Immunoglobulin Variable Heavy Chain Research Articles

Increased c-MYC Expression Associated with Active IGH Locus Rearrangement: An Emerging Role for c-MYC in Chronic Lymphocytic Leukemia

This review examines the pivotal role of c-MYC in Chronic Lymphocytic Leukemia (CLL), focusing on how its overexpression leads to increased genetic instability, thereby accelerating disease progression. MYC, a major oncogene, encodes a transcription factor that regulates essential cellular processes, including cell cycle control, proliferation, and apoptosis. In CLL cases enriched with unmutated immunoglobulin heavy chain variable (IGHV) genes, MYC is significantly overexpressed and associated with active rearrangements in the IGH immunoglobulin heavy chain locus. This overexpression results in substantial DNA damage, including double-strand breaks, chromosomal translocations, and an increase in abnormal repair events. Consequently, c-MYC plays a dual role in CLL: it promotes aggressive cell proliferation while concurrently driving genomic instability through its involvement in genetic recombination. This dynamic contributes not only to CLL progression but also to the overall aggressiveness of the disease. Additionally, the review suggests that c-MYC’s influence on genetic rearrangements makes it an attractive target for therapeutic strategies aimed at mitigating CLL malignancy. These findings underscore c-MYC’s critical importance in advancing CLL progression, highlighting the need for further research to explore its potential as a target in future treatment approaches.

Genetic Profiling in Chronic Lymphocytic Leukemia: The Role of TP53 Mutations and IGHV Status in Treatment Decision-Making – A Case Report

Introduction. The TP53 gene encodes the p53 protein, crucial for DNA damage response, apoptosis, and cell cycle regulation. In chronic lymphocytic leukemia (CLL), TP53 loss due to 17p deletion or mutation leads to poor chemoimmunotherapy response and shorter survival. Patients with unmutated immunoglobulin heavy chain variable (IGHV) status exhibit a more aggressive disease course, poorer outcomes, and reduced response to standard chemoimmunotherapy. These genetic variations significantly affect disease progression, treatment choice, and response to therapy. Case Report. In November 2023, a 61-year-old man presented to our clinic with complaints of generalized weakness and rapid fatigue since October 2023. CLL was diagnosed in 2018 through pathohistological and immunohistochemical analysis of the bone marrow. The patient received no therapy until 2023 due to the absence of active disease signs. From March 28, 2023, to July 25, 2023, the patient received chemoimmunotherapy with the bendamustine and rituximab (BR) regimen. Five courses of therapy were administered; however, further treatment was discontinued due to side effects that occurred during the fifth course of bendamustine administration. A subsequent diagnostic evaluation aimed at assessing treatment efficacy, prognosis, and genetic profiling included a cytomorphological analysis, which revealed that lymphocytes comprised 80% of the cellular composition. Immunocytological analysis confirmed the presence of monoclonal atypical lymphocytes, accounting for 70% of the cell population. Next-generation sequencing identified a pathogenic TP53 mutation, and fragment analysis confirmed an unmutated IGHV status. The presence of the TP53 mutation and unmutated IGHV status categorizes the patient as being in the very high-risk group, for which the use of Bruton’s tyrosine kinase inhibitors (BTKIs) and/or B-cell lymphoma-2 (BCL-2) inhibitors is recommended. Conclusions. This case highlights the significance of comprehensive genetic profiling in CLL patients using techniques such as fluorescence in situ hybridization, polymerase chain reaction, and next-generation sequencing. Such profiling detects molecular genetic alterations, facilitating personalized and effective treatment.

Chronic Lymphocytic Leukemia: Prognostic Factors in the Era of Novel Drugs.

Novel drugs have profoundly changed the outcomes in chronic lymphocytic leukemia (CLL) patients, and the traditional prognostic factors that were identified in the era of chemoimmunotherapy need to be validated in the context of these new targeted therapies. Currently, the most important prognostic genetic biomarkers are the immunoglobulin heavy chain variable (IGHV) mutational status, genetic aberrations including del(17p)/TP53 abnormalities, and the complex karyotype. In this review, we discuss the prognostic role of these genomic markers in relation to novel treatments. Moreover, we present and discuss new scoring systems that were elaborated and validated in the era of new drugs. In routine clinical practice, the application of an extensive genomic work-up with validated prognostic markers could improve the identification of "very high-risk" CLL patients who could benefit from novel, more effective targeted treatments.

