Effector memory CD8 T cell response elicits Hepatitis E Virus genotype 3 pathogenesis in the elderly

Genotype 3 Hepatitis E virus (HEV-3) is an emerging threat for aging population. More than one third of older infected patients develops clinical symptoms with severe liver damage, while others remain asymptomatic. The origin of this discrepancy is still elusive although HEV-3 pathogenesis appears to be immune-mediated. Therefore, we investigated the role of CD8 T cells in the outcome of the infection in immunocompetent elderly subjects. We enrolled twenty two HEV-3-infected patients displaying similar viral determinants and fifteen healthy donors. Among the infected group, sixteen patients experienced clinical symptoms related to liver disease while six remained asymptomatic. Here we report that symptomatic infection is characterized by an expansion of highly activated effector memory CD8 T (EM) cells, regardless of antigen specificity. This robust activation is associated with key features of early T cell exhaustion including a loss in polyfunctional type-1 cytokine production and partial commitment to type-2 cells. In addition, we show that bystander activation of EM cells seems to be dependent on the inflammatory cytokines IL-15 and IL-18, and is supported by an upregulation of the activating receptor NKG2D and an exuberant expression of T-Bet and T-Bet-regulated genes including granzyme B and CXCR3. We also show that the inflammatory chemokines CXCL9-10 are increased in symptomatic patients thereby fostering the recruitment of highly cytotoxic EM cells into the liver in a CXCR3-dependent manner. Finally, we find that the EM-biased immune response returns to homeostasis following viral clearance and disease resolution, further linking the EM cells response to viral burden. Conversely, asymptomatic patients are endowed with low-to-moderate EM cell response. In summary, our findings define immune correlates that contribute to HEV-3 pathogenesis and emphasize the central role of EM cells in governing the outcome of the infection.     

Neural Androgen Receptor Deletion Impairs the Temporal Processing of Objects and Hippocampal CA1-Dependent Mechanisms

We studied the role of testosterone, mediated by the androgen receptor (AR), in modulating temporal order memory for visual objects. For this purpose, we used male mice lacking AR specifically in the nervous system. Control and mutant males were gonadectomized at adulthood and supplemented with equivalent amounts of testosterone in order to normalize their hormonal levels. We found that neural AR deletion selectively impaired the processing of temporal information for visual objects, without affecting classical object recognition or anxiety-like behavior and circulating corticosterone levels, which remained similar to those in control males. Thus, mutant males were unable to discriminate between the most recently seen object and previously seen objects, whereas their control littermates showed more interest in exploring previously seen objects. Because the hippocampal CA1 area has been associated with temporal memory for visual objects, we investigated whether neural AR deletion altered the functionality of this region. Electrophysiological analysis showed that neural AR deletion affected basal glutamate synaptic transmission and decreased the magnitude of N-methyl-D-aspartate receptor (NMDAR) activation and high-frequency stimulation-induced long-term potentiation. The impairment of NMDAR function was not due to changes in protein levels of receptor. These results provide the first evidence for the modulation of temporal processing of information for visual objects by androgens, via AR activation, possibly through regulation of NMDAR signaling in the CA1 area in male mice.     

Mutant loxP vectors for selectable marker recycle and conditional knock-outs

Background  

Gene disruption by targeted integration of transfected constructs becomes increasingly popular for studies of gene function. The chicken B cell line DT40 has been widely used as a model for gene knock-outs due to its high targeted integration activity. Disruption of multiple genes and complementation of the phenotypes is, however, restricted by the number of available selectable marker genes. It is therefore highly desirable to recycle the selectable markers using a site-specific recombination system like Cre/loxP.     

Energy metabolism of beating rat heart cell cultures: II. - Glucose metabolism

Glycogen metabolism, lactate excretion and carbon dioxide production from uniformly labelled glucose were studied on beating rat heart cell cultures in relation to medium replenishment. Only a small fraction of labelled glucose was incorporated into glycogen and then released at a high rate, while exogenous glucose was still continuously taken up by the cells. When glucose in the medium was nearly depleted, glycogen degradation slowed down. The rate of carbon flow through phosphopentose shunt showed a 600 p. cent increase several hours before DNA synthesis. Up to 24 hours after medium renewal, the cells excreted high amounts of lactate; then lactate was reutilized, probably through transaminating processes. Up to 10 hours after medium renewal, labelