Non-invasive determination of the paternal HLA haplotype of a fetus using kinetic PCR to detect fetal microchimerism in maternal plasma

Maternal microchimerism in pediatric inflammatory bowel disease

Inflammatory bowel disease (IBD) shares many immunologic and clinical characteristics with graft versus host disease caused by allogeneic T lymphocytes after hematopoietic cell transplantation. Since maternal cells are known to enter the fetal circulation in a high proportion of pregnancies, we hypothesized that maternal engraftment in the fetus results in immune sequelae that can lead to IBD.

METHOD

The presence and extent of maternal microchimerism in tissues and blood samples from patients with Crohn's, Ulcerative colitis (UC), and control groups were determined using kinetic Polymerase Chain Reaction (kPCR) to detect maternal- and patient-specific HLA types. In addition, fluorescent in situ hybridization (FISH) was employed to detect maternal cells in biopsies from patients with IBD.

RESULTS

Using kPCR, maternal microchimerism was observed in 9 of the 16 (56%) patients with IBD and 6 out of 15 of the control group (40%) (P=NS). Five of 10 Crohn's patients had evidence of maternal microchimerism (50%) (P=NS). Four of six UC patients had evidence of maternal microchimerism in gut tissues (67%) (P=NS). There was no correlation between maternal michrochimerism and disease activity, disease location or granulomas in patients with IBD. Using FISH, five male Crohn's and five male UC patient's intestinal biopsies were analyzed for maternal microchimerism. No maternal cells were identified.

CONCLUSION

There is nothing in the data to suggest that patients with IBD differ from disease controls in their frequency of maternal microchimerism in either blood or gut mucosal tissues. These data suggest that maternal microchimerism in blood and biopsies is a relatively common phenomenon that has neither positive nor negative impact on IBD.

Transfusion-associated microchimerism: the hybrid within

Microchimerism, the coexistence of genetically disparate populations of cells in a receptive host, is well described in both clinical and physiological settings, including transplantation and pregnancy. Microchimerism can also occur after allogeneic blood transfusion in traumatically injured patients, where donor cells have been observed decades after transfusion. To date, transfusion-associated microchimerism (TA-MC) appears confined to this clinical subset, most likely due to the immune perturbations that occur after severe trauma that allow foreign donor cells to survive. Transfusion-associated microchimerism appears to be unaffected by leukoreduction and has been documented after transfusion with an array of blood products. The only significant predictor of TA-MC to date is the age of red cells, with fresher units associated with higher risk. Thus far, no adverse clinical effect has been observed in limited studies of TA-MC. There are, however, hypothesized links to transfusion-associated graft vs host disease that may be unrecognized and consequently underreported. Microchimerism in other settings has gained increasing attention owing to a plausible link to autoimmune diseases, as well as its diagnostic and therapeutic potential vis-a-vis antenatal testing and adoptive immunotherapy, respectively. Furthermore, microchimerism provides a tool to further our understanding of immune tolerance and regulation.

Cell-free fetal nucleic acid testing: a review of the technology and its applications

Cell-free fetal nucleic acids circulating in the blood of pregnant women afford the opportunity for early, noninvasive prenatal genetic testing. The predominance of admixed maternal genetic material in circulation demands innovative means for identification and analysis of cell-free fetal DNA and RNA. Techniques using polymerase chain reaction, mass spectrometry, and sequencing have been developed for the purposes of detecting fetal-specific sequences, such as paternally inherited or de novo mutations, or determining allelic balance or chromosome dosage. Clinical applications of these methods include fetal sex determination and blood group typing, which are currently available commercially although not offered routinely in the United States. Other uses of cell-free fetal DNA and RNA being explored are the detection of single-gene disorders, chromosomal abnormalities, and inheritance of parental polymorphisms across the whole fetal genome. The concentration of cell-free fetal DNA may also provide predictive capabilities for pregnancy-associated complications. The roles that cell-free fetal nucleic acid testing assume in the existing framework of prenatal screening and invasive diagnostic testing will depend on factors such as costs, clinical validity and utility, and perceived benefit-risk ratios for different applications. As cell-free fetal DNA and RNA testing continues to be developed and translated, significant ethical, legal, and social questions will arise that will need to be addressed by those with a stake in the use of this technology.

TARGET AUDIENCE

Obstetricians & Gynecologists and Family Physicians Learning Objectives: After participating in this activity, physicians should be better able to evaluate techniques and tools for analyzing cell-free fetal nucleic acids, assess clinical applications of prenatal testing, using cell-free fetal nucleic acids and barriers to implementation, and distinguish between relevant clinical features of cell-free fetal nucleic acid testing and existing prenatal genetic screening and diagnostic procedures.

