Circulating cell-free mitochondrial DNA as a diagnostic and prognostic biomarker in chronic and late acute graft-versus-host disease in children.

In an earlier study, we found that mitochondrial DNA (mtDNA) concentration is elevated in adults with chronic graft-versus-host disease (cGvHD), acting as an endogenous source of TLR9 agonists to augment B-cell responses. To validate this in children, we evaluated mtDNA plasma expression in a large pediatric cohort (ABLE/PBMTC 1202 study). Plasma cell-free mtDNA (cf-mtDNA) copy numbers were measured in 202 pediatric patients using quantitative Droplet Digital polymerase chain reaction (ddPCR). Two evaluations were performed: 1) before the onset of cGvHD or late acute graft-versus-host disease (aGvHD) at day 100 ± 14 days and 2) at the time of cGvHD onset compared with time-matched non-cGvHD controls. We found that cf-mtDNA copy numbers were not affected by immune reconstitution post-hematopoietic stem cell transplantation but were higher on day 100 before the onset of late aGvHD and at the onset of cGvHD. We found that cf-mtDNA was not impacted by previous aGvHD, but correlated with the early onset, NIH moderate/severe cGvHD, and did not correlate with other immune cell populations, cytokines, or chemokines but did with the metabolites spermine and taurine. Similar to adults, children have elevated plasma cf-mtDNA concentrations at the early onset of cGvHD, especially in NIH moderate/severe cGvHD, elevation with late aGvHD, and associated with metabolites involved in mitochondrial function.

Elevated ADA2 Enzyme Activity at the Onset of Chronic Graft-versus-Host Disease in Children.

Adenosinergic signaling has potent, context-specific effects on immune cells, particularly on the dysregulation of lymphocytes. This in turn may have a role in immune activation and loss of tolerance in such diseases as chronic graft-versus-host disease (chronic GVHD). We assessed whether changes in the enzymatic activity of adenosine deaminase 2 (ADA2), an enzyme that depletes adenosine in the extracellular space via conversion to inosine, may be associated with the onset of chronic GVHD. ADA2-specific enzyme activity was measured in plasma samples from 230 pediatric hematopoietic stem cell transplantation (HSCT) recipients enrolled on the Applied Biomarkers of Late Effects of Childhood Cancer (ABLE)/Pediatric Blood and Marrow Transplant Consortium (PBMTC) 1202 study and compared between patients developing chronic GVHD and those not developing chronic GVHD within 12 months of transplantation. ADA2 and its relationships with 219 previously measured plasma-soluble proteins, metabolites, and immune cell populations were evaluated as well. Plasma ADA2 enzyme activity was significantly elevated in pediatric HSCT recipients at the onset of chronic GVHD compared to patients without chronic GVHD and was not associated with prior history of acute GVHD or generalized inflammation as measured by C-reactive protein concentration. ADA2-specific enzyme activity met our criteria as a potential diagnostic biomarker of chronic GVHD (effect ratio ≥1.30 or ≤.75; area under the receiver operating characteristic curve ≥.60; P < .05) and was positively associated with markers of immune activation previously identified in pediatric chronic GVHD patients. These results support the potential of ADA2 enzyme activity, in combination with other biomarkers and subject to future validation, to aid the diagnosis of chronic GVHD in children post-HSCT.

A diagnostic classifier for pediatric chronic graft-versus-host disease: results of the ABLE/PBMTC 1202 study.

The National Institutes of Health Consensus criteria for chronic graft-versus-host disease (cGVHD) diagnosis can be challenging to apply in children, making pediatric cGVHD diagnosis difficult. We aimed to identify diagnostic pediatric cGVHD biomarkers that would complement the current clinical criteria and help differentiate cGVHD from non-cGVHD. The Applied Biomarkers of Late Effects of Childhood Cancer (ABLE) study, open at 27 transplant centers, prospectively evaluated 302 pediatric patients after hematopoietic cell transplant (234 evaluable). Forty-four patients developed cGVHD. Mixed and fixed effect regression analyses were performed on diagnostic cGVHD onset blood samples for cellular and plasma biomarkers, with individual markers declared relevant if they met 3 criteria: an effect ratio ≥1.3 or ≤0.75; an area under the curve (AUC) of ≥0.60; and a P value <5.814 × 10-4 (Bonferroni correction) (mixed effect) or <.05 (fixed effect). To address the complexity of cGVHD diagnosis in children, we built a machine learning-based classifier that combined multiple cellular and plasma biomarkers with clinical factors. Decreases in regulatory natural killer cells, naïve CD4 T helper cells, and naïve regulatory T cells, and elevated levels of CXCL9, CXCL10, CXCL11, ST2, ICAM-1, and soluble CD13 (sCD13) characterize the onset of cGVHD. Evaluation of the time dependence revealed that sCD13, ST2, and ICAM-1 levels varied with the timing of cGVHD onset. The cGVHD diagnostic classifier achieved an AUC of 0.89, with a positive predictive value of 82% and a negative predictive value of 80% for diagnosing cGVHD. Our polyomic approach to building a diagnostic classifier could help improve the diagnosis of cGVHD in children but requires validation in future prospective studies. This trial was registered at www.clinicaltrials.gov as #NCT02067832.

