Immunoglobulin Kappa Locus Research Articles

Resolving haplotype variation and complex genetic architecture in the human immunoglobulin kappa and lambda chain loci in individuals of diverse ancestry

Abstract Immunoglobulins (IGs), critical components of the human immune system, are composed of heavy and light protein chains encoded at three genomic loci. The IG Kappa (IGK) chain locus consists of two large, inverted segmental duplications. The complexity of IG loci has hindered effective use of standard high-throughput methods for characterizing genetic variation within these regions. To overcome these limitations, we leverage long-read sequencing to create haplotype-resolved IGK assemblies in an ancestrally diverse cohort (n=36), representing the first comprehensive description of IGK haplotype variation. We identify extensive locus polymorphism, including novel single nucleotide variants (SNVs) and a common novel ∼24.7 Kbp structural variant harboring a functional IGKV gene. Among 47 functional IGKV genes, we identify 141 alleles, 64 (45.4%) of which were not previously curated. We report inter-population differences in allele frequencies for 14 IGKV genes, including alleles unique to specific populations within this dataset. In addition, we identify haplotypes carrying signatures of gene conversion that associate with enrichment of SNVs in the IGK distal region. Finally, we identify extensive polymorphism in the IG Lambda (IGL) locus, including copy number variation for genes encoding IGLC and IGLJ genes. These data lay a foundation for advancing our understanding of how genetic variation in IG loci impacts expressed antibody repertoires in human populations.

Abstract 339: Universal synthetic TCR/BCR spike-in controls to evaluate immune receptor profiling assay and next-generation sequencing performance

Abstract Adaptive immune receptor (AIR) repertoire diversity assays are susceptible to biases arising from variations in conditions in the RT-PCR and next-generation sequencing (NGS) steps. We designed synthetic TCR and BCR spike-in controls to mitigate these biases and to serve as universal standards for any PCR-based immune receptor profiling assay. We synthesized 48 BCR constructs representing different IGH, IGK, and IGL genes and 39 TCR constructs for TRB, TRA, TRG, and TRD genes. The spike-in controls were tested as (16 × 3) BCR constructs and (13 × 3) TCR Triplex isoform pools added to multiple samples in the same batch to detect cross-contamination across samples. We successfully discriminated between controls and background sequences by combining a unique molecular identifier (UMI)-based correction strategy with spike-in controls at the data analysis step. We also tested 48 BCR and 39 TCR Premixed Controls by spiking into peripheral blood mononuclear cells (PBMC) RNA samples before reverse transcription using Cellecta’s DriverMap™ Adaptive Immune Receptor Profiling Assay that uses a multiplex RT-PCR approach with gene-specific primers and UMIs. We successfully used it to evaluate assay performance by adding premixed controls at different concentrations. Results showed a linear trend as the number of spike-in molecules increased. Our analysis revealed an average sequencing error rate of 0.4%-0.8% per base, aligning with the reported error rate range of Illumina sequencing. This suggests the reliability of our spike-in controls, which can be used to rectify biases in the AIR protocol and accurately estimate error and mutation rates for the DriverMap AIR assay or any other sequencing-based immune receptor profiling assay. This innovative approach enhances the robustness of immune receptor profiling technology, facilitating more accurate assessments of repertoire diversity. Citation Format: Alex Chenchik, Tianbing Liu, Mikhail Makhanov, Dongfang Hu, Khadija Ghias, Paul Diehl. Universal synthetic TCR/BCR spike-in controls to evaluate immune receptor profiling assay and next-generation sequencing performance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 339.

Assessment of Bone Marrow Involvement in B-Cell non-Hodgkin Lymphoma Using Immunoglobulin Gene Rearrangement Analysis with Next-Generation Sequencing.

Assessment of bone marrow involvement (BMI) in non-Hodgkin lymphoma (NHL) is crucial for determining patient prognosis and treatment strategy. We assessed the prognostic value of next-generation sequencing (NGS)-based immunoglobulin (Ig) gene clonality analysis as an ancillary test for BMI evaluation in NHL. A retrospective cohort of 124 patients newly diagnosed with B-cell NHL between 2019 and 2022 was included. NGS-based Ig clonality analysis was conducted using LymphoTrak IGH FR1 Assay and IGK Assay (Invivoscribe Technologies, San Diego, CA, USA) on BM aspirate samples, and the results were compared with those of histopathological BMI (hBMI). Among the 124 patients, hBMI was detected in 16.9% (n = 21). The overall agreement of BMI between Ig clonality analyses and histopathological analysis for IGH, IGK, and either IGH or IGK was 86.3%, 92.7%, and 90.3%. The highest positive percent agreement was observed with clonal rearrangements of either IGH or IGK gene (90.5%), while the highest negative percent agreement was observed with clonal rearrangement of IGK gene (96.1%). For the prediction of hBMI, positive prediction value ranged between 59.1% and 80.0% and the negative prediction value ranged between 91.3% and 97.9%. NGS-based clonality analysis is an analytic platform with a substantial overall agreement with histopathological analysis. Assessment of both IGH and IGK genes for the clonal rearrangement analysis could be considered for the optimal diagnostic performance of BMI detection in B-cell NHL.

