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Markus Cornberg

Publications and source records attributed to Markus Cornberg.

At least 19 recordsLinked to original sources
PubMed2006

Protection against vaccinia virus challenge by CD8 memory T cells resolved by molecular mimicry.

Live vaccinia virus (VV) vaccination has been highly successful in eradicating smallpox. However, the mechanisms of immunity involved in mediating this protective effect are still poorly understood, and the roles of CD8 T-cell responses in primary and secondary VV infections are not clearly identified. By applying the concept of molecular mimicry to identify potential CD8 T-cell epitopes that stimulate cross-reactive T cells specific to lymphocytic choriomeningitis virus (LCMV) and VV, we identified after screening only 115 peptides two VV-specific immunogenic epitopes that mediated protective immunity against VV. An immunodominant epitope, VV-e7r130, did not generate cross-reactive T-cell responses to LCMV, and a subdominant epitope, VV-a11r198, did generate cross-reactive responses to LCMV. Infection with VV induced strong epitope-specific responses which were stable into long-term memory and peaked at the time virus was cleared, consistent with CD8 T cells assisting in the control of VV. Two different approaches, direct adoptive transfer of VV-e7r-specific CD8 T cells and prior immunization with a VV-e7r-expressing ubiquitinated minigene, demonstrated that memory CD8 T cells alone could play a significant role in protective immunity against VV. These studies suggest that exploiting cross-reactive responses between viruses may be a useful tool to complement existing technology in predicting immunogenic epitopes to large viruses, such as VV, leading to a better understanding of the role CD8 T cells play during these viral infections.

Animals↗
PubMed2006

Hepatitis A virus infection suppresses hepatitis C virus replication and may lead to clearance of HCV.

BACKGROUND/AIMS: The significance of hepatitis A virus (HAV) super-infection in patients with chronic hepatitis C had been a matter of debate. While some studies suggested an incidence of fulminant hepatitis A of up to 35%, this could not be confirmed by others. METHODS: We identified 17 anti-HCV-positive patients with acute hepatitis A from a cohort of 3170 anti-HCV-positive patients recruited at a single center over a period of 12 years. RESULTS: Importantly, none of the anti-HCV-positive patients had a fulminant course of hepatitis A. HCV-RNA was detected by PCR in 84% of the anti-HCV-positive/anti-HAV-IgM-negative patients but only in 65% of anti-HCV-positive patients with acute hepatitis A (p=0.03), indicating suppression of HCV replication during hepatitis A. Previous HAV infection had no effect on HCV replication. After recovery from hepatitis A, an increased HCV replication could be demonstrated for 6 out of 9 patients with serial quantitative HCV-RNA values available while 2 patients remained HCV-RNA negative after clearance of HAV throughout follow-up of at least 2 years. CONCLUSIONS: HAV super-infection is associated with decreased HCV-RNA replication which may lead to recovery from HCV in some individuals. Fulminant hepatitis A is not frequent in patients with chronic hepatitis C recruited at a tertiary referral center.

Acute Disease↗
PubMed2006

Narrowed TCR repertoire and viral escape as a consequence of heterologous immunity.

Why some virus-specific CD8 TCR repertoires are diverse and others restricted or "oligoclonal" has been unknown. We show here that oligoclonality and extreme clonal dominance can be a consequence of T cell cross-reactivity. Lymphocytic choriomeningitis virus (LCMV) and Pichinde virus (PV) encode NP(205-212) epitopes that induce different but highly cross-reactive diverse TCR repertoires. Homologous viral challenge of immune mice only slightly skewed the repertoire and enriched for predictable TCR motifs. However, heterologous viral challenge resulted in a narrow oligoclonal repertoire with dominant clones with unpredictable TCR sequences. This shift in clonal dominance varied with the private, i.e., unique, specificity of the host's TCR repertoire and was simulated using affinity-based computer models. The skewing differences in TCR repertoire following homologous versus heterologous challenge were observed within the same private immune system in mice adoptively reconstituted with memory CD8 T cell pools from the same donor. Conditions driving oligoclonality resulted in an LCMV epitope escape variant in vivo resembling the natural Lassa virus sequence. Thus, T cell oligoclonality, including extremes in clonal dominance, may be a consequence of heterologous immunity and lead to viral escape. This has implications for the design of peptide-based vaccines, which might unintentionally prime for skewed TCR responses to cross-reactive epitopes.

Animals↗
PubMed2006

Early monotherapy with pegylated interferon alpha-2b for acute hepatitis C infection: the HEP-NET acute-HCV-II study.

