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Biomedical subjects

M C Jung

Publications and source records attributed to M C Jung.

At least 37 records · Page 2Linked to original sources
PubMed1997

Analysis of T cell activation pathways in patients with liver cirrhosis, impaired delayed hypersensitivity and other T cell-dependent functions.

Patients with cirrhosis of the liver frequently demonstrate anergy in intracutaneous tests and fail to respond to vaccination, suggesting impaired delayed hypersensitivity and other T cell-dependent functions in vivo. T cell activation through the coordinated interaction of different cells of the immune system (B cell, antigen-presenting cells (APC)) is an important step in the induction of cellular and humoral immune responses. Impaired T cell-dependent functions in patients with liver cirrhosis may thus be explained by defective T cell activation. We prospectively investigated T cell activation pathways in 12 patients (nine males, three females) with alcoholic liver cirrhosis (seven Child Pugh stage A and B (CP A + B), five Child Pugh stage C (CP C)) and five healthy controls and compared the in vitro results of T cell activation with data obtained in vivo, e.g. intracutaneous tests and vaccination against hepatitis B surface antigen (HBs-Ag). Five out of eight patients who completed vaccination against hepatitis B virus infection were non-responders; one of the three responders had a non-protective anti-HBs titre. Moreover, three of five patients with alcoholic liver cirrhosis CP A + B, and two out of three with CP C were anergic in intracutaneous tests to a set of diverse antigens. All parameters of T cell activation were normal, including proliferation mediated by CD2, CD3-T cell receptor (TCR) complex, and CD28; acquisition of responsiveness to exogenous IL-2 and IL-4; activation of proteinkinase C (PKC) by phorbol ester and calcium influx by addition of ionomycin. The ability of monocytes to deliver costimulatory signals was preserved in patients with alcoholic cirrhosis. In addition, serum of patients with alcoholic liver disease did not inhibit T cell proliferation. We conclude that, although in patients with alcoholic liver cirrhosis T cell-dependent functions are impaired in vivo, T cell activation pathways are not responsible for the observed immune defect.

Adolescent↗
PubMed1997

Immunodominant CD4+ T-cell epitope within nonstructural protein 3 in acute hepatitis C virus infection.

In acute hepatitis C virus infection, 50 to 70% of patients develop chronic disease. Considering the low rate of spontaneous viral clearance during chronic hepatitis C infection, the first few months of interaction between the patient's immune system and the viral population seem to be crucial in determining the outcome of infection. We previously reported the association between a strong and sustained CD4+ T-cell response to nonstructural protein 3 (NS3) of the hepatitis C virus and a self-limited course of acute hepatitis C infection. In this study, we identify an immunodominant CD4+ T-cell epitope (amino acids 1248 to 1261) that was recognized by the majority (14 of 23) of NS3-specific CD4+ T-cell clones from four of five patients with acute hepatitis C infection. This epitope can be presented to CD4+ T cells by HLA-DR4, -DR11, -DR12, -DR13, and -DR16. HLA-binding studies revealed a high binding affinity for 10 of 13 common HLA-DR alleles. Two additional CD4+ T-cell epitopes, amino acids 1388 to 1407 and amino acids 1450 to 1469, showed a very narrow pattern of binding to individual HLA-DR alleles. Our data suggest that the NS3-specific CD4+ T-cell response in acute hepatitis C infection is dominated by a single, promiscuous peptide epitope which could become a promising candidate for the development of a CD4+ T-cell vaccine.

Acute Disease↗
PubMed1996

Serum levels and in situ expression of TNF-alpha and TNF-alpha binding proteins in inflammatory liver diseases.

