Recent developments in fetal nucleic acids in maternal plasma: implications to noninvasive prenatal fetal blood group genotyping

Sparsely methylated mitochondrial cell free DNA released from cardiomyocytes contributes to systemic inflammatory response accompanied by atrial fibrillation

Systemic inflammation is assumed to be the consequence and the cause of atrial fibrillation (AF); however, the underlying mechanism remains unclear. We aimed to evaluate the level of cell-free DNA (cfDNA) in patients with AF and AF mimicking models, and to illuminate its impact on inflammation. Peripheral blood was obtained from 54 patients with AF and 104 non-AF controls, and cfDNA was extracted. We extracted total cfDNA from conditioned medium after rapid pacing to HL-1 cells. Nuclear and mitochondrial DNA were separately extracted and fragmented to simulate nuclear-cfDNA (n-cfDNA) and mitochondrial-cfDNA (mt-cfDNA). The AF group showed higher cfDNA concentration than the non-AF group (12.6 [9.0–17.1] vs. 8.1 [5.3–10.8] [ng/mL], p < 0.001). The copy numbers of n-cfDNA and mt-cfDNA were higher in AF groups than in non-AF groups; the difference of mt-cfDNA was particularly apparent (p = 0.011 and p < 0.001, respectively). Administration of total cfDNA and mt-cfDNA to macrophages significantly promoted IL-1β and IL-6 expression through TLR9, whereas n-cfDNA did not. Induction of cytokine expression by methylated mt-cfDNA was lower than that by unmethylated mt-cfDNA. Collectively, AF was associated with an increased cfDNA level, especially mt-cfDNA. Sparsely methylated mt-cfDNA released from cardiomyocytes may be involved in sterile systemic inflammation accompanied by AF.

Use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for multiplex genotyping

After completion of the human genome project, the focus of geneticists has shifted to elucidation of gene function and genetic diversity to understand the mechanisms of complex diseases or variation of patient response in drug treatment. In the past decade, many different genotyping techniques have been described for the detection of single-nucleotide polymorphisms (SNPs) and other common polymorphic variants. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is among the most powerful and widely used genotyping technologies. The method offers great flexibility in assay design and enables highly accurate genotyping at high sample throughput. Different strategies for allele discrimination and quantification have been combined with MALDI (hybridization, ligation, cleavage, and primer extension). Approaches based on primer extension have become the most popular applications. This combination enables rapid and reliable multiplexing of SNPs and other common variants, and makes MALDI-TOF-MS well suited for large-scale studies in fine-mapping and verification of genome-wide scans. In contrast to standard genotyping, more demanding approaches have enabled genotyping of DNA pools, molecular haplotyping or the detection of free circulating DNA for prenatal or cancer diagnostics. In addition, MALDI can also be used in novel applications as DNA methylation analysis, expression profiling, and resequencing. This review gives an introduction to multiplex genotyping by MALDI-MS and will focus on the latest developments of this technology.

Spontaneous labor onset: is it immunologically mediated?

OBJECTIVE

The investigators tested the hypothesis that maternal-fetal immune interactions could be important in initiating spontaneous labor onset by examining if labor was delayed when fetuses share maternal HLA antigen types.

STUDY DESIGN

HLA antigen types A, B, and DR in 200 Danish mother-infant pairs delivering in 42-44 weeks (postterm) were compared with 195 mother-infant pairs delivering in 37-40 weeks (term).

RESULTS

Sharing of HLA A and B antigens was more common than expected in postterm deliveries. Odds ratios were 1.54 (95% confidence interval [CI], 1.01-2.35) and 1.75 (95% CI, 0.87-3.52), respectively (risk per shared antigen: 1.40 [95% CI, 1.04-1.90] per unit increase). Adding stringent birth-length criteria for postmaturity (92 cases; 168 controls) strengthened risks associated with antigen sharing to 1.57 (95% CI, 0.90-2.74) and 2.60 (95% CI, 1.15-5.88), respectively (risk per shared antigen: 1.60 (95% CI, 1.10-2.32).

CONCLUSION

Postterm-delivered infants had more HLA A and B antigens in common with their mothers, suggesting that recognition of HLA antigen differences by adaptive immunity may have a role in triggering labor onset.

