Efficacy of transfusion with granulocytes from G-CSF/dexamethasone-treated donors in neutropenic patients with infection

Optimized high-dose granulocyte transfusions for the treatment of infections in neutropenic patients: A single-center retrospective analysis

BACKGROUND

Granulocyte transfusions for patients with prolonged neutropenia and severe infections has been a controversial practice. Previous studies suggest a benefit of high-dose granulocyte transfusions (≥0.6 × 109/kg), although, until recently, the consistent production of high-dose units has been challenging. Here, we present our experience and results utilizing high-dose granulocyte transfusions at a large, tertiary academic medical center for the treatment of infections in adult, neutropenic patients.

STUDY DESIGN/METHODS

A retrospective chart review (2018-2021) was conducted for all patients who received high-dose granulocyte transfusions from donors stimulated with granulocyte colony-stimulating factor (G-CSF) and dexamethasone. Gathered parameters included patient demographics, clinical history, infection status, dose, clinical outcomes, pre- and post-absolute neutrophil count (ANC), and transfusion times including time between granulocyte collection, administration, and posttransfusion ANC count. Gathered parameters were summarized using descriptive statistics, outcomes were assessed utilizing Kaplan-Meier curves/log-rank/regression testing.

RESULTS

Totally 28 adult, neutropenic patients refractory to antimicrobial agents and/or G-CSF received a total of 173 granulocyte concentrates. Median ANC increased from 0.7 × 109/L pre-transfusion to 1.6 × 109/L posttransfusion. The mean granulocyte yield was 77.4 × 109 resulting in an average dose per kilogram of 0.90 × 109 ± 0.30 × 109 granulocytes. Composite day 42 survival and microbial response was 42.9% (n = 12/28) without significant adverse reactions.

DISCUSSION

Here, we demonstrate the successful and safe implementation of high-dose granulocyte transfusions for neutropenic patients. Given the rapid and consistent production, distribution, and improved granulocyte quality, further investigations to determine the clinical efficacy of G-CSF primed granulocyte transfusions is now possible.

Clinical management of a patient following a granulocyte transfusion from a donor positive for COVID-19

Granulocyte transfusions are indicated for patients with severe neutropenia and evidence of bacterial or fungal infection who are unresponsive to standard antimicrobial therapy. With a limited expiration time of 24 hours after collection, granulocytes are often transfused before results of infectious-disease screening tests are available, and before a transfusion service can perform a risk assessment if postdonation information is provided after the collection. The case we describe herein demonstrates a clinical scenario meeting indications for granulocyte transfusion, coupled with the clinical management undertaken after the granulocyte donor disclosed a positive result for a COVID-19 self-test taken 1 day after donation. In this case, the patient did not develop new COVID-19 symptoms and tested negative for COVID-19 after transfusion of the implicated unit. These findings add to the body of evidence in the literature that COVID-19 is not transmitted via blood transfusion.

Neutrophils, an emerging new therapeutic platform

Neutrophils possess unique characteristics that render them indispensable to health, and patients with irregular neutrophil counts or functions suffer from increased morbidity and mortality. As neutrophils are short-lived postmitotic cells, genetic aberrations cannot be corrected directly in neutrophils and must be targeted in their progenitors. Neutrophils are increasingly being contemplated for a range of therapeutic applications, including restoration or modulation of immune function and targeting of solid tumors. This review addresses the state-of-the-art in neutrophil transfusions and their possible applications for infectious disease prevention and treatment. It offers a landscape of the most recent gene therapy approaches to address neutrophil-related genetic diseases. We also discuss how ongoing research could broaden the applicability of neutrophil-based therapies to solid cancer treatments and beyond.

Granulocyte transfusions in severe aplastic anemia

Patients with severe aplastic anemia (SAA) are at high risk of morbidity and mortality due to severe infections. We aimed to characterize the role of granulocyte transfusions (GT) in SAA. Primary outcomes were survival after the first GT, including overall survival (OS) at last follow up, survival to discharge, and receipt of a hematopoietic stem cell transplant (HSCT) Secondary outcomes included evaluation of clinical response at 7 and 30 days after initiation of GT, using a clinical scoring system incorporating microbiological and radiographic response. Twenty-eight SAA patients underwent 30 GT courses with a per-dose median of 1.28x109 granulocytes/kilogram (range, 0.45-4.52x109). OS from initial GT to median last follow up (551 days) was 50%, with 39% (11/28) alive at last follow up. Sixty-four percent (18/28) of all patients survived to hospital discharge. Patients with a complete or partial response, or stable infection, at 30 days had significantly better OS compared to non-responders (P=0.0004). Eighty-six percent (18/21) of patients awaiting HSCT during GT underwent a transplant and 62% (13/21) survived to post-HSCT discharge. Sex, type of infection, and percentage of days with absolute neutrophil count >0.2x109/L during the course of GT were not predictive of survival (P=0.52, P=0.7 and P=0.28, respectively). Nine of 28 (32%) patients developed new or increased human leukocyte antigen alloimmunization during their GT course. GT in SAA may have an impact on survival in those patients with improvement or stabilization of their underlying infection. Alloimmunization can occur and OS in this population remains poor, but GT may be a useful tool to bridge patients to curative treatment with HSCT.

Granulocyte transfusions in life-threatening infections of children with hemato-oncological diseases

Granulocytes are the most important cells for host defense during infections. Granulocyte suspension transfusions (GTx) may be given as additional treatment in severely neutropenic patients with life-threatening infections when antimicrobial therapy is inadequate. The aim of this study was to evaluate the effectiveness and safety of GTx for the treatment of children with hemato-oncological disease, febrile neutropenia and serious life-threatening infections. Patients who underwent GTx between July 2020 and September 2022 were evaluated retrospectively. Hematologic and clinical response rates, adverse effects, characteristics of infection episodes and survival data of the patients were analyzed. During the study period, 60 patients received a total of 313 GTx for 81 infection episodes with a median number of GTx/infection episode of 3 (range 1-29). The median neutrophil count per bag was 20.8 (range 7.9-68.3) × 109 and the median neutrophil count per kg body weight was 0.82 (range 0.17-9.2) × 109. Clinical response was 85 %. Clinical response decreased significantly as the duration of neutropenia increased (p = 0.002). Hematologic response was calculated in 198 GTx (GTx given with pre-transfusion neutrophil count ≤ 0.5 × 109/L); hematologic response rate was 34 %. The infection-related mortality was 15 % and overall survival rate was 87 % and 70 % on days 30 and 90, respectively. No serious side effects were observed in any patient. Granulocyte transfusions appear to be safe and effective supportive treatment in neutropenic children with hematologic/oncologic diseases and severe infections.