CD56bright CD16- natural killer cells as an important regulatory mechanism in chronic graft-versus-host disease.

Chronic graft-versus-host disease (cGvHD) is a major cause of morbidity after hematopoietic stem cell transplantation (HSCT). In large patient populations, we have shown a CD56bright natural killer (NK) population to strongly associate with a lack of cGvHD and we hypothesize that these cells function to suppress cGvHD. We aimed to isolate and define the characteristics of regulatory NK (NKreg) cells associated with suppression of cGvHD. Immunophenotypic evaluation of a large pediatric population found the CD56bright NK population associated with a lack of cGvHD to be perforin-, Granzyme B-, and CD335+. Transcriptome analysis of a small patient cohort of CD56bright compared to CD56dim NK cells found the NKreg cells to also overexpress Granzyme K, IL-7R, GPR183, RANK, GM-CSFR, TCF7, and IL23A. Further analysis of this CD56bright NKreg population found a subpopulation that overexpressed IRF1, and TNF. We also found that viable NKreg cells may be isolated by sorting on CD56+ and CD16- NK cells, and this population can suppress allogeneic CD4+ T cells, but not Treg cells or CD8+ T cells through a non-cytolytic, cell-cell contact dependent mechanism. Suppression was not reliant upon the NKp44, NKp46, or GPR183 receptors. Additionally, NKreg cells do not kill leukemic cells. Moreover, this is the first paper to clearly establish that a CD56brightCD3-CD16-perforin- NKreg population associates with a lack of cGvHD and has several unique characteristics, including the suppression of helper T-cell function in vitro. With further investigation we may decipher the mechanism of NKreg suppression and operationalize expansion of NKreg cells associated with cGvHD suppression.

Metabolomic identification of α-ketoglutaric acid elevation in pediatric chronic graft-versus-host disease.

Chronic graft-versus-host disease (cGVHD) is the most common cause for non-relapse mortality postallogeneic hematopoietic stem cell transplant (HSCT). However, there are no well-defined biomarkers for cGVHD or late acute GVHD (aGVHD). This study is a longitudinal evaluation of metabolomic patterns of cGVHD and late aGVHD in pediatric HSCT recipients. A quantitative analysis of plasma metabolites was performed on 222 evaluable pediatric subjects from the ABLE/PBMTC1202 study. We performed a risk-assignment analysis at day + 100 (D100) on subjects who later developed either cGVHD or late aGVHD after day 114 to non-cGVHD controls. A second analysis at diagnosis used fixed and mixed multiple regression to compare cGVHD at onset to time-matched non-cGVHD controls. A metabolomic biomarker was considered biologically relevant only if it met all 3 selection criteria: (1) P ≤ .05; (2) effect ratio of ≥1.3 or ≤0.75; and (3) receiver operator characteristic AUC ≥0.60. We found a consistent elevation in plasma α-ketoglutaric acid before (D100) and at the onset of cGVHD, not impacted by cGVHD severity, pubertal status, or previous aGVHD. In addition, late aGVHD had a unique metabolomic pattern at D100 compared with cGVHD. Additional metabolomic correlation patterns were seen with the clinical presentation of pulmonary, de novo, and progressive cGVHD. α-ketoglutaric acid emerged as the single most significant metabolite associated with cGVHD, both in the D100 risk-assignment and later diagnostic onset analysis. These distinctive metabolic patterns may lead to improved subclassification of cGVHD. Future validation of these exploratory results is needed. This trial was registered at www.clinicaltrials.gov as #NCT02067832.

"Age Related Differences in the Biology of Chronic Graft-Versus-Host Disease After Hematopoietic Stem Cell Transplantation".

