Immune Reconstitution and Immunotherapy After Autologous Hematopoietic Stem Cell Transplantation

T cell subgroup analysis and T cell exhaustion after autologous stem cell transplantation in lymphoma patients

BACKGROUND

Autologous stem cell transplantation (ASCT) is a common treatment option for relapsed/refractory (R/R) lymphomas and it is considered standard of care as primary consolidation therapy for some types of Non-Hodgkin Lymphomas (NHL). Although ASCT benefits patients by allowing cytoreduction with intensive chemotherapy and reconstituting with stem cells, the effects of immunological changes in T cell subgroups after ASCT are still poorly understood.

OBJECTIVES

We evaluated changes in frequencies of T cell subsets and T cells expressing some of the exhaustion markers (such as LAG-3 and PD-1) from peripheral blood samples before and after ASCT to investigate bone marrow reconstruction and whether exhaustion predicts relapse.

STUDY DESIGN

Blood samples were collected on the day before conditioning and at the 1st, 3rd, and 6th months post-ASCT. Flow cytometry analysis was conducted to examine T cell subgroup composition and exhaustion markers, including PD-1 and LAG-3. Additionally, functional analysis was performed using assays for IFN-g and TNF-a production. Furthermore, a CSFE proliferation assay was utilized to assess proliferation capacity.

RESULTS

In our data set, dominant cells post-transplantation were memory cells, as the naïve cell population did not recover for 6 months. Both single and combined expressions of LAG-3 and PD-1 were found to be high before transplantation, and decreased after transplantation. However, LAG-3 and PD-1 expression increased in the 3rd and 6th month after transplantation respectively. These changes were more evident for the relapsed patients when compared to non-relapsed patients within 3 months follow-up time. Notably, the expression of inhibitory receptors in the relapsed patients was significantly higher at the first month post-transplantation. CD107a+ cytotoxic T lymphocytes (CTL), IFN-g+, TNF-a.+ CTL and T helper lymphocyte (THL) populations significantly decreased in relapsed patients 3rd month after transplantation. Decreased proliferation capacities of CTLs and THLs were also observed in these patients.

CONCLUSION

These results suggest that increased surface PD-1 and LAG-3 expressions along with functional decline after 3 months of ASCT can be used as prognostic data about the relapse status of transplant patients.

Next-generation sequencing protocol of hematopoietic stem cells (HSCs). Step-by-step overview and troubleshooting guide

Populations of very small embryonic-like stem cells (VSELs) (CD34+lin-CD45- and CD133+lin-CD45-), circulating in the peripheral blood of adults in small numbers, have been identified in several human tissues and together with the populations of hematopoietic stem cells (HSCs) (CD34+lin-CD45+) and CD133+lin-CD45+constitute a pool of cells with self-renewal and pluripotent stem cell characteristics. Using advanced cell staining and sorting strategies, we isolated populations of VSELs and HSCs for bulk RNA-Seq analysis to compare the transcriptomic profiles of both cell populations. Libraries were prepared from an extremely small number of cells; however, their good quality was preserved, and they met the criteria for sequencing. We present here a step-by-step NGS protocol for sequencing VSELs and HSC with a description of troubleshooting during library preparation and sequencing.

MicroRNA Profiles in Hematopoietic Stem Cell Transplant Recipients

Background: Hematopoietic Stem Cell Transplant (HCT) is a potentially curative treatment for hematologic malignancies, including multiple myeloma. Biomarker investigation can guide identification of HCT recipients at-risk for poor outcomes. MicroRNAs (miRNAs) are a class of non-coding RNAs involved in the modulation and regulation of pathological processes and are emerging as prognostic and predictive biomarkers for multiple health conditions. This pilot study aimed to examine miRNA profiles associated with HCT-related risk factors and outcomes in patients undergoing autologous HCT. Methods: Patients eligible for autologous HCT were recruited and blood samples and HCT-related variables were collected. Differential expression analysis of miRNA was conducted on 24 patient samples to compare changes in miRNA profile in HCT eligible patients before and after transplant. Results: Unsupervised clustering of differentially expressed (p < .05) miRNAs pre- and post- HCT identified clusters of up- and down-regulated miRNAs. Four miRNAs (miR-125a-5p, miR-99b-5p, miR-382-5p, miR-145-5p) involved in hematopoiesis (differentiation of progenitor cells, granulocyte function, thrombopoiesis, and tumor suppression) were significantly downregulated post-HCT. Correlation analyses identified select miRNAs associated with risk factors (such as frailty, fatigue, cognitive decline) and quality of life pre- and post-HCT. Select miRNAs were correlated with platelet engraftment. Conclusion: Future studies should examine miRNA signatures in larger cohorts in association with HCT outcomes; and expand investigations in patients receiving allogeneic transplants. This will lead to identification of biomarkers for risk stratification of HCT recipients.

Autologous haematopoiesis stem cell transplantation (AHSCT) for treatment-refractory autoimmune diseases in children

OBJECTIVES

To evaluate the long-term effectiveness and safety of autologous haematopoiesis stem cell transplantation (AHSCT) for severe, refractory autoimmune diseases in paediatric patients.

METHODS

A single-centre study of consecutive children and adolescents with refractory autoimmune diseases undergoing AHSCT was performed. Demographics, clinical, laboratory features, pre-AHSCT medications, disease activity and functional status were captured. The primary outcome was progression-free survival, secondary outcomes included overall survival, disease-specific treatment responses, disease activity at the last follow-up and AHSCT safety.

RESULTS

The study included seven patients: two systemic sclerosis, one pansclerotic morphoea, one eosinophilic fasciitis, one juvenile dermatomyositis and two patients with systemic juvenile idiopathic arthritis; four women, three men median age at AHSCT of 10 years (7-19), median follow-up post-AHSCT of 17 years. Median progression-free survival and overall survival was 4.2 years (95% CI: 0.98 to 8.3) and 17 years (95% CI: 11.8 to 22.1), respectively. Progression-free survival rates at 1 and 2 years post-AHSCT were 100% and 77%, respectively. All children survived. All patients are in clinical remission, only four require ongoing immunotherapy.

SAFETY

Three experienced infections, including HHV6, Candida and Ralstonia sepsis; one developed a systemic inflammatory response syndrome; two new onset secondary autoimmune diseases including autoimmune haemolytic anaemia, Graves' disease and one was found to have a breast fibroadenoma. Treatment toxicity: one cyclophosphamide-associated transient renal failure and pericardial effusion, one patient with amenorrhoea/infertility.

CONCLUSIONS

AHSCT was an effective and safe approach for children and adolescents with treatment-refractory autoimmune diseases. The indication and timing of transplantation requires a careful consideration and a multidisciplinary approach.

Enrichment of effector memory T cells in the CD4 and CD8 T cell compartment during chronic graft versus host disease in children

BACKGROUND

During allogeneic Hematopoietic stem cell transplantation (HSCT), frequent pathological scenarios include graft versus host disease (GVHD) and viral infections. We hypothesized if exogenous stimulus as alloantigen and viral antigens might impact on central and effector memory T cells in pediatric recipients.

