R. Repp

Detection of a hepatitis B virus variant with a truncated X gene and enhancer II.

SummaryApproximately 15% of the viral genomes in the serum of a hepatitis B carrier were found to exhibit an 8 base-pair deletion within the enhancer II element, which would truncate the X protein by 26 amino acids at the carboxy-terminus.

Absence of free core antigen in anti-HBc negative viremic hepatitis B carriers.

Using enzyme immune assay and immune electron microscopy, we have examined the sera of immune-suppressed anti-HBc negative HBV-infected patients for the presence of HBcAg. Our results suggest that free HBV core particles are absent or present only in minute amounts in the blood of chronic carriers and that at the most, only minimal amounts of core antigen are found on the surface of the virus particles.

Frequency and DNA sequence of tal-1 rearrangement in children with T-cell acute lymphoblastic leukemia

SummaryUsing nested polymerase chain reaction (PCR) a gene rearrangement named tal-1 deletion was found in five of 56 leukemic bone marrow samples from children with T-cell acute lymphoblastic leukemia (ALL). The DNA sequences of the PCR fragments consisted of the known conserved germline sequences in addition to short DNA insertions at the breakpoint region, which were different in each patient. Moreover, one patient was examined at diagnosis and at relapse 11 months later, revealing identical DNA sequences at the rearrangement site. The recombination site of the tal rearrangement therefore may be used as a genetic marker for detecting minimal residual disease in about 10% of T-cell ALL in childhood.

Clinical and immunological aspects of hepatitis B virus infection in children receiving multidrug cancer chemotherapy

For two reasons hepatitis B virus infection is an important problem in patients with cancer. First, multidrug cancer chemotherapy may reactivate or worsen a previously benign chronic HBV infection. Second, patients undergoing cancer chemotherapy are at an increased risk of acquiring and spreading HBV which may result in an endemic infection. HBV reactivation may precipitate into a severe acute disease including fulminant hepatitis. In contrast, the acquisition of HBV during cancer chemotherapy commonly takes a mild clinical course but frequently leads to persistently high viremia. This state of immunotolerance to viral antigens allows viral replication without any sign of liver cell destruction. Withdrawal of chemotherapy does not cause significant changes if infection occurred during cytotoxic chemotherapy. Infection with HBV during cancer chemotherapy, therefore, may be considered as a model of an induced antigen-specific immunotolerance. In agreement with this hypothesis, vaccination against HBV during cancer chemotherapy does not prevent spread of HBV in oncology wards as it does not produce significant anti-HBs titers. Furthermore, vaccination even suppresses the immune response to later booster doses after chemotherapy has been withdrawn.

Secondary acute myeloid leukemia with translocation (4;11) and MLL/AF4 rearrangement in a 15-year-old boy treated for common acute lymphoblastic leukemia 11 years earlier

SummarySecondary acute myeloid leukemia occurring in a 15-year-old boy 11 years after initial treatment of a common lymphoblastic leukemia (c-ALL) is described. Initial complete remission was terminated after 4 years by an isolated testicular relapse, followed by first bone marrow relapse within 18 months. After he achieved remission again, an allogeneic bone marrow transplantation from his HLA-identical brother was performed. Five years and 9 months later, the patient developed thrombocytopenia, leukopenia, and anemia, but bone marrow biopsies at this time demonstrated only myelofibrosis, with no blast cell population present. A polymerase chain reaction assay of a peripheral blood sample recognized the mRNA fusion region for the MLL/AF4 rearrangement, i.e., the molecular equivalent of the translocation (4;11)(q21,q23). Four weeks later, a blast cell population with AML-M1 morphology according to the FAB classification appeared in the bone marrow, and translocation (4;11) was detected by cytogenetics. Thus, secondary leukemias with chromosomal 11q23 rearrangement can develop after a long latency period and can be diagnosed earlier with the PCR technique.

A new fingerprint method for sequence analysis of chromosomal translocations at the genomic DNA level

Chromosomal rearrangements constitute a significant feature of leukemogenesis and malignant transformation in general. Nucleotide patterns in the immediate vicinity of the break point may provide important information about the underlying causalities, eg illegitimate recombination events mediated by topoisomerase II, Alu repeats, or VDJ recombinase. In order to facilitate the determination of those DNA patterns, we developed a new fingerprint approach. In a first step, two DNA fragments were independently amplified by long distance PCR: the genomic region carrying the break point and the normal nonrearranged counterpart. Subsequently, both PCR products were digested with restriction enzymes, end-labelled with a fluorescent dye, and subjected to high resolution polyacrylamide gel electrophoresis. By comparing the restriction patterns of the rearranged and the nonrearranged PCR fragments, the break points could be easily localized within a size range coverable by a single sequencing reaction. Finally, the exact DNA sequence across the break point was directly determined. The ‘fingerprint’ technique is fast, reliable and enables the assay of multiple samples in parallel.