Cells respond to tumour necrosis factor-alpha (TNF-alpha) via binding to 75-kDa (type A) and 55-kDa (type B) receptors which have different intracellular signalling pathways and can also circulate as soluble molecules. Both receptors are co-expressed in many tissues, but their relative contributions to cellular TNF responses is for most situations unknown. In patients with viral and non-viral inflammatory liver diseases serum TNF-alpha was determined by an immunoenzymetric assay and soluble type A and B TNF receptors (TNF-alpha r) by enzyme-linked immunological and biological assays (ELIBA). In addition, cellular expression of TNF and its binding proteins were studied in liver biopsies by an indirect immunoperoxidase technique. Secretion of TNF-alpha and upregulation of TNF-alpha r-A were particularly prominent in viral hepatitis. Strong TNF-alpha in-situ production by mononuclear cells could be demonstrated in liver biopsies from patients with acute viral hepatitis. However, TNF-alpha r-A was detected only on hepatocytes. Serum TNF-alpha r-A was elevated two-fold in relative abundance over TNF-alpha r-B and was correlated to serum TNF-alpha (r = 0.6464, P < 0.0001). Soluble TNF-alpha r levels normalized, when the viral hepatitis was cleared, and successful therapy of hepatitis B was associated with a temporary rise of TNF-alpha r-A during the initial flare of aminotransferase. Patients with alcoholic hepatitis had also evidence of TNF-alpha activation but clearly differed from patients with viral induced liver diseases: Soluble TNF-alpha r-A and TNF-alpha r-B were highly elevated in equal proportions. In situ analysis in liver biopsies revealed a distinctive pattern of TNF-alpha r expression with strong cytoplasmic staining for both TNF-alpha r-A and B on scattered hepatocytes in addition to infiltrating mononuclear cells. The data propose that TNF release during antiviral immune responses is predominantly associated with TNF-alpha r-A upregulation and shedding, whereas upregulation and shedding of TNF-alpha r-B is more prominent in alcoholic hepatitis. As cytotoxicity and apoptosis by TNF are mediated mainly via TNF-alpha r-B, our results are consistent with more severe TNF-alpha induced liver damage in alcoholic hepatitis as compared to viral hepatitis.

Antigens, CD↗
PubMed1996

The role of hepatitis C virus specific CD4+ T lymphocytes in acute and chronic hepatitis C.

Since the discovery of hepatitis C virus it has become clear that chronic hepatitis C is a major health problem throughout the world. Because antiviral agents are of limited value in the treatment of chronic hepatitis C, research has focused on the antiviral immune response for the development of both a protective vaccine and effective immunotherapies for established chronic infection. Antiviral antibodies are present in almost all patients with chronic hepatitis C but do not seem to be virus neutralizing, probably due to the high mutational rate of viral envelope proteins. Studies on the antiviral T cell response have revealed the presence of virus-specific CD4+ helper and CD8+ cytotoxic T cells in a substantial proportion of patients with chronic hepatitis C. Recent studies describe an association between strong CD4+ T helper cell activity to certain hepatitis C virus antigens and a self-limited course of acute hepatitis C and possibly also a sustained response to treatment with interferon-alpha. Therapeutic manipulation of the virus-specific T cell response may thus develop into a new approach for prevention and treatment of hepatitis C virus infection.

Acute Disease↗
PubMed1996

Anergic TH1 clones specific for hepatitis B virus (HBV) core peptides are inhibitory to other HBV core-specific CD4+ T cells in vitro.

A strong and transient hepatitis B virus core (HBc)-specific CD4+ T-cell response has been shown to be associated with viral elimination in acute self-limited hepatitis B but to be absent in chronic hepatitis B. So far, little is known about immunological mechanisms involved in the regulation of the HBc-specific CD4+ T-cell response. We studied 28 patients with acute hepatitis B, and frequently a sudden decrease in the HBc-specific CD4+ T-cell response was found between 4 and 8 weeks after disease onset. Thirty-two CD4+ T-cell clones specific for amino acids 50 to 69, 81 to 105, 117 to 131, or 141 to 165 of HBc were isolated from a patient shortly before the peripheral blood mononuclear cell response to most HBc-derived peptides abruptly disappeared. TH1 clones, but not TH0 clones, could be anergized in vitro by stimulation with specific peptides even in the presence of costimulatory cells. Moreover, when anergic cells were mixed with responsive cells, the proliferation of HBc-specific TH1 or TH0 clones was inhibited antigen specifically by anergic cells. The unusual susceptibility of HBc-specific TH1 clones to anergy induction in vitro as well as their potential to inhibit other HBc-specific TH1 and TH0 clones suggests that anergy induction may be involved in the downregulation of the virus-specific immune response during acute hepatitis B in vivo.