PATIENTS AND METHODS

Subjects included 21 pediatric recipients and 20 healthy children (control group). Peripheral blood samples of patients were collected along the first 712 days post-HSCT. T cell phenotyping of naïve, central, and effector memory T cells (TCMs and TEMs, respectively) was conducted using flow cytometry. Viral nucleic acids were detected using real-time PCR.

RESULTS

T cell reconstitution was not reached after 1 year post-HSCT. Chronic GVHD was associated with increased numbers of naïve CD4 T cells (p < 0.05) as well as an increase in TEM and TCM cells of the CD4 (p < 0.0001 and p < 0.05, respectively) and CD8 T cell TEM (p < 0.0001). and TCM (p < 0.001) populations too. Moreover, BK and Epstein-Barr viruses were the main viral pathogens detected (<104 copies), which were associated with a decrease in all T cell compartments.

CONCLUSION

During chronic GVHD, alloantigen persistence generates TEM cell enrichment among CD4 and CD8 T cells, and viral infections are associated with deficient recovery of T cells after HSCT.

CAR+ and CAR- T cells share a differentiation trajectory into an NK-like subset after CD19 CAR T cell infusion in patients with B cell malignancies

Chimeric antigen receptor (CAR) T cell therapy is effective in treating B cell malignancies, but factors influencing the persistence of functional CAR+ T cells, such as product composition, patients' lymphodepletion, and immune reconstitution, are not well understood. To shed light on this issue, here we conduct a single-cell multi-omics analysis of transcriptional, clonal, and phenotypic profiles from pre- to 1-month post-infusion of CAR+ and CAR- T cells from patients from a CARTELL study (ACTRN12617001579381) who received a donor-derived 4-1BB CAR product targeting CD19. Following infusion, CAR+ T cells and CAR- T cells shows similar differentiation profiles with clonally expanded populations across heterogeneous phenotypes, demonstrating clonal lineages and phenotypic plasticity. We validate these findings in 31 patients with large B cell lymphoma treated with CD19 CAR T therapy. For these patients, we identify using longitudinal mass-cytometry data an association between NK-like subsets and clinical outcomes at 6 months with both CAR+ and CAR- T cells. These results suggest that non-CAR-derived signals can provide information about patients' immune recovery and be used as correlate of clinically relevant parameters.

The shifting roles and toxicities of cellular therapies in B-cell malignancies

Cellular therapies provide a curative-intent option for patients with relapsedand refractory lymphomas. Current options including high dose chemotherapyfollowed by autologous or allogeneic hematopoietic stem cell transplantation or CD19 chimericantigen receptor T-cell (CART) therapy. The indication varies according to lymphoma sub-type and line oftherapy. The sequencing of these therapies and their use in second-line orlater settings to manage these diseases is undergoing significant changes, withCD19 CAR T becoming a preferred option for relapsed aggressive B-cell lymphoma.The mechanism of both therapies causes significant yet distinctlymphodepletion, infectious, and inflammatory toxicities. The resulting patternand timing of immune reconstitution helps guide risk-mitigating strategies,revaccination, and infectious prophylaxis. In this review, we discuss theindication, efficacy, toxicity and immune reconstitution of autologoushematopoietic stem cell transplantation and CAR T therapy for use in thetreatment of lymphoma.

Iatrogenic Kaposi's sarcoma from induction therapy for myeloma: to transplant or not to transplant?

We present the case of an HIV-negative man in his 50s who developed a generalised nodular rash while having first-line bortezomib-cyclophosphamide-dexamethasone chemotherapy for multiple myeloma. The rash was biopsied and proven to be Kaposi's sarcoma. The patient's treatment was interrupted at the sixth cycle of chemotherapy, by which time the rash had also spread to the oral mucosa and eyelid. The rash regressed spontaneously on stopping treatment. We were reluctant to restart myeloma treatment, but on the other hand, we wished to consolidate the very good partial response achieved. An autologous marrow transplant was done months later without any recurrence of his Kaposi's with the initiation of bortezomib maintenance. Bortezomib has putative activity against Kaposi's. The patient could benefit from imid-based (thalidomide, lenalidomide, pomalidomide) combination chemotherapy once his myeloma progresses or if there is a recurrence of Kaposi's sarcoma.

Atypical haemolytic uremic syndrome with refractory multiorgan involvement and heterozygous CFHR1/CFHR3 gene deletion

BACKGROUND

We present this challenging case report of Atypical Haemolytic Uremic Syndrome (aHUS) presenting with multi-organ involvement in a patient and heterozygous CFHR1/CFHR3 gene variant, which was refractory to initial eculizumab therapy.

CASE PRESENTATION

A forty-three year old female presented with aHUS and had heterozygous disease-associated deletions in the complement genes CFHR1/CFHR3. She had progressive kidney failure and severe extra-renal manifestations including cardiomyopathy and haemorrhagic cystitis; as well as pulmonary, gastrointestinal and neurological involvement. The initial kidney biopsy revealed thrombotic microangiopathy (TMA) changes involving all glomeruli. Clinical improvement was initially seen during eculizumab initiation with suppressed CH50 level, but a new rhinovirus/enterovirus upper respiratory tract infection triggered further severe multi-organ disease activity. The extra-renal manifestations stabilised, then ultimately improved after a period of eculizumab dose intensification. However, the impact on dose intensification on this improvement is unclear. Despite the extra-renal clinical improvement, she ultimately progressed to end-stage kidney disease (ESKD), commencing peritoneal dialysis for three years before undergoing a successful uncomplicated cadaveric kidney transplant without prophylactic eculizumab. Two years after transplant, she has excellent transplant graft function without any further disease recurrence.

CONCLUSIONS

This case highlights the concept of extra-renal manifestations in aHUS initially resistant to eculizumab, which potentially responded to dose intensification. Whilst organ injuries are potentially reversible with timely targeted treatment, it appears that the kidneys are most vulnerable to injury.

Incidence and risk factors of opportunistic infections after autologous stem cell transplantation: a nationwide, population-based cohort study in Korea

Several guidelines classify autologous stem cell transplantation (ASCT) as a low to intermediate risk group for infection. In a nationwide population-based study, using the Korean Health Insurance Review and Assessment Service database, patients with lymphoma and multiple myeloma (MM) who underwent ASCT from 2002 to 2016 were retrospectively analyzed. Cumulative incidence rates (CIRs) and risk factors of opportunistic infections were investigated. CIRs of fungal, Varicella zoster virus (VZV), cytomegalovirus (CMV), and Pneumocystis jirovecii infections in lymphoma were 7.9%, 16.0%, 7.4%, and 5.1%, respectively, and CIRs in MM were 6.3%, 19.1%, 4.2%, and 5.6%, respectively. Fungal infection was significantly higher in patients with previous infection (Hazard ratio (HR) 2.003, p = 0.005) in lymphoma. Incidence of CMV infection was significantly higher in patients with prior CMV infection: HR 4.920, p < 0.001 (lymphoma); HR 3.022, p = 0.030 (MM). VZV infection was significantly lower in patients receiving prophylaxis: HR 0.082, p < 0.001 (lymphoma); HR 0.096, p < 0.001 (MM). For P. jirovecii infection, busulfex and melphalan conditioning (HR 1.875, p = 0.032) and previous P. jirovecii infection (HR 4.810, p < 0.001) had a higher incidence in MM. Patients who underwent ASCT should receive VZV prophylaxis and prophylaxis for fungal and P. jirovecii may be considered in patients with previous same infection.

