Plasma DNA aberrations in systemic lupus erythematosus revealed by genomic and methylomic sequencing

Effects of blood-processing protocols on cell-free DNA fragmentomics in plasma: Comparisons of one- and two-step centrifugations

BACKGROUND

Cell-free DNA (cfDNA) fragmentomic characteristics are promising analytes with abundant physiological signals for non-invasive disease diagnosis and monitoring. Previous studies on plasma cfDNA fragmentomics commonly employed a two-step centrifugation process for removing cell debris, involving a low-speed centrifugation followed by a high-speed centrifugation. However, the effects of centrifugation conditions on the analysis of cfDNA fragmentome remain uncertain.

METHODS

We collected blood samples from 10 healthy individuals and divided each sample into two aliquots for plasma preparation with one- and two-step centrifugation processes. We performed whole genome sequencing (WGS) of the plasma cfDNA in the two groups and comprehensively compared the cfDNA fragmentomic features. Additionally, we reanalyzed the fragmentomic features of cfDNA from 16 healthy individuals and 16 COVID-19 patients, processed through one- and two-step centrifugation in our previous study, to investigate the impact of centrifugation on disease signals.

RESULTS

Our results showed that there were no significant differences observed in the characteristics of nuclear cfDNA, including size, motif diversity score (MDS) of end motifs, and genome distribution, between plasma samples treated with one- and two-step centrifugation. The cfDNA size shortening in COVID-19 patients was observed in plasma samples with one- and two-step centrifugation methods. However, we observed a significantly higher relative abundance and longer size of cell-free mitochondrial DNA (mtDNA) in the one-step samples compared to the two-step samples. This difference in mtDNA caused by the one- and two-step centrifugation methods surpasses the pathological difference between COVID-19 patients and healthy individuals.

CONCLUSIONS

Our findings indicate that one-step low-speed centrifugation is a simple and potentially suitable method for analyzing nuclear cfDNA fragmentation characteristics. These results offer valuable guidance for cfDNA research in various clinical scenarios.

Intranasal PAMAM-G3 scavenges cell-free DNA attenuating the allergic airway inflammation

Allergic airway inflammation (AAI), including allergic rhinitis (AR) and allergic asthma, is driven by epithelial barrier dysfunction and type 2 inflammation. However, the underlying mechanism remains uncertain and available treatments are constrained. Consequently, we aim to explore the role of cell-free DNA (cfDNA) in AAI and assess the potential alleviating effects of cationic polymers (CPs) through cfDNA elimination. Levels of cfDNA were evaluated in AR patients, allergen-stimulated human bronchial epithelium (BEAS-2B cells) and primary human nasal epithelium from both AR and healthy control (HC), and AAI murine model. Polyamidoamine dendrimers-generation 3 (PAMAM-G3), a classic type of cationic polymers, were applied to investigate whether the clearance of cfDNA could ameliorate airway epithelial dysfunction and inhibit AAI. The levels of cfDNA in the plasma and nasal secretion from AR were higher than those from HC (P < 0.05). Additionally, cfDNA levels in the exhaled breath condensate (EBC) were positively correlated with Interleukin (IL)-5 levels in EBC (R = 0.4191, P = 0.0001). Plasma cfDNA levels negatively correlated with the duration of allergen immunotherapy treatment (R = -0.4297, P = 0.006). Allergen stimulated cfDNA secretion in vitro (P < 0.001) and in vivo (P < 0.0001), which could be effectively scavenged with PAMAM-G3. The application of PAMAM-G3 inhibited epithelial barrier dysfunction in vitro and attenuated the development of AAI in vivo. This study elucidates that cfDNA, a promising biomarker for monitoring disease severity, aggravates AAI and the application of intranasal PAMAM-G3 could potentially be a novel therapeutic intervention for AAI. Allergen stimulates the secretion of cell-free DNA (cfDNA) in both human and mouse airway. Intranasal polyamidoamine dendrimers-generation 3 (PAMAM-G3) scavenges cfDNA and alleviates allergic airway inflammation.

Unique Interplay Between Antinuclear Antibodies and Nuclear Molecules in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease that primarily affects young women and causes a wide range of inflammatory manifestations. The hallmark of SLE is the production of antibodies to components of the cell nucleus (antinuclear antibodies [ANAs]). These antibodies can bind to DNA, RNA, and protein complexes with nucleic acids. Among ANAs, antibodies to DNA (anti-DNA) are markers for classification and disease activity, waxing and waning disease activity in many patients. In the blood, anti-DNA antibodies can bind to DNA to form immune complexes with two distinct roles in pathogenesis: (1) renal deposition to provoke nephritis and (2) stimulation of cytokine production following uptake into innate immune cells and interaction with internal nucleic acid sensors. These sensors are part of an internal host defense system in the cell cytoplasm that can respond to DNA from infecting organisms; during cell stress, DNA from nuclear and mitochondrial sources can also trigger these sensors. The formation of immune complexes requires a source of extracellular DNA in an immunologically accessible form. As shown in in vivo and in vitro systems, extracellular DNA can emerge from dead and dying cells in both a free and a particulate form. Neutrophils undergoing the process of NETosis can release DNA in mesh-like structures called neutrophil extracellular traps. In SLE, therefore, the combination of ANAs and immunologically active DNA can create new structures that can promote inflammation throughout the body as well as drive organ inflammation and damage.

Clinical algorithm model based on cfDNA to predict SLE disease activity

BACKGROUND

Circulating cell-free DNA (cfDNA) has been widely used as a new liquid-biopsy marker. Dysregulation of cfDNA has been found in patients with systemic lupus erythematosus (SLE). However, the detailed association between cfDNA and SLE has not been thoroughly studied.

METHODS

Plasma samples were collected from 88 patients with active SLE and 39 patients with inactive SLE. The cfDNA concentration was determined, and the length and distribution of cfDNA fragments were verified.

RESULTS

cfDNA concentrations were significantly higher in patients with active SLE than in patients with inactive SLE (0.4 [0.18-0.897] ng/µL vs 0.249 [0.144-0.431] ng/µL; p = .043). cfDNA fragments were enriched in the ranges of 153-198 bp and 300-599 bp. cfDNA concentrations were associated with the reduction of the anti-double-stranded DNA (dsDNA) antibodies titer (r = -0.301, p = .034). The presence of anti-U1 ribonucleoprotein (p = .012), anti-Sjogren syndrome A (p = .024), anti-dsDNA (p = .0208), and anti-nucleosome antibodies (p = .0382) might associate to the variation of cfDNA concentration. Reduced cfDNA concentration was associated with renal damage in active SLE patients (0.31 [0.11-0.73] ng/µL vs 0.65 [0.27-1.53] ng/µL; p = .009). The Active index, a combination model including cfDNA concentration and other clinical indices, had an area of 0.886 under the receiver operating characteristics curve for distinguishing active SLE. The Active index was positively correlated with the SLE disease activity index score (r = 0.6724, p < .0001).

CONCLUSIONS

Through systematic stratified analysis and clinical algorithm model, this study found that plasma cfDNA concentration is closely related to SLE disease severity, which has guiding significance for the future clinical application of cfDNA in SLE.

Heat inactivation does not alter host plasma cell-free DNA characteristics in infectious disease research

BACKGROUND

Cell-free DNA (cfDNA) is a promising analyte for non-invasive liquid biopsy, carrying abundant signatures for disease diagnosis and monitoring. In infectious disease researches, blood plasma samples are routinely heat-inactivated before proceeding with downstream analyses. However, the effects of heat inactivation on cfDNA fragmentomic analysis remain largely unclear, potentially introducing biases or altering the characteristics of cfDNA.

METHODS

We performed a comprehensive investigation of cfDNA concentrations and fragmentomics in 21 plasma samples from 7 healthy individuals, by comparing the sample group without the heat inactivation to those exposed to once or twice heat-inactivation at 56 °C for 30 min and following freeze-thaw.

RESULTS

Plasma samples with once and twice heat inactivation displayed no significant deviations in primary characteristics, including cfDNA concentrations, size profiles, end motif features, and genome-wide distributions, compared to samples without heat treatment.