Early treatment of acute hepatitis C with interferon alpha-2b for 24 weeks prevents chronic infection in almost all patients. Because pegylated interferons have replaced conventional interferon in the therapy of chronic hepatitis C, the aim of this study was to analyze the efficacy of an early treatment of acute hepatitis C with peginterferon alpha-2b. Between February 2001 and February 2004, 89 individuals with acute HCV infection were recruited at 53 different centers in Germany. Patients received 1.5 microg/kg peginterferon alpha-2b for 24 weeks; treatment was initiated after a median of 76 days after infection (range 14-150). End-of-treatment response and sustained virological response were defined as undetectable HCV RNA at the end of therapy and after 24 weeks of follow-up, respectively. In the total study population, virological response was 82% at the end of treatment and 71% at the end of follow-up. Of 89 individuals, 65 (73%) were adherent to therapy, receiving 80% of the interferon dosage within 80% of the scheduled treatment duration. End-of-treatment and sustained virological response rates in this subpopulation were 94% and 89%, respectively. A maximum alanine aminotransferase level of more than 500 U/L prior to therapy was the only factor associated with successful treatment. In conclusion, in acute HCV infection, early treatment with peginterferon alpha-2b leads to high virological response rates in individuals who are adherent to treatment. The high number of dropouts underlines the importance of thorough patient selection and close monitoring during therapy. Thus, future studies should identify factors predicting spontaneous viral clearance to avoid unnecessary therapy.

Acute Disease↗
PubMed2006

Caspase activation is required for antiviral treatment response in chronic hepatitis C virus infection.

Only half of patients with chronic hepatitis C virus (HCV) infection and genotype-1 show a sustained antiviral response to the current antiviral therapy. The reason this treatment fails is unclear, and no reliable marker exists that predicts the treatment outcome. In the present study, we investigated the apoptotic activation of caspases in HCV patients undergoing antiviral therapy with regard to the treatment outcome. We determined caspase activation in sera from patients who were either responding or nonresponding to antiviral therapy by using two novel caspase assays, an immunological and a luminometric enzyme test. We found that compared with nonresponding individuals, responding patients showed significantly (P < .05) increased caspase activity, which was closely correlated with virus elimination (r = 0.81). The cutoff value of serum caspase activity was determined, which correctly predicted the treatment outcome with a sensitivity of 70% and a specificity of 82% (area under the curve 0.845; 95% CI). In conclusion, hepatic caspase activity might play a role in HCV clearance and could also predict the efficacy of antiviral therapy.

Adult↗
PubMed2006

Memory of mice and men: CD8+ T-cell cross-reactivity and heterologous immunity.

The main functions of memory T cells are to provide protection upon re-exposure to a pathogen and to prevent the re-emergence of low-grade persistent pathogens. Memory T cells achieve these functions through their high frequency and elevated activation state, which lead to rapid responses upon antigenic challenge. The significance and characteristics of memory CD8+ T cells in viral infections have been studied extensively. In many of these studies of T-cell memory, experimental viral immunologists go to great lengths to assure that their animal colonies are free of endogenous pathogens in order to design reproducible experiments. These experimental results are then thought to provide the basis for our understanding of human immune responses to viruses. Although these findings can be enlightening, humans are not immunologically naïve, and they often have memory T-cell populations that can cross-react with and respond to a new infectious agent or cross-react with allo-antigens and influence the success of tissue transplantation. These cross-reactive T cells can become activated and modulate the immune response and outcome of subsequent heterologous infections, a phenomenon we have termed heterologous immunity. These large memory populations are also accommodated into a finite immune system, requiring that the host makes room for each new population of memory cell. It appears that memory cells are part of a continually evolving interactive network, where with each new infection there is an alteration in the frequencies, distributions, and activities of memory cells generated in response to previous infections and allo-antigens.

Animals↗
PubMed2006

Present and future therapy for hepatitis C virus.

The treatment of hepatitis C virus (HCV) infection has developed enormously over recent years. Early treatment of acute HCV infection with interferon-alpha can prevent chronicity and a significant proportion of patients with chronic HCV can be cured with the current standard therapy consisting of pegylated interferon-alpha and ribavirin. However, the improvement of current treatment regimens and the development of new antiviral drugs will be essential within the next few years. This review focuses on the present and future concepts for treating HCV infection, including prevention of infection, antiviral therapy of acute and chronic HCV and the management of patients after liver transplantation.

Antiviral Agents↗
PubMed2005

Treatment with daily consensus interferon (CIFN) plus ribavirin in non-responder patients with chronic hepatitis C: a randomized open-label pilot study.