Drug Repurposing of ACT001 to Discover Novel Promising Sulfide Prodrugs with Improved Safety and Potent Activity for Neutrophil-Mediated Antifungal Immunotherapy

Neutrophil-mediated immunotherapy is a promising strategy for treating Candida albicans infection due to its potential in dealing with drug-resistant events. Our previous study found that ACT001 exhibited good antifungal immunotherapeutic activity by inhibiting PD-L1 expression in neutrophils, but its strong cytotoxicity and high BBB permeability hindered its antifungal application. To address these deficiencies, a series of novel sulfide derivatives were designed and synthesized based on a slow-release prodrug strategy. Among these derivatives, compound 16 exhibited stronger inhibition of PD-L1 expression, less cytotoxicity to neutrophils, and lower BBB permeability than ACT001. Compound 16 also significantly enhanced neutrophil-mediated antifungal immunity in C. albicans infected mice, with acceptable pharmacokinetic properties and good oral safety. Moreover, pharmacological mechanism studies demonstrated that ACT001 and compound 16 reduced PD-L1 expression in neutrophils by directly targeting STAT3. Briefly, this study provided a novel prototype compound 16 which exhibited great potential in neutrophil-mediated antifungal immunotherapy.

Transfusion Support in Hematopoietic Stem Cell Transplantation: A Contemporary Narrative Review

Hematopoietic stem cell transplantation (HSCT) is a cornerstone of modern medical practice, and can only be performed safely and effectively with appropriate transfusion medicine support. Patients undergoing HSCT often develop therapy-related cytopenia, necessitating differing blood product requirements in the pre-, peri-, and post-transplant periods. Moreover, ensuring optimal management for patients alloimmunized to human leukocyte antigens (HLA) and/or red blood cell (RBC) antigens, as well as for patients receiving ABO-incompatible transplants, requires close collaboration with transfusion medicine and blood bank professionals. Finally, as updated transfusion guidelines and novel blood product modifications emerge, the options available to the transplant practitioner continue to expand. Herein, we detail contemporary blood transfusion and transfusion medicine practices for patients undergoing HSCT.

Granulocyte Transfusions in Neutropenic Infections: Insights From a Single-Center Study

Introduction Despite the development of modern antibiotic and antifungal therapies, neutropenic infections remain life-threatening. Granulocyte transfusion (GTX) is a less frequently used treatment modality in patients with refractory neutropenic infections. The role of donor GTX remains controversial, partly because of the lack of proper clinical trials. This study aimed to contribute to the literature by evaluating the efficacy and side effects of granulocyte transfusions in our center. Methods Eight febrile neutropenic patients with confirmed infections received granulocyte transfusions from ABO-compatible related and unrelated donors. Donors received filgrastim and dexamethasone stimulation, and granulocyte suspensions were irradiated and administered within six hours. Monitoring, antibiotic therapy, and granulocyte colony-stimulating factor (G-CSF) support were maintained. Results Our study observed a 28-day survival rate of 25%, which was lower than that reported in previous literature. The median number of transfusions was 3, with an average eight-day duration post-infection diagnosis, and no side effects were observed. Conclusion While some patients benefited from GTX, overall survival rates remained modest, indicating the need for further research. Prospective, well-powered randomized controlled trials are essential to address patient selection, dosing, and duration to determine the clinical utility of GTX. This study underscores the complexity of GTX in real-world clinical practice and provides insight into the ongoing debate regarding its efficacy in treating severe neutropenic infections.

Acute Invasive Pulmonary Aspergillosis: Clinical Presentation and Treatment

Among all clinical manifestations of pulmonary aspergillosis, invasive pulmonary aspergillosis (IPA) is the most acute presentation. IPA is caused by Aspergillus hyphae invading the pulmonary tissue, causing either tracheobronchitis and/or bronchopneumonia. The degree of fungal invasion into the respiratory tissue can be seen as a spectrum, going from colonization to deep tissue penetration with angio-invasion, and largely depends on the host's immune status. Patients with prolonged, severe neutropenia and patients with graft-versus-host disease are at particularly high risk. However, IPA also occurs in other groups of immunocompromised and nonimmunocompromised patients, like solid organ transplant recipients or critically ill patients with severe viral disease. While a diagnosis of proven IPA is challenging and often warranted by safety and feasibility, physicians must rely on a combination of clinical, radiological, and mycological features to assess the likelihood for the presence of IPA. Triazoles are the first-choice regimen, and the choice of the drug should be made on an individual basis. Adjunctive therapy such as immunomodulatory treatment should also be taken into account. Despite an improving and evolving diagnostic and therapeutic armamentarium, the burden and mortality of IPA still remains high. This review aims to give a comprehensive and didactic overview of the current knowledge and best practices regarding the epidemiology, clinical presentation, diagnosis, and treatment of acute IPA.

AKT2 inhibition accelerates the acquisition of phagocytic ability in induced pluripotent stem cell-derived neutrophils

Neutrophils are key components of the immune system that inhibit bacterial infections. Systemic bacterial infections can cause lethal conditions, especially in patients with neutropenia associated with chemotherapy or other systemic illnesses; hence, early detection of the symptoms and prompt management are crucial in such cases. Previously, we established expandable engineered neutrophil-primed progenitors (NeuPs-XL) using human-induced pluripotent stem cells (iPSCs), which can produce neutrophil-like cells at a clinically suitable scale within 4 days of inducing myeloid differentiation. In this study, using small-molecule compound-based screening, we detected that MK-2206, a selective pan-AKT inhibitor, can accelerate this differentiation process, promote phagocytic ability in neutrophils, and enhance cytokine and chemokine expression in response to lipopolysaccharides. The inhibition of AKT2 has been identified as the key mechanism underlying this acceleration. These results can make a substantial contribution to the development of strategies for the prompt production of clinically applicable iPSC-derived neutrophils, which can potentially lead to the management of severe infections associated with life-threatening neutropenia and the effective treatment of related health conditions in the future.

Comparison of two apheresis systems for granulocyte collection without hydroxyethyl starch

BACKGROUND AND OBJECTIVES

Granulocyte transfusion (GTX) is a treatment option for severe infections in patients with neutropenia. In previous studies, hydroxyethyl starch (HES) was used to enhance red blood cell sedimentation for granulocyte collection (GC). However, there are safety concerns about HES, and HES is not readily available in some countries. Therefore, we compared the granulocyte counts and GC efficiency achieved by two apheresis systems without HES.

MATERIALS AND METHODS

All consecutive GC procedures performed between July 2011 and March 2018 at our hospital were analysed. COBE Spectra was used until 5 February 2016, and Spectra Optia was used afterwards. HES was not used.

RESULTS

Twenty-six GC procedures were performed, including 18 performed using COBE Spectra and 8 using Spectra Optia. When Spectra Optia was used, >1 × 1010 neutrophils were collected from seven of the eight (88%) procedures. Although there was no significant difference in the granulocyte yield between COBE Spectra-based and Spectra Optia-based GC procedures, the collection efficiency of Spectra Optia was significantly higher than that of COBE Spectra (p = 0.021). Furthermore, the granulocyte yields of Spectra Optia-based GC tended to be more strongly correlated with the peripheral blood neutrophil count on the day of apheresis than those of COBE Spectra-based GC.

CONCLUSION

Our results suggest that Spectra Optia achieves greater GC efficiency than COBE Spectra, even without HES. GTX may be a therapeutic option for severe neutropenia, even in places where HES is not available.