CD4-Positive T-Lymphocytes↗
PubMed1995

Possible mechanism involving T-lymphocyte response to non-structural protein 3 in viral clearance in acute hepatitis C virus infection.

In acute hepatitis C virus (HCV) infection only 20-50% of patients spontaneously clear the virus. To characterise the immune reaction during that phase we studied the response of peripheral blood mononuclear cells (PBMC) to the recombinant HCV proteins core, non-structural protein 3 (NS3), NS4, and NS5 in 14 patients with acute hepatitis C. All eight patients with self-limited disease compared with two of six with evolving chronic infection showed an NS3- specific PBMC response (p = 0.015). Of 65 patients with established chronic hepatitis C, five showed a PBMC response to NS3. NS3-specific CD4 T-cell clones from patients with self-limited infection predominantly produced interferon-gamma and may thus support cytotoxic effector mechanisms important for viral clearance.

Acute Disease↗
PubMed1995

Activation of a heterogeneous hepatitis B (HB) core and e antigen-specific CD4+ T-cell population during seroconversion to anti-HBe and anti-HBs in hepatitis B virus infection.

Overcoming hepatitis B virus infection essentially depends on the appropriate immune response of the infected host. Among the hepatitis B virus antigens, the core (HBcAg) and e (HBeAg) proteins appear highly immunogenic and induce important lymphocyte effector functions. In order to investigate the importance of HBcAg/HBeAg-specific T lymphocytes in patients with acute and chronic hepatitis B and to identify immunodominant epitopes within the HBcAg/HBeAg, CD4+ T-cell responses to hepatitis B virus-encoded HBcAg and HBcAg/HBeAg-derived peptides were studied in 49 patients with acute and 39 patients with chronic hepatitis B. The results show a frequent antigen-specific CD4+ T-cell activation during acute hepatitis B infection, a rare HBcAg/HBeAg-specific CD4+ T-cell response among HBeAg+ chronic carriers, and no response in patients with anti-HBe+ chronic hepatitis. An increasing CD4+ T-cell response to HBcAg/HBeAg coincides with loss of HBeAg and hepatitis B virus surface antigen (HBsAg). Functional analysis of peptide-specific CD4+ T-cell clones revealed a heterogeneous population with respect to lymphokine production. Epitope mapping within the HBcAg/HBeAg peptide defined amino acids (aa) 1 to 25 and aa 61 to 85, irrespective of the HLA haplotype, as the predominant CD4+ T-cell recognition sites. Other important sequences could be identified in the amino-terminal part of the protein, aa 21 to 45, aa 41 to 65, and aa 81 to 105. The immunodominant epitopes are expressed in both proteins, HBcAg and HBeAg. Our findings lead to the conclusion that activation of CD4+ T lymphocytes by HBcAg/HBeAg is a prerequisite for viral elimination, and further studies have to focus on the question of how to enhance or induce this type of T-cell response in chronic carriers. The immunodominant viral sequences identified may have relevance to synthetic vaccine design and to the use of peptide T-cell sites as immunotherapeutic agents in chronic infection.

Acute Disease↗
PubMed1995

Mapping of immunodominant CD4+ T lymphocyte epitopes of hepatitis C virus antigens and their relevance during the course of chronic infection.

In acute and chronic viral disease the specific response of CD4+ T lymphocytes to certain viral proteins is an essential part of antiviral effector mechanisms. In hepatitis C virus infection, the contribution of the immune system and particularly of CD4+ T lymphocytes to the pathogenesis of disease is unknown. We serially determined the peripheral blood CD4+ T lymphocyte response to several recombinant hepatitis C virus proteins (core, NS3, NS4, NS5) and 17 overlapping synthetic peptides derived from the core sequence over up to 48 months in 43 patients with chronic hepatitis C; of these, 16 had been treated with interferon alfa (IFN). Twelve of 27 untreated patients, 4 of 4 sustained responders to IFN, 7 of 8 patients with a transient response, and 1 of 4 nonresponders showed a proliferative response to hepatitis C virus proteins. The hepatitis C virus core protein was the most immunogenic protein, and fine analysis with peptides indicated amino acids 23 to 42, 66 to 85, and 131 to 150 as immunodominant regions. In a subgroup of nine patients, proliferation assays were performed before or during IFN. In this subgroup, sustained responders but not those with a transient or no response to IFN showed a specific CD4+ immune reaction to hepatitis C viral antigens (P < .05). Infection with hepatitis C virus genotype 3a was significantly associated with a sustained response to IFN (P < .05). In general, a CD4+ T lymphocyte response was more common in patients with chronic hepatitis C who responded to interferon-alpha as compared with nonresponders.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

