Phagocytosis-dependent activation of a TLR9-BTK-calcineurin-NFAT pathway co-ordinates innate immunity to Aspergillus fumigatus

Nocardiosis in a Patient with Nephrotic Syndrome Treated with Glucocorticoids and Tacrolimus

Nephrotic syndrome (NS) predisposes patients to immunocompromised hosts owing to the loss of immunoglobulins, immunosuppressant use, and edema complications. In addition, aging impairs the immune system; thus, elderly individuals with NS are vulnerable to infection. Nocardiosis is not a common disease; however, once infected, it can disseminate hematogenously, causing serious health problems. An 88-year-old woman with amyloid light chain amyloidosis-induced NS was treated with prednisolone and tacrolimus and developed nocardiosis and invasive aspergillosis. Protecting the skin and wounds from direct exposure to nocardia is important. Physicians should consider the safe dose and treatment period of immunosuppressants in elderly patients with NS.

Cytosolic nucleic acid sensing as driver of critical illness: mechanisms and advances in therapy

Nucleic acids from both self- and non-self-sources act as vital danger signals that trigger immune responses. Critical illnesses such as acute respiratory distress syndrome, sepsis, trauma and ischemia lead to the aberrant cytosolic accumulation and massive release of nucleic acids that are detected by antiviral innate immune receptors in the endosome or cytosol. Activation of receptors for deoxyribonucleic acids and ribonucleic acids triggers inflammation, a major contributor to morbidity and mortality in critically ill patients. In the past decade, there has been growing recognition of the therapeutic potential of targeting nucleic acid sensing in critical care. This review summarizes current knowledge of nucleic acid sensing in acute respiratory distress syndrome, sepsis, trauma and ischemia. Given the extensive research on nucleic acid sensing in common pathological conditions like cancer, autoimmune disorders, metabolic disorders and aging, we provide a comprehensive summary of nucleic acid sensing beyond critical illness to offer insights that may inform its role in critical conditions. Additionally, we discuss potential therapeutic strategies that specifically target nucleic acid sensing. By examining nucleic acid sources, sensor activation and function, as well as the impact of regulating these pathways across various acute diseases, we highlight the driving role of nucleic acid sensing in critical illness.

Interferon-gamma rescues dendritic cell calcineurin-dependent responses to Aspergillus fumigatus via Stat3 to Stat1 switching

Invasive pulmonary aspergillosis is a lethal opportunistic fungal infection in transplant recipients receiving calcineurin inhibitors. We previously identified a role for the calcineurin pathway in innate immune responses to A. fumigatus and have used exogenous interferon-gamma successfully to treat aspergillosis in this setting. Here we show that calcineurin inhibitors block dendritic cell maturation in response to A. fumigatus, impairing the Th1 polarization of CD4 cells. Interferon gamma, an immunotherapeutic option for invasive aspergillosis, restored maturation and promoted Th1 polarization via a dendritic cell dependent effect that was co-dependent on T cell interaction. We find that interferon gamma activates alternative transcriptional pathways to calcineurin-NFAT for the augmentation of pathogen handling. Histone modification ChIP-Seq analysis revealed dominant control by an interferon gamma induced regulatory switch from STAT3 to STAT1 transcription factor binding underpinning these observations. These findings provide key insight into the mechanisms of immunotherapy in organ transplant recipients with invasive fungal diseases.

NFATc1 in CD4+ T cells and CD11c+ dendritic cells drives TH2-mediated eosinophilic inflammation in allergic asthma

Background

Asthma, a chronic lung disease, is a significant public health problem worldwide. It is marked by increased TH2 response resulting in eosinophil accumulation. The pathophysiology of asthma involves various cell types, including epithelial cells, dendritic cells (DCs), innate lymphoid cells, B cells, and effector cells. Nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), a critical transcription factor for immune regulation, is known for its role in T cells and, more recently, in myeloid cells. However, the specific contributions of NFATc1 in T cells and DCs in the context of asthma are not well understood.

Objective

We explored NFATc1's role in T cells and DCs in modulating TH2 immune responses within the pathophysiology of allergic asthma.

Methods

We induced asthma in mice lacking Nfatc1 in CD4+ T cells or CD11c+ DCs using house dust mite, thereby enabling investigation into NFATc1's role in both cell types in experimental allergic asthma. Additionally, we examined NFATc1 expression in these cell types and its correlation with blood eosinophil levels in an adult asthma cohort.

Results

In a house dust mite-induced asthma model, we found that Nfatc1 deficiency either in CD4+ T cells or CD11c+ DCs resulted in reduced TH2-driven eosinophilic inflammation, IgE levels, and mast cell presence in the lung of asthmatic mice. Nfatc1's absence in CD4+ T cells directly hampered TH2 cell polarization and functionality, whereas in CD11c+ DCs, it affected DC differentiation and maturation, thereby weakening T-cell priming, proliferation, and subsequent TH2 differentiation. Correspondingly, translational research indicated significant correlations between CD4+NFATc1+ and CD11c+NFATc1+ cell populations and eosinophil levels in asthmatic patients, but not in healthy controls.

Conclusion

NFATc1 in T cells and DCs modulates TH2-mediated eosinophilic inflammation in allergic asthma, thus offering insight into asthma pathogenesis and identifying NFATc1 as a potential target for therapeutic intervention.

Increased NFAT and NFκB signalling contribute to the hyperinflammatory phenotype in response to Aspergillus fumigatus in a mouse model of cystic fibrosis

Aspergillus fumigatus (Af) is a major mould pathogen found ubiquitously in the air. It commonly infects the airways of people with cystic fibrosis (CF) leading to Aspergillus bronchitis or allergic bronchopulmonary aspergillosis. Resident alveolar macrophages and recruited neutrophils are important first lines of defence for clearance of Af in the lung. However, their contribution to the inflammatory phenotype in CF during Af infection is not well understood. Here, utilising CFTR deficient mice we describe a hyperinflammatory phenotype in both acute and allergic murine models of pulmonary aspergillosis. We show that during aspergillosis, CFTR deficiency leads to increased alveolar macrophage death and persistent inflammation of the airways in CF, accompanied by impaired fungal control. Utilising CFTR deficient murine cells and primary human CF cells we show that at a cellular level there is increased activation of NFκB and NFAT in response to Af which, as in in vivo models, is associated with increased cell death and reduced fungal control. Taken together, these studies indicate that CFTR deficiency promotes increased activation of inflammatory pathways, the induction of macrophage cell death and reduced fungal control contributing to the hyper-inflammatory of pulmonary aspergillosis phenotypes in CF.

Conditional requirement for dimerization of the membrane-binding module for BTK signaling in lymphocyte cell lines

Bruton's tyrosine kinase (BTK) is a major drug target in immune cells. The membrane-binding pleckstrin homology and tec homology (PH-TH) domains of BTK are required for signaling. Dimerization of the PH-TH module strongly stimulates the kinase activity of BTK in vitro. Here, we investigated whether BTK dimerizes in cells using the PH-TH module and whether this dimerization is necessary for signaling. To address this question, we developed high-throughput mutagenesis assays for BTK function in Ramos B cells and Jurkat T cells. We measured the fitness costs for thousands of point mutations in the PH-TH module and kinase domain to assess whether dimerization of the PH-TH module and BTK kinase activity were necessary for function. In Ramos cells, we found that neither PH-TH dimerization nor kinase activity was required for BTK signaling. Instead, in Ramos cells, BTK signaling was enhanced by PH-TH module mutations that increased membrane adsorption, even at the cost of reduced PH-TH dimerization. In contrast, in Jurkat cells, we found that BTK signaling depended on both PH-TH dimerization and kinase activity. Evolutionary analysis indicated that BTK proteins in organisms that evolved before the divergence of ray-finned fishes lacked PH-TH dimerization but had active kinase domains, similar to other Tec family kinases. Thus, PH-TH dimerization is a distinct feature of BTK that evolved to exert stricter regulatory control on kinase activity as adaptive immune systems gained increased complexity.