The role of transplacental microtransfusions of maternal lymphocytes in HIV transmission to newborns

BACKGROUND

Perinatal HIV transmission could occur via microtransfused maternal blood during delivery. If so, detecting maternal cells in umbilical cord blood should correlate with infection risk.

OBJECTIVE

To develop sensitive assays for maternal DNA in infant's blood stored as dried blood spots (DBS) and examine the correlation between microtransfusion and perinatal HIV infection risk.

METHODS

Blood-in-blood serial dilutions were prepared as DBS. Extracted DNA was amplified for unique minor-population sequences using 24 allele-specific polymerase chain reaction assays. Using newborns born to HIV+ mothers, paired mother-infant samples were similarly examined to identify unique maternal sequences targeted by allele-specific polymerase chain reaction of DNA extracted from cord blood DBS. Cord-blood PCR-negative infants were categorized as uninfected or perinatally infected by HIV PCR on samples collected 4-8 weeks after birth.

RESULTS

Sequences from added cells were detected at less than 1: 1000 dilutions in 19 of 20 aliquots, and less than 1: 10 000 dilutions in seven of 20 aliquots; the median limit of detection (probit analysis) was one added genomic sequence in 9500 background sequences of amplifiable DNA. Maternal sequences were detected in cord-blood DBS of 50% of infected infants (N = 18) and 44% of uninfected infants (N = 43). Infection did not correlate with more frequent detection of maternal sequences.

CONCLUSION

This semiquantitative assay reliably detected maternal DNA sequences in DBS at levels of less than 1: 1000 cells. Maternal sequences were frequently detected but did not correlate infection risk with detection or level of maternal DNA in umbilical cord blood. Therefore, we could not demonstrate that microtransfusions at parturition were responsible for perinatal HIV transmission.

Noninvasive prenatal diagnosis of aneuploidy using cell-free nucleic acids in maternal blood: promises and unanswered questions

The discovery of cell-free fetal (cff) DNA and RNA in the maternal circulation has driven developments in noninvasive prenatal diagnosis (NIPD) for the past decade. Detection of paternally derived alleles in cff DNA is becoming well established. Now much interest is focussing on NIPD of fetal chromosomal abnormalities, such as trisomy 21, which is a considerable challenge because this demands accurate quantitative measurements of the amounts of specific cff DNA or cff RNA sequences in maternal blood samples. Emerging strategies for distinguishing and quantifying the fetal nucleic acids in the maternal circulation promise continued development of the field, and pose a number of unanswered questions.

Non-invasive prenatal diagnosis: implications for antenatal diagnosis and management of high-risk pregnancies

There has been a huge effort in the last 2-3 decades to develop non-invasive prenatal diagnosis to avoid the risks to the fetus caused by invasive procedures. Obtaining fetal nucleic material for molecular analysis without the need of invasive procedures has been a goal of prenatal diagnosis for many years; this is now been made possible by the use of non-cellular fetal nucleic acids circulating in maternal blood. The placenta is the primary source of these nucleic acids, raising the possibility that they could be a marker for pregnancy complications resulting from placental disease/dysfunction such as pre-eclampsia and fetal growth restriction. If so, these markers might be able to identify cases at risk, predict disease and/or its severity or allow early diagnosis. This has the potential to allow improvements in the management of complicated pregnancies.

Candidate epigenetic biomarkers for non-invasive prenatal diagnosis of Down syndrome

This report describes the first identification and characterization of three chromosome-21-specific DNA sequences (and reference sequences from other chromosomes) that are differentially methylated between peripheral blood and placental tissue, with the aim of providing epigenetic biomarkers for quantifying cell-free fetal DNA in maternal plasma. To select sequences to be screened for differential methylation, three strategies were adopted: (i) investigating promoters of highly differentially expressed genes; (ii) choosing 'random' promoter regions; and (iii) choosing 'random' non-promoter regions. Over 200 pre-selected DNA sequences were screened using a methylation-specific restriction enzyme assay. Differentially methylated sequences located at 21q22.3 (AIRE, SIM2 and ERG genes), 1q32.1 (CD48 gene and FAIM3 gene), 2p14 (ARHGAP25 gene) and 12q24 (SELPLG gene) were identified. Bisulphite conversion confirmed that CpG sites within the AIRE promoter region are highly differentially methylated, and optimized methylation-specific primers for this region that are highly specific for placental DNA were devised. Next, it was shown that the methylation status of chorionic villus sample DNA from first trimester pregnancies matched the hypermethylated state of term placenta. Thus there is no indication of a difference in methylation status between early and term pregnancy for the sequences tested. The identified sequences constitute candidate biomarkers for non-invasive prenatal diagnosis of Down syndrome.