A study on beneficial impact of the use of medium-molecular-weight hydroxyethyl starch in granulocyte apheresis using continuous-flow cell separator Spectra Optia: A retrospective single-center study at a tertiary care oncology center

INTRODUCTION

Granulocyte transfusion is one of the best therapeutic modalities in prolonged neutropenic patients with severe bacterial/fungal infections. Granulocyte harvest using conventional acid citrate dextrose (ACD) anticoagulant (ACD-A) by apheresis is not satisfactory in comparison to the use of hydroxyethyl starch (HES), but the latter is associated with various adverse events, especially with high-molecular-weight HES.

AIMS AND OBJECTIVE

This study aimed to assess the beneficial impact of the use of medium-molecular-weight (MMW)-HES and trisodium citrate combination over ACD-A in granulocyte apheresis when using Spectra Optia.

MATERIALS AND METHODS

This was a retrospective study comparing granulocyte harvest results with the use of ACD or HES and trisodium citrate combination. All the donors in both the groups received single 600 μg of granulocyte colony-stimulating factor subcutaneous injection followed by 8 mg of dexamethasone tablet 10-12 h and omnacortil 60 mg orally 3 h before harvest. A number of adverse incidents, if any, were observed and noted. Donor/procedure parameters were compared using Mann-Whitney U-test/unpaired t-test.

RESULTS

Granulocyte yield (mean: 3.29 × 1010/unit vs. 4.5 × 1010/unit in the ACD and HES groups, respectively, P ≤ 0.0001) was significantly better in the HES group. The collection efficiency was also better in the HES group (mean: 15.86% vs. 26.70% in the ACD and HES groups, respectively, P ≤ 0.0001) in the ACD and HES groups, respectively. There was no significant adverse event noted in any of these two groups.

CONCLUSION

In our study, granulocytes with optimum yield can be easily harvested with Spectra Optia cell separator using 6% HES (MMW) and trisodium citrate combination with standard 12-h interval gap between mobilization and harvest. This strategy can also have no or minimal extra cost burden to patients.

Navigating the neutropenic abyss with granulocyte transfusions: Retrospective single-center analysis of effectiveness and safety in India

BACKGROUND

Hemato-oncologic patients receiving intensive chemotherapy may develop severe neutropenia and serious bacterial and/or fungal infections. Granulocyte transfusions (GTs) may be beneficial as a bridging therapy in hemato-oncologic patients with febrile neutropenia.

AIM

To evaluate the clinical effectiveness of GTs in hemato-oncologic patients with febrile neutropenia.

MATERIALS AND METHODS

This retrospective study evaluated the effectiveness of 150 GTs in 88 hemato-oncologic patients. Donors were mobilized with granulocyte colony-stimulating factors and dexamethasone. Patients' hematological parameters (pre- and post-GT) and safety and effectiveness of GTs were analyzed.

RESULTS

The safety and effectiveness of GTs were assessed in the patients with various underlying conditions, including 78% with acute myeloid leukemia. In total, 150 GTs were administered, mostly during the chemotherapy induction phase. The GTs were well-tolerated by the patients, and a significant increment in white blood cell count and absolute neutrophil count (ANC) was noticed in 95% of patients after the transfusion. The granulocyte dose was positively correlated with ANC after the transfusion. The average time to neutrophil recovery from the last day of GT was 6.7 days, and the 30-day survival rate was 77%. The donors were all men, and a significant increase in WBC count was observed post-mobilization. The median granulocyte yield was 2.28 × 1010 /unit. All granulocyte products were crossmatched and irradiated before the transfusion.

CONCLUSION

GTs can be a useful adjunctive treatment for febrile neutropenia in hemato-oncologic patients with multidrug-resistant sepsis. However, additional studies are required for confirming their effectiveness and establishing guidelines for their use.

Recent advances in microfluidic cell separation to enable centrifugation-free, low extracorporeal volume leukapheresis in pediatric patients

Leukapheresis is a common extracorporeal procedure for leukodepletion and cellular collection. During the procedure, a patient's blood is passed through an apheresis machine to separate white blood cells (WBCs) from red blood cells (RBCs) and platelets (PLTs), which are then returned to the patient. Although it is well-tolerated by adults and older children, leukapheresis poses a significant risk to neonates and low-weight infants because the extracorporeal volume (ECV) of a typical leukapheresis circuit represents a particularly large fraction of their total blood volume. The reliance of existing apheresis technology on centrifugation for separating blood cells limits the degree to which the circuit ECV could be miniaturized. The rapidly advancing field of microfluidic cell separation holds excellent promise for devices with competitive separation performance and void volumes that are orders of magnitude smaller than their centrifugation-based counterparts. This review discusses recent advancements in the field, focusing on passive separation methods that could potentially be adapted to perform leukapheresis. We first outline the performance requirements that any separation method must meet to replace centrifugation-based methods successfully. We then provide an overview of the passive separation methods that can remove WBCs from whole blood, focusing on the technological advancements made in the last decade. We describe and compare standard performance metrics, including blood dilution requirements, WBC separation efficiency, RBC and PLT loss, and processing throughput, and discuss the potential of each separation method for future use as a high-throughput microfluidic leukapheresis platform. Finally, we outline the primary common challenges that must still be overcome for these novel microfluidic technologies to enable centrifugation-free, low-ECV leukapheresis in the pediatric setting.

Investigational non-antibiotic therapeutics for infections in hematopoietic cell transplant recipients and patients with hematologic malignancies receiving cellular therapies

In the age of progressive antimicrobial resistance and increased difficulty combating infections in immunocompromised hosts, there has been renewed interest in the use of nontraditional therapeutics for infections. Herein, we review the use of investigational non-pharmaceutical anti-infective agents targeting fungal, bacterial, and viral infections in patients with hematologic malignancies, focusing on those receiving hematopoietic cell transplantation or cellular therapies. We discuss immune checkpoint inhibitors, granulocyte transfusions, bone marrow colony-stimulating factors, bacteriophages, fecal microbiota transplantation, and virus specific T-cell therapy. Although there is promising early experience with many of these treatments, further studies will be required to define their optimal role in the therapeutic armamentarium against infections in immunocompromised hosts.

Machine Learning Predicts 30-Day Outcome among Acute Myeloid Leukemia Patients: A Single-Center, Retrospective, Cohort Study

Acute myeloid leukemia (AML) is a clinical emergency requiring treatment and results in high 30-day (D30) mortality. In this study, the prediction of D30 survival was studied using a machine learning (ML) method. The total cohort consisted of 1700 survivors and 130 non-survivors at D30. Eight clinical and 42 laboratory variables were collected at the time of diagnosis by pathology. Among them, six variables were selected by a feature selection method: induction chemotherapy (CTx), hemorrhage, infection, C-reactive protein, blood urea nitrogen, and lactate dehydrogenase. Clinical and laboratory data were entered into the training model for D30 survival prediction, followed by testing. Among the tested ML algorithms, the decision tree (DT) algorithm showed higher accuracy, the highest sensitivity, and specificity values (95% CI) of 90.6% (0.918-0.951), 70.4% (0.885-0.924), and 92.1% (0.885-0.924), respectively. DT classified patients into eight specific groups with distinct features. Group 1 with CTx showed a favorable outcome with a survival rate of 97.8% (1469/1502). Group 6, with hemorrhage and the lowest fibrinogen level at diagnosis, showed the worst survival rate of 45.5% (25/55) and 20.5 days. Prediction of D30 survival among AML patients by classification of patients with DT showed distinct features that might support clinical decision-making.