Human immunoglobulin gene allelic variation impacts germline-targeting vaccine priming

Vaccine priming immunogens that activate germline precursors for broadly neutralizing antibodies (bnAbs) have promise for development of precision vaccines against major human pathogens. In a clinical trial of the eOD-GT8 60mer germline-targeting immunogen, higher frequencies of vaccine-induced VRC01-class bnAb-precursor B cells were observed in the high dose compared to the low dose group. Through immunoglobulin heavy chain variable (IGHV) genotyping, statistical modeling, quantification of IGHV1-2 allele usage and B cell frequencies in the naive repertoire for each trial participant, and antibody affinity analyses, we found that the difference between dose groups in VRC01-class response frequency was best explained by IGHV1-2 genotype rather than dose and was most likely due to differences in IGHV1-2 B cell frequencies for different genotypes. The results demonstrate the need to define population-level immunoglobulin allelic variations when designing germline-targeting immunogens and evaluating them in clinical trials.

Эффективность ибрутиниба в первой линии терапии у пациентов из группы высокого риска и во второй, третьей линиях при резистентном течении хронического лимфоцитарного лейкоза

Risk stratification appears to be the most valid criterion in decision-making regarding optimal specific therapy in chronic lymphocytic leukemia (CLL). The CLL International Prognostic Index takes account of unfavorable cytogenetic abnormalities (del(17p)/del(11q) and/or TP53 gene mutations) as well as the mutation status of immunoglobulin heavy chain variable (IGHV) region genes. Unmutated V(H)-status is commonly associated with such prognostically unfavorable genetic markers as del(17p)/del(11q), trisomy 12, and TP53 mutation. The combination of unmutated V(H)-status with unfavorable karyotype abnormalities (del(17p)/del(11q)) negatively affects the prognosis and overall survival rate. Besides, in high-risk CLL, the efficacy of therapy is rather low, and the development of refractoriness is possible. Targeted therapy (Bruton tyrosine kinase inhibitors) both in first line and in resistant CLL considerably increases the probability of achieving long-term remission. The present paper provides the comparative analysis of clinical and hematological efficacy and tolerability of ibrutinib in first-line CLL therapy of high-risk patients as well as second- and third-line therapies of resistant CLL. Ibrutinib shows high efficacy and low toxicity. First-line ibrutinib treatment results in a faster response and effectively reduces the probability of CLL progression. Second- and third-line ibrutinib treatment allows to overcome CLL resistance without impairing patients’ quality of life.

Effect of BAFF blockade on the B cell receptor repertoire and transcriptome in a mouse model of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease. Anti-B-cell-activating factor (BAFF) therapy effectively depletes B cells and reduces SLE disease activity. This research aimed to evaluate the effect of BAFF blockade on B cell receptor (BCR) repertoire and gene expression. Through next-generation sequencing, we analyzed gene expression and BCR repertoire in MRL/lpr mice that received long-term anti-BAFF therapy. Based on gene expression profiles, we predicted the relative proportion of immune cells using ImmuCellAI-mouse, validating our predictions via flow cytometry and FluoroSpot. The loss of BCR repertoire diversity and richness, along with increased clonality and differential frequency distribution of the immunoglobulin heavy chain variable (IGHV) segment gene usage, were observed in BAFF-blockade mice. Meanwhile, the distribution of complementarity-determining region 3 (CDR3) length and CDR3 amino acid usage remained unaffected. BAFF blockade resulted in extensive changes in gene expression, particularly that of genes related to B cells and immunoglobulins. Besides, the tumor necrosis factor (TNF)-α responses and interferon (IFN)-α/γ were downregulated, consistent with the decrease in IFN-γ and TNF-α serum levels following anti-BAFF therapy. In addition, BAFF blockade significantly reduced B cell subpopulations and plasmacytoid dendritic cells, and caused the depletion of antibody-secreting cells. Our comparative BCR repertoire and transcriptome analyses of MRL/lpr mice subjected to BAFF blockade provide innovative insights into the molecular pathophysiology of SLE.

Association of Cytogenetics Aberrations and IGHV Mutations with Outcome in Chronic Lymphocytic Leukemia Patients in a Real-World Clinical Setting.