Kidins220 regulates the development of B cells bearing the λ light chain.

The ratio between κ and λ light chain (LC)-expressing B cells varies considerably between species. We recently identified Kinase D-interacting substrate of 220 kDa (Kidins220) as an interaction partner of the BCR. In vivo ablation of Kidins220 in B cells resulted in a marked reduction of λLC-expressing B cells. Kidins220 knockout B cells fail to open and recombine the genes of the Igl locus, even in genetic scenarios where the Igk genes cannot be rearranged or where the κLC confers autoreactivity. Igk gene recombination and expression in Kidins220-deficient B cells is normal. Kidins220 regulates the development of λLC B cells by enhancing the survival of developing B cells and thereby extending the time-window in which the Igl locus opens and the genes are rearranged and transcribed. Further, our data suggest that Kidins220 guarantees optimal pre-BCR and BCR signaling to induce Igl locus opening and gene recombination during B cell development and receptor editing.

Effects of early treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) on the bronchoalveolar lavage proteome and oxylipids during bovine respiratory syncytial virus (BRSV) infection.

Non-steroidal anti-inflammatory drugs (NSAID) are not recommended for use against pneumonia in humans, but are commonly utilised against bovine respiratory disease. This study aimed to determine if the use of NSAIDs in the early phase of bovine respiratory syncytial virus (BRSV)-infection limits pulmonary inflammation. Four to nine-week old calves were infected with BRSV by aerosol and were treated with either meloxicam intravenously on day (D)4 (n = 5, MEL), acetylsalicylat-DL-lysin intravenously on D4 and D5 (n = 5, ASA), or were left untreated as controls (n = 5, CTR). Clinical signs were monitored daily until necropsy on D7, BRSV-RNA was detected in nasal swabs and bronchoalveolar lavage (BAL) by RT-qPCR, inflammatory cells and proteins were identified in BAL by cytology and label-free quantitative mass spectrometry-based proteomics, respectively, and oxylipids were quantified in BAL and plasma by liquid chromatography tandem mass spectrometry with triple quadrupole mass detectors. The calves developed mild to moderate signs of respiratory disease and, with the exception of one MEL-treated and one ASA-treated calf, limited lung lesions. None of the treatments had a significant effect on virus replication, clinical signs or lung lesion extent. Relative to controls, both treatments initially induced a downregulation of proteins in BAL. Immunoglobulin (Ig)-related proteins, such as the Ig kappa and lambda locus and the joining chain of IgA and IgM, were downregulated in MEL-treated calves compared to controls. In addition, meloxicam induced an increased neutrophil influx in BAL in response to BRSV, possibly related to a reduction in plasma prostaglandin, and to a downregulation of The Liver X Receptor/ Retinoid X Receptor (LXR/RXR), the Farnesoid X Receptor (FXR)/RXR and the 24-Dehydrocholesterol Reductase (DHC24) signalling pathways in the lung. The risk of NSAIDs to increase neutrophil activity during stimulation with BRSV or other toll-like receptor 4 agonists needs to be investigated further. Since augmented neutrophil responses can be detrimental, the results of the present study do not support the use of NSAIDs to prevent the clinical expression of BRSV-infection.

Molecular pathology assists the diagnosis of lymphoepithelial sialadenitis, Sjögren's syndrome and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue

Background/purposeLymphoepithelial sialadenitis (LESA), Sjögren's syndrome (SS), and salivary MALT lymphoma are diseases characterized by lymphoepithelial lesions, and the differential diagnosis between them in the salivary glands is challenging. This study aimed to explore clinicopathological and genetic characteristics of the three diseases. Materials and methodsWe retrospectively analyzed the clinical features, the histomorphology, immunohistochemistry, and genetic profiling by polymerase chain reaction (PCR) and next-generation sequencing (NGS). ResultsThere included 68 LESAs, 25 SSs, and 62 MALT lymphomas. Ten cases relapsed in total, and 3 of MALT lymphomas died due to high-level transformation. Immunohistochemical double staining showed FCRL4 cells co-expressed Pax-5 and Ki-67, suggesting FCRL4 cells were proliferative B-cells. The expression level of the FCRL4 was significantly higher in MALT lymphoma than LESA and SS. The detection rates of clonal IGH, IGK, and IGL gene rearrangements in MALT lymphoma with a sensitivity of 83.33%. Monoclonal immunoglobulin gene rearrangements were confirmed in five suspected patients by NGS (100%). ConclusionFCRL4 B cells might play an important role in the formation of lymphoepithelial lesions and might be as a diagnostic positive marker of salivary MALT lymphoma. The application of multiple detection methods could significantly improve the diagnostic accuracy for MALT lymphomas from LESA and SS.

