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Biomedical subjects

J Löwer

Publications and source records attributed to J Löwer.

At least 19 recordsLinked to original sources
PubMed2004

Detection and characterization of betaretroviral sequences, related to sheep Jaagsiekte virus, in Africans from Nigeria and Cameroon.

Jaagsiekte retrovirus (JSRV) causes ovine pulmonary adenomatosis (OPA) that resembles bronchioloalveolar carcinoma (BAC) in humans. To test the possible role of JSRV in human diseases, DNA specimens from 103 individuals either healthy or suffering from lung carcinomas were analyzed for JSRV sequences. orf-x sequences were detected in 19 of 64 samples and gag-prt sequences in 4 of 38 samples, predominantly in individuals from Africa. Sequences obtained from orf-x amplimers varied in-between each other and differed from control endogenous ovine JSRV sequence. No association with lung cancer was found. This is the first report of JSRV-like sequences detected in humans.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed2001

Cold-attenuated live influenza vaccines, a risk-benefit assessment.

The principle of live attenuated influenza vaccines has been known for many decades. However, the pharmaceutical and clinical development according to current regulations, of modern live influenza vaccines based on cold adapted influenza viruses (CAIV) started only recently and these vaccines will most probably become an alternative within the next couple of years to licensed inactivated influenza vaccines that have been used routinely since the early 1940s. In contrast to contemporary trivalent inactivated influenza vaccines, which are administered intramuscularly, trivalent CAIV-based vaccines will be administered intranasally as a spray. Quality, safety and efficacy aspects related to CAIV vaccines as well as possible risks linked to the widespread use of these vaccines will be discussed in the following overview and compared to established influenza vaccines. Moreover, issues of practicality of CAIV vaccines focusing on the necessity of an annual update of influenza vaccines are addressed.

Animals↗
PubMed2001

Parvovirus B19 DNA in plasma pools and plasma derivatives.

BACKGROUND AND OBJECTIVES: Human parvovirus B19 (B19) has been transmitted by various plasma-derived medicinal products. The aim of this study was to determine the frequency and the level of B19 DNA contamination in plasma pools destined for fractionation and in a broad range of plasma derivatives. In addition, removal of B19 DNA by the manufacturing process was investigated in cases where corresponding samples from plasma pool and product were available. MATERIALS AND METHODS: Plasma pool samples and blood products were tested for B19 DNA by nested polymerase chain reaction (PCR), and the viral DNA content was determined by TaqMan quantitative PCR. RESULTS: Two-hundred and twenty two of 372 plasma pools for fractionation contained B19 DNA at concentrations of 10(2)-10(8) genome equivalents/ml (geq/ml). While approximately 65% of the DNA-positive plasma pools were only moderately contaminated (< 10(5) geq/ml), 35% contained > 10(6) geq/ml. High frequencies of contamination were detected in Factor VIII (79 of 91), prothrombin complex concentrates (38 of 43) and Factor IX (41 of 62), where the concentration of B19 DNA ranged between 102 and 107 geq/ml. A lower level of B19 DNA contamination was found in antithrombin III (five of 26 samples), in anti-D immunoglobulins (three of 37 samples) and in albumin (four of 51 samples), with levels ranging between 10(2) and 10(3) geq/ml. Furthermore, investigation of plasma pools for solvent/detergent plasma (S/D plasma), from two manufacturers, revealed B19 DNA in 15 of 66 batches at concentrations of 10(2)-10(8) geq/ml. Similar concentrations were detected in the corresponding final S/D plasma products. Anti-B19 immunoglobulin G (IgG) was found in plasma pools and S/D plasma at concentrations of approximately 40 IU/ml. CONCLUSION: Although positive PCR results do not necessarily reflect infectivity, these data show that B19 is a common contaminant in plasma pools and in plasma-derived medicinal products. Considering the resistance of animal parvoviruses to inactivation by heat and chemical agents, and the absence of specific information for B19, the risk of B19 transmission by plasma products should be considered. Physicians should be aware of this problem when treating patients of B19-related risk groups. The plasma fractionation industry should continue their efforts to avoid B19 contamination of plasma derivatives and develop methods which are effective in removing/inactivating parvovirus B19.

