Impact of lymphocyte and monocyte recovery on the outcomes of allogeneic hematopoietic SCT with fludarabine and melphalan conditioning

Risk factors of early disease progression and decreased survival for multiple myeloma patients after upfront autologous stem cell transplantation

Multiple myeloma (MM) stands as the second most prevalent hematological malignancy, constituting approximately 10% of all hematological malignancies. Current guidelines recommend upfront autologous stem cell transplantation (ASCT) for transplant-eligible MM patients. This study seeks to delineate factors influencing post-ASCT outcomes in MM patients. Our cohort comprised 150 MM patients from Taipei Veterans General Hospital, with progression-free survival (PFS) as the primary endpoint and overall survival (OS) as the secondary endpoint. A Cox proportional hazards model was employed to discern potential predictive factors for survival. ASCT age ≥ 65 (hazard ratio [HR] 1.94, 95% confidence interval [CI] 1.08-3.47) and the presence of extramedullary disease (HR 2.53, 95% CI 1.53-4.19) negatively impacted PFS. Conversely, treatment response ≥ VGPR before ASCT (HR 0.52, 95% CI 0.31-0.87) and total CD34+ cells collected ≥ 4 × 106 cells/kg on the first stem cell harvesting (HR 0.52, 95% CI 0.32-0.87) were positively associated with PFS. For OS, patients with ISS stage III (HR 2.06, 95% CI 1.05-4.04), the presence of extramedullary disease (HR 3.92, 95% CI 2.03-7.58), light chain ratio ≥ 100 before ASCT (HR 7.08, 95% CI 1.45-34.59), post-ASCT cytomegalovirus infection (HR 9.43, 95% CI 3.09-28.84), and a lower conditioning melphalan dose (< 140 mg/m2; HR 2.75, 95% CI 1.23-6.17) experienced shorter OS. In contrast, post-ASCT day + 15 absolute monocyte counts (D15 AMC) > 500/µl (HR 0.36, 95% CI 0.17-0.79) and post-ASCT day + 15 platelet counts (D15 PLT) > 80,000/µl (HR 0.48, 95% CI 0.24-0.94) were correlated with improved OS. Significantly, early PLT and AMC recovery on day + 15 predicting longer OS represents a novel finding not previously reported. Other factors also align with previous studies. Our study provides real-world insights for post-ASCT outcome prediction beyond clinical trials.

Early reversal of the lymphocyte-to-monocyte ratio after allogeneic-hematopoietic stem cell transplantation is associated with reduced relapse and improved prognosis

BACKGROUND

The early recovery of lymphocyte and monocyte cells is associated with a favorable prognosis after allogeneic stem cell transplantation (allo-HSCT); however, it is not clear whether the balance of lymphocyte and monocyte recovery affects the post-transplant prognosis.

METHODS

We examined whether the time-point at which the number of lymphocytes exceeded the number of monocytes, which we termed lymphocyte-to-monocyte ratio reversal (LMRR), affected the prognosis after allo-HSCT. We retrospectively evaluated 235 patients who underwent their first allo-HSCT at our institution.

RESULTS

The median number of days from HSCT to LMRR was 46 (range, 0-214), and the patients were divided into two groups according to the occurrence of LMRR by day 45 (LMRR45). In a multivariate analysis, early LMRR contributed favorably to overall survival (hazard ratio [HR] .519; 95% confidence interval [CI] .332-.812; p = .004) with fewer post-transplant relapses (HR .462; 95% CI, .274-.777; p = .004). Differences in the timing of LMRR did not affect non-relapse mortality (HR 1.477; 95% CI .779-2.80; p = .23) or the incidence of grade II-IV acute GVHD (LMRR45(+): 25.0% vs. LMRR45(-) 35.2%. p = .111). In subgroup analyses, LMRR45(+) was found to be a favorable factor for survival with less relapse, regardless of the disease risk, stem cell source, or the recovery of either lymphocyte or monocyte counts.

CONCLUSIONS

An early LMRR may be a novel factor that is associated with reduced relapse and improved survival after allo-HSCT.

Immune Reconstitution of Patients Who Recovered From Steroid-Refractory Acute Graft-Versus-Host Disease After Basiliximab Treatment

We aimed to identify the characteristics of immune reconstitution (IR) in patients who recovered from steroid-refractory acute graft-versus-host disease (SR-aGVHD) after basiliximab treatment. A total of 179, 124, 80, and 92 patients were included in the analysis for IR at 3, 6, 9, and 12 months, respectively, after haploidentical donor hematopoietic stem cell transplantation (HID HSCT). We observed that IR was fastest for monocytes and CD8⁺ T cells, followed by lymphocytes, CD3⁺ T cells, and CD19⁺ B cells and slowest for CD4⁺ T cells. Almost all immune cell subsets recovered comparably between patients receiving <5 doses and ≥5 doses of basiliximab. Most immune cell subsets recovered comparably between SR-aGVHD patients who recovered after basiliximab treatment and event-free HID HSCT recipients. Patients who recovered from SR-aGVHD after basiliximab treatment experienced satisfactory IR, which suggested that basiliximab may not have prolonged the negative impact on IR in these patients.

