Fetal-origin cells in maternal circulation correlate with placental dysfunction, fetal sex, and severe hypertension during pregnancy

Fetal microchimerism (FMc) arises when fetal cells enter maternal circulation, potentially persisting for decades. Increased FMc is associated with fetal growth restriction, preeclampsia, and anti-angiogenic shift in placenta-associated proteins in diabetic and normotensive term pregnancies. The two-stage model of preeclampsia postulates that placental dysfunction causes such shift in placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFLt-1), triggering maternal vascular inflammation and endothelial dysfunction. We investigated whether anti-angiogenic shift, fetal sex, fetal growth restriction, and severe maternal hypertension correlate with FMc in hypertensive disorders of pregnancy with new-onset features (n = 125). Maternal blood was drawn pre-delivery at > 25 weeks' gestation. FMc was detected by quantitative polymerase chain reaction targeting paternally inherited unique fetal alleles. PlGF and sFlt-1 were measured by immunoassay. We estimated odds ratios (ORs) by logistic regression and detection rate ratios (DRRs) by negative binomial regression. PlGF correlated negatively with FMc quantity (DRR = 0.2, p = 0.005) and female fetal sex correlated positively with FMc prevalence (OR = 5.0, p < 0.001) and quantity (DRR = 4.5, p < 0.001). Fetal growth restriction no longer correlated with increased FMc quantity after adjustment for correlates of placental dysfunction (DRR = 1.5, p = 0.272), whereas severe hypertension remained correlated with both FMc measures (OR = 5.5, p = 0.006; DRR = 6.3, p = 0.001). Our findings suggest that increased FMc is independently associated with both stages of the two-stage preeclampsia model. The association with female fetal sex has implications for microchimerism detection methodology. Future studies should target both male and female-origin FMc and focus on clarifying which placental mechanisms impact fetal cell transfer and how FMc impacts the maternal vasculature.

Signaling via a CD27-TRAF2-SHP-1 axis during naive T cell activation promotes memory-associated gene regulatory networks

The interaction of the tumor necrosis factor receptor (TNFR) family member CD27 on naive CD8+ T (Tn) cells with homotrimeric CD70 on antigen-presenting cells (APCs) is necessary for T cell memory fate determination. Here, we examined CD27 signaling during Tn cell activation and differentiation. In conjunction with T cell receptor (TCR) stimulation, ligation of CD27 by a synthetic trimeric CD70 ligand triggered CD27 internalization and degradation, suggesting active regulation of this signaling axis. Internalized CD27 recruited the signaling adaptor TRAF2 and the phosphatase SHP-1, thereby modulating TCR and CD28 signals. CD27-mediated modulation of TCR signals promoted transcription factor circuits that induced memory rather than effector associated gene programs, which are induced by CD28 costimulation. CD27-costimulated chimeric antigen receptor (CAR)-engineered T cells exhibited improved tumor control compared with CD28-costimulated CAR-T cells. Thus, CD27 signaling during Tn cell activation promotes memory properties with relevance to T cell immunotherapy.

Cancer-Associated Fibroblast-Like Tumor Cells Remodel the Ewing Sarcoma Tumor Microenvironment

PURPOSE

Despite limited genetic and histologic heterogeneity, Ewing sarcoma (EwS) tumor cells are transcriptionally heterogeneous and display varying degrees of mesenchymal lineage specification in vitro. In this study, we investigated if and how transcriptional heterogeneity of EwS cells contributes to heterogeneity of tumor phenotypes in vivo.

EXPERIMENTAL DESIGN

Single-cell proteogenomic-sequencing of EwS cell lines was performed and integrated with patient tumor transcriptomic data. Cell subpopulations were isolated by FACS for assessment of gene expression and phenotype. Digital spatial profiling and human whole transcriptome analysis interrogated transcriptomic heterogeneity in EwS xenografts. Tumor cell subpopulations and matrix protein deposition were evaluated in xenografts and patient tumors using multiplex immunofluorescence staining.

RESULTS

We identified CD73 as a biomarker of highly mesenchymal EwS cell subpopulations in tumor models and patient biopsies. CD73+ tumor cells displayed distinct transcriptional and phenotypic properties, including selective upregulation of genes that are repressed by EWS::FLI1, and increased migratory potential. CD73+ cells were distinguished in vitro and in vivo by increased expression of matrisomal genes and abundant deposition of extracellular matrix (ECM) proteins. In epithelial-derived malignancies, ECM is largely deposited by cancer-associated fibroblasts (CAF), and we thus labeled CD73+ EwS cells, CAF-like tumor cells. Marked heterogeneity of CD73+ EwS cell frequency and distribution was detected in tumors in situ, and CAF-like tumor cells and associated ECM were observed in peri-necrotic regions and invasive foci.

CONCLUSIONS

EwS tumor cells can adopt CAF-like properties, and these distinct cell subpopulations contribute to tumor heterogeneity by remodeling the tumor microenvironment. See related commentary by Kuo and Amatruda, p. 5002.

Ultrasensitive chimerism enhances measurable residual disease testing after allogeneic hematopoietic cell transplantation

Increasing mixed chimerism (reemerging recipient cells) after allogeneic hematopoietic cell transplant (allo-HCT) can indicate relapse, the leading factor determining mortality in blood malignancies. Most clinical chimerism tests have limited sensitivity and are primarily designed to monitor engraftment. We developed a panel of quantitative polymerase chain reaction assays using TaqMan chemistry capable of quantifying chimerism in the order of 1 in a million. At such analytic sensitivity, we hypothesized that it could inform on relapse risk. As a proof-of-concept, we applied our panel to a retrospective cohort of patients with acute leukemia who underwent allo-HCT with known outcomes. Recipient cells in bone marrow aspirates (BMAs) remained detectable in 97.8% of tested samples. Absolute recipient chimerism proportions and rates at which these proportions increased in BMAs in the first 540 days after allo-HCT were associated with relapse. Detectable measurable residual disease (MRD) via flow cytometry in BMAs after allo-HCT showed limited correlation with relapse. This correlation noticeably strengthened when combined with increased recipient chimerism in BMAs, demonstrating the ability of our ultrasensitive chimerism assay to augment MRD data. Our technology reveals an underappreciated usefulness of clinical chimerism. Used side by side with MRD assays, it promises to improve identification of patients with the highest risk of disease reoccurrence for a chance of early intervention.