An IFN-STAT1-CYBB Axis Defines Protective Plasmacytoid DC to Neutrophil Crosstalk During Aspergillus fumigatus Infection

Aspergillus fumigatus is the most common cause of invasive aspergillosis (IA), a devastating infection in immunocompromised patients. Plasmacytoid dendritic cells (pDCs) regulate host defense against IA by enhancing neutrophil antifungal properties in the lung. Here, we define the pDC activation trajectory during A. fumigatus infection and the molecular events that underlie the protective pDC - neutrophil crosstalk. Fungus-induced pDC activation begins after bone marrow egress and results in pDC-dependent regulation of lung type I and type III IFN levels. These pDC-derived products act on type I and type III IFN receptor-expressing neutrophils and control neutrophil fungicidal activity and reactive oxygen species production via STAT1 signaling in a cell-intrinsic manner. Mechanistically, neutrophil STAT1 signaling regulates the transcription and expression of Cybb, which encodes one of five NADPH oxidase subunits. Thus, pDCs regulate neutrophil-dependent immunity against inhaled molds by controlling the local expression of a subunit required for NADPH oxidase assembly and activity in the lung.

Mycobacterial lipoarabinomannan negatively interferes with macrophage responses to Aspergillus fumigatus in-vitro

Introduction

Over 1 million people have chronic pulmonary aspergillosis (CPA) secondary to pulmonary tuberculosis. Additionally, Aspergillus fumigatus (Af) has been reported as one of the most common pathogens associated with mycobacteria in patients with cystic fibrosis. Mycobacterial virulence factors, like lipoarabinomannan, have been shown to interfere with host's intracellular pathways required for an effective immune response, however, the immunological basis for mycobacterial-fungal coinfection is still unknown. We therefore investigated the effect of lipoarabinomannan on macrophage responses against Af.

Methods

Bone marrow-derived macrophages (BMDMs) were stimulated with non-mannose-capped lipoarabinomannan (LAM) from Mycobacterium smegmatis or mannose-capped lipoarabinomannan (ManLAM) from Mycobacterium tuberculosis for 2 hours and then infected with swollen Af conidia. Cell death was assessed by lactate dehydrogenase release. Cytokine release was measured in supernatant using Enzyme Linked Immuno-Sorbent Assay (ELISA). Colony forming units counting and time-lapse fluorescence microscopy was performed for studying conidia killing by macrophages.

Results

BMDMs stimulated with LAM showed increased cell death and inflammatory cytokine release in a dose-dependent manner, characterised by a significant increase of IL-1β release. Time-lapse fluorescence microscopy and CFUs revealed that both LAM and ManLAM significantly decrease the capacity of macrophages to kill Af conidia within the first 6 hours of infection.

Conclusions

The mycobacterial virulence factor, lipoarabinomannan, disrupts macrophage capacity to efficiently clear Af at early stages of infection in-vitro.

Calcineurin inhibition enhances Caenorhabditis elegans lifespan by defecation defects-mediated calorie restriction and nuclear hormone signaling

Calcineurin is a highly conserved calcium/calmodulin-dependent serine/threonine protein phosphatase with diverse functions. Inhibition of calcineurin is known to enhance the lifespan of Caenorhabditis elegans through multiple signaling pathways. Aiming to study the role of calcineurin in regulating innate immunity, we discover that calcineurin is required for the rhythmic defecation motor program (DMP) in C. elegans. Calcineurin inhibition leads to defects in the DMP, resulting in intestinal bloating, rapid colonization of the gut by bacteria, and increased susceptibility to bacterial infection. We demonstrate that intestinal bloating caused by calcineurin inhibition mimics the effects of calorie restriction, resulting in enhanced lifespan. The TFEB ortholog, HLH-30, is required for lifespan extension mediated by calcineurin inhibition. Finally, we show that the nuclear hormone receptor, NHR-8, is upregulated by calcineurin inhibition and is necessary for the increased lifespan. Our studies uncover a role for calcineurin in the C. elegans DMP and provide a new mechanism for calcineurin inhibition-mediated longevity extension.

The Road Ahead: Advancing Antifungal Vaccines and Addressing Fungal Infections in the Post-COVID World

In impoverished nations, the COVID-19 pandemic has led to a widespread occurrence of deadly fungal diseases like mucormycosis. The limited availability of effective antifungal treatments and the emergence of drug-resistant fungal strains further exacerbate the situation. Factors such as systemic steroid use, intravenous drug misuse, and overutilization of broad-spectrum antimicrobials contribute to the prevalence of hospital-acquired infections caused by drug-resistant fungi. Fungal infections exploit compromised immune status and employ intricate mechanisms to evade immune surveillance. The immune response involves the innate and adaptive immune systems, leading to phagocytic and complement-mediated elimination of fungi. However, resistance to antifungals poses a challenge, highlighting the importance of antifungal prophylaxis and therapeutic vaccination. Understanding the host-fungal immunological interactions and developing vaccines are vital in combating fungal infections. Further research is needed to address the high mortality and morbidity associated with multidrug-resistant fungal pathogens and to develop innovative treatment drugs and vaccines. This review focuses on the global epidemiological burden of fungal infections, host-fungal immunological interactions, recent advancements in vaccine development and the road ahead.

Calcineurin-NFAT signaling controls neutrophils' ability of chemoattraction upon fungal infection

Calcineurin-nuclear factor of activated T cells (CN-NFAT) inhibitors are widely clinically used drugs for immunosuppression, but besides their required T cell response inhibition, they also undesirably affect innate immune cells. Disruption of innate immune cell function can explain the observed susceptibility of CN-NFAT inhibitor-treated patients to opportunistic fungal infections. Neutrophils play an essential role in innate immunity as a defense against pathogens; however, the effect of CN-NFAT inhibitors on neutrophil function was poorly described. Thus, we tested the response of human neutrophils to opportunistic fungal pathogens, namely Candida albicans and Aspergillus fumigatus, in the presence of CN-NFAT inhibitors. Here, we report that the NFAT pathway members were expressed in neutrophils and mediated part of the neutrophil response to pathogens. Upon pathogen exposure, neutrophils underwent profound transcriptomic changes with subsequent production of effector molecules. Importantly, genes and proteins involved in the regulation of the immune response and chemotaxis, including the chemokines CCL2, CCL3, and CCL4 were significantly upregulated. The presence of CN-NFAT inhibitors attenuated the expression of these chemokines and impaired the ability of neutrophils to chemoattract other immune cells. Our results amend knowledge about the impact of CN-NFAT inhibition in human neutrophils.

Manipulation of host phagocytosis by fungal pathogens and therapeutic opportunities

An important host defence mechanism against pathogens is intracellular killing, which is achieved through phagocytosis, a cellular process for engulfing and neutralizing extracellular particles. Phagocytosis results in the formation of matured phagolysosomes, which are specialized compartments that provide a hostile environment and are considered the end point of the degradative pathway. However, all fungal pathogens studied to date have developed strategies to manipulate phagosomal function directly and also indirectly by redirecting phagosomes from the degradative pathway to a non-degradative pathway with the expulsion and even transfer of pathogens between cells. Here, using the major human fungal pathogens Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans and Histoplasma capsulatum as examples, we discuss the processes involved in host phagosome-fungal pathogen interactions, with a focus on fungal evasion strategies. We also discuss recent approaches to targeting intraphagosomal pathogens, including the redirection of phagosomes towards degradative pathways for fungal pathogen eradication.

BTK inhibitor-induced defects in human neutrophil effector activity against Aspergillus fumigatus are restored by TNF-α

Inhibition of Bruton's tyrosine kinase (BTK) through covalent modifications of its active site (e.g., ibrutinib [IBT]) is a preferred treatment for multiple B cell malignancies. However, IBT-treated patients are more susceptible to invasive fungal infections, although the mechanism is poorly understood. Neutrophils are the primary line of defense against these infections; therefore, we examined the effect of IBT on primary human neutrophil effector activity against Aspergillus fumigatus. IBT significantly impaired the ability of neutrophils to kill A. fumigatus and potently inhibited reactive oxygen species (ROS) production, chemotaxis, and phagocytosis. Importantly, exogenous TNF-α fully compensated for defects imposed by IBT and newer-generation BTK inhibitors and restored the ability of neutrophils to contain A. fumigatus hyphal growth. Blocking TNF-α did not affect ROS production in healthy neutrophils but prevented exogenous TNF-α from rescuing the phenotype of IBT-treated neutrophils. The restorative capacity of TNF-α was independent of transcription. Moreover, the addition of TNF-α immediately rescued ROS production in IBT-treated neutrophils, indicating that TNF-α worked through a BTK-independent signaling pathway. Finally, TNF-α restored effector activity of primary neutrophils from patients on IBT therapy. Altogether, our data indicate that TNF-α rescued the antifungal immunity block imposed by inhibition of BTK in primary human neutrophils.