Natural Killer Cells Are Key Host Immune Effector Cells Affecting Survival in Autologous Peripheral Blood Hematopoietic Stem Cell Transplantation

The infusion of autograft immune effector cells directly impacts the clinical outcomes of patients treated with autologous peripheral blood hematopoietic stem cell transplantation, suggesting the possibility of an autologous graft-versus tumor cells. Furthermore, the early recovery of immune effector cells also affects survival post-autologous peripheral blood hematopoietic stem cell transplantation. Natural killer cells are among the immune effector cells reported to be collected, infused, and recovered early post-autologous peripheral blood hematopoietic stem cell transplantation. In this review, I attempt to give an update on the role of natural killer cells regarding improving survival outcomes on patients treated with autologous peripheral blood hematopoietic stem cell transplantation.

Lymphopenia and Mechanisms of T-Cell Regeneration

Chronic lymphopenia, in particular, T-lymphocyte deficiency, increases the risk of death from cancer, cardiovascular and respiratory diseases and serves as a risk factor for a severe course and poor outcome of infectious diseases such as COVID-19. The regeneration of T-lymphocytes is a complex multilevel process, many questions of which still remain unanswered. The present review considers two main pathways of increasing the T-cell number in lymphopenia: production in the thymus and homeostatic proliferation in the periphery. Literature data on the signals that regulate each pathway are summarized. Their contribution to the quantitative and qualitative restoration of the immune cell pool is analyzed. The features of CD4⁺ and CD8⁺ T-lymphocytes’ regeneration are considered.

Prognostic impact of natural killer cell recovery on minimal residual disease after autologous stem cell transplantation in multiple myeloma

INTRODUCTION

Natural killer cells are a potent effector lymphocyte subset that can induce cytotoxicity without the need for antigen sensitization or presentation. NK cells are a tempting target -for immune therapy, monoclonal antibody, or genetic engineering-to enhance immune surveillance mechanisms against myeloma cells.

MATERIALS AND METHODS

We hypothesized an association between natural killer cell recovery after autologous stem cell transplantation (ASCT) and disease outcomes in multiple myeloma patients. We concluded a prospective study that started enrolling patients in January 2020 to identify the association between absolute NK cell count two to three after ASCT and disease outcomes after autologous stem cell transplantation in multiple myeloma using univariate and multivariate analysis.

RESULTS

Natural killer cell recovery was evaluated during the third month after ASCT, day +60 to +90 post-ASCT. Our patients had a mean NK cell count of 90.53, ranging from 14 to 282 Cell/μL (Std Dev 84.64 Cell/μL). The odds of having a minimal residual disease (MRD-positivity) among patients with partial remission before transplantation is four times higher than patients with very good partial response or better (95% confidence interval 0.45-35.79). Our patients were classified into two groups based on MRD status after ASCT, an MRD-negative group of eight participants and an MRD-positive group of seven participants. The mean absolute NK cell count was significantly higher in the MRD-negative cohort, 131.38 Cell/μL, versus 43.86 Cell/μL in the MRD-positive group (p = 0.049).

CONCLUSION

We conclude that for multiple myeloma patients treated with ASCT, high absolute NK cell counts two to three months after ASCT is an independent predictor for MRD negativity.

Lymphoid and myeloid immune cell reconstitution after nicotinamide-expanded cord blood transplantation

Omidubicel (nicotinamide-expanded cord blood) is a potential alternative source for allogeneic hematopoietic cell transplantation (HCT) when an HLA-identical donor is lacking. A phase I/II trial with standalone omidubicel HCT showed rapid and robust neutrophil and platelet engraftment. In this study, we evaluated the immune reconstitution (IR) of patients receiving omidubicel grafts during the first 6 months post-transplant, as IR is critical for favorable outcomes of the procedure. Data was collected from the omidubicel phase I-II international, multicenter trial. The primary endpoint was the probability of achieving adequate CD4+ T-cell IR (CD4IR: > 50 × 106/L within 100 days). Secondary endpoints were the recovery of T-cells, natural killer (NK)-cells, B-cells, dendritic cells (DC), and monocytes as determined with multicolor flow cytometry. LOESS-regression curves and cumulative incidence plots were used for data description. Thirty-six omidubicel recipients (median 44; 13-63 years) were included, and IR data was available from 28 recipients. Of these patients, 90% achieved adequate CD4IR. Overall, IR was complete and consisted of T-cell, monocyte, DC, and notably fast NK- and B-cell reconstitution, compared to conventional grafts. Our data show that transplantation of adolescent and adult patients with omidubicel results in full and broad IR, which is comparable with IR after HCT with conventional graft sources.

Immune control of cytomegalovirus reactivation in stem cell transplantation

The reactivation of viruses from latency after allogeneic stem cell transplantation (SCT) continues to represent a major clinical challenge requiring sophisticated monitoring strategies in the context of prophylactic and/or pre-emptive antiviral drugs that are associated with significant expense, toxicity, and rates of failure. Accumulating evidence has demonstrated the association of polyfunctional virus-specific T-cells with protection from viral reactivation, affirmed by the ability of adoptively transferred virus-specific T-cells to prevent and treat reactivation and disease. The roles of innate cells (NK cells) in early viral surveillance, and dendritic cells in priming of T-cells have also been delineated. Most recently, a role for strain-specific humoral responses in preventing early cytomegalovirus (CMV) reactivation has been demonstrated in preclinical models. Despite these advances, many unknowns remain: what are the critical innate and adaptive responses over time, is the origin (e.g. recipient versus donor) and localization (e.g. in parenchymal tissue versus lymphoid organs) of these responses important, how does GVHD and the prevention/treatment thereof (e.g. high dose steroids) impact the functionality and relevance of a particular immune axis, do the immune parameters that control latency, reactivation and dissemination differ, and what is the impact of new antiviral drugs on the development of enduring antiviral immunity. Thus, whilst antiviral drugs have provided major improvements over the last two decades, understanding the immunological paradigms underpinning protective antiviral immunity after SCT offers the potential to generate non-toxic immune-based therapeutic approaches for lasting protection from viral reactivation.

Autologous Stem Cell Transplantation for Myeloma: Cytoreduction or an Immunotherapy?

