Miguel Waterhouse

Horizontal DNA Transfer from Donor to Host Cells as an Alternative Mechanism of Epithelial Chimerism after Allogeneic Hematopoietic Cell Transplantation

Animal and human studies have shown that after allogeneic hematopoietic cell transplantation, epithelial cells containing donor-derived genome emerge. The mechanisms underlying this phenomenon are still unclear. We hypothesized that horizontal transfer of the hematopoietic donor-DNA to the host epithelium confers a possible operating mechanism. In an in vitro model mimicking the lymphocyte-epithelial interaction, we cocultivated keratinocyte HaCaT cells (Y-chromosome negative) with nonapoptotic or apoptotic, CMFDA, or BrdU-labeled hematopoietic Jurkat cells (Y+) and looked for the emergence of HaCaT cells bearing Jurkat genome. We found that DNA can be horizontally transferred from hematopoietic to epithelial cell lines through phagocytosis of apoptotic bodies. The ingested genomic material was also found within the nuclear compartment and in isolated chromosomes obtained from HaCaT metaphases. Both lysosomal inhibition in HaCaT cells and repetitive load of HaCaT cells with apoptotic bodies increased the intercellular and intranuclear DNA delivery. Although recipient cells remained viable and showed to express the foreign DNA, this expression was transient. Taking into consideration these findings of horizontal DNA transfer between hematopoietic and epithelial cells, we evaluated by quantitative microsatellite analysis the amount of donor DNA in 176 buccal swabs obtained from 71 patients after allogeneic transplantation. We found a high amount of donor-DNA (mean 26.6%) in the majority (89.7%) of them, although no donor hematopoietic cells were evident in the samples by immunofluorescence. We propose that the incessant charge of the transplant recipient with donor-DNA and its inappropriate intranuclear delivery in host epithelium may explain the emergence of epithelial cells with donor-derived genome.

Soluble HLA-G Molecules and HLA-G 14-Base Pair Polymorphism After Allogeneic Hematopoietic Cell Transplantation

HLA-G 14-base pair (bp) polymorphism and soluble human leukocyte antigen G were previously reported to be implicated in allogeneic hematopoietic cell transplantation (allo-HSCT) outcome. However, soluble HLA-G blood levels and the 14-bp insertion-deletion polymorphism were separately assessed in the context of allo-HSCT. The aim of the present study was to examine the influence of the 14-bp insertion/deletion polymorphism of the HLA-G gene together with the soluble HLA-G plasma levels on allo-HSCT complications. We investigated the possible impact of HLA-G 14-bp polymorphism together with the pretransplantation and posttransplantation concentration of soluble HLA-G in 59 patients undergoing allo-HSCT. No association was found between the HLA-G 14-bp polymorphism, the soluble HLA-G level and acute graft-versus-host disease (GvHD), disease recurrence, or death. In contrast with previous reports the present data suggest a weak or negligible involvement of both 14-bp polymorphism on HLA-G gene and sHLA-G concentration in posttransplantation complications such as acute or chronic GvHD, relapse, or death.

An internal validation approach and quality control on hematopoietic chimerism testing after allogeneic hematopoietic cell transplantation

Abstract Background: Hematopoietic chimerism analysis is important in the follow-up of patients undergoing allogeneic stem cell transplantation. PCR of short tandem repeats is mainly used for monitoring chimerism after transplantation. Validation studies and precision of assay’s performance with respect to different mixed chimerism stages is not fully addressed. The aim of the present study was to assess the impact of several microsatellite analytical parameters in the quantification of hematopoietic chimerism after allogeneic hematopoietic stem cell transplantation and to analyze the overall analytical process through the application of internal quality control procedures. Methods: Artificial DNA mixtures prepared in known proportions and patients samples were analyzed using three microsatellites, together with amplification of amelogenin gene and fluorescence in situ hybridization (FISH) for X and Y chromosomes. Limit of detection, analytical and clinical sensitivity, stochastic threshold and precision profiling was established. Levey-Jennings charts and Westgard rules were applied for quality control evaluation. Results: Analytical and clinical sensitivity of the microsatellite markers was between 0.5% and 1.6%. Amelogenin detection and FISH for X and Y chromosomes showed a similar sensitivity. Severe allelic imbalance resulted in up to 50% difference between the calculated and corrected mixed chimerism. Systematic errors were identified using Levey-Jennings charts and Westgard rules. Conclusions: Analysis of hematopoietic chimerism performance is a critical step to better understand potential intrinsic errors that may impact the final hematopoietic chimerism results. Implementing quality control tools, such as Levey-Jennings charts together with Westgard rules can identify systematic and random errors so corrective actions can be performed.

Early mixed hematopoietic chimerism detection by digital droplet PCR in patients undergoing gender-mismatched hematopoietic stem cell transplantation

Abstract Background: Clinical decision making after allogeneic stem cell transplantation (HSCT) is partially based on hematopoietic chimerism analysis. Polymerase chain reaction amplification of polymorphic short tandem repeats (STR-PCR) is currently considered the gold standard for chimerism surveillance after transplantation. Nevertheless, this method has shown several limitations. Emerging technologies such as digital PCR (dPCR) has been applied to detect hematopoietic chimerism. Despite previous reports, the clinical usefulness of dPCR is unclear because the studies were performed in limited patient populations with short follow-ups. Methods: In order to compare hematopoietic chimerism detection time and rate, we analyzed 591 samples from 155 patients undergoing gender-mismatched HSCT using STR-PCR and dPCR. We also established the correlation between both methods in artificial DNA mixtures prepared in known proportions and in clinical samples. Results: Depending on the artificial DNA mixture analyzed the correlation coefficient between both methods was 0.9946 and 0.9732. The limit of detection for dPCR was 0.01%. Of 157 samples with donor and recipient DNA, mixed chimerism (MC) was detected solely by dPCR in 66 samples. Within the group of patients relapsing after HSCT (n=32) MC was detected earlier in 15 of these patients with dPCR in comparison with STR-PCR. The mean time from MC detection to relapse was 155 days (range: 13–385 days) and 65 days (range: 0–203 days) for dPCR and STR-PCR, respectively. Conclusions: dPCR is a sensitive and accurate method for the quantification of hematopoietic chimerism allowing earlier MC detection compared to STR-PCR.

