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J Köck

Publications and source records attributed to J Köck.

At least 19 recordsLinked to original sources
PubMed2002

Mutations of the serine protease inhibitor, Kazal type 1 gene, in patients with idiopathic chronic pancreatitis.

OBJECTIVE: The pathogenesis of chronic pancreatitis (CP) is poorly understood. Genetic studies revealed mutations in the cationic trypsinogen gene and an increased frequency of cystic fibrosis gene mutations in patients with CP. Recently, a point mutation (N34S) in the gene encoding the serine protease inhibitor, Kazal type 1 (SPINK1), was found in approximately 20% of patients with CP. The aim of our study was to determine the frequency of the N34S SPINKI gene mutation in a well-defined patient cohort with idiopathic CP (ICP) and to compare the incidence with healthy controls. In addition, we investigated the impact of this mutation on the long-term course of CP. METHODS: Fourteen patients with early-onset and four patients with late-onset CP of our well-defined pancreatitis cohort were enrolled in the present study, and 397 healthy individuals served as a control population. Coding exonic and the flanking intronic sequences of SPINK1 were investigated by direct DNA sequencing. The mutations found were confirmed by melting curve analysis. In addition, the N34S mutation was detected by analyzing the DNA fragments generated by digestion with restriction enzyme TspR I. Clinical data of patients with the N34S mutation were compared with those without mutations. RESULTS: The N34S mutation was detected in six of 14 (43%) patients with early-onset ICP. One patient was homozygous, and five patients were heterozygous for this mutation. The N34S mutation in a heterozygous state was found in four of 397 healthy controls (1.0%). The different allele frequency observed (seven of 28 vs four of 794) was significant (odds ratio = 66, 95% CI = 18-242, p < 0.0001). The clinical course was similar in patients with a mutation compared with those without a mutation. No other SPINKI mutations were detected. The N34S mutation was not found in patients with late-onset ICP. CONCLUSIONS: Our results indicate that the N34S mutation in the SPINKI gene is strongly associated with ICP, especially with the early-onset type. The natural course is similar in patients with mutations compared with SPINK1 mutation-negative patients. The N34S mutation may easily be screened for by restriction digestion with TspR I.

Adult↗
PubMed2001

Inhibition of duck hepatitis B virus replication by intrahepatic expression of an antiviral resistance gene.

Resistance genes coding for inhibitors of hepadnaviral replication, such as ribozymes, antisense RNA, and dominant negative mutants have been shown to be effective in transfected hepatoma cells. In vivo studies, however, are not available to date. Here we expanded the use of the duck hepatitis B virus (DHBV) model for studying antiviral resistance genes in vivo. Animals were experimentally infected by intravenous injection of DHBV-positive serum in ovo. The use of recombinant human adenovirus type 5 and avian adenovirus CELO for gene transfer was evaluated. Adenovirus type 5 transduced more than 95% and CELO less than 1% of embryonic hepatocytes in vivo. Adenovirus type 5 interfered with DHBV replication (viral cross-talk), but this effect was moderate and did not preclude analysis of specific antiviral effects. Thus adenoviral transfer of a dominant negative mutant prior to DHBV infection (intracellular immunization) yielded 100-fold suppression of viral replication compared to the green fluorescent protein marker gene. Neither gene was toxic. These data demonstrate that a prototype anthepadnaviral resistance gene is functional in vivo. Duck embryos represent a useful model for evaluating gene therapeutic strategies in vivo without the need for large scale preparations of gene delivery vehicles.

Adenoviridae↗
PubMed2001

Generation of stable mRNA fragments and translation of N-truncated proteins induced by antisense oligodeoxynucleotides.

Binding of phosphorothioate-modified antisense oligodeoxynucleotides (AS ODNs) to target mRNAs is commonly thought to mediate RNA degradation or block of translation. Here we demonstrate cleavage of target mRNAs within the AS ODN binding region with subsequent degradation of the 5' but not the 3' cleavage product. Some, if not all, 3' mRNA fragments lacked a 5' cap structure, whereas their poly(A) tail length remained unchanged. Furthermore, they were efficiently translated into N-terminally truncated proteins as demonstrated in three settings: production of shortened hepadnaviral surface proteins, alteration of the subcellular localization of a fluorescent protein, and shift of the transcription factor C/EBPalpha isoform expression levels. Thus, AS treatment may result in the synthesis of N-truncated proteins with biologically relevant effects.