Immunoglobulin heavy chain variable ( IGHV ) region mutations, TP53 mutation, fluorescence in situ hybridization (FISH), and cytogenetic analysis are the most important prognostic biomarkers used in chronic lymphocytic leukemia (CLL) patients in our daily practice. In real-life environment, there are scarce studies that analyze the correlation of these factors with outcome, mainly referred to time to first treatment (TTFT) and overall survival (OS). This study aimed to typify IGHV mutation status, family usage, FISH aberrations, and complex karyotype (CK) and to analyze the prognostic impact in TTFT and OS in retrospective study of 375 CLL patients from a Spanish cohort. We found unmutated CLL (U-CLL) was associated with more aggressive disease, shorter TTFT (48 vs. 133 months, p < 0.0001), and shorter OS (112 vs. 246 months, p < 0.0001) than the mutated CLL. IGHV3 was the most frequently used IGHV family (46%), followed by IGHV1 (30%) and IGHV4 (16%). IGHV5-51 and IGHV1-69 subfamilies were associated with poor prognosis, while IGHV4 and IGHV2 showed the best outcomes. The prevalence of CK was 15% and was significantly associated with U-CLL. In the multivariable analysis, IGHV2 gene usage and del13q were associated with longer TTFT, while VH1-02, +12, del11q, del17p, and U-CLL with shorter TTFT. Moreover, VH1-69 usage, del11q, del17p, and U-CLL were significantly associated with shorter OS. A comprehensive analysis of genetic prognostic factors provides a more precise information on the outcome of CLL patients. In addition to FISH cytogenetic aberrations, IGHV and TP53 mutations, IGHV gene families, and CK information could help clinicians in the decision-making process.

Broad Superiority of Zanubrutinib (Zanu) Over Bendamustine + Rituximab (BR) Across Multiple High-Risk Factors: Biomarker Subgroup Analysis in the Phase 3 SEQUOIA Study in Patients With Treatment-Naive (TN) Chronic Lymphocytic Leukemia (CLL)/Small Lymphocytic Lymphoma (SLL) without del(17p)

Introduction Zanu is a Bruton tyrosine kinase (BTK) inhibitor with high potency, selectivity, and efficacy and a favorable toxicity profile. In the phase 3 SEQUOIA study (NCT03336333; Tam et al. Lancet Oncol. 2022), zanu treatment demonstrated superior progression-free survival (PFS) in TN patients (pts) with CLL/SLL and without del(17p) (cohort 1) compared with BR treatment (hazard ratio [HR], 0.42; 95% CI, 0.28-0.63; 2-sided P&amp;lt;.0001). We evaluated PFS in both treatment arms in pt subgroups based on various biomarkers, including several known negative prognostic factors for CLL. Methods Details of the SEQUOIA study were described previously (Tam et al. Lancet Oncol. 2022). A total of 479 pts in cohort 1 were randomized to either zanu (n=241) or BR (n=238). Blood (CLL) or bone marrow (SLL) samples collected at screening were used for fluorescence in situ hybridization for chromosome abnormalities, cytogenetic analysis for complex karyotype (CK), next-generation sequencing (NGS) per the European Research Initiative on CLL (ERIC) for immunoglobulin heavy chain variable (IGHV) gene mutations and expressed clones, and ultrasensitive targeted NGS for mutation analysis of 106 genes. For NGS, all pathogenic mutations with variant allele frequency ≥1% were analyzed. The association between biomarkers and PFS was quantified using the log-rank test and HR and summarized by the Kaplan-Meier method. Data cutoff was October 31, 2022. Results Overall, the CLL features analyzed were similarly distributed between both treatment arms (Table). In pts with cytogenetic abnormalities, zanu demonstrated significantly better PFS than BR in those with del(11q) ( P&amp;lt;.001), del(13q) ( P&amp;lt;.001), trisomy 12 ( P&amp;lt;.01), or CKT ≥3 ( P&amp;lt;.01) (Table). Furthermore, zanu treatment conferred a similar PFS benefit to pts with the negative prognostic factor, del(11q) ( P=.05) or intermediate prognostic factor, trisomy 12 ( P=.40), compared to those without these abnormalities (Table). Notably, in the zanu arm, CKT ≥3 was not associated with worse PFS ( P=.18; Table). Pts with either mutated IGHV (mIGHV) or unmutated IGHV (uIGHV) in the zanu arm had significantly better PFS than pts in the BR arm (uIGHV: P&amp;lt;.0001; mIGHV: P&amp;lt;.01; Table); analysis was confirmed by an ERIC-certified provider. Furthermore, PFS was unaffected by IGHV mutational status in pts treated with zanu ( P=.12). In pts with uIGHV, IGHV1-69 was the most prevalent expressed clone in both arms (zanu: 24.6% [31/126]; BR: 30.7% [39/127]). In the present study, pts with uIGHV harboring IGHV1-69 clones showed significantly better PFS with zanu vs BR ( P&amp;lt;.0001). Across all pts, the most frequently mutated genes were ATM (zanu: 11%; BR: 16%), SF3B1 (zanu: 17%; BR: 21%), NOTCH1 (zanu: 20%; BR: 20%), and BRAF (zanu: 11%; BR: 7%; Table). Pts with mutations associated with poor prognosis in CLL had significantly better PFS with zanu than with BR (eg, ATM [ P=.02], BRAF [ P=.01], NOTCH1 [ P&amp;lt;.001], SF3B1 [ P&amp;lt;.001]; Table). Furthermore, zanu-treated pts with or without mutations in ATM ( P=.58), NOTCH1 ( P=.38), and SF3B1 ( P=.39) had similar PFS. Conclusions TN del(17p)-negative pts with CLL/SLL were evenly distributed between zanu and BR arms in SEQUOIA cohort 1 based on the biomarkers analyzed. PFS in zanu-treated pts was superior to that of BR-treated pts in all biomarker subgroups analyzed, including some known negative prognostic markers in CLL such as del11q, CKT≥3, and uIGHV. Importantly, within the zanu-treatment arm, pts with negative prognostic biomarkers showed comparable PFS benefit to pts without those markers. Like with other BTK inhibitors, ibrutinib and acalabrutinib, IGHV mutational status did not affect PFS outcome (Bartosz et al. Hematology in Clinical Practice 2022). However, contrary to what has been reported for TN or relapsed/refractory pts treated with ibrutinib-based regimens, CKT ≥3 was not associated with worse PFS in zanubrutinib-treated patients (Rigolin et al. Blood. 2021; Thompson et al. Cancer. 2015). This study provides further evidence that zanu is a valuable first-line treatment option for pts with CLL/SLL.

