SARS-CoV-2 vaccine responses following CD20-depletion treatment in patients with haematological and rheumatological disease: a West Midlands Research Consortium study

B cell depleting agents are amongst the most commonly used drugs to treat haemato-oncological and autoimmune diseases. They rapidly induce a state of peripheral B cell aplasia with the potential to interfere with nascent vaccine responses, particularly to novel antigens. We have examined the relationship between B cell reconstitution and SARS-CoV-2 vaccine responses in two cohorts of patients previously exposed to B cell depleting agents: a cohort of patients treated for haematological B cell malignancy and another treated for rheumatological disease. B cell depletion severely impairs vaccine responsiveness in the first 6 months after administration: SARS-CoV-2 antibody seroprevalence was 42.2% and 33.3% in the haemato-oncological patients and rheumatology patients respectively and 22.7% in patients vaccinated while actively receiving anti-lymphoma chemotherapy. After the first 6 months, vaccine responsiveness significantly improved during early B cell reconstitution, however, the kinetics of reconstitution was significantly faster in haemato-oncology patients. The AstraZeneca ChAdOx1 nCoV-19 vaccine and the Pfizer BioNTech 162b vaccine induced equivalent vaccine responses, however shorter intervals between vaccine doses (<1m) improved the magnitude of the antibody response in haeamto-oncology patients. In a subgroup of haemato-oncology patients, with historic exposure to B cell depleting agents (>36m previously) vaccine non-responsiveness was independent of peripheral B cell reconstitution. The findings have important implications for primary vaccination and booster vaccination strategies in individuals clinically vulnerable to SARS-CoV-2.

Thrombotic Microangiopathy, an Unusual Form of Monoclonal Gammopathy of Renal Significance: Report of 3 Cases and Literature Review

Monoclonal gammopathies result from neoplastic clones of the B-cell lineage and may cause kidney disease by various mechanisms. When the underlying clone does not meet criteria for a malignancy requiring treatment, the paraprotein is called a monoclonal gammopathy of renal significance (MGRS). One rarely reported kidney lesion associated with benign paraproteins is thrombotic microangiopathy (TMA), provisionally considered as a combination signifying MGRS. Such cases may lack systemic features of TMA, such as a microangiopathic hemolytic anemia, and the disease may be kidney limited. There is no direct deposition of the paraprotein in the kidney, and the presumed mechanism is disordered complement regulation. We report three cases of kidney limited TMA associated with benign paraproteins that had no other detectable cause for the TMA, representing cases of MGRS. Two of the cases are receiving clone directed therapy, and none are receiving eculizumab. We discuss in detail the pathophysiological basis for this possible association. Our approach to therapy involves first ruling out other causes of TMA as well as an underlying B-cell malignancy that would necessitate direct treatment. Otherwise, clone directed therapy should be considered. If refractory to such therapy or the disease is severe and multisystemic, C5 inhibition (eculizumab or ravulizumab) may be indicated as well.

Selection of a Nuclease-Resistant RNA Aptamer Targeting CD19

The transmembrane glycoprotein cluster of differentiation 19 (CD19) is a B cell–specific surface marker, expressed on the majority of neoplastic B cells, and has recently emerged as a very attractive biomarker and therapeutic target for B-cell malignancies. The development of safe and effective ligands for CD19 has become an important need for the development of targeted conventional and immunotherapies. In this regard, aptamers represent a very interesting class of molecules. Additionally referred to as ‘chemical antibodies’, they show many advantages as therapeutics, including low toxicity and immunogenicity. Here, we isolated a nuclease-resistant RNA aptamer binding to the human CD19 glycoprotein. In order to develop an aptamer also useful as a carrier for secondary reagents, we adopted a cell-based SELEX (Systematic Evolution of Ligands by EXponential Enrichment) protocol adapted to isolate aptamers able to internalise upon binding to their cell surface target. We describe a 2′-fluoro pyrimidine modified aptamer, named B85.T2, which specifically binds to CD19 and shows an exquisite stability in human serum. The aptamer showed an estimated dissociation constant (KD) of 49.9 ± 13 nM on purified human recombinant CD19 (rhCD19) glycoprotein, a good binding activity on human B-cell chronic lymphocytic leukaemia cells expressing CD19, and also an effective and rapid cell internalisation, thus representing a promising molecule for CD19 targeting, as well as for the development of new B-cell malignancy-targeted therapies.