Animals↗
PubMed2001

Trypsinogen gene mutations in patients with chronic or recurrent acute pancreatitis.

Three-point mutations (R117H, N211, A16V) within the cationic trypsinogen gene have been identified in patients with hereditary pancreatitis (HP). A genetic background has also been discussed for idiopathic juvenile chronic pancreatitis (IJCP), which closely mimicks the clinical pattern of HP, and alcoholic chronic pancreatitis because only a small number of heavy drinkers develop pancreatitis. This prompted us to screen 104 patients in our well-defined pancreatitis cohort for the currently known cationic trypsinogen gene mutations. The R117H mutation was detected in seven patients (six patients of two clinically classified HP families, one patient with clinically classified IJCP) and the A16V mutation in one IJCP patient. No cationic trypsinogen gene mutations were found in the remaining 96 patients with chronic and recurrent acute pancreatitis of various etiologies. Our results demonstrate the need for genetic testing to exclude HP, particularly in the presence of an atypical or unknown family history. In addition, cationic trypsinogen gene mutations are no predisposing factor in patients with chronic and recurrent acute pancreatitis of different etiologies.

Acute Disease↗
PubMed2001

Efficient infection of primary tupaia hepatocytes with purified human and woolly monkey hepatitis B virus.

The Asian tree shrew, Tupaia belangeri, has been proposed as a novel animal model for studying hepatitis B virus (HBV) infection. Here, we describe a protocol for efficient and reproducible infection of primary tupaia hepatocytes with HBV. We report that human serum interferes with HBV binding to the hepatocytes, thus limiting the maximum multiplicity of infection. Purification of HBV virions by gradient sedimentation greatly enhances virus binding and infectivity. Covalently closed circular DNA was clearly detectable by Southern blot analysis and newly synthesized single-stranded HBV DNA was visible 2 weeks postinoculation. Primary tupaia hepatocytes are also susceptible to infection with the recently discovered woolly monkey hepatitis B virus (WMHBV) but not to woodchuck hepatitis virus infection. Compared to HBV, WMHBV replicated at a higher rate with single-stranded DNA detectable within the first week postinoculation. Primary tupaia hepatocytes should represent a useful system for studying early steps of HBV and WMHBV infection.

Animals↗
PubMed1999

Dominant negative mutants of the duck hepatitis B virus core protein interfere with RNA pregenome packaging and viral DNA synthesis.

Dominant negative (DN) mutants of the hepadnaviral core protein are potent inhibitors of viral replication. We have previously shown that fusion of sequences derived from the duck hepatitis B virus (DHBV) polymerase (Pol), DHBV small surface protein (S), bacterial beta-galactosidase (lacZ), or green fluorescent protein (GFP) to the carboxy terminus of the DHBV core protein yields DN mutants that inhibit viral replication at the posttranslational level. To elucidate the mechanism(s) of their antiviral action, we analyzed the effect of the DN mutants on RNA pregenome packaging and nucleocapsid assembly. Core-Pol and core-S, but not core-lacZ or core-GFP, markedly interfered with RNA pregenome packaging. Nucleocapsid formation was not affected by any of the mutants. The DN core-GFP fusion protein formed mixed particles with wild-type core protein in the cytoplasm of cotransfected cells and interfered with reverse transcription of the viral pregenome. A subpopulation of chimeric nucleocapsids, however, was shown to overcome the block in DNA synthesis and produce mature viral DNA. Thus, at least 2 steps within the viral life cycle can be targeted by DN DHBV core proteins: 1) packaging of the viral pregenome; and 2) reverse transcription within mixed particles. The fact that some mixed particles retain replication competence demonstrates a high structural flexibility of nucleocapsids and indicates a possible mechanism of viral escape.

Animals↗
PubMed1999

[Implication of mutation of hepatitis C virus 1b interferon sensitivity determining region(NS5A aa 2209-2248) response to interferon alpha therapy in patients with chronic hepatitis C].