Whole Genome Classification of Pre-Malignant B-Cells Disorder of the Oxplored Study

Background. Chronic lymphocytic leukaemia (CLL) is always preceded by preclinical clonal B-cell disorders such as monoclonal B-cell lymphocytosis (MBL). Pre-malignant clonal B-cells are identifiable in asymptomatic individuals, a minority of whom will progress to symptomatic CLL. While some people remain at pre-cancerous or asymptomatic early stage CLL, others experience clinically aggressive disease. There is currently no method to effectively stratify individuals at higher risk of developing symptomatic CLL. Despite recent advances in treatment options available, the disease remains incurable. Therefore, we need to expand our knowledge and improve current classification methods. Here, we propose a molecular classifier using whole genome sequencing (WGS). This classifier was obtained by performing genomic characterization in pre-malignancy / early stages of the disease and comparing the genomic subgroups with those of symptomatic CLL. Methods. Individuals with newly diagnosed monoclonal B-cell lymphocytosis and early asymptomatic chronic lymphocytic leukaemia were enrolled in the OXPLORED clinical trial (Oxford Pre-cancerous Lymphoproliferative Disorders: Analysis and Interception study). We performed WGS in 400 samples from 200 individuals (sorted CD19+ B-cells as tumour, and matched salivary DNA as germline) to detect somatic alterations. We derived immunoglobulin heavy chain variable (IGHV) mutational status, stereotype and an additional 186 genomic features as previously described (Robbe*, Ridout* et al. Nature Genetics 2022) including known and recently discovered candidate drivers of CLL, recurrent structural variants, mutational signatures, genomic complexity measures, mutational burden, and pathway alterations. All the data was compiled into a matrix to extract meaningful sets of features to cluster patients' genomes using non-negative matrix factorization (NMF). Genomic findings were compared to the largest CLL whole genome cohort of symptomatic patients requiring frontline treatment (n=443). Results. The IGHV mutational status was found unmutated in 31% of individuals and hypermutated in 69% (excluding missing data for 6 genomes). Next, we considered mutations and CNAs in 58 common CLL drivers and 34 regions with recurrent CNAs. Although numbers were lower than in frontline CLL, most individuals presented at least one driver (86%) or more (57%) (by comparison, the CLL frontline cohort presented at least one CLL driver in 98% of patients). Genomic complexity, defined as 4 or more CNAs was detected in 12%, and complex genome defined as the presence of both CN gains and CN losses in 22%, indicating that newly diagnosed monoclonal B-cell lymphocytosis and early asymptomatic CLL present a relatively high degree of genomic complexity similar to what was observed in frontline CLL. The most common driver was del13q (60%), including as a sole driver in a third of these genomes. Other recurrent alterations were IGLL5 mutations (20%), trisomy 12 (9%), and mutations in MYD88 (8%), CREBBP (5%), NOTCH1 (5%), and SPEN (5%). Noncoding elements were also found mutated, including 30 promoters (including BIRC3 in 7%), five UTRs and eight enhancers, including BCL6 and PAX5 enhancers in 18% and 3.4% of individuals, respectively. When comparing this cohort with CLL genomes, we found that alterations in the main cancer pathways were depleted in OXPLORED, including known drivers such as ATM, NOTCH1, SF3B1. Finally, moving away from single-alteration grouping, we clustered the 643 genomes (443 CLL + 200 OXPLORED) using 186 genomic features by applying NMF. Importantly, we found distinct genomic profiles in the early disease cohort, including a subgroup like symptomatic CLL at frontline and another distinct subgroup, hinting towards identifying a genomic subgroup at higher risk of progressing to CLL. Conclusion: The comprehensive characterisation of genomic events that determine progression to malignancy are essential to understand the mechanisms of disease progression. Our study opens new horizons towards identifying individuals at higher risk and might pinpoint to individuals who need early intervention with curative intent. Therefore, we propose to analyse newly generated whole-genome sequencing (WGS) data to establish genomic subgroups in early CLL / pre-malignancy stages.