CONCLUSIONS

Heat-inactivated cfDNA can be utilized for liquid biopsy in infectious disease researches, without substantial impact on cfDNA concentrations and fragmentomic properties. This study provides essential insights into the effects of heat inactivation on cfDNA properties and will contribute to the development of reliable non-invasive biomarkers for infectious disease.

Recent advances in the involvement of epigenetics in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a typical systemic autoimmune disease that manifests as skin rash, arthritis, lymphadenopathy, and multiple organ lesions. Epigenetics, including DNA methylation, histone modification, and non-coding RNA regulation, mainly affect the function and characteristics of cells through the regulation of gene transcription or translation. Increasing evidence indicates that there are a variety of complex epigenetic effects in patients with SLE, which interfere with the differentiation and function of T, and B lymphocytes, monocytes, and neutrophils, and enhance the expression of SLE-associated pathogenic genes. This paper summarizes our currently knowledge regarding pathogenesis of SLE, and introduces current advances in the epigenetic regulation of SLE from three aspects: immune function, inflammatory response, and lupus complications. We propose that epigenetic changes could be used as potential biomarkers and therapeutic targets of SLE.

Non-invasive prenatal testing: when results suggests maternal cancer

It is now well-established that non-invasive prenatal testing (NIPT), originally designed to screen cell-free DNA (cfDNA) in maternal blood for the presence of common fetal trisomies, can lead to incidental detection of occult maternal malignancies. Retrospective evaluations have demonstrated that the detection of multiple copy number alterations in cfDNA is particularly suggestive of an incipient tumor and that cancer detection rates not only depend on tumor biology but also on applied NIPT technologies and downstream diagnostic investigations. Since the identification of a maternal cancer in pregnancy has implications for both woman and the unborn child, prospective studies are needed to provide evidence on best clinical practices and on clinical utility in terms of patient outcomes.

The fragmentomic property of plasma cell-free DNA enables the non-invasive detection of diabetic nephropathy in patients with diabetes mellitus

Background

Diabetic nephropathy (DN) is one of the most prevalent complications of diabetes mellitus (DM). However, there is still a lack of effective methods for non-invasive diagnosis of DN in clinical practice. We aimed to explore biomarkers from plasma cell-free DNA as a surrogate of renal biopsy for the differentiation of DN patients from patients with DM.

Materials and methods

The plasma cell-free DNA (cfDNA) was sequenced from 53 healthy individuals, 53 patients with DM but without DN, and 71 patients with both DM and DN. Multidimensional features of plasma DNA were analyzed to dissect the cfDNA profile in the DM and DN patients and identify DN-specific cfDNA features. Finally, a classification model was constructed by integrating all informative cfDNA features to demonstrate the clinical utility in DN detection.

Results

In comparison with the DM patients, the DN individuals exhibited significantly increased cfDNA concentration in plasma. The cfDNA from the DN patients showed a distinct fragmentation pattern with an altered size profile and preferred motifs that start with "CC" in the cfDNA ending sites, which were associated with deoxyribonuclease 1 like 3 (DNASE1L3) expression in the kidney. Moreover, patients with DM or DN were found to carry more alterations in whole-genome cfDNA coverage when compared with healthy individuals. We integrated DN-specific cfDNA features (cfDNA concentration, size, and motif) into a classification model, which achieved an area under the receiver operating characteristic curve (AUC) of 0.928 for the differentiation of DN patients from DM patients.

Conclusion

Our findings showed plasma cfDNA as a reliable non-invasive biomarker for differentiating DN patients from DM patients. The utility of cfDNA in clinical practice in large prospective cohorts is warranted.

What helps define outcomes in persistent uninterpretable non-invasive prenatal testing: Maternal factors, fetal fraction or quality scores?

OBJECTIVES

To assess maternal characteristics and comorbidities in patients with persistent uninterpretable non-invasive prenatal testing (NIPT) and to evaluate the association with adverse pregnancy outcome in a general risk population.

METHODS

A retrospective cohort study (July 2017-December 2020) was conducted of patients with persistent uninterpretable NIPT samples. Maternal characteristics and pregnancy outcomes were compared with the general Belgian obstetric population.

RESULTS

Of the 148 patients with persistent uninterpretable NIPT, 37 cases were due to a low fetal fraction (LFF) and 111 due to a low quality score (LQS). Both groups (LFF, LQS) showed more obesity (60.6%, 42.4%), multiple pregnancies (18.9%, 4.5%) and more obstetrical complications. In the LQS group, a high rate of maternal auto-immune disorders (30.6%) was seen and hypertensive complications (17.6%), preterm birth (17.6%) and neonatal intensive care unit (NICU) admission (22%) were significantly increased. In the LFF group hypertensive complications (21.6%), gestational diabetes (20.6%), preterm birth (27%), SGA (25.6%), major congenital malformations (11.4%), c-section rate (51.4%) and NICU admission (34.9%) were significantly increased. Chromosomal abnormalities were not increased in both groups.

CONCLUSIONS

Patients with persistent uninterpretable NIPT have significantly more maternal obesity, comorbidities and adverse pregnancy outcome than the general population and should receive high-risk pregnancy care. Distinguishing between LFF and LQS optimizes counseling because maternal characteristics and pregnancy outcome differ between these groups.

Overview of Noninvasive Prenatal Testing (NIPT) for the Detection of Fetal Chromosome Abnormalities; Differences in Laboratory Methods and Scope of Testing

Although nearly all noninvasive prenatal testing is currently based on analyzing circulating maternal cell-free DNA, the technical methods usedvary considerably. We review the different methods. Based on validation trials and clinical experience, there are mostly relatively small differences in screening performance for trisomies 21, 18, and 13 in singleton pregnancies. Recent reports show low no-call rates for all methods, diminishing its importance when choosing a laboratory. However, method can be an important consideration for twin pregnancies, screening for sex chromosome abnormalities, microdeletion syndromes, triploidy, molar pregnancies, rare autosomal trisomies, and segmental imbalances, and detecting maternal chromosome abnormalities.

A Novel Paradigm for Non-Invasive Prenatal Genetic Screening: Trophoblast Retrieval and Isolation from the Cervix (TRIC)

As the prevalence of pregnancies with advanced maternal age increases, the risk of fetal chromosomal abnormalities is on the rise. Therefore, prenatal genetic screening and diagnosis have become essential elements in contemporary obstetrical care. Trophoblast retrieval and isolation from the cervix (TRIC) is a non-invasive procedure that can be utilized for prenatal genetic diagnosis. The method involves the isolation of fetal cells (extravillous trophoblasts) by transcervical sampling; along with its non-invasiveness, TRIC exhibits many other advantages such as its usefulness in early pregnancy at 5 weeks of gestation, and no interference by various fetal and maternal factors. Moreover, the trophoblast yields from TRIC can provide valuable information about obstetrical complications related to abnormal placentation even before clinical symptoms arise. The standardization of this clinical tool is still under investigation, and the upcoming advancements in TRIC are expected to meet the increasing need for a safe and accurate option for prenatal diagnosis.

Fragment length profiles of cancer mutations enhance detection of circulating tumor DNA in patients with early-stage hepatocellular carcinoma

BACKGROUND

Late detection of hepatocellular carcinoma (HCC) results in an overall 5-year survival rate of less than 16%. Liquid biopsy (LB) assays based on detecting circulating tumor DNA (ctDNA) might provide an opportunity to detect HCC early noninvasively. Increasing evidence indicates that ctDNA detection using mutation-based assays is significantly challenged by the abundance of white blood cell-derived mutations, non-tumor tissue-derived somatic mutations in plasma, and the mutational tumor heterogeneity.

METHODS

Here, we employed concurrent analysis of cancer-related mutations, and their fragment length profiles to differentiate mutations from different sources. To distinguish persons with HCC (PwHCC) from healthy participants, we built a classification model using three fragmentomic features of ctDNA through deep sequencing of thirteen genes associated with HCC.