Blood↗
PubMed2001

Causality assessment of suspected virus transmission by human plasma products.

BACKGROUND: Causality assessment of reports on suspected virus transmission is crucial for early detection of infectious plasma products. Commonly used algorithms, such as the WHO criteria, do not meet the specific requirements for causality assessment of suspected virus transmission. STUDY DESIGN AND METHODS: A special algorithm, based on nucleic acid amplification and gene sequencing technology, effectiveness of validated virus-inactivation methods, empirical data concerning the safety record of the product, and information on batch-related infection clusters, was developed. The algorithm is focused on laboratory test results or otherwise standardized data, with few clinical data being required. To facilitate practical application, the algorithm has been converted into a graphical decision tree. RESULTS: The feasibility of the algorithm is shown by causality assessment of sample cases. Three cases are presented with the details of each case used in the 12-question checklist. The answers provided by the checklist led to the causality classification. CONCLUSION: The algorithm is a tool for evaluating reports of suspected virus transmission in a standardized manner. It thus has the potential to improve early signal detection in pharmacovigilance of plasma products by confirmation or exclusion of suspected infectivity in most cases.

Adult↗
PubMed2001

Rec (formerly Corf) function requires interaction with a complex, folded RNA structure within its responsive element rather than binding to a discrete specific binding site.

It was recently reported that the human endogenous retrovirus HTDV/HERV-K encodes the regulatory protein Rec (formerly designated Corf), which is functionally equivalent to the nuclear export adapter proteins Rev of human immunodeficiency virus and Rex of human T-cell leukemia virus. We have demonstrated that the Rec protein interacts with a characteristic 429-nucleotide RNA element, the Rec-responsive element (RcRE), present in the 3' long terminal repeat of HTDV/HERV-K transcripts. In analogy to the Rev and Rex proteins, which have distinct RNA binding sites in their responsive elements, we have proposed that Rec may also have a defined binding site in the RcRE. In this report, we demonstrate that not every HTDV/HERV-K copy present in the human genome contains an active RcRE, and we characterize mutations that abrogate Rec function. In addition, we demonstrate that Rec function requires binding to a complex, folded RNA structure rather than binding to a discrete specific binding site, in contrast to Rev and Rex and their homologous responsive elements. We define four stem-loop structures in the RcRE that are essential for Rec function. Finally, we demonstrate that both Rev and Rex can mediate nuclear export through the RcRE but that their binding sites are different from each other and from that of Rec.

Base Sequence↗
PubMed2000

Corf, the Rev/Rex homologue of HTDV/HERV-K, encodes an arginine-rich nuclear localization signal that exerts a trans-dominant phenotype when mutated.

Regulation of nucleo-cytoplasmic export of viral transcripts by a viral protein (Rev/Rex) is a characteristic feature in the replication cycle of complex retroviruses. We recently reported that the endogenous retrovirus family HTDV/HERV-K encodes a protein, Corf, that is a cellular Counterpart of Rev/Rex function and thus a new component of nucleo-cytoplasmic pathways. In HTDV/HERV-K-expressing cells, Corf is localized within the nucleoli. Here we describe the nuclear localization signal (NLS) of the Corf protein. Mutations in the NLS lead to cytoplasmic accumulation of the mutated protein and abrogate Corf function in a trans-dominant way.

Amino Acid Sequence↗
PubMed1999

A new cluster of hepatitis A infection in hemophiliacs traced to a contaminated plasma pool.