The incidence of multiple myeloma (MM), a bone marrow (BM) resident hematological malignancy, is increasing globally. The disease has substantial morbidity and mortality and remains largely incurable. Clinical studies show that autologous stem cell transplantation (ASCT) remains efficacious in eligible patients, providing a progression free survival (PFS) benefit beyond novel therapies alone. Conventionally, improved PFS after ASCT is attributed to cytoreduction from myeloablative chemotherapy. However, ASCT results in immune effects beyond cytoreduction, including inflammation, lymphodepletion, T cell priming via immunogenic cell death, and disruption of the tumor BM microenvironment. In fact, a small subset of patients achieve very long-term control of disease post-ASCT, akin to that seen in the context of immune-mediated graft-vs.-myeloma effects after allogeneic SCT. These clinical observations coupled with recent definitive studies in mice demonstrating that progression after ASCT represents immune escape as a consequence of T cell exhaustion, highlight the potential for new immunotherapy maintenance strategies to prevent myeloma progression following consolidation with ASCT.

Thresholds for post-rebound SHIV control after CCR5 gene-edited autologous hematopoietic cell transplantation

Autologous, CCR5 gene-edited hematopoietic stem and progenitor cell (HSPC) transplantation is a promising strategy for achieving HIV remission. However, only a fraction of HSPCs can be edited ex vivo to provide protection against infection. To project the thresholds of CCR5-edition necessary for HIV remission, we developed a mathematical model that recapitulates blood T cell reconstitution and plasma simian-HIV (SHIV) dynamics from SHIV-1157ipd3N4-infected pig-tailed macaques that underwent autologous transplantation with CCR5 gene editing. The model predicts that viral control can be obtained following analytical treatment interruption (ATI) when: (1) transplanted HSPCs are at least fivefold higher than residual endogenous HSPCs after total body irradiation and (2) the fraction of protected HSPCs in the transplant achieves a threshold (76-94%) sufficient to overcome transplantation-dependent loss of SHIV immunity. Under these conditions, if ATI is withheld until transplanted gene-modified cells engraft and reconstitute to a steady state, spontaneous viral control is projected to occur.

Low B cell counts as risk factor for infectious complications in systemic sclerosis after autologous hematopoietic stem cell transplantation

Background

Autologous hematopoietic stem cell transplantation (aHSCT) is a treatment option for a selected group of systemic sclerosis (SSc) patients with good available evidence but can be associated with considerable morbidity and mortality. The aim of this study was to describe infectious complications and distinct immune reconstitution patterns after aHSCT and to detect risk factors in lymphocyte subsets, which are associated with an elevated rate of infections after aHSCT.

Methods

Seventeen patients with SSc were included in this single-center retrospective cohort study. Clinical and laboratory data was collected before and for 12 months after aHSCT, including immunophenotyping of peripheral whole blood by fluorescence-activated cell sorting.

Results

Cytomegalovirus (CMV) reactivations were common in CMV-IgG-positive patients (50%) and needed treatment. Mycotic infections occurred in 17.6%. One patient died (resulting in a mortality of 5.9%) due to pneumonia with consecutive sepsis. All patients showed decreased T helper cells (CD3⁺/CD4⁺) and within the B cell compartment decreased post-switched memory B cells (CD19⁺/CD27⁺/IgD⁻) and elevated naïve B cells (CD19⁺/CD27⁻/IgD⁺) until 12 months after aHSCT. Patients who developed infections had significantly lower B cells before aHSCT than patients who did not develop infections.

Conclusion

After aHSCT, monitoring for infectious complications, especially for CMV reactivations, is crucial as the reconstitution of the immune system takes longer than 12 months. Low peripheral B cells might be a risk factor for an elevated infection rate.

Effectiveness and Cost-Effectiveness of Prophylactic Voriconazole and Fluconazole Regarding Prevention of Post-hematopoietic Stem Cell Transplantation Invasive Fungal Infection and Its Related Death: A Single Center Experience

Purpose

Analyzing effectiveness and cost-effectiveness of voriconazole versus fluconazole prophylaxis in hematopoietic stem cell transplantation (HSCT).

Methods

The research included 70 patients; 34 undergoing allogeneic HSCT and 36 undergoing autologous stem cell transplantation (ASCT), alternated to receive either voriconazole or fluconazole prophylaxis for 180 days on a 1:1 basis. Patients were monitored for occurrence of invasive fungal infections (IFI), IFI-related death (IRD) and total death events. Cost-effectiveness of both agents in both groups was also assessed.

Results

Antifungal prophylactic drug had no impact on incidence of IFI and IRD in both allogeneic HSCT and ASCT (P = .452 and P = 1.000; P = .457 and P = .146 respectively). An insignificant difference occurred among patients receiving voriconazole or fluconazole regarding overall survival (OS) and fungal infection-free survival (FFS) in both groups (P = .705 and P = .879; P = .713 and P = .681 respectively). Regarding cost-effectiveness, voriconazole dominated fluconazole regarding prevention of IFI and IRD but was less costly/less effective regarding prevention of total death events and gaining life years in the allogeneic HSCT setting. In the ASCT setting, voriconazole was not cost-effective regarding avoidance of IFI and IRD and was dominated by fluconazole regarding avoidance of total death events and gaining life years.

Conclusions

Voriconazole does not differ from fluconazole regarding its efficacy in prevention of IFI and IRD and does not improve OS and FFS in both allogeneic HSCT and ASCT settings. Voriconazole is cost-effective regarding protection from IFI and IRD in allogeneic HSCT but not cost-effective in ASCT.

Circulating monocyte subsets in multiple myeloma patients receiving autologous stem cell transplantation - a study of the preconditioning status and the course until posttransplant reconstitution for a consecutive group of patients

BACKGROUND

Induction therapy of multiple myeloma patients prior to autologous stem cell transplantation has changed from conventional chemotherapy to treatment based on proteasome inhibitors or immunomodulatory drugs. We used flow cytometry to analyze total monocyte and monocyte subset (classical, intermediate and non-classical monocytes) peripheral blood levels before and following auto-transplantation for a consecutive group of myeloma patients who had received the presently used induction therapy.

RESULTS

The patients showed normal total monocyte concentrations after induction/stem cell mobilization, but the concentrations of classical monocytes were increased compared with healthy controls. Melphalan conditioning reduced the levels of total CD14⁺ as well as classical and non-classical monocytes, whereas intermediate monocytes were not affected. Thus, melphalan has a non-random effect on monocyte subsets. Melphalan had a stronger effect on total and classical monocyte concentrations for those patients who had received induction therapy including immunomodulatory drugs. Total monocytes and monocyte subset concentrations decreased during the period of pancytopenia, but monocyte reconstitution occurred before hematopoietic reconstitution. However, the fractions of various monocyte subsets varied considerably between patients.

CONCLUSIONS

The total level of circulating monocytes is normalized early after auto-transplantation for multiple myeloma, but pre- and post-transplant levels of various monocyte subsets show considerable variation between patients.

