Lack of variant specific CD8+T-cell response against mutant and pre-existing variants leads to outgrowth of particular clones in acute hepatitis C

Background: CTL escape mutations have been described during acute hepatitis C in patients who developed chronic disease later on. Our aim was to investigate the mutual relationship between HCV specific CD8+ T cells and evolution of the viral sequence during early acute HCV infection. Results: We sequenced multiple clones of NS3 1406 epitope in 4 HLA-A{*}02 patients with acute hepatitis C genotype 1b infection. Pentamers specific for the variants were used to monitor the corresponding CD8+ T cell response. We observed outgrowth of mutations, which induced only a weak and thus potentially insufficient CD8+ T cell response. In one patient we observed outgrowth of variant epitopes with similarities to a different genotype rather than de novo mutations most probably due to a lack of responsiveness to these likely pre-existing variants. We could show that in acute hepatitis C CTL escape mutations occur much earlier than demonstrated in previous studies. Conclusions: The adaption of the virus to a new host is characterized by a high and rapid variability in epitopes under CD8+ T cell immune pressure. This adaption takes place during the very early phase of acute infection and strikingly some sequences were reduced below the limit of detection at some time points but were detected at high frequency again at later time points. Independent of the observed variability, HCV-specific CD8+ T cell responses decline and no adaption to different or new antigens during the course of infection could be detected

Association of Hepatitis C Virus—Specific CD8+ T Cells with Viral Clearance in Acute Hepatitis C

CD8+ T lymphocytes play a major role in antiviral immune defense. Their significance for acute hepatitis C is unclear. Our aim was to correlate the CD8+ T cell response with the outcome of infection. Eighteen patients with acute hepatitis C and 19 normal donors were studied. Hepatitis C virus (HCV)—specific CD8+ T cells were identified in the enzyme-linked immunospot assay by their interferon-γ (IFN-γ) production after specific stimulation. The highest numbers of IFN-γ—producing HCV-specific CD8+ T cells were found in patients with acute hepatitis C and a self-limited course of disease during the first 6 months after onset of disease, but these numbers dropped thereafter to undetectable levels. The differences in responsiveness between patients with self-limited disease versus patients with a chronic course were statistically significant (P < .001). Our data show that the number of IFN—γ-producing HCV-specific CD8+ T cells during the first 6 months after onset of disease is associated with eradication of the HCV infectio

Association of Hepatitis C Virus—Specific CD8+ T Cells with Viral Clearance in Acute Hepatitis C

CD8+ T lymphocytes play a major role in antiviral immune defense. Their significance for acute hepatitis C is unclear. Our aim was to correlate the CD8+ T cell response with the outcome of infection. Eighteen patients with acute hepatitis C and 19 normal donors were studied. Hepatitis C virus (HCV)—specific CD8+ T cells were identified in the enzyme-linked immunospot assay by their interferon-γ (IFN-γ) production after specific stimulation. The highest numbers of IFN-γ—producing HCV-specific CD8+ T cells were found in patients with acute hepatitis C and a self-limited course of disease during the first 6 months after onset of disease, but these numbers dropped thereafter to undetectable levels. The differences in responsiveness between patients with self-limited disease versus patients with a chronic course were statistically significant (P < .001). Our data show that the number of IFN—γ-producing HCV-specific CD8+ T cells during the first 6 months after onset of disease is associated with eradication of the HCV infection

Inhibitory Phenotype of HBV-Specific CD4⁺ T-Cells Is Characterized by High PD-1 Expression but Absent Coregulation of Multiple Inhibitory Molecules

Background: T-cell exhaustion seems to play a critical role in CD8(+) T-cell dysfunction during chronic viral infections. However, up to now little is known about the mechanisms underlying CD4(+) T-cell dysfunction during chronic hepatitis B virus (CHB) infection and the role of inhibitory molecules such as programmed death 1 (PD-1) for CD4(+) T-cell failure. Methods: The expression of multiple inhibitory molecules such as PD-1, CTLA-4, TIM-3, CD244, KLRG1 and markers defining the grade of T-cell differentiation as CCR7, CD45RA, CD57 and CD127 were analyzed on virus-specific CD4(+) T-cells from peripheral blood using a newly established DRB1*01-restricted MHC class II Tetramer. Effects of in vitro PD-L1/2 blockade were defined by investigating changes in CD4(+) T-cell proliferation and cytokine production. Results: CD4(+) T-cell responses during chronic HBV infection was characterized by reduced Tetramer(+)CD4(+) T-cell frequencies, effector memory phenotype, sustained PD-1 but low levels of CTLA-4, TIM-3, KLRG1 and CD244 expression. PD-1 blockade revealed individualized patterns of in vitro responsiveness with partly increased IFN-gamma, IL-2 and TNF-alpha secretion as well as enhanced CD4(+) T-cell expansion almost in treated patients with viral control. Conclusion: HBV-specific CD4(+) T-cells are reliably detectable during different courses of HBV infection by MHC class II Tetramer technology. CD4(+) T-cell dysfunction during chronic HBV is basically linked to strong PD-1 upregulation but absent coregulation of multiple inhibitory receptors. PD-L1/2 neutralization partly leads to enhanced CD4(+) T-cell functionality with heterogeneous patterns of CD4(+) T-cell rejunivation

Conserving approximations in direct perturbation theory: new semianalytical impurity solvers and their application to general lattice problems