BTK drives neutrophil activation for sterilizing antifungal immunity

We describe a previously unappreciated role for Bruton's tyrosine kinase (BTK) in fungal immune surveillance against aspergillosis, an unforeseen complication of BTK inhibitors (BTKi) used for treating B cell lymphoid malignancies. We studied BTK-dependent fungal responses in neutrophils from diverse populations, including healthy donors, patients who were treated with BTKi, and X-linked agammaglobulinemia patients. Upon fungal exposure, BTK was activated in human neutrophils in a TLR2-, Dectin-1-, and FcγR-dependent manner, triggering the oxidative burst. BTK inhibition selectively impeded neutrophil-mediated damage to Aspergillus hyphae, primary granule release, and the fungus-induced oxidative burst by abrogating NADPH oxidase subunit p40phox and GTPase RAC2 activation. Moreover, neutrophil-specific Btk deletion in mice enhanced aspergillosis susceptibility by impairing neutrophil function, not recruitment or lifespan. Conversely, GM-CSF partially mitigated these deficits by enhancing p47phox activation. Our findings underline the crucial role of BTK signaling in neutrophils for antifungal immunity and provide a rationale for GM-CSF use to offset these deficits in patients who are susceptible.

Decoding Toll-like receptors: Recent insights and perspectives in innate immunity

Toll-like receptors (TLRs) are an evolutionarily conserved family in the innate immune system and are the first line of host defense against microbial pathogens by recognizing pathogen-associated molecular patterns (PAMPs). TLRs, categorized into cell surface and endosomal subfamilies, recognize diverse PAMPs, and structural elucidation of TLRs and PAMP complexes has revealed their intricate mechanisms. TLRs activate common and specific signaling pathways to shape immune responses. Recent studies have shown the importance of post-transcriptional regulation in TLR-mediated inflammatory responses. Despite their protective functions, aberrant responses of TLRs contribute to inflammatory and autoimmune disorders. Understanding the delicate balance between TLR activation and regulatory mechanisms is crucial for deciphering their dual role in immune defense and disease pathogenesis. This review provides an overview of recent insights into the history of TLR discovery, elucidation of TLR ligands and signaling pathways, and their relevance to various diseases.

Dephosphorylation of NFAT by Calcineurin inhibits Skp2-mediated degradation

The transcription factor NFAT plays key roles in multiple biological activities, such as immune responses, tissue development and malignant transformation. NFAT is dephosphorylated by calcineurin, which is activated by intracellular calcium levels, and translocated into the nucleus, resulting in transcriptional activation. Calcineurin dephosphorylates various target proteins and regulates their functions. However, the regulation of NFAT degradation is largely unknown, and it is unclear whether calcineurin contributes to the stability of NFAT. We investigated the effect of calcineurin inhibition on NFAT protein stability and found that the dephosphorylation of NFAT by calcineurin promotes the NFAT stabilization, whereas calcineurin mutant that is defective in phosphatase activity was unable to stabilize NFAT. Increased intracellular calcium ion concentration, which is essential for calcineurin activation, also induced NFAT stability. In addition, we identified S-phase kinase associated protein 2 (Skp2), an F-box protein of the SCF ubiquitin ligase complex, as a factor mediating degradation of NFAT when calcineurin was depleted. In summary, these findings revealed that the dephosphorylation of NFAT by calcineurin protects NFAT from degradation by Skp2 and promotes its protein stability.

Urinary tract infection following the use of BTK inhibitors: a real-world analysis of post-marketing surveillance data

BACKGROUND

Emerging case reports have raised awareness of urinary tract infection (UTI) which maybe a potentially serious complication. The present study aimed to summarize the clinical characteristics of patients with BTK inhibitor-related UTI, and the association between BTK inhibitors and UTI events was also assessed by disproportionality analysis.

RESEARCH DESIGN AND METHODS

We conducted an observational, retrospective, and pharmacovigilance study using data from the Food and Drug Administration Adverse Event Reporting System (FAERS) database. Data were retrieved from Quarter 1, 2004 to Quarter 2, 2022. The clinical characteristics of cases were summarized using descriptive statistics. We used the χ2 or Fisher exact methods for the analysis of categorical variables and the Mann-Whitney test or Student's t-text for the comparisons of continuous variables between fatal and non-fatal cases. A p-value less than 0.05 is considered to be statistically significant. Information component (IC) and reporting odds ratio (ROR) were used to evaluate the association.

RESULTS

BTK inhibitors were identified as the suspected drug causing UTI in 539 cases. The age of those cases concentrated on 60-89 years (87.83%, data available in 263/539). UTI signals were detected during BTK inhibitors treatment (IC 0.95[0.83-1.08], ROR 1.96[1.80-2.13]). The association between BTK inhibitors and UTI events was shown among all groups but not in the group of age<60 years old. There were no significant differences in age and gender between fatal and non-fatal cases. However, a significant difference in reporting regions was found (p = 0.016), with the highest percentage of reported deaths occurring in Europe (26.15%, p = 0.000).

CONCLUSIONS

Our study suggested a safety signal for UTI and BTK inhibitors compared to all other drugs in the database, especially in the elder (age ≥60). Further studies are needed to clarify these results.

Infectious complications among patients receiving ibrutinib for the treatment of hematological malignancies

PURPOSE

Ibrutinib is a Bruton's tyrosine kinase inhibitor used to treat multiple hematologic malignancies and graft-versus-host disease. Though less myelosuppressive than cytotoxic chemotherapy, increased infections, including invasive fungal infections (IFIs), have been reported with ibrutinib use. This study aimed to determine the characteristics and risk factors for infection associated with ibrutinib at our institution.

METHODS

Patients who received ibrutinib between June 2014 and August 2019 were included. Primary endpoints were the incidence of any infection and the incidence of serious infection (defined as hospitalization, parenteral antimicrobial therapy, or pneumonia regardless of hospitalization). Infection risk factors were assessed using logistic regression.

RESULTS

One hundred thirty-two patients were identified (78% male; median age, 71 years). The most common indications for ibrutinib were chronic lymphocytic leukemia (67%) and mantle cell lymphoma (12%). Infection and serious infection occurred in 94 (71%) and 47 (36%) patients, respectively; when pneumonia was excluded as a criterion for serious infection, the serious infection rate was 27%. The median time from ibrutinib initiation to first infection was 125 days. Prior allogeneic hematopoietic stem cell transplantation (allo-HSCT) (odds ratio [OR], 4.60; 95% CI, 1.22-17.4) and corticosteroid use (OR, 5.55; 95% CI, 1.52-20.3) were significant risk factors for serious infection. IFIs were diagnosed in 7 patients (5%): 5 had Pneumocystis jirovecii pneumonia and 2 were infected with invasive molds.

CONCLUSION

Serious infection and IFI rates are high but similar to those previously described. Risk factors for serious infection included allo-HSCT and corticosteroid use. Targeted antimicrobial prophylaxis should be evaluated in prospective studies in patients on ibrutinib to reduce serious infections and IFI.

Severe infections requiring intensive care unit admission in patients receiving ibrutinib for hematological malignancies: a groupe de recherche respiratoire en réanimation onco-hématologique (GRRR-OH) study

BACKGROUND

In the last decade, Ibrutinib has become the standard of care in the treatment of several lymphoproliferative diseases such as chronic lymphocytic leukemia (CLL) and several non-Hodgkin lymphoma. Beyond Bruton tyrosine kinase inhibition, Ibrutinib shows broad immunomodulatory effects that may promote the occurrence of infectious complications, including opportunistic infections. The infectious burden has been shown to vary by disease status, neutropenia, and prior therapy but data focusing on severe infections requiring intensive care unit (ICU) admission remain scarce. We sought to investigate features and outcomes of severe infections in a multicenter cohort of 69 patients receiving ibrutinib admitted to 10 French intensive care units (ICU) from 1 January 2015 to 31 December 2020.