It is established that pediatric hematopoietic stem cell transplant (HSCT) recipients have a lower rate of chronic graft-versus-host disease (cGvHD) compared to adults. Our group has previously published immune profiles changes associated with cGvHD of clinically well-defined adult and pediatric HSCT cohorts. Since all analyses were performed by the same research group and analyzed using identical methodology, we first compared our previous immune profile analyses between adults and children. We then performed additional analyses comparing the T cell populations across age groups, and a sub-analysis of the impact of the estimated pubertal status at time of HSCT in our pediatric cohort. In all analyses, we corrected for clinical covariates including total body irradiation and time of onset of cGvHD. Three consistent findings were seen in both children and adults, including elevations of ST2 and naive helper T (Th) cells and depression of NKreg cells. However, significant differences exist between children and adults in certain cytokines, B cell, and Treg populations. In children, we saw a broad suppression of newly formed B (NF-B) cells, whereas adults exhibited an increase in T1-CD21lo B cells and a decrease in T1-CD24hiCD38hi B cells. Prepubertal children had elevations of aminopeptidase N (sCD13) and ICAM-1. Treg abnormalities in children appeared to be primarily in memory Treg cells, whereas in adults the abnormalities were in naïve Treg cells. In adults, the loss of PD1 expression in naïve Treg and naïve Th cells was associated with cGvHD. We discuss the possible mechanisms for these age-related differences, and how they might theoretically impact on different therapeutic approaches to cGvHD between children and adults.

Immune profile differences between chronic GVHD and late acute GVHD: results of the ABLE/PBMTC 1202 studies.

Human graft-versus-host disease (GVHD) biology beyond 3 months after hematopoietic stem cell transplantation (HSCT) is complex. The Applied Biomarker in Late Effects of Childhood Cancer study (ABLE/PBMTC1202, NCT02067832) evaluated the immune profiles in chronic GVHD (cGVHD) and late acute GVHD (L-aGVHD). Peripheral blood immune cell and plasma markers were analyzed at day 100 post-HSCT and correlated with GVHD diagnosed according to the National Institutes of Health consensus criteria (NIH-CC) for cGVHD. Of 302 children enrolled, 241 were evaluable as L-aGVHD, cGVHD, active L-aGVHD or cGVHD, and no cGVHD/L-aGVHD. Significant marker differences, adjusted for major clinical factors, were defined as meeting all 3 criteria: receiver-operating characteristic area under the curve ≥0.60, P ≤ .05, and effect ratio ≥1.3 or ≤0.75. Patients with only distinctive features but determined as cGVHD by the adjudication committee (non-NIH-CC) had immune profiles similar to NIH-CC. Both cGVHD and L-aGVHD had decreased transitional B cells and increased cytolytic natural killer (NK) cells. cGVHD had additional abnormalities, with increased activated T cells, naive helper T (Th) and cytotoxic T cells, loss of CD56bright regulatory NK cells, and increased ST2 and soluble CD13. Active L-aGVHD before day 114 had additional abnormalities in naive Th, naive regulatory T (Treg) cell populations, and cytokines, and active cGVHD had an increase in PD-1- and a decrease in PD-1+ memory Treg cells. Unsupervised analysis appeared to show a progression of immune abnormalities from no cGVHD/L-aGVHD to L-aGVHD, with the most complex pattern in cGVHD. Comprehensive immune profiling will allow us to better understand how to minimize L-aGVHD and cGVHD. Further confirmation in adult and pediatric cohorts is needed.

A Germline Mutation in the C2 Domain of PLCγ2 Associated with Gain-of-Function Expands the Phenotype for PLCG2-Related Diseases.

We report three new cases of a germline heterozygous gain-of-function missense (p.(Met1141Lys)) mutation in the C2 domain of phospholipase C gamma 2 (PLCG2) associated with symptoms consistent with previously described auto-inflammation and phospholipase Cγ2 (PLCγ2)-associated antibody deficiency and immune dysregulation (APLAID) syndrome and pediatric common variable immunodeficiency (CVID). Functional evaluation showed platelet hyper-reactivity, increased B cell receptor-triggered calcium influx and ERK phosphorylation. Expression of the altered p.(Met1141Lys) variant in a PLCγ2-knockout DT40 cell line showed clearly enhanced BCR-triggered influx of external calcium when compared to control-transfected cells. Our results further expand the molecular basis of pediatric CVID and phenotypic spectrum of PLCγ2-related defects.

