Evaluation of seven PCR-based assays for the analysis of microchimerism

Genetic diagnosis in recently transfused patients

Analysis of recently transfused patients is usually postponed to avoid spurious results because of contamination with donor's cells. However, little is known about the extent of this influence in routine molecular diagnostic tests. To elucidate this question, we tested a mix of blood samples from 2 α-1-antitrypsin-deficient patients diagnosed as Pi*Z homozygous with 1 normal donor at 1:1, 1:10, 1:20, and 1:30 proportions. Human identification panel and Pi*Z allele detection were used to establish the detection limit of a blood mixture. Mixtures of 1:1 and 1:10 were easily detected with both techniques, whereas for 1:30, it was necessary to change the equipment settings to identify the mixture. Moreover, the heterozygous pattern observed for the mixtures on Pi*Z genotyping was weaker at this level of mixture. We further evaluated the degree of mixture detectable in 20 transfused patients who received 1 blood unit (concentrate of irradiated or nonirradiated red blood cells) using the human identification panel. Two days after the transfusion, the presence of the donor's markers was not detected, suggesting that after this time point the levels of admixture are below 1:30. The methods applied in the present study showed adequate sensitivity to identify alleles of the so-called "smaller population" of cells up to 3%, approximately. The same result was obtained in a "diagnostic situation," in which the blood mixture was submitted to a PCR-RFLP protocol to detect a mutation.

Concise review: expanding roles for hematopoietic cellular therapy and the blood transfusion services

Hematopoietic stem cells (HSCs) have remained at the forefront of stem cell research for the past 50 years, since the therapeutic potential of bone marrow transplantation was realized. Uniquely, among stem and progenitor cells, research progress has been made in parallel between the laboratory benchtop and hospital bedside during this period. Integral to this work has been the role of the transfusion medicine services in the collection, storage, and processing of HSCs. The next decade promises to bring further developments: with new fields of cellular therapies, stem cell vaccination, and stem cell drug testing opening up. This article summarizes exciting areas of research concerning the behavior and potential clinical applications of HSCs. For the purposes of clarity, we describe in turn the trafficking and transfer of HSCs; ex vivo expansion of HSC units from different sources; and finally, applications of specifically selected subsets of hematopoietic cells and their progeny.

Microchimerism evaluation in recipients of living-related or unrelated deceased allograft renal transplants

The presence of microchimerism in the peripheral blood of solid organ graft recipients has been associated with long-term solid organ acceptance, immunologic tolerance, and less aggressive immunosuppressive therapy. Molecular biology assays are among the most sensitive methods to detect microchimerism, primarily to evaluate Y chromosome sequences in females as indirect evidence of circulating male nucleated donor cells. We screened for the presence of the SRY sequence region in peripheral blood of 13 female recipients of male kidney grafts: 5 living-related and 8 deceased grafts. Only patients who received grafts from related living donors exhibited microchimerism. Five of 13 patients studied exhibited better graft outcomes, including the 4 who were positive for the SRY sequences.

Presence of donor-and-recipient-derived DNA microchimerism in the cell-free blood samples of renal transplantation recipients associates with the acceptance of transplanted kidneys

AIM

To examine whether the existence of the donor-and recipient-derived DNA chimerism in recipient's plasma can be a predictive marker for the status of transplanted organ.

METHODS

One hundred and twenty-six female patients who had been transplanted with male kidneys were enrolled in the present study. In these female recipients, the SRY(1), DYZ(1)(1st) and DYZ(1)(2nd) genes on the Y chromosome from the plasma were prospectively examined using reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

SRY, DYZ(1)(1st) and DYZ(1)(2nd) sequences were detected in the cell-free blood (plasma) of 97 (77%) of 126 female patients with male kidney. The average time that the transplanted kidneys functioned was 8.7 years and 5.4 years among microchimerism-positive and microchimerism-negative recipients, respectively. The frequency of the patients who had acute rejection after renal transplantation was approximately 10% and 28% in microchimerism-positive and microchimerism-negative recipients, respectively. Serum creatinine levels in microchimerism-positive patients were significantly lower than those in microchimerism-negative patients.