Enhancer-instructed epigenetic landscape and chromatin compartmentalization dictate a primary antibody repertoire protective against specific bacterial pathogens.

Antigen receptor loci are organized into variable (V), diversity (D) and joining (J) gene segments that rearrange to generate antigen receptor repertoires. Here, we identified an enhancer (E34) in the murine immunoglobulin kappa (Igk) locus that instructed rearrangement of Vκ genes located in a sub-topologically associating domain, including a Vκ gene encoding for antibodies targeting bacterial phosphorylcholine. We show that E34 instructs the nuclear repositioning of the E34 sub-topologically associating domain from a recombination-repressive compartment to a recombination-permissive compartment that is marked by equivalent activating histone modifications. Finally, we found that E34-instructed Vκ-Jκ rearrangement was essential to combat Streptococcus pneumoniae but not methicillin-resistant Staphylococcus aureus or influenza infections. We propose that the merging of Vκ genes with Jκ elements is instructed by one-dimensional epigenetic information imposed by enhancers across Vκ and Jκ genomic regions. The data also reveal how enhancers generate distinct antibody repertoires that provide protection against lethal bacterial infection.

Role of immunoglobulin heavy and light chain gene rearrangement analysis in differentiating between benign and malignant bone marrow B-cell lymphoid aggregates

Lymphoid aggregates are found in a minority of bone marrow biopsy and aspirate specimens, and when present, the distinction between benign and malignant aggregates can represent a diagnostic challenge. Morphologic and immunophenotypic evaluation of the aggregates can aid in that distinction but in a few cases, detection of immunoglobulin heavy chain (IGH) and kappa light chain (IGK) gene rearrangements may be needed to rule in or out a malignant disease process. We studied the role of testing for IGH/IGK rearrangements in the distinction between benign and malignant B cell-predominant lymphoid aggregates. Only a few studies have addressed this issue and most lacked an adequate number of cases for establishing statistical significance. Our study retrospectively evaluated 120 bone marrow aspirate and biopsy specimens, 79 cases originally diagnosed with benign lymphoid aggregates [4,5], and 41 demonstrating a B-cell lymphoma with malignant aggregates. Immunohistochemical stains were performed on all cases in our study and flow cytometry results were available in the vast majority of cases (98%). All patients included in our study but 9 had at least 2 years of clinical follow-up information. Of the malignant lymphoma cases, IGH/IGK rearrangements were demonstrated by polymerase chain reactionin 60% of the cases. Moreover, clonal rearrangements were identified in 15% of the cases with benign aggregates. After at least 2 years of follow-up, only one case with a positive clonality study occurring in the setting of morphologically benign-appearing bone marrow lymphoid aggregates experienced a relapse of non-Hodgkin lymphoma. Molecular analysis of the IGH and IGK genes may have utility in confirming the presence of malignancy in bone marrow aspirates and biopsy specimens. False-negative results, however, are possible due to testing limitations and sampling issues. Moreover, patients with conditions such as autoimmune disorders or infectious diseases are shown to also develop clonal B-cell lymphoid aggregates. As a result, we recommend a thorough morphological examination, informative immunohistochemical staining, accurate flow cytometric analysis, and current IGH/IGK rearrangement testing when evaluating bone marrow specimens containing B cell-predominant lymphoid aggregates, with the knowledge that molecular clonality results should be carefully interpreted in the context of morphological and immunophenotypic findings to prevent misdiagnosis.