Poor glucose control and markers of placental dysfunction correlate with increased circulating fetal microchimerism in diabetic pregnancies

Fetal microchimerism (FMc) arises during pregnancy as fetal cells enter maternal circulation and remain decades postpartum. Circulating FMc is increased in preeclampsia, fetal growth restriction, and as we recently showed, is associated with biomarkers of placental dysfunction in normotensive term pregnancies. Diabetes mellitus (DM) also correlates with placental dysfunction. We hypothesize that poor glucose control and markers of placental dysfunction are associated with increased circulating FMc in diabetic pregnancies. We included 122 pregnancies preceding active labor (pregestational DM, n = 77, gestational DM (GDM), n = 45) between 2001 and 2017. Maternal and fetal samples were genotyped for various human leukocyte antigen (HLA) loci, and other polymorphisms to identify fetus-specific alleles. We used validated polymerase chain reaction (PCR) assays to quantify FMc in maternal peripheral blood buffy coat. Negative binomial regression with adjustment for confounders was used to assess FMc quantity. In pregestational DM, increased circulating FMc correlated with elevation of HbA1c (≥ 6.0 %) (detection rate ratio (DRR) = 4.9, p = 0.010) and a 1000 pg/mL rise in the anti-angiogenic biomarker soluble fms-like tyrosine kinase-1 (sFlt-1) (DRR = 1.1, p = 0.011). In GDM, increased FMc correlated with elevated 2-hour oral glucose tolerance test results (DRR = 2.3, p = 0.046) and birthweight < 10th or > 90th percentile (DRR = 4.2, p = 0.049). These findings support our novel hypothesis that FMc correlates with poor glucose control and various aspects of placental dysfunction in DM. Whether increased FMc in pregnancies with poor glucose control and placental dysfunction contributes to the risk of preeclampsia in diabetic pregnancies and to the increased risk of chronic cardiovascular disease later in life remains to be investigated.

Fetal microchimerism and the two-stage model of preeclampsia

Fetal cells cross the placenta during pregnancy and some have the ability to persist in maternal organs and circulation long-term, a phenomenon termed fetal microchimerism. These cells often belong to stem cell or immune cell lineages. The long-term effects of fetal microchimerism are likely mixed, potentially depending on the amount of fetal cells transferred, fetal-maternal histocompatibility and fetal cell-specific properties. Both human and animal data indicate that fetal-origin cells partake in tissue repair and may benefit maternal health overall. On the other hand, these cells have been implicated in inflammatory diseases by studies showing increased fetal microchimerism in women with autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. During pregnancy, preeclampsia is associated with increased cell-transfer between the mother and fetus, and an increase in immune cell subsets. In the current review, we discuss potential mechanisms of transplacental transfer, including passive leakage across the compromised diffusion barrier and active recruitment of cells residing in the placenta or fetal circulation. Within the conceptual framework of the two-stage model of preeclampsia, where syncytiotrophoblast stress is a common pathophysiological pathway to maternal and fetal clinical features of preeclampsia, we argue that microchimerism may represent a mechanistic link between stage 1 placental dysfunction and stage 2 maternal cardiovascular inflammation and endothelial dysfunction. Finally, we postulate that fetal microchimerism may contribute to the known association between placental syndromes and increased long-term maternal cardiovascular disease risk. Fetal microchimerism research represents an exciting opportunity for developing new disease biomarkers and targeted prophylaxis against maternal diseases.

Carcinoma-associated fibroblast-like tumor cells remodel the Ewing sarcoma tumor microenvironment

Tumor heterogeneity is a major driver of cancer progression. In epithelial-derived malignancies, carcinoma-associated fibroblasts (CAFs) contribute to tumor heterogeneity by depositing extracellular matrix (ECM) proteins that dynamically remodel the tumor microenvironment (TME). Ewing sarcomas (EwS) are histologically monomorphous, mesenchyme-derived tumors that are devoid of CAFs. Here we identify a previously uncharacterized subpopulation of transcriptionally distinct EwS tumor cells that deposit pro-tumorigenic ECM. Single cell analyses revealed that these CAF-like cells differ from bulk EwS cells by their upregulation of a matrisome-rich gene signature that is normally repressed by EWS::FLI1, the oncogenic fusion transcription factor that underlies EwS pathogenesis. Further, our studies showed that ECM-depositing tumor cells express the cell surface marker CD73, allowing for their isolation ex vivo and detection in situ. Spatial profiling of tumor xenografts and patient biopsies demonstrated that CD73 ⁺ EwS cells and tumor cell-derived ECM are prevalent along tumor borders and invasive fronts. Importantly, despite loss of EWS::FLI1-mediated gene repression, CD73 ⁺ EwS cells retain expression of EWS::FLI1 and the fusion-activated gene signature, as well as tumorigenic and proliferative capacities. Thus, EwS tumor cells can be reprogrammed to adopt CAF-like properties and these transcriptionally and phenotypically distinct cell subpopulations contribute to tumor heterogeneity by remodeling the TME.