Chimerism in the immunohematology laboratory in the molecular biology era

Dual or multiple cell populations, induced by chimeras, have been the subject of many studies. This long-standing fascination with chimeras has revealed a good deal of knowledge about human inheritance. Although historically most chimeras were caused by natural events, certain current medical intervention therapies are increasing the number of situations that can lead to a mixed cell population, that is, the chimeric condition, in humans. Medical therapies such as transfusion, stem cell transplantation, kidney transplantation, and artificial insemination induce temporary and sometimes permanent chimeras. Such natural or therapeutically induced presentations of chimerism can present challenging issues to the clinical immunohematology laboratory with regard to interpretation of results and subsequent patient management. The purpose of this review was to highlight some of these chimeric states and hypothesize how testing DNA from various tissues can cause apparent discrepancies between phenotype and genotype results.

Use of maternal plasma for non-invasive prenatal diagnosis of fetal ABO genotypes

BACKGROUND

Measurement of free fetal DNA in maternal plasma opened a door for non-invasive prenatal diagnosis. Prenatal diagnosis of fetal ABO genotypes can provide a basis for the prevention and therapy of maternal-fetal incompatibility. We identified fetal ABO genotypes using fetal DNA in plasma from pregnant women with blood group O. The aim of the study was to investigate the accuracy and feasibility of this method.

METHODS

A total of 105 blood group O women in middle or late pregnancy were enrolled. Fetal DNA in maternal plasma and genomic DNA in umbilical vein blood from newborns were extracted using a QIAamp DNA Blood Kit. DNA was amplified to identify ABO genotypes by PCR with sequence-specific primers (PCR-SSP). The genotype results were evaluated using serologic tests for ABO phenotyping.

RESULTS

Using DNA from umbilical vein blood, ABO genotypes of 105 newborns were successfully identified by PCR-SSP. Using fetal DNA from maternal plasma, 88.6% (93/105) fetal ABO genotypes was correct; 12 false results were from 66 pregnant women with fetuses of type non-O. The accuracy in middle pregnancy was lower than that in late pregnancy, although the difference was not significant (0.05<p<0.10).

CONCLUSIONS

It is feasible to use measurement of fetal DNA in plasma from pregnant women with blood group O for prenatal diagnosis of fetal ABO genotypes. The method is useful for the diagnosis and therapy of ABO maternal-fetal incompatibility and hemolytic disease of the newborn.

Molecular testing for transfusion medicine

PURPOSE OF REVIEW

Molecular testing methods were introduced to the blood bank and transfusion medicine community more than a decade ago after cloning of the genes made genetic testing for blood groups, that is genotyping, possible. This review summarizes the progress made in the last decade in applying genotyping to prenatal practice and clinical transfusion medicine.

RECENT FINDINGS

Assays that target allelic polymorphisms prevalent in all populations are reproducible and highly correlated with red blood cell phenotype. For some blood groups, assays that detect silencing mutations are also required for accurate typing, and for ABO and Rh, multiple regions of the genes must be sampled. Genotyping is a powerful adjunct to serologic testing and is superior for typing transfused patients, for D-zygosity determination, for noninvasive fetal typing, and for antigen-matching in sickle cell patients.

SUMMARY

Implementation of molecular testing for transfusion medicine has been a conservative process and limited primarily to reference laboratory environments. With the development of high-throughput platforms, genotyping is poised to move into the mainstream, revolutionizing the provision of antigen-negative donor units. This will enable electronic selection of units antigen matched to recipients at multiple blood group loci, potentially eliminating alloimmunization and significantly improving transfusion outcomes.