12 ng/mL). BL cfDNA levels correlated with MIPI scores and identified pts with poor outcome. Genotyping by EC-NDC showed fully concordant IG clonotypes and SVs among 57 paired PB gDNA and cfDNA samples. 126 SNVs were identified (VAF 2.7%–75%, median 30%) in genes described as drivers in MCL, ATM (44%), TP53 (19%), KMT2D (16%), SAMHD1 (8%), CCND1 (8%) and 18 others. On average, 6 MRD markers were identified per patient (range 3-10). Copy number variation analysis revealed deletions in ATM (10%), CDKN2A (16%) and TP53 (5%) pts. TP53 mutations/deletions are a poor prognostic indicator in MCL, but therapy in arms A+I/I (n = 6) overcomes this poor outcome in comparison to arm A (n = 5). At MI, total cfDNA and ctDNA levels were significantly increased in arms A+I/I as compared to arm A (p = 0.049). 20/57 (35%) pts were MRD+ in PB and 35/55 (64%) in cfDNA. ctDNA was detected in 17/21 pts (81%) in Arm A and 18/34 pts (53%) in Arms A+I/I, suggesting effective disease clearance in the lymph nodes by ibrutinib. ctDNA detection at MI predicted outcome only in arm A. At EoI 8/53 (15%) pts were MRD+ in PB and 20/40 (50%) pts were MRD+ in cfDNA. ctDNA was detected in 12/18 pts (66%) in Arm A and 8/22 pts (36%) in Arms A+I/I. Similar to MI, ctDNA at EoI predicted outcome only in arm A. Keywords: combination therapies, liquid biopsy, minimal residual disease Conflicts of interests pertinent to the abstract S. Ferrero Consultant or advisory role: EUSA Pharma, Jannsen Honoraria: Servier Research funding: Gilead, Morphosys, Jannsen V. H. van der Velden Other remuneration: EuroFlow: Patents and Royalties R. García Sanz Honoraria: Janssen, BeiGene, Gilead, Astellas, Amgen, Takeda Research funding: Janssen, Gilead, Astellas, Takeda Educational grants: Janssen M. Dreyling Consultant or advisory role: Novartis, Lilly/Loxo, AstraZeneca, Roche, Janssen, Gilead/Kite, BMS/Celgene, Beigene Honoraria: Novartis, Lilly/Loxo, Amgen, AstraZeneca, Roche, Janssen, Gilead/Kite Research funding: Roche, Janssen, Bayer, AbbVie A. W. Langerak Research funding: Genentech, Roche Other remuneration: Spearkers Bureau: Janssen, Gilead D. Gonzalez de Castro Employment or leadership position: Founder and director of Univ8 Genomics Ltd.

Minimal residual disease detection by mutation-specific droplet digital PCR for leukemia/lymphoma

Minimal residual disease (MRD) is usually defined as the small number of cancer cells that remain in the body after treatment. The clinical significance of MRD kinetics is well recognized in treatment of hematologic malignancies, particularly acute lymphoblastic leukemia (ALL). Real time quantitative PCR targeting immunoglobulin (Ig) or T-cell receptor (TCR) rearrangement (PCR-MRD), as well as multiparametric flow cytometric analysis targeting antigen expression, are widely used in MRD detection. In this study, we devised an alternative method to detect MRD using droplet digital PCR (ddPCR), targeting somatic single nucleotide variants (SNVs). This ddPCR-based method (ddPCR-MRD) had sensitivity up to 1E-4. We assessed ddPCR-MRD at 26 time points from eight T-ALL patients, and compared it to the results of PCR-MRD. Almost all results were concordant between the two methods, but ddPCR-MRD detected micro-residual disease that was missed by PCR-MRD in one patient. We also measured MRD in stored ovarian tissue of four pediatric cancer patients, and detected 1E-2 of submicroscopic infiltration. Considering the universality of ddPCR-MRD, the methods can be used as a complement for not only ALL, but also other malignant diseases regardless of tumor-specific Ig/TCR or surface antigen patterns.

Read the clonotype: Next-generation sequencing-based lymphocyte clonality analysis and perspectives for application in pathology.

Clonality assessment using the unique rearrangements of immunoglobulin (IG) and T-cell receptor (TR) genes in lymphocytes is a widely applied supplementary test for the diagnosis of B-cell and T-cell lymphoma. To enable a more sensitive detection and a more precise comparison of clones compared with conventional clonality analysis based on fragment analysis, the EuroClonality NGS Working Group developed and validated a next-generation sequencing (NGS)-based clonality assay for detection of the IG heavy and kappa light chain and TR gene rearrangements for formalin-fixed and paraffin-embedded tissues. We outline the features and advantages of NGS-based clonality detection and discuss potential applications for NGS-based clonality testing in pathology, including site specific lymphoproliferations, immunodeficiency and autoimmune disease and primary and relapsed lymphomas. Also, we briefly discuss the role of T-cell repertoire of reactive lymphocytic infiltrations in solid tumors and B-lymphoma.

Prevalence of STAT3 mutations in patients with rheumatoid arthritis-associated T-cell large granular lymphocytic leukaemia and Felty syndrome.