Normal Absolute Monocyte Count in Combination with Normal/High Absolute Lymphocyte Count at the Time of Relapse is Associated with Improved Survival in Patients with Early Relapsed Acute Myeloid Leukemia

This study aimed to examine the prognostic significance of peripheral absolute monocyte count (AMC) in combination with absolute lymphocyte count (ALC) at the time of relapse in a cohort of 57 patients with early relapsed (first complete remission <12 months) acute myeloid leukemia (AML). Both univariate and multivariate Cox proportional hazard regression analyses revealed that normal AMC in combination with normal/high ALC (versus low/high AMC in combination with low ALC) was significantly associated with improved OS. We concluded that the combination of AMC and ALC could be used as a prognostic marker for survival outcomes in early relapsed AML.

Associations between the Gut Microbiota, Immune Reconstitution, and Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation

Immune reconstitution following allogeneic hematopoietic stem cell transplantation (allo-HSCT) sets the stage for the goal of a successful transplant—the prevention of disease relapse without graft versus host disease (GVHD) and opportunistic infection. In both epidemiologic studies and in controlled animal studies, it is known that the gut microbiome (GM) can profoundly influence normal innate and adaptive immune development and can be altered by microbial transfer and antibiotics. Following allo-HSCT the GM has been shown to influence clinical outcomes but published associations between the GM and immune reconstitution post-allo-HSCT are lacking. In this viewpoint we propose that the extensive knowledge garnered from studying normal immune development can serve as a framework for studying immune development post-allo-HSCT. We summarize existing studies addressing the effect of the GM on immune ontogeny and draw associations with immune reconstitution and the GM post-allo-HSCT.

Monocyte Reconstitution and Gut Microbiota Composition after Hematopoietic Stem Cell Transplantation

BACKGROUND

Monocytes are an essential cellular component of the innate immune system that support the host's effectiveness to combat a range of infectious pathogens. Hemopoietic cell transplantation (HCT) results in transient monocyte depletion, but the factors that regulate recovery of monocyte populations are not fully understood. In this study, we investigated whether the composition of the gastrointestinal microbiota is associated with the recovery of monocyte homeostasis after HCT.

METHODS

We performed a single-center, prospective, pilot study of 18 recipients of either autologous or allogeneic HCT. Serial blood and stool samples were collected from each patient during their HCT hospitalization. Analysis of the gut microbiota was done using 16S rRNA gene sequencing, and flow cytometric analysis was used to characterize the phenotypic composition of monocyte populations.

RESULTS

Dynamic fluctuations in monocyte reconstitution occurred after HCT, and large differences were observed in monocyte frequency among patients over time. Recovery of absolute monocyte counts and subsets showed significant variability across the heterogeneous transplant types and conditioning intensities; no relationship to the microbiota composition was observed in this small cohort.

CONCLUSION

In this pilot study, a relationship between the microbiota composition and monocyte homeostasis could not be firmly established. However, we identify multivariate associations between clinical factors and monocyte reconstitution post-HCT. Our findings encourage further longitudinal surveillance of the intestinal microbiome and its link to immune reconstitution.

Normal Absolute Monocyte Count at the Time of Relapse is Associated with Improved Survival After First Salvage Therapy in Adult Patients with Early Relapsed B-Lineage Acute Lymphoblastic Leukemia

Background

Peripheral monocytes, a key cell type for innate immunity, have been shown to be associated with survival in various types of hematological malignancies. However, no previous studies regarding the prognostic impact of peripheral absolute monocyte count (AMC) in early relapsed B-lineage acute lymphoblastic leukemia (B-ALL) have been reported.

Methods

Forty-nine cases of early relapsed adult B-ALL were reviewed. The upper (0.80 × 10⁹/L) and lower limits (0.12 × 10⁹/L) of the normal value for AMC were used as cut-off points. Kaplan–Meier curves and Log rank test were used for comparison of overall survival (OS). The univariate and multivariate Cox proportional hazards models were used for investigating the factors associated with OS.

Results

More than half (59.2%) of all patients showed a normal AMC (0.12–0.80 × 10⁹/L). The median follow-up was 5.3 months from the start of first salvage therapy. Univariate analysis revealed that normal AMC (versus low/high AMC) at the time of relapse was a prognostic factor for improved OS (P = 0.021). On multivariate analysis, normal AMC (versus low/high AMC) at the time of relapse remained an independent prognostic factor for improved OS (hazard ratio = 0.43, P = 0.030).

Conclusion

AMC at the time of relapse, which can be easily derived from routine clinical laboratory testing of complete blood count, might be used as a prognostic marker for survival outcomes in adult patients with early relapsed B-ALL.

1,25-dihydroxyvitamin-D3 but not the clinically applied marker 25-hydroxyvitamin-D3 predicts survival after stem cell transplantation

The serum level of 25-hydroxyvitamin-D3 is accepted as marker for a person’s vitamin D status but its role for the outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is controversially discussed. The impact of 1,25-dihydroxyvitamin-D3 on HSCT outcome, however, has never been studied. In a discovery cohort of 143 HSCT patients we repeatedly (day −16 to 100) measured 1,25-dihydroxyvitamin-D3 and in comparison the well-established marker for serum vitamin D status 25-hydroxyvitamin-D3. Only lower 1,25-dihydroxyvitamin-D3 levels around HSCT (day −2 to 7, peritransplant) were significantly associated with higher 1-year treatment-related mortality (TRM) risk (Mann–Whitney U test, P = 0.001). This was confirmed by Cox-model regression without and with adjustment for baseline risk factors and severe acute Graft-versus-Host disease (aGvHD; unadjusted P = 0.001, adjusted P = 0.005). The optimal threshold for 1,25-dihydroxyvitamin-D3 to identify patients at high risk was 139.5 pM. Also in three replication cohorts consisting of altogether 365 patients 1,25-dihydroxyvitamin-D3 levels below 139.5 pM had a 3.3-fold increased risk of TRM independent of severe aGvHD compared to patients above 139.5 pM (Cox-model unadjusted P < 0.0005, adjusted P = 0.001). Our data highlight peritransplant 1,25-dihydroxyvitamin-D3 levels but not the commonly monitored 25-hydroxyvitamin-D3 levels as potent predictor of 1-year TRM and suggest to monitor both vitamin D metabolites in HSCT patients.