Efficiently normalizing leukopoiesis by gadofullerene nanoparticles to ameliorate radiation-triggered myelosuppression

Myelosuppression is a predominant side-effect of radiotherapy, which manifests as the lower activity of blood cell precursors in bone marrow. Though progress in anti-myelosuppression has been made by the application of growth factors e.g., the granulocyte colony-stimulating factor (G-CSF), the side-effects (e.g., bone-pain, liver injury, and lung toxicity) limit their applications in clinic. Herein, we developed a strategy of efficiently normalizing leukopoiesis using gadofullerene nanoparticles (GFNPs) against myelosuppression triggered by radiation. Specifically, GFNPs with high radical-scavenging abilities elevated the generation of leukocytes and alleviated the bone marrow's pathological state under myelosuppression. Notably, GFNPs potentiated the differentiation, development, and maturation of leukocytes (neutrophils, lymphocytes) in radiation bearing mice even better than what G-CSF did. In addition, GFNPs had little toxicity towards the main organs including the heart, liver, spleen, lung, and kidney. This work provides an in-depth understanding of how advanced nanomaterials mitigate myelosuppression by regulating leukopoiesis.

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.

Transfusion support in hematopoietic stem cell transplantation

Transfusion support for hematopoietic stem cell transplantation (HSCT) is an essential part of supportive care, and compatible blood should be transfused into recipients. As leukocyte antigen (HLA) matching is considered first and as the blood group does not impede HSCT, major, minor, bidirectional, and RhD incompatibilities occur that might hinder transfusion and cause adverse events. Leukocyte reduction in blood products is frequently used, and irradiation should be performed for blood products, except for plasma. To mitigate incompatibility and adverse events, local transfusion guidelines, hospital transfusion committees, and patient management should be considered.

Fulminant Metastatic Cellulitis Caused by Stenotrophomonas Maltophilia Infection and Subsequent Candida Parapsilosis Fungemia After Cord Blood Transplantation

Stenotrophomonas maltophilia is known to be an opportunistic pathogen with intrinsic and acquired resistance mechanisms to multiple antibiotics. Bloodstream infection caused by S. maltophilia is a potentially fatal complication, especially in recipients of umbilical cord blood transplantation (CBT). Infrequent reports of S. maltophilia skin and soft tissue infections (SSTIs), including metastatic cellulitis and ecthyma gangrenosum, have been reported as wound infections. Metastatic cellulitis lesions due to S. maltophilia are typically reported to be tender, erythematous, and to show warm subcutaneous infiltration. There are only a few available reports about the clinical course of metastatic cellulitis due to S. maltophilia. We experienced a case involving the development of metastatic cellulitis with fulminant and extensive exfoliation in a patient who underwent CBT. Despite controlling the bloodstream infection caused by S. maltophilia, the patient succumbed to secondary fungal infection due to the devastation of the skin barrier. Our case highlights that SSTIs due to S. maltophilia can cause the unexpected development of fulminant metastatic cellulitis with systemic epidermal peeling in severely immunocompromised hosts, including CBT recipients undergoing steroid therapy.

In Vitro Human Haematopoietic Stem Cell Expansion and Differentiation

The haematopoietic system plays an essential role in our health and survival. It is comprised of a range of mature blood and immune cell types, including oxygen-carrying erythrocytes, platelet-producing megakaryocytes and infection-fighting myeloid and lymphoid cells. Self-renewing multipotent haematopoietic stem cells (HSCs) and a range of intermediate haematopoietic progenitor cell types differentiate into these mature cell types to continuously support haematopoietic system homeostasis throughout life. This process of haematopoiesis is tightly regulated in vivo and primarily takes place in the bone marrow. Over the years, a range of in vitro culture systems have been developed, either to expand haematopoietic stem and progenitor cells or to differentiate them into the various haematopoietic lineages, based on the use of recombinant cytokines, co-culture systems and/or small molecules. These approaches provide important tractable models to study human haematopoiesis in vitro. Additionally, haematopoietic cell culture systems are being developed and clinical tested as a source of cell products for transplantation and transfusion medicine. This review discusses the in vitro culture protocols for human HSC expansion and differentiation, and summarises the key factors involved in these biological processes.

Non-Aspergillus Hyaline Molds: A Host-Based Perspective of Emerging Pathogenic Fungi Causing Sinopulmonary Diseases

The incidence of invasive sino-pulmonary diseases due to non-Aspergillus hyaline molds is increasing due to an enlarging and evolving population of immunosuppressed hosts as well as improvements in the capabilities of molecular-based diagnostics. Herein, we review the following opportunistic pathogens known to cause sinopulmonary disease, the most common manifestation of hyalohyphomycosis: Fusarium spp., Scedosporium spp., Lomentospora prolificans, Scopulariopsis spp., Trichoderma spp., Acremonium spp., Paecilomyces variotii, Purpureocillium lilacinum, Rasamsonia argillacea species complex, Arthrographis kalrae, and Penicillium species. To facilitate an understanding of the epidemiology and clinical features of sino-pulmonary hyalohyphomycoses in the context of host immune impairment, we utilized a host-based approach encompassing the following underlying conditions: neutropenia, hematologic malignancy, hematopoietic and solid organ transplantation, chronic granulomatous disease, acquired immunodeficiency syndrome, cystic fibrosis, and healthy individuals who sustain burns, trauma, or iatrogenic exposures. We further summarize the pre-clinical and clinical data informing antifungal management for each pathogen and consider the role of adjunctive surgery and/or immunomodulatory treatments to optimize patient outcome.

How are granulocytes for transfusion best used? The past, the present and the future

Granulocyte transfusions continue to be used in clinical practice, predominantly for treatment of refractory infection in the setting of severe neutropenia. There is biological plausibility for effectiveness in these patients with deficiencies of neutrophils, either as a consequence of disease or treatment. However, there is a chequered history of conducting and completing interventional trials to define optimal use, and many uncertainties remain regarding schedule and dose. Practice and clinical studies are severely limited by the short shelf life and viability of current products, which often restricts the timely access to granulocyte transfusions. In the future, methods are needed to optimise donor-derived granulocyte products. Options include use of manufactured neutrophils, expanded and engineered from stem cells. Further possibilities include manipulation of neutrophils to enhance their function and/or longevity. Granulocyte transfusions contain a heterogeneous mix of cells, and there is additional interest in how these transfusions may have immunomodulatory effects, including for potential uses as adjuncts for anti-cancer effects.