Enrichment in Metabolic Pathway Activation Corresponds to Immunoglobulin Gene Diversity across B Cell Developmental Stages in B-Lymphoblastic Leukemia

Background: Intraclonal genetic variation in the immunoglobulin heavy chain variable gene (IGHV) has been widely documented in B-lymphoblastic leukemia (B-ALL), but its biologic significance as a presumed reflection of the B cell stage of leukemic transformation has not been systematically evaluated. Using ultradeep, targeted sequencing of the rearranged IgH gene in 22 patients with B-ALL, we previously demonstrated that there are subsets of patients with either extensive or minimal diversity in recombination activating gene (RAG)-mediated variable (V), diversity (D), and joining (J) gene rearrangements and that gene expression profiling (GEP) reveals enrichment of oxidative phosphorylation (OXPHOS), glycolysis, and fatty acid metabolism Hallmark pathways among cases with V-DJ rearrangement diversity (Fries et al. ASH 2022). We observed enrichment in these same metabolic signatures among leukemia cells with a pre-B cell phenotypic signature found to be predictive of relapse (Good et al. Nat Med 2018; Liu et al. ASH 2021). To understand the functional implications of this metabolic activation observed among cases with IgH diversity, we applied cytometry by time of flight (CyTOF) phenotyping to determine if IgH clonal composition reflects the metabolic and proliferative activation inherent to B cell stage of origin which may have relevance to disease behavior and outcome. Methods: Using viably-frozen, pre-treatment bone marrow (BM) and/or peripheral blood (PB) biospecimens from a cohort of 18 patients with B-ALL with known IgH clonal composition (7 with extensive V-DJ diversity, 8 without diversity, and 3 lacking any dominant clonal sequence), we performed deep phenotyping by mass cytometry and compared signaling pathway activation patterns between cohorts and compared to healthy controls. Samples were analyzed by mass cytometry with a 40-marker panel including B cell developmental phenotypic and metabolic proteins. Developmental classification was performed as previously described (Good et al. 2018). To test statistical significance in frequency of each subpopulation between two groups, we applied a multiple unpaired t-test with correction by Holm-Sidak method. Results: We discovered that all leukemia samples - regardless of IgH clonal composition - were significantly enriched for phenotypic features reflecting a pro-BII cell state, whereas enrichment of other more or less mature cell stages varied according to IgH composition. Developmental classification demonstrated that cases lacking a clonal IgH rearrangement (N=3) - presumed to have derived from a B cell stage preceding an initial DJ joining event - were enriched at the pro-BII population (P&amp;lt;0.0001), as were cases with extensive V-DJ diversity (N=7; P=0.019), and those lacking in diversity (N=8; P=0.0007) compared to healthy BM. However, cases with V-DJ diversity were uniformly enriched for OXPHOS, glycolytic, and pentose phosphate pathway (PPP)-associated protein expression compared to those without V-DJ diversity. In cells with a pro-BII phenotype, differentially expressed proteins between diverse and non-diverse cases included proteins essential for glycolysis (GLUT1, ENO1, PKM1), PPP (PGD, TKT), and OXPHOS (SDHA, CS, ATPA5, CytC). Conclusions: Cellular metabolism is a known hallmark of cancer proliferation, leukemia stem cell maintenance, and therapeutic escape, just as genetic diversification is integral to tumor evolution. Using primary B-ALL specimens, we show that metabolic pathway activation coincides with extensive RAG-mediated IGHV gene diversification across B cell developmental phenotypes. Contrary to the canonical assumption in B-ALL that V-DJ rearrangement and diversity is tied to developmental state, our analysis suggests that all cases are enriched at the proB-preB transition, but with differences in cellular metabolism that distinguish the diverse from homogeneous rearrangement state. These data suggest that IgH composition is not merely a passive genetic signature exploitable for tracking purposes in B-ALL, but may also inherently reflect underlying biology relevant to clinical outcomes.

High-throughput Proteomics Identifies THEMIS2 as Independent Biomarker of Treatment-free Survival in Untreated CLL.

