Distinct reconstitution of neutrophil functions after allogeneic peripheral blood stem cell transplantation

Risk beyond neutropenia: insights into neutrophil migration from newly diagnosed AML until late after allogeneic stem cell transplantation

Quantification of neutrophil counts is the most relevant assessment of cellular immunity in clinical practice. Patients with neutropenia are considered at risk and are categorized according to its severity. The incidence of febrile neutropenia varies, but patients with acute myeloid leukemia are traditionally considered at high risk, especially following myelotoxic treatments. To provide additional functional parameters, we investigated the ex vivo migration properties and morphology of neutrophils in 10 patients with acute myeloid leukemia using single-cell video-microscopy and discovered, in addition to neutropenia, highly pathological neutrophil migration patterns and polarization defects in patients with untreated acute myeloid leukemia. Neutrophil speed was the most sensitive parameter and significantly lower at leukemia diagnosis (9.067 vs 15.810 µm/min, P = 0.0025) compared to healthy controls (n = 46). Hematological remission was associated with improved neutrophil migration profiles, but these ultimately normalized only after hematopoietic cell transplantation. Five patients were followed up for long-term effects of hematopoietic cell transplantation for up to 24 mo. This is the first longitudinal ex vivo neutrophil migration study in patients with acute myeloid leukemia, followed by allogeneic hematopoietic cell transplantation. It identified functional neutrophil impairments beyond routine quantitative assessments, adding to the well-known quantitative impairment of neutropenia. HCT can reestablish functional neutrophils with healthy migration profiles in these patients.

Functional immune reconstitution early after allogeneic haematopoietic cell transplantation: A comparison of pre- and post-transplantation cytokine responses in stimulated whole blood

We aimed to use a novel standardized whole-blood stimulation system to evaluate differences in the functional immune reconstitution in patients early after allogeneic haematopoietic cell transplantation (HCT). Between April and September 2018, 30 patients undergoing HCT had whole blood samples collected around day -21 (day 0 being the day of haematopoietic cell infusion) and day +28. Whole blood was transferred to TruCulture assays comprising prefilled incubation tubes with cell culture medium and a standardized stimulus. We used a panel of four stimuli (lipopolysaccharide, resiquimod, heat-killed Candida albicans and polyinosinic:polycytidylic acid) and a blank, designed to evaluate the function of critical extra- and intracellular immunological signalling pathways. For each stimulus, the cytokine response was assessed by the concentration of interferon-γ, interleukin (IL)-12p40, IL-10, IL-1β, IL-6, IL-8, IL-10, IL-12p40, IL-17A and tumour necrosis factor-α using a multiplex Luminex assay. Pre-HCT cytokine responses were globally decreased across several different stimuli. Despite patients receiving immunosuppressive prophylaxis at the time, post-HCT cytokine responses were higher and less intercorrelated than pre-HCT responses, also after adjusting for differences in the leukocyte differential counts. For the resiquimod and heat-killed Candida albicans stimuli, we identified a cluster of patients in whom post-HCT responses were lower than average across several cytokines, indicating a possible functional immune deficiency. Our findings suggest that the standardized whole blood stimulation system can be used to reveal heterogeneity in the in vitro cytokine responses to various stimuli after HCT. Larger studies are needed to address if the functional immune reconstitution after HCT can predict the risk of infections.

Uncovering the multifaceted roles played by neutrophils in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a life-saving procedure used for the treatment of selected hematological malignancies, inborn errors of metabolism, and bone marrow failures. The role of neutrophils in alloHSCT has been traditionally evaluated only in the context of their ability to act as a first line of defense against infection. However, recent evidence has highlighted neutrophils as key effectors of innate and adaptive immune responses through a wide array of newly discovered functions. Accordingly, neutrophils are emerging as highly versatile cells that are able to acquire different, often opposite, functional capacities depending on the microenvironment and their differentiation status. Herein, we review the current knowledge on the multiple functions that neutrophils exhibit through the different stages of alloHSCT, from the hematopoietic stem cell (HSC) mobilization in the donor to the immunological reconstitution that occurs in the recipient following HSC infusion. We also discuss the influence exerted on neutrophils by the immunosuppressive drugs delivered in the course of alloHSCT as part of graft-versus-host disease (GVHD) prophylaxis. Finally, the potential involvement of neutrophils in alloHSCT-related complications, such as transplant-associated thrombotic microangiopathy (TA-TMA), acute and chronic GVHD, and cytomegalovirus (CMV) reactivation, is also discussed. Based on the data reviewed herein, the role played by neutrophils in alloHSCT is far greater than a simple antimicrobial role. However, much remains to be investigated in terms of the potential functions that neutrophils might exert during a highly complex procedure such as alloHSCT.