A POLE Splice Site Deletion Detected in a Patient with Biclonal CLL and Prostate Cancer: A Case Report

Chronic lymphocytic leukemia (CLL) is considered a clonal B cell malignancy. Sporadically, CLL cases with multiple productive heavy and light-chain rearrangements were detected, thus leading to a bi- or oligoclonal CLL disease with leukemic cells originating either from different B cells or otherwise descending from secondary immunoglobulin rearrangement events. This suggests a potential role of clonal hematopoiesis or germline predisposition in these cases. During the screening of 75 CLL cases for kappa and lambda light-chain rearrangements, we could detect a single case with CLL cells expressing two distinct kappa and lambda light chains paired with two separate immunoglobulin heavy-chain variable regions. Furthermore, this patient also developed a prostate carcinoma. Targeted genome sequencing of highly purified light-chain specific CLL clones from this patient and from the prostate carcinoma revealed the presence of a rare germline polymorphism in the POLE gene. Hence, our data suggest that the detected SNP may predispose for cancer, particularly for CLL.

Longitudinal analyses of CLL in mice identify leukemia-related clonal changes including a Myc gain predicting poor outcome in patients

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy mainly occurring at an advanced age with no single major genetic driver. Transgenic expression of TCL1 in B cells leads after a long latency to a CLL-like disease in aged Eµ-TCL1 mice suggesting that TCL1 overexpression is not sufficient for full leukemic transformation. In search for secondary genetic events and to elucidate the clonal evolution of CLL, we performed whole exome and B-cell receptor sequencing of longitudinal leukemia samples of Eµ-TCL1 mice. We observed a B-cell receptor stereotypy, as described in patients, confirming that CLL is an antigen-driven disease. Deep sequencing showed that leukemia in Eµ-TCL1 mice is mostly monoclonal. Rare oligoclonality was associated with inability of tumors to develop disease upon adoptive transfer in mice. In addition, we identified clonal changes and a sequential acquisition of mutations with known relevance in CLL, which highlights the genetic similarities and therefore, suitability of the Eµ-TCL1 mouse model for progressive CLL. Among them, a recurrent gain of chromosome 15, where Myc is located, was identified in almost all tumors in Eµ-TCL1 mice. Interestingly, amplification of 8q24, the chromosomal region containing MYC in humans, was associated with worse outcome of patients with CLL.

The Biology of Classic Hairy Cell Leukemia

Classic hairy cell leukemia (HCL) is a rare mature B-cell malignancy associated with pancytopenia and infectious complications due to progressive infiltration of the bone marrow and spleen. Despite tremendous therapeutic advances achieved with the implementation of purine analogues such as cladribine into clinical practice, the culprit biologic alterations driving this fascinating hematologic disease have long stayed concealed. Nearly 10 years ago, BRAF V600E was finally identified as a key activating mutation detectable in almost all HCL patients and throughout the entire course of the disease. However, additional oncogenic biologic features seem mandatory to enable HCL transformation, an open issue still under active investigation. This review summarizes the current understanding of key pathogenic mechanisms implicated in HCL and discusses major hurdles to overcome in the context of other BRAF-mutated malignancies.