Anti-Thymocyte Globulin Prophylaxis Induces a Decrease in Naive Th Cells to Inhibit the Onset of Chronic Graft-versus-Host Disease: Results from the Canadian Bone Marrow Transplant Group (CBMTG) 0801 Study.

Anti-thymocyte globulin (ATG) is an established approach to decrease chronic GVHD (cGVHD), yet the exact mechanism is uncertain. To better understand the mechanism of action of ATG in preventing cGVHD, we evaluated the day 100 immune reconstitution of known cGVHD cellular biomarkers using patients from the randomized Canadian Bone Marrow Transplant Group (CBMTG) 0801 trial, which demonstrated a significant impact of ATG on cGVHD. In a separate companion biology study, we evaluated the impact of ATG prophylaxis on cGVHD cellular markers at day 100 in 40 CBMTG 0801 patients. Analysis focused on previously identified cGVHD cellular biomarkers, including naive helper T (Th) cells, recent thymic emigrant (RTE) Th cells, CD21low B cells, CD56bright NKreg cells, and Treg cells ST2, osteopontin, soluble B-cell activating factor (sBAFF), Interleukin-2 receptor alpha (sCD25), T-cell immunoglobulin and mucin domain-3 (TIM-3), matrix metallopeptidase 3, ICAM-1, C-X-C motif chemokine 10 (CXCL10), and soluble aminopeptidase N. The ATG-treated group had a >10-fold decrease in both RTE naive Th and naive Th cells (P < .0001) and a 10-fold increase in CD56bright NKreg cells (P < .0001). Treg cells, conventional Th cells, CD21low B cells, and all plasma markers were not affected. In the populations most affected by ATG, changes in naive Th cells were associated with the later development of cGVHD. This analysis suggests that ATG primarily impacts on cGVHD through suppression of naive Th cell expansion after transplantation. These associations need to be validated in additional studies.

Comprehensive B Cell Phenotyping Profile for Chronic Graft-versus-Host Disease Diagnosis.

Previous studies have reported single B cell-related chronic graft-versus-host disease diagnostic (cGVHD) biomarkers, such as B cell-activating factor (BAFF), CD21low, and immature B cells, but research on the performance of biomarker combinations and the covariate effect of steroids is lacking. The primary objective of this study was to determine the most accurate combination of B cell populations using cell surface staining flow cytometry in an independent cohort of patients with cGVHD. Secondary objectives included assessing the effect of corticosteroid use at sample collection on the makeup and accuracy of the diagnostic panel and identifying the mechanism underlying low surface expression of BAFF receptor (BAFF-R) on B cells in cGVHD. Flow cytometry analysis was performed in an adult cohort of post-HCT patients with cGVHD onset (n = 44) and time-matched recipients without cGVHD (n = 63). We confirmed that the onset of cGVHD was associated with higher soluble BAFF (sBAFF) levels, elevated CD27-CD10-CD21low CD19+ B cell and classical switched memory B cell counts, and reduced transitional and naïve B cell counts. The highest single B cell population area under the receiver operating characteristic (ROC) curve (AUC) was .72 for transitional type 1 CD21low B cells. We also showed a significant inverse relationship between sBAFF and surface BAFF-R expression caused by sBAFF modulation of BAFF-R. Steroid use at sample collection influenced the significance of the sBAFF:B cell ratio, naïve and marginal zone-like B cells. The optimal combination of B cell subsets most significantly associated with cGVHD onset with or without concurrent corticosteroid use resulted in ROC AUCs of .87 and .84, respectively. Transitional and CD21low B cells were the only populations present in both panels; however, analyzing only these populations resulted in ROC AUCs of .79 and .78, respectively. This suggests that the inclusion of other populations and use of different panels depending on steroid use is necessary to achieve better accuracy. sBAFF was not a component of either panel. These novel B cell profiles could be tested prospectively in patients post-HSCT and could lead to focused mechanistic studies.

Heterogeneity of chronic graft-versus-host disease biomarkers: association with CXCL10 and CXCR3+ NK cells.