Recombinant GM-CSF for diseases of GM-CSF insufficiency: Correcting dysfunctional mononuclear phagocyte disorders

Introduction

Endogenous granulocyte-macrophage colony-stimulating factor (GM-CSF), identified by its ability to support differentiation of hematopoietic cells into several types of myeloid cells, is now known to support maturation and maintain the metabolic capacity of mononuclear phagocytes including monocytes, macrophages, and dendritic cells. These cells sense and attack potential pathogens, present antigens to adaptive immune cells, and recruit other immune cells. Recombinant human (rhu) GM-CSF (e.g., sargramostim [glycosylated, yeast-derived rhu GM-CSF]) has immune modulating properties and can restore the normal function of mononuclear phagocytes rendered dysfunctional by deficient or insufficient endogenous GM-CSF.

Methods

We reviewed the emerging biologic and cellular effects of GM-CSF. Experts in clinical disease areas caused by deficient or insufficient endogenous GM-CSF examined the role of GM-CSF in mononuclear phagocyte disorders including autoimmune pulmonary alveolar proteinosis (aPAP), diverse infections (including COVID-19), wound healing, and anti-cancer immune checkpoint inhibitor therapy.

Results

We discuss emerging data for GM-CSF biology including the positive effects on mitochondrial function and cell metabolism, augmentation of phagocytosis and efferocytosis, and immune cell modulation. We further address how giving exogenous rhu GM-CSF may control or treat mononuclear phagocyte dysfunction disorders caused or exacerbated by GM-CSF deficiency or insufficiency. We discuss how rhu GM-CSF may augment the anti-cancer effects of immune checkpoint inhibitor immunotherapy as well as ameliorate immune-related adverse events.

Discussion

We identify research gaps, opportunities, and the concept that rhu GM-CSF, by supporting and restoring the metabolic capacity and function of mononuclear phagocytes, can have significant therapeutic effects. rhu GM-CSF (e.g., sargramostim) might ameliorate multiple diseases of GM-CSF deficiency or insufficiency and address a high unmet medical need.

Therapeutic Approaches for Combating Aspergillus Associated Infection

Now-a-days fungal infection emerges as a significant problem to healthcare management systems due to high frequency of associated morbidity, mortality toxicity, drug-drug interactions, and resistance of the antifungal agents. Aspergillus is the most common mold that cause infection in immunocompromised hosts. It's a hyaline mold that is cosmopolitan and ubiquitous in nature. Aspergillus infects around 10 million population each year with a mortality rate of 30-90%. Clinically available antifungal formulations are restricted to four classes (i.e., polyene, triazole, echinocandin, and allylamine), and each of them have their own limitations associated with the activity spectrum, the emergence of resistance, and toxicity. Consequently, novel antifungal agents with modified and altered chemical structures are required to combat these invasive fungal infections. To overcome these limitations, there is an urgent need for new antifungal agents that can act as potent drugs in near future. Currently, some compounds have shown effective antifungal activity. In this review article, we have discussed all potential antifungal therapies that contain old antifungal drugs, combination therapies, and recent novel antifungal formulations, with a focus on the Aspergillus associated infections.

Granulocyte Transfusion Therapy: Institutional Experience of Benefit in Cancer Patients with Prolonged Neutropenic Sepsis—A Retrospective Study

Introduction Patients undergoing intensive chemotherapy for hematological malignancy and stem cell transplantation are at increased risk of neutropenia.

Neutropenia is among the frequent side effects of intensive treatments, and when absolute neutrophil count (ANC) falls < 500/µL, the risk of microbial and fungal infection increases significantly.

As neutropenia is the main cause of these infections, transfusion of granulocyte immediately as a replacement is a life-saving therapeutic option to support these patients by restoring neutrophil counts and aiding in the resolution of infection.

Objective The present study is a retrospective single institutional analysis of granulocyte transfusion therapy in children and young adults with cancer who received treatment with GT during prolonged and profound life threatening neutropenia.

Materials and Methods This study was a retrospective analysis of 66 granulocyte transfusions in 36 patients of hematological and solid malignancy with severe and prolonged neutropenia in the department of Medical Oncology, Sri Aurobindo Institute of Medical Sciences Indore, between September 2019 and March 2022.

Donors were either patients' relatives or voluntary donors without comorbidities.

All granulocyte concentrates were collected by centrifugation leukapheresis and irradiated with 2500 centigray and immediately transfused in full, to the patient over 60 ot 120 minutes with appropriate premedication.

Results A total of 36 patients (M:F, 19:17) with a median age of 16 years (2–43) received 66 granulocyte transfusions. The diagnosis of patients included acute myelogenous leukemia (n = 17), B cell acute lymphoblastic leukemia (n = 10), non-Hodgkin lymphoma (n = 3), Ewing's sarcoma (n = 2), neuroblastoma (n = 1), malignant melanoma (n = 1), aplastic anemia (n = 1), osteosarcoma (n = 1). All had severe neutropenia with absolute neutrophil count < 0.5 × 109/L. The median duration of severe neutropenia was 16 days. Patients received a median cell dose of granulocytes 2.9 × 1010/L. A favorable response was seen in 28 (78%) patients, whereas an unfavorable response was seen in 8 patients (23%).

Conclusion A granulocyte therapy was effective in many critically sick patients with prolonged and profound neutropenia. Granulocyte transfusions may be more beneficial in selected patients where it provides more time to overcome refractory infections with broad-spectrum antibiotics. Granulocyte transfusion are at best a “bridge” that gives time to marrow recovery. The challenges to using GT are clinical, finding patients who may get benefitted, and logistical, selection of donors and harvest technique. Randomized trials with large numbers of patients are required to prepare guidelines for granulocyte use.

Cui Bono? Identifying Patient Groups That May Benefit From Granulocyte Transfusions in Pediatric Hematology and Oncology

INTRODUCTION

Granulocyte transfusions have long been used to bridge the time to neutrophil recovery in patients with neutropenia and severe infection. Recent randomized controlled trials did not prove a beneficial effect of granulocyte transfusions, but were likely underpowered and suffered from very heterogeneous study populations.

METHODS

We retrospectively reviewed data of all patients treated with granulocyte transfusions at our pediatric center from 2004 to 2019. To identify parameters that predict the success of granulocyte transfusions, we stratified patients in 3 groups. Patients in group 1 cleared their infection, whereas patients in group 2 succumbed to an infection in neutropenia despite granulocyte transfusions. A third group included all patients who died of causes that were not related to infection.

RESULTS

We demonstrate that patients without respiratory or cardiocirculatory insufficiency are enriched in group 1 and more likely to benefit from granulocyte transfusions than patients who already require these intensive care measures. The effect of granulocyte transfusions correlates with the cell dose per body weight applied per time. With our standard twice weekly dosing, patients with a body weight below 40 kg are more likely to achieve a sufficient leukocyte increment and clear their infection in comparison to patients with a higher body weight.

DISCUSSION/CONCLUSIONS

We suggest that future studies on the benefits of granulocyte transfusions stratify patients according to clinical risk factors that include the need for respiratory or cardiocirculatory support and strive for a sufficient dose density of granulocyte transfusions.