Abstract 3531: Discrete extracellular matrix-secreting tumor cell subpopulations remodel the Ewing sarcoma tumor microenvironment to promote invasion

Ewing sarcoma (EwS) cells exist along a neuro-mesenchymal transcriptional continuum that is largely determined by transcriptional activity of the EWS::FLI1 fusion oncoprotein. Although EWS::FLI1-low state cells are more metastatic in experimental models, the role of these cells in established EwS tumor ecosystems is unknown. Here we have leveraged multimodal single-cell sequencing, spatial transcriptomics, and immunohistochemical profiling to characterize EwS cell subpopulations in cell lines, PDX models, and patient tumors. We identify CD73 as a marker of mesenchymal-high state EwS cells and show that CD73+ tumor cells share properties of experimentally-induced EWS::FLI1-low cells including altered cytoskeletons, enhanced migration and invasion, and increased expression of EWS::FLI1-repressed genes. However, CD73+ cells retain proliferative capacity and do not down-regulate the fusion or the EWS::FLI1-activated signature. Instead, CD73+ EwS cells selectively express a gene signature that is enriched in extracellular matrix (ECM) genes. Examination of xenograft and EwS patient biopsies confirms the existence of subpopulations of spatially and transcriptionally distinct ECM-producing tumor cells and shows them to be more prevalent in infiltrating regions. Importantly, the local tumor microenvironment (TME) surrounding these cells is rich in tumor-derived TNC, SPARC, and biglycan, ECM proteins that have been widely implicated in cancer metastatic progression. Significantly, CD73+ EwS cells also upregulate expression of ECM-sensing genes, including ITGA5 and ITGB1, suggesting potential to activate autocrine feedback loops. In support of this, interrupting outside-in ECM:integrin signaling cascades, through pharmacologic inhibition of FAK or SRC pathways, strongly reduces the invasive properties of CD73+ tumor spheroids in 3D collagen. Together these studies confirm the presence and functional importance of transcriptionally distinct tumor cell subpopulations in established EwS tumor ecosystems. In particular, our data reveal that highly mesenchymal tumor cells both generate and respond to pro-metastatic ECM proteins to support invasion. Studies are ongoing to determine the role of tumor cell-derived ECM on EwS progression and treatment resistance.

Citation Format: Emma D. Wrenn, April A. Apfelbaum, Shireen Ganapathi, Erin R. Rudzinski, Xuemei Deng, Nicolas Garcia, Katherine Braun, Trisha Lipson, Shruti Bhise, Sami B. Kanaan, Olivia Waltner, Erika Newman, Scott Furlan, Elizabeth R. Lawlor. Discrete extracellular matrix-secreting tumor cell subpopulations remodel the Ewing sarcoma tumor microenvironment to promote invasion. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3531.

Umbilical Cord Maternal Microchimerism in Normal and Preeclampsia Pregnancies

Bidirectional exchange of cells between mother and fetus establishes microchimerism (Mc). Mc can persist for decades and is associated with later-life health and disease. Greater fetal Mc is detected in the maternal compartment in preeclampsia (PE), but whether maternal Mc (MMC) in umbilical cord blood (CB) is altered in PE is unknown. We evaluated MMc in CB from normal and PE pregnancies. DNA from CB mononuclear cells following placental delivery (n = 36 PE, n = 37 controls) and maternal blood was extracted and genotyped. MMc, quantified by qPCR assays targeting maternal-specific nonshared polymorphisms in CB, was compared using logistic and negative binomial regression models. Clinically and statistically relevant confounders were included, and included the total number of cell equivalents tested, gravidity, mode of delivery, birthweight, and fetal sex. PE participants delivered at earlier gestational ages, with higher Cesarean rates, and lower infant birthweights. CB MMc detection was similar between PE and controls (52.8% vs. 51.3%, respectively, p = 0.90) and unchanged after adjustment for confounders. MMc concentration was not different between groups (mean 73.7 gEq/105 gEq in PE vs. mean 22.8 gEq/105 in controls, p = 0.56), including after controlling for confounders (p = 0.64). There was no difference in CB MMc detection or concentration between PE and normal pregnancies, despite previously noted greater fetal Mc in the maternal compartment. This suggests possible differential transfer of cells at the maternal fetal interface in PE. Phenotypic evaluation of Mc cells may uncover underlying mechanisms for differential cellular exchange between mother and fetus in PE.

Markers of placental function correlate with prevalence and quantity of nucleated fetal cells in maternal circulation in normotensive term pregnancies

INTRODUCTION

Transplacental fetal cell transfer results in the engraftment of fetal-origin cells in the pregnant woman's body, a phenomenon termed fetal microchimerism. Increased fetal microchimerism measured decades postpartum is implicated in maternal inflammatory disease. Understanding which factors cause increased fetal microchimerism is therefore important. During pregnancy, circulating fetal microchimerism and placental dysfunction increase with increasing gestational age, particularly towards term. Placental dysfunction is reflected by changes in circulating placenta-associated markers, specifically placental growth factor (PlGF), decreased by several 100 pg/mL, soluble fms-like tyrosine kinase-1 (sFlt-1), increased by several 1000 pg/mL, and the sFlt-1/PlGF ratio, increased by several 10 (pg/mL)/(pg/mL). We investigated whether such alterations in placenta-associated markers correlate with an increase in circulating fetal-origin cells.

MATERIAL AND METHODS

We included 118 normotensive, clinically uncomplicated pregnancies (gestational age 37+1 up to 42+2 weeks' gestation) pre-delivery. PlGF and sFlt-1 (pg/mL) were measured by Elecsys® Immunoassays. We extracted DNA from maternal and fetal samples and genotyped four human leukocyte antigen loci and 17 other autosomal loci. Paternally inherited, unique fetal alleles served as polymerase chain reaction (PCR) targets for detecting fetal-origin cells in maternal buffy coat. Fetal-origin cell prevalence was assessed by logistic regression, and quantity by negative binomial regression. Statistical exposures included gestational age (weeks), PlGF (100 pg/mL), sFlt-1 (1000 pg/mL) and the sFlt-1/PlGF ratio (10 (pg/mL)/(pg/mL)). Regression models were adjusted for clinical confounders and PCR-related competing exposures.

RESULTS

Gestational age was positively correlated with fetal-origin cell quantity (DRR = 2.2, P = 0.003) and PlGF was negatively correlated with fetal-origin cell prevalence (odds ratio [OR]₁₀₀ = 0.6, P = 0.003) and quantity (DRR₁₀₀ = 0.7, P = 0.001). The sFlt-1 and the sFlt-1/PlGF ratios were positively correlated with fetal-origin cell prevalence (OR₁₀₀₀ = 1.3, P = 0.014 and OR₁₀ = 1.2, P = 0.038, respectively), but not quantity (DRR₁₀₀₀ = 1.1, P = 0.600; DRR₁₀ = 1.1, P = 0.112, respectively).