Key Aspects of the Immunobiology of Haploidentical Hematopoietic Cell Transplantation

Hematopoietic stem cell transplantation from a haploidentical donor is increasingly used and has become a standard donor option for patients lacking an appropriately matched sibling or unrelated donor. Historically, prohibitive immunological barriers resulting from the high degree of HLA-mismatch included graft-vs.-host disease (GVHD) and graft failure. These were overcome with increasingly sophisticated strategies to manipulate the sensitive balance between donor and recipient immune cells. Three different approaches are currently in clinical use: (a) ex vivo T-cell depletion resulting in grafts with defined immune cell content (b) extensive immunosuppression with a T-cell replete graft consisting of G-CSF primed bone marrow and PBSC (GIAC) (c) T-cell replete grafts with post-transplant cyclophosphamide (PTCy). Intriguing studies have recently elucidated the immunologic mechanisms by which PTCy prevents GVHD. Each approach uniquely affects post-transplant immune reconstitution which is critical for the control of post-transplant infections and relapse. NK-cells play a key role in haplo-HCT since they do not mediate GVHD but can successfully mediate a graft-vs.-leukemia effect. This effect is in part regulated by KIR receptors that inhibit NK cell cytotoxic function when binding to the appropriate HLA-class I ligands. In the context of an HLA-class I mismatch in haplo-HCT, lack of inhibition can contribute to NK-cell alloreactivity leading to enhanced anti-leukemic effect. Emerging work reveals immune evasion phenomena such as copy-neutral loss of heterozygosity of the incompatible HLA alleles as one of the major mechanisms of relapse. Relapse and infectious complications remain the leading causes impacting overall survival and are central to scientific advances seeking to improve haplo-HCT. Given that haploidentical donors can typically be readily approached to collect additional stem- or immune cells for the recipient, haplo-HCT represents a unique platform for cell- and immune-based therapies aimed at further reducing relapse and infections. The rapid advancements in our understanding of the immunobiology of haplo-HCT are therefore poised to lead to iterative innovations resulting in further improvement of outcomes with this compelling transplant modality.

National Institutes of Health-Defined Chronic Graft-vs.-Host Disease in Pediatric Hematopoietic Stem Cell Transplantation Patients Correlates With Parameters of Long-Term Immune Reconstitution

Recent data revealed the importance of immune reconstitution (IR) for the evaluation of possible biomarkers in National Institutes of Health (NIH)–defined chronic graft-vs.-host disease (cGVHD) and its clinical aspects. In this large pediatric study (n = 146), we have analyzed whether cellular and humoral parameters of IR in the long-term follow-up (FU) with a special emphasis on B-cell reconstitution correlate with NIH-defined cGVHD criteria. HYPOTHESIS: we were especially interested in whether meaningful cGVHD biomarkers could be defined in a large pediatric cohort. We here demonstrate for the first time in a highly homogenous pediatric patient cohort that both cGVHD (n = 38) and its activity were associated with the perturbation of the B-cell compartment, including low frequencies of CD19⁺CD27⁺ memory B-cells and increased frequencies of circulating CD19⁺CD21^low B-cells, a well-known hyperactivated B-cell subset frequently found elevated in chronic infection and autoimmunity. Notably, resolution of cGVHD correlated with expansion of CD19⁺CD27⁺ memory B-cells and normalization of CD19⁺CD21^low B-cell frequencies. Moreover, we found that the severity of cGVHD had an impact on parameters of IR and that severe cGVHD was associated with increased CD19⁺CD21^low B-cell frequencies. When comparing the clinical characteristics of the active and non-active cGVHD patients (in detail at time of analyses), we found a correlation between activity and a higher overall severity of cGVHD, which means that in the active cGVHD patient group were more patients with a higher disease burden of cGVHD—despite similar risk profiles for cGVHD. Our data also provide solid evidence that the time point of analysis regarding both hematopoietic stem cell transplantation (HSCT) FU and cGVHD disease activity may be of critical importance for the detailed investigation of pediatric cohorts. Finally, we have proven that the differences in risk factors and patterns of IR, with cGVHD as its main confounding factor, between malignant and non-malignant diseases, are important to be considered in future studies aiming at identification of novel biomarkers for cGVHD.