It remains challenging in chronic lymphocytic leukemia (CLL) to distinguish between patients with favorable and unfavorable time-to-first treatment (TTFT). Additionally, the downstream protein correlates of well-known molecular features of CLL are not always clear. To address this, we selected 40 CLL patients with TTFT ≤24 months and compared their B cell intracellular protein expression with 40 age- and sex-matched CLL patients with TTFT >24 months using mass spectrometry. In total, 3268 proteins were quantified in the cohort. Immunoglobulin heavy-chain variable (IGHV) mutational status and trisomy 12 were most impactful on the CLL proteome. Comparing cases to controls, 5 proteins were significantly upregulated, whereas 3 proteins were significantly downregulated. Of these, only THEMIS2, a signaling protein acting downstream of the B cell receptor, was significantly associated with TTFT, independently of IGHV and TP53 mutational status (hazard ratio, 2.49 [95% confidence interval, 1.62-3.84]; P < 0.001). This association was validated on the mRNA and protein level by quantitative polymerase chain reaction and ELISA, respectively. Analysis of 2 independently generated RNA sequencing and mass spectrometry datasets confirmed the association between THEMIS2 expression and clinical outcome. In conclusion, we present a comprehensive characterization of the proteome of untreated CLL and identify THEMIS2 expression as a putative biomarker of TTFT.

Affinity-matured homotypic interactions induce spectrum of PfCSP structures that influence protection from malaria infection

The generation of high-quality antibody responses to Plasmodium falciparum (Pf) circumsporozoite protein (PfCSP), the primary surface antigen of Pf sporozoites, is paramount to the development of an effective malaria vaccine. Here we present an in-depth structural and functional analysis of a panel of potent antibodies encoded by the immunoglobulin heavy chain variable (IGHV) gene IGHV3-33, which is among the most prevalent and potent antibody families induced in the anti-PfCSP immune response and targets the Asn-Ala-Asn-Pro (NANP) repeat region. Cryo-electron microscopy (cryo-EM) reveals a remarkable spectrum of helical antibody-PfCSP structures stabilized by homotypic interactions between tightly packed fragments antigen binding (Fabs), many of which correlate with somatic hypermutation. We demonstrate a key role of these mutated homotypic contacts for high avidity binding to PfCSP and in protection from Pf malaria infection. Together, these data emphasize the importance of anti-homotypic affinity maturation in the frequent selection of IGHV3–33 antibodies and highlight key features underlying the potent protection of this antibody family.

Targeting conditioned media dependencies and FLT-3 in chronic lymphocytic leukemia

AbstractThe importance of the stromal microenvironment in chronic lymphocytic leukemia (CLL) pathogenesis and drug resistance is well established. Despite recent advances in CLL therapy, identifying novel ways to disrupt interactions between CLL and its microenvironment may identify new combination partners for the drugs currently in use. To understand the role of microenvironmental factors on primary CLL cells, we took advantage of an observation that conditioned media (CM) collected from stroma was protective of CLL cells from spontaneous cell death ex vivo. The cytokine in the CM-dependent cells that most supports CLL survival in short-term ex vivo culture was CCL2. Pretreatment of CLL cells with anti-CCL2 antibody enhanced venetoclax-mediated killing. Surprisingly, we found a group of CLL samples (9/23 cases) that are less likely to undergo cell death in the absence of CM support. Functional studies revealed that CM-independent (CMI) CLL cells are less sensitive to apoptosis than conventional stroma-dependent CLL. In addition, a majority of the CMI CLL samples (80%) harbored unmutated immunoglobulin heavy-chain variable (IGHV) region. Bulk-RNA sequence analysis revealed upregulation of the focal adhesion and RAS signaling pathways in this group, along with expression of fms-like tyrosine kinase 3 (FLT3) and CD135. Treatment with FLT3 inhibitors caused a significant reduction in cell viability among CMI samples. In summary, we were able to discriminate and target 2 biologically distinct subgroups of CLL based on CM dependence with distinct microenvironmental vulnerabilities.