CONCLUSIONS

Our results suggest that placental dysfunction as evidenced by placenta-associated marker changes, may increase fetal cell transfer. The magnitudes of change tested were based on ranges in PlGF, sFlt-1 and the sFlt-1/PlGF ratio previously demonstrated in pregnancies near and post-term, lending clinical significance to our findings. Our results were statistically significant after adjusting for confounders including gestational age, supporting our novel hypothesis that underlying placental dysfunction potentially is a driver of increased fetal microchimerism.

Increased fetal microchimerism in immune and stem cell subsets in preeclampsia

PROBLEM

Preeclampsia (PE) is associated with an increased risk of maternal cardiovascular disease (CVD), however, it is unclear whether this is due to shared underlying physiology or changes which occur during the disease process. Fetal microchimerism (FMc) within the maternal circulation can durably persist decades after pregnancy, is known to occur at greater frequency in PE, and can potentially affect local and systemic immune programming, thus changes in cellular FMc may provide a mechanism for long-term health outcomes associated with PE.

METHOD OF STUDY

We investigated whether PE is associated with alterations in FMc immune and stem cell populations. We analyzed maternal peripheral blood mononuclear cells (PBMC) from PE cases (n = 16) and matched controls from normal pregnancies (n = 16), from which immune and stem cell subsets were isolated by flow cytometry. Genomic DNA was extracted from total PMBC and individual cell subsets, and FMc frequency was quantified by quantitative polymerase chain reaction assays targeting a fetal-specific non-shared polymorphism identified from family genotyping.

RESULTS

There was a significant increase in FMc concentration in immune cell subsets in PE cases compared to controls, predominantly in B cell, and NK cell lymphocyte populations. There was no significant difference in FMc frequency or concentration within the stem cell population between PE and controls.

CONCLUSIONS

The altered concentrations of immune cells within FMc in the maternal blood provides a potential mechanism for the inflammation which occurs during PE to induce long-lasting changes to the maternal immune system and may potentially promote chronic maternal disease.

Factors influencing maternal microchimerism throughout infancy and its impact on infant T cell immunity

Determinants of the acquisition and maintenance of maternal microchimerism (MMc) during infancy and the impact of MMc on infant immune responses are unknown. We examined factors which influence MMc detection and level across infancy and the effect of MMc on T cell responses to BCG vaccination in a cohort of HIV exposed, uninfected and HIV unexposed infants in South Africa. MMc was measured in whole blood from 58 infants using a panel of quantitative PCR assays at day one and 7, 15, and 36 weeks of life. Infants received BCG at birth, and selected whole blood samples from infancy were stimulated in vitro with BCG and assessed for polyfunctional CD4+ T cell responses. MMc was present in most infants across infancy with levels ranging from 0-1,193/100,000 genomic equivalents and was positively impacted by absence of maternal HIV, maternal-infant HLA compatibility, infant female sex, and exclusive breastfeeding. Initiation of maternal antiretroviral therapy prior to pregnancy partially restored MMc levels in HIV exposed, uninfected infants. Birth MMc was associated with an improved polyfunctional CD4+ T cell response to BCG. These data emphasize that both maternal and infant factors influence MMc, which may subsequently impact infant T cell responses.

Cross-decoration of dendritic cells by non-inherited maternal antigen-containing extracellular vesicles: Potential mechanism for PD-L1-based tolerance in cord blood and organ transplantation

Exposure to non-inherited maternal antigens (NIMA) during the fetal period induces lifelong split tolerance to grafts expressing these allo-antigens. In adult mice, the production of extracellular vesicles (EVs) from maternal microchimeric cells causes cross-decoration (XD) of offspring dendritic cells (DC) with NIMA and upregulation of PD-L1, contributing to NIMA tolerance. To see how this may apply to humans, we tested NIMA acquisition by fetal DCS in human cord blood. The average percentage of NIMA-XD among total DCs was 2.6% for myeloid and 4.5% for Plasmacytoid DC. These cells showed higher PD-L1 expression than their non-XD counterparts (mDC: p = .0016; pDC: p = .024). We detected CD9+ EVs bearing NIMA and PD-L1 in cord blood. To determine if this immune regulatory mechanism persists beyond the pregnancy, we analyzed NIMA-expressing kidney and liver transplant recipients. We found donor antigen XD DCs in peripheral blood and graft-infiltrating DCs. As in cord blood, the pattern of donor antigen expression was punctate, and PD-L1 expression was upregulated, likely due to both protein and miRNA acquired from EV. Our findings support a mechanism for split tolerance to NIMAs that develops during pregnancy and is recapitulated in adult transplant recipients.

Quantification of Maternal Microchimeric Cells in the Liver of Children With Biliary Atresia

ABSTRACT

Biliary atresia (BA) is a rare disorder of unknown etiology. There is a debate as to whether maternal microchimerism plays a significant role in the development of BA or in graft tolerance after liver transplantation. Here, we performed quantitative-PCR-based assays for liver tissues of children with BA and other diseases. Maternal cells were detected in 4/13 and 1/3 of the BA and control groups, respectively. The estimated number of maternal cells ranged between 0 and 34.7 per 106 total cells. The frequency and severity of maternal microchimerism were similar between the BA and control groups, and between patients with and without acute rejection of maternal grafts. These results highlight the high frequency of maternal microchimerism in the liver. This study provides no evidence for roles of microchimerism in the etiology of BA or in graft tolerance. Thus, the biological consequences of maternal microchimerism need to be clarified in future studies.