RESULTS

Our model achieved an area under the curve (AUC) of 0.88, a sensitivity of 89%, and a specificity of 82% in the discovery cohort consisting of 55 PwHCC and 55 healthy participants. In an independent validation cohort of 54 PwHCC and 53 healthy participants, the established model achieved comparable classification performance with an AUC of 0.86 and yielded a sensitivity and specificity of 81%.

CONCLUSIONS

Our study provides a rationale for subsequent clinical evaluation of our assay performance in a large-scale prospective study.

Serological, fragmentomic, and epigenetic characteristics of cell-free DNA in patients with lupus nephritis

Objectives

The biological characteristics of plasma circulating cell-free DNA (cfDNA) are related to the pathogenesis of lupus nephritis (LN). The aim of this study was to explore the biological characteristics of cfDNA in patients with LN in terms of serology, fragment omics, and epigenetics, and to discuss the possibility of liquid biopsy for cfDNA as an alternative to conventional tissue biopsy.

Methods

cfDNA was extracted from plasma samples of 127 patients with systemic lupus erythematosus (64 with LN, 63 without LN). The cfDNA concentration was determined using the Qubit method. Next-generation sequencing cfDNA methylation profiling was performed for three LN patients and six non-LN patients. The methylation panel was designed based on data from The Cancer Genome Atlas cohort. The fragmentation index, motif score, and DELFI score were calculated to explore the fragmentation profile of cfDNA in patients with LN. Statistical and machine learning methods were used to select features to calculate the methylation scores of the samples.

Results

Patients with LN had significantly lower cfDNA concentrations (P = 0.0347) than those without LN. This may be associated with the presence of anti-double-stranded DNA antibodies (r = -0.4189; P = 0.0296). The mean DELFI score (proportion of short fragments of cfDNA) in patients with LN was significantly higher than that in patients without LN (P = 0.0238). Based on the pan-cancer data, 73, 66, 8, and 10 features were selected and used to calculate the methylation scores. The mean methylation scores of these features in patients with LN differed significantly from those in patients without LN (P = 0.0238).

Conclusions

The specificity of cfDNA in patients with LN was identified using serological, fragmentomic, and epigenetic analyses. The findings may have implications for the development of new molecular markers of LN.

Associations of genome-wide cell-free DNA fragmentation profiles with blood biochemical and hematological parameters in healthy individuals

Cell-free DNA (cfDNA), as a non-invasive approach, has been introduced in a wide range of applications, including cancer diagnosis/ monitoring, prenatal testing, and transplantation monitoring. Yet, studies of cfDNA fragmentomics in physiological conditions are lacking. In this study, we aim to explore the correlation of fragmentation patterns of cfDNA with blood biochemical and hematological parameters in healthy individuals. We addressed the impact of physiological variables and abnormal blood biochemical and hematological parameters on cfDNA fragment size distribution. We also figured and validated that hematological inflammation markers, including leukocyte, lymphocyte, neutrophil, and platelet distribution width as well as aspartate transaminase levels were significantly correlated with the genome-wide cfDNA fragmentation pattern. Our findings suggest that cfDNA fragmentation profiles were associated with physiological parameters related to cardiovascular risk factors, inflammatory response and hepatocyte injury, which may provide insights for further research on the potential role of cfDNA fragmentation in diagnosis and monitor of several disease.

The Effect of Elevated Alanine Transaminase on Non-invasive Prenatal Screening Failures

Objective

To determine the effects of alanine transaminase (ALT) levels on the screening failure rates or “no calls” due to low fetal fraction (FF) to obtain a result in non-invasive prenatal screening (NIPS).

Methods

NIPS by sequencing and liver enzyme measurements were performed in 7,910 pregnancies at 12–26 weeks of gestation. Univariate and multivariable regression models were used to evaluate the significant predictors of screening failure rates among maternal characteristics and relevant laboratory parameters.

Results

Of the 7,910 pregnancies that met the inclusion criteria, 134 (1.69%) had “no calls.” Multiple logistic regression analysis demonstrated that increased body mass index, ALT, prealbumin, albumin levels, and in vitro fertilization (IVF) conception rates were independently associated with screening failures. The test failure rate was higher (4.34 vs. 1.41%; P &lt; 0.001) in IVF pregnancies relative to those with spontaneous conceptions. Meanwhile, the screening failure rates increased with increasing ALT levels from 1.05% at ≤10 U/L to 3.73% at &gt;40 U/L. In particular, IVF pregnancies with an ALT level of &gt;40 U/L had a higher test failure rate (9.52%). Compared with that for an ALT level of ≤10 U/L, the adjusted odds ratio of “no calls” for ALT levels of 10–20, 21–40, and &gt;40 U/L was 1.204 [95% confidence interval (CI), 0.709–2.045], 1.529 (95% CI, 0.865–2.702), and 2.764 (95% CI, 1.500–5.093) (Ptrend &lt; 0.001), respectively.

Conclusions

Increased ALT and IVF conceptions were associated with a higher screening failure rates in NIPS. Therefore, a feasible strategy to adjust these factors to reduce the probability of “no calls” due to low FF would be of great clinical significance.

Cell-Free DNA Derived From Neutrophils Triggers Type 1 Interferon Signature in Neuromyelitis Optica Spectrum Disorder

Background and Objectives

Recently accumulating evidence suggests the pivotal role of type 1 interferon (IFN-1) signature in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD). However, the mechanism of the initial trigger that augments IFN-1 pathway in the peripheral immune system of NMOSD has yet to be elucidated.

Methods

Clinical samples were obtained from 32 patients with aquaporin-4 antibody–positive NMOSD and 23 healthy subjects. IFN-1 induction in peripheral blood mononuclear cells (PBMCs) by serum-derived cell-free DNA (cfDNA) was assessed in combination with blockades of DNA sensors in vitro. CfDNA fraction was analyzed for DNA methylation profiles by bisulfite sequencing, elucidating the cellular origin of cfDNA. The induction of neutrophil extracellular trap related cell death (NETosis) was further analyzed in NMOSD and control groups, and the efficacy of pharmacologic intervention of NETosis was assessed.

Results

Enhanced IFN-1 induction by cfDNA derived from NMOSD was observed in PBMCs with cofactor of LL37 antimicrobial peptide. DNase treatment, cGAS inhibitor, and Toll-like receptor 9 antagonist efficiently inhibited IFN-1 production. DNA methylation pattern of cfDNA in patients with NMOSD demonstrated that the predominant cellular source of cfDNA was neutrophils. Whole blood transcriptome analysis also revealed neutrophil activation in NMOSD. In addition, enhanced NETosis induction was observed with NMOSD-derived sera, and efficient pharmacologic inhibition of NETosis with dipyridamole was observed.

Discussion

Our study highlights the previously unrevealed role of cfDNA predominantly released by neutrophil in the induction of IFN-1 signature in NMOSD and further indicate a novel pharmacologic target in NMOSD.

Cell-Free DNA Fragmentomics in Liquid Biopsy

Cell-free DNA (cfDNA) in bodily fluids has rapidly transformed the development of noninvasive prenatal testing, cancer liquid biopsy, and transplantation monitoring. Plasma cfDNA consists of a mixture of molecules originating from various bodily tissues. The study of the fragmentation patterns of cfDNA, also referred to as ‘fragmentomics’, is now an actively pursued area of biomarker research. Clues that cfDNA fragmentation patterns might carry information concerning the tissue of origin of cfDNA molecules have come from works demonstrating that circulating fetal, tumor-derived, and transplanted liver-derived cfDNA molecules have a shorter size distribution than the background mainly of hematopoietic origin. More recently, an improved understanding of cfDNA fragmentation has provided many emerging fragmentomic markers, including fragment sizes, preferred ends, end motifs, single-stranded jagged ends, and nucleosomal footprints. The intrinsic biological link between activities of various DNA nucleases and characteristic fragmentations has been demonstrated. In this review, we focus on the biological properties of cell-free DNA unveiled recently and their potential clinical applications.