Profound but Transient Changes in the Inflammatory Milieu of the Blood During Autologous Hematopoietic Stem Cell Transplantation

Little is known about the inflammatory milieu in the blood during autologous hematopoietic stem cell transplantation (AHSCT) and how it is affected by the stem cell mobilization, collection, and reinfusion and conditioning regimen. In this study, we analyzed 92 proteins connected to inflammation at 10 time points during and after AHSCT in 16 patients with multiple sclerosis (MS). Serum from 29 patients with newly diagnosed MS and 15 healthy controls were included for comparative analysis. There were no significant differences in inflammatory serum protein levels between patients with newly diagnosed MS and healthy controls, but 29 out of 73 detectable proteins were significantly altered between at least 2 adjacent sampling time points during AHSCT. The predominant changes occurred after the conditioning regimen had been administered, whereas stem cell mobilization, collection, and reinfusion appeared to have less impact. Two distinct response patterns could be discerned, likely representing loss of basal cytokine production and homeostasis. The analyzed serum proteins gradually returned to baseline levels after treatment, with no remaining differences at 3 months after AHSCT. We conclude that treatment with AHSCT has a major but transient impact on the inflammatory milieu of peripheral blood.

Immune checkpoint blockade and its combination therapy with small-molecule inhibitors for cancer treatment

Initially understood for its physiological maintenance of self-tolerance, the immune checkpoint molecule has recently been recognized as a promising anti-cancer target. There has been considerable interest in the biology and the action mechanism of the immune checkpoint therapy, and their incorporation with other therapeutic regimens. Recently the small-molecule inhibitor (SMI) has been identified as an attractive combination partner for immune checkpoint inhibitors (ICIs) and is becoming a novel direction for the field of combination drug design. In this review, we provide a systematic discussion of the biology and function of major immune checkpoint molecules, and their interactions with corresponding targeting agents. With both preclinical studies and clinical trials, we especially highlight the ICI + SMI combination, with its recent advances as well as its application challenges.

A phase I clinical study of autologous dendritic cell therapy in patients with relapsed or refractory multiple myeloma

Cellular immunotherapy is emerging as a potential immunotherapeutic modality in multiple myeloma (MM). We have developed potent immunotherapeutic agent (VAX-DC/MM) generated by dendritic cells (DCs) loaded with autologous myeloma cells irradiated with ultraviolet B. In this study, we evaluated the safety and efficacy of VAX-DC/MM in patients with relapsed or refractory MM. This trial enrolled relapsed or refractory MM patients who had received both thalidomide- and bortezomib-based therapies. Patients received the intradermal VAX-DC/MM injection every week for 4 weeks. Patients were treated with 5 × 10⁶ or 10 × 10⁶ cells, with nine patients treated at a higher dose. The median time from diagnosis to VAX-DC/MM therapy was 56.6 months (range, 28.5–130.5). Patients had received a median of five prior treatments, and 75% had received autologous stem cell transplantation. VAX-DC therapy was well-tolerated, and the most frequent adverse events were local reactions at the injection site and infusion-related reactions. In seven of nine patients who received 10×10⁶ cells, an immunological response (77.8%) was observed by interferon-gamma ELISPOT assay or a mixed lymphocyte reaction assay for T-cell proliferation. The clinical benefit rate was 66.7% including one (11.1%) with minor response and five (55.6%) with stable disease; three (33.3%) patients showed disease progression. In conclusion, VAX-DC/MM therapy was well-tolerated, and had disease-stabilizing activity in heavily pretreated MM cases. Further studies are needed to increase the efficacy of VAX-DC/MM in patients with MM.

Nutritional Support from the Intestinal Microbiota Improves Hematopoietic Reconstitution after Bone Marrow Transplantation in Mice

Bone marrow transplantation (BMT) offers curative potential for patients with high-risk hematologic malignancies, but the post-transplantation period is characterized by profound immunodeficiency. Recent studies indicate that the intestinal microbiota not only regulates mucosal immunity, but can also contribute to systemic immunity and hematopoiesis. Using antibiotic-mediated microbiota depletion in a syngeneic BMT mouse model, here we describe a role for the intestinal flora in hematopoietic recovery after BMT. Depletion of the intestinal microbiota resulted in impaired recovery of lymphocyte and neutrophil counts, while recovery of the hematopoietic stem and progenitor compartments and the erythroid lineage were largely unaffected. Depletion of the intestinal microbiota also reduced dietary energy uptake and visceral fat stores. Caloric supplementation through sucrose in the drinking water improved post-BMT hematopoietic recovery in mice with a depleted intestinal flora. Taken together, we show that the intestinal microbiota contribute to post-BMT hematopoietic reconstitution in mice through improved dietary energy uptake.

Tackling Cancer Resistance by Immunotherapy: Updated Clinical Impact and Safety of PD-1/PD-L1 Inhibitors

Cancer therapy has been constantly evolving with the hope of finding the most effective agents with the least toxic effects to eradicate tumors. Cancer immunotherapy is currently among the most promising options, fulfilling this hope in a wide range of tumors. Immunotherapy aims to activate immunity to fight cancer in a very specific and targeted manner; however, some abnormal immune reactions known as immune-related adverse events (IRAEs) might occur. Therefore, many researchers are aiming to define the most proper protocols for managing these complications without interfering with the anticancer effect. One of these targeted approaches is the inhibition of the interaction between the checkpoint protein, programmed death-receptor 1 (PD-1), and its ligand, programmed death-ligand 1 (PD-L1), via a class of antibodies known as PD-1/PD-L1 inhibitors. These antibodies achieved prodigious success in a wide range of malignancies, including those where optimal treatment is not yet fully identified. In this review, we have critically explored and discussed the outcome of the latest PD-1 and PD-L1 inhibitor studies in different malignancies compared to standard chemotherapeutic alternatives with a special focus on the clinical efficacy and safety. The approval of the clinical applications of nivolumab, pembrolizumab, atezolizumab, avelumab, and durvalumab in the last few years clearly highlights the hopeful future of PD-1/PD-L1 inhibitors for cancer patients. These promising results of PD-1/PD-L1 inhibitors have encouraged many ongoing preclinical and clinical trials to explore the extent of antitumor activity, clinical efficacy and safety as well as to extend their applications.

Immune Reconstitution Following Autologous Stem Cell Transplantation in Patients with High-Risk Neuroblastoma at the Time of Immunotherapy

Outcomes for patients with high-risk neuroblastoma (HR-NBL) are significantly improved with the addition of immunotherapy (dinutuximab + cytokines) following autologous hematopoietic stem cell transplantation (auto-HSCT). We hypothesized that the immune system is not fully reconstituted at the initiation of immunotherapy. To test this hypothesis, we evaluated hematologic and immune subsets in 34 patients with HR-NBL before and after auto-HSCT. We found that absolute T, B, and NK cell counts at the time of immunotherapy were below normal in 80% of patients. Patients with residual disease at the time of transplantation had significantly lower absolute lymphocyte counts (ALC; P = .008), lower CD16⁺ cell counts (P = .009), and an abnormal ratio of cytokine-releasing to cytotoxic NK cells at the time of dinutuximab treatment. In addition, the preparative regimen used for auto-HSCT predicted immune recovery. Finally, higher total white blood cell count (P = .013) and ALC (P = .013) at 3 months after completion of therapy were measured in patients who remained in remission compared with those who relapsed. Our results indicate that most patients with HR-NBL do not have full immune reconstitution at the time of dinutuximab treatment after auto-HSCT, and that immune recovery may correlate with disease-related outcomes in patients with high-risk disease.