RESULTS

Median time from ibrutinib initiation was 6.6 [3-18] months. Invasive fungal infections (IFI) accounted for 19% (n = 13/69) of severe infections, including 9 (69%; n = 9/13) invasive aspergillosis, 3 (23%; n = 3/13) Pneumocystis pneumonia, and 1 (8%; n = 1/13) cryptococcosis. Most common organ injury was acute respiratory failure (ARF) (71%; n = 49/69) and 41% (n = 28/69) of patients required mechanical ventilation. Twenty (29%; n = 20/69) patients died in the ICU while day-90 mortality reached 55% (n = 35/64). In comparison with survivors, decedents displayed more severe organ dysfunctions (SOFA 7 [5-11] vs. 4 [3-7], p = 0.004) and were more likely to undergo mechanical ventilation (68% vs. 31%, p = 0.010). Sixty-three ibrutinib-treated patients were matched based on age and underlying malignancy with 63 controls receiving conventional chemotherapy from an historic cohort. Despite a higher median number of prior chemotherapy lines (2 [1-2] vs. 0 [0-2]; p < 0.001) and higher rates of fungal [21% vs. 8%, p = 0.001] and viral [17% vs. 5%, p = 0.027] infections in patients receiving ibrutinib, ICU (27% vs. 38%, p = 0.254) and day-90 mortality (52% vs. 48%, p = 0.785) were similar between the two groups.

CONCLUSION

In ibrutinib-treated patients, severe infections requiring ICU admission were associated with a dismal prognosis, mostly impacted by initial organ failures. Opportunistic agents should be systematically screened by ICU clinicians in this immunocompromised population.

Discovery of Ibrutinib-based BTK PROTACs with in vivo anti-inflammatory efficacy by inhibiting NF-κB activation

As a critical upstream regulator of nuclear factor-κB (NF-κB) activation, Bruton's tyrosine kinase (BTK) has been identified to be an effective therapeutic target for the treatment of acute or chronic inflammatory diseases. Herein, we describe the design, synthesis and structure-activity-relationship analysis of a novel series of Ibrutinib-based BTK PROTACs by recruiting Cereblon (CRBN) ligase. Among them, compound 15 was identified as the most potent degrader with a DC50 of 3.18 nM, significantly better than the positive control MT802 (DC50 of 63.31 nM). Compound 15 could also degrade BTK protein in Lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and suppress the mRNA expression and secretion of proinflammatory cytokines such as IL-1β and IL-6 by inhibiting NF-κB activation. Furthermore, compound 15 reduced inflammatory responses in a mouse zymosan-induced peritonitis (ZIP) model. Our findings demonstrated for the first time that targeting BTK degradation by PROTACs might be an alternative option for the treatment of inflammatory disorders, and compound 15 represents one of the most efficient BTK PROTACs (DC50 = 3.18 nM; Dmax = 99.90%; near 100% degradation at 8 h) reported so far and could serve as a lead compound for further investigation as an anti-inflammatory agent.

Immune responses to human fungal pathogens and therapeutic prospects

Pathogenic fungi have emerged as significant causes of infectious morbidity and death in patients with acquired immunodeficiency conditions such as HIV/AIDS and following receipt of chemotherapy, immunosuppressive agents or targeted biologics for neoplastic or autoimmune diseases, or transplants for end organ failure. Furthermore, in recent years, the spread of multidrug-resistant Candida auris has caused life-threatening outbreaks in health-care facilities worldwide and raised serious concerns for global public health. Rapid progress in the discovery and functional characterization of inborn errors of immunity that predispose to fungal disease and the development of clinically relevant animal models have enhanced our understanding of fungal recognition and effector pathways and adaptive immune responses. In this Review, we synthesize our current understanding of the cellular and molecular determinants of mammalian antifungal immunity, focusing on observations that show promise for informing risk stratification, prognosis, prophylaxis and therapies to combat life-threatening fungal infections in vulnerable patient populations.

Primary biliary cholangitis: molecular pathogenesis perspectives and therapeutic potential of natural products

Primary biliary cirrhosis (PBC) is a chronic cholestatic immune liver disease characterized by persistent cholestasis, interlobular bile duct damage, portal inflammation, liver fibrosis, eventual cirrhosis, and death. Existing clinical and animal studies have made a good progress in bile acid metabolism, intestinal flora disorder inflammatory response, bile duct cell damage, and autoimmune response mechanisms. However, the pathogenesis of PBC has not been clearly elucidated. We focus on the pathological mechanism and new drug research and development of PBC in clinical and laboratory in the recent 20 years, to discuss the latest understanding of the pathological mechanism, treatment options, and drug discovery of PBC. Current clinical treatment mode and symptomatic drug support obviously cannot meet the urgent demand of patients with PBC, especially for the patients who do not respond to the current treatment drugs. New treatment methods are urgently needed. Drug candidates targeting reported targets or signals of PBC are emerging, albeit with some success and some failure. Single-target drugs cannot achieve ideal clinical efficacy. Multitarget drugs are the trend of future research and development of PBC drugs.

Exploiting antifungal immunity in the clinical context

The continuous expansion of immunocompromised patient populations at-risk for developing life-threatening opportunistic fungal infections in recent decades has helped develop a deeper understanding of antifungal host defenses, which has provided the foundation for eventually devising immune-based targeted interventions in the clinic. This review outlines how genetic variation in certain immune pathway-related genes may contribute to the observed clinical variability in the risk of acquisition and/or severity of fungal infections and how immunogenetic-based patient stratification may enable the eventual development of personalized strategies for antifungal prophylaxis and/or vaccination. Moreover, this review synthesizes the emerging cytokine-based, cell-based, and other immunotherapeutic strategies that have shown promise as adjunctive therapies for boosting or modulating tissue-specific antifungal immune responses in the context of opportunistic fungal infections.

Invasive aspergillosis in liver transplant recipients

BACKGROUND

Liver transplantation is increasing worldwide with underlying pathologies dominated by metabolic and alcoholic diseases in developed countries.

METHODS

We provide a narrative review of invasive aspergillosis (IA) in liver transplant (LT) recipients. We searched PubMed and Google Scholar for references without language and time restrictions.

RESULTS

The incidence of IA in LT recipients is low (1.8%), while mortality is high (∼50%). It occurs mainly early (<3 months) after LT. Some risk factors have been identified before (corticosteroid, renal, and liver failure), during (massive transfusion and duration of surgical procedure), and after transplantation (intensive care unit stay, re-transplantation, re-operation). Diagnosis can be difficult and therefore requires full radiological and clinicobiological collaboration. Accurate identification of Aspergillus species is recommended due to the cryptic species, and susceptibility testing is crucial given the increasing resistance of Aspergillus fumigatus to azoles. It is recommended to reduce the dose of tacrolimus (50%) and to closely monitor the trough level when introducing voriconazole, isavuconazole, and posaconazole. Surgery should be discussed on a case-by-case basis. Antifungal prophylaxis is recommended in high-risk patients. Environmental preventative measures should be implemented to prevent outbreaks of nosocomial aspergillosis in LT recipient units.

CONCLUSION

IA remains a very serious disease in LT patients and should be promptly sought and, if possible, prevented by clinicians when risk factors are identified.

Honokiol reduces fungal burden and ameliorate inflammation lesions of Aspergillus fumigatus keratitis via Dectin-2 down-regulation

PURPOSE

To screen and identify the mechanism of honokiol on anti-fungi and anti-inflammation in fungal keratitis (FK) through bioinformatic analysis and biological experiments.

METHODS

Transcriptome profile demonstrated differential expression genes (DEGs) of Aspergillus fumigatus keratitis between PBS-treated and honokiol-treated groups via bioinformatics analyses. Inflammatory substances were quantified by qRT-PCR, Western blot and ELISA, and macrophage polarization was examined by flow cytometry. Periodic acid Schiff staining and morphological interference assay were used to detect hyphal distribution in vivo and fungal germination in vitro, respectively. Electron microscopy was to illustrate hyphal microstructure.