Monocyte Subpopulation Recovery as Predictors of Hematopoietic Cell Transplantation Outcomes

Monocyte recovery after hematopoietic cell transplantation (HCT) has been correlated with overall survival (OS). However, monocytes are heterogeneous and consist of classic (CD14⁺⁺CD16^-), intermediate (CD14⁺CD16⁺), and nonclassic (CD14⁺CD16⁺⁺) subpopulations, with unique functional properties. We hypothesized that monocyte subpopulation reconstitution would vary based on allogeneic stem cell source and would be associated with outcomes. We studied monocyte subpopulation recovery at days 28, 60, 100, 180, and 365 post-HCT among 202 patients with hematologic malignancy. Significant differences in absolute monocyte count (AMC) and monocyte subpopulation counts at days 60 and 100 were identified based on stem cell source (all P < .01), with more robust recovery in umbilical cord blood (UCB) recipients. Using 2-fold cross-validation, optimal cutpoints were calculated for day 28 AMC and monocyte subpopulations based on OS. These were used to calculate hazard ratios for OS, disease-free survival (DFS), relapse, transplant-related mortality (TRM), and acute and chronic graft-versus-host disease. OS and DFS were superior when AMC and classic monocyte recovery were above optimal cutpoints (all P < .03). Relapse was reduced for those with AMC (P < .01) and classic (P = .05) monocyte counts above optimal cutpoints. TRM was also reduced when classic (P = .02) monocyte count exceeded optimal cutpoints. Intermediate and nonclassic monocyte recovery were not associated with outcomes. In summary, hematopoietic cell source is associated with monocyte subpopulation recovery, with the early robust recovery in UCB recipients. Recovery of AMC and classic monocytes were prognostic for survival, relapse, and TRM. These indicators may identify patients at increased risk for post-HCT failure and guide therapeutic interventions.

Early CD8+-recovery independently predicts low probability of disease relapse but also associates with severe GVHD after allogeneic HSCT

In this single-center study we retrospectively evaluated the impact of early reconstitution of different lymphocyte subsets on patient outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We found that CD8+ T-cell counts exceeding 50x10(6)/l as early as on day 28 post-transplantation correlated significantly with decreased relapse risk, with three-year relapse rates of 17.0% and 55.6% (P = 0.002), but were also associated with severe acute and chronic GVHD. Incidence of grade III-IV acute GVHD was 30.5% for those with early CD8+ T-cell recovery compared to 2.1% for those with lower CD8+ T-cell counts on day 28 post-transplant (HR = 20.24, P = 0.004). Early CD8+ T-cell reconstitution did not, however, affect the overall survival. Multivariate analysis showed that slow CD8+ T-cell reconstitution was strongly associated with increased risk of relapse (HR = 3.44, P = 0.026). A weaker correlation was found between CD4+ reconstitution and relapse-risk, but there was no such association with CD19+ B-cells or NK-cells. In conclusion, the early CD8+ T-cell recovery on day 28 post-transplant is associated with the lower risk of relapse but also predicts the impending severe GVHD, and thus could be useful in guiding timely treatment decisions.

Inherited CARD9 Deficiency: Invasive Disease Caused by Ascomycete Fungi in Previously Healthy Children and Adults

Autosomal recessive CARD9 deficiency underlies life-threatening, invasive fungal infections in otherwise healthy individuals normally resistant to other infectious agents. In less than 10 years, 58 patients from 39 kindreds have been reported in 14 countries from four continents. The patients are homozygous (n = 49; 31 kindreds) or compound heterozygous (n = 9; 8 kindreds) for 22 different CARD9 mutations. Six mutations are recurrent, probably due to founder effects. Paradoxically, none of the mutant alleles has been experimentally demonstrated to be loss-of-function. CARD9 is expressed principally in myeloid cells, downstream from C-type lectin receptors that can recognize fungal components. Patients with CARD9 deficiency present impaired cytokine and chemokine production by macrophages, dendritic cells, and peripheral blood mononuclear cells and defective killing of some fungi by neutrophils in vitro. Neutrophil recruitment to sites of infection is impaired in vivo. The proportion of Th17 cells is low in most, but not all, patients tested. Up to 52 patients suffering from invasive fungal diseases (IFD) have been reported, with ages at onset of 3.5 to 52 years. Twenty of these patients also displayed superficial fungal infections. Six patients had only mucocutaneous candidiasis or superficial dermatophytosis at their last follow-up visit, at the age of 19 to 50 years. Remarkably, for 50 of the 52 patients with IFD, a single fungus was involved; only two patients had IFDs due to two different fungi. IFD recurred in 44 of 45 patients who responded to treatment, and a different fungal infection occurred in the remaining patient. Ten patients died from IFD, between the ages of 12 and 39 years, whereas another patient died at the age of 91 years, from an unrelated cause. At the most recent scheduled follow-up visit, 81% of the patients were still alive and aged from 6.5 to 75 years. Strikingly, all the causal fungi belonged to the phylum Ascomycota: commensal Candida and saprophytic Trychophyton, Aspergillus, Phialophora, Exophiala, Corynesprora, Aureobasidium, and Ochroconis. Human CARD9 is essential for protective systemic immunity to a subset of fungi from this phylum but seems to be otherwise redundant. Previously healthy patients with unexplained invasive fungal infection, at any age, should be tested for inherited CARD9 deficiency.

KEY POINTS

• Inherited CARD9 deficiency (OMIM #212050) is an AR PID due to mutations that may be present in a homozygous or compound heterozygous state. • CARD9 is expressed principally in myeloid cells and transduces signals downstream from CLR activation by fungal ligands. • Endogenous mutant CARD9 levels differ between alleles (from full-length normal protein to an absence of normal protein). • The functional impacts of CARD9 mutations involve impaired cytokine production in response to fungal ligands, impaired neutrophil killing and/or recruitment to infection sites, and defects of Th17 immunity. • The key clinical manifestations in patients are fungal infections, including CMC, invasive (in the CNS in particular) Candida infections, extensive/deep dermatophytosis, subcutaneous and invasive phaeohyphomycosis, and extrapulmonary aspergillosis. • The clinical penetrance of CARD9 deficiency is complete, but penetrance is incomplete for each of the fungi concerned. • Age at onset is highly heterogeneous, ranging from childhood to adulthood for the same fungal disease. • All patients with unexplained IFD should be tested for CARD9 mutations. Familial screening and genetic counseling should be proposed. • The treatment of patients with CARD9 mutations is empirical and based on antifungal therapies and the surgical removal of fungal masses. Patients with persistent/relapsing Candida infections of the CNS could be considered for adjuvant GM-CSF/G-CSF therapy. The potential value of HSCT for CARD9-deficient patients remains unclear.