Mucormycosis in Children With Hematologic Malignancies: A Case Series and Review of the Literature

BACKGROUND

Mucormycosis is classified as the third leading cause of invasive fungal disease in immunocompromised patients and is characterized by high morbidity and mortality (33%-56%). The aim of this study is to describe presentation, treatment and outcome of Dutch pediatric hemato-oncology patients recently diagnosed with mucormycosis and to review the literature to gain more insight specifically into contemporary outcome data.

METHODS

Ten cases were diagnosed in the Princess Máxima Center for Pediatric Oncology from 2018 to 2021 and were retrospectively reviewed. In addition, 9 case series (n = 148) were included from literature.

RESULTS

In our case series, 5 patients of 10 children (age 2-17 years) had disseminated invasive fungal disease. Four patients had localized pulmonary disease and 1 had a localized renal infection. One diagnosis was made postmortem. The underlying diseases were acute lymphoblastic leukemia (n = 6), acute myeloid leukemia (n = 2) and lymphoma (n=2). Seven patients received combination therapy comprising of a lipid amphotericin B formulation and a triazole, surgery was performed in 67%. All neutropenic patients received granulocyte transfusions and/or granulocyte colony-stimulating factor. Mucormycosis-related mortality was 20%. In the literature review, mucormycosis-related mortality was 36% for all patients and 66% for patients with disseminated disease. Survival rates were similar over the past 2 decades. The most common underlying disorder was acute lymphoblastic leukemia. Liposomal amphotericin B was the mainstay of treatment. Seventy percent of patients underwent surgery.

CONCLUSIONS

Although survival of mucormycosis improved significantly overtime, it plateaued in the past decades. This series shows that with screening, early diagnostics and early antifungal and if possible surgical treatment, mortality is low and even disseminated disease is salvageable if approached aggressively with a combination of surgery and antifungal treatment. Further research focused on diagnostics, combination antifungal and adjunctive therapy is necessary to enhance the survival of mucormycosis in children.

Risk stratification by 30-day prognostic factors of clinical outcomes after granulocyte transfusion in acute myeloid leukemia: A single-center retrospective study

Background

Granulocyte transfusions (GTs) have been used to treat infections in neutropenic patients undergoing chemotherapy or hematopoietic stem cell transplantation. However, there is persistent controversy regarding their outcomes. We aimed to analyze accumulated clinical and laboratory data from patients with acute myeloid leukemia (AML) who underwent GT at our institution in the last 10 years to determine optimal parameters to estimate the GT effect. We hypothesized that patients grouped according to prognostic factors would have inconsistent clinical outcomes.

Materials and methods

In this single-center retrospective study, we collected medical records of 219 GT-treated patients diagnosed with AML from 2009 to 2019. Prognostic factors, including clinical and laboratory parameters, were assessed. Serial measurements of laboratory parameters before and after GT were collected, and the area under the curve of the white blood cells (AUC-WBC) was calculated using the trapezoidal method. A prognostic scoring system using 8 factors from multivariate analysis was analyzed. The primary outcome was survival at 30 days (D30) after GT initiation.

Results

The 8 factors for the prognosis scoring system included secondary AML, mean AUC-WBC, prothrombin time, and levels of blood urea nitrogen (BUN), bilirubin, alanine aminotransferase (ALT), phosphorus, and lactate dehydrogenase (LDH). Patients were grouped into 4 risk groups (low, medium, high, and very high), and the D30 survival rates for each group were as follows: 87.6% (99/113), 55.9% (33/59), 21.1% (4/19), and 0% (0/19), respectively. Hematopoiesis, liver, and renal function affected the outcome. FLT3 mutation acted as a favorable factor for D30 survival.

Conclusions

GT response in patients with AML seemed to be reflected by 8 score markers, and GT was significantly effective in the low-risk group. We suggest that it is important to evaluate the risk assessment of patients before GT to achieve better outcomes.

A high-throughput microfluidic device based on controlled incremental filtration to enable centrifugation-free, low extracorporeal volume leukapheresis

Leukapheresis, the extracorporeal separation of white blood cells (WBCs) from red blood cells (RBCs) and platelets (PLTs), is a life-saving procedure used for treating patients with cancer and other conditions, and as the initial step in the manufacturing of cellular and gene-based therapies. Well-tolerated by adults, leukapheresis poses a significant risk to neonates and low-weight infants because the extracorporeal volume (ECV) of standard centrifugation-based machines represents a particularly large fraction of these patients' total blood volume. Here we describe a novel high-throughput microfluidic device (with a void volume of 0.4 mL) based on controlled incremental filtration (CIF) technology that could replace centrifugation for performing leukapheresis. The CIF device was tested extensively using whole blood from healthy volunteers at multiple hematocrits (5-30%) and flow rates (10-30 mL/min). In the flow-through regime, the CIF device separated WBCs with > 85% efficiency and 10-15% loss of RBCs and PLTs while processing whole blood diluted with saline to 10% hematocrit at a flow rate of 10 mL/min. In the recirculation regime, the CIF device demonstrated a similar level of separation performance, virtually depleting WBCs in the recirculating blood (~ 98% reduction) by the end of a 3.5-hour simulated leukapheresis procedure. Importantly, the device operated without clogging or decline in separation performance, with minimal activation of WBCs and PLTs and no measurable damage to RBCs. Compared to the typical parameters of centrifugation-based leukapheresis, the CIF device had a void volume at least 100-fold smaller, removed WBCs about twice as fast, and lost ~ 2-3-fold fewer PLTs, while operating at a flow rate compatible with the current practice. The hematocrit and flow rate at which the CIF device operated were significantly higher than previously published for other microfluidic cell separation methods. Finally, this study is the first to demonstrate a highly efficient separation of cells from recirculating blood using a microfluidic device. Overall, these findings suggest the feasibility of using high-throughput microfluidic cell separation technology to ultimately enable centrifugation-free, low-ECV leukapheresis. Such a capability would be particularly useful in young children, a vulnerable group of patients who are currently underserved.

Granulocyte Transfusions in Patients with Chronic Granulomatous Disease Undergoing Hematopoietic Cell Transplantation or Gene Therapy

Granulocyte transfusions are sometimes used as adjunctive therapy for the treatment of infection in patients with chronic granulomatous disease (CGD). However, granulocyte transfusions can be associated with a high rate of alloimmunization, and their role in CGD patients undergoing hematopoietic cell transplantation (HCT) or gene therapy (GT) is unknown. We identified 27 patients with CGD who received granulocyte transfusions pre- (within 6 months) and/or post-HCT or GT in a retrospective survey. Twelve patients received granulocyte transfusions as a bridge to cellular therapy. Six (50%) of these patients had a complete or partial response. However, six of 10 (60%) patients for whom testing was performed developed anti-HLA antibodies, and three of the patients also had severe immune-mediated cytopenia within the first 100 days post-HCT or GT. Fifteen patients received granulocyte transfusions post-HCT only. HLA antibodies were not checked for any of these 15 patients, but there were no cases of early immune-mediated cytopenia. Out of 25 patients who underwent HCT, there were 5 (20%) cases of primary graft failure. Three of the patients with primary graft failure had received granulocyte transfusions pre-HCT and were subsequently found to have anti-HLA antibodies. In this small cohort of patients with CGD, granulocyte transfusions pre-HCT or GT were associated with high rates of alloimmunization, primary graft failure, and early severe immune-mediated cytopenia post-HCT or GT. Granulocyte transfusions post-HCT do not appear to confer an increased risk of graft failure.