Recently, several clusters of hepatitis A have been observed among hemophiliacs linked to factor VIII concentrates treated for virus inactivation solely with the solvent/detergent (S/D) method, a procedure that does not affect nonenveloped viruses such as the hepatitis A virus (HAV). A new outbreak of hepatitis A in six hemophiliacs treated with the same lot of a factor VIII preparation occurred recently in Germany. The objective of the study was to clarify whether these diseases were caused by the administration of the S/D-treated plasma product, rather than a community-acquired infection. Polymerase chain reactions designed to detect HAV nucleic acid have been carried out in the implicated factor VIII lots, in the corresponding plasma pools, and in serum samples of four out of six infected individuals. The nucleic acid sequences were determined in samples that resulted in positive amplification products. HAV sequences were found in one of the two plasma pools used for manufacture of the incriminated product, in the incriminated lot itself, and in all recipient sera tested so far, although the latter were collected up to 7 weeks after the onset of jaundice. The sequences obtained were completely identical, revealing a unique HAV strain of genotype IA. This study provides conclusive evidence that hepatitis A can be transmitted by factor VIII concentrates treated solely by the S/D procedure for virus inactivation. This inactivation method is not effective against nonenveloped viruses. Since a number of hepatitis A transmission episodes have been described with such preparations during the past 10 years, their continued use seems to be questionable unless additional virus removal or inactivation steps are introduced to prevent the transmission of nonenveloped viruses. Molecular approaches again proved to be reliable tools for elucidating the chain of virus transmission.

Adult↗
PubMed1999

Safety issues for plasma derivatives and benefit from NAT testing.

Manufacturing processes for plasma derivatives are in general highly effective for removal or inactivation of enveloped viruses and the products are safe with regard to the clinically important viruses HIV, HCV and HBV. They are not so effective for the elimination for non-enveloped viruses, especially Parvovirus B19 (B19). A certain risk remains of B19 contamination for some plasma derivatives that is caused, firstly, by the occurrence of highly contaminated donations (up to 10(14)genomes/ml) and secondly, by the extreme heat resistance and small size of B19 which makes it difficult to remove or inactivate. NAT is a beneficial tool for detection of virus contamination. It is routinely used for the detection of HCV-RNA in plasma pools, thereby preventing the processing of HCV-RNA positive material. NAT assays may also be valuable for testing the removal of viruses during manufacturing. This may be especially important if a virus cannot be tested by infectivity assays.

Blood Donors↗
PubMed1999

cORF and RcRE, the Rev/Rex and RRE/RxRE homologues of the human endogenous retrovirus family HTDV/HERV-K.

cORF, a protein encoded by the human endogenous retrovirus family HTDV/HERV-K, contains amino acid motifs which resemble the nuclear import and export signals of the viral regulatory proteins Rev (human immunodeficiency virus) and Rex (human T-cell leukemia virus [HTLV]). In this study, we demonstrated that cORF indeed has a Rev-like function and mapped the cORF-responsive RNA element to a sequence in the 3' long terminal repeat, a localization similar to RxRE, the responsive element in HTLV type 1. Accordingly, we have given the element the designation RcRE. cORF and RcRE stabilize unspliced and incompletely spliced viral transcripts and enhance their nuclear export via the CRM1 export pathway. So far, HTDV/HERV-K is the only endogenous retrovirus family with a complex regulation at the posttranscriptional level. It may be regarded as an intermediate in the evolution from simple to complex retroviruses.

Amino Acid Sequence↗
PubMed1999

Expression of the human endogenous retrovirus HTDV/HERV-K is enhanced by cellular transcription factor YY1.

The human endogenous retrovirus HTDV/HERV-K, which resides in moderate copy numbers in the human genome, is expressed in a cell-type-specific manner, predominantly in teratocarcinoma cells. We have analyzed the regulatory potential of the 5' enhancer of the HERV-K long terminal repeat. Protein extracts of HERV-K-expressing teratocarcinoma cell lines (GH and Tera2) and nonexpressing HeLa and HepG2 cells form different protein complexes on the enhancer sequence as detected by electrophoretic mobility shift assays (EMSA). Using competition EMSAs, DNase I footprinting, and supershift experiments, we localized the binding site of these complexes to a 20-bp sequence within the enhancer and showed that the transcription factor YY1 is one component of the HERV-K enhancer complex. Replacement of the YY1 binding site with unrelated sequences reduced expression of the luciferase gene as a reporter in transient-transfection assays.

DNA-Binding Proteins↗
PubMed1999

Oligonucleotide and plasmid DNA packaging into polyoma VP1 virus-like particles expressed in Escherichia coli.