Bioinformatics analysis methods for cell-free DNA

As a kind of novel non-invasive marker for molecular detection, cell-free DNA (cfDNA) has potential value for the early diagnosis of diseases, prognosis assessment, and efficacy monitoring. The constant developments in molecular biology detection technologies have led to an increase in clinical studies on the use of cfDNA detection methods for patients, and many gratifying outcomes have been achieved. In this review, the contributions of bioinformatics tools to the study of cfDNA are well discussed. The focus of the review is on cfDNA identification signals, cfDNA identification methods, and the relationship of cfDNA with human diseases such as hepatic cancer, lung cancer, end-stage kidney disease, and ischemic stroke. The research significance and existing problems of using cfDNA as a biomarker for diseases are also discussed.

Factors Affecting the Fetal Fraction in Noninvasive Prenatal Screening: A Review

A paradigm shift in noninvasive prenatal screening has been made with the discovery of cell-free fetal DNA in maternal plasma. Noninvasive prenatal screening is primarily used to screen for fetal aneuploidies, and has been used globally. Fetal fraction, an important parameter in the analysis of noninvasive prenatal screening results, is the proportion of fetal cell-free DNA present in the total maternal plasma cell-free DNA. It combines biological factors and bioinformatics algorithms to interpret noninvasive prenatal screening results and is an integral part of quality control. Maternal and fetal factors may influence fetal fraction. To date, there is no broad consensus on the factors that affect fetal fraction. There are many different approaches to evaluate this parameter, each with its advantages and disadvantages. Different fetal fraction calculation methods may be used in different testing platforms or laboratories. This review includes numerous publications that focused on the understanding of the significance, influencing factors, and interpretation of fetal fraction to provide a deeper understanding of this parameter.

Methylation Markers in Cutaneous Melanoma: Unravelling the Potential Utility of Their Tracking by Liquid Biopsy

Malignant melanoma is the most serious, life-threatening form of all dermatologic diseases, with a poor prognosis in the presence of metastases and advanced disease. Despite recent advances in targeted therapy and immunotherapy, there is still a critical need for a better understanding of the fundamental mechanisms behind melanoma progression and resistance onset. Recent advances in genome-wide methylation methods have revealed that aberrant changes in the pattern of DNA methylation play an important role in many aspects of cancer progression, including cell proliferation and migration, evasion of cell death, invasion, and metastasization. The purpose of the current review was to gather evidence regarding the usefulness of DNA methylation tracking in liquid biopsy as a potential biomarker in melanoma. We investigated the key genes and signal transduction pathways that have been found to be altered epigenetically in melanoma. We then highlighted the circulating tumor components present in blood, including circulating melanoma cells (CMC), circulating tumor DNA (ctDNA), and tumor-derived extracellular vesicles (EVs), as a valuable source for identifying relevant aberrations in DNA methylation. Finally, we focused on DNA methylation signatures as a marker for tracking response to therapy and resistance, thus facilitating personalized medicine and decision-making in the treatment of melanoma patients.

Analysis of cf-mtDNA and cf-nDNA fragment size distribution using different isolation methods in BV-2 cell supernatant of starvation-induced autophagy

Fragment size distribution, the important biological properties of cell-free DNA (cfDNA), provides useful information required for diagnostic assay development. However, besides methodological discrepancies, it varies due to the complicated origins and occurrences of in vivo cfDNA. In addition, limited data are available concerning the cfDNA associated with autophagy and distributional difference between cf-mitochondrial DNA (cf-mtDNA) and cf-nuclear DNA (cf-nDNA) fragments. Here we developed an in vitro model of mouse microglial cell (BV-2) with starvation-induced autophagy, in which cfDNA was isolated from the cell supernatant by ultrafiltration (UF) and column-based commercial kit (CC), respectively. Using Agilent 2100 Bioanalyzer, a DNA ladder pattern as the presence of peaks corresponding to mono-, di- and tri-nucleosomes was clearly visualized both in isolation products of UF and CC. However, we also detected shorter fragments than mono-nucleosome by UF. In comparing the UF and CC, we found that the former produced the higher recovery efficiency for spiked-in DNA of shorter fragments than mono-nucleosome in both water and medium, but the latter was superior for spiked-in DNA fragments which were longer than or equal to mono-nucleosome in medium. Combined with these two isolation methods, we have observed that autophagy-associated cf-mtDNA and cf-nDNA were both highly enriched in <mono-nucleosomes fragments more than 71%, and showed no significant differences in the relative percentages for these four fragment sizes. These results have improved our understanding of the fragment size distribution of autophagy-derived cf-mtDNA and cf-nDNA in vitro, and might further develop application of cfDNA as a diagnostic tool.

NiPTUNE: an automated pipeline for noninvasive prenatal testing in an accurate, integrative and flexible framework

Noninvasive prenatal testing (NIPT) consists of determining fetal aneuploidies by quantifying copy number alteration from the sequencing of cell-free DNA (cfDNA) from maternal blood. Due to the presence of cfDNA of fetal origin in maternal blood, in silico approaches have been developed to accurately predict fetal aneuploidies. Although NIPT is becoming a new standard in prenatal screening of chromosomal abnormalities, there are no integrated pipelines available to allow rapid, accurate and standardized data analysis in any clinical setting. Several tools have been developed, however often optimized only for research purposes or requiring enormous amount of retrospective data, making hard their implementation in a clinical context. Furthermore, no guidelines have been provided on how to accomplish each step of the data analysis to achieve reliable results. Finally, there is no integrated pipeline to perform all steps of NIPT analysis. To address these needs, we tested several tools for performing NIPT data analysis. We provide extensive benchmark of tools performances but also guidelines for running them. We selected the best performing tools that we benchmarked and gathered them in a computational pipeline. NiPTUNE is an open source python package that includes methods for fetal fraction estimation, a novel method for accurate gender prediction, a principal component analysis based strategy for quality control and fetal aneuploidies prediction. NiPTUNE is constituted by seven modules allowing the user to run the entire pipeline or each module independently. Using two cohorts composed by 1439 samples with 31 confirmed aneuploidies, we demonstrated that NiPTUNE is a valuable resource for NIPT analysis.

Nuclease deficiencies alter plasma cell-free DNA methylation profiles

The effects of DNASE1L3 or DNASE1 deficiency on cell-free DNA (cfDNA) methylation were explored in plasma of mice deficient in these nucleases and in DNASE1L3-deficient humans. Compared to wild-type cfDNA, cfDNA in DNASE1L3-deficient mice was significantly hypomethylated, while cfDNA in DNASE1-deficient mice was hypermethylated. The cfDNA hypomethylation in DNASE1L3-deficient mice was due to increased fragmentation and representation from open chromatin regions (OCRs) and CpG islands (CGIs). These findings were absent in DNASE1-deficient mice, demonstrating the preference of DNASE1 to cleave in hypomethylated OCRs and CGIs. We also observed a substantial decrease of fragment ends at methylated CpGs in the absence of DNASE1L3, thereby demonstrating that DNASE1L3 prefers to cleave at methylated CpGs. Furthermore, we found that methylation levels of cfDNA varied by fragment size in a periodic pattern, with cfDNA of specific sizes being more hypomethylated and enriched for OCRs and CGIs. These findings were confirmed in DNASE1L3-deficient human cfDNA. Thus, we have found that nuclease-mediated cfDNA fragmentation markedly affects cfDNA methylation level on a genome-wide scale. This work provides a foundational understanding of the relationship between methylation, nuclease biology, and cfDNA fragmentation.

A practical guide to chimerism analysis: Review of the literature and testing practices worldwide

BACKGROUND AND PURPOSE

Currently there are no widely accepted guidelines for chimerism analysis testing in hematopoietic cell transplantation (HCT) patients. The objective of this review is to provide a practical guide to address key aspects of performing and utilizing chimerism testing results. In developing this guide, we conducted a survey of testing practices among laboratories that are accredited for performing engraftment monitoring/chimerism analysis by either the American Society for Histocompatibility & Immunogenetics (ASHI) and/or the European Federation of Immunogenetics (EFI). We interpreted the survey results in the light of pertinent literature as well as the experience in the laboratories of the authors.

RECENT DEVELOPMENTS

In recent years there has been significant advances in high throughput molecular methods such as next generation sequencing (NGS) as well as growing access to these technologies in histocompatibility and immunogenetics laboratories. These methods have the potential to improve the performance of chimerism testing in terms of sensitivity, availability of informative genetic markers that distinguish donors from recipients as well as cost.