NET Release of Long-Term Surviving Neutrophils

Background

Neutrophil extracellular traps (NETs)—as double-edged swords of innate immunity—are involved in numerous processes such as infection, inflammation and tissue repair. Research on neutrophil granulocytes is limited because of their short lifetime of only a few hours. Several attempts have been made to prolong the half-life of neutrophils using cytokines and bacterial products and have shown promising results. These long-term surviving neutrophils are reported to maintain phagocytic activity and cytokine release; however, little is known regarding their capability to release NETs.

Methods

We analysed the prolongation of neutrophil survival in vitro under various culture conditions using granulocyte colony-stimulating factor (G-CSF), lipopolysaccharide (LPS) or tumour necrosis factor alpha (TNF-α) by flow cytometry and a viability assay. Additionally, we assessed NET formation following stimulation with phorbol 12-myristate 13-acetate (PMA) by immunofluorescence staining, myeloperoxidase (MPO)-DNA sandwich-ELISA and fluorometric assays for cell-free DNA (cfDNA), neutrophil elastase (NE) and myeloperoxidase (MPO).

Results

Untreated neutrophils could form NETs after stimulation with PMA for up to 24 h. Incubation with LPS extended their ability to form NETs for up to 48 h. At 48 h, NET release of neutrophils cultured with LPS was significantly higher compared to that of untreated cells; however, no significantly different enzymatic activity of NE and MPO was observed. Similarly, incubation with G-CSF resulted in significantly higher NET release at 48 h compared to untreated cells. Furthermore, NETs showed significantly higher enzymatic activity of NE and MPO after incubation with G-CSF. Lastly, incubation with TNF-α had no influence on NET release compared to untreated cells although survival counts were altered by TNF-α.

Conclusions

G-CSF, LPS or TNF-α each at low concentrations lead to prolonged survival of cultured neutrophils, resulting in considerable differences in NET formation and composition. These results provide new information for the use of neutrophils in long-term experiments for NET formation and provide novel insights for neutrophil behaviour under inflammatory conditions.

Suppression of Aspergillus fumigatus Germination by Neutrophils Is Enhanced by Endothelial-Derived CSF3 Production

Infection with Aspergillus fumigatus can cause life-threatening diseases in immunocompromised patients with an unacceptable mortality rate. Angioinvasion is one of the features of severe invasive aspergillosis. Neutrophils are short-lived immune cells regulated by colony-stimulating factor 3 (CSF3) that play a key role in anti-fungal immune responses. To investigate the interactions between A. fumigatus and the host immune cells, such as neutrophils, we stimulated human umbilical vein endothelial cells (HUVECs) with the conidia of A. fumigatus, and co-cultured them with human neutrophils. Apoptosis and functions of neutrophils were analyzed. Our results showed that HUVECs upregulate the expression of CSF3, which could reduce the apoptosis of neutrophils while enhancing their functions. Lack of CSF3 was associated with enhanced apoptosis of neutrophils with impaired function. This work indicated that the CSF3 is required for neutrophil survival and function, at least in the early stages of A. fumigatus infection.

Assessment of Safety and Immunogenicity of MHC homozygous iPSC-derived CD34+ Hematopoietic Progenitors in a NHP Model

Infusion of iHPs is safe and well tolerated in NHPs.

iHPs are hypoimmunogenic and can be administered with a low risk of alloimmunization.

Administration of ex vivo expanded somatic myeloid progenitors has been explored as a way to facilitate a more rapid myeloid recovery and improve overall survival after myeloablation. Recent advances in induced pluripotent stem cell (iPSC) technologies have created alternative platforms for supplying off-the-shelf immunologically compatible myeloid progenitors, including cellular products derived from major histocompatibility complex (MHC) homozygous superdonors, potentially increasing the availability of MHC-matching cells and maximizing the utility of stem cell banking. However, the teratogenic and tumorigenic potential of iPSC-derived progenitor cells and whether they will induce alloreactive antibodies upon transfer remain unclear. We evaluated the safety and efficacy of using CD34⁺CD45⁺ hematopoietic progenitors derived from MHC homozygous iPSCs (iHPs) to treat cytopenia after myeloablative hematopoietic stem cell (HSC) transplantation in a Mauritian cynomolgus macaque (MCM) nonhuman primate (NHP) model. We demonstrated that infusion of iHPs was well tolerated and safe, observing no teratomas or tumors in the MCMs up to 1 year after HSC transplantation and iHP infusion. Importantly, the iHPs also did not induce significant levels of alloantibodies in MHC-matched or -mismatched immunocompetent MCMs, even after increasing MHC expression on iHPs with interferon-γ. These results support the feasibility of iHP use in the setting of myeloablation and suggest that iHP products pose a low risk of inducing alloreactive antibodies.

Transfusable neutrophil progenitors as cellular therapy for the prevention of invasive fungal infections

The use of mature neutrophil (granulocyte) transfusions for the treatment of neutropenic patients with invasive fungal infections (IFIs) has been the focus of multiple clinical trials. Despite these efforts, the transfusion of mature neutrophils has resulted in limited clinical benefit, likely owing to problems of insufficient numbers and the very short lifespan of these donor cells. In this report, we employed a system of conditionally immortalized murine neutrophil progenitors that are capable of continuous expansion, allowing for the generation of unlimited numbers of homogenous granulocyte-macrophage progenitors (GMPs). These GMPs were assayed in vivo to demonstrate their effect on survival in 2 models of IFI: candidemia and pulmonary aspergillosis. Mature neutrophils derived from GMPs executed all cardinal functions of neutrophils. Transfused GMPs homed to the bone marrow and spleen, where they completed normal differentiation to mature neutrophils. These neutrophils were capable of homing and extravasation in response to inflammatory stimuli using a sterile peritoneal challenge model. Furthermore, conditionally immortalized GMP transfusions significantly improved survival in models of candidemia and pulmonary aspergillosis. These data confirm the therapeutic benefit of prophylactic GMP transfusions in the setting of neutropenia and encourage development of progenitor cellular therapies for the management of fungal disease in high-risk patients.

The Role of Granulocyte Transfusions in Optimizing Candidacy for Chimeric Antigen Receptor T-cell Therapy in Patients With Treatment-refractory Infections

While advancements in cellular therapy have improved outcomes for patients with refractory leukemia, severe infections may hinder access. Granulocyte transfusions, in combination with anti-microbial therapy, may be a safe option to facilitate candidacy for chimeric antigen receptor T-cell therapy in patients with leukemia and prolonged immune-compromised status.