T cell recognition of hepatitis B and C viral antigens.

The outcome of hepatitis B and C heavily depends on the appropriate virus specific T cell response. Both CD8+ and CD4+ T lymphocytes do not recognize native viral proteins but processed peptides bound to MHC class I and class II, respectively. For therapeutical intervention aimed at T lymphocytes in chronic carriers as well as for the development of new vaccines, a precise identification of immunodominant epitopes, which can be recognized by a majority of patients, is necessary. Biological features of certain viral antigens have been partly characterized in animal models, but with the availability of modern molecular technology it is possible to extend these findings to the human system. The identification of anchor residues and motifs in peptides, which are essential for binding to certain MHC class I and class II molecules, allows the prediction of MHC allele-specific epitopes within viral proteins. By the use of synthetic peptides and vaccinia expression vectors, several epitopes for cytotoxic and helper T lymphocytes have been identified in HBV and HCV antigens. In HBV infection cytotoxic T lymphocytes recognize epitopes within the polymerase protein, the envelope protein and the nucleocapsid. In HCV cytotoxic epitopes have so far been identified within the nucleocapsid, E1, E2 and NS2. Since virus specific CD8+ T lymphocytes lyse virus infected cells in vitro and seem to play an important role for viral elimination in vivo, activation of virus specific effector cells may be achieved by immunizing chronically infected patients with the MHC-allele-specific peptides. Epitopes for CD4+ T lymphocytes have been demonstrated in the majority of HBV- and HCV-proteins. Different subsets of CD4+ T lymphocytes influence the course of infection by the production of lymphokines which either support antibody production by B cells or cellular antiviral effector mechanisms. In acute and chronic HBV infection the HBcAg/HBeAg-specific T cell response is closely correlated to viral elimination and the occurrence of anti-HBe- and anti-HBs antibodies. In HCV infection the CD4+ T cell response appears to be more heterogenous, and better functional characterization of the CD4+ response to immunodominant peptide epitopes in association with certain disease stages is required. Since T cell activation, the resulting effector functions and binding of the peptide to the HLA-molecule mainly depend on the peptide structure, viral mutations leading to amino acid changes may contribute to T cell non-responsiveness or an inappropriate T cell response.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens, Viral↗
PubMed1993

Long-term response to interferon therapy in chronic hepatitis B: importance of hepatitis B virus heterogeneity.

The long-term therapeutic efficacy of alpha IFN and the influence of preC variants on the type of response were evaluated in 25 patients with chronic hepatitis B, 14 HBeAg and 11 antiHBe positive patients, treated with alpha IFN and monitored for at least four years after discontinuing therapy. In both groups of patients, serum HBV-DNA became frequently undetectable by DNA dot blot during treatment, suggesting that alpha IFN has an antiviral effect both on HBeAg and antiHBe positive chronic carriers. However, long term follow up showed that the loss of viral DNA in antiHBe carriers was only transient, because all responder patients relapsed from 1 to 48 months after IFN withdrawal. In the HBeAg positive carriers, selection for preC mutants was observed at the end of follow up in 2 patients who seroconverted to antiHBe and remained viremic. Both the frequent occurrence of reactivations in antiHBe compared to HBeAg carriers, and the association of IFN therapy with preC mutant virus selection during long term post-treatment follow up observed in this study, indicate that preC variants are more resistant to IFN therapy than preC wild type HBV. Our data suggest therefore, that IFN therapy may be less frequently able to induce a permanent remission in patients infected with preC mutants.