RESULTS

Illumina sequencing demonstrated that compared with the honokiol group, 1175 up-regulated and 383 down-regulated genes were induced in C57BL/6 mice Aspergillus fumigatus keratitis with PBS treatment. Through GO analysis, some differential expression proteins (DEPs) played major roles in biological processes, especially fungal defense and immune activation. KEGG analysis provided fungus-related signaling pathways. PPI analysis demonstrated that DEPs from multiple pathways form a close-knit network, providing a broader context for FK treatment. In biological experiments, Dectin-2, NLRP3 and IL-1β were upregulated by Aspergillus fumigatus to evaluate immune response. Honokiol could reverse the trend, comparable to Dectin-2 siRNA interference. Meanwhile, honokiol could also play an anti-inflammatory role via promoting M2 phenotype polarization. Moreover, honokiol reduced hyphal distribution in the stroma, delayed germination, and destroyed the hyphal cell membrane in-vitro.

CONCLUSIONS

Honokiol possesses anti-fungal and anti-inflammatory effects in Aspergillus fumigatus keratitis and may develop a potential and safe therapeutic modality for FK.

Fungal melanin-induced metabolic reprogramming in macrophages is crucial for inflammation

The overuse of antifungal and immunosuppressant drugs and the higher frequency of organ transplantation has resulted in mycosis being increasingly intractable, and there is a great need for the development of new therapies. Melanin is an important virulence factor that can inhibit the inflammatory response in the host and facilitate fungal survival by several methods. However, a recent study showed that the Akt/mTOR/HIF1α axis in macrophages was activated after melanin-binding proteins recognised the DHN melanin of Aspergillus fumigatus, with a resulting metabolic shift towards glycolysis (i.e., metabolic reprogramming). As a result, antimicrobial compounds (e.g., inflammatory mediators and reactive oxygen species) were increased to fight the fungal invasion. Actually, DHN melanin from other fungi and DOPA melanin can induce inflammation and stimulate the production of melanin-binding antibodies. In addition, DOPA melanin contains conserved repeating units that are similar to those of DHN melanin. Therefore, we evaluated the associated evidence to propose an interesting and reasonable hypothesis that melanin promotes inflammation by metabolic reprogramming, which could provide a research direction for antifungal therapy. It suggests that regulating the metabolism of immune cells can guide the inflammatory response against fungi, despite the presence of immunosuppressant melanin. Since the biochemical molecules of glycolysis are clearly described, regulating glycolysis in macrophages may be easier than inventing new antifungal drugs. Further clarification of our hypothesis may strengthen the candidacy of melanin for future antifungal vaccines.

Stimulating the autophagic-lysosomal axis enhances host defense against fungal infection in a zebrafish model of invasive Aspergillosis

The increasing prevalence of antifungal-resistant human pathogenic fungi, particularly azole-resistant Aspergillus fumigatus, is a life-threatening challenge to the immunocompromised population. Autophagy-related processes such as LC3-associated phagocytosis have been shown to be activated in the host response against fungal infection, but their overall effect on host resistance remains uncertain. To analyze the relevance of these processes in vivo, we used a zebrafish animal model of invasive Aspergillosis. To confirm the validity of this model to test potential treatments for this disease, we confirmed that immunosuppressive treatments or neutropenia rendered zebrafish embryos more susceptible to A. fumigatus. We used GFP-Lc3 transgenic zebrafish to visualize the autophagy-related processes in innate immune phagocytes shortly after phagocytosis of A. fumigatus conidia, and found that both wild-type and melanin-deficient conidia elicited Lc3 recruitment. In macrophages, we observed GFP-Lc3 accumulation in puncta after phagocytosis, as well as short, rapid events of GFP-Lc3 decoration of single and multiple conidia-containing vesicles, while neutrophils covered single conidia-containing vesicles with bright and long-lasting GFP-Lc3 signal. Next, using genetic and pharmacological stimulation of three independent autophagy-inducing pathways, we showed that the antifungal autophagy response improves the host survival against A. fumigatus infection, but only in the presence of phagocytes. Therefore, we provide proof-of-concept that stimulating the (auto)phagolysosomal pathways is a promising approach to develop host-directed therapies against invasive Aspergillosis, and should be explored further either as adjunctive or stand-alone therapy for drug-resistant Aspergillus infections.Abbreviations: DMSO: dimethyl sulfoxide; HR: hazard ratio; HDT: host-directed therapy; Hpf: hours post fertilization; IA: invasive Aspergillosis; LAP: LC3-associated phagocytosis; MTZ: metronidazole; PTU: N-phenylthiourea; ROS: reactive oxygen species.

Postinfluenza Environment Reduces Aspergillus fumigatus Conidium Clearance and Facilitates Invasive Aspergillosis In Vivo

Aspergillus fumigatus is a human fungal pathogen that is most often avirulent in immunecompetent individuals because the innate immune system is efficient at eliminating fungal conidia. However, recent clinical observations have shown that severe influenza A virus (IAV) infection can lead to secondary A. fumigatus infections with high mortality. Little is currently known about how IAV infection alters the innate antifungal immune response. Here, we established a murine model of IAV-induced A. fumigatus (IAV-Af) superinfection by inoculating mice with IAV followed 6 days later by A. fumigatus conidia challenge. We observed increased mortality in the IAV-Af-superinfected mice compared to mice challenged with either IAV or A. fumigatus alone. A. fumigatus conidia were able to germinate and establish a biofilm in the lungs of the IAV-Af superinfection group, which was not seen following fungal challenge alone. While we did not observe any differences in inflammatory cell recruitment in the IAV-Af superinfection group compared to single-infection controls, we observed defects in Aspergillus conidial uptake and killing by both neutrophils and monocytes after IAV infection. pHrodo Green zymosan bioparticle (pHrodo-zymosan) and CM-H2DCFDA [5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate] staining, indicators of phagolysosome maturation and reactive oxygen species (ROS) production, respectively, revealed that the fungal killing defect was due in part to reduced phagolysosome maturation. Collectively, our data demonstrate that the ability of neutrophils and monocytes to kill and clear Aspergillus conidia is strongly reduced in the pulmonary environment of an IAV-infected lung, which leads to invasive pulmonary aspergillosis and increased overall mortality in our mouse model, recapitulating what is observed clinically in humans. IMPORTANCE Influenza A virus (IAV) is a common respiratory virus that causes seasonal illness in humans, but can cause pandemics and severe infection in certain patients. Since the emergence of the 2009 H1N1 pandemic strains, there has been an increase in clinical reports of IAV-infected patients in the intensive care unit (ICU) developing secondary pulmonary aspergillosis. These cases of flu-Aspergillus superinfections are associated with worse clinical outcomes than secondary bacterial infections in the setting of IAV. To date, we have a limited understanding of the cause(s) of secondary fungal infections in immunocompetent hosts. IAV-induced modulation of cytokine production and innate immune cellular function generates a unique immune environment in the lung, which could make the host vulnerable to a secondary fungal infection. Our work shows that defects in phagolysosome maturation in neutrophils and monocytes after IAV infection impair the ability of these cells to kill A. fumigatus, thus leading to increased fungal germination and growth and subsequent invasive aspergillosis. Our work lays a foundation for future mechanistic studies examining the exact immune modulatory events occurring in the respiratory tract after viral infection leading to secondary fungal infections.

The Therapeutic Effect of Tacrolimus in a Mouse Psoriatic Model is Associated with the Induction of Myeloid-derived Suppressor Cells

Objectives

Topical administration of Tacrolimus (TAC) is efective in the treatment of psoriasis in human patients and in mouse models. Previously, we showed that, though promoting the proliferative expansion of CD4⁺Foxp3⁺ regulatory T cells (Tregs), TNFR2 was protective in mouse psoriasis model. We thus examined the role of TNFR2 signal in the efect of TAC in the treatment of mouse psoriasis.