Abstract 2778: Validation of a next generation sequencing clinical assay for detection of immunoglobulin heavy chain clonality and somatic hypermutation in chronic lymphocytic leukemia

Abstract Next-generation sequencing (NGS) provides a powerful high-throughput approach to identify and track B-cell immunoglobulin (IG) heavy chain clonality and to assess somatic hypermutation status in a massively parallel manner. The NGS-based clonality/SHM testing demonstrated superior performance over the conventional capillary electrophoresis (CE) methods in characterization of B-cell neoplasms. However, its broad utilization in clinical diagnostics requires extensive validation of assays as well as standardization of data interpretation. We present here an NGS assay designed and validated specifically for IG clonality/SHM characterization of B-cell malignancies. The assay was designed to simultaneously target the Leader, FR1, FR2, and FR3 regions of the IGH gene to identify clonal IGH VH-JH rearrangement as well as the IGK gene to identify clonal IGK VK-JK, VK-Kde, and INTR-Kde rearrangement. The validation was performed to assess assay accuracy, specificity, sensitivity, repeatability, and reproducibility, with both pre-characterized reference controls and prospectively collected clinic peripheral blood and bone marrow aspirate specimen included. Triplicates were included and testing was performed at different times and by different operators to assess the assay precision. Over 60 clinic peripheral blood and bone marrow aspirate specimens were collected, including patients with B-cell malignancies such as CLL, B-ALL, and DLBCL as well as heathy donors, processed within 7 days for DNA extraction, and assessed by the NGS assay for IGH clonality and SHM assessment. Assay sensitivity as low as 2.5% for baseline clonality and as low as 0.001% for tracking MRD were observed. Near-perfect assay specificity and precision were observed at these sensitivity levels. The validated NGS assay was further qualified by ERIC (the European Research Initiative on CLL) with a certificate granted to standardize the data interpretation of this assay for testing in chronic lymphocytic leukemia. In conclusion, a NGS IG clonality/SHM assay was analytically and clinically validated under medical oversight, with a demonstrated rigor of the test by its high sensitivity/specificity and robust reproducibility. The clinical diagnostic testing results with this assay is interpreted in accordance with ERIC standards for reliable clinical reporting. Citation Format: Xin-Xing Tan, Tricia Peters, Meredith Berry, Kristyn Jeter, Brigitte Lovell, Victor Venegas, Yanglong Mou, Brad Thomas, Vincent Funari, Josette William. Validation of a next generation sequencing clinical assay for detection of immunoglobulin heavy chain clonality and somatic hypermutation in chronic lymphocytic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2778.

The order of immunoglobulin light chain κ and λ usage in primary and secondary lymphoid tissues of germ-free and conventional piglets

In pigs (Sus scrofa), the initial immunoglobulin rearrangement of the κ light chain is replaced by λ before the heavy chains rearrange, and the light chains may rearrange even later. This study investigates whether these developmental differences are reflected in the usage of IGK and IGL genes. We found large differences between peripheral B cells and those developing in the bone marrow, and between B cells in germ-free piglets and conventional pigs. During early B cell development in the bone marrow, more 3′ V and 5′ J gene segments for both light chains are used. However, in the peripheral naive repertoire, more 5′ IGLV and 3′ IGLJ genes are used. A similar shift toward the use of more 5′ IGKV and 3′ IGKJ genes is observed later after antigen exposure in conventional pigs. The expression profile showed that most λ+ B cells are generated earlier, while κ+ B cells develop from late precursors that already contain the λ rearrangement. The initial λ rearrangement is retained in both λ+ and κ+ B lymphocytes, and multiple λ transcripts can be found in individual cells. The overall pool of the IGLV repertoire is therefore much larger and more diversified than for IGKV. The κ repertoire is further restricted to the preferential use of only two major IGKV genes, reflecting the limitation for only two consecutive rearrangements. Tracing of silenced λ transcripts in κ+ B cells further confirmed the unconventional mechanism of differential rearrangements in pigs. Our results underline the diversity of the immune system among mammals.

Nemo-Dependent, ATM-Mediated Signals from RAG DNA Breaks at Igk Feedback Inhibit V κ Recombination to Enforce Igκ Allelic Exclusion.

Monoallelic AgR gene expression underlies specific adaptive immune responses. AgR allelic exclusion is achieved by sequential initiation of V(D)J recombination between alleles and resultant protein from one allele signaling to prevent recombination of the other. The ATM kinase, a regulator of the DNA double-strand break (DSB) response, helps enforce allelic exclusion through undetermined mechanisms. ATM promotes repair of RAG1/RAG2 (RAG) endonuclease-induced DSBs and transduces signals from RAG DSBs during Igk gene rearrangement on one allele to transiently inhibit RAG1 protein expression, Igk accessibility, and RAG cleavage of the other allele. Yet, the relative contributions of ATM functions in DSB repair versus signaling to enforce AgR allelic exclusion remain undetermined. In this study, we demonstrate that inactivation in mouse pre-B cells of the NF-κB essential modulator (Nemo) protein, an effector of ATM signaling, diminishes RAG DSB-triggered repression of Rag1/Rag2 transcription and Igk accessibility but does not result in aberrant repair of RAG DSBs like ATM inactivation. We show that Nemo deficiency increases simultaneous biallelic Igk cleavage in pre-B cells and raises the frequency of B cells expressing Igκ proteins from both alleles. In contrast, the incidence of biallelic Igκ expression is not elevated by inactivation of the SpiC transcriptional repressor, which is induced by RAG DSBs in an ATM-dependent manner and suppresses Igk accessibility. Thus, we conclude that Nemo-dependent, ATM-mediated DNA damage signals enforce Igκ allelic exclusion by orchestrating transient repression of RAG expression and feedback inhibition of additional Igk rearrangements in response to RAG cleavage on one Igk allele.