Ultrasensitive Quantitation of Genomic Chimerism by Single-Molecule Molecular Inversion Probe Capture and High-Throughput Sequencing of Copy Number Deletion Polymorphisms

Genomic chimerism represents co-existing cells with different genotypes and has diagnostic significance in transplant engraftment monitoring, residual cancer detection, and other contexts. We previously described an approach to chimerism detection by interrogating variably present or absent genomic loci using single-molecule molecular inversion probes (smMIPs) and next-generation sequencing, which provided ultrasensitive limits of detection (<1 in 10,000 cells) but was not reliably quantitative. Herein, smMIP testing was modified to accurately quantitate chimeric cells by incorporating copy number neutral control loci for data normalization and computationally modeling cell mixtures from individual-specific genotypes. Data demonstrate precision and accuracy over three orders of magnitude (0.01% to 50% chimerism). Seventy hematopoietic stem cell transplant specimens from single (n = 42) or double (n = 28) donors were evaluated, benchmarking smMIP against conventional variable number tandem repeat (VNTR) analysis and an unrelated, ultrasensitive polymorphism-specific quantitative PCR (PS-qPCR) assay. Quantitative concordance of all three assays was high (P < 0.0005, Pearson correlation coefficient), although smMIP correlated better with VNTR testing than PS-qPCR. smMIP and PS-qPCR collectively identified low-level chimerism in all specimens testing negative by VNTR (n = 41 and n = 45 of 48 specimens, respectively). This work demonstrates the feasibility of smMIP-based chimerism testing for quantitative and ultrasensitive measurement of genomic chimerism at practical levels approaching one in one million cells, and cross-validates the approach.

Circulating maternal chimeric cells have an impact on the outcome of biliary atresia

INTRODUCTION

We aimed to quantify the DNA of maternal chimeric (MC) cells in the peripheral blood of the BA patients and investigated the impact on the outcome.

METHODS

Patients with progressive jaundice because of no bile flow, which necessitated liver transplantation, or who showed inadequate bile flow with or without episodes of cholangitis and progressive hepatic fibrosis and portal hypertension were classified into the poor group. Those with adequate bile flow with completely normal liver function tests beyond 2 years were classified into the good group. The qPCR were separately carried out in buffy coat samples and plasma samples, targeting the non-inherited maternal HLA alleles in the DNA samples.

RESULTS

MC-DNA was present in the buffy coat (10-328 gEq per 10⁶ host cells) in seven patients. There was no MC-DNA in the remaining five patients. MC-DNA (214-15,331 gEq per 10⁶ host cells) was observed in the plasma of five patients. The quantity of MC-DNA in the buffy coat showed a significant difference between the two prognostic groups (p = 0.018), whereas there was no significant difference in the quantity of MC-DNA in plasma (p = 0.205). MC-DNA in the buffy coat was significantly associated with the outcome (p = 0.028), whereas MC-DNA in the plasma did not influence the outcome (p = 0.56).

CONCLUSIONS

Poor outcomes in BA were correlated with circulating maternal chimeric lymphocytes.

Predictors of maternal-origin microchimerism in young women in the Philippines

OBJECTIVES

Microchimerism is the presence of a small quantity of cells or DNA from a genetically distinct individual. This phenomenon occurs with bidirectional maternal-fetal exchange during pregnancy. Microchimerism can persist for decades after delivery and have long-term health implications. However, little is known about why microchimerism is detectable at varying levels in different individuals. We examine the variability and the following potential determinants of maternal-origin microchimerism (MMc) in young women in the Philippines: gestational duration (in utero exposure to MMc), history of being breastfed (postpartum exposure to MMc), maternal telomere length (maternal cells' ability to replicate and persist), and participant's pregnancies in young adulthood (effect of adding fetal-origin microchimerism to preexisting MMc).

MATERIALS AND METHODS

Data are from the Cebu Longitudinal Health and Nutrition Survey, a population-based study of infant feeding practices and long-term health outcomes. We quantified MMc using quantitative PCR (qPCR) in 89 female participants, ages 20-22, and analyzed these data using negative binomial regression.

RESULTS

In a multivariate model including all predictors, being breastfed substantially predicted decreased MMc (detection rate ratio = 0.15, p = 0.007), and there was a trend of decreasing MMc in participants who had experienced more pregnancies (detection rate ratio = 0.55, p = 0.057).

DISCUSSION

These results might be explained by breastfeeding having lasting impact on immune regulatory networks, thus reducing MMc persistence. MMc may also decrease in response to the introduction of fetal-origin microchimerism with pregnancies experienced in adulthood.

Cord blood maternal microchimerism following unrelated cord blood transplantation

Cord blood transplantation (CBT) is associated with low risk of leukemia relapse. Mechanisms underlying antileukemia benefit of CBT are not well understood, however a previous study strongly but indirectly implicated cells from the mother of the cord blood (CB) donor. A fetus acquires a small number of maternal cells referred to as maternal microchimerism (MMc) and MMc is sometimes detectable in CB. From a series of 95 patients who underwent double or single CBT at our center, we obtained or generated HLA-genotyping of CB mothers in 68. We employed a technique of highly sensitive HLA-specific quantitative-PCR assays targeting polymorphisms unique to the CB mother to assay CB-MMc in patients post-CBT. After additional exclusion criteria, CB-MMc was evaluated at multiple timepoints in 36 patients (529 specimens). CB-MMc was present in 7 (19.4%) patients in bone marrow, peripheral blood, innate and adaptive immune cell subsets, and was detected up to 1-year post-CBT. Statistical trends to lower relapse, mortality, and treatment failure were observed for patients with vs. without CB-MMc post-CBT. Our study provides proof-of-concept that maternal cells of the CB graft can be tracked in recipients post-CBT, and underscore the importance of further investigating CB-MMc in sustained remission from leukemia following CBT.

