TOX defines the degree of CD8+ T cell dysfunction in distinct phases of chronic HBV infection

Objective Chronic hepatitis B virus (HBV) infection is characterised by HBV-specific CD8+ T cell dysfunction that has been linked to Tcell exhaustion, a distinct differentiation programme associated with persisting antigen recognition. Recently, Thymocyte Selection-Associated High Mobility Group Box (TOX) was identified as master regulator of CD8+ T cell exhaustion. Here, we addressed the role of TOX in HBV-specific CD8+ T cell dysfunction associated with different clinical phases of infection. Design We investigated TOX expression in HBV-specific CD8+ T cells from 53 HLA-A*01:01, HLA-A*11:01 and HLA-A*02:01 positive patients from different HBV infection phases and compared it to hepatitis C virus (HCV)-specific, cytomegalovirus (CMV)-specific, Epstein-Barr virus (EBV)-specific and influenza virus (FLU)-specific CD8+ T cells. Phenotypic and functional analyses of virus-specific CD8+ T cells were performed after peptide-loaded tetramer-enrichment and peptide-specific expansion. Results Our results show that TOX expression in HBV-specific CD8+ T cells is linked to chronic antigen stimulation, correlates with viral load and is associated with phenotypic and functional characteristics of T-cell exhaustion. In contrast, similar TOX expression in EBV-specific and CMV-specific CD8+ T cells is not linked to T-cell dysfunction suggesting different underlying programmes. TOX expression in HBV-specific CD8+ T cells is also affected by targeted antigens, for example, core versus polymerase. In HBV-specific CD8+ T cells, TOX expression is maintained after spontaneous or therapy-mediated viral control in chronic but not self-limiting acute HBV infection indicating a permanent molecular imprint after chronic but not temporary stimulation. Conclusion Our data highlight TOX as biomarker specific for dysfunctional virus-specific CD8+ T cells in the context of an actively persisting infection

Characterization of the Modular Design of the Autolysin/Adhesin Aaa from Staphylococcus Aureus

BACKGROUND: Staphylococcus aureus is a frequent cause of serious and life-threatening infections, such as endocarditis, osteomyelitis, pneumonia, and sepsis. Its adherence to various host structures is crucial for the establishment of diseases. Adherence may be mediated by a variety of adhesins, among them the autolysin/adhesins Atl and Aaa. Aaa is composed of three N-terminal repeated sequences homologous to a lysin motif (LysM) that can confer cell wall attachment and a C-terminally located cysteine, histidine-dependent amidohydrolase/peptidase (CHAP) domain having bacteriolytic activity in many proteins. METHODOLOGY/PRINCIPAL FINDINGS: Here, we show by surface plasmon resonance that the LysM domain binds to fibrinogen, fibronectin, and vitronectin respresenting a novel adhesive function for this domain. Moreover, we demonstrated that the CHAP domain not only mediates the bacteriolytic activity, but also adherence to fibrinogen, fibronectin, and vitronectin, thus demonstrating for the first time an adhesive function for this domain. Adherence of an S. aureus aaa mutant and the complemented aaa mutant is slightly decreased and increased, respectively, to vitronectin, but not to fibrinogen and fibronectin, which might at least in part result from an increased expression of atl in the aaa mutant. Furthermore, an S. aureus atl mutant that showed enhanced adherence to fibrinogen, fibronectin, and endothelial cells also demonstrated increased aaa expression and production of Aaa. Thus, the redundant functions of Aaa and Atl might at least in part be interchangeable. Lastly, RT-PCR and zymographic analysis revealed that aaa is negatively regulated by the global virulence gene regulators agr and SarA. CONCLUSIONS/SIGNIFICANCE: We identified novel functions for two widely distributed protein domains, LysM and CHAP, i.e. the adherence to the extracellular matrix proteins fibrinogen, fibronectin, and vitronectin. The adhesive properties of Aaa might promote S. aureus colonization of host extracellular matrix and tissue, suggesting a role for Aaa in the pathogenesis of S. aureus infections

Salmonella Pathogenicity Island 4-Mediated Adhesion Is Coregulated with Invasion Genes in Salmonella enterica▿