Current Knowledge in Genetics, Molecular Diagnostic Tools, and Treatments for Mantle Cell Lymphomas.

Mantle Cell lymphoma (MCL) is a mature B-cell lymphoma with a well-known hallmark genetic alteration in most cases, t (11,14)(q13q32)/CCND1-IGH. However, our understanding of the genetic and epigenetic alterations in MCL has evolved over the years, and it is now known that translocations involving CCND2, or cryptic insertion of enhancer elements of IGK or IGL gene, can also lead to MCL. On a molecular level, MCL can be broadly classified into two subtypes, conventional MCL (cMCL) and non-nodal MCL (nnMCL), each with different postulated tumor cell origin, clinical presentation and behavior, mutational pattern as well as genomic complexity. This article reviews both the common and rare alterations in MCL on a gene mutational, chromosomal arm, and epigenetic level, in the context of their contribution to the lymphomagenesis and disease evolution in MCL. This article also summarizes the important prognostic factors, molecular diagnostic tools, and treatment options based on the most recent MCL literature.

Retrospective Analysis of Minimal Residual Disease Testing By High Throughput Immunosequencing Versus High Sensitivity Flow Cytometry in Multiple Myeloma

Introduction:Detection of minimal residual disease (MRD) is one of the strongest predictors of outcome in multiple myeloma (MM). Until recently, the most commonly available method to detect MRD in clinical practice has been high sensitivity flow cytometry (FC) which can detect MRD with at 10 -5 sensitivity. In recent years, next-generation sequencing (NGS) has become a viable method to assess the MRD in MM patients with a 10 -6 sensitivity. NGS appears to have some advantages over HC-FC by circumventing subjectivity of analysis. However, real-world comparison between these two methodologies in the literature is limited and is important to inform daily hematopathology and oncology ordering practices.Methods:We retrospectively identified all cases of MM with NGS MRD data from bone marrow specimens at the Moffitt Cancer Center and collated corresponding flow MRD data and clinical data (OS, patient demographics) electronically and via chart review.10-color flow cytometry was performed on a Gallios System and analyzed on Kaluza (Beckman Coulter, IN). Two million events were collected on all cells. Validated lower limit of detection was at least 0.01%. Antibodies included CD28, CD81, CD56, CD138, CD319, CD20, CD19, CD117, CD38, CD45, CD27, CD200 (BD, Biolegend, Beckman Coulter).clonoSEQ ® (Adaptive Biotechnologies, Seattle, WA) testing was performed which uses multiplex polymerase chain reaction (PCR) and NGS to identify, characterize, and monitor clonotypes of immunoglobulin (Ig) IgH (V-J), IgH (D-J), IgK, and IgL receptor gene sequences, and translocated BCL1/IgH (J) and BCL2/IgH (J) sequencesStatistical analysis was performed by Spearman correlation coefficient and Kaplan-Meier analysis.Results:192 samples from 122 unique patients were identified that had both NGS and FC data performed on the same sample. FC+ values ranged from 1x10 -7 to 0.39. NGS+ values ranged from 2.3 x 10 -7 to 0.15. Spearman correlation coefficient showed moderate concordance between NGS and FC at r=0.67 (p<0.001). Six samples were positive by FC (mean tumor burden (MTB)= 0.0007) but missed by NGS; whereas 59 samples were positive by NGS (MTB= 0.002) but missed by flow cytometry. Two cases by FC were equivocal and these were both definitively designated as MRD+ by NGS. Overall survival was worse for MRD+ (by NGS or FC) vs MRD(-) (Figure 1).Conclusion:Our study confirms the importance of MRD detection in MM and shows the robust utility of NGS for MRD detection in routine hematopathology practice. While both FC and NGS are complementary given that each can potentially detect MRD missed by another method, the data supports the increased sensitivity of NGS over FC. [Display omitted] DisclosuresNishihori: Novartis: Research Funding; Karyopharm: Research Funding. Hussaini: Stemeline Therapeutics: Honoraria.