Alanine Transaminase↗
PubMed1993

Increased frequency of CD8+ CD45R0+ memory T lymphocytes in acute hepatitis B virus infection.

CD8+ lymphocytes of the memory subset (= CD45R0+) encompass antigen-specific effector cells, which are believed to be decisive for virus elimination in several viral infections. To determine whether this can be extended to HBV infection naive and memory T cells were studied among CD(4+)- and CD(8+)-lymphocytes and used monoclonal antibodies in two-color flow cytometric analysis to quantitate functional T cell subsets in peripheral blood of patients with acute hepatitis B (n = 11), chronic hepatitis B (n = 24) and healthy individuals (n = 26). Compared to CD4+ populations of healthy individuals the number of total CD4+ lymphocytes in patients with both acute or chronic hepatitis was significantly reduced. In contrast CD8+ cells did not significantly change in either acute and chronic hepatitis. Analysis of naive and memory subsets demonstrated, however, a significant rise in CD45R0+ memory cells from 5 to 15% (70% of all CD8+ cells) in acute hepatitis. These changes within the CD8+ population were, however, restricted to the acute phase of hepatitis in that the frequency of CD8+CD45R0+ decreased within weeks post infection. Furthermore, patients with chronic hepatitis did exhibit normal values of CD8+ memory cells (30% of all CD8+ cells). These findings suggest that enrichment of CD8+CD45R0+ memory cells reflects an accumulation of functional effector cells, which may be specifically activated by viral antigens and determine the outcome of infection.

Acute Disease↗
PubMed1992

Precore mutant hepatitis B virus infection and liver disease.

The type of hepatitis B virus ("wild-type" or precore mutant) in anti-e antigen antibody-positive carriers, viral DNA levels in the serum, and core and e antigen expression in the liver were investigated to search for a possible correlation of these factors with the severity of liver damage. Two major groups of patients were found: the patients in group A were predominantly infected with precore mutant virus and had chronic active hepatitis, expressed nuclear/cytoplasmic core and e antigens in liver biopsy specimens, and usually had high levels of viral DNA in their serum; patients in group B were infected with a mixture of wild-type and mutant viruses, had predominantly chronic persistent hepatitis, showed weaker expression of nuclear core antigen with no cytoplasmic core or e antigen, and had low viremia. A few patients were infected with viruses without precore stop-codon mutation. These data indicate a high prevalence of precore mutant viruses in anti-e carriers with chronic liver disease and suggest that monitoring of virus sequence type and DNA level may be of prognostic value for liver disease sequelae.

Adult↗
PubMed1992

Hepatitis B virus genomes that cannot synthesize pre-S2 proteins occur frequently and as dominant virus populations in chronic carriers in Italy.

The heterogeneity of hepatitis B virus (HBV) pre-S sequences coding for envelope proteins was tested by DNA amplification and direct sequencing of viral genomes from sera of 22 unselected chronic carriers resident in Southern Italy. The sequences of the dominant viral genome populations from 15 carriers were very similar to known published "wildtype" HBV genomes and showed no deletions. In contrast, in the HBV populations of six patients, deletions in the pre-S region, mainly clustered at the amino terminal end of the pre-S2 region, were found. Four of these mutant genome populations and those from another patient cannot express pre-S2 proteins due to deletions or a mutation of the translation initiation codon. Emergence of the pre-S mutant viruses either during the natural course of infection or after interferon treatment was found in follow-up sera of one and two patients, respectively. These data indicate a high prevalence of pre-S mutant viruses which cannot express pre-S2 and normal-size pre-S1 proteins. This has important implications for the usefulness of diagnostic pre-S protein assays and possibly for interferon treatment and the efficacy of new vaccines containing pre-S proteins.

Amino Acid Sequence↗
PubMed1992

T lymphocytes from patients with primary biliary cirrhosis produce reduced amounts of lymphotoxin, tumor necrosis factor and interferon-gamma upon mitogen stimulation.