Hepatitis C virus (HCV) isolates from 12 patients with chronic hepatitis C underwent the sequence analysis. Among the 12 patients, 9 obtained a complete response (CR), 2 partial response (PR) and 1 non--response (NR) after the treatment with IFN-alpha. The results showed that only single amino acid (aa) substitution in iIFN sensitivity determining region (ISDR) (aa 2213 and aa 2218) in 6 cases with CR was observed, while 3 cases of CR and all PR and NR cases had no aa mutation of ISDR. It is suggested that the ISDR in HCV NS5A was yet not identified by our patients.

Adult↗
PubMed1998

Duck hepatitis B virus nucleocapsids formed by N-terminally extended or C-terminally truncated core proteins disintegrate during viral DNA maturation.

Hepadnaviruses are DNA viruses that replicate through reverse transcription of an RNA pregenome. Viral DNA synthesis takes place inside viral nucleocapsids, formed by core protein dimers. Previous studies have identified carboxy-terminal truncations of the core protein that affect viral DNA maturation. Here, we describe the effect of small amino-terminal insertions into the duck hepatitis B virus (DHBV) core protein on viral DNA replication. All insertion mutants formed replication-competent nucleocapsids. Elongation of viral DNA, however, appeared to be incomplete. Increasing the number of additional amino acids and introducing negatively charged residues further reduced the observed size of mature viral DNA species. Mutant core proteins did not inhibit the viral polymerase. Instead, viral DNA synthesis destabilized mutant nucleocapsids, rendering mature viral DNA selectively sensitive to nuclease action. Interestingly, the phenotype of two previously described carboxy-terminal DHBV core protein deletion mutants was found to be based on the same mechanism. These data suggest that (i) the amino- as well as the carboxy-terminal portion of the DHBV core protein plays a critical role in nucleocapsid stabilization, and (ii) the hepadnavirus polymerase can perform partial second-strand DNA synthesis in the absence of intact viral nucleocapsids.

Amino Acid Sequence↗
PubMed1997

Long-term expression of the hepatitis B virus core-e- and X-proteins does not cause pathologic changes in transgenic mice.

BACKGROUND/AIMS: Chronic infections with the human hepatitis B virus can result in liver cirrhosis and primary hepatocellular carcinoma. The reasons for these long-term effects are unclear. The aim of this study was to generate transgenic mice expressing the HBV X- and c/e-gene under authentic and foreign promoter control and to test whether the respective gene products can cause pathologic effects during the lifespan of a mouse. Moreover, the temporal and the tissue-specific regulation of the crucial HBV c/e-gene promoter was analyzed. METHODS: Eight transgenic mouse lines were generated. Four contained the c/e- and X-gene and two contained only the X-gene under authentic promoter control. Two lines expressed only the X-gene under control of the rat insulin promoter/enhancer. Gene expression was tested by protein and mRNA analyses. During an observation period of 2 years, mice were sacrificed and organs subjected to histologic examination. Mice expressing the X-gene in pancreatic beta cells were tested for the development of diabetes. RESULTS: In the liver, slight histopathologic alterations but no neoplastic changes could be observed in mice expressing the X-gene. Activity of the c/e-gene promoter/enhancer was age dependent and was not restricted to hepatocytes. CONCLUSION: No evidence was obtained that long-term expression of the HBV c/e- and X-gene products can cause neoplasia during the lifespan of a mouse.

Animals↗
PubMed1996

Hepatitis B virus nucleic acids associated with human peripheral blood mononuclear cells do not originate from replicating virus.

There have been numerous reports suggesting that human peripheral blood mononuclear cells (PBMCs) can be productively infected with human hepatitis B virus (HBV). We therefore examined whether the PBMCs can be used to establish an in vitro infection system for HBV. Freshly purified PBMCs were incubated with HBV with or without mitogen stimulation. Successful infection was tested using a newly developed PCR method that can differentiate between the relaxed circular (RC) DNA of the virus inoculum and the covalently closed circular (CCC) DNA which is formed only after successful virus entry. This method enables virus uptake to be proven even if the infection is abortive because there is no gene expression because of the lack of liver specific gene expression factors. All attempts to detect CCC DNA after incubation of PBMCs with HBV failed. On the contrary, CCC DNA could easily be detected in infected liver or after in vitro infection of primary human hepatocytes. Because this result appeared to be contradictory to the published data, we analyzed PMBCs isolated from infected patients. We could confirm that HBV DNA and RNA are associated with these cells. However, even after restimulation with mitogens, we could only detect RC DNA. Moreover, we could also demonstrate that viral RNA is present in free virus. Apparently, a certain amount of defective particles do not reverse transcribe the packaged pregenomic RNA. In summary we found no evidence that PMBCs can be infected with HBV and conclude that all previous observations can be explained by adsorbed virus.