BACKGROUND/AIMS: Therapeutic options for hepatitis C non-responder patients are limited. METHODS: We initiated an open-label pilot study to investigate the efficacy of CIFN plus ribavirin on viral kinetics, sustained virological response (SVR), and histological response in hepatitis C non-responder patients. Seventy-seven patients were enrolled to receive CIFN given daily in combination with 1000/1200 mg ribavirin. An 8-week induction-dosing regimen of 18 microg CIFN, followed by 9 microg for 40 weeks was compared to 9 microg CIFN for 48 weeks. 90% of patients were infected with HCV-genotype 1. RESULTS: Overall, 82% of the patients demonstrated an early virological response, 65% had an end-of-treatment response, and the SVR was 30%. Interferon/ribavirin non-responders demonstrated a SVR of 22%. Induction-dosing resulted in a greater first-phase HCV-RNA decay that, however, did not translate to better SVRs, presumably due to more dose modifications. High ALT, younger age, and second-phase viral kinetics were associated with SVR. Only sustained responders and relapse patients showed an improved liver histology. CONCLUSIONS: Daily dosing of CIFN plus ribavirin may be a promising concept for selected non-responder patients before considering therapies which are anti-viral but not curative. However, motivation and compliance are requisites and a CIFN induction is not required.

Adolescent↗
PubMed2005

Cross-reactive influenza virus-specific CD8+ T cells contribute to lymphoproliferation in Epstein-Barr virus-associated infectious mononucleosis.

The marked proliferation of activated CD8+ T cells is pathognomonic of EBV-associated infectious mononucleosis (IM), common in young adults. Since the diversity and size of the memory CD8+ T cell population increase with age, we questioned whether IM was mediated by the reactivation of memory CD8+ T cells specific to previously encountered pathogens but cross-reactive with EBV. Of 8 HLA-A2+ IM patients, 5 had activated T cells specific to another common virus, as evidenced by a significantly higher number of peripheral blood influenza A virus M1(58-66)-specific T cells compared with healthy immune donors. Two patients with an augmented M1 response had tetramer-defined cross-reactive cells recognizing influenza M1 and EBV-BMLF1(280-288), which accounted for up to one-third of their BMLF1-specific population and likely contributed to a skewed M1-specific T cell receptor repertoire. These epitopes, with only 33% sequence similarity, mediated differential effects on the function of the cross-reactive T cells, which may contribute to alterations in disease outcome. EBV could potentially encode an extensive pool of T cell epitopes that activate other cross-reactive memory T cells. Our results support the concept that cross-reactive memory CD8+ T cells activated by EBV contribute to the characteristic lymphoproliferation of IM.

Adolescent↗
PubMed2005

Private specificities of CD8 T cell responses control patterns of heterologous immunity.

CD8 T cell cross-reactivity between viruses can play roles in protective heterologous immunity and damaging immunopathology. This cross-reactivity is sometimes predictable, such as between lymphocytic choriomeningitis virus (LCMV) and Pichinde virus, where cross-reactive epitopes share six out of eight amino acids. Here, however, we demonstrate more subtle and less predictable cross-reactivity between LCMV and the unrelated vaccinia virus (VV). Epitope-specific T cell receptor usage differed between individual LCMV-infected C57BL/6 mice, even though the mice had similar epitope-specific T cell hierarchies. LCMV-immune mice challenged with VV showed variations, albeit in a distinct hierarchy, in proliferative expansions of and down-regulation of IL-7Ralpha by T cells specific to different LCMV epitopes. T cell responses to a VV-encoded epitope that is cross-reactive with LCMV fluctuated greatly in VV-infected LCMV-immune mice. Adoptive transfers of splenocytes from individual LCMV-immune donors resulted in nearly identical VV-induced responses in each of several recipients, but responses differed depending on the donor. This indicates that the specificities of T cell responses that are not shared between individuals may influence cross-reactivity with other antigens and play roles in heterologous immunity upon encounter with another pathogen. This variability in cross-reactive T cell expansion that is unique to the individual may underlie variation in the pathogenesis of infectious diseases.

Adoptive Transfer↗
PubMed2004

Long-term follow-up after successful interferon therapy of acute hepatitis C.