Cell-free DNA characteristics and chimerism analysis in patients after allogeneic cell transplantation

Cell-free DNA (cfDNA) isolated from plasma or serum has received increasing interest for diagnostic applications in pregnancy, solid tumors and solid organ transplantation. The reported clinical usefulness of cfDNA obtained from plasma or serum in patients undergoing allogeneic cell transplantation (alloHSCT) is scarce.nnnOBJECTIVEnTo analyze the potential clinical utility of cfDNA chimerism analysis after alloHSCT.nnnDESIGN AND METHODSnA total of 196 samples obtained from 110 patients were investigated for their chimeric status both in peripheral blood and plasma using standard PCR for microsatellite amplification. Plasma DNA size distribution was analyzed using capillary electrophoresis.nnnRESULTSnThe mean cfDNA concentration in the transplanted patients was 469ng/ml (range: 50-10,700ng/ml). The size range of almost 80% of the analyzed fragments was between 80 and 200bp. In 41 out of the 110 patients included in the study a mixture of donor and recipient plasma cfDNA was detected. There was a statistically significant difference in the percentage of plasma mixed chimerism between the patients without transplant related complications and the patients with either GvHD (p<0.05) or relapse (p<0.01). In those patients who showed improvement of GvHD also displayed a decrease in the observable percentage of recipient cfDNA during GvHD treatment. In patients without improvement or even with worsening of acute GvHD, stable or increasing levels of recipient cfDNA were detected.nnnCONCLUSIONSncfDNA in combination with peripheral blood and bone marrow cell chimerism analysis might improve its utility in the clinic in particular in those patients with clinical complications after alloHSCT.

Impact of Lung Function on Bronchiolitis Obliterans Syndrome and Outcome after Allogeneic Hematopoietic Cell Transplantation with Reduced-Intensity Conditioning

Lung function deterioration contributes to treatment-related morbidity and mortality in patients after allogeneic hematopoietic cell transplantation (allo-HCT). Better understanding of impaired lung function including bronchiolitis obliterans syndrome (BOS) as chronic manifestation of graft-versus-host disease (GVHD) might improve outcomes of patients after allo-HCT. To detect early pulmonary function test abnormalities associated with BOS incidence and outcome after allo-HCT, we performed a retrospective analysis of homogenous-treated 445 patients (median age, 61.9 years; range, 19 to 76 years) with a reduced intensity/toxicity conditioning protocol. The cumulative incidence of BOS was 4.1% (95% confidence interval [CI], 2.6 to 6.4) at 1 year and 8.6% (95% CI, 6.3 to 11.6) at 5 years after allo-HCT with a median follow-up of 43.2 months (range, 3.3 to 209 months). In multivariate analysis, pre-existence of moderate small airway disease reflected by decreased midexpiratory flows before allo-HCT was associated with increased risk for BOS development. In addition, severe small airway disease before allo-HCT and combined restrictive/obstructive lung disease at day +100 after allo-HCT were associated with higher risk for nonrelapse mortality (NRM) due mainly to pulmonary cause of death. In summary, we identified novel pulmonary function test abnormalities prior and after allo-HCT associated with BOS development and NRM. These findings might help to identify a risk population and result in personalized GVHD prophylaxis and preventive or early therapeutic interventions.

GVHD meets GWAS.

In this issue of Blood , [Sato-Otsubo et al][1] perform a genome-wide association study (GWAS) to identify minor histocompatibility antigens associated with clinically relevant graft-versus-host disease (GVHD).[1][2]nn![Figure][3] nnSchematic representation of different factors influencing the

Diagnostic utility of a soluble cytokeratin 18 assay for gastrointestinal graft-vs.-host disease detection

Abstract Background: Gastrointestinal/liver graft-vs.-host disease is a frequent complication after allogeneic hematopoietic cell transplantation. Endoscopic biopsies are needed to confirm clinical diagnosis, but this is not always feasible due to concurrent complications after transplantation. Cytokeratin 18 is expressed in epithelial colon cells and hepatocytes. Apoptosis, a hallmark of graft-vs.-host disease, results in the cleavage of cytokeratin 18 and the resulting fragments are released into the circulation. Methods: The aim of the present study was to assess the general performance and usefulness of a serologic test for soluble cytokeratin 18 for gastrointestinal/liver graft-vs.-host disease detection. Plasmatic concentration of soluble cytokeratin 18 was measured in 38 individuals undergoing hematopoietic cell transplantation. A two-fold increase of sCK18 above the pre-transplant concentration was used as a threshold value. Results: Plasmatic concentration of soluble cytokeratin 18 was significantly elevated in patients with gastrointestinal/liver graft-vs.-host disease. Soluble cytokeratin 18 concentration raised before the onset of clinical symptoms in 69% of the patients with gastrointestinal/liver graft-vs.-host disease. The threshold value used in our study resulted in a high sensitivity and a low false negative rate for gastrointestinal/liver graft-vs.-host disease detection. Conclusions: Soluble cytokeratin 18 seems to be a suitable biomarker for gastrointestinal/liver graft-vs.-host disease detection, particularly when a biopsy is not feasible.