Effect of absolute monocyte count post-transplant on the outcome of patients with acute myeloid leukemia undergoing myeloablative allogeneic hematopoietic stem cell transplant with busulfan and cyclophosphamide conditioning

Peripheral monocytes have recently been evaluated as a prognostic factor in different types of hematological malignancies. This study assessed the prognostic value of absolute monocyte count (AMC) post-transplant on the clinical outcomes of 59 patients with acute myeloid leukemia (AML) who had undergone myeloablative conditioning (MAC) allogeneic hematopoietic stem cell transplant (allo-HSCT) with busulfan and cyclophosphamide (Bu/Cy). Kaplan-Meier analysis showed that patients with a high AMC (≥ 0.57 × 10⁹/L) on post-transplant day (PTD) 15 had a significantly worse overall survival (OS) compared to patients with a low AMC (< 0.57 × 10⁹/L) on PTD 15 (P = .0049). Univariate Cox proportional hazard analyses revealed that only high AMC on PTD 15 was a poor prognostic factor for OS (P = .008) and post-relapse survival (P = .030). We conclude that AMC ≥ 0.57 × 10⁹/L on PTD 15 is associated with more deaths in patients with AML who have undergone MAC allo-HSCT with Bu/Cy.

Early lymphocyte recovery predicts clinical outcome after HSCT with mycophenolate mofetil prophylaxis in the Japanese population

Immune reconstitution affects clinical outcomes after allogeneic hematopoietic stem cell transplantation (HSCT), and it has been suggested that lymphocyte recovery affects survival after HSCT. However, few studies have examined lymphocyte recovery in Asian patients who received mycophenolate mofetil (MMF) prophylaxis for graft-versus-host disease. We retrospectively evaluated early lymphocyte recovery after HSCT among Japanese adults who received MMF prophylaxis. Patients were divided into two groups according to their median absolute lymphocyte count (ALC) on day 28 after HSCT as follows: the "low ALC group" (≤ 0.22 × 10⁹ cells/L) and the "high ALC group" (> 0.22 × 10⁹ cells/L). With a median follow-up of 317 days, the high ALC group showed significantly better overall survival than the low ALC group (at 1 year: 62 vs. 46%, P = 0.02). The high ALC group also tended to have better non-relapse mortality than the low ALC group (at 1 year: 13 vs. 23%, P = 0.08). There was no significant difference in relapse rate between the high and low ALC groups (at 1 year: 29 vs. 35%, P = 0.2). We conclude that among Japanese patients who received MMF prophylaxis, ALC on day 28 after HSCT was effective in predicting overall survival and non-relapse mortality.

Characterization of innate immune viral sensors in patients following allogeneic hematopoietic stem cell transplantation

Viral infection is a major cause of morbidity and mortality following allogeneic hematopoietic stem cell transplant (HSCT), with up to one in four deaths directly linked to viral disease. Whilst awaiting lymphocyte reconstitution post-HSCT, the innate antiviral immune response is the first line of defense against invading viruses. Several novel innate viral-sensing pathways have recently been characterized, but their physiological importance in humans is poorly understood. We analyzed a panel of innate viral-sensor genes in HSCT patients, and assessed whether differences in innate antiviral responses could account for variation in susceptibility to viral infections. Expression levels of innate viral sensors in HSCT patients with active viral infections, HSCT patients without active infections and healthy volunteers were highly homogenous. Although IFN-α expression was up-regulated in actively infected patients relative to controls, a corresponding up-regulation of innate viral sensor expression was not observed. IFN-α stimulation of patient PBMCs in vitro showed intact IFN-α signaling, but actively infected patients' PBMCs had reduced up-regulation of innate viral sensors. We show that the aberrant IFN-α responses in HSCT patients were not due to calcineurin inhibition. Our data therefore raises the possibility of an intrinsic defect in innate viral sensor up-regulation in HSCT patients following viral infection.

T Cell Depletion as an Alternative Approach for Patients 55 Years or Older Undergoing Allogeneic Stem Cell Transplantation as Curative Therapy for Hematologic Malignancies

T cell-depleted (TCD) allogeneic hematopoietic stem cell transplantation (HSCT) is curative treatment for hematologic malignancies in adults, shown to reduce graft-versus-host disease (GVHD) without increased relapse. We retrospectively reviewed a single-center, 11-year experience of 214 patients aged ≥ 55 years to determine tolerability and efficacy in the older adult. Most patients (70%) had myeloid diseases, and most acute leukemias were in remission. Median age was 61 years, with related and unrelated donors ≥8/10 HLA matched. Hematopoietic cell transplantation-specific comorbidity index scores were intermediate and high for 84%. Conditioning regimens were all myeloablative. Grafts were peripheral blood stem cells (97%) containing CD3 dose ≤103-4/kg body weight, without pharmacologic GVHD prophylaxis. With median follow-up of 70 months among survivors, Kaplan-Meier estimates of overall and relapse-free survival were 44% and 41%, respectively (4 years). Cumulative incidence of nonrelapse mortality at day +100 was only 10%. Incidence of GVHD for acute (grades II to IV) was 9% at day +100 and for chronic was 7% at 2 and 4 years (8 extensive, 1 overlap). Median Karnofsky performance status for patients > 2 years post-transplant was 90%. As 1 of the largest reports for patients ≥2 aged ≥55 years receiving TCD HSCTs, it demonstrates curative therapy with minimal GVHD, similar to that observed in a younger population.