Chronic graft-versus-host disease (cGVHD) remains one of the most significant long-term complications after allogeneic blood and marrow transplantation. Diagnostic biomarkers for cGVHD are needed for early diagnosis and may guide identification of prognostic markers. No cGVHD biomarker has yet been validated for use in clinical practice. We evaluated both previously known markers and performed discovery-based analysis for cGVHD biomarkers in a 2 independent test sets (total of 36 cases ≤1 month from diagnosis and 31 time-matched controls with no cGVHD). On the basis of these results, 11 markers were selected and evaluated in 2 independent replication cohorts (total of 134 cGVHD cases and 154 controls). cGVHD cases and controls were evaluated for several clinical covariates, and their impact on biomarkers was identified by univariate analysis. The 2 replications sets were relatively disparate in the biomarkers they replicated. Only sBAFF and, most consistently, CXCL10 were identified as significant in both replication sets. Other markers identified as significant in only 1 replication set included intercellular adhesion molecule 1 (ICAM-1), anti-LG3, aminopeptidase N, CXCL9, endothelin-1, and gelsolin. Multivariate analysis found that all covariates evaluated affected interpretation of the biomarkers. CXCL10 had an increased significance in combination with anti-LG3 and CXCL9, or inversely with CXCR3(+)CD56(bright) natural killer (NK) cells. There was significant heterogeneity of cGVHD biomarkers in a large comprehensive evaluation of cGVHD biomarkers impacted by several covariates. Only CXCL10 strongly correlated in both replication sets. Future analyses for plasma cGVHD biomarkers will need to be performed on very large patient groups with consideration of multiple covariates.

Insights into the structural stability of nuclear matrix ribonucleoprotein, LMG160: thermodynamic and spectroscopic analysis.

Low-mobility group nonhistone chromatin protein, LMG160, is a nuclear matrix ribonucleoprotein particle (RNP) which has a RNA molecule with approximately 300 bases. In this study, structural stability of the intact LMG160 (I-LMG160) was investigated at different ionic strength and in the absence of its RNA moiety (T-LMG160) employing spectroscopic and thermodynamic techniques. The UV absorption spectra showed hypochromicity and red shift under increasing ionic strength for both forms of LMG160 but in different extents. The fluorescence emission intensity was decreased as ionic strength was increased and the Stern-Volmer quenching constant (Ksv) for T-LMG160 was 3.7 times less than for I-LMG160. In the absence of sodium chloride, I-LMG160 exhibited a very stable structure against the temperature change compared to T-LMG160. The thermodynamic parameters showed that the positive values of ΔHm and ΔSm increased by increasing ionic strength in both forms of LMG160. Removal of the RNA moiety altered secondary structure: as T-LMG160 showed more helical content than I-LMG160. From the results, it is concluded that I-LMG160 is more sensitive to alteration of environment and the RNA has an important role in this RNP conformation. Also, interaction of both I- and T-LMG160 with sodium chloride is entropy driven and is usually accompanied by surface hydrophobicity.

Toxic effects of lead and nickel nitrate on rat liver chromatin components.

The biological activity of heavy metals is related to their physicochemical interaction with biological receptors. In the present study, the effect of low concentrations of nickel nitrate and lead nitrate (<0.3 mM) on rat liver soluble chromatin and histone proteins was examined. The results showed that addition of various concentrations of metals to chromatin solution preceded the chromatin into aggregation and precipitation in a dose-dependant manner; however, the extent of absorbance changes at 260 and 400 nm was different between two metals. Gel electrophoresis of histone proteins and DNA of the supernatants obtained from the metal-treated chromatin and the controls revealed higher affinity of lead nitrate to chromatin compared to nickel nitrate. Also, the binding affinity of lead nitrate to histone proteins free in solution was higher than nickel. On the basis of the results, it is concluded that lead reacts with chromatin components even at very low concentrations and induce chromatin aggregation through histone-DNA cross-links. Whereas, nickel nitrate is less effective on chromatin at low concentrations, suggesting higher toxicity of lead nitrate on chromatin compared to nickel.

Identification of low-molecular-weight protein (SCP1) from shark cartilage with anti-angiogenesis activity and sequence similarity to parvalbumin.

Cartilage was considered as a possible natural source of anti-angiogenesis compounds due to its known avascular nature. In this study, a low-molecular-weight protein with an anti-angiogenesis activity was isolated from shark cartilage using a mild extraction procedure. The protein was purified to homogeneity by gel filtration and electroelution techniques and its N-terminal amino acid sequence was determined. The purified protein, designated as SCP1, represented a molecular weight of 13.7 kDa, pI of 6.9-7 and its N-terminal sequence revealed sequence similarity to alpha parvalbumin family. The protein inhibited angiogenesis when subjected to microvessel sprouting of collagen-embedded rat aortic ring assay. It is suggested that SCP1 could be considered as a new angiogenesis inhibitor derived from shark cartilage.