Infusion of haplo-identical killer immunoglobulin-like receptor ligand mismatched NK cells for relapsed myeloma in the setting of autologous stem cell transplantation

Killer immunoglobulin-like receptor (KIR)-ligand mismatched natural killer (NK) cells play a key role in achieving durable remission after haplo-identical transplantation for acute myeloid leukaemia. We investigated the feasibility of transfusing haplo-identical, T-cell depleted, KIR-ligand mismatched NK cells, after conditioning therapy with melphalan and fludarabine, to patients with advanced multiple myeloma (MM) followed by delayed rescue with autologous stem cells. No graft-versus-host disease or failure of autologous stem cells to engraft was observed. There was significant variation in the number of allo-reactive NK cells transfused. However, all NK products containing allo-reactive NK cells killed the NK cell target K562, the MM cell line U266, and recipient MM cells when available. Post NK cell infusion there was a rise in endogenous interleukin-15 accompanied by increasing donor chimaerism. Donor chimaerism was eventually lost, which correlated with the emergence of potent host anti-donor responses indicating that the immunosuppressive properties of the conditioning regimen require further optimization. Further, blocking of inhibitory KIR-ligands with anti-human leucocyte antigen antibody substantially enhanced killing of MM cells thus highlighting the potential for modulating NK/MM cell interaction. Encouragingly, 50% of patients achieved (near) complete remission. These data set the stage for future studies of KIR-ligand mismatched NK cell therapy in the autologous setting.

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.

Enhanced ascertainment of microchimerism with real-time quantitative polymerase chain reaction amplification of insertion-deletion polymorphisms

BACKGROUND

The characterization of microchimerism (MC) by gene amplification has been limited by few allogeneic markers, ascertainment bias, and assay analytic performance. To address this, a panel of 12 MC assays based on insertion-deletion (InDel) polymorphisms had been optimized.

STUDY DESIGN AND METHODS

The InDel assays were validated with comprehensive in vitro spiking studies at the stochastic limit of detection. Their ability was also determined to ascertain MC of unknown source genotype with both theoretical and actual donor-recipient pairs, and the assays were applied to a clinical population of 73 trauma patients who received transfusions where MC was previously characterized by HLA-based assays alone.

RESULTS

In the stochastic spiking experiments, all assays were sensitive to a single copy of target DNA, and no false-positive amplification occurred among 1128 samples studied. Among 219 theoretical donor-recipient pairs, informative alleles existed for 99.5 percent with both InDel and HLA compared to 91.3 percent with HLA alone. In the clinical population, 33 cases of MC were detected (9 more cases than by HLA-DR alone) in the nonleukoreduced (non-LR) group and 8 cases (1 more case than by HLA-DR) in the LR group for the short-term follow-up. Among 27 long-term follow-up samples, 8 cases were detected overall (3 more cases than by HLA-DR alone).

CONCLUSION

It is concluded that an InDel-based assay panel has excellent technical performance characteristics while also allowing for ascertainment of some MC cases not detectable with HLA alone. The tandem use of both the InDel and the HLA provides a powerful tool for the enhanced ascertainment of MC.

Maternal microchimerism in the livers of patients with biliary atresia

Background

Biliary atresia (BA) is a neonatal cholestatic disease of unknown etiology. It is the leading cause of liver transplantation in children. Many similarities exist between BA and graft versus host disease suggesting engraftment of maternal cells during gestation could result in immune responses that lead to BA. The aim of this study was to determine the presence and extent of maternal microchimerism (MM) in the livers of infants with BA.

Methods

Using fluorescent in situ hybridization (FISH), 11 male BA & 4 male neonatal hepatitis (NH) livers, which served as controls, were analyzed for X and Y-chromosomes. To further investigate MM in BA, 3 patients with BA, and their mothers, were HLA typed. Using immunohistochemical stains, the BA livers were examined for MM. Four additional BA livers underwent analysis by polymerase chain reaction (PCR) for evidence of MM.

Results

By FISH, 8 BA and 2 NH livers were interpretable. Seven of eight BA specimens showed evidence of MM. The number of maternal cells ranged from 2–4 maternal cells per biopsy slide. Neither NH specimen showed evidence of MM. In addition, immunohistochemical stains confirmed evidence of MM. Using PCR, a range of 1–142 copies of maternal DNA per 25,000 copies of patients DNA was found.

Conclusions

Maternal microchimerism is present in the livers of patients with BA and may contribute to the pathogenesis of BA.

Quantification of maternal microchimerism by HLA-specific real-time polymerase chain reaction: Studies of healthy women and women with scleroderma

OBJECTIVE

Microchimerism (Mc), originating from bidirectional fetal-maternal cell traffic during pregnancy, has recently been identified in healthy adults and in patients with scleroderma (systemic sclerosis [SSc]). This study was undertaken to investigate the frequency and quantitative levels of maternal Mc (MMc) in healthy women and women with SSc.

METHODS

HLA-specific primers and fluorogenic probes were used in real-time quantitative polymerase chain reaction assays to detect and quantify MMc by targeting noninherited, nonshared HLA sequences. DNA-based HLA typing was conducted in 67 proband-mother pairs and in all children if the proband was parous. Statistical analysis was limited to 50 proband-mother pairs (including 32 healthy women and 18 women with SSc) in whom MMc could be distinguished from potential fetal Mc.