Assessment of Neutrophil Chemotaxis Upon G-CSF Treatment of Healthy Stem Cell Donors and in Allogeneic Transplant Recipients

Neutrophils are crucial for the human innate immunity and constitute the majority of leukocytes in circulation. Thus, blood neutrophil counts serve as a measure for the immune system's functionality. Hematological patients often have low neutrophil counts due to disease or chemotherapy. To increase neutrophil counts and thereby preventing infections in high-risk patients, recombinant G-CSF is widely used as adjunct therapy to stimulate the maturation of neutrophils. In addition, G-CSF is utilized to recruit stem cells (SCs) into the peripheral blood of SC donors. Still, the actual functionality of neutrophils resulting from G-CSF treatment remains insufficiently understood. We tested the ex vivo functionality of neutrophils isolated from blood of G-CSF-treated healthy SC donors. We quantified chemotaxis, oxidative burst, and phagocytosis before and after treatment and detected significantly reduced chemotactic activity upon G-CSF treatment. Similarly, in vitro treatment of previously untreated neutrophils with G-CSF led to reduced chemotactic activity. In addition, we revealed that this effect persists in the allogeneic SC recipients up to 4 weeks after neutrophil engraftment. Our data indicates that neutrophil quantity, as a sole measure of immunocompetence in high-risk patients should be considered cautiously as neutrophil functionality might be affected by the primary treatment.

A review of infectious complications after haploidentical hematopoietic stem cell transplantations

BACKGROUND

Allogeneic hematopoietic stem cell transplantation from haploidentical donor is a feasible option for patients with hematological diseases who lack a suitable HLA-matched donor, but viral and fungal infections are still the most common causes of morbidity and mortality in haploidentical transplantation setting because of delayed immune reconstitution, increased risk of graft vs host disease (GvHD) or systemic steroid use. Therefore, this review will focus on the infectious complications after haploidentical hematopoietic stem cell transplantation (HSCT).

MATERIALS AND METHODS

Electronic publications were searched until February 2017 throughout databases, including Pubmed, Cochrane, and Embase. The following keywords were used 'haploidentical transplantation', 'infection', 'T cell replete', and 'T cell deplete'.

RESULTS

An increased incidence of bacterial, fungal, or viral infections is detected in haplo-HSCT compared to related, unrelated, or cord blood transplantations. Neutropenia and use of systemic steroid for GvHD and delayed immune reconstitution are important risk factors for infection after haplo-HSCT.

CONCLUSION

A shift towards T cell repletes haplo-HSCT with post-transplant cyclophosphamide (CY) for GvHD has been emerged in recent years, in which the incidence of viral and fungal infections is detected to be lower. Prophylaxis and pre-emptive treatment strategies should be applied according to patient status.

Neutrophil function in children following allogeneic hematopoietic stem cell transplant

HSCT is a lifesaving procedure for children with malignant and non-malignant conditions. The conditioning regimen renders the patient severely immunocompromised and recovery starts with neutrophil (PMN) engraftment. We hypothesize that children demonstrate minimal PMN dysfunction at engraftment and beyond, which is influenced by the stem cell source and the conditioning regimen. Peripheral blood was serially collected from children at 1 to 12 months following allogeneic HSCT. PMN superoxide (O2-) production, degranulation (elastase), CD11b surface expression, and phagocytosis were assessed. Twenty-five patients, mean age of 10.5 yr with 65% males, comprised the study and transplant types included: 14 unrelated cord blood stem cells (cords), seven matched related bone marrow donors, three matched unrelated bone marrow donors, and one peripheral blood progenitor cells. Engraftment occurred at 24 days. There were no significant differences between controls and patients in PMN O2- production, phagocytosis, CD11b surface expression, and total PMN elastase. Elastase release was significantly decreased <6 months vs. controls (p < 0.05) and showed normalization by six months for cords only. The conditioning regimen did not affect PMN function. PMN function returns with engraftment, save elastase release, which occurs later related to the graft source utilized, and its clinical significance is unknown.

Inhibition of Neutrophil Extracellular Trap Formation after Stem Cell Transplant by Prostaglandin E2

RATIONALE

Autologous and allogeneic hematopoietic stem cell transplant (HSCT) patients are susceptible to pulmonary infections, including bacterial pathogens, even after hematopoietic reconstitution. We previously reported that murine bone marrow transplant (BMT) neutrophils overexpress cyclooxygenase-2, overproduce prostaglandin E2 (PGE2), and exhibit defective intracellular bacterial killing. Neutrophil extracellular traps (NETs) are DNA structures that capture and kill extracellular bacteria and other pathogens.