SUMMARY

The results of the survey revealed a great deal of heterogeneity in chimerism testing practices among participating laboratories. The most consistent response indicated monitoring of engraftment within the first 30 days. These responses are reflective of published literature. Additional clinical indications included early detection of impending relapse as well as identification of cases of HLA-loss relapse.

More attention should be paid to pregnant women who fail non-invasive prenatal screening

OBJECTIVE

We discuss how to handle failure of first-pass non-invasive prenatal screening (NIPS) and investigate the pregnancy outcomes after second-pass failure.

METHODS

A total of 35,187 pregnant women underwent NIPS in a single center. Those who failed first-pass NIPS were re-tested after a repeat blood draw. Those who failed again were offered genetic counseling. We recorded antenatal data and pregnancy outcomes.

RESULTS

A total of 273 (0.78%) women failed the first test. On re-testing, 220 (80.59%) yielded reliable results and 53 failed the test again. Women with higher total cell-free DNA (cfDNA) levels evidenced a lower NIPS success rate (40%) and a higher incidence of adverse pregnancy outcomes.

CONCLUSIONS

Most women who failed first-pass NIPS yielded reliable results on repeat testing, especially those with lower fetal fraction. Higher concentrations of cfDNA in maternal plasma were associated with poorer pregnancy outcomes. Such women require special attention, thus early medical intervention, to avoid an adverse prognosis.

Time-Dependent Apparent Increase in dd-cfDNA Percentage in Clinically Stable Patients Between One and Five Years Following Kidney Transplantation

BACKGROUND

Donor-derived cell-free DNA (dd-cfDNA) is reportedly a valuable tool for graft surveillance following kidney transplantation (KTx). Possible changes in dd-cfDNA(%) reference values over time have not been evaluated. For long-term monitoring after KTx, changes in host cfDNA might represent a biasing factor in dd-cfDNA(%) determinations.

METHODS

Plasma samples were obtained (n = 929) 12-60 months after engraftment in a cross-sectional cohort of 303 clinically stable KTx recipients. Total cfDNA(copies/mL), dd-cfDNA(%), and dd-cfDNA(copies/mL) were determined using droplet-digital PCR. Stability of threshold values in these stable KTx recipients over time was assessed by 80th, 85th, and 90th quantile regression.

RESULTS

Upper percentiles of total cfDNA showed a significant decline of -1902, -3589, and -4753 cp/mL/log(month) (P = 0.014, <0.001, and 0.017, respectively), resulting in increasing dd-cfDNA(%) percentiles by 0.25, 0.46, and 0.72%/log(month) (P = 0.04, 0.001, and 0.002, respectively), with doubling of the 85th percentile value by 5 years. In contrast, dd-cfDNA(cp/mL) was stable during the observation period (P = 0.52, 0.29, and 0.39). In parallel increasing white blood cell counts and decreasing tacrolimus concentrations over time were observed. After 5 years, the median total cfDNA was still 1.6-fold (P < 0.001) higher in KTx recipients than in healthy controls (n = 135) and 1.4-fold (P < 0.001) higher than patients with other medical conditions (n = 364).

CONCLUSIONS

The time-dependent decrease of host cfDNA resulted in an apparent increase of dd-cfDNA fraction in stable KTx patients. For long-term surveillance, measurement of absolute dd-cfDNA concentrations appears to be superior to percentages to minimize false positive results.

The Nexus of cfDNA and Nuclease Biology

Cell-free DNA (cfDNA) is a widely used noninvasive biomarker for diagnosis and prognosis of multiple disease states. Emerging evidence suggests that cfDNA might not just be passive waste products of cell death but could have a physiological and pathological function in inflammation and autoimmunity. The balance of cfDNA generation and clearance may thus be vital in health and disease. In particular, plasma nuclease activity has been linked to multiple pathologies including cancer and systemic lupus erythematosus (SLE) and associated with profound changes in the nonrandom fragmentation of cfDNA. Lastly, in this review, we explore the effects of DNA fragmentation factor B (DFFB), DNASE1L3, and DNASE1 on cfDNA levels and their fragmentomic profiles, and what these recent insights reveal about the biology of cfDNA.

Autoantibody-mediated impairment of DNASE1L3 activity in sporadic systemic lupus erythematosus

Antibodies to double-stranded DNA (dsDNA) are prevalent in systemic lupus erythematosus (SLE), particularly in patients with lupus nephritis, yet the nature and regulation of antigenic cell-free DNA (cfDNA) are poorly understood. Null mutations in the secreted DNase DNASE1L3 cause human monogenic SLE with anti-dsDNA autoreactivity. We report that >50% of sporadic SLE patients with nephritis manifested reduced DNASE1L3 activity in circulation, which was associated with neutralizing autoantibodies to DNASE1L3. These patients had normal total plasma cfDNA levels but showed accumulation of cfDNA in circulating microparticles. Microparticle-associated cfDNA contained a higher fraction of longer polynucleosomal cfDNA fragments, which bound autoantibodies with higher affinity than mononucleosomal fragments. Autoantibodies to DNASE1L3-sensitive antigens on microparticles were prevalent in SLE nephritis patients and correlated with the accumulation of cfDNA in microparticles and with disease severity. DNASE1L3-sensitive antigens included DNA-associated proteins such as HMGB1. Our results reveal autoantibody-mediated impairment of DNASE1L3 activity as a common nongenetic mechanism facilitating anti-dsDNA autoreactivity in patients with severe sporadic SLE.

Factors associated with test failure in pregnant women undergoing cell-free DNA-based testing for fetal trisomy

OBJECTIVE

To investigate the factors associated with cell-free DNA test failure, and the optimal subsequent management of these pregnancies.

METHODS

This was a retrospective study of 27,363 singleton pregnancies undergoing cell-free DNA testing. Women with cell-free DNA test failure were divided into a high-risk group and a low-risk group according to their indications. The subsequent management and pregnancy outcomes of these women were followed up.

RESULTS

The rate of cell-free DNA test failure at the first sampling was 1.49%, and 78.4% of failures were due to a low fetal fraction. Of the 66 women who refused any subsequent management, an adverse pregnancy outcome was seen in 5 cases, all belonging to the high-risk group. Of the 13 low-risk women who chose second-trimester maternal serum screening, all obtained a low-risk maternal serum screening result and an unaffected pregnancy outcome. A redraw was chosen by 171 women, which yielded a result in 75.4% and their pregnancy outcomes were unaffected; 42 women had an uninformative result again and received an amniocentesis. As 158 women had an amniocentesis after the first sampling, this procedure was offered in 200 cases altogether. Abnormal genetic testing results were shown in six (3%, 6/200) cases, all in the high-risk group.

CONCLUSIONS

High-risk pregnant women with cell-free DNA test failure are at increased risk of adverse pregnancy outcomes. A second sampling for cell-free DNA test or maternal serum screening might be suggested to low-risk women. Invasive prenatal diagnosis should be offered to the high-risk patients, especially those with a second cell-free DNA test failure.

Performance of Cell-Free DNA Screening for Fetal Common Aneuploidies and Sex Chromosomal Abnormalities: A Prospective Study from a Less Developed Autonomous Region in Mainland China

To evaluate the performance of noninvasive prenatal screening (NIPS) in the detection of common aneuploidies in a population-based study, a total of 86,262 single pregnancies referred for NIPS were prospectively recruited. Among 86,193 pregnancies with reportable results, follow-up was successfully conducted in 1160 fetuses reported with a high-risk result by NIPS and 82,511 cases (95.7%) with a low-risk result. The screen-positive rate (SPR) of common aneuploidies and sex chromosome abnormalities (SCAs) provided by NIPS were 0.7% (586/83,671) and 0.6% (505/83,671), respectively. The positive predictive values (PPVs) for Trisomy 21, Trisomy 18, Trisomy 13 and SCAs were calculated as 89.7%, 84.0%, 52.6% and 38.0%, respectively. In addition, less rare chromosomal abnormalities, including copy number variants (CNVs), were detected, compared with those reported by NIPS with higher read-depth. Among these rare abnormalities, only 23.2% (13/56) were confirmed by prenatal diagnosis. In total, four common trisomy cases were found to be false negative, resulting in a rate of 0.48/10,000 (4/83,671). In summary, this study conducted in an underdeveloped region with limited support for the new technology development and lack of cost-effective prenatal testing demonstrates the importance of implementing routine aneuploidy screening in the public sector for providing early detection and precise prognostic information.

