Biomedical subjects

Joachim Hahn

Publications and source records attributed to Joachim Hahn.

9 recordsLinked to original sources

PubMed2006

Monitoring of the JAK2-V617F mutation by highly sensitive quantitative real-time PCR after allogeneic stem cell transplantation in patients with myelofibrosis.

The JAK2-V617F mutation occurs in about 50% of patients with myelofibrosis and might be a reliable marker to monitor residual disease after allogeneic stem cell transplantation. We describe a new, highly sensitive (>or= 0.01%) real-time polymerase chain reaction (PCR) to monitor and quantify V617F-JAK2-positive cells after dose-reduced allogeneic stem cell transplantation. After 22 allogeneic stem cell transplantation procedures in 21 JAK2-positive patients with myelofibrosis, 78% became PCR negative. In 15 of 17 patients (88%), JAK2 remained negative after a median follow-up of 20 months. JAK2 negativity was achieved after a median of 89 days after allograft (range, 19-750 days). A significant inverse correlation was seen for JAK2 positivity and donor-cell chimerism (r:-0.91, P<.001). Four of 5 patients who never achieved JAK2 negativity fulfilled during the entire follow-up all criteria for complete remission recently proposed by the International Working Group, suggesting a major role for JAK2 measurement to determine depths of remission. In one case, residual JAK2-positive cells were successfully eliminated by donor lymphocyte infusion. In conclusion, allogeneic stem cell transplantation after dose-reduced conditioning induces high rates of molecular remission in JAK2-positive patients with myelofibrosis, and quantification of V617F-JAK2 mutation by real-time PCR allows the detection of minimal residual disease to guide adoptive immunotherapy.

Adult↗

PubMed2006

Monocyte-derived cells express CYP27A1 and convert vitamin D3 into its active metabolite.

CYP27A1 catalyses hydroxylations in the biosynthesis of bile acids and the bioactivation of vitamin D3. We investigated the expression of CYP27A1 in human monocytes, monocyte-derived macrophages, and dendritic cells on mRNA and protein levels as well as its enzymatic activity in comparison with the expression of CYP27B1 and CYP24A1. Macrophages showed a strong expression of CYP27A1, whereas monocytes and dendritic cells expressed low levels of CYP27A1 mRNA. Immunohistochemistry revealed CYP27A1 and CYP27B1 protein expression in macrophages. Accordingly, macrophages converted vitamin D3 into the active metabolite 1,25(OH)2D3. Dendritic cells also metabolized vitamin D3 although to a lesser extent. This could be due to the high expression of CYP24A1, the enzyme that degrades 25(OH)D3 and 1,25(OH)2D3. Our results show that macrophages and dendritic cells are capable to perform both hydroxylation steps of the vitamin D3 metabolism suggesting a possible role of local 1,25(OH)2D3 synthesis by myeloid cells in the skin and gut.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗

PubMed2006

Prognostic significance of NOD2/CARD15 variants in HLA-identical sibling hematopoietic stem cell transplantation: effect on long-term outcome is confirmed in 2 independent cohorts and may be modulated by the type of gastrointestinal decontamination.

To assess the role of NOD2/CARD15 variants on the long-term outcome of allogeneic stem cell transplantation in a genetically homogeneous group, we extended our previous study (cohort I, n = 78) and typed DNA for NOD2/CARD15 single nucleotide polymorphisms (SNPs) from an additional 225 recipients and their HLA-identical sibling donors (cohort II) treated at four other European centers. Results of genotyping were compared with clinical outcome. The strong association of NOD2/CARD15 variants with transplantation-related mortality (TRM) was confirmed in univariate and multivariate analysis; TRM increased from 20% in cohort I/22% in cohort II in recipient/donor pairs without any NOD2/CARD15 variants to 47% in cohort I/32% in cohort II in the presence of one variant in either donor or recipient and further to 57% in cohort I/74% in cohort II in the presence of 2 or more variants (P < .002 in both cohorts). NOD2/CARD15 SNPs were not associated with relapse rate but had a strong impact on overall survival. In an analysis of center effects, the type of gastrointestinal decontamination was the only factor interfering with the prognostic significance of NOD2/CARD15 SNPs. Our data further support an interaction between gastrointestinal defense mechanisms, activation of the innate immune system, and specific transplant-related complications.