Mosaicism of XX and XXY cells accounts for high copy number of Toll like Receptor 7 and 8 genes in peripheral blood of men with Rheumatoid Arthritis

The X chromosome, hemizygous in males, contains numerous genes important to immunological and hormonal function. Alterations in X-linked gene dosage are suspected to contribute to female predominance in autoimmunity. A powerful example of X-linked dosage involvement comes from the BXSB murine lupus model, where the duplication of the X-linked Toll-Like Receptor 7 (Tlr7) gene aggravates autoimmunity in male mice. Such alterations are possible in men with autoimmune diseases. Here we showed that a quarter to a third of men with rheumatoid arthritis (RA) had significantly increased copy numbers (CN) of TLR7 gene and its paralog TLR8. Patients with high CN had an upregulated pro-inflammatory JNK/p38 signaling pathway. By fluorescence in situ hybridization, we further demonstrated that the increase in X-linked genes CN was due to the presence of an extra X chromosome in some cells. Men with RA had a significant cellular mosaicism of female (46,XX) and/or Klinefelter (47,XXY) cells among male (46,XY) cells, reaching up to 1.4% in peripheral blood. Our results present a new potential trigger for RA in men and opens a new field of investigation particularly relevant for gender-biased autoimmune diseases.

Fetal microchimerism by mode of delivery: a prospective cohort study

OBJECTIVE

To compare fetal microchimerism (FMc) in pregnancies with uncomplicated vaginal delivery (VD) versus caesarean delivery (CD).

DESIGN

Prospective cohort study.

SETTING

University of Washington and Fred Hutchinson Cancer Research Center, USA.

POPULATION

Women delivering singleton pregnancies without pertinent antenatal complications with uncomplicated deliveries (n = 36).

METHODS

We collected maternal predelivery, postdelivery and umbilical cord blood for each mother-baby pair. Following maternal and fetal genotyping, FMc was measured with quantitative polymerase chain reaction assays targeting fetus-specific polymorphisms. Quantification of FMc is expressed as genome equivalents (gEq) of fetal DNA/100 000 total gEq tested. FMc detection was evaluated by logistic regression while controlling for total number of cell equivalents tested and clinically relevant covariates. FMc concentrations were compared using negative binomial regression while controlling for the same covariates and predelivery FMc positivity.

MAIN OUTCOME MEASURE

Detection and concentration of FMc by mode of delivery.

RESULTS

Twenty-four mother-baby pairs had a VD and 12 had a CD. Postdelivery FMc detection was higher following CD than after VD (58.3% versus 16.7%, P = 0.02). After controlling for covariates, the likelihood of postdelivery FMc detection was almost nine-fold higher after CD than VD (odds ratio 8.8, 95% CI 1.6-47.6; P = 0.01). With respect to postdelivery FMc concentration, the detection rate ratio for CD versus VD in the adjusted negative binomial regression model was 14.7 (95% CI 3.2-66.8; P = 0.001).

CONCLUSION

Postdelivery peripheral FMc detection and concentration are significantly higher after CD than after VD. As FMc is associated with long-term maternal health, our findings suggest that the mode of delivery may impact this risk.

TWEETABLE ABSTRACT

Greater fetal microchimerism found in maternal blood following caesarean delivery compared with vaginal delivery.

Soluble HLA-G Expression Inversely Correlates With Fetal Microchimerism Levels in Peripheral Blood From Women With Scleroderma

Women with scleroderma (SSc) maintain significantly higher quantities of persisting fetal microchimerism (FMc) from complete or incomplete pregnancies in their peripheral blood compared to healthy women. The non-classical class-I human leukocyte antigen (HLA) molecule HLA-G plays a pivotal role for the implantation and maintenance of pregnancy and has often been investigated in offspring from women with pregnancy complications. However data show that maternal HLA-G polymorphisms as well as maternal soluble HLA-G (sHLA-G) expression could influence pregnancy outcome. Here, we aimed to investigate the underlying role of maternal sHLA-G expression and HLA-G polymorphisms on the persistence of FMc. We measured sHLA-G levels by enzyme linked immunosorbent assay in plasma samples from 88 healthy women and 74 women with SSc. Male Mc was quantified by DYS14 real-time PCR in blood samples from 58 women who had previously given birth to at least one male child. Furthermore, eight HLA-G 5'URR/3'UTR polymorphisms, previously described as influencing HLA-G expression, were performed on DNA samples from 96 healthy women and 106 women with SSc. Peripheral sHLA-G was at lower concentration in plasma from SSc (76.2 ± 48.3 IU/mL) compared to healthy women (117.5 ± 60.1 IU/mL, p < 0.0001), independently of clinical subtypes, autoantibody profiles, disease duration, or treatments. Moreover, sHLA-G levels were inversely correlated to FMc quantities (Spearman correlation, p < 0.01). Finally, women with SSc had lower sHLA-G independently of the eight HLA-G 5'URR/3'UTR polymorphisms, although they were statistically more often homozygous than heterozygous for HLA-G polymorphism genotypes -716 (G/T), -201 (G/A), 14 bp (ins/del), and +3,142 (G/A) than healthy women. In conclusion, women with SSc display less sHLA-G expression independently of the eight HLA-G polymorphisms tested. This decreased production correlates with higher quantities of persisting FMc commonly observed in blood from SSc women. These results shed some lights on the contribution of the maternal HLA-G protein to long-term persistent fetal Mc and initiate new perspectives in this field.

Cells from a vanished twin as a source of microchimerism 40 years later

We report the case of a 40-year-old man diagnosed with a scleroderma-like disease. Clinical similarities with graft versus host disease prompted initial testing for chimerism employing fluorescence in situ hybridization (FISH). Female cells were observed within peripheral blood mononuclear cells from the patient.Because maternal cells have been detected in healthy immunologically competent adults and patients with autoimmune conditions, we hypothesized that these cells were of maternal origin. Contrary to our expectations, HLA-specific quantitative PCR (QPCR) ruled out maternal microchimerism. However, HLA-specific QPCR testing was positive for the paternal HLA haplotype that the patient did not inherit. We reasoned that the most likely origin of chimerism with non-inherited paternal HLA alleles was from an unrecognized "vanished" twin. The patient had never received a blood transfusion.This report suggests that cells from a vanished twin are a possible source of chimerism. The frequency of chimerism from this source is not yet known and whether the scleroderma-like disease observed in the patient is anecdotal or implies a potential association with autoimmune disease remains to be elucidated.