Stop and go: hematopoietic cell transplantation in the era of chimeric antigen receptor T cells and checkpoint inhibitors

PURPOSE OF REVIEW

For several decades, hematopoietic cell transplantation (HCT) has been considered the standard curative therapy for many patients with hematological malignancies. In addition to the cytotoxic effects of the chemotherapy and radiation used in the conditioning regimen, the benefits of HCT are derived from a reset of the immune system and harnessing the ability of donor T cells to eliminate malignant cells. With the dawn of the era of immunotherapies in the form of checkpoint inhibitors and chimeric antigen receptor (CAR) T cells, the role of HCT has evolved.

RECENT FINDINGS

Immunotherapy with checkpoint inhibitors is increasingly being used for relapsed Hodgkin and non-Hodgkin lymphoma after autologous HCT. Checkpoint inhibitors are also being tested after allogeneic HCT with observable benefits in treating hematological malignancies, but with a potential risk of increased graft versus host disease and transplant-related mortality. Immunotherapy with Cluster of differentiation 19 CAR T cells are powerful options with aggressive B-cell malignancies both for therapy and as induction leading to allogeneic HCT.

SUMMARY

Although immunotherapies with checkpoint inhibition and CAR T cells are increasingly being used to treat hematological malignancies, HCT remains a standard of care for most of the diseases with the best chance of cure. Combination of these therapies with HCT has the potential to more effectively treat hematological malignancies.

The multi-faceted potential of CD38 antibody targeting in multiple myeloma

CD38, an adenine dinucleotide phosphate (ADP) ribose cyclase and a cyclic ADP ribose hydrolase, is widely expressed on the surface of multiple myeloma (MM) cells. It is known to play a pivotal role in the downstream pathways that mediate MM cell growth, signal transduction, and adhesion. The clinical use of CD38 monoclonal antibodies (MoAbs), such as daratumumab, either as monotherapy or in combination with other anti-MM agents, has produced impressive results in patients who have failed standard MM therapy. CD38 MoAbs exhibit several cytotoxic mechanisms on MM cells. In addition to the classical effector mechanisms associated with antibody therapy, CD38 MoAbs induce MM apoptosis and clonal T-cell expansion. Here, we summarize the results of some pivotal clinical studies using a human CD38 MoAb, daratumumab, in patients with MM, discuss the anti-MM effector mechanisms induced by CD38 MoAbs, and review the potential tumor antigens that may be suitable targets for immunotherapy of MM. Finally, we present a paradigm of immunotherapy for MM patients using CD38 MoAbs followed by GM-CSF and an immune checkpoint inhibitor in patients who have undergone high dose chemotherapy and autologous stem cell transplant. CD38 MoAbs have emerged as a novel and ultimately very promising immunotherapeutic agent for MM because of its ability to induce MM cytotoxicity through both arms of the adaptive immune responses.

The role of anti-PD-1 and anti-PD-L1 agents in the treatment of diffuse large B-cell lymphoma: The future is now

Immune checkpoints inhibitors have been incorporated into standard treatment protocols for advanced solid tumors. The aim of T-cell-based immune therapy in cancer has been to generate durable clinical benefits for patients, paired with enhanced side effect profiles. The beneficial antitumoral activity of programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) has been thoroughly demonstrated in certain metastatic malignancies (e.g. melanoma, non-small cell lung cancer, renal cell carcinoma); however, the therapeutic role in lymphoid cancers is complex. Nonetheless, the striking clinical activity seen in early clinical trials of various subtypes of relapsed lymphoma have paved the way for these exciting innovative therapeutic alternatives in these tumors. In this article we assess the literature on the role of the PD-1/PD-L1 pathway in Diffuse Large B-cell lymphoma (DLBCL), and describe future strategies involving these new anticancer agents in this lymphoid neoplasm.

Targeting Immune Checkpoints in Hematologic Malignancies

The use of antibodies that target immune checkpoint molecules on the surface of T-lymphocytes and/or tumor cells has revolutionized our approach to cancer therapy. Cytotoxic-T-lymphocyte antigen (CTLA-4) and programmed cell death protein 1 (PD-1) are the two most commonly targeted immune checkpoint molecules. Although the role of antibodies that target CTLA-4 and PD-1 has been established in solid tumor malignancies and Food and Drug Administration approved for melanoma and non-small cell lung cancer, there remains a desperate need to incorporate immune checkpoint inhibition in hematologic malignancies. Unlike solid tumors, a number of considerations must be addressed to appropriately employ immune checkpoint inhibition in hematologic malignancies. For example, hematologic malignancies frequently obliterate the bone marrow and lymph nodes, which are critical immune organs that must be restored for appropriate response to immune checkpoint inhibition. On the other hand, hematologic malignancies are the quintessential immune responsive tumor type, as proven by the success of allogeneic stem cell transplantation (allo-SCT) in hematologic malignancies. Also, sharing an immune cell lineage, malignant hematologic cells often express immune checkpoint molecules that are absent in solid tumor cells, thereby offering direct targets for immune checkpoint inhibition. A number of clinical trials have demonstrated the potential for immune checkpoint inhibition in hematologic malignancies before and after allo-SCT. The ongoing clinical studies and complimentary immune correlatives are providing a growing body of knowledge regarding the role of immune checkpoint inhibition in hematologic malignancies, which will likely become part of the standard of care for hematologic malignancies.

Programmed death-1 immune checkpoint blockade in the treatment of hematological malignancies

The use of tumor-specific monoclonal antibodies (MAbs) has revolutionize the field of cancer immunotherapy. Although treatment of malignant diseases with MAbs is promising, many patients fail to respond or relapse after an initial response. Both solid tumors and hematological malignancies develop mechanisms that enable them to evade the host immune system by usurping immune checkpoint pathways such as PD-1, PD-2, PDL-1, or PDL-2 (programmed cell death protein-1 or 2 and PD-Ligand 1 or 2), which are expressed on activated T cells and on T-regulatory, B cells, natural killers, monocytes, and dendritic cells. One of the most exciting anticancer development in recent years has been the immune checkpoint blockade therapy by using MAbs against immune checkpoint receptor and/or ligands. Anti-PD1 antibodies have been tested in clinical studies that included patients with hematological malignancies and showed remarkable efficacy in Hodgkin lymphoma (HL). In our review, we will focus on the effect of PD-1 activation on hematological malignancies and its role as a therapeutic target. Key messages The programmed death 1 (PD1) immune checkpoint is an important homeostatic mechanism of the immune system that helps in preventing autoimmunity and uncontrolled inflammation in cases of chronic infections. However, PD1 pathway is also operated by a wide variety of malignancies and represents one of the most important mechanisms by which tumor cells escape from the surveillance of the immune system. Blocking of immune checkpoints by the use of monoclonal antibodies opened a new era in the field of cancer immunotherapy. Results from clinical trials are promising, and currently, this approach has been proven effective and safe in patients with solid tumors and hematological malignancies.