Adolescent↗

PubMed2005

Exposure of hematologic patients to parvovirus B19 as a contaminant of blood cell preparations and blood products.

BACKGROUND: Patients with hematologic malignancies often require blood products, and parvovirus B19 is known to be transmitted by this route. Primary infection with parvovirus B19 shows a wide variety of disease manifestation. In immunocompromised patients, symptoms are severe and viral clearance is delayed or missing. STUDY DESIGN AND METHODS: A total of 2123 blood products given to all patients of a hematologic ward over a period of 6 months were retrospectively examined for the presence of parvovirus B19 DNA by an in-house real-time polymerase chain reaction (PCR; TaqMan). Patients who had received B19 DNA-positive blood products were further investigated serologically and by PCR for the presence of parvovirus B19 antibodies and DNA. RESULTS: Twenty-one (1%) of 2123 blood products tested positive for the presence of B19 DNA (2% of pooled products, 0.7% of single-donor products, and 17.6% of allogeneic peripheral blood progenitor cells), the median viral load was 700 genome equivalents per mL. During the study period, 114 patients were treated on the ward, and 14 (12%) of them received B19 DNA-positive blood components. None of them developed symptoms of an acute B19 infection, although one had a short low-level viremia. CONCLUSIONS: Although B19 DNA was detected in 1 percent of blood products given to hematologic patients, the exposure of 12 percent of patients did not result in symptomatic infections.

Adult↗

PubMed2004

Both donor and recipient NOD2/CARD15 mutations associate with transplant-related mortality and GvHD following allogeneic stem cell transplantation.

Single nucleotide polymorphisms (SNPs) of the NOD2/CARD15 gene resulting in a diminished nuclear factor-kappaB (NF-kappaB) response to bacterial cell wall products have been associated with an increased incidence of Crohn disease. To assess a possible contribution of NOD2/CARD15 mutations to graft-versus-host disease (GvHD) and complications following allogeneic stem cell transplantation, we retrospectively typed DNA from donor/recipient pairs in 169 consecutive patients receiving transplants from related or unrelated donors. Mutated alleles were observed in 21% of patients and in 14% of donors. Cumulative incidence of 1-year, transplant-related mortality rose from 20% in donor/recipient pairs without mutated SNPs to 49% in pairs with recipient mutations (P =.03) and 59% in pairs with donor mutations (P <.005), and was highest in 12 pairs with mutated alleles in both donor and recipients (83%; P <.001). Similar associations were observed for severe overall and severe gastrointestinal GvHD. The impact of NOD2/CARD15 mutations was more prominent for HLA-identical sibling transplantations but was also observed in unrelated donor transplantation. Mutations proved to be independent risk factors for transplant-related mortality. Our findings indicate a major role of monocyte/macrophage dysfunction in the pathophysiology of GvHD and strongly suggest a future risk assessment or even donor selection through NOD2/CARD15 typing.

Adolescent↗

PubMed2004

Quantitation of Epstein-Barr virus mRNA using reverse transcription and real-time PCR.

Monitoring of Epstein-Barr virus (EBV) infection and reactivation in immunocompromized patients (e.g., after organ or bone-marrow transplantation) is based mainly on serological assays and detection of viral DNA. For further characterization of virus reactivation and monitoring of viral transcription we established real-time RT-PCR assays using TaqMan technology to sensitively quantify viral transcripts expressed at different times of the lytic cycle: for BZLF1, an immediate early transactivator initiating the transition from latency to lytic replication, for the DNA-polymerase BALF5 and for the major viral glycoprotein gp350/220 (BLLF1). RNA-isolation was optimized to eliminate contaminating DNA. Preparations were shown to be virtually DNA-free for up to 10(6) copies of RNA. With our PCR systems, it is possible to detect 10 copies of DNA or 100 copies of RNA per reaction as shown with serial dilutions of DNA-plasmids or in vitro transcribed RNA, respectively. This corresponds to a detection limit of 8 x 10(2) copies/10(6) peripheral blood mononuclear cells (PBMCs). Evaluation of this system showed that even in healthy carriers borderline levels of BLLF1 mRNA were sometimes detectable. In patients with acute infectious mononucleosis (IM) viral transcripts were regularly found in varying concentrations. Extremely high levels of all three mRNA species could be seen in a patient after bone-marrow transplantation monitored during an episode of lymphoproliferation which regressed during treatment with acyclovir and transfusion of donor T-cells. This sensitive and reproducible method to detect and quantify different transcripts of EBV can be used to closely monitor reactivation of EBV, e.g., in immunocompromized patients.