Concurrent Monitoring of Peripheral Blood Circulating Tumor DNA and Circulating Tumor Cells in Relapsed/Refractory Follicular Lymphoma Patients Post Axicabtagene Ciloleucel, a Single Center Experience

Concurrent Monitoring of Peripheral Blood Circulating Tumor DNA and Circulating Tumor Cells in Relapsed/Refractory Follicular Lymphoma Patients Post Axicabtagene Ciloleucel, a Single Center Experience

Retrospective Analysis of Minimal Residual Disease Testing By High Throughput Immunosequencing Versus High Sensitivity Flow Cytometry and qPCR in B-Lymphoblastic Leukemia

Introduction: Detection of minimal residual disease (MRD) is one of the most powerful predictors of prognosis in patients with B-Lymphoblastic Leukemia (ALL). Standard methods to detect MRD in ALL include high-resolution flow cytometry (FC) (sensitivity 10 -4 to 10 -5) and qPCR for Ph+ ALL (sensitivity 10 -5 to -6). More recently, high-throughput sequencing (NGS) has been leveraged to detect MRD (sensitivity 10 -6). Retrospective, non-clinical trial based real-world data comparing between these methodologies in the literature is limited to absent. We report our experience at a high-volume cancer center comparing NGS, qPCR, and FC.Methods: All cases of ALL with NGS MRD data at the Moffitt Cancer Center were identified. Corresponding FC, qPCR (p190 and p210) and clinical data were collected electronically and via chart review.10-color flow cytometry was performed on a Gallios System and analyzed on Kaluza (Beckman Coulter, IN). 750,000 events were collected on all cells. Validated lower limit of detection was at least 0.01%. Antibodies included CD15, CD130, CD10, CD58, CD22, CD33, CD13, CD123, CD19, CD20, CD45, CD38, CD34, CD81, CD200 (BD, Biolegend, Beckman Coulter).Quantidex™ BCR-ABL IS Kit (RT qPCR) was used to quantify BCR-ABL (p190 and p210) and ABL transcripts in total RNA in patients with ALL on Applied Biosystems 7500 Fast Dx Real-Time PCR instrument. The results were expressed by normalized BCR-ABL to ABL (control) ratio.clonoSEQ ® (Adaptive Biotechnologies, Seattle, WA) testing was performed which uses multiplex polymerase chain reaction (PCR) and NGS to identify, characterize, and monitor clonotypes of immunoglobulin (Ig) IgH (V-J), IgH (D-J), IgK, and IgL receptor gene sequences, and translocated BCL1/IgH (J) and BCL2/IgH (J) sequences.Statistical analysis was performed by Spearman correlation coefficient and Kaplan-Meier analysis.Results: 95 samples from 54 unique patients were identified that had both NGS and FC data. A subset of patients had qPCR data (n=31 samples). FC+ values ranged from 0.00004 to 0.75. NGS+ values ranged from 8.25E-08 to 0.49. Spearman correlation coefficient showed moderate concordance between NGS and FC at r=0.62 (p<0.001). Spearman correlation coefficient for qPCR vs Flow was r= 0.08 (p=0.68). Three samples were positive by FC (mean tumor burden (MTB= 0.002) but missed by NGS; whereas 31 samples were detected by NGS (MTB= 0.0016) that were missed by flow cytometry. By FC, 9 samples were equivocal of which 7 were definitively designated as MRD+ by NGS. There were 7 qPCR+/NGS- samples (MTB= 2.5 x 10 -5) and 6 qPCR-/NGS+ cases (MTB= 0.012). Overall survival was worse for MRD+ (by NGS, qPCR, or FC) vs MRD(-) (Figure 1).Conclusion:Our study confirms the importance of MRD detection in ALL and shows the robust utility of NGS for MRD detection in routine hematopathology practice. While qPCR, FC and NGS are complementary given that each can potentially detect MRD missed by another method, the data supports the increased sensitivity of NGS over FC. [Display omitted] DisclosuresShah: Servier Genetics: Other; Jazz Pharmaceuticals: Research Funding; Incyte: Research Funding; BeiGene: Consultancy, Honoraria; Acrotech/Spectrum: Honoraria; Pharmacyclics/Janssen: Honoraria, Other: Expenses; Kite, a Gilead Company: Consultancy, Honoraria, Other: Expenses, Research Funding; Precision Biosciences: Consultancy; Amgen: Consultancy; Pfizer: Consultancy, Other: Expenses; Novartis: Consultancy, Other: Expenses; Bristol-Myers Squibb/Celgene: Consultancy, Other: Expenses; Adaptive Biotechnologies: Consultancy. Hussaini: Stemeline Therapeutics: Honoraria.