Primary biliary cirrhosis (PBC) is considered an autoimmune disease characterized by destruction of small intrahepatic bile ducts by lymphocytes. Altered functions of these lymphocytes might reflect an abnormal immune response leading to tissue damage. We investigated lymphokine secretion by mitogen-stimulated T lymphocytes from the liver biopsies of patients with PBC and for comparison also peripheral blood. In PBC, diminished synthesis of lymphotoxin (TNF beta), tumor necrosis factor (TNF alpha) and interferon-gamma (IFN gamma) was found both in T-cell lines from liver tissue and in peripheral blood. The reduction was most prominent for TNF beta in early histological stages of PBC, and appeared to be a stable phenomenon when T cells were tested after long-term tissue culture. Analysis of mRNA levels indicates a possible link between reduced TNF beta production and a defect in interleukin-2 transcription. The data suggest that diminished lymphokine production in patients with PBC may play an important role in the immunopathogenesis of this disease.

Adult↗
PubMed1991

Polymorphic structure of the tumor necrosis factor (TNF) locus: an NcoI polymorphism in the first intron of the human TNF-beta gene correlates with a variant amino acid in position 26 and a reduced level of TNF-beta production.

Since a dysregulated synthesis of tumor necrosis factor alpha (TNF-alpha) may be involved in the pathogenesis of autoimmune diseases, it was of interest to precisely locate the recently reported NcoI restriction fragment length polymorphism (RFLP) of the TNF-alpha region. However, by mapping of 56.8 kb of overlapping cosmid clones and direct sequencing, we could localize the polymorphic NcoI restriction site within the first intron of the TNF-beta gene and not in the TNF-alpha gene. To study whether regulatory mechanisms are affected by this polymorphism, we analyzed the TNF-alpha/TNF-beta production of phytohemagglutinin-stimulated peripheral blood mononuclear cells of individuals homozygous for the TNF-beta NcoI RFLP by ELISA and concomitant Northern blot analysis. On days 2-4 after stimulation with mitogen, the TNFB*1 allele corresponding to a 5.3-kb NcoI fragment presented with a significantly higher TNF-beta response. A mRNA analysis demonstrated that higher protein levels of TNF-beta correlate also with increased amounts of TNF-beta transcripts. No allelic association was found in respect to TNF-alpha production. To further investigate a possible allelic influence on transcription, we determined the DNA sequence of 2 kb of the 5' portion of our cloned TNFB*2 allele and compared it with the available TNF-beta sequences. By computer-aided recognition motif search of DNA binding factors, we report putative binding sites conserved between mouse and man in the 5' flanking region as well as in intron 1 of the TNF-beta gene, found also in other cytokine promoter sequences. In addition, by polymerase chain reaction amplification and sequencing of 740 bp of the 5' part of TNF-beta of individuals typed homozygously for the NcoI RFLP, we could show that amino acid position 26 is conserved as asparagine in the TNFB*1 and as threonine in the TNFB*2 sequence. A previously reported, EcoRI RFLP in the 3' untranslated region of TNF-beta does not segregate with either of the two alleles. Thus, four TNFB alleles can be defined at the DNA level.

Alleles↗
PubMed1991

Prevalence and type of pre-C HBV mutants in anti-HBe positive carriers with chronic liver disease in a highly endemic area.

The sequence variability in the pre-C region of the hepatitis B virus (HBV) genome in the serum of 42 anti-HBe antibody positive carriers with chronic hepatitis B was studied by PCR and direct sequencing to determine prevalence and type of HBV pre-C mutants in a highly endemic area. Except for one, all patients were infected with viruses containing mutations in the pre-C region which prevent precore and e-antigen (HBeAg) expression: 33 were infected predominantly or exclusively with variants containing a stop codon; two had a mixture of wild-type and a pre-C stop codon mutant virus; three had precore variants with mutations of the pre-C initiation codon and two of them an additional stop codon; four had a frameshift mutation; and one had two stop codons. One patient was infected with viruses which contained a mutation creating an amino acid exchange which should not prevent precore and HBeAg expression. These data demonstrate that in an endemic area a higher prevalence and even broader spectrum of pre-C HBV mutants are found than has been recognized previously in anti-HBe positive patients with chronic hepatitis B.

Adult↗