Maternal Microchimerism Predicts Increased Infection but Decreased Disease due to Plasmodium falciparum During Early Childhood

Background

A mother's infection with placental malaria (PM) can affect her child's susceptibility to malaria, although the mechanism remains unclear. The fetus acquires a small amount of maternal cells and DNA known as maternal microchimerism (MMc), and we hypothesized that PM increases MMc and that MMc alters risk of Plasmodium falciparum malaria during infancy.

Methods

In a nested cohort from Muheza, Tanzania, we evaluated the presence and level of cord blood MMc in offspring of women with and without PM. A maternal-specific polymorphism was identified for each maternal-infant pair, and MMc was assayed by quantitative polymerase chain reaction. The ability of MMc to predict malaria outcomes during early childhood was evaluated in longitudinal models.

Results

Inflammatory PM increased the detection rate of MMc among offspring of primigravidae and secundigravidae, and both noninflammatory and inflammatory PM increased the level of MMc. Detectable MMc predicted increased risk of positive blood smear but, interestingly, decreased risk of symptomatic malaria and malaria hospitalization.

Conclusions

The acquisition of MMc may result in increased malaria infection but protection from malaria disease. Future studies should be directed at the cellular component of MMc, with attention to its ability to directly or indirectly coordinate anti-malarial immune responses in the offspring.

Newly Identified BRAF Mutation in Rheumatoid Arthritis

OBJECTIVE

Rheumatoid arthritis (RA)-associated autoantibodies include those directed at the kinase site of BRAF (v-Raf murine sarcoma viral oncogene homolog B1), a serine-threonine kinase involved in the MAPK signaling pathway. To understand anti-BRAF immunization, we sought to identify BRAF mutations in the peripheral blood lymphocytes (PBLs) of patients with RA.

METHODS

We first cloned the major BRAF region known for mutations in the pCR2.1 vector, using genomic DNA from the PBLs of 8 RA patients. For each patient, 100 clones were sequenced. In 5 of 8 patients, we detected a new BRAF mutation in 1 clone. The frequency of this new mutation was evaluated by droplet digital polymerase chain reaction in PBLs from RA patients and controls. To test whether p.Val600Ala influences the kinase activity of BRAF, we developed an in vitro assay based on phosphorylation of MEK-1, a major BRAF substrate.

RESULTS

A BRAF mutation, p.Val600Ala, was identified in 1 of 8,000 PBLs and 1 of 6,000 T lymphocytes from RA patients and in 1 of 12,500 PBLs and 1 of 12,500 T lymphocytes from controls. The BRAF p.Val600Ala mutation was not correlated with the presence of anti-BRAF autoantibodies. The p.Val600Ala mutation activated phosphorylation of MEK-1 in vitro.

CONCLUSION

Most RA patients have a p.Val600Ala mutation in the BRAF gene. This mutation activates the kinase activity of BRAF. The p.Val600Ala mutation could activate the MAPK pathway, leading to the activation of T lymphocytes.

Maternal microchimerism is prevalent in cord blood in memory T cells and other cell subsets, and persists post-transplant

Among reported advantages of umbilical cord blood (CB) in transplantation is lower leukemia relapse probability. Underlying cellular mechanisms of graft-vs.-leukemia (GVL) are thought to include a prominent role for T cells. Cells of the CB's mother, maternal microchimerism (MMc), were recently strongly, but indirectly, implicated in this GVL benefit. We assayed MMc directly and hypothesized benefit accrues from CB maternal T cells. MMc was quantified in 51 CBs and, within memory T, naïve T, B, NK cells, and monocytes in 27 CBs. Polymorphism-specific quantitative-PCR assays targeted maternal genotypes non-shared with CBs. Overall MMc was common and often at substantial levels. It was present in 52.9% of CB and in 33.3-55.6% of tested subsets. Remarkably, MMc quantities were greater in memory T cells than other subsets (p < 0.001). Expressed as genome equivalents (gEq) per 10⁵ total gEq tested (gEq/10⁵), memory T cell MMc averaged 850.2 gEq/10⁵, while other subset mean quantities were 13.8-30.1 gEq/10⁵. After adjustment for proportionality in CB, MMc remained 6-17 times greater in memory T, and 3-9 times greater in naïve T, vs. non-T-cell subsets. Further, CB-origin MMc was detected in vivo in a patient up to 6 mo post-transplantation, including among T cells. Overall, results revealed levels and phenotypes of CB MMc with potential relevance to CB transplantation and, more broadly, to offspring health.

Brief Report: HLA-DRB1, DQA1, and DQB1 in Juvenile-Onset Systemic Sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is a rare disease that is particularly uncommon in children. Specific HLA alleles have been associated with SSc in adults. This study was undertaken to investigate HLA class II alleles in juvenile-onset SSc.

METHODS

DRB1, DQA1, and DQB1 alleles were determined by DNA-based HLA typing. Analyses were conducted comparing Caucasian patients with juvenile-onset SSc (n = 76) to healthy Caucasian controls (n = 581).

RESULTS

Initial analyses focused on HLA class II associations previously reported in adult Caucasian patients with SSc. The frequency of DRB1*11 was not significantly increased in juvenile-onset SSc (22.4% of patients with juvenile-onset SSc versus 17.6% of controls; odds ratio [OR] 1.35, P = 0.34), nor were the specific DRB1*11:01 or *11:04 alleles. DQA1*05, a risk factor previously identified in adult men with SSc, was increased in patients with juvenile-onset SSc versus controls (57.9% versus 44.1%; OR 1.76, P = 0.027), as was DRB1*03 (34.2% versus 22.5%; OR 1.79, P = 0.031). Secondary analyses of all DRB1 allele groups revealed an association with DRB1*10 (10.5% of patients with juvenile-onset SSc versus 1.5% of controls; OR 7.48, P = 0.0002). As this is a new observation, correction was made for multiple comparisons of 13 different DRB1 allele groups; results nevertheless remained significant (P = 0.003). Also, a lower frequency of DRB1*01 was observed in patients with juvenile-onset SSc who were younger at disease onset (OR 0.06, P = 0.01) and in those with antibodies to topoisomerase (OR 0.14, P = 0.024).