Cell-free DNA beyond a biomarker for rejection: Biological trigger of tissue injury and potential therapeutics

Cell-free DNA, measured as donor-derived cell-free DNA is developed as a non-specific biomarker for allograft injury and transplant rejection. However, cell-free DNA characteristics are more specific, its fragment length, nucleotide content, and composition, as well as the tissue source of origin, are intrinsically linked to the underlying disease pathogenesis, showing distinct features in acute cellular rejection and antibody-mediated rejection for example. Further, cell-free DNA and cell-free mitochondrial DNA can directly trigger tissue injury as damage-associated molecular patterns through three major intracellular receptors, toll-like receptor 9 , cyclic guanosine monophosphate-adenosine monophosphate synthase, and inflammasomes (i.e., absent in melanoma 2: AIM2). Therefore, in addition to its role as a non-specific marker for allograft injury, cell-free DNA analysis may be used to phenotype transplant rejection, and to non-invasively point the underlying molecular mechanisms with allograft injury. Novel treatment approaches targeting these cell-free DNA pathways may be useful to treat transplant rejection and prevent end-organ dysfunction. In this review, we discuss the link between cell-free DNA characteristics and disease, the role of cell-free DNA as a damage-associated molecular pattern, and novel therapeutics targeting these cell-free DNA molecular pathways and their potential utility to treat transplant rejection.

Causes of aberrant non-invasive prenatal testing for aneuploidy: A systematic review

Non-invasive prenatal testing (NIPT) is performed worldwide to detect common chromosomal aneuploidies. The analysis of cell-free DNA (cfDNA) in maternal blood for NIPT is highly accurate for the detection of the main fetal trisomies: 21,18, and 13. However, false-positive, false-negative, and non-reportable results can occur, and these can have biological causes. Understanding the causes of unexpected NIPT results is essential to enable clinicians and genetic counselors to counsel patients comprehensively and appropriately, both prior to testing as well as after receiving the test results. The classification of non-reportable results from cfDNA analysis is important in order to provide women with precise information. In addition to technical issues, there are biological reasons for discordant results, which can be either fetal or maternal in origin. Contributing fetal factors include insufficient or absent fetal fraction, fetoplacental mosaicism, and the presence of a vanishing twin. In some pregnant women that test positive for NIPT, multiple chromosome aneuploidy has been reported as a result of suspected malignancy, and cancer has been found. False-positive and false-negative results may be the result of placental biology and not a failure in the actual test platform. Explaining the placental origin of cfDNA provides the patient with a clear view of the abilities and limitations of cfDNA-based prenatal screening.

Plasma DNA Profile Associated with DNASE1L3 Gene Mutations: Clinical Observations, Relationships to Nuclease Substrate Preference, and In Vivo Correction

Plasma DNA fragmentomics is an emerging area in cell-free DNA diagnostics and research. In murine models, it has been shown that the extracellular DNase, DNASE1L3, plays a role in the fragmentation of plasma DNA. In humans, DNASE1L3 deficiency causes familial monogenic systemic lupus erythematosus with childhood onset and anti-dsDNA reactivity. In this study, we found that human patients with DNASE1L3 disease-associated gene variations showed aberrations in size and a reduction of a "CC" end motif of plasma DNA. Furthermore, we demonstrated that DNA from DNASE1L3-digested cell nuclei showed a median length of 153 bp with CC motif frequencies resembling plasma DNA from healthy individuals. Adeno-associated virus-based transduction of Dnase1l3 into Dnase1l3-deficient mice restored the end motif profiles to those seen in the plasma DNA of wild-type mice. Our findings demonstrate that DNASE1L3 is an important player in the fragmentation of plasma DNA, which appears to act in a cell-extrinsic manner to regulate plasma DNA size and motif frequency.

Cell-free DNA profiling in patients with lupus nephritis

Background

Increased level of cell-free DNA (cf-DNA) is associated with systemic lupus erythematosus (SLE) and might be related to disease activity. The aim of this study was to evaluate whether cfDNA integrity, size distribution and concentration of different cfDNA fractions is associated with lupus activity and kidney involvement.

Methods

Blood samples were collected from 43 SLE patients and 50 healthy controls. Nuclear and mitochondrial fractions of cfDNA and intracellular DNA were quantified by real-time qPCR. Sizing and quantification of total cfDNA level was performed on Bioanalyzer.

Results

We determined four parameters that characterized cfDNA profile: fragmentation index, ratio of intra- to extracellular mtDNA copy number, cfDNA concentration, and presence of 54–149 bp and 209–297 bp fragments. Patients with healthy-like cfDNA profile had higher eGFR ( P = 0.009) and more often no indications for kidney biopsy or less advanced lupus nephritis (LN) ( P = 0.037). In contrary, SLE patients with distinct cfDNA profile (characterized by increased cfDNA concentration and fragmentation, higher discrepancy between intra- to extracellular mtDNA copy number, and the presence of 54–149 bp and 209–297 bp fragments) had lower eGFR ( P = 0.005) and more often advanced LN or history of renal transplantation ( P = 0.001).

Conclusions

We showed that cfDNA profiling may help to distinguish SLE patients with renal involvement and severe disease course from patients with more favorable outcomes. We suggest cfDNA profile a promising SLE biomarker.

Detection and characterization of jagged ends of double-stranded DNA in plasma

Cell-free DNA in plasma has been used for noninvasive prenatal testing and cancer liquid biopsy. The physical properties of cell-free DNA fragments in plasma, such as fragment sizes and ends, have attracted much recent interest, leading to the emerging field of cell-free DNA fragmentomics. However, one aspect of plasma DNA fragmentomics as to whether double-stranded plasma molecules might carry single-stranded ends, termed a jagged end in this study, remains underexplored. We have developed two approaches for investigating the presence of jagged ends in a plasma DNA pool. These approaches utilized DNA end repair to introduce differential methylation signals between the original sequence and the jagged ends, depending on whether unmethylated or methylated cytosines were used in the DNA end-repair procedure. The majority of plasma DNA molecules (87.8%) were found to bear jagged ends. The jaggedness varied according to plasma DNA fragment sizes and appeared to be in association with nucleosomal patterns. In the plasma of pregnant women, the jaggedness of fetal DNA molecules was higher than that of the maternal counterparts. The jaggedness of plasma DNA correlated with the fetal DNA fraction. Similarly, in the plasma of cancer patients, tumor-derived DNA molecules in patients with hepatocellular carcinoma showed an elevated jaggedness compared with nontumoral DNA. In mouse models, knocking out of the Dnase1 gene reduced jaggedness, whereas knocking out of the Dnase1l3 gene enhanced jaggedness. Hence, plasma DNA jagged ends represent an intrinsic property of plasma DNA and provide a link between nuclease activities and the fragmentation of plasma DNA.

Evolving story of autoantibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by antinuclear antibody (ANA) production. ANAs bind to DNA, RNA and complexes of proteins and nucleic acids and are important markers for diagnosis and activity. According to current models, ANAs originate from antigen-driven processes; nevertheless, antibody responses to both DNA and RNA binding proteins display features unexpected in terms of current paradigms for antigenicity. These differences may reflect disturbances in both B and T cells critical for autoreactivity. Clinically, ANA testing has new uses for determining classification as well as assessing eligibility for clinical trials. Studies of patients with established disease show frequent seronegativity. In this setting, seronegativity may indicate a stage of disease called post-autoimmunity in which the natural history of disease or effects of immunosuppressive therapies modifies responses. The new uses of ANA testing highlight the importance of understanding autoantigenicity and developing sensitive and informative assays for clinical assessments.