FISH-Guided Evaluation of Hyperdiploidy and Other Cytogenetic Abnormalities in Childhood Burkitt Lymphoma

Background: Burkitt lymphoma (BL) is the most common lymphoma in childhood. Apart from MYC rearrangement, considered the hallmark of the disease, BL often presents with additional chromosome aberrations, the biological and clinical significance of which is not fully understood. Materials and methods: The study included 72 children (55 boys, 17 girls), aged 2-16 years (median 9), with BL diagnosed on the basis of histopathology and a demonstrable MYC rearrangement. Touch imprints from the diagnostic biopsy samples were investigated with i-FISH for MYC, BCL2, BCL6, IGH, IGK and IGL rearrangements genes and copy number aberrations involving 1q21/1p32, 7cen/7q31, 9cen/9p21, 13q14/13q34 and 17cen/17p13. Deviations from the diploid status were further investigated for aneusomies of the carrier chromosome with the use of appropriate chromosome enumeration probes. Results: MYC gene was demonstrated in all cases with MYC/IGH fusion in 83.3% (60/72). 47 cases (65.3%) were found with least one additional aberration, most commonly with 1q gain (29.2%), 7q gain (19.4%), 13q deletion (19.4%), hemizygous 9p loss (8.3%) and hyperdiploidy (8.3%). Advanced clinical stage (IV), 7q gain (but not trisomy 7) and -9/9p- were significantly associated with shorter overall survival. There was no instance of relapse or death among the hyperdiploid cases. Conclusions: This extensive FISH investigation on imprints of affected tissue provides clinically meaningful information on the genetic profile of BL and may prove valuable in the management of patients with no karyotype available. In particular, the demonstration of hyperdiploidy through the use of chromosome enumeration probes could offer the means for the delineation of clonal evolution pathways and the recognition of a subgroup of children with excellent prognosis who could be cured with low-intensity chemotherapy regimens. DisclosuresKattamis: VIFOR: Consultancy; CRISPR/Vertex: Consultancy, Honoraria; Agios Pharmaceuticals: Consultancy; IONIS: Consultancy; BMS/Celgene: Consultancy, Honoraria, Research Funding; Chiesi: Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Consultancy.

P-036: Implementation of IgH/k Next Generation Sequencing for Multiple Myeloma Minimal Residual Disease monitoring: advantages in patients’ management during daily clinical practice.

<h3>Background</h3> The introduction of novel agents into the therapeutic algorithm of Multiple Myeloma (MM) has led to remarkable improvements in the rate of Minimal Residual Disease (MRD) negative status. Sustained MRD negativity is a robust prognosticator and a driver of treatment strategies. Therefore, it is expected that MRD molecular tracking would become critical in the management of MM, and could be included in daily clinical practice. <h3>Aim</h3> To evaluate the performances of next generation sequencing (NGS), implemented as best practice in MM MRD daily evaluation. <h3>Methods</h3> A cohort of 166 newly diagnosed transplant-eligible and -ineligible MM pts were screened to define the ID clonotypes. MRD was firstly assessed at achievement of at least a very good partial response during maintenance, and thereafter once a year. In high-risk pts, MRD was also detected between 1° and 2° autologous stem-cell transplantation (ASCT). The ID clonotypes screening has been performed by NGS, using an assay covering IgH and Igk genes (Invivoscribe®). The MRD tracking has been done both by conventional ASO-qPCR and by NGS. Data were analyzed by Lymphotrack Dx and MRD software (Invivoscribe®). <h3>Results</h3> The ID clonotypes screening was successful in 158/166 pts (95%), even though a small proportion of pts resulted polyclonal (14/158). Overall, 63, 27 and 54 pts had IgH, Igk and IgH/k ID clonotypes, respectively, mainly restricted to the VH3 (47%) family genes. MRD assessment was performed by NGS in 124/144 pts (overall, 96 MRD samples for 64 pts monitored to date), with 10-5 sensitivity in most cases (75/96). 44 pts were assessed during maintenance and 23 achieved MRD-negativity. On the contrary, 20 pts were evaluated between 1° and 2° ASCT, resulting MRD-positive in all cases. Overall, few FU samples (13/96) were reported as "positive-not-quantifiable" (PNQ), since had residual disease levels of 10-7, much lower than the internal control. In a subset of 20 pts with trackable IgH/Igk sequences, pts-specific assays were designed, according to the EuroMRD guidelines. In these pts, MRD was tested both by ASO-qPCR (including a standard curve and healthy donor cells, to define the sensitivity and the specificity, respectively) and by NGS. Overall, ASO-qPCR allowed the tracking of a single MRD clone (with up to 10-4 sensitivity) in 12/20 pts (60%), whereas NGS was feasible in all of them, confirming the ASO-qPCR results, yet with higher sensitivity and >95% confidence. Moreover, in 2 cases, NGS allowed to disclose ASO-qPCR PNQ results due to nonspecific amplification, thus unveiling MRD negativity with 10-5 sensitivity. <h3>Conclusion</h3> NGS has been successfully implemented as best practice in the management of MM pts, showing the superiority of this method over ASO-qPCR conventional approach. The ID clonotype was defined in almost all pts included in the workflow, thus allowing their MRD molecular monitoring, according to the clinical requirements. <h3>Acknowledgment</h3> AIRC IG2018-22059