CONCLUSION

These results suggest that plasma DNA microchimerism present in certain patients following renal transplantation and measurement of plasma DNA microchimerism using quantitative RT-PCR might be a useful predictor for the acceptance of transplanted kidneys.

Use of highly sensitive mitochondrial probes to detect microchimerism in xenotransplantation models

Chimerism, defined as the co-existence of cells of different origin within the same organism, has received much attention in hematopoietic cell and organ transplantation because of the strict relationship between its establishment and the induction of specific tolerance. Traditional methods applied for chimerism detection, such as immunohistochemistry, cytogenetics, fluorescent-activated cell sorter analysis, and serological and biochemical testing, are limited by their sensitivity. We have established a highly sensitive molecular approach based on the amplification of the mitochondrial cytochrome B gene and tested its specificity and sensitivity level in six different mammalian species, including human, pig, mouse, rat, sheep and rabbit. Increased sensitivity of detection of specific amplification products was obtained by the non-radioactive Southern blot technique. This novel approach allows the detection of one cell against the background of 1 to 4 x 10(6) xenogenec cells and will be helpful for high-sensitivity analysis of donor cell engraftment after xenotransplantation procedures in these animal models.

Can post-mortem blood be used for DNA profiling after peri-mortem blood transfusion?

The question of whether blood transfusions can affect DNA profiling is still a contentious issue throughout the forensic community. It is hypothesised that donor leucocytes present in the administered blood will be detected upon examination of recipient blood. In order to resolve this issue, a selection of theoretical experiments were carried out to determine how much donor DNA must be present for its detection in blood components. Five casework examples of material collected from individuals after massive transfusion, including a case of whole organ transplantation, were also investigated. The results indicated that filtration processes used during blood production do not allow the passage of enough donor leucocytes for detection using current forensic profiling techniques. No evidence of secondary profile alleles were found in any case, indicating that peri-mortem blood transfusion does not affect DNA profiling.

Short tandem repeat (STRs) and sex specific Amelogenin analysis of blood samples from neurosurgical female transfused patients

Blood transfusion and its effects on DNA profiles of an individual is an important issue in the forensic context. In the present study, the effects of unfiltered whole male blood transfusion in seven female subjects were investigated by PCR-based assays on serial post-transfusion blood samples. PCR analysis of specific short tandem repeat (STR) primer pair to CSF1PO, TPOX, TH01, F13A01, FESFPS, vWA and sex specific Amelogenin loci for banding pattern of alleles generated from the pre- and post-transfusion of seven female recipients and their corresponding donors were studied. Pre- and post-transfusion DNA profiles of all the seven female recipients were found to be consistent with no evidence of the male and female donor genetic material. It is concluded that currently used PCR-based STRs and sex specific Amelogenin loci DNA profiling techniques in forensic science are reliable and informative for paternity and identity purposes in situations of transfusion of 1 or 2 U of unfiltered whole male and female blood (> 72 h old) to female recipient up to 24 h post-transfusion.

Restriction fragment length polymorphism and polymerase chain reaction: HLA-DQA1 and polymarker analysis of blood samples from transfusion recipients

The effect of blood transfusion on DNA profiles of an individual is a significant issue in the forensic context. In the present study, the effects of blood transfusion in 5 recipients were studied by performing restriction fragment length polymorphism and polymerase chain reaction HLA-DQA1 and Polymarker (LDLR, GYPA, HBGG, D7S8, and GC) assays (Roche Molecular Systems, Branchburg, NJ) on serial posttransfusion blood samples. Pretransfusion and posttransfusion DNA profiles of all 5 recipients were consistent with no evidence of the donor genetic material. Currently used DNA profiling techniques in forensic science are reliable and informative for paternity and identity purposes in situations involving transfusion of 1 or 2 U of blood up to 24 hours posttransfusion.