Base Sequence↗
PubMed1996

Reactivated fulminant hepatitis B virus replication after bone marrow transplantation: clinical course and possible treatment with ganciclovir.

A female chronic hepatitis B virus carrier (HBV-DNA negative) suffered from simultaneous hepatitis B virus and cytomegalovirus reactivation after in vivo T cell depletion preceding transplantation of an in vitro T cell depleted marrow graft for treatment of acute leukaemia. Interstitial pneumonia developing after bone marrow transplantation was successfully treated with ganciclovir (day 13 until day 46). The initially unnoticed extensive hepatitis B virus replication finally led to clinical hepatitis (day 85) and liver failure (day 96). Liver transplantation was performed, but the patient died from septicaemia. Retrospective analysis of hepatitis B virus DNA revealed that the HBV replication started immediately after T cell depletion and was completely suppressed during ganciclovir administration. Screening for HBV-DNA seems to be mandatory in comparable cases, and antiviral chemotherapy should be seriously considered.

Adult↗
PubMed1996

Uptake of duck hepatitis B virus into hepatocytes occurs by endocytosis but does not require passage of the virus through an acidic intracellular compartment.

The infectious entry pathway of duck hepatitis B virus (DHBV) was investigated with primary duck hepatocytes. Virus uptake was measured by a selective PCR technique which allows for the detection of a successful infection without the need for viral replication or gene expression. To test whether DHBV uptake occurs by endocytosis, the effects of energy depletion were analyzed. The requirement for an acidic intracellular pH was tested with the lysosomotropic agent ammonium chloride. The data show that energy depletion prevents the uptake of DHBV into primary hepatocytes whereas ammonium chloride has no effect. From these data, we conclude that DHBV is taken up by its host cells by endocytosis. However, in contrast to that of most other enveloped viruses, escape of DHBV from the endocytotic route does not depend on an acidic intracellular compartment.

Ammonium Chloride↗
PubMed1995

Recombinant duck interferon: a new reagent for studying the mode of interferon action against hepatitis B virus.

Although interferon is widely used to treat chronic hepatitis B virus infections, its mode of action against hepadnaviruses is largely unknown. This deficit is due mainly to the lack of suitable model systems. The duck system could not be used because purified duck interferon was not available in sufficient quantities. We have now cloned a DNA fragment that contains an intronless gene for duck interferon. The primary translation product consists of 191 amino acids, the N-terminal 30 residues of which constitute a signal peptide. Mature duck interferon is 50% identical to the recently cloned chicken interferon. Sequence homology to mammalian interferons is marginal, but conservation of four cysteine residues and inducibility by virus indicate a distant relationship between duck interferon and mammalian type I interferons. Purified recombinant duck interferon from Escherichia coli is biologically active: it activates the interferon-inducible Mx gene, prevents cell destruction by cytolytic RNA viruses, and has a strong inhibitory effect on duck hepatitis B virus in cultured primary duck hepatocytes. This new reagent should help to define the interferon-sensitive step of the hepadnavirus life cycle. Furthermore, the duck system can now be used for systematic studies of the in vivo effectiveness of interferon in chronic hepatitis B virus infections.

Amino Acid Sequence↗
PubMed1993

Molecular basis of the diversity of hepatitis B virus core-gene products.

All hepatitis B viruses examined to date code for at least two different core-gene products which are referred to as the c- and the e-protein. In the case of the human hepatitis B virus, they are known as the HBcAg and the HBeAg. Although these proteins share most of their primary amino acid sequence, they exhibit quite distinct properties. The e-protein is located in the cytoplasm and the nucleus of infected cells and very efficiently assembles into nucleocapsids. By contrast, the e-protein does not form particles. It enters the secretory pathway and is actively secreted by the cells. Here we describe the biosynthetic pathways by which the c- and e-proteins are expressed and summarize recent data from our laboratory showing that the antigenic and biophysical properties which distinguish the HBeAg from the HBcAg are primarily due to the 10 amino acid long portion of the HBeAg leader sequence that remains attached to the HBeAg after cleavage.

Genes, Viral↗