Comparison of reference values for immune recovery between event-free patients receiving haploidentical allografts and those receiving human leukocyte antigen-matched sibling donor allografts

To establish optimal reference values for recovered immune cell subsets, we prospectively investigated post-transplant immune reconstitution (IR) in 144 patients who received allogeneic stem cell transplantation (allo- SCT) and without showing any of the following events: poor graft function, grades II‒IV acute graft-versus-host disease (GVHD), serious chronic GVHD, serious bacterial infection, invasive fungal infection, or relapse or death in the first year after transplantation. IR was rapid in monocytes, intermediate in lymphocytes, CD3⁺ Tcells, CD8⁺ T cells, and CD19⁺ B cells, and very slow in CD4⁺ T cells in the entire patient cohort. Immune recovery was generally faster under HLA-matched sibling donor transplantation than under haploidentical transplantation. Results suggest that patients with an IR comparable to the reference values display superior survival, and the levels of recovery in immune cells need not reach those in healthy donor in the first year after transplantation.We suggest that data from this recipient cohort should be used as reference values for post-transplant immune cell counts in patients receiving HSCT.

Lymphocyte recovery is an independent predictor of relapse in allogeneic hematopoietic cell transplantation recipients for acute leukemia

AIM

To examine the optimal absolute lymphocyte count (ALC) cut-off utilizing receiver operator characteristics (ROC) in addition to graft characteristics associated with early ALC recovery.

METHODS

Patients who received T-cell replete peripheral hematopoietic cell transplantation (HCT) for acute leukemia were identified. ALC cut-off was established using ROC analysis and subsequently the cohort was stratified. Time to endpoint analysis and cox regression modelling was computed to analyze outcomes.

RESULTS

A total of 72 patients met the inclusion criteria and were analyzed. Optimal ALC cut-off was established to be on day 14 (D14) with ALC > 0.3 × 10⁹/L. At 2 years, cumulative incidence of relapse was 16.9% vs 46.9% (P = 0.025) for early and delayed lymphocyte recovery cohorts, respectively. Chronic graft vs host disease was more prevalent in the early lymphocyte recovery (ELR) group at 70% vs 27%, respectively (P = 0.0006). On multivariable analysis for relapse, ELR retained its prognostic significance with HR = 0.27 (0.05-0.94, P = 0.038).

CONCLUSION

ELR is an independent predictor for relapse in patients receiving allogeneic HCT for acute leukemia. ELR was influenced by graft characteristics particularly CD34 count.

Prognostic Analysis of Absolute Lymphocyte and Monocyte Counts after Autologous Stem Cell Transplantation in Children, Adolescents, and Young Adults with Refractory or Relapsed Hodgkin Lymphoma

Previous studies in adults have shown that peripheral blood absolute lymphocyte and monocyte count ratio (ALC/AMC) after autologous stem cell transplantation (ASCT) can predict outcome in patients with relapsed/refractory (R/R) Hodgkin lymphoma (HL). We retrospectively reviewed all of our children, adolescent, and young adult (CAYA) patients (age ≤26) who underwent transplantation for R/R HL between 2004 and 2015. Seventy-six patients (median age, 21; range, 10 to 26 years) who reached day 100 disease free were analyzed; 33% of them had positron emission tomography (PET)-positive tumors before ASCT. Patients received high-dose carmustine, etoposide, cytarabine, and melphalan (n = 40) or gemcitabine/busulfan/melphalan (n = 36). Median follow-up after day 100 was 3.9 years (95% confidence interval [CI], 2.8 to 4.9). A day 100 ALC/AMC ratio >2.1 correlated with lower risk of relapse (hazard ratio,  .097; 95% CI, .03 to .29; P <.0001). Patients with day 100 ALC/AMC ratios >2.1 and ≤2.1 had 4-year relapse-free survival rates of 93% and 33%, respectively (P = .0001) and 4-year overall survival rates of 96% and 76%, respectively (P = .0001). In addition, an ALC/AMC ratio increase >1.8 from day 15 to day 100 correlated with lower risk of relapse (hazard ratio, .24; 95% CI, .08 to 0.73; P = .01). Likewise, an ALC/AMC ratio change >.26 from day 30 to day 100 also correlated with a lower likelihood of relapse (hazard ratio, .20; 95% CI,  .081 to .51; P = .0007). Multivariate analysis showed that a positive PET scan at ASCT, day 100 ALC/AMC ratio ≤ 2.1, and an ALC/AMC ratio change either ≤1.8 from day 15 to day 100 or ≤.26 from day 30 to day 100 were independent adverse predictors. In conclusion, our analysis confirms in CAYA patients prior observations in adults indicating a major prognostic effect of peripheral lymphocyte and monocyte counts at day 100 and earlier post-ASCT time points in R/R HL.