Methods

To this end, psoriasis was induced in WT, or TNFR1 KO, or TNFR2 KO mice, and the psoriatic mice were treated with or without IMQ.

Results

The results showed that TAC treatment potently inhibited the development of psoriasis in WT and TNFR1 KO mice, but not in TNFR2 KO mice. However, the treatment of TAC failed to induce the expansion of Tregs in psoriatic mice. In addition to playing a decisive role in the activation of Tregs, TNFR2 stimulates the generation and activation of myeloid-derived suppressor cells (MDSCs). This led us to found that the topical treatment with TAC markedly increased the number of MDSCs in the spleen of WT and TNFR1 KO mice, but not in TNFR2 KO mice. Consequently, TAC potently decreased serum levels of IL-17A, INF-γ, and TNF and their mRNA levels in the inflamed skin lesion.

Conclusion

Therefore, our study for the first time found that the therapeutic efect of TAC in psoriasis is associated with the expansion of MDSCs in a TNFR2-dependent manner.

Potential Antifungal Targets for Aspergillus sp. from the Calcineurin and Heat Shock Protein Pathways

Aspergillus species, especially A. fumigatus, and to a lesser extent others (A. flavus, A. niger, A. terreus), although rarely pathogenic to healthy humans, can be very aggressive to immunocompromised patients (they are opportunistic pathogens). Although survival rates for such infections have improved in recent decades following the introduction of azole derivatives, they remain a clinical challenge. The fact that current antifungals act as fungistatic rather than fungicide, that they have limited safety, and that resistance is becoming increasingly common make the need for new, more effective, and safer therapies to become more acute. Over the last decades, knowledge about the molecular biology of A. fumigatus and other Aspergillus species, and particularly of calcineurin, Hsp90, and their signaling pathway proteins, has progressed remarkably. Although calcineurin has attracted much interest, its adverse effects, particularly its immunosuppressive effects, make it less attractive than it might at first appear. The situation is not very different for Hsp90. Other proteins from their signaling pathways, such as protein kinases phosphorylating the four SPRR serine residues, CrzA, rcnA, pmcA-pmcC (particularly pmcC), rfeF, BAR adapter protein(s), the phkB histidine kinase, sskB MAP kinase kinase, zfpA, htfA, ctfA, SwoH (nucleoside diphosphate kinase), CchA, MidA, FKBP12, the K27 lysine position from Hsp90, PkcA, MpkA, RlmA, brlA, abaA, wetA, other heat shock proteins (Hsp70, Hsp40, Hsp12) currently appear promising and deserve further investigation as potential targets for antifungal drug development.

BTK inhibitors in the treatment of hematological malignancies and inflammatory diseases: mechanisms and clinical studies

Bruton's tyrosine kinase (BTK) is an essential component of multiple signaling pathways that regulate B cell and myeloid cell proliferation, survival, and functions, making it a promising therapeutic target for various B cell malignancies and inflammatory diseases. Five small molecule inhibitors have shown remarkable efficacy and have been approved to treat different types of hematological cancers, including ibrutinib, acalabrutinib, zanubrutinib, tirabrutinib, and orelabrutinib. The first-in-class agent, ibrutinib, has created a new era of chemotherapy-free treatment of B cell malignancies. Ibrutinib is so popular and became the fourth top-selling cancer drug worldwide in 2021. To reduce the off-target effects and overcome the acquired resistance of ibrutinib, significant efforts have been made in developing highly selective second- and third-generation BTK inhibitors and various combination approaches. Over the past few years, BTK inhibitors have also been repurposed for the treatment of inflammatory diseases. Promising data have been obtained from preclinical and early-phase clinical studies. In this review, we summarized current progress in applying BTK inhibitors in the treatment of hematological malignancies and inflammatory disorders, highlighting available results from clinical studies.

Pulmonary Fibrosis and Hypereosinophilia in TLR9-/- Mice Infected by Cryptococcus gattii

Cryptococcus gattii is a worldwide-distributed basidiomycetous yeast that can infect immunocompetent hosts. However, little is known about the mechanisms involved in the disease. The innate immune response is essential to the control of infections by microorganisms. Toll-like receptor 9 (TLR9) is an innate immune receptor, classically described as a non-methylated DNA recognizer and associated with bacteria, protozoa and opportunistic mycosis infection models. Previously, our group showed that TLR9^-/- mice were more susceptible to C. gattii after 21 days of infection. However, some questions about the innate immunity involving TLR9 response against C. gattii remain unknown. In order to investigate the systemic cryptococcal infection, we evaluated C57BL/6 mice and C57BL/6 TLR9^-/- after intratracheal infection with 10⁴C. gattii yeasts for 21 days. Our data evidenced that TLR9^-/- was more susceptible to C. gattii. TLR9^-/- mice had hypereosinophilia in pulmonary mixed cellular infiltrate, severe bronchiolitis and vasculitis and type 2 alveolar cell hyperplasia. In addition, TLR9^-/- mice developed severe pulmonary fibrosis and areas with strongly birefringent fibers. Together, our results corroborate the hypothesis that TLR9 is important to support the Th1/Th17 response against C. gattii infection in the murine experimental model.

Specific immunosuppressive role of nanodrugs targeting calcineurin in innate myeloid cells

Calcineurin (CN) inhibitors currently used to avoid transplant rejection block the activation of adaptive immune responses but also prevent the development of tolerance toward the graft, by directly inhibiting T cells. CN, through the transcription factors of the NFAT family, plays an important role also in the differentiation dendritic cells (DCs), the main cells responsible for the activation of T lymphocytes. Therefore, we hypothesized that the inhibition of CN only in DCs and not in T cells could be sufficient to prevent T cell responses, while allowing for the development of tolerance. Here, we show that inhibition of CN/NFAT pathway in innate myeloid cells, using a new nanoconjugate capable of selectively targeting phagocytes in vivo, protects against graft rejection and induces a longer graft acceptance compared to common CN inhibitors. We propose a new generation of nanoparticles-based selective immune suppressive agents for a better control of transplant acceptance.

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Calcineurin/NFATc2 pathway is required to enable DC migration to draining lymph nodes

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Calcineurin/NFATc2 pathway in DCs is required for type I immune responses activation

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Superparamagnetic iron oxide NPs can be used to efficiently target phagocytes in vivo

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Specific delivery of calcineurin inhibitor by NPs to phagocytes induce graft acceptance

BTK Inhibitors Impair Platelet-Mediated Antifungal Activity

In recent years, the introduction of new drugs targeting Bruton’s tyrosine kinase (BTK) has allowed dramatic improvement in the prognosis of patients with chronic lymphocytic leukemia (CLL) and other B-cell neoplasms. Although these small molecules were initially considered less immunosuppressive than chemoimmunotherapy, an increasing number of reports have described the occurrence of unexpected opportunistic fungal infections, in particular invasive aspergillosis (IA). BTK represents a crucial molecule in several signaling pathways depending on different immune receptors. Based on a variety of specific off-target effects on innate immunity, namely on neutrophils, monocytes, pulmonary macrophages, and nurse-like cells, ibrutinib has been proposed as a new host factor for the definition of probable invasive pulmonary mold disease. The role of platelets in the control of fungal growth, through granule-dependent mechanisms, was described in vitro almost two decades ago and is, so far, neglected by experts in the field of clinical management of IA. In the present study, we confirm the antifungal role of platelets, and we show, for the first time, that the exposure to BTK inhibitors impairs several immune functions of platelets in response to Aspergillus fumigatus, i.e., the ability to adhere to conidia, activation (as indicated by reduced expression of P-selectin), and direct killing activity. In conclusion, our experimental data suggest that antiplatelet effects of BTK inhibitors may contribute to an increased risk for IA in CLL patients.