Hematopoietic stem and progenitor cells improve survival from sepsis by boosting immunomodulatory cells

New therapeutic strategies to reduce sepsis-related mortality are urgently needed, as sepsis accounts for one in five deaths worldwide. Since hematopoietic stem and progenitor cells (HSPCs) are responsible for producing blood and immune cells, including in response to immunological stress, we explored their potential for treating sepsis. In a mouse model of Group A Streptococcus (GAS)-induced sepsis, severe immunological stress was associated with significant depletion of bone marrow HSPCs and mortality within approximately 5–7 days. We hypothesized that the inflammatory environment of GAS infection drives rapid HSPC differentiation and depletion that can be rescued by infusion of donor HSPCs. Indeed, infusion of 10,000 naïve HSPCs into GAS-infected mice resulted in rapid myelopoiesis and a 50–60% increase in overall survival. Surprisingly, mice receiving donor HSPCs displayed a similar pathogen load compared to untreated mice. Flow cytometric analysis revealed a significantly increased number of myeloid-derived suppressor cells in HSPC-infused mice, which correlated with reduced inflammatory cytokine levels and restored HSPC levels. These findings suggest that HSPCs play an essential immunomodulatory role that may translate into new therapeutic strategies for sepsis.

Efficient production of human neutrophils from iPSCs that prevent murine lethal infection with immune cell recruitment

Neutrophils play an essential role in innate immune responses to bacterial and fungal infections, and loss of neutrophil function can increase the risk of acquiring lethal infections in clinical settings. Here, we show that engineered neutrophil-primed progenitors derived from human induced pluripotent stem cells can produce functional neutrophil-like cells at a clinically applicable scale that can act rapidly in vivo against lethal bacterial infections. Using 5 different mouse models, we systematically demonstrated that these neutrophil-like cells migrate to sites of inflammation and infection and increase survival against bacterial infection. In addition, we found that these human neutrophil-like cells can recruit murine immune cells. This system potentially provides a straight-forward solution for patients with neutrophil deficiency: an off-the-shelf neutrophil transfusion. This platform should facilitate the administration of human neutrophils for a broad spectrum of physiological and pathological conditions.

Granulocyte transfusions made with modified fluid gelatin in pediatric and adolescent patients with prolonged neutropenia

BACKGROUND

Granulocyte transfusions (GT) are used to treat progressive systemic or local infections in prolonged neutropenic patients with antibiotic or antifungal resistance. Granulocytes are most commonly collected from whole blood by apheresis using hydroxyethyl starch (HES) as the red blood cell (RBC) sedimentation agent. This is the first study on the safety and efficacy of transfusing granulocytes collected with modified fluid gelatin (MFG) instead of HES to pediatric patients.

METHODS

Clinical data from 46 pediatric and adolescent patients receiving at least one MFG-based granulocyte transfusion and in total 295 granulocyte concentrates from July 2013 to August 2019 at our local university medical center were evaluated retrospectively.

RESULTS

Forty-one patients (89%) survived at least 21 days after their last granulocyte transfusion. These survivors had lower CRP values and higher leukocyte counts after GT than non-survivors (mean delta of -5.34 mg/dl vs. -11.99 mg/dl and + 0.62 × 10³ /μl vs. +0.18 × 10³ /μl of all GT, respectively). The neutrophil corrected count increment (CCI) was 68.72 mm² /ml in survivors versus 28.00 mm² /ml in non-survivors. There were no major or severe adverse events.

CONCLUSION

This study suggests that modified fluid gelatin is a safe and effective alternative to hydroxyethyl starch for the collection of granulocytes for transfusion to prolonged neutropenic patients with progressive systemic or local infections refractory to antibiotic or antifungal therapy.

Prolonged storage of purified granulocyte concentrates: Introduction of a new purification method

BACKGROUND

Use of donor granulocyte concentrate (GC) has been limited due to its short storage time of 6-24 h, which is partially due to residual red blood cells (RBCs) and platelets and the resulting lactate production leading to an acidotic milieu. To increase this storage time, we developed a closed system procedure compatible with standard blood bank technologies to remove RBC and platelets and to enrich the GC.

METHODS

Standard GCs (sGCs) were sedimented, washed twice with 0.9% sodium chloride (NaCl), and resuspended in blood group-identical fresh frozen plasma. The resulting purified GCs (pGCs) were then stored in platelet bags at a cell concentration of about 5 × 10⁷  ± 1.8 × 10⁷ leukocytes/ml without agitation at room temperature for up to 72 h. Cell count and viability, pH, blood gases, phagocytosis, and oxidative burst were monitored daily.

RESULTS

A significant reduction in RBC (98%) through sedimentation, and platelets (96%) by washing, purified the white blood cell (WBC) population and enriched the granulocytes to 96% of the WBC in the pGC. After 72 h of storage, over 90% of the initial WBC count of pGC remained, was viable (≥97%), and the granulocytes exhibited a high phagocytosis and oxidative burst functionality, comparable to sGC after 24 h.

CONCLUSION

Purification extends the maximum storage period of GC from 24 to 72 h and may therefore improve the availability of GC and its clinical use.

Survival among children and adults treated with granulocyte transfusions: Twenty years' experience at a Brazilian blood center

BACKGROUND

It remains controversial whether granulocyte transfusions as a supportive treatment improve survival in patients with febrile neutropenia or granulocyte dysfunctions. We describe survival rates subsequent to granulocyte transfusions in pediatric and adults patients treated at a major blood center in Brazil.

MATERIAL AND METHODS

We retrospectively reviewed the clinical charts of pediatric and adult patients treated with granulocyte transfusions at our institution from January 2000 to October 2019. We assessed demographic characteristics, clinical features, indications for transfusion, units transfused, dose of granulocytes administered and survival rates 30 and 100 days after the initial transfusion.

RESULTS

We identified 64 pediatric and 67 adult patients treated with 262 granulocyte transfusions. An optimal dose (> 0.6 × 10⁹ granulocytes per kilogram per transfused unit) was available for transfusion in 80.4 % of pediatric patients but in only 19.6 % of adults (p = 0.017). Thirty days after their first granulocyte transfusion, 38 (59.4 %) pediatric and 61 (91 %) adult patients had died. Patients receiving the optimal dose of granulocytes had better survival outcomes, but even among this sub-group, adults were more likely to die than were children either at 30 days (OR = 8.67, 95 %CI 2.69-34.9) or 100 days (OR = 6.27, 95 %CI 1.86-25.9) after their initial granulocyte transfusion.

CONCLUSION

Survival rates following granulocyte transfusion varied by the dose transfused and were higher in children than in adults.

Granulocyte Transfusion: Clinical Updates and a Practical Approach to Transfusion

Neutrophils are an integral component of the innate immune system and key regulators of cell-mediated defense against bacterial and fungal pathogens. The potential of granulocyte transfusions has been investigated to temporarily replenish innate immune function to prevent and/or treat infections in patients with severe neutropenia or neutrophil dysfunction. However, evidence has been largely theoretical, experimental, and/or inconclusive. Clinical efficacy has yet to be confirmed by large-scale randomized controlled clinical trials. Performing such trials has been hampered by low granulocyte collection yield and poor patient accrual. We provide a practical summary of the current literature surrounding the practice of granulocyte transfusion.