Optimal Threshold and Time of Absolute Lymphocyte Count Assessment for Outcome Prediction after Bone Marrow Transplantation

The recovery pace of absolute lymphocyte count (ALC) is prognostic after hematopoietic stem cell transplantation. Previous studies have evaluated a wide range of ALC cutoffs and time points for predicting outcomes. We aimed to determine the optimal ALC value for outcome prediction after bone marrow transplantation (BMT). A total of 518 patients who underwent BMT for acute leukemia or myelodysplastic syndrome between 1999 and 2010 were divided into a training set and a test set to assess the prognostic value of ALC on days 30, 60, 90, 120, 180, as well as the first post-transplantation day of an ALC of 100, 200, 300, 400, 500, and 1000/μL. In the training set, the best predictor of overall survival (OS), relapse-free survival (RFS), and nonrelapse mortality (NRM) was ALC on day 60. In the entire patient cohort, multivariable analyses demonstrated significantly better OS, RFS, and NRM and lower incidence of graft-versus-host disease (GVHD) in patients with an ALC >300/μL on day 60 post-BMT, both including and excluding patients who developed GVHD before day 60. Among the patient-, disease-, and transplant-related factors assessed, only busulfan-based conditioning was significantly associated with higher ALC values on day 60 in both cohorts. The optimal ALC cutoff for predicting outcomes after BMT is 300/μL on day 60 post-transplantation.

CD56dimCD57+NKG2C+ NK cell expansion is associated with reduced leukemia relapse after reduced intensity HCT

We have recently described a specialized subset of human natural killer (NK) cells with a CD56^dimCD57⁺NKG2C⁺ phenotype that expand specifically in response to cytomegalovirus (CMV) reactivation in hematopoietic cell transplant (HCT) recipients and exhibit properties characteristic of adaptive immunity. We hypothesize that these cells mediate relapse protection and improve post-HCT outcomes. In 674 allogeneic HCT recipients, we found that those who reactivated CMV had lower leukemia relapse (26% [17–35%], p=0.05) and superior disease-free survival (DFS) (55% [45–65%] p=0.04) 1 year after reduced intensity conditioning (RIC) compared to CMV seronegative recipients who experienced higher relapse rates (35% [27–43%]) and lower DFS (46% [38–54%]). This protective effect was independent of age and graft-versus-host disease (GvHD) and was not observed in recipients who received myeloablative (MA) regimens. Analysis of the reconstituting NK cells demonstrated that CMV reactivation is associated with both higher frequencies and greater absolute numbers of CD56^dimCD57⁺NKG2C⁺ NK cells, particularly after RIC HCT. Furthermore, expansion of these cells at 6 months post-transplant independently trended toward a lower 2-year relapse risk. Together, our data suggest that the protective effect of CMV reactivation on post-transplant relapse is in part driven by adaptive NK cell responses.

Absolute lymphocyte count recovery after allogeneic hematopoietic stem cell transplantation predicts clinical outcome

Immune reconstitution is critical for clinical outcome after allogeneic hematopoietic stem cell transplantation (HSCT). To determine the impact of absolute lymphocyte count (ALC) recovery on clinical outcomes, we conducted a retrospective study of 1109 adult patients who underwent a first allogeneic HSCT from 2003 through 2009, excluding patients who died or relapsed before day 30. The median age was 51 years (range, 18 to 74) with 52% undergoing reduced-intensity conditioning and 48% undergoing myeloablative conditioning HSCT with T cell-replete peripheral blood stem cells (93.7%) or marrow (6.4%) grafts. The median follow-up time was 6 years. To determine the threshold value of ALC for survival, the entire cohort was randomly split into a training set and a validation set in a 1:1 ratio, and then a restricted cubic spline smoothing method was applied to obtain relative hazard estimates of the relationship between ALC at 1 month and log hazard of progression-free survival (PFS). Based on this approach, ALC was categorized as ≤.2 × 10(9) cells/L (low) or >.2 × 10(9) cells/L. For patients with low ALC at 1, 2, or 3 months after HSCT, the overall survival (OS) (P ≤ .0001) and PFS (P ≤ .0002) were significantly lower and nonrelapse mortality (NRM) (P ≤ .002) was significantly higher compared with patients with ALC > .2 × 10(9) cells/L at each time point. When patients who had low ALC at 1, 2, or 3 months after HSCT were grouped together and compared, their outcomes were inferior to those of patients who had ALC > .2 × 10(9) cells/L at 1, 2, and 3 months after HSCT: the 5-year OS for patients with low ALC was 28% versus 46% for patients with ALC > .2 × 10(9) cells/L, P < .0001; the 5-year PFS was 21% versus 39%, P < .0001, respectively and 5-year NRM was 40% versus 18%, P < .0001, respectively. This result remained consistent when other prognostic factors, including occurrence of grade II to IV acute graft-versus-host disease (GVHD), were adjusted for in multivariable Cox models stratified by conditioning intensity: hazard ratio (HR) for OS: 1.52; P ≤ .0001; for PFS: 1.42; P = .0008; and for NRM: 2.4 P < .0001 for patients with low ALC. Low ALC was not significantly associated with relapse (HR, 1.01; P = .92) in the multivariable model. Low ALC early after HSCT is an independent risk factor for increased NRM and poor survival independent of grade II to IV acute GVHD.

Impact of clinical factors and allograft leukocyte content on post-transplant lymphopenia, monocytopenia, and survival in patients undergoing allogeneic peripheral blood haematopoietic cell transplant

BACKGROUND

We have previously shown that lymphopenia and monocytopenia at 2-3 months post-allogeneic haematopoietic cell transplant (HCT) is associated with poor survival in recipients of both myeloablative and reduced intensity conditioning regimens. It is not known whether the graft leukocyte content has a role in early lymphocyte and monocyte recovery following allogeneic T-cell replete peripheral blood HCT.