Ibrutinib in Refractory or Relapsing Primary Central Nervous System Lymphoma: A Systematic Review

Primary Central Nervous System Lymphoma (PCNSL) is a rare variant of Non-Hodgkin Lymphoma (NHL) representing 1–2% of all NHL cases. PCNSL is defined as a lymphoma that occurs in the brain, spinal cord, leptomeninges, or eyes. Efforts to treat PCNSL by traditional chemotherapy and radiotherapy have generally been unsuccessful as a significant proportion of patients have frequent relapses or are refractory to treatment. The prognosis of patients with Refractory or Relapsed (R/R) PCNSL is abysmal. The optimal treatment for R/R PCNSL is poorly defined as there are only a limited number of studies in this setting. Several studies have recently shown that ibrutinib, a Bruton tyrosine kinase (BTK) inhibitor, has promising results in the treatment of R/R PCNSL. However, these are preliminary studies with a limited sample size. In this systematic review, we explored and critically appraised the evidence about the efficacy of the novel agent ibrutinib in treating R/R PCNSL.

Invasive Fungal Infections and Targeted Therapies in Hematological Malignancies

The use of targeted biologic therapies for hematological malignancies has greatly expanded in recent years. These agents act upon specific molecular pathways in order to target malignant cells but frequently have broader effects involving both innate and adaptive immunity. Patients with hematological malignancies have unique risk factors for infection, including immune dysregulation related to their underlying disease and sequelae of prior treatment regimens. Determining the individual risk of infection related to any novel agent is challenging in this setting. Invasive fungal infections (IFIs) represent one of the most morbid infectious complications observed in hematological malignancy. In recent years, growing evidence suggests that certain small molecule inhibitors, such as BTK inhibitors and PI3K inhibitors, may cause an increased risk of IFI in certain patients. It is imperative to better understand the impact that novel targeted therapies might have on the development of IFIs in this high-risk patient population.

The role of Bruton's tyrosine kinase in the immune system and disease

Bruton's tyrosine kinase (BTK) is a TEC kinase with a multifaceted role in B-cell biology and function, highlighted by its position as a critical component of the B-cell receptor signalling pathway. Due to its role as a therapeutic target in several haematological malignancies including chronic lymphocytic leukaemia, BTK has been gaining tremendous momentum in recent years. Within the immune system, BTK plays a part in numerous pathways and cells beyond B cells (i.e. T cells, macrophages). Not surprisingly, BTK has been elucidated to be a driving factor not only in lymphoproliferative disorders but also in autoimmune diseases and response to infection. To extort this role, BTK inhibitors such as ibrutinib have been developed to target BTK in other diseases. However, due to rising levels of resistance, the urgency to develop new inhibitors with alternative modes of targeting BTK is high. To meet this demand, an expanding list of BTK inhibitors is currently being trialled. In this review, we synopsize recent discoveries regarding BTK and its role within different immune cells and pathways. Additionally, we discuss the broad significance and relevance of BTK for various diseases ranging from haematology and rheumatology to the COVID-19 pandemic. Overall, BTK signalling and its targetable nature have emerged as immensely important for a wide range of clinical applications. The development of novel, more specific and less toxic BTK inhibitors could be revolutionary for a significant number of diseases with yet unmet treatment needs.

Immunosuppression Affects Neutrophil Functions: Does Calcineurin-NFAT Signaling Matter?

Neutrophils are innate immune cells with important roles in antimicrobial defense. However, impaired or dysregulated neutrophil function can result in host tissue damage, loss of homeostasis, hyperinflammation or pathological immunosuppression. A central link between neutrophil activation and immune outcomes is emerging to be the calcineurin-nuclear factor of activated T cells (NFAT) signaling pathway, which is activated by neutrophil detection of a microbial threat via pattern recognition receptors and results in inflammatory cytokine production. This potent pro-inflammatory pathway is also the target of several immunosuppressive drugs used for the treatment of autoimmune disorders, during solid organ and hematopoietic cell transplantations, and as a part of anti-cancer therapy: but what effects these drugs have on neutrophil function, and their broader consequences for immune homeostasis and microbial defense are not yet known. Here, we bring together the emerging literature describing pathology- and drug- induced neutrophil impairment, with particular focus on their effects on calcineurin-NFAT signaling in the innate immune compartment.

In cellulo synthesis of dendrimeric sensors for fluorescence-on imaging of bacterial phagocytosis

Methods for optical tracking of pathogen-host interactions are of biomedical significance. We herein have reported a high molecular weight pH sensor (Den-pH) that is assembled in bacteria and then stably trapped in bacteria irrespective of bacterial membrane potentials. Endowed with acidity-triggered red fluorescence, Den-pH allows signal-on tracking of S. aureus in phagocytosis by macrophages. Intra-bacterial formation of multifunctional optical probes, which offers the advantage of overcoming the liability of conventional potential-sensitive dyes to dissipate from stressed bacteria, offers a new tool to study stressed pathogens.

Phagosome maturation in macrophages: Eat, digest, adapt, and repeat

Phagocytosis is a dynamic process that requires an intricate interplay between phagocytic receptors, membrane lipids, and numerous signalling proteins and their effectors, to coordinate the engulfment of a bound particle. These particles are diverse in their physico-chemical properties such as size and shape and include bacteria, fungi, apoptotic cells, living tumour cells, and abiotic particles. Once engulfed, these particles are enclosed within a phagosome, which undergoes a striking transformation referred to as phagosome maturation, which will ultimately lead to the processing and degradation of the enclosed particulate. In this review, we focus on recent advancements in phagosome maturation in macrophages, highlighting new discoveries and emerging themes. Such advancements include identification of new GTPases and their effectors and the intricate spatio-temporal dynamics of phosphoinositides in governing phagosome maturation. We then explore phagosome fission and recycling, the emerging role of membrane contact sites, and delve into mechanisms of phagosome resolution to recycle and reform lysosomes. We further illustrate how phagosome maturation is context-dependent, subject to the type of particle, phagocytic receptors, the phagocytes and their state of activation during phagocytosis. Lastly, we discuss how phagosomes serve as signalling platforms to help phagocytes adapt to their environmental conditions. Overall, this review aims to cover recent findings, identify emerging themes, and highlight current challenges and directions to improve our understanding of phagosome maturation in macrophages.

Cerebral aspergillosis and facial acneiform lesions following initiation of ibrutinib in a patient with chronic lymphocytic leukemia

A case of a 67-year-old male with CLL, presented with prolonged pancytopenia after his first cycle of fludarabine, cyclophosphamide, and rituximab (FCR) chemotherapy. He was then treated with ibrutinib oral monotherapy. Shortly after ibrutinib treatment initiation, he developed a brain abscess and pulmonary disease as a part of an invasive aspergillosis. The patient improved after brain abscess drainage and the anti-fungal therapy voriconazole. Upon resuming ibrutinib four months after his hospitalization, he developed extensive acneiform facial lesions. This case is the first to report on the development of two separate complications in one patient related to ibrutinib, namely, Aspergillus infection, and severe acneiform skin lesions.

Experimental Models of Infectious Pulmonary Complications Following Hematopoietic Cell Transplantation

Pulmonary infections remain a major cause of morbidity and mortality in hematopoietic cell transplantation (HCT) recipients. The prevalence and type of infection changes over time and is influenced by the course of immune reconstitution post-transplant. The interaction between pathogens and host immune responses is complex in HCT settings, since the conditioning regimens create periods of neutropenia and immunosuppressive drugs are often needed to prevent graft rejection and limit graft-versus-host disease (GVHD). Experimental murine models of transplantation are valuable tools for dissecting the procedure-related alterations to innate and adaptive immunity. Here we review mouse models of post-HCT infectious pulmonary complications, primarily focused on three groups of pathogens that frequently infect HCT recipients: bacteria (often P. aeruginosa), fungus (primarily Aspergillus fumigatus), and viruses (primarily herpesviruses). These mouse models have advanced our knowledge regarding how the conditioning and HCT process negatively impacts innate immunity and have provided new potential strategies of managing the infections. Studies using mouse models have also validated clinical observations suggesting that prior or occult infections are a potential etiology of noninfectious pulmonary complications post-HCT as well.

Keeping a balance in chronic lymphocytic leukemia (CLL) patients taking ibrutinib: ibrutinib-associated adverse events and their management based on drug interactions

INTRODUCTION

Ibrutinib is a highly effective drug for patients with chronic lymphocytic leukemia (CLL), and is well tolerated even by older patients and those unfit to receive conventional immuno-chemotherapy.