Early treatment of acute hepatitis C infection with interferon alfa-2b (IFN-alpha-2b) prevents chronicity in almost all patients. So far, no data are available on the long-term outcome after interferon (IFN) therapy of acute hepatitis C. The aim of this study was to assess the clinical, virological, and immunological long-term outcome of 31 successfully treated patients with acute hepatitis C infection who were followed for a median of 135 weeks (52-224 weeks) after end of therapy. None of the individuals had clinical evidence of liver disease. Alanine aminotransferase (ALT) levels were normal in all but 1 patient. Serum hepatitis C virus (HCV) RNA was negative throughout follow-up, even when investigated with the highly sensitive transcription-mediated amplification (TMA) assay (cutoff 5-10 IU/mL). In addition, no HCV RNA was detected in peripheral blood mononuclear cells (PBMC) of 15 cases tested. The patients' overall quality-of-life scores as determined by the SF-36 questionnaire did not differ from the German reference control cohort. Ex vivo interferon gamma (IFN-gamma) ELISPOT analysis detected HCV-specific CD4(+) T-helper cell reactivity in only 35% of cases, whereas HCV-specific CD8(+) T-cell responses were found in 4 of 5 HLA-A2-positive individuals. Anti-HCV antibody levels decreased significantly during and after therapy in all individuals. In conclusion, early treatment of symptomatic acute hepatitis C with IFN-alpha-2b leads to a long-term virological, biochemical, and clinical response. Waning of anti-HCV humoral immunity and presence of HCV-specific CD8(+) (but not CD4(+)) T cells highlights the complexity of T-cell and B-cell memory to HCV, which might be significantly altered by IFN treatment.

Acute Disease↗
PubMed2004

CD8 memory T cells: cross-reactivity and heterologous immunity.

Virus-specific memory T cell populations demonstrate plasticity in antigen recognition and in their ability to accommodate new memory T cell populations. The degeneracy of T cell antigen recognition and the flexibility of diverse antigen-specific repertoires allow the host to respond to a multitude of pathogens while accommodating these numerous large memory pools in a finite immune system. These cross-reactive memory T cells can be employed in immune responses and mediate protective immunity, but they can also induce life-threatening immunopathology or impede transplantation tolerance and graft survival. Here we discuss examples of altered viral pathogenesis occurring as a consequence of heterologous T cell immunity and propose models for the maintenance of a dynamic pool of memory cells.

Animals↗
PubMed2004

Effect of H. pylori on the expression of TRAIL, FasL and their receptor subtypes in human gastric epithelial cells and their role in apoptosis.

BACKGROUND AND AIMS: In the human stomach expression of TNF-related apoptosis inducing ligand (TRAIL) and its receptors and the modulatory role of Helicobacter pylori are not well described. Therefore, we investigated the effect of H. pylori on the expression of TRAIL, FasL and their receptors (TRAIL-R1-R4, Fas) in gastric epithelial cells and examined their role in apoptosis. MATERIALS AND METHODS: mRNA and protein expression of TRAIL, FasL and their receptors were analyzed in human gastric epithelial cells using RT-PCR, Western blot, and immunohistochemistry. Gastric epithelial cells were incubated with FasL, TRAIL and/or H. pylori, and effects on expression, cell viability and epithelial apoptosis were monitored. Apoptosis was analyzed by histone ELISA, DAPI staining and immunohistochemistry. RESULTS: TRAIL, FasL and their receptor subtypes were expressed in human gastric mucosa, gastric epithelial cell primary cultures and gastric cancer cells. TRAIL, FasL and H. pylori caused a time- and concentration-dependent induction of DNA fragmentation in gastric cancer cells with synergistic effects. In addition, H. pylori caused a selective up-regulation of TRAIL, TRAIL-R1 and Fas mRNA and protein expression in gastric cancer cells. CONCLUSIONS: Next to FasL and Fas, TRAIL and all of its receptor subtypes are expressed in the human stomach and differentially modulated by H. pylori. TRAIL, FasL and H. pylori show complex interaction mediating apoptosis in human gastric epithelial cells. These findings might be important for the understanding of gastric epithelial cell kinetics in patients with H. pylori infection.

Apoptosis↗
PubMed2002

Treatment of chronic hepatitis C with PEGylated interferon and ribavirin.

Treatment with interferon alfa combined with ribavirin is successful in approximately 40% to 45% of patients with chronic hepatitis C viral infection (HCV). However, response rates are disappointing in patients who are difficult to treat, such as those infected with HCV genotype 1, high viral load, or advanced liver fibrosis. In addition, low tolerability and significant side effects of therapy frequently lead to dose reduction and treatment discontinuation, decreasing response rates further. Thus, investigation of new treatment options and innovations for chronic HCV infection are vital. This review describes recent advances in the treatment of HCV infection with PEGylated interferon (interferon modified with polyethylene glycol [PEG] ) combined with ribavirin.

Antiviral Agents↗