Neutropenia is a key presentation of Felty syndrome (FS) and rheumatoid arthritis (RA)-associated T-cell large granular lymphocytic (T-LGL) leukaemia. Clonal rearrangement of T-cell receptor (TCR) gene supports the diagnosis of T-LGL leukaemia but not FS. Mutations in the signal transducer and activator of transcription 3 (STAT3) gene are highly specific for T-LGL leukaemia, but their prevalence in FS remains poorly clarified. The study included 100 patients with RA and unexplained neutropenia. TCR rearrangements were examined in blood (100 cases), bone marrow (47 cases), and spleen (12 cases) using the BIOMED-2 protocol. Patients were stratified into RA-associated T-LGL leukaemia cohort if a clonal TCR rearrangement was identified in any of the tested patient samples, and into FS cohort in other cases. Mutations in the STAT3 were examined using next-generation sequencing (NGS) technology in blood (100 cases), bone marrow (37 cases), and spleen (7 cases). STAT3 mutations were identified in 71% (49/69) patients with RA-associated T-LGL leukaemia and in 10% (3/31) patients with FS (p=4.7×10-8). Three samples from the RA-associated T-LGL leukaemia cohort and 5 samples from the FS cohort had STAT3 mutations in the absence of clonal TCR rearrangement. The results suggest that STAT3 mutations are significantly less common in FS than in RA-associated T-LGL leukaemia. Moreover, NGS can detect clones undetectable by fragment analysis. We speculate that in patients with RA and neutropenia, the detection of STAT3 mutations can point to T-LGL leukaemia even in the absence of clonal TCR rearrangement.

Antigen-specific TCR-T cells from Rag2 gene-deleted pluripotent stem cells impede solid tumour growth in a mouse model.

The technology of adoptive transfer of T-cell receptor (TCR) engineered T cells is wildly investigated as it has the potential to treat solid cancers. However, the therapeutic application of TCR-T cells is hampered by the poor quality derived mainly from patients' peripheral blood, as well as heterogeneous TCRs caused by the mismatch between transgenic and endogenous TCRs. To improve the homogeneity, antigen-specificity and reduce possible autoreactivity, here we developed a technique to generate antigen-specific T cells from Rag2 gene-deleted pluripotent stem cells (PSCs) and further measured their anti-tumour efficacy. PSCs were first targeted with OT1 TCR into the Rag2 locus to prevent TCR rearrangement during T-cell development. The engineered PSCs were then differentiated through a two-step strategy, in vitro generation of haematopoietic progenitor cells, and in vivo development and maturation of TCR-T cells. Finally, the response to tumour cells was assessed in vitro and in vivo. The regenerated OT1-iT displayed monoclonal antigen-specific TCR expression, and phonotypic normalities in the spleen and lymph node tissues. Importantly, the OT1-iT cells eliminated tumour cells while releasing specific cytokines in vitro. Furthermore, adoptive transfer of OT1-iT cells suppresses solid tumour growth in tumour-bearing animals. Our study presents a novel and straightforward strategy for producing antigen-specific TCR-T cells in vivo from PSCs, allowing for allogeneic transplantation and therapy of solid tumours.

Determinants of resistance to engineered T cell therapies targeting CD19 in large B cell lymphomas.

Most relapsed/refractory large B cell lymphoma (r/rLBCL) patients receiving anti-CD19 chimeric antigen receptor (CAR19) Tcells relapse. To characterize determinants of resistance, we profiled over 700 longitudinal specimens from two independent cohorts (n= 65 and n= 73) of r/rLBCL patients treated with axicabtagene ciloleucel. A method for simultaneous profiling of circulating tumor DNA (ctDNA), cell-free CAR19 (cfCAR19) retroviral fragments, and cell-free Tcell receptor rearrangements (cfTCR) enabled integration of tumor and both engineered and non-engineered Tcell effector-mediated factors for assessing treatment failure and predicting outcomes. Alterations in multiple classes of genes are associated with resistance, including B cell identity (PAX5 and IRF8), immune checkpoints (CD274), and those affecting the microenvironment (TMEM30A). Somatic tumor alterations affect CAR19 therapy at multiple levels, including CAR19 Tcell expansion, persistence, and tumor microenvironment. Further, CAR19 Tcells play a reciprocal role in shaping tumor genotype and phenotype. We envision these findings will facilitate improved chimeric antigen receptor (CAR) Tcells and personalized therapeutic approaches.

A Blood-Based Molecular Clock for Biological Age Estimation.

In the last decade, extensive efforts have been made to identify biomarkers of biological age. DNA methylation levels of ELOVL fatty acid elongase 2 (ELOVL2) and the signal joint T-cell receptor rearrangement excision circles (sjTRECs) represent the most promising candidates. Although these two non-redundant biomarkers echo important biological aspects of the ageing process in humans, a well-validated molecular clock exploiting these powerful candidates has not yet been formulated. The present study aimed to develop a more accurate molecular clock in a sample of 194 Italian individuals by re-analyzing the previously obtained EVOLV2 methylation data together with the amount of sjTRECs in the same blood samples. The proposed model showed a high prediction accuracy both in younger individuals with an error of about 2.5 years and in older subjects where a relatively low error was observed if compared with those reported in previously published studies. In conclusion, an easy, cost-effective and reliable model to measure the individual rate and the quality of aging in human population has been proposed. Further studies are required to validate the model and to extend its use in an applicative context.