For the treatment of interacting electrons in crystal lattices approximations based on the picture of effective sites, coupled in a self-consistent fashion, have proven very useful. Particularly in the presence of strong local correlations, a local approach to the problem, combining a powerful method for the short ranged interactions with the lattice propagation part of the dynamics, determines the quality of results to a large extent. For a considerable time the non crossing approximation (NCA) in direct perturbation theory, an approach originally developed by Keiter for the Anderson impurity model, built a standard for the description of the local dynamics of interacting electrons. In the last couple of years exact methods like the numerical renormalization group (NRG) as pioneered by Wilson, have surpassed this approximation as regarding the description of the low energy regime. We present an improved approximation level of direct perturbation theory for finite Coulomb repulsion U, the crossing approximation one (CA1) and discuss its connections with other generalizations of NCA. CA1 incorporates all processes up to fourth order in the hybridization strength V in a self-consistent skeleton expansion, retaining the full energy dependence of the vertex functions. We reconstruct the local approach to the lattice problem from the point of view of cumulant perturbation theory in a very general way and discuss the proper use of impurity solvers for this purpose. Their reliability can be tested in applications to e.g. the Hubbard model and the Anderson-lattice model. We point out shortcomings of existing impurity solvers and improvements gained with CA1 in this context. This paper is dedicated to the memory of Hellmut Keiter.Comment: 45 pages, 22 figure

Oxidation and Reduction Kinetics of Iron and Iron Based Alloys Used as Storage Materials in a High Temperature Battery

The background of the present studies relates to the development of a novel high temperature energy storage system based on a solid oxide cell. The energy is stored in a metal/metal oxide system which is part of the fuel side of the cell. The aim of the present study was to evaluate the suitability of pure iron and iron based model alloys as possible energy storage material for this type of high temperature battery system at a service temperature of 800°C. For this purpose the oxidation and reduction behaviour of iron in Ar–H2–(H2O) environments has been examined. The reduction process in Ar–2%H2 of the wüstite scale formed on pure iron in Ar–H2–H2O was hampered by the formation of a continuous, gas tight metallic iron layer on its surface. Possible approaches to increase oxidation and reduction kinetics by optimised alloy compositions for the Fe storage are discussed

Oxidation and Reduction Kinetics of Iron and Iron Based Alloys Used as Storage Materials in High Temperature Battery

The background of the present studies relates to the development of a novel high temperature energy storage system based on a solid oxide cell. The energy is stored in a metal/metal oxide system which is part of the fuel side of the cell. The aim of the present study was to evaluate the suitability of pure iron and iron based model alloys as possible energy storage material for this type of high temperature battery system at a service temperature of 800°C. For this purpose the oxidation and reduction behaviour of iron in Ar–H2–(H2O) environments has been examined. The reduction process in Ar–2%H2 of the wüstite scale formed on pure iron in Ar–H2–H2O was hampered by the formation of a continuous, gas tight metallic iron layer on its surface. Possible approaches to increase oxidation and reduction kinetics by optimised alloy compositions for the Fe storage are discussed

Effect of PD-L1/2 blockade on CD4⁺ T-cell expansion.

<p>Induction of CD4⁺ T-cell proliferation in chronic HBV (n = 23) from h0 (<i>left</i>) to antigenic stimulation (<i>middle</i>) and PD-L1/2 blockade (<i>right</i>) illustrated as point to point graphs from (<b>A</b>) PD-L1/2 responders (n = 9) and (<b>B</b>) Non-responders (n = 14). Contour plots are shown for each group. (<b>C</b>) Patients treated with nucleosid/nucleotid analogs (<i>black bars</i>) responded to PD-1 blockade using Chi²-test, indicating that viral control let enhance patients susceptibility as (<b>D</b>) treated patients are characterized by low viremia. (<b>E</b>) Decreased PD-1 expression in PD-L1/2 responders (R) (n = 6) versus non-responders (NR) (n = 6). (<b>F</b>) CD4⁺ T-cell frequencies upon antigenic stimulation (<i>black bars</i>) and PD-L1/2 inhibition (<i>grey bars</i>) in relation to PD-1 expression.</p

Baseline Characteristics^*.

<p>*presented as median values.</p><p>**nucleosid/nucleotide analogs.</p><p>***not determined.</p

Inhibitory phenotype of HBV-specific CD4⁺ T-cells.

<p>(<b>A</b>) PD-1 (n = 29), CTLA-4 (n = 8), TIM-3 (n = 14), KLRG1 (n = 12) and CD244 (n = 8) expression is displayed on Tetramer⁺CD4⁺ T-cells during chronic HBV. (<b>B</b>) PD-1 expression in chronic (<i>black points</i>) (n = 29) and acute HBV (<i>black squares</i>) (n = 7), resolved HBV (<i>white squares</i>) (n = 5), EBV (<i>grey points</i>) (n = 15) and Flu (<i>white points</i>) (n = 21) infection. (<b>C</b>) Contour plots illustrate patterns of PD-1 expression during HBV, EBV and Flu infection. (<b>D</b>) CD127 expression on HBV-specific (<i>black points</i>) (n = 11) and Flu-specific CD4⁺ T-cells (<i>white points</i>) (n = 9). (<b>E</b>) Contour plots display CD127 expression on CD14⁻, CD19⁻, Via Probe⁻, Tetramer⁺ T-cells. (<b>F</b>) CD127 defines PD-1 expression as examined in HBV (<i>black bars</i>) and Flu infection (<i>white bar</i>). (<b>G</b>) Influence of viral load on CD127 expression.</p