The drug delivery system described here is based on the properties of the capsoid or capsid-like structure resulting from the assembly of polyoma virus capsid protein VP1 expressed in Escherichia coli. The capsid protein VP1 was expressed as a fusion protein with a completely removable N-terminal His6 affinity tag. The pentameric morphology of the recombinant VP1 protein was confirmed by electron microscopy after affinity chromatography and factor Xa cleavage under conditions of low ionic strength. The self-assembly of VP1 capsoids can be induced from purified VP1 pentamers by increasing the ionic strength with (NH4)2SO4. These VP1 capsoid particles were packed in vitro with anti-sense oligonucleotides and plasmid DNA. The loading with DNA was pH-dependent. We observed the highest efficiency at pH 5. DNase I treatment of particles with encapsidated material showed that 37-55% of the bound oligonucleotides and fragments of 1.5-1.8 kb double-stranded DNA were protected against degradation.

Base Sequence↗
PubMed1998

GB virus C/hepatitis G virus and intravenous immunoglobulins.

BACKGROUND AND OBJECTIVES: Different intravenous immunoglobulins (IVIGs) were found to be GB virus C/hepatitis G virus polymerase chain reaction (GBV-C/HGV-PCR)-positive. The potential transmission of this virus to recipients by a PCR-positive IVIG batch was investigated. MATERIALS AND METHODS: Polyclonal IVIGs of different manufacturers and with different virus inactivation procedures were analyzed by GBV-C/HGV-PCR and anti-E2-ELISA. Follow-up sera of 13 participants of a clinical trial performed with a GBV-C/HGV-PCR-positive batch were retrospectively investigated for GBV-C/HGV seroconversion (specific antibodies, viral RNA). RESULTS: Four out of ten IVIGs analysed by GBV-C/HGV-PCR were - at least for some batches - virus genome-positive. Virus inactivation by solvent/detergent treatment resulted in GBV-C/HGV-PCR-negative products. GBV-C/HGV-specific antibodies were detectable in all IVIGs analyzed. There was no transmission of GBV-C/HGV observed when recipients of a large amount of a GBV-C/HGV-PCR-positive batch were analyzed by an antibody test and specific PCR. CONCLUSIONS: Despite PCR positivity of an IVIG preparation no transmission of GBV-C/HGV to recipients was observed. Possible explanations are a sufficient virus inactivation procedure and/or presence of specific antibodies in the final products.

Antibodies, Viral↗
PubMed1997

Frequencies of GB virus C/hepatitis G virus genomes and of specific antibodies in German risk and non-risk populations.

The prevalence of the new flavivirus GB virus C/hepatitis virus G (GBV-C/HGV) in different German populations was investigated by detection of viral genomes and anti-E2 antibodies. While blood donors had an overall prevalence of 10.4% there were increased rates for hemophiliacs (54.7%), hemodialysis patients (30.2%), male homosexuals (30.2%) and intravenous drug users (74.4). Most GBV-C/HGV positive samples were either viral genome positive or antibody positive, exclusively. Samples with the rare constellation "positive for both GBV-C/HGV genome and specific antibody" originated in almost all cases from patients who were additionally infected with HIV or HCV. Probable transmission of GBV-C/HGV by PCR-positive blood transfusions was observed in 5 of 6 cases approximately six months after transfusion.

Blood Donors↗
PubMed1996

The viruses in all of us: characteristics and biological significance of human endogenous retrovirus sequences.

Human endogenous retroviruses (HERVs) are very likely footprints of ancient germ-cell infections. HERV sequences encompass about 1% of the human genome. HERVs have retained the potential of other retroelements to retrotranspose and thus to change genomic structure and function. The genomes of almost all HERV families are highly defective. Recent progress has allowed the identification of the biologically most active family, HTDV/HERV-K, which codes for viral proteins and particles and is highly expressed in germ-cell tumors. The demonstrable and potential roles of HTDV/HERV-K as well as of other human elements in disease and in maintaining genome plasticity are illustrated.

Antibody Formation↗