CONCLUSION

Associations of HLA alleles with juvenile-onset SSc differed from associations with SSc in women, but were similar to associations with SSc in men. Additionally, a novel association with DRB1*10 was observed in children. The greatest proportion of genetic risk of SSc is contributed by the HLA complex, and the current study reveals the importance of the association of HLA class II genes in juvenile-onset SSc.

Anti-Ephrin Type-B Receptor 2 (EphB2) and Anti-Three Prime Histone mRNA EXonuclease 1 (THEX1) Autoantibodies in Scleroderma and Lupus

In a pilot ProtoArray analysis, we identified 6 proteins out of 9483 recognized by autoantibodies (AAb) from patients with systemic sclerosis (SSc). We further investigated the 6 candidates by ELISA on hundreds of controls and patients, including patients with Systemic Lupus Erythematosus (SLE), known for high sera reactivity and overlapping AAb with SSc. Only 2 of the 6 candidates, Ephrin type-B receptor 2 (EphB2) and Three prime Histone mRNA EXonuclease 1 (THEX1), remained significantly recognized by sera samples from SSc compared to controls (healthy or with rheumatic diseases) with, respectively, 34% versus 14% (P = 2.10⁻⁴) and 60% versus 28% (P = 3.10⁻⁸). Above all, EphB2 and THEX1 revealed to be mainly recognized by SLE sera samples with respectively 56%, (P = 2.10⁻¹⁰) and 82% (P = 5.10⁻¹³). As anti-EphB2 and anti-THEX1 AAb were found in both diseases, an epitope mapping was realized on each protein to refine SSc and SLE diagnosis. A 15-mer peptide from EphB2 allowed to identify 35% of SLE sera samples (N = 48) versus only 5% of any other sera samples (N = 157), including SSc sera samples. AAb titers were significantly higher in SLE sera (P<0.0001) and correlated with disease activity (p<0.02). We could not find an epitope on EphB2 protein for SSc neither on THEX1 for SSc or SLE. We showed that patients with SSc or SLE have AAb against EphB2, a protein involved in angiogenesis, and THEX1, a 3’-5’ exoribonuclease involved in histone mRNA degradation. We have further identified a peptide from EphB2 as a specific and sensitive tool for SLE diagnosis.

Evaluation of X Chromosome Inactivation with Respect to HLA Genetic Susceptibility in Rheumatoid Arthritis and Systemic Sclerosis

Background

Autoimmune diseases, including rheumatoid arthritis (RA) and systemic sclerosis (SSc) are characterized by a strong genetic susceptibility from the Human Leucocyte Antigen (HLA) locus. Additionally, disorders of epigenetic processes, in particular non-random X chromosome inactivation (XCI), have been reported in many female-predominant autoimmune diseases. Here we test the hypothesis that women with RA or SSc who are strongly genetically predisposed are less susceptible to XCI bias.

Methods

Using methylation sensitive genotyping of the androgen receptor (AR) gene, XCI profiles were performed in peripheral blood mononuclear cells from 161 women with RA, 96 women with SSc and 100 healthy women. HLA-DRB1 and DQB1 were genotyped. Presence of specific autoantibodies was documented for patients. XCI skewing was defined as having a ratio ≥ 80:20 of cells inactivating the same X chromosome.

Results

110 women with RA, 68 women with SSc, and 69 controls were informative for the AR polymorphism. Among them 40.9% of RA patients and 36.8% of SSc patients had skewed XCI compared to 17.4% of healthy women (P = 0.002 and 0.018, respectively). Presence of RA-susceptibility alleles coding for the “shared epitope” correlated with higher skewing among RA patients (P = 0.002) and such correlation was not observed in other women, healthy or with SSc. Presence of SSc-susceptibility alleles did not correlate with XCI patterns among SSc patients.

Conclusion

Data demonstrate XCI skewing in both RA and SSc compared to healthy women. Unexpectedly, skewed XCI occurs more often in women with RA carrying the shared epitope, which usually reflects severe disease. This reinforces the view that loss of mosaicism in peripheral blood may be a consequence of chronic autoimmunity.

Comparing HLA shared epitopes in French Caucasian patients with scleroderma

Although many studies have analyzed HLA allele frequencies in several ethnic groups in patients with scleroderma (SSc), none has been done in French Caucasian patients and none has evaluated which one of the common amino acid sequences, ⁶⁷FLEDR⁷¹, shared by HLA-DRB susceptibility alleles, or ⁷¹TRAELDT⁷⁷, shared by HLA-DQB1 susceptibility alleles in SSc, was the most important to develop the disease. HLA-DRB and DQB typing was performed for a total of 468 healthy controls and 282 patients with SSc allowing FLEDR and TRAELDT analyses. Results were stratified according to patient’s clinical subtypes and autoantibody status. Moreover, standardized HLA-DRß1 and DRß5 reverse transcriptase Taqman PCR assays were developed to quantify ß1 and ß5 mRNA in 20 subjects with HLA-DRB1*15 and/or DRB1*11 haplotypes. FLEDR motif is highly associated with diffuse SSc (χ² = 28.4, p<10−6) and with anti-topoisomerase antibody (ATA) production (χ² = 43.9, p<10−9) whereas TRAELDT association is weaker in both subgroups (χ² = 7.2, p = 0.027 and χ² = 14.6, p = 0.0007 respectively). Moreover, FLEDR motif- association among patients with diffuse SSc remains significant only in ATA subgroup. The risk to develop ATA positive SSc is higher with double dose FLEDR than single dose with respectively, adjusted standardised residuals of 5.1 and 2.6. The increase in FLEDR motif is mostly due to the higher frequency of HLA-DRB1*11 and DRB1*15 haplotypes. Furthermore, FLEDR is always carried by the most abundantly expressed ß chain: ß1 in HLA DRB1*11 haplotypes and ß5 in HLA-DRB1*15 haplotypes.

In French Caucasian patients with SSc, FLEDR is the main presenting motif influencing ATA production in dcSSc. These results open a new field of potential therapeutic applications to interact with the FLEDR peptide binding groove and prevent ATA production, a hallmark of severity in SSc.