Salmonella pathogenicity island 4 (SPI4) encodes a type I secretion system and the cognate substrate protein, SiiE. We have recently demonstrated that SiiE is a giant nonfimbrial adhesin involved in the adhesion of Salmonella enterica serovar Typhimurium to polarized epithelial cells. We also observed that under in vitro culture conditions, the synthesis and secretion of SiiE coincided with the activation of Salmonella invasion genes. These observations prompted us to investigate the regulation of SPI4 genes in detail. A novel approach for the generation of reporter gene fusions was employed to generate single-copy chromosomal fusions to various genes within SPI4, and the expression of these fusions was investigated. We analyzed the regulation of SPI4 genes and the roles of various regulatory systems for SPI4 expression. Our data show that the expression of SPI4 genes is coregulated with SPI1 invasion genes by the global regulator SirA. Expression of a SPI4 gene was also reduced in the absence of HilA, the central local regulator of SPI1 gene expression. Both SirA and HilA functions were required for the secretion of SiiE and the SPI4-mediated adhesion. Our data demonstrate that SPI4-mediated adhesion, as well as SPI1-mediated invasion, are tightly coregulated by the same regulatory circuits and induced under similar environmental conditions

CD8⁺ T Cell Responses during HCV Infection and HCC

Chronic hepatitis C virus (cHCV) infection is a major global health burden and the leading cause of hepatocellular carcinoma (HCC) in the Western world. The course and outcome of HCV infection is centrally influenced by CD8+ T cell responses. Indeed, strong virus-specific CD8+ T cell responses are associated with spontaneous viral clearance while failure of these responses, e.g., caused by viral escape and T cell exhaustion, is associated with the development of chronic infection. Recently, heterogeneity within the exhausted HCV-specific CD8+ T cells has been observed with implications for immunotherapeutic approaches also for other diseases. In HCC, the presence of tumor-infiltrating and peripheral CD8+ T cell responses correlates with a favorable prognosis. Thus, tumor-associated and tumor-specific CD8+ T cells are considered suitable targets for immunotherapeutic strategies. Here, we review the current knowledge of CD8+ T cell responses in chronic HCV infection and HCC and their respective failure with the potential consequences for T cell-associated immunotherapeutic approaches

doi:10.1016/j.ijmm.2006.05.001

Regulation of Abstract The function of a type III secretion system (T3SS) encoded by Salmonella pathogenicity island 2 (SPI2) is essential for the intracellular lifestyle of Salmonella enterica serovar Typhimurium. Expression of SPI2 genes is induced within the Salmonella-containing vacuole (SCV) inside host cells and is controlled by the SsrAB two-component system. However, the nature of the signals leading to expression of SPI2 genes is controversial. Here we report that expression of SPI2 genes can be induced independently by two different environmental stimuli. Exposure of bacteria to slightly acidic pH was sufficient to induce a rapid up-regulation of SPI2 genes. In contrast, limitation of inorganic phosphate (P i ) in the growth media led to activation of SPI2 genes in the late exponential growth phase and was independent of the media pH. Limitation of P i induced an over-expression of sensor protein SsrB. Response to both environmental stimuli required a functional SsrAB system. In vivo analyses indicated that limitation of P i is also encountered by intracellular Salmonella. Our observations allow the integration of previous disparate reports on the induction of SPI2 genes.

Influence of drying methods on the physical properties of bacterial nanocellulose

Bacterial nanocellulose (BNC) is a promising material for the use in medical implants. BNC does not induce unwanted reactions in vivo , is long term stable and possesses unique mechanical properties. However, to make the most of these features, BNC must be carefully processed. Details of the cultivation and post-synthetic methods offer various ways to control the properties of BNC. The focus of this work is put on drying of the BNC. Different unconstrained drying methods (climate chamber at 23°C, oven at 100°C, freeze-drying) and constrained drying under excertion of uniaxial pressure at various temperatures have been investigated. The reduction of the high water content of native BNC (≈98%) causes a thickness reduction of the samples. For oven or climate chamber drying a thickness reduction of 98% is observed, while freeze-drying widely preserves the nano- or micro-structure of the fibrous material and leads to a thickness reduction of only ≈13%. During drying or pressing at high temperature (100°C), i.e. by evaporation of the water, intermolecular hydrogen bonds are formed and interconnect the individual fibres and strands. Consequently mechanical stiffening is observed in tensile tests at small strains. After drying, a densified cellulose nano-fibre network is observed by scanning electron microscopy. Due to the irreversibility of drying by evaporation, the water content and water retention capacity of BNC are not recovered by rehydration. Applying uniaxial pressure before drying further enhances the irreversible reinforcement of the fibre network, while this is not the case when pressing the samples after drying. The presented results show that the properties of BNC can be widely controlled by post-processing steps. Thus, taylor-made BNC can be produced for biomedical applications