AREAS COVERED

The occurrence of adverse events was revealed as a major cause of ibrutinib failure in the real-world. Ibrutinib-induced lymphocytosis carries the risk of an untimely interruption of therapy because it may be misinterpreted as disease progression. In addition, drug interactions can worsen ibrutinib-associated toxicities by increasing the plasma concentration of ibrutinib. In this review, we present a case of major hemorrhage and atrial fibrillation (AF) during ibrutinib use and summarize the adverse events associated with ibrutinib. Furthermore, the practical management of ibrutinib-associated toxicities was covered with reference to a drug interaction mechanism.

EXPERT OPINION

Clinicians should examine the prescribed drugs prior to ibrutinib initiation and carefully monitor toxicities while taking ibrutinib. A reduced dose of ibrutinib with the concurrent use of CYP3A inhibitors such as antifungal agents could be an attractive strategy to reduce toxicities and may confer financial benefits. Reducing unexpected toxicities is as significant as achieving treatment response in the era of life-long therapy with ibrutinib in patients with CLL.

Incidence and associated risk factors for invasive fungal infections and other serious infections in patients on ibrutinib

BACKGROUND

Ibrutinib is a small molecule tyrosine kinase inhibitor that blocks the activity of B cells and other immune effectors and is used in a variety of hematologic malignancies. There have been numerous reports of increased frequency of serious infections including invasive fungal infections (IFI) in patients on ibrutinib.

METHODS

Demographic and clinical features of all patients receiving ibrutinib at a single tertiary care center were collected from electronic medical records. Univariate and multivariate statistical analyses were performed to find out the factors associated with infection.

RESULTS

A total of 244 patients received ibrutinib for hematologic malignancies, of which 44 (18.0%) experienced ≥ 1 serious infection including 5 (2.0%) with IFI (1 pulmonary cryptococcosis, 4 pulmonary aspergillosis), 39 (16.0%) with bacterial infections and 8 (3.3%) with viral infections. Ten patients (4.1%) experienced multiple infections or co-infections while on ibrutinib and 10 (4.1%) expired or were transferred to hospice as a result of infection. In multivariate analysis risk factors that were less common in uninfected versus infected patients included advanced age (73 years vs. 77 years), Eastern Cooperative Oncologic Grade (ECOG) performance score ≥ 2 (6.5% vs. 31.8%) and concurrent use of steroids (4.5% vs. 20.5%) or other cytotoxic agents (0% vs. 4.6%).

CONCLUSIONS

There was a high rate of serious infection but relatively few IFI in patients receiving ibrutinib. Most patients who developed serious infections while on ibrutinib had additional predisposing risk factors including concurrent use of steroids or other cytotoxic agents, advanced age and frailty.

Future challenges and chances in the diagnosis and management of invasive mould infections in cancer patients

Diagnosis, treatment, and management of invasive mould infections (IMI) are challenged by several risk factors, including local epidemiological characteristics, the emergence of fungal resistance and the innate resistance of emerging pathogens, the use of new immunosuppressants, as well as off-target effects of new oncological drugs. The presence of specific host genetic variants and the patient's immune system status may also influence the establishment of an IMI and the outcome of its therapy. Immunological components can thus be expected to play a pivotal role not only in the risk assessment and diagnosis, but also in the treatment of IMI. Cytokines could improve the reliability of an invasive aspergillosis diagnosis by serving as biomarkers as do serological and molecular assays, since they can be easily measured, and the turnaround time is short. The use of immunological markers in the assessment of treatment response could be helpful to reduce overtreatment in high risk patients and allow prompt escalation of antifungal treatment. Mould-active prophylaxis could be better targeted to individual host needs, leading to a targeted prophylaxis in patients with known immunological profiles associated with high susceptibility for IMI, in particular invasive aspergillosis. The alteration of cellular antifungal immune response through oncological drugs and immunosuppressants heavily influences the outcome and may be even more important than the choice of the antifungal treatment. There is a need for the development of new antifungal strategies, including individualized approaches for prevention and treatment of IMI that consider genetic traits of the patients.

Lay Abstract

Anticancer and immunosuppressive drugs may alter the ability of the immune system to fight invasive mould infections and may be more important than the choice of the antifungal treatment. Individualized approaches for prevention and treatment of invasive mold infections are needed.

Prognostic Impact and Risk Factors of Infections in Patients with Chronic Lymphocytic Leukemia Treated with Ibrutinib

Ibrutinib represents extraordinary progress in the treatment of chronic lymphocytic leukemia (CLL). However, treatment-related adverse events limit the benefit of this agent. This observational, multicenter study focused on the incidence, risk factors, and prognostic impact of infections in 494 patients with CLL treated with an ibrutinib-based treatment. Ibrutinib was given to 89 (18%) previously untreated patients (combined with rituximab, 24) and 405 (82%) relapsed/refractory patients. Pneumonia (PN), grade ≥3 non-opportunistic infections (NOI), and opportunistic infections (OI) were recorded in 32% of patients with an overall incidence rate per 100 person-year of 15.3% (PN, 10%; NOI, 3.3%; OI, 2%). Infections were the reason for the permanent discontinuation of ibrutinib in 9% of patients. Patients who experienced pneumonia or a severe infection showed a significantly inferior survival than those who were infection-free (p < 0.0001). A scoring system based on the three factors associated with a significant and independent impact on infections-PN or severe infection in the year before starting ibrutinib, chronic obstructive pulmonary disease, ≥2 prior treatments-identified patients with a two- to threefold increase in the rate of infections. In conclusion, the results of this study highlight the adverse impact of infectious events on the outcomes of CLL patients treated with ibrutinib.

Targeting Bruton's Tyrosine Kinase in CLL

Targeting the B-cell receptor signaling pathway through BTK inhibition proved to be effective for the treatment of chronic lymphocytic leukemia (CLL) and other B-cell lymphomas. Covalent BTK inhibitors (BTKis) led to an unprecedented improvement in outcome in CLL, in particular for high-risk subgroups with TP53 aberration and unmutated immunoglobulin heavy-chain variable-region gene (IGHV). Ibrutinib and acalabrutinib are approved by the US Food and Drug Administration for the treatment of CLL and other B-cell lymphomas, and zanubrutinib, for patients with mantle cell lymphoma. Distinct target selectivity of individual BTKis confer differences in target-mediated as well as off-target adverse effects. Disease progression on covalent BTKis, driven by histologic transformation or selective expansion of BTK and PLCG2 mutated CLL clones, remains a major challenge in the field. Fixed duration combination regimens and reversible BTKis with non-covalent binding chemistry hold promise for the prevention and treatment of BTKi-resistant disease.

NFAT signaling in human mesenchymal stromal cells affects extracellular matrix remodeling and antifungal immune responses

Mesenchymal stromal cells (MSCs) combined with calcineurin-nuclear factor of activated T cell (CN-NFAT) inhibitors are being tested as a treatment for graft-versus-host disease (GvHD). The immunosuppressive properties of MSCs seem beneficial; however, their response during fungal infection, which is an important cause of mortality in patients with GvHD , is unknown. We report that MSCs phagocytose the fungal component zymosan, resulting in phosphorylation of spleen tyrosine kinase (Syk), increase in cytosolic calcium levels, and ultimately, increase in NFAT1 nuclear translocation. RNA sequencing analysis of zymosan-treated MSCs showed that CN-NFAT inhibition affects extracellular matrix (ECM) genes but not cytokine expression that is under the control of the NF-κB pathway. When coculturing MSCs or decellularized MSC-ECM with human peripheral blood mononuclear cells (PBMCs), selective NFAT inhibition in MSCs decreased cytokine expression by PBMCs. These findings reveal a dual mechanism underlying the MSC response to zymosan: while NF-κB directly controls inflammatory cytokine expression, NFAT impacts immune-cell functions by regulating ECM remodeling.

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Stimulation of MSCs with zymosan activates NFAT and NF-kB via the dectin1-Syk axis

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Calcineurin-NFAT inhibition impacts the expression of extracellular matrix genes

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NF-kB pathway regulates cytokine expression in zymosan-stimulated MSCs

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Selective NFAT inhibition in MSCs impacts cytokine secretion of MSC-PBMC cocultures