METHODS

Haematologic recovery data, including absolute lymphocyte and monocyte counts (ALC and AMC, respectively) at day +15, +30, +60, and +100, and outcomes data were pooled from two prior independent cohorts, and parameters were correlated with leukocyte graft content in those individuals receiving peripheral blood progenitor cell grafts. 216 consecutive patients from 2001-2010 were included in the analysis.

RESULTS

Neither infused allograft lymphocyte, monocyte, granulocyte, nor CD34+ cell number per kilogram recipient body weight correlated with haematologic recovery parameters or overall survival in this cohort. Prognostic factors for overall survival based on multivariate analysis were as expected from the results of the previous independent cohorts and included severity of chronic GVHD (p < 0.001), development of post-transplant relapse (p = 0.001), day +60 AMC > 0.3 x 10(9) cells/L (p = 0.0015), and day +100 ALC > 0.3 x 10(9) cells/L (p < 0.001). Low monocyte and lymphocyte counts at the day +60 and day +100 time points were significantly associated with acute GVHD and/or CMV viraemia.

CONCLUSIONS

This study suggests that graft cell count does not influence post-transplant monocyte and lymphocyte recovery following T-cell replete allogeneic peripheral blood HCT. Post-transplant complications such as acute GVHD and/or CMV viraemia negatively influenced monocyte and lymphocyte recovery, and hence the survival. Further studies aimed at understanding the mechanisms behind sustained lymphopenia and monocytopenia post-transplant are needed.

White blood cell recovery after allogeneic hematopoietic cell transplantation predicts clinical outcome

To determine whether outcome after allogeneic hematopoietic cell transplantation (HCT) could be estimated by using peripheral white blood cell count (WBC) as a metric that integrates several aspects of HCT recovery, we conducted a retrospective study of 1,109 adult patients who underwent first allogeneic HCT from 2003 through 2009. WBC at 1-3 months after HCT was categorized as low (<2), normal (2-10), and high (>10 × 10(9) cells/L). Overall survival (OS) and progression-free survival (PFS) were lower for patients with low or high WBC at 1-3 months after HCT (P < 0.0001). We developed a predictive three-group risk model based on the pattern of WBC recovery early after HCT. Five-year OS was 47, 30, and 15% (P < 0.0001) and 5-year PFS was 39, 22, and 14% for patients in the three different risk groups (P < 0.0001). The pattern of WBC recovery early after HCT provides prognostic information for relapse, nonrelapse mortality, progression-free survival, and overall survival. A scoring system based on the trajectory of the WBC in the first 3 months after HCT can effectively stratify patients into three groups with different PFS and OS. If validated, this system could be useful in the clinical management of patients after HCT, and to stratify patients enrolled on HCT clinical trials.

Immune reconstitution after haploidentical hematopoietic stem cell transplantation

Haploidentical hematopoietic stem cell transplantation (HSCT) offers the benefits of rapid and nearly universal donor availability and has been accepted worldwide as an alternative treatment for patients with hematologic malignancies who do not have a completely HLA-matched sibling or who require urgent transplantation. Unfortunately, serious infections and leukemia relapse resulting from slow immune reconstitution remain the 2 most frequent causes of mortality in patients undergoing haploidentical HSCT, particularly in those receiving extensively T cell-depleted megadose CD34(+) allografts. This review summarizes advances in immune recovery after haploidentical HSCT, focusing on the immune subsets likely to have the greatest impact on clinical outcomes. The progress made in accelerating immune reconstitution using different strategies after haploidentical HSCT is also discussed. It is our belief that a predictive immune subset-guided strategy to improve immune recovery might represent a future clinical direction.

Day 100 Peripheral Blood Absolute Lymphocyte/Monocyte Ratio and Survival in Classical Hodgkin's Lymphoma Postautologous Peripheral Blood Hematopoietic Stem Cell Transplantation

Day 100 prognostic factors of postautologous peripheral blood hematopoietic stem cell transplantation (APBHSCT) to predict clinical outcome in classical Hodgkin lymphoma (cHL) patients have not been evaluated. Thus, we studied if the day 100 peripheral blood absolute lymphocyte/monocyte ratio (Day 100 ALC/AMC) affects clinical outcomes by landmark analysis from day 100 post-APBHSCT. Only cHL patients achieving a complete remission at day 100 post-APBHSCT were studied. From 2000 to 2010, 131 cHL consecutive patients qualified for the study. The median followup from day 100 was 4.1 years (range: 0.2-12.3 years). Patients with a Day 100 ALC/AMC ≥ 1.3 experienced superior overall survival (OS) and progression-free survival (PFS) compared with Day 100 ALC/AMC < 1.3 (from day 100: OS, median not reached versus 2.8 years; 5 years OS rates of 93% (95% CI, 83%-97%) versus 35% (95% CI, 19%-51%), resp., P < 0.0001; from day 100: PFS, median not reached versus 1.2 years; 5 years PFS rates of 79% (95% CI, 69%-86%) versus 27% (95% CI, 14%-45%), resp., P < 0.0001). Day ALC/AMC ratio was an independent predictor for OS and PFS. Thus, Day 100 ALC/AMC ratio is a simple biomarker that can help to assess clinical outcomes from day 100 post-APBHSCT in cHL patients.