Quantitative polymerase chain reaction-based assay with fluorogenic Y-chromosome specific probes to measure bone marrow chimerism in mice

A quantitative duplex polymerase chain reaction (PCR) method using the LightCycler detection system was developed to generate a reproducible and convenient method to quantitatively measure chimeric states in murine transplantational models using male and female BALB/c mice.

MATERIALS AND METHODS

DNA mixtures isolated from male and female murine BALB/c bone marrow cells were analyzed with Y-chromosome and control autosomal GAPDH specific primers by either monoplex or duplex real-time quantitative PCR using the LightCycler detection system to determine chimeric states.

RESULTS

High specific Y-chromosome and control autosomal GAPDH primers gave a detection sensitivity of approximately 0.01% using LightCycler PCR. Analysis of standard curve distribution of diluted DNA samples accurately matched the proportional dilutions. Y6 primers run on male DNA samples against a female background showed amplification slope initiations reflecting the amounts of male DNA contained in these mixtures. Mixed samples run with GAPDH primers showed amplification corresponding to 100% DNA amounts of limiting dilution runs which were used as controls. Calculated engraftment generated by monoplex PCR lacked reproducibility. Quantitation using duplex PCR using specific detection probes for both Y-chromosome Y6 and autosomal GAPDH primer amplicons allowed precise and reproducible calculations of engraftment levels.

CONCLUSION

Duplex PCR using specific detection probes for Y-chromosome Y6 and autosomal GAPDH primer amplicons allows for rapid, precise and specific engraftment determination after transplantation of male BALB/c marrow cells into female BALB/c recipients.

Survival of transfused donor white blood cells in HIV-infected recipients

The appearance and expansion of donor white blood cells in a recipient after transfusion has many potential biologic ramifications. Although patients with HIV infection are ostensibly at high risk for microchimerism, transfusion-associated graft-versus-host disease (TA-GVHD) is rare. The purpose of this study was to search for sustained microchimerism in such patients. Blood samples were collected from 93 HIV-infected women (a subset from the Viral Activation Transfusion Study, an NHLBI multicenter randomized trial comparing leukoreduced versus unmodified red blood cell [RBC] transfusions) before and after transfusions from male donors. Donor lymphocytes were detected in posttransfusion specimens using a quantitative Y-chromosome-specific polymerase chain reaction (PCR) assay, and donor-specific human leukocyte antigen (HLA) alleles were identified with allele-specific PCR primers and probes. Five of 47 subjects randomized to receive nonleukoreduced RBCs had detectable male lymphocytes 1 to 2 weeks after transfusion, but no subject had detectable male cells more than 4 weeks after a transfusion. In 4 subjects studied, donor-specific HLA haplotypes were detected in posttransfusion specimens, consistent with one or more donors' cells. None of 46 subjects randomized to receive leukoreduced RBCs had detectable male lymphocytes in the month after transfusion. Development of sustained microchimerism after transfusion in HIV-infected patients is rare; HIV-infected patients do not appear to be at risk for TA-GVHD.

Lack of evidence for an increased microchimerism in the circulation of patients with Sjögren's syndrome

OBJECTIVE

To examine the hypothesis that fetal microchimerism plays a part in the pathogenic process of Sjögren's syndrome (SS).

METHODS

Genomic DNA samples were extracted from peripheral blood whole nucleated cells and the CD34+ cell enriched fraction of patients with SS and healthy women who had male offspring as well as nulliparous women. A Y chromosome-specific sequence was detected as a marker for fetal cells by a nested polymerase chain reaction (PCR) and by DNA hybridisation combined with PCR using specific primers and probes. All procedures were performed with great care to avoid the contamination of male DNA.

RESULTS

A nested PCR and DNA hybridisation combined with PCR was established that can detect a single male cell out of 1.67x10(5) female cells. It was not possible to increase the sensitivity further because the amount of template DNA held in the PCR was limited. When these methods were used, no fetal cells were detected in any samples from patients with SS, though they were detected in whole nucleated cells from two healthy women who had delivered sons previously.