RESULTS

MMc in peripheral blood mononuclear cells was more frequent among women with SSc (72%) than healthy women (22%) (odds ratio 9.3, P = 0.001). However, levels of MMc, expressed as the genome equivalent of maternal cells per million (gEq/mil), were not significantly different (0-68.6 gEq/mil in SSc patients, 0-54.5 in healthy women). In additional studies, positivity for MMc was demonstrated in a bone marrow aspirate from an SSc patient in whom peripheral blood had been found to be negative for MMc on 4 occasions, and tissue from a subsequent autopsy of this patient had MMc levels of 757 and 1,489 gEq/mil in the lung and heart, respectively.

CONCLUSION

MMc is not uncommon in the peripheral blood of healthy adults, is increased in frequency in patients with SSc, and may be present in bone marrow and disease-affected tissues although absent in the peripheral blood.

DNA enrichment by allele-specific hybridization (DEASH): a novel method for haplotyping and for detecting low-frequency base substitutional variants and recombinant DNA molecules

Detecting rare sequence variants in genomic DNA is central to the analysis of de novo mutation and recombination events and the detection of rare pathological mutations in mixed cell populations. Current PCR techniques suffer from noise that limits detection to variants present at a frequency of at least 10(-4)-10(-5) per cell. We now describe an alternative approach that recovers genomic DNA molecules containing a known single-nucleotide variant by hybridization selection using a biotinylated allele-specific oligonucleotide, followed by hybrid capture on streptavidin-coated paramagnetic beads and subsequent analysis by PCR. This technique of DNA enrichment by allele-specific hybridization (DEASH) is fast, effective for all tested single-nucleotide polymorphisms (SNPs), and can recover large (>10 kb) single-stranded molecules. A single round of DEASH is effective in separating haplotypes from genomic DNA and can not only readily detect and validate DNA molecules containing a single base change at a frequency of 10(-5) per cell, but can also place these changes within the context of an extended haplotype. This technique offers a new approach to the analysis of mutation and recombination, and has the potential to detect very rare de novo base substitutions.

Comprehensive banking of sibling donor cord blood for children with malignant and nonmalignant disease

Banking of cord blood (CB) for unrelated hematopoietic stem cell (HSC) transplantation is well established. However, directed-donor banking of CB for siblings in a current good tissue practices (cGTP) environment has not previously been investigated. Families were eligible for the present study if they were caring for a child with a disorder treatable by HSC transplantation and expecting the birth of a full sibling. We devised standard operating procedures and policies to address eligibility, donor recruitment, donor and recipient evaluation, CB collection, shipping, graft characterization, storage, and release of CB from quarantine. Many of these policies are distinctly different from those established for unrelated-donor CB banks. We enrolled 540 families from 42 states. Collections occurred at several hundred different hospitals. No family was deferred on the basis of health history or infectious disease testing, but departures from standard donor suitability criteria were documented. Disease categories for sibling recipients included malignancy, sickle cell anemia, thalassemia major, nonmalignant hematological conditions, and metabolic errors. Mean CB volume (including anticoagulant) was 103.1 mL; mean nucleated cell count was 8.9 x 10(8). Cell dose exceeded 1.5 x 10(7) nucleated cells per kilogram for 90% of banked units. Seventeen units (3.4%) have been transplanted. Sixteen of the 17 CB allograft recipients had stable engraftment of donor cells. Remote-site collection of sibling donor CB can be accomplished with a high success rate and in a cGTP-guided environment. The cellular products have been used successfully for transplantation; their number and characteristics should be adequate to support the first prospective clinical investigations of sibling CB transplantation.

Lack of donor hyporesponsiveness and donor chimerism after clinical transplantation of the hand

BACKGROUND

Composite tissue allografts offer great potential in reconstructive surgery. However, the risks of immunosuppression and graft-versus-host disease (GVHD) after transplantation of vascularized bone in these grafts are significant. Transplantation of vascularized bone also may confer donor hematopoietic chimerism and, potentially, tolerance. We have followed two hand transplant recipients for more than 1 year to determine the level of chimerism and possible donor-specific tolerance, in addition to possible GVHD.

METHODS

We performed kinetic studies on peripheral blood of two subjects after hand transplantation that included portions of the radius and ulna. We evaluated donor-specific reactivity, chimerism, and antibody production.

RESULTS

Donor-specific tolerance did not develop clinically or in mixed lymphocyte reaction. The first subject recovered an excellent in vitro response to phytohemagglutinin, donor and third-party alloantigen, and by month 4 and at month 12 also recovered the ability to respond to Epstein-Barr virus. The second subject also demonstrated good in vitro proliferative responses, which were attenuated by immunosuppression. No phenotypic changes in mature hematopoietic lineages were detected by four-color flow cytometry other than those expected in response to immunosuppression. Donor chimerism was not detectable using four-color flow cytometry. Microchimerism (approximately 1:75,000 cells) was observed at the level of detection in some of the early posttransplantation specimens and was undetectable thereafter.

CONCLUSIONS

In this particular transplantation and immunosuppressive regimen, the composite tissue allograft with vascularized bone marrow did not provide the immunologic benefit of tolerance induction nor cause GVHD.