The fragmentation patterns of maternal plasma cell-free DNA and its applications in non-invasive prenatal testing

The discovery of cell-free DNA (cfDNA) in maternal plasma has opened up new promises for the development of non-invasive prenatal testing (NIPT). Application of cfDNA in NIPT of fetus diseases and abnormalities is restricted by the low amount of fetal DNA molecules in maternal plasma. Fetus-derived cfDNA in maternal plasma are shorter than maternal DNA, thus leveraging the maternal and fetus-derived cfDNA molecules size difference has become a novel and more accurate method for NIPT. However, multiple biological properties such as size distribution of plasma DNA, proportion of fetal-derived DNA and methylation levels in maternal plasma across different gestational ages still remain largely unknown. Further insights into the size distribution and fragmentation pattern of circulating plasma cfDNA will shed light on the origin and fragmentation mechanisms of cfDNA during physiological and pathological processes in prenatal diseases and enhance our ability to take the advantage of plasma cfDNA as a molecular diagnostic tool. In the review, we start by summarizing the research techniques for the determination of the fragmentation profiles of cfDNA in maternal plasma. We then summarize the main progress and findings in size profiles of maternal plasma cfDNA and cffDNA. Finally, we discuss the potential diagnostic applications of plasma cfDNA size profiling.

Circulating tumour-derived KRAS mutations in pancreatic cancer cases are predominantly carried by very short fragments of cell-free DNA

BACKGROUND

The DNA released into the bloodstream by malignant tumours· called circulating tumour DNA (ctDNA), is often a small fraction of total cell-free DNA shed predominantly by hematopoietic cells and is therefore challenging to detect. Understanding the biological properties of ctDNA is key to the investigation of its clinical relevance as a non-invasive marker for cancer detection and monitoring.

METHODS

We selected 40 plasma DNA samples of pancreatic cancer cases previously reported to carry a KRAS mutation at the 'hotspot' codon 12 and re-screened the cell-free DNA using a 4-size amplicons strategy (57 bp, 79 bp, 167 bp and 218 bp) combined with ultra-deep sequencing in order to investigate whether amplicon lengths could impact on the capacity of detection of ctDNA, which in turn could provide inference of ctDNA and non-malignant cell-free DNA size distribution.

FINDINGS

Higher KRAS amplicon size (167 bp and 218 bp) was associated with lower detectable cell-free DNA mutant allelic fractions (p < 0·0001), with up to 4·6-fold (95% CI: 2·6-8·1) difference on average when comparing the 218bp- and the 57bp-amplicons. The proportion of cases with detectable KRAS mutations was also hampered with increased amplicon lengths, with only half of the cases having detectable ctDNA using the 218 bp assay relative to those detected with amplicons less than 80 bp.

INTERPRETATION

Tumour-derived mutations are carried by shorter cell-free DNA fragments than fragments of wild-type allele. Targeting short amplicons increases the sensitivity of cell-free DNA assays for pancreatic cancer and should be taken into account for optimized assay design and for evaluating their clinical performance.

FUNDING

IARC; MH CZ - DRO; MH SK; exchange program between IARC and Sao Paulo medical Sciences; French Cancer League.

Identification of Specific Joint-Inflammatogenic Cell-Free DNA Molecules From Synovial Fluids of Patients With Rheumatoid Arthritis

Elevated cell-free DNA (cfDNA) levels in the plasma and synovial fluid of rheumatoid arthritis (RA) patients are proposed to be pathologically relevant. However, direct evidence to support this perception is lacking, and molecular feature of the cfDNA molecules with assumed pathological function is not well characterized. Here, we confirm remarkably increased levels of total synovial fluid and plasma cfDNAs in a large cohort of patients with rheumatoid arthritis compared to the counterparts in osteoarthritis, and demonstrate the potent inflammatogenic effects of RA synovial fluid cfDNA on both human monocyte cell line and primary cells related to RA. Massively parallel sequencing identifies distinct molecular pattern of cfDNA in RA, as characterized by enriching CpG-motif containing sequences. Importantly, these identified CpG-motif-rich sequences are hypomethylated in RA patients and induce severe inflammatory responses both in vitro and in vivo. Our data demonstrate the pathological role of global and specific cfDNA molecules in RA, thereby identifying novel therapeutic target candidate and potential biomarker for RA.

Nonreportable rates and cell-free DNA profiles in noninvasive prenatal testing among women with heparin treatment

OBJECTIVE

To evaluate the "nonreportable" rate in patients treated with heparin and to determine the effect of heparin on the results of noninvasive prenatal testing (NIPT).

METHOD

This was a single-center retrospective study of NIPT. The "nonreportable" rate of NIPT was evaluated according to presence or absence of heparin treatment. After excluding true-positive cases, a matched cohort study evaluating Z-scores, GC bias, and cell-free DNA (cfDNA) profiles was performed to investigate the effect of heparin on NIPT results.

RESULTS

Overall, 2651 singleton pregnancies with available clinical information were evaluated; 23 mothers were treated with heparin. The nonreportable rate was much higher among patients treated with heparin than among those who were not (8.70% vs 0.15%). In the matched cohort study, the Z-scores for chromosomes 13, 18, and 21, and GC bias were significantly higher in the heparin group than in the matched control group. Based on cfDNA library electrophoresis data, the proportion of short-sized cfDNA was higher in the heparin group.

CONCLUSION

Heparin use increased the nonreportable rate of NIPT results by borderline Z-scores, possibly caused by the increased proportions of shorter and GC-rich cfDNA fragments. This information will be helpful for prenatal genetic counseling for patients requiring heparin treatment.

The Role of Extracellular DNA and Histones in Ischaemia-Reperfusion Injury of the Myocardium

Despite an increase in the rates of survival in patients suffering myocardial infarction, as yet there is no therapy specifically targeting ischaemia and reperfusion injury of the myocardium. With a greater understanding of immune activation during infarction, more potential treatment targets are now being identified. The innate immune system is believed to play an important role in the myocardium after ischaemia-driven cardiomyocyte death. The release of intracellular contents including DNA into the extracellular space during necrosis and cell rupture is now believed to create a pro-inflammatory milieu which propagates the inflammatory process. DNA and DNA fragments have been shown to activate the innate immune system by acting as Danger-Associated Molecular Patterns (DAMPs), which act as ligands on toll-like receptors (TLRs). Stimulation of TLRs, in turn, can activate intracellular cell death pathways such as pyroptosis. Here, we review the role of DNA fragments during ischaemia and reperfusion, and assess their potential as a target in the quest to preserve cardiomyocyte viability following myocardial infarction.

Size profile of cell-free DNA: A beacon guiding the practice and innovation of clinical testing

Cell-free DNA (cfDNA) has pioneered the development of noninvasive prenatal testing and liquid biopsy, its emerging applications include organ transplantation, autoimmune diseases, and many other disorders; size profile of cfDNA is a crucial biological property and is essential for its clinical applications. Therefore, a thorough mastery of the characteristic and potential applications of cfDNA size profile is needed. Methods: Based on the recent researches, we summarized the size profile of cfDNA in pregnant women, tumor patients, transplant recipients and systemic lupus erythematosus (SLE) patients to explore the common features. We also concluded the applications of size profile in pre-analytical phases, analytical phases for novel assays, and preparation of quality control materials (QCMs). Results: The size profile of cfDNA shared common features in different populations, and was distributed as a "ladder" pattern with a dominant peak at ~166 bp. However, cfDNA entailed slightly discrepant characteristics due to specific tissues of origin. The dominant peaks of fetal and maternal cfDNA fragments in pregnant women were at 143 bp and 166 bp, respectively. The plasma cfDNA in tumor patients, transplant recipients, and SLE patients had a peak of around 166 bp. In pre-analytical phases, size profile served as a vital indicator to judge the eligibility of specimens, thus ensuring the successful implementation of assays. More importantly, the size profile had the potential to enrich short fragments, calculate fetal fraction, detect fetal abnormalities, predict tumor progress in analytical phase and to guide the preparation of QCMs. Conclusions: Our finding summarized the characteristics and potential applications of cfDNA size profile, providing clinical researchers with novel assays by the extensive application of cfDNA.