CONCLUSIONS

The findings indicate that circulating fetal cells in patients with SS are uncommon (<1 in 1.67x10(5)), if they exist. With the conventional PCR based methods that were used, it is difficult to evaluate the quantitative difference in circulating fetal cells between patients with SS and healthy women.

Fetal microchimerism in primary biliary cirrhosis

BACKGROUND/AIMS

Recent studies have suggested a role of fetal microchimerism in the pathogenesis of scleroderma. The present study investigated the potential role of fetal microchimerism in primary biliary cirrhosis (PBC), a closely related disease.

METHODS

A quantitative nested polymerase chain reaction was used to detect Y-chromosome sequences in the peripheral blood or the liver of PBC women and controls having male children and no transfusion or miscarriage history.

RESULTS

Male microchimerism was found in the peripheral blood from 45% (9 of 20) of PBC women and 25% (5 of 20) of healthy controls matched for the number of male children and age of the youngest son (p=0.28), and in the liver-biopsy specimens from 33% (5 of 15) of PBC women and 32% (8 of 25) of controls. The level of chimerism did not differ between patients and controls either in blood or in liver. Microchimerism was not related to the severity of the disease but was more frequent in PBC patients with anticentromere antibodies (p=0.049).

CONCLUSIONS

Fetal microchimerism does not seem to play a major role in most cases of PBC. However, the association with anticentromere antibodies suggests a possible role in the subgroup of patients with CREST syndrome or scleroderma.

Analysis of engraftment, graft-versus-host disease, and immune recovery following unrelated donor cord blood transplantation

Unrelated cord blood (UCB) is being used as a source of alternative hematopoietic stem cells for transplantation with increasing frequency. From November 1994 to February 1999, 30 UCB transplant procedures were performed for both malignant and nonmalignant diseases in 27 children, aged 0.4 to 17.1 years. Patients received either HLA-matched (n = 3) or 1- or 2-antigen–mismatched (n = 27) UCB following 1 of 2 standardized preparative and graft-versus-host disease regimens (hyperfractionated total body irradiation, cyclophosphamide, and antithymocyte globulin [ATG] with cyclosporine A and methotrexate; or busulfan, melphalan, and ATG with cyclosporine A and prednisone). The median time to neutrophil and platelet engraftment was 27 days (12-60 days) and 75 days (33-158 days) posttransplantation, respectively. No correlation was noted between neutrophil and platelet engraftment and nucleated cells per kilogram, CD34+ cells per kilogram infused, or cytomegalovirus status of recipient. The cumulative probability of acute grade 2 or greater graft-versus-host disease (GVHD) was 37.2%, and of grade 3 or greater GVHD was 8.8%. No patients developed chronic GVHD. CD4, CD19, and natural killer cell recovery was achieved at a median of 12, 6, and 2 months, respectively. CD8 recovery was delayed at a median of 9 months. Normal mitogen response was achieved at 6 to 9 months. The probability of survival, disease-free survival, and event-free survival at 1 year was 52.3% (34.1%-70.5%), 54.7% (34.5%-74.9%) and 49.6% (29.9%-69.4%), respectively. This series of 30 UCB transplants suggests that although CD8 cell recovery is delayed, the pattern of immune reconstitution with UCB is similar to that reported for other stem cell sources.

Analysis of engraftment, graft-versus-host disease, and immune recovery following unrelated donor cord blood transplantation