DNA, Viral↗

PubMed2004

Long-term parvovirus B19 viraemia associated with pure red cell aplasia after allogeneic bone marrow transplantation.

BACKGROUND: Parvovirus B19 infection is associated with a variety of symptoms like erythema infectiosum, anaemia and arthritis. In immunocompetent persons, viraemia is usually cleared a few weeks after infection. OBJECTIVE: An immunocompromised adult female patient was persistently infected with B19 after allogenic bone marrow transplantation (BMT) and developed chronic anaemia. STUDY DESIGN: B19-specific antibodies were determined by ELISA and viral load was assessed using a quantitative real time B19 PCR. The patient was evaluated clinically. RESULTS: Two years after successful BMT, the patient received intensified immunosuppressive treatment, erythropoetin and erythrocyte concentrates due to chronic graft-versus-host disease with renal failure. Despite of this treatment, the aplastic anaemia worsened. PCR revealed B19 viraemia with 10(12) geq/ml serum. After 7 months of repeated applications of immunoglobulins and reduction of immunosuppressive treatment, reticulocyte counts and haemoglobin levels normalized and the viral load finally dropped to 10(3) geq/ml serum. One of the back-up samples of the erythrocyte concentrates tested positive, the respective transfusion had been applied 2 months after the beginning of viraemia. CONCLUSIONS: The source of the primary infection remained unclear, but at least re-infection by blood transfusion is likely. Treatment did not result in virus elimination from peripheral blood but in resolvement of symptoms.

Anemia, Aplastic↗

PubMed2002

Septicemia due to Acinetobacter junii.

Acinetobacter spp. are considered to be emerging nosocomial pathogens. Acinetobacter junii is a rare cause of disease in humans and was associated mainly with bacteremia in preterm infants and pediatric oncologic patients. In this report we describe a case of catheter-related infection by A. junii in an adult oncologic patient. Application of molecular methods for precise species identification of Acinetobacter spp. will help to further clarify their role as human pathogens.

Acinetobacter↗

PubMed2002

Serum cholesterol levels in neutropenic patients with fever.

Hypocholesterolemia, which often accompanies infectious diseases has been suggested to serve as a prognostic marker in hospitalized patients. Even though patients with chemotherapy-induced leukopenia are at high risk of infection and mortality, only limited information is available on serum cholesterol levels in these patients. We therefore measured serum cholesterol levels in 17 patients with hematological malignancies during chemotherapy-induced neutropenia and correlated it with clinical outcome. Patients with fever (>38.5 degrees C) showed a significant decrease in serum cholesterol levels within 24 hours. Eight days after onset of the fever non-survivors had significantly lower serum cholesterol levels (median 2.09 mmol/l, range 0.49-2.79, n=6) compared to survivors (median 3.23 mmol/l, range 1.68-4.86, n=11). Cholesterol levels in survivors returned to baseline levels at the time of discharge from the hospital. At the onset of fever, serum levels of inflammatory cytokines interleukin-6, tumor necrosis factor (TNF) and soluble TNF receptors p55 and p75 were elevated in all patients, but only TNF and TNF receptor p75 levels were significantly different in survivors and non-survivors. Our data suggest that a decrease in serum cholesterol levels is a prognostic marker in neutropenic patients with fever. Release of inflammatory cytokines may in part be responsible for hypocholesterolemia in these patients.

Antigens, CD↗