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

The development of some lymphomas has been associated with infections caused by bacterial species discovered in the 1980s, for example, Helicobacter pylori and Borrelia burgdorferi s.l. The first cases of human infection with a bacterial species that was first described in 2004, the tick-borne bacterium Neoehrlichia mikurensis were published in 2010. Patients with malignant B cell lymphomas emerged as a risk group for severe cases of infection, presenting with fever of unknown cause and venous thromboembolism. The infection is missed by routine microbiologic diagnostic procedures such as blood culture and can only be detected by PCR. Vascular endothelium is a likely target of N. mikurensis infection. Asymptomatic carriage of the infection for months to years appears to occur. We hypothesized that N. mikurensis causes latent infections that can reactivate when B cell defenses are compromised. It was whilst conducting a study of patients with malignant B cell lymphomas scheduled to receive treatment with rituximab that we discovered several patients who had the infection already before the start of treatment. This led us to hypothesize that persistent latent infections with N. mikurensis might contribute to the development of certain cases of malignant B cell lymphoma. Splenic engagement, restricted repertoires of the Immunoglobulin heavy chain variable (IGHV) regions, and mutations of the IGHV regions from the germline configuration featured among these cases of lymphoma, which encompassed chronic lymphocytic leukemia, splenic marginal zone lymphoma, mantle cell lymphoma and non-classified indolent splenic lymphoma. Remarkably, three out of five patients could cease lymphoma therapy after eradication of the infection. Our aim is to confirm and expand these findings of a possible causality between N. mikurensis infection and the development of malignant B cell lymphomas. To this end, we are starting a prospective study of the prevalence of N. mikurensis infection in newly diagnosed patients with malignant B cell lymphomas, and the response of such lymphomas to eradication of the infection. We will also attempt to identify a genetic signature of N. mikurensis infection by studying IGHV gene usage, the mutations induced by somatic hypermutations, as well as the physicochemical properties of the complementarity-determining region 3 (CDR3), the most hypervariable part of the B cell receptor of infected patients. This will help establish if it is mainly post-germinal center B cells that undergo malignant B cell transformation in cases of N. mikurensis-associated lymphoma. The research was funded by: the Swedish Research Council, the Swedish Cancer Society, the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement, and the Cancer and Allergy Foundation. Keywords: indolent non-Hodgkin lymphoma, tumor biology and heterogeneity, chronic lymphocytic leukemia (CLL) No conflicts of interests pertinent to the abstract.

Diffuse Large B-cell Lymphoma Involving an Abundant Infiltration of T Follicular Helper Cells: A Case Report.

A 76-year-old man presented with skin plaque and splenic nodules, and diffuse large B-cell lymphoma (DLBCL) with infiltration of T-cells was suspected based on the skin lesions. The disease showed indolent clinical behavior for three months, when systemic lymphadenopathy rapidly evolved. An inguinal lymph node biopsy revealed DLBCL with abundant infiltration of T follicular helper (TFH) cells. A polymerase chain reaction-based analysis of immunoglobulin variable heavy chain showed that the skin, splenic nodules, and inguinal lymph node shared the same clone. This case indicates that the dysregulated infiltration of TFH cells in the tumor microenvironment accelerates the lymphomagenesis and progression of DLBCL.

Clonotypic analysis of immunoglobulin heavy chain sequences among 44 patients with Waldenström macroglobulinemia

To analyze the correlation between the mutational status of immunoglobulin heavy chain variable (IGHV) gene with the prognosis of patients with Waldenström macroglobulinemia (WM). Immunoglobulin heavy chain gene (IGH) clonotypic sequence analysis was carried out to assess the mutational status of IGHV in the blood and/or bone marrow samples from 44 WM patients. The usage characteristics of IGHV-IGHD-IGHJ gene was explored. The most common IGHV subgroup was IGHV3, which was similar to the data from the Institute of Hematology of Chinese Academy of Medical Science. IGHV3-23 (20.45% vs. 15.44%) and IGHV3-74 (11.36% vs. 7.35%) were the main fragments used, which was followed by IGHV4 gene family (15.91% vs. 24.26%). However, no significant correlation was found between the IGHV4 usage and the prognosis of the patients. Should 98% be taken as the cut-off value for the IGHV mutation status, only 5 patients had no IGHV variant, and there was no correlation with the prognosis. Based on the X-tile analysis, 92.6% was re-selected as the cut-off value for the IGHV variant status in such patients. LDH was increased in 26 patients (59.1%) without IGHV variant (P < 0.05), whilst progression-free survival (P < 0.05) and overall survival (P < 0.05) were significantly shorter compared with those with IGHV variants. The usage characteristics of IGHV-IGHD-IGHJ in our patients was similar to reported by the Institute of Hematology of Chinese Academy of Medical Science, albeit that no correlation was found between the IGHV4 usage and the prognosis of the patients. Furthermore, 98% may not be appropriate for distinguishing the IGHV variant status in WM patients.

Frequent use of IGHV3-30-3 in SARS-CoV-2 neutralizing antibody responses.

