Do reduced numbers of plasmacytoid dendritic cells contribute to the aggressive clinical course of COVID-19 in chronic lymphocytic leukaemia?

Infections with SARS-CoV-2 have been unduly severe in patients with haematological malignancies, in particular in those with chronic lymphocytic leukaemia (CLL). Based on a series of observations, we propose that an underlying mechanism for the aggressive clinical course of COVID-19 in CLL is a paucity of plasmacytoid dendritic cells (pDCs) in these patients. Indeed, pDCs express Toll-like receptor 7 (TLR7), which together with interferon-regulatory factor 7 (IRF7), enables pDCs to produce large amounts of type I interferons, essential for combating COVID-19. Treatment of CLL with Bruton's tyrosine kinase (BTK) inhibitors increased the number of pDCs, likely secondarily to the reduction in the tumour burden.publishedVersio

Ancestral SARS-CoV-2-specific T cells cross-recognize the Omicron variant

The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (B.1.1.529) variant of concern (VOC) has destabilized global efforts to control the impact of coronavirus disease 2019 (COVID-19). Recent data have suggested that B.1.1.529 can readily infect people with naturally acquired or vaccine-induced immunity, facilitated in some cases by viral escape from antibodies that neutralize ancestral SARS-CoV-2. However, severe disease appears to be relatively uncommon in such individuals, highlighting a potential role for other components of the adaptive immune system. We report here that SARS-CoV-2 spike-specific CD4+ and CD8+ T cells induced by prior infection or BNT162b2 vaccination provide extensive immune coverage against B.1.1.529. The median relative frequencies of SARS-CoV-2 spike-specific CD4+ T cells that cross-recognized B.1.1.529 in previously infected or BNT162b2-vaccinated individuals were 84% and 91%, respectively, and the corresponding median relative frequencies for SARS-CoV-2 spike-specific CD8+ T cells were 70% and 92%, respectively. Pairwise comparisons across groups further revealed that SARS-CoV-2 spike-reactive CD4+ and CD8+ T cells were functionally and phenotypically similar in response to the ancestral strain or B.1.1.529. Collectively, our data indicate that established SARS-CoV-2 spike-specific CD4+ and CD8+ T cell responses, especially after BNT162b2 vaccination, remain largely intact against B.1.1.529

Polycomb Target Genes Are Silenced in Multiple Myeloma

Multiple myeloma (MM) is a genetically heterogeneous disease, which to date remains fatal. Finding a common mechanism for initiation and progression of MM continues to be challenging. By means of integrative genomics, we identified an underexpressed gene signature in MM patient cells compared to normal counterpart plasma cells. This profile was enriched for previously defined H3K27-tri-methylated genes, targets of the Polycomb group (PcG) proteins in human embryonic fibroblasts. Additionally, the silenced gene signature was more pronounced in ISS stage III MM compared to stage I and II. Using chromatin immunoprecipitation (ChIP) assay on purified CD138+ cells from four MM patients and on two MM cell lines, we found enrichment of H3K27me3 at genes selected from the profile. As the data implied that the Polycomb-targeted gene profile would be highly relevant for pharmacological treatment of MM, we used two compounds to chemically revert the H3K27-tri-methylation mediated gene silencing. The S-adenosylhomocysteine hydrolase inhibitor 3-Deazaneplanocin (DZNep) and the histone deacetylase inhibitor LBH589 (Panobinostat), reactivated the expression of genes repressed by H3K27me3, depleted cells from the PRC2 component EZH2 and induced apoptosis in human MM cell lines. In the immunocompetent 5T33MM in vivo model for MM, treatment with LBH589 resulted in gene upregulation, reduced tumor load and increased overall survival. Taken together, our results reveal a common gene signature in MM, mediated by gene silencing via the Polycomb repressor complex. The importance of the underexpressed gene profile in MM tumor initiation and progression should be subjected to further studies

Anaemia and cancer : oral or intravenous iron ?

peer reviewedAnaemia and absolute or functional iron deficiency (ID) are common issues among cancer patients, with the prevalence of ID ranging from 32% to 60%. Most randomised clinical trials have shown superior efficacy of IV iron over oral or no iron supplementation in anaemic cancer patients receiving erythropoiesis-stimulating agents. Intravenous iron supplementation reduced blood transfusions, increased haemoglobin, and improved quality of life. At recommended doses, IV iron is well tolerated, and allergic reactions are exceedingly rare with modern formulations. Oral iron is often poorly tolerated and this can lead to compliance issues

New perspectives on complement mediated immunotherapy

Tumor-specific monoclonal antibodies (mAbs) offer several modes of tumor cell killing, from direct cytotoxic activity to indirect mechanisms employing the host immune system, particularly its innate branch. The latter effector functions seem to dominate among clinically approved anti-cancer mAbs and major efforts are being undertaken by both academia and the pharmaceutical industry with the aim to improve complement activation, antibody-dependent cellular cytotoxicity (ADCC) and Fc/opsonin-mediated phagocytosis. On one hand, there are a variety of available effector mechanisms to allow multistep elimination of tumor cells. On the other hand, tumor cells adopt a number of strategies to evade immune attack, such as overexpression of complement inhibitors, trogocytosis, shedding or internalization of mAb-targeted epitopes, which all contribute to their resistance against host defense mechanisms. Another problem recognized only recently is the depletion of immune effectors during the first round of treatment, which in concordance with delayed turnover of immune components renders subsequent rounds of therapy ineffective. Herein, we discuss newly identified limiting factors but also novel mechanistic data on complement activation by antitumor antibodies as issues important for guidance towards the next generations of immunotherapeutics

Antibodies reactive to cleaved sites in complement proteins enable highly specific measurement of soluble markers of complement activation.

An emerging number of diseases and therapeutic approaches with defined involvement of the complement system justify a need for specific markers reflecting activation of particular effector arms of the complement cascade. Measurement of such soluble markers in circulation is a challenge since the specificity of antibodies must be limited to activated complement fragments but not predominant and ubiquitous parental molecules. Existing assays for the measurement of soluble, activated complement proteins are based on the detection of conformational neoepitopes. We tested an alternative approach based on detection of short linear neoepitopes exposed at the cleavage sites after activation of the actual complement component. Obtained antibodies reactive to C4d and C5b fragments enabled us to set up highly specific sandwich ELISAs, which ensured trustful measurements without false positive readouts characteristic for some of the widely used assays