A hajas sejtes leukémia korszerű diagnosztikája és kezelése

Összefoglaló. A hajas sejtes leukémia (HCL) egy indolens lefolyású ritka B-sejtes lymphoma. Diagnosztikájában jellegzetes morfológiai képén túlmenően a sejtek felszínén megtalálható markerek azonosítása áramlási citometriával, valamint a betegségben előforduló specifikus fehérjék immunhisztokémiai detektálása jelenti a rutineljárást. Kiemelt szerepet tölt be a differenciáldiagnosztikában a BRAF V600E mutációjának a kimutatása, melyre ma már számos módszer áll rendelkezésre, mint például az immunhisztokémia, pyroszekvenálás, allélspecifikus PCR vagy a droplet digitalis PCR. A tumorsejtek jelátviteli rendszerében és szabályozásában azonban a BRAF mutációjának következtében kialakuló folyamatos aktivitása mellett egyéb mechanizmusok is szerepet játszhatnak, többek között növekedési faktorok, interleukinek, adhéziós fehérjék vagy éppen mikro-RNS-ek. A patomechanizmus egyre részletesebb megismerése érdekében egyéb daganatokhoz hasonlóan a HCL-ben is aktív kutatások folynak a genetikai háttér feltérképezésére új generációs szekvenálás segítségével. Leírtak már nagy százalékban előforduló mutációkat a CDKN1B-, KLF2- és KMT2C-gének esetében, továbbá egyéb génekben is alacsonyabb előfordulási aránnyal. Genetikailag, sőt klinikai manifesztáció és terápiás válasz alapján is jelentős eltérések láthatóak a klasszikus és variáns HCL-es betegek között, elkülönítésük épp ezért rendkívül fontos. Míg a klasszikus esetben első vonalban alkalmazott purin nukleozid analógok kiemelkedő válaszreakciót képesek kiváltani, a variáns HCL-es betegek gyakran refrakterek a kezelésre, és esetükben a célzott BRAF-gátlók szintén hatástalanok. Számos klinikai kutatás zajlik a jelenleg is alkalmazott terápiás szerek optimalizálása, kombinációban történő alkalmazása, valamint egyéb lymphoid daganatokban alkalmazott gyógyszerek és új támadáspontok ellen tervezett molekuláknak a HCL kezelésébe történő bevonása céljából. Summary. Hairy cell leukemia (HCL) is a rare indolent B-cell malignancy. In addition to characteristic morphology of HCL cells, the identification of the cellular surface markers and the expression of specific proteins by flow cytometry and immunohistochemistry are routine procedure in HCL diagnosis. Detection of BRAF V600E mutation plays key role in differential diagnosis of HCL which can be detected by several novel methods, such as immunohistochemistry, pyrosequencing, allele specific PCR or droplet digital PCR. Beside the BRAF mutation there can be other mechanisms causing constitutive activity in the signaling pathway and regulating the tumor cells such as growth factors, interleukins, adhesion proteins and micro-RNAs as well. Like in other malignancies, in order to clarify the pathomechanism, the genetic background of HCL is also actively investigated by next-generation sequencing. Frequent mutations were described in CDKN1B, KLF2 and KMT2C genes, moreover in other genes with lower incidence rate, as well. Genetically, and even in clinical manifestation and therapeutic response, significant differences can be found between patients with classical and variant HCL. While classical type has outstanding response for the first-line treatment with purine analogues, patients with variant HCL are often refractory to the treatment, and the BRAF inhibitors prove to be ineffective. Therefore, it is really important to distinguish these two entities. Several clinical studies are still in progress for the optimization and application of combining the currently applied therapeutic agents, furthermore other drugs that used in lymphoid malignancies are under investigation. New target molecules are also designed as novel therapeutic opportunity in HCL treatment.

Microfluidic Device Engineered to Study the Trafficking of Multiple Myeloma Cancer Cells Through the Sinusoidal Niche of Bone Marrow

Multiple myeloma (MM) is an incurable B cell malignancy characterized by the accumulation of monoclonal abnormal plasma cells in the bone marrow (BM). It has been a significant challenge to study the spatiotemporal interactions of MM cancer cells with the embedded microenvironments of BM. Here we report a microfluidic device which was designed to mimic several physiological features of the BM niche: (1) sinusoidal circulation, (2) sinusoidal endothelium, and (3) stroma. The endothelial and stromal compartments were constructed and used to demonstrate the device’s utility by spatiotemporally characterizing the CXCL12-mediated egression of MM cells from the BM stroma and its effects on the barrier function of endothelial cells (ECs). We found that the egression of MM cells resulted in less organized and loosely connected ECs, the widening of EC junction pores, and increased permeability through ECs, but without significantly affecting the number density of viable ECs. The results suggest that the device can be used to study the physical and secreted factors determining the trafficking of cancer cells through BM. The sinusoidal flow feature of the device provides an integral element for further creating systemic models of cancers that reside or metastasize to the BM niche.