The antibody response to SARS-CoV-2 shows biased immunoglobulin heavy chain variable (IGHV) gene usage, allowing definition of genetic signatures for some classes of neutralizing antibodies. We investigated IGHV gene usage frequencies by sorting spike-specific single memory B cells from individuals infected with SARS-CoV-2 early in the pandemic. From two study participants and 703 spikespecific B cells, the most used genes were IGHV1-69, IGHV3-30-3, and IGHV3-30. Here, we focused on the IGHV3-30 group of genes and an IGHV3-30-3-using ultrapotent neutralizing monoclonal antibody, CAB-F52, which displayed broad neutralizing activity also in its germline-reverted form. IGHV3-30-3 is encoded by a region of the IGH locus that is highly variable at both the allelic and structural levels. Using personalized IG genotyping, we found that 4 of 14 study participants lacked the IGHV3-30-3 gene on both chromosomes, raising the question if other, highly similar IGHV genes could substitute for IGHV3-30-3 in persons lacking this gene. In the context of CAB-F52, we found that none of the tested IGHV3-33 alleles, but several IGHV3-30 alleles could substitute for IGHV3-30-3, suggesting functional redundancy between the highly homologous IGHV3-30 and IGHV3-30-3 genes for this antibody.

Characterization of clonal immunoglobulin heavy V-D-J gene rearrangements in Chinese patients with chronic lymphocytic leukemia: Clinical features and molecular profiles.

Several prognostic factors of chronic lymphocytic leukemia (CLL) have been identified, such as cytogenetic aberrations and recurrent gene mutations. B-cell receptor (BCR) signaling plays an important role in the tumorigenesis of CLL, and its clinical significance in predicting prognosis is also under study. Therefore, we assessed the already-known prognostic markers, immunoglobulin heavy chain (IGH) gene usage and the associations among these factors in 71 patients diagnosed with CLL in our center from October 2017 to March 2022. Sequencing of IGH gene rearrangements was performed using Sanger sequencing or IGH-based next-generation sequencing, and the results were further analyzed for distinct IGH/IGHD/IGHJ genes and the mutational status of the clonotypic IGHV (IGH variable) gene. In summary, by analyzing the distribution of potential prognostic factors in CLL patients, we displayed a landscape of molecular profiles, confirmed the predictive value of recurrent genetic mutations and chromosome aberrations, and found that IGHJ3 was associated with favorable markers (mutated IGHV, trisomy 12), while IGHJ6 tended to correlate with unfavorable factors (unmutated IGHV, del17p). These results provided an indication for IGH gene sequencing in predicting the prognosis of CLL.

OBINUTUZUMAB FOR THE TREATMENT OF CHRONIC LYMPHOCYTIC LEUKEMIA PATIENTS: SINGLE CENTER EXPERIENCE

Monoclonal antibodies (mAbs) targeting CD20 molecule on B lymphocyte are of great importance in the treatment of B-cell malignancies. In recent years a great effort has been put in developing novel mAbs that can provide greater efficacy than the well-known rituximab. A second class of mAbs obinutuzumab has been presented as a more powerful tool in the treatment of this group of patients. In this retrospective study 70 patients with symptomatic CLL were included. CLL patients were diagnosed and treated at the University Clinic for Hematology between January 2018 and January 2022. All patients were evaluated for traditional clinical and laboratory prognostic factors and newer prognostic factors including IGHV mutation status and CLL prognostic and predictive genetic abnormalities. Most of the patients treated with obinutuzumab had Binet B stage (56%). Mutational status of the immunoglobulin variable region heavy chain (IGHV) in most of CLL patients treated with obinutuzumab was unmated IGHV gene. The most frequently encountered adverse events were tumor lysis syndrome and leukopenia. The analysis of the initial results of the application of obinutuzumab-based therapy allows us to conclude that this therapeutical modality is not associated with severe adverse events that would limit the administration of therapy.

Diversification of immunoglobulin genes by gene conversion in the domestic chicken (Gallus gallus domesticus).

Sustainable modern poultry production depends on effective protection against infectious diseases and a diverse range of antibodies is key for an effective immune response. In the domestic chicken, somatic gene conversion is the dominant process in which the antibody immunoglobulin genes are diversified. Affinity maturation by somatic hypermutation (SHM) also occurs, but the relative contribution of gene conversion versus somatic hypermutation to immunoglobulin (Ig) gene diversity is poorly understood. In this study, we use high throughput long-read sequencing to study immunoglobulin diversity in multiple immune-associated tissues in Rhode Island Red chickens. To better understand the impact of genetic diversification in the chicken, a novel gene conversion identification software was developed (BrepConvert). In this study, BrepConvert enabled the identification of over 1 million gene conversion events. Mapping the occurrence of putative somatic gene conversion (SGC) events throughout the variable gene region revealed repetitive and highly restricted patterns of genetic insertions in both the antibody heavy and light chains. These patterns coincided with the locations of genetic variability in available pseudogenes and align with antigen binding sites, predominately the complementary determining regions (CDRs). We found biased usage of pseudogenes during gene conversion, as well as immunoglobulin heavy chain diversity gene (IGHD) preferences during V(D)J gene rearrangement, suggesting that antibody diversification in chickens is more focused than the genetic potential for diversity would suggest.