Detection of transcriptionally active hepatitis B virus DNA in peripheral mononuclear blood cells after infection during immunosuppressive chemotherapy using the polymerase chain reaction.

Using PCR we have studied mononuclear peripheral blood leucocytes (PMBLs) from HBV-infected immunosuppressed patients in order to detect the presence of HBV genomes. Our results indicate that non-transient PMBL infection is common in immunotolerant carriers. In addition, the presence of pregenomic mRNA sequences suggests that virus replication may take place in PMBLs, possibly implicating the latter as a source of virus after replication has ceased in the liver.

Rapid detection of mitochondrial deletions by long-distance polymerase chain reaction

Sir: Deletions within the mitochondrial genome may be associated with diverse clinical phenotypes ranging from maternally transmitted adult-onset diabetes mellitus and benign nonprogressive ptosis to devastating multisystem disorders such as Leigh disease, Kearns-Sayre syndrome and Pearson bone marrow/pancreas syndrome [4]. Mitochondrial DNA (mtDNA) deletions have usually been identified by Southern blot hybridisation or by amplification of multiple overlapping DNA fragments in different polymerase chain reaction (PCR) assays. In order to cover almost the entire mitochondrial genome of 16569 basepairs by a single PCR reaction we have applied the newly developed long-distance PCR protocol for amplification of mtDNA [2]. This assay mainly differs from conventional PCR by the use of the thermostable Thermus thermophilus DNA polymerase with intrinsic proofreading activity providing amplification of DNA fragments up to 40 kb. Proofreading activity corrects nucleotide misincorporation which might otherwise prematurely terminate DNA synthesis thus overcoming the limitation of DNA fragment synthesis >4-5 kh in conventional PCR reactions. In order to amplify a DNA fragment of 15662 basepairs covering all clinically relevant deletions of mtDNA reported to date, total DNA from peripheral blood mononuclear cells from healthy donors and from a patient with Pearson syndrome was used [3]. This patient suffered from refractory sideroblastic anaemia, thrombocytopenia, neutropenia and exocrine pancreatic dysfunction since early infancy. Despite resolution of haematopoetic abnormalities within the first 3 years of life, the patient died at the age of 4 years due to progredient neurodegeneration and respiratory insufficiency. Long-distance PCR was performed as follows: PCR primers were located at po1% Agarose Gel

Quantification of leukaemic cells based on heteroduplex formation of tal-1 gene sequences after PCR coamplification

Summary Based on the high sensitivity of the polymerase chain reaction (PCR) several assays have already been described which can be applied to monitor minimal residual disease in patients with leukaemia. However, most of these approaches are only qualitative or semiquantitative at best. Moreover, the semiquantitative assays require rather largescale procedures such as oligonucleotide hybridization or sampling of aliquots during the exponential phase of PCR amplification, which is time consuming and may be error prone.

Characterization of chromosome 8 abnormalities by fluorescence in situ hybridization in childhood B-acute lymphoblastic leukemia/non-Hodgkin lymphoma☆

Using fluorescence in situ hybridization (FISH), we studied chromosome 8 abnormalities in 30 children with mature B-cell acute lymphoblastic leukemia (B-ALL) or B-cell non-Hodgkin lymphoma (B-NHL). FISH was performed on metaphase spreads and interphase nuclei with a whole chromosome 8 painting probe. Fifteen patients were studied retrospectively after metaphases from the malignant cell specimen had already been G-banded. When interphase nuclei were examined, FISH was able to confirm t(8;14)(q24;q32) in all nine patients positive by previous G-banding. FISH, however, was positive in metaphase spreads from only seven patients. Another 15 patients were included in a prospective study. In six of them (40%), a translocation involving chromosome 8 was shown by a split small segment (8q24-8qter) on interphase nuclei. Analysis of metaphase spreads showed only three positive cases each by FISH or G-banding, respectively, with corresponding results in two patients. By interphase FISH, trisomy of chromosome 8 also was detectable. In three patients shown by G-banding to have trisomy, interphase FISH study showed high scores of three chromosome 8 signal positive cells. There was no cross-hybridization to other chromosomes interfering with FISH analysis. FISH analysis on interphase nuclei using a whole chromosome 8 hybridization probe will supplement and can be more sensitive than metaphase cytogenetic techniques for detection of chromosome 8 rearrangements in B-ALL/NHL.