Combining the use of a fetal fraction-based risk algorithm and probability of an informative redraw in noninvasive prenatal testing for fetal aneuploidy

Some women undergoing noninvasive prenatal testing (NIPT) do not receive an informative result due to low fetal fraction (FF). A proportion of these are at increased risk for fetal trisomy 13, 18, or triploidy, while others have no change from their prior risk. Women with an initial uninformative NIPT need to be counseled about any such change in their risk for fetal abnormality and also the probability that a redraw will be informative. To help in the decision making, we reviewed a dataset of single nucleotide polymorphism‐based NIPT with uninformative results where a redraw was received. Risk for trisomy 13, 18, or triploidy was evaluated using a fetal fraction‐based risk (FFBR) algorithm. Risk‐unchanged women were further analyzed using a regression model to determine the likelihood of an informative redraw. Of 2,644 women with an uninformative NIPT and a redraw, 1,147 (43.4%) were high risk for trisomy 13, 18, or triploidy. 1,497 (56.6%) were risk unchanged and, of these, 975 (65.1%) cases had an informative redraw (i.e., risks were available for 2,122 (80%) of those initially classified as uninformative). The regression model for the risk‐unchanged cases provided a new table for predicting an informative redraw. Likelihood of a successful redraw was significantly (p < .001) dependent on the initial FF, maternal weight, and time between blood draws. We conclude that the FFBR algorithm and the predictive model for an informative redraw provide complementary additions in the management of women presented with an initially uninformative SNP‐based NIPT due to low FF. We suggest approaches for the counseling and follow‐up testing for women with an initially uninformative NIPT.

Fetal fraction and noninvasive prenatal testing: What clinicians need to know

The fetal fraction (FF) is a function of both biological factors and bioinformatics algorithms used to interpret DNA sequencing results. It is an essential quality control component of noninvasive prenatal testing (NIPT) results. Clinicians need to understand the biological influences on FF to be able to provide optimal post-test counseling and clinical management. There are many different technologies available for the measurement of FF. Clinicians do not need to know the details behind the bioinformatics algorithms of FF measurements, but they do need to appreciate the significant variations between the different sequencing technologies used by different laboratories. There is no universal FF threshold that is applicable across all platforms and there have not been any differences demonstrated in NIPT performance by sequencing platform or method of FF calculation. Importantly, while FF should be routinely measured, there is not yet a consensus as to whether it should be routinely reported to the clinician. The clinician should know what to expect from a standard test report and whether reasons for failed NIPT results are revealed. Emerging solutions to the challenges of samples with low FF should reduce rates of failed NIPT in the future. In the meantime, having a "plan B" prepared for those patients for whom NIPT is unsuccessful is essential in today's clinical practice.

TRIDENT-2: National Implementation of Genome-wide Non-invasive Prenatal Testing as a First-Tier Screening Test in the Netherlands

The Netherlands launched a nationwide implementation study on non-invasive prenatal testing (NIPT) as a first-tier test offered to all pregnant women. This started on April 1, 2017 as the TRIDENT-2 study, licensed by the Dutch Ministry of Health. In the first year, NIPT was performed in 73,239 pregnancies (42% of all pregnancies), 7,239 (4%) chose first-trimester combined testing, and 54% did not participate. The number of trisomies 21 (239, 0.33%), 18 (49, 0.07%), and 13 (55, 0.08%) found in this study is comparable to earlier studies, but the Positive Predictive Values (PPV)-96% for trisomy 21, 98% for trisomy 18, and 53% for trisomy 13-were higher than expected. Findings other than trisomy 21, 18, or 13 were reported on request of the pregnant women; 78% of women chose to have these reported. The number of additional findings was 207 (0.36%); these included other trisomies (101, 0.18%, PPV 6%, many of the remaining 94% of cases are likely confined placental mosaics and possibly clinically significant), structural chromosomal aberrations (95, 0.16%, PPV 32%,) and complex abnormal profiles indicative of maternal malignancies (11, 0.02%, PPV 64%). The implementation of genome-wide NIPT is under debate because the benefits of detecting other fetal chromosomal aberrations must be balanced against the risks of discordant positives, parental anxiety, and a potential increase in (invasive) diagnostic procedures. Our first-year data, including clinical data and laboratory follow-up data, will fuel this debate. Furthermore, we describe how NIPT can successfully be embedded into a national screening program with a single chain for prenatal care including counseling, testing, and follow-up.

Could high levels of cell-free DNA in maternal blood be associated with maternal health and perinatal outcomes?

The aim of this study was to evaluate the maternal and foetal factors affect higher cell-free DNA (cfDNA) levels and to investigate a possible relationship between high cfDNA levels and adverse perinatal outcomes. From a total of 4594 women who underwent non-invasive prenatal testing from January 2016 to March 2018 in our hospital, 112 women had high levels of cfDNA, which was not appropriate for testing. Maternal characteristics and perinatal outcomes were compared between patients with high levels of cfDNA and normal levels of cfDNA. Patients with high levels of cfDNA had greater risks than patients with normal cfDNA levels of pregnancy complications but no statistically significant difference was found. Patients with high cfDNA levels had higher foetal death rates with a statistically significant difference (9.8% versus 1.8%, p = .024). An increase in foetal death could be expected in patients with increased cfDNA levels; therefore, these patients should be carefully followed up during pregnancy.IMPACT STATEMENTWhat's already known about this topic? Most studies about cfDNA levels are focussed on the foetal fraction. There are new arguments about maternal health and cfDNA. It is known that autoimmune diseases as systemic lupus erythematosus (SLE) and maternal obesity increase cell turnover. There are also clinical studies suggesting a relationship between low molecular weight heparin therapy and the amount of cfDNA.What do the results of this study add? This is the first study evaluating the maternal and foetal biological factors affecting cfDNA concentrations and investigating the possible relationship between high cfDNA levels and adverse perinatal outcomes in patients with high levels of cfDNA compared to patients with normal levels of cfDNA. In the present study, it was found that an increase in foetal death could be expected in patients with higher cfDNA levels.What are the implications of these findings for clinical practice and/or further research? If potential effects and underlying causes of increased cfDNA could be explained, cfDNA might be used as a biomarker for adverse perinatal outcomes.

Triggers of Autoimmunity: The Role of Bacterial Infections in the Extracellular Exposure of Lupus Nuclear Autoantigens

Infections are considered important environmental triggers of autoimmunity and can contribute to autoimmune disease onset and severity. Nucleic acids and the complexes that they form with proteins—including chromatin and ribonucleoproteins—are the main autoantigens in the autoimmune disease systemic lupus erythematosus (SLE). How these nuclear molecules become available to the immune system for recognition, presentation, and targeting is an area of research where complexities remain to be disentangled. In this review, we discuss how bacterial infections participate in the exposure of nuclear autoantigens to the immune system in SLE. Infections can instigate pro-inflammatory cell death programs including pyroptosis and NETosis, induce extracellular release of host nuclear autoantigens, and promote their recognition in an immunogenic context by activating the innate and adaptive immune systems. Moreover, bacterial infections can release bacterial DNA associated with other bacterial molecules, complexes that can elicit autoimmunity by acting as innate stimuli of pattern recognition receptors and activating autoreactive B cells through molecular mimicry. Recent studies have highlighted SLE disease activity-associated alterations of the gut commensals and the expansion of pathobionts that can contribute to chronic exposure to extracellular nuclear autoantigens. A novel field in the study of autoimmunity is the contribution of bacterial biofilms to the pathogenesis of autoimmunity. Biofilms are multicellular communities of bacteria that promote colonization during chronic infections. We review the very recent literature highlighting a role for bacterial biofilms, and their major components, amyloid/DNA complexes, in the generation of anti-nuclear autoantibodies and their ability to stimulate the autoreactive immune response. The best studied bacterial amyloid is curli, produced by enteric bacteria that commonly cause infections in SLE patients, including Escherichia coli and Salmonella spps. Evidence suggests that curli/DNA complexes can trigger autoimmunity by acting as danger signals, molecular mimickers, and microbial chaperones of nucleic acids.