Unrelated cord blood (UCB) is being used as a source of alternative hematopoietic stem cells for transplantation with increasing frequency. From November 1994 to February 1999, 30 UCB transplant procedures were performed for both malignant and nonmalignant diseases in 27 children, aged 0.4 to 17.1 years. Patients received either HLA-matched (n = 3) or 1- or 2-antigen–mismatched (n = 27) UCB following 1 of 2 standardized preparative and graft-versus-host disease regimens (hyperfractionated total body irradiation, cyclophosphamide, and antithymocyte globulin [ATG] with cyclosporine A and methotrexate; or busulfan, melphalan, and ATG with cyclosporine A and prednisone). The median time to neutrophil and platelet engraftment was 27 days (12-60 days) and 75 days (33-158 days) posttransplantation, respectively. No correlation was noted between neutrophil and platelet engraftment and nucleated cells per kilogram, CD34+ cells per kilogram infused, or cytomegalovirus status of recipient. The cumulative probability of acute grade 2 or greater graft-versus-host disease (GVHD) was 37.2%, and of grade 3 or greater GVHD was 8.8%. No patients developed chronic GVHD. CD4, CD19, and natural killer cell recovery was achieved at a median of 12, 6, and 2 months, respectively. CD8 recovery was delayed at a median of 9 months. Normal mitogen response was achieved at 6 to 9 months. The probability of survival, disease-free survival, and event-free survival at 1 year was 52.3% (34.1%-70.5%), 54.7% (34.5%-74.9%) and 49.6% (29.9%-69.4%), respectively. This series of 30 UCB transplants suggests that although CD8 cell recovery is delayed, the pattern of immune reconstitution with UCB is similar to that reported for other stem cell sources.

Presence of Donor- and Recipient-derived DNA in Cell-free Urine Samples of Renal Transplantation Recipients: Urinary DNA Chimerism

Background: Previous studies have indicated that microchimerism is present in body tissues, peripheral blood, and plasma of recipients after organ transplantation. We hypothesize that donor-derived DNA may also be present in cell-free urine of renal transplant recipients and that the concentrations of urine DNA may be correlated with graft rejection.

Methods: Thirty-one female patients who had renal transplantation were enrolled in the study. In women with male organ donors, the SRY gene on the Y chromosome was used as a marker for donor-derived DNA. Real-time quantitative PCR for the SRY and β-globin genes was carried out on cell-free urinary DNA from these patients. Serial urine samples from a female renal transplant recipient undergoing an acute rejection episode were also collected and analyzed with the β-globin quantitative PCR system.

Results: SRY sequences were detected in the urine of 14 of 17 female patients with male organ donors. None of the 14 patients with female organ donors had detectable SRY sequences in urinary DNA. The median fractional concentration of donor-derived DNA was 8.7% (interquartile range, 1.9–26.4%). During the acute rejection episode, urinary concentrations of the β-globin gene were markedly increased, with the concentrations returning rapidly to normal following antirejection treatment.

Conclusions: Our results demonstrate that urinary DNA chimerism is present following renal transplantation. The measurement of urinary DNA using quantitative PCR may be useful for the diagnosis and monitoring of graft rejection.

Prospective study of microchimerism in transplant recipients

BACKGROUND

We evaluated peripheral blood microchimerism in 48 consecutive organ transplant recipients (35 kidneys, ten livers, one kidney-liver, one kidney-pancreatic islet, one kidney pancreas) up to 12 months post-transplantation. Patients were categorized according to the presence or absence of rejection episodes, and the patterns of microchimerism in the two groups were then compared.

METHODS

DNA was extracted from donor, pre-transplant, and post-transplant peripheral blood samples. Several polymerase chain reaction (PCR)-based assays were developed for the detection of microchimerism. Assay sensitivities ranged from 0.0001 to 3%.

RESULTS

Microchimerism was detected only in sex-mismatched cases (male donors and female recipients) using nested PCR for a Y-chromosome marker. There were ten such cases (six kidneys, two livers, and two combined organ transplants). In patients without rejection (n = 7), there was a peak of donor-DNA at 1-3 wk post-transplantation followed by a second peak between 3 wk and 4 months. In patients with biopsy-proven rejection (n = 3), the peaks were absent and the levels of microchimerism were extremely low (< 0.001%). Microchimerism levels declined in all 10 patients and were barely detectable 1 yr post-transplantation. Microchimerism was not detected in the remaining 38 patients despite using a battery of sensitive PCR-based assays.

CONCLUSIONS

In our study, microchimerism was detected using the Y-chromosome PCR assay only and the level of donor-DNA in a given patient varied over time. This study highlights the difficulties in establishing a correlation between microchimerism and transplant tolerance.