OBJECTIVES

To determine whether NETosis was defective after transplant and if so, whether this was regulated by PGE2 signaling.

METHODS

Neutrophils isolated from mice and humans (both control and HSCT subjects) were analyzed for NETosis in response to various stimuli in the presence or absence of PGE2 signaling modifiers.

MEASUREMENTS AND MAIN RESULTS

NETs were visualized by immunofluorescence or quantified by Sytox Green fluorescence. Treatment of BMT or HSCT neutrophils with phorbol 12-myristate 13-acetate or rapamycin resulted in reduced NET formation relative to control cells. NET formation after BMT was rescued both in vitro and in vivo with cyclooxygenase inhibitors. Additionally, the EP2 receptor antagonist (PF-04418948) or the EP4 antagonist (AE3-208) restored NET formation in neutrophils isolated from BMT mice or HSCT patients. Exogenous PGE2 treatment limited NETosis of neutrophils collected from normal human volunteers and naive mice in an exchange protein activated by cAMP- and protein kinase A-dependent manner.

CONCLUSIONS

Our results suggest blockade of the PGE2-EP2 or EP4 signaling pathway restores NETosis after transplantation. Furthermore, these data provide the first description of a physiologic inhibitor of NETosis.

Robust T cell responses to aspergillosis in chronic granulomatous disease: implications for immunotherapy

Chronic granulomatous disease (CGD) patients are highly susceptible to invasive aspergillosis and might benefit from aspergillus-specific T cell immunotherapy, which has shown promise in treating those with known T cell defects such as haematopoietic stem cell transplant (HSCT) recipients. But whether such T cell defects contribute to increased risks for aspergillus infection in CGD is unclear. Hence, we set out to characterize the aspergillus-specific T cell response in CGD. In murine CGD models and in patients with CGD we showed that the CD4(+) T cell responses to aspergillus were unimpaired: aspergillus-specific T cell frequencies were even elevated in CGD mice (P < 0·01) and humans (P = 0·02), compared to their healthy counterparts. CD4-depleted murine models suggested that the role of T cells might be redundant because resistance to aspergillus infection was conserved in CD4(+) T cell-depleted mice, similar to wild-type animals. In contrast, mice depleted of neutrophils alone or neutrophils and CD4(+) T cells developed clinical and pathological evidence of pulmonary aspergillosis and increased mortality (P < 0·05 compared to non-depleted animals). Our findings that T cells in CGD have a robust aspergillus CD4(+) T cell response suggest that CD4(+) T cell-based immunotherapy for this disease is unlikely to be beneficial.

Reconstitution and functional analyses of neutrophils and distinct subsets of monocytes after allogeneic stem cell transplantation

PURPOSE

The aim of the study was to investigate the recovery of the innate immune system within the first 100 days after allogeneic peripheral blood stem cell transplantation (PBSCT) and to elucidate a potential correlation with such important events as severe infectious complications or graft-versus-host disease (GvHD).

METHODS

In 30 consecutive patients who underwent allogeneic PBSCT, absolute numbers of neutrophils and monocytes were determined and different functional analyses performed at different time points (day +30, +60 and +90, respectively). The capacity to phagocyte Escherichia coli (E. coli) as well as the induction of oxidative burst after incubation with different stimuli (Phorbol-12-myristate-13-acetate; PMA, the chemotactic peptide N-formyl-Met-Leu-Phe; f-MLP or opsonized E. coli) were analysed after engraftment.

RESULTS

There was a rapid reconstitution concerning the capability of both neutrophils and monocytes to phagocyte E. coli without a significant increase between day +30 and +90. In contrast, a twofold increase of monocyte oxidative burst after incubation with PMA at day +90 was observed (P = 0.017). Furthermore, the ability of neutrophils to induce oxidative burst after ingestion with E. coli was impaired on day +30 with a significant functional reconstitution on day +60 (P = 0.01). The oxidative burst activity following incubation with f-MLP did not show significant changes after stem cell engraftment. Analysis of numeric reconstitution of CD14+CD16+ monocytes demonstrated a potential correlation with a decreased incidence of chronic GvHD.

CONCLUSION

The functional recovery of neutrophils and monocytes in the early period after allogeneic PBSCT differs not only concerning phagocytosis and oxidative burst but also with respect to the stimulus and the cell population that was analysed for oxidative burst activity. The subset of CD16+CD14+ monocytes might be a predictor for a reduced risk of chronic GvHD.