Population matched (pm) germline allelic variants of immunoglobulin (IG) loci: Relevance in infectious diseases and vaccination studies in human populations

Immunoglobulin (IG) loci harbor inter-individual allelic variants in many different germline IG variable, diversity and joining genes of the IG heavy (IGH), kappa (IGK) and lambda (IGL) loci, which together form the genetic basis of the highly diverse antigen-specific B-cell receptors. These allelic variants can be shared between or be specific to human populations. The current immunogenetics resources gather the germline alleles, however, lack the population specificity of the alleles which poses limitations for disease-association studies related to immune responses in different human populations. Therefore, we systematically identified germline alleles from 26 different human populations around the world, profiled by “1000 Genomes” data. We identified 409 IGHV, 179 IGKV, and 199 IGLV germline alleles supported by at least seven haplotypes. The diversity of germline alleles is the highest in Africans. Remarkably, the variants in the identified novel alleles show strikingly conserved patterns, the same as found in other IG databases, suggesting over-time evolutionary selection processes. We could relate the genetic variants to population-specific immune responses, e.g. IGHV1-69 for flu in Africans. The population matched IG (pmIG) resource will enhance our understanding of the SHM-related B-cell receptor selection processes in (infectious) diseases and vaccination within and between different human populations.

ENTIERE IDENTITIES BETWEEN OPHIOCOMINA NIGRA IGKAPPA GENE AND HUMAN IMMUNOGLOBULIN KAPPA LOCUS.NEW ASPECTS OF INVERTEBRATE IGKAPPA GENES (IPA)

Entiere identities between Invertebrate Ophiocomina nigra IGKappa gene and Human IGK gene are confirmed, in the present work, at the level of immunoglobulin domains (constant and variable). The transcriptome of the Ophuirid : Ophiocomina nigra IGKappa gene was discovered recently(1).Since it was synthesized de novo and cloned in a pUC-GW-Kan plasmid (2) which was a gift of Bo Huang laboratories. The original sequence of the IGKappa gene, after cloning, was the following in 5’-3’ :

Clinical and biological features of B-cell neoplasms with CDK6 translocations: an association with a subgroup of splenic marginal zone lymphomas displaying frequent CD5 expression, prolymphocytic cells, and TP53 abnormalities.

A translocation involving the cyclin-dependent kinase 6 (CDK6) gene [t(CDK6)] is a rare but recurrent abnormality in B-cell neoplasms. To further characterise this aberration, we studied 57 cases; the largest series reported to date. Fluorescence in situ hybridisation analysis confirmed the involvement of CDK6 in all cases, including t(2;7)(p11;q21) immunoglobulin kappa locus (IGK)/CDK6 (n=51), t(7;14)(q21;q32) CDK6/immunoglobulin heavy locus (IGH) (n=2) and the previously undescribed t(7;14)(q21;q11) CDK6/T-cell receptor alpha locus (TRA)/T-cell receptor delta locus (TRD) (n=4). In total, 10 patients were diagnosed with chronic lymphocytic leukaemia, monoclonal B-cell lymphocytosis or small lymphocytic lymphoma, and 47 had small B-cell lymphoma (SmBL) including 36 cases of marginal zone lymphoma (MZL; 34 splenic MZLs, one nodal MZL and one bronchus-associated lymphoid tissue lymphoma). In all, 18 of the 26 cytologically reviewed cases of MZL (69%) had an atypical aspect with prolymphocytic cells. Among the 47 patients with MZL/SmBL, CD5 expression was found in 26 (55%) and the tumour protein p53 (TP53) deletion in 22 (47%). The TP53 gene was mutated in 10/30 (33%); the 7q deletion was detected in only one case, and no Notch receptor 2 (NOTCH2) mutations were found. Immunoglobulin heavy-chain variable-region (IGHV) locus sequencing revealed that none harboured an IGHV1-02*04 gene. Overall survival was 82% at 10years and not influenced by TP53 aberration. Our present findings suggest that most t(CDK6)+ neoplasms correspond to a particular subgroup of indolent marginal zone B-cell lymphomas with distinctive features.