Mesenchymal Stromal/Stem Cells Do Not Ameliorate Experimental Autoimmune Encephalomyelitis and Are Not Detectable in the Central Nervous System of Transplanted Mice

Mesenchymal stromal/stem cells (MSCs) constitute progenitor cells that can be isolated from different tissues. Based on their immunomodulatory and neuroprotective functions, MSC-based cell-therapy approaches have been suggested to antagonize inflammatory activity and neuronal damage associated with autoimmune disease of the central nervous system (CNS), for example, multiple sclerosis (MS). Intravenous MSC transplantation was reported to ameliorate experimental autoimmune encephalomyelitis (EAE), the murine model of MS, within days after transplantation. However, systemic distribution patterns and fate of MSCs after administration, especially their potential to migrate into inflammatory lesions within the CNS, remain to be elucidated. This question has of recent become particularly important, since therapeutic infusion of MSCs is now being tested in clinical trials with MS-affected patients. Here, we made use of the established EAE mouse model to investigate migration and therapeutic efficacy of murine bone marrow-derived MSCs. Applying a variety of techniques, including magnetic resonance imaging, immunohistochemistry, fluorescence in-situ hybridization, and quantitative polymerase chain reaction we found no evidence for immediate migration of infused MSC into the CNS of treated mice. Moreover, in contrast to other studies, transplanted MSCs did not ameliorate EAE. In conclusion, our data does not provide substantiation for a relevant migration of infused MSCs into the CNS of EAE mice supporting the hypothesis that potential therapeutic efficacy could be based on systemic effects. Evaluation of possible mechanisms underlying the observed discrepancies in MSC treatment outcomes between different EAE models demands further studies.

Reprint of: Fast Cars and No Brakes: Autologous Stem Cell Transplantation as a Platform for Novel Immunotherapies

Autologous stem cell transplantation (ASCT) is indicated in a number of hematologic malignancies, including multiple myeloma, non-Hodgkin lymphoma, and Hodgkin lymphoma. Relapse, however, remains 1 of the main causes of post-ASCT failure, and several strategies are being investigated to decrease the risk of relapse of progression. Recent advances in the treatment of hematological malignancies have included adoptive transfer of genetically modified T cells that express chimeric antigen receptors or T cell receptors, as well the use of checkpoint inhibitors. Early clinical results in non-transplantation patients have been very promising. This review will focus on the use of gene-modified T cells and checkpoint inhibitors in stem cell transplantation.

Homeostatic cytokines in immune reconstitution and graft-versus-host disease

For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic SCT, acute graft-versus-host disease (aGVHD) remains the second cause of death after disease recurrence. aGVHD is highly immunosuppressive and the adverse effect of allogeneic SCT on T cell regeneration is typically more important than the levels of immunosuppression normally seen after autologous SCT. In these patients, immune reconstitution often takes several years to occur and restoring immunocompetence after allogeneic SCT represents an important challenge, principally because clinical options are limited and current methods used to accelerate immune reconstitution are associated with increased GVHD. Interleukin-7 and IL-15 are both under clinical investigation and demonstrate the greatest potential on peripheral T cells regeneration in mice and humans. However, awareness has been raised about the use of IL-7 and IL-15 after allogeneic SCT with regards to potential adverse effects on aGVHD. In this review, we will discuss about recent progress made in lymphocyte regeneration, the critical role played by IL-7 and IL-15 in T cell homeostasis and how these cytokines could be used to improve immune reconstitution after allogeneic SCT.

Phagocyte function decreases after high-dose treatment with melphalan and autologous stem cell transplantation in patients with multiple myeloma

High-dose melphalan with autologous hematopoietic stem cell transplantation (ASCT) is the standard of care for younger patients with newly diagnosed multiple myeloma and is aimed at achieving as deep and complete a response as possible after various combinations of induction therapy. However, it is frequently associated with infectious complications. This study investigated the effects of high-dose treatment with autologous stem cell support on patients' innate immunity, with a focus on subpopulations and functioning of recently released polymorphonuclear leukocytes (PMNs) and monocytes in peripheral blood. Flow cytometry-based analysis was used to measure the degree of PMN maturation and activation, before and after ASCT and compared with healthy controls. After high-dose treatment and ASCT, a smaller proportion of patients' PMNs had the capacity for oxidative burst. Moreover, patients' PMNs, both before and after ASCT, had a reduced capacity for phagocytosis. Eosinophils, which recently have been suggested to play a role in promoting malignant plasma cell proliferation, were markedly reduced after ASCT, with slow regeneration. HLA-DR expression by monocytes was significantly depressed after ASCT, a characteristic often attributed to monocytic myeloid-derived suppressor cells. Our results suggest that several aspects of phagocytic function are impaired for at least 20 days after ASCT.

Mechanisms of blood homeostasis: lineage tracking and a neutral model of cell populations in rhesus macaques

Background

How a potentially diverse population of hematopoietic stem cells (HSCs) differentiates and proliferates to supply more than 10¹¹ mature blood cells every day in humans remains a key biological question. We investigated this process by quantitatively analyzing the clonal structure of peripheral blood that is generated by a population of transplanted lentivirus-marked HSCs in myeloablated rhesus macaques. Each transplanted HSC generates a clonal lineage of cells in the peripheral blood that is then detected and quantified through deep sequencing of the viral vector integration sites (VIS) common within each lineage. This approach allowed us to observe, over a period of 4-12 years, hundreds of distinct clonal lineages.

Results

While the distinct clone sizes varied by three orders of magnitude, we found that collectively, they form a steady-state clone size-distribution with a distinctive shape. Steady-state solutions of our model show that the predicted clone size-distribution is sensitive to only two combinations of parameters. By fitting the measured clone size-distributions to our mechanistic model, we estimate both the effective HSC differentiation rate and the number of active HSCs.

Conclusions

Our concise mathematical model shows how slow HSC differentiation followed by fast progenitor growth can be responsible for the observed broad clone size-distribution. Although all cells are assumed to be statistically identical, analogous to a neutral theory for the different clone lineages, our mathematical approach captures the intrinsic variability in the times to HSC differentiation after transplantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-015-0191-8) contains supplementary material, which is available to authorized users.

Fast Cars and No Brakes: Autologous Stem Cell Transplantation as a Platform for Novel Immunotherapies

Autologous stem cell transplantation (ASCT) is indicated in a number of hematologic malignancies, including multiple myeloma, non-Hodgkin lymphoma, and Hodgkin lymphoma. Relapse, however, remains 1 of the main causes of post-ASCT failure, and several strategies are being investigated to decrease the risk of relapse of progression. Recent advances in the treatment of hematological malignancies have included adoptive transfer of genetically modified T cells that express chimeric antigen receptors or T cell receptors, as well the use of checkpoint inhibitors. Early clinical results in nontransplantation patients have been very promising. This review will focus on the use of gene-modified T cells and checkpoint inhibitors in stem cell transplantation.

Immune Reconstitution after Allogeneic Hematopoietic Cell Transplantation in Children

Allogeneic (allo) hematopoietic cell transplantation (HCT) has evolved into a potent curative treatment option for a variety of malignant and nonmalignant diseases. The occurrence of complications and mortality after allo-HCT is, however, still high and is strongly associated with immune reconstitution (IR). Therefore, detailed information on IR through immunomonitoring is crucial to improve survival chances after HCT. To date, information about the reconstituting immune system after allo-HCT in pediatric patients is mostly derived from routine standard-of-care measurements. More profound knowledge on IR may provide tools to better predict and modulate adverse reactions and, subsequently, improve survival chances. Here, we provide an overview of IR (eg, immune cell subsets and circulating chemokines/cytokines) after allo-HCT in children, taking into account different cell sources and serotherapy, and discuss strategies to enhance immunomonitoring. We conclude that available IR data after allo-HCT contain limited information on immune cell families (mostly only generic T, B, and NK cells), which would improve with more detailed information on reconstituting cell subsets or effector cell functionality at earlier time points (<1 month). In addition, secretome data (eg, multiplex cytokine/chemokine profiles) could add to the understanding of IR mechanisms and cell functionality and may even provide (early) biomarkers for individual disease outcome, such as viral reactivity, graft-versus-host disease, or graft-versus-leukemia. The present data and suggestions for more detailed, standardized, and harmonized immunomonitoring in future (pediatric) allo-HCT studies will pave the path to "precision transplantation:" an individualized HCT approach (including conditioning), based on detailed information on IR and biomarkers, aiming to reduce transplantation related mortality and relapse, and subsequently improve survival chances.

Idiotypic DNA vaccination for the treatment of multiple myeloma: safety and immunogenicity in a phase I clinical study

We report on the safety and immunogenicity of idiotypic DNA vaccination in a phase I, non-randomised, open-label study in patients with multiple myeloma. The study used DNA fusion gene vaccines encoding patient-specific single chain variable fragment, or idiotype (Id), linked to fragment C (FrC) of tetanus toxin. Patients in complete or partial response following high-dose chemotherapy and autologous stem cell transplant were vaccinated intramuscularly with 1 mg DNA on six occasions, beginning at least 6 months post-transplant; follow-up was to week 52. Fourteen patients were enrolled on study and completed vaccinations. Idiotypic DNA vaccines were well tolerated with vaccine-related adverse events limited to low-grade constitutional symptoms. FrC- and Id-specific T-cell responses were detected by ex vivo ELISPOT in 9/14 and 3/14 patients, respectively. A boost of pre-existing anti-FrC antibody (Ab) was detected by ELISA in 8/14 patients, whilst anti-Id Ab was generated in 1/13 patients. Overall, four patients (29 %) made an immune response to FrC and Id, with six patients (43 %) responding to FrC alone. Over the 52-week study period, serum paraprotein was undetectable, decreased or remained stable for ten patients (71 %), whilst ongoing CR/PR was maintained for 11 patients (79 %). The median time to progression was 38.0 months for 13/14 patients. Overall survival was 64 % after a median follow-up of 85.6 months.

Immune checkpoint blockade in hematologic malignancies

Therapeutic blockade of immune checkpoint pathways, in particular cytotoxic T-lymphocyte associated protein 4 and programmed-death 1 (PD-1), has become a paradigm-shifting treatment in solid tumor oncology. Hematologic malignancies (HMs), many of which are known to have clinically exploitable immune sensitivity, are a natural target for this type of treatment. Several clinical trials of checkpoint blockade have been conducted in HM, with preliminary results suggesting the therapeutic usefulness of this approach across several tumor types. In particular, the results of PD-1 blockade in Hodgkin lymphoma (HL) are remarkable, and raise hope that it may alter the treatment landscape in this disease. However, numerous questions remain about the optimal role of checkpoint blockade both in HL and beyond. Those questions are the focus of this review, in the hope that, if we are at the dawn of a new day in HM immunotherapy, we may begin to envision its morning.

Beyond consolidation: auto-SCT and immunotherapy for plasma cell myeloma

Autologous hematopoietic cell transplantation (auto-HCT) is the standard consolidation therapy for plasma cell myeloma patients following induction therapy. Auto-HCT improves disease-free survival (DFS), but is generally not curative. The allogeneic HCT experience demonstrated that T-cell immunotherapy can confer long-term DFS. Preclinical and clinical data indicate that myeloma-associated Ags elicit humoral and cellular immune responses (IRs) in myeloma patients. These findings strongly suggest that the immunotherapeutic strategies, including immune checkpoint inhibitors, therapeutic cancer vaccines and adoptive cellular therapies, are promising avenues of clinical research that may be most applicable in the minimal residual disease state following auto-HCT. These strategies are designed to prime or augment antimyeloma IRs and promote a 'host-vs-myeloma' effect that may result in durable DFS. Innovative clinical trials investigating immune checkpoint inhibitors and cancer vaccines have demonstrated that robust immunity against myeloma-associated Ags can be elicited in the setting of auto-HCT. A diverse array of immunotherapeutic strategies have entered clinical trials in myeloma, including PD-1/PD-L1 inhibitors, DC/myeloma cell fusion vaccines and adoptive chimeric Ag receptor T-cell therapy, and further investigation of combinations of immunologic and pharmaceutical agents are expected in the near future. In this review, we will discuss the preclinical data supporting immunotherapy in auto-HCT for myeloma, clinical investigation of these strategies and the future prospects of immunotherapy in pursuit of the goal of curative therapy.

Alkylating agent melphalan augments the efficacy of adoptive immunotherapy using tumor-specific CD4+ T cells

In recent years, the immune-potentiating effects of some widely used chemotherapeutic agents have been increasingly appreciated. This provides a rationale for combining conventional chemotherapy with immunotherapy strategies to achieve durable therapeutic benefits. Previous studies have implicated the immunomodulatory effects of melphalan, an alkylating agent commonly used to treat multiple myeloma, but the underlying mechanisms remain obscure. In the present study, we investigated the impact of melphalan on endogenous immune cells as well as adoptively transferred tumor-specific CD4(+) T cells in tumor-bearing mice. We showed that melphalan treatment resulted in a rapid burst of inflammatory cytokines and chemokines during the cellular recovery phase after melphalan-induced myelodepletion and leukodepletion. After melphalan treatment, tumor cells exhibited characteristics of immunogenic cell death, including membrane translocation of the endoplasmic reticulum-resident calreticulin and extracellular release of high-mobility group box 1. Additionally, there was enhanced tumor Ag uptake by dendritic cells in the tumor-draining lymph node. Consistent with these immunomodulatory effects, melphalan treatment of tumor-bearing mice led to the activation of the endogenous CD8(+) T cells and, more importantly, effectively drove the clonal expansion and effector differentiation of adoptively transferred tumor-specific CD4(+) T cells. Notably, the combination of melphalan and CD4(+) T cell adoptive cell therapy was more efficacious than either treatment alone in prolonging the survival of mice with advanced B cell lymphomas or colorectal tumors. These findings provide mechanistic insights into melphalan's immunostimulatory effects and demonstrate the therapeutic potential of combining melphalan with adoptive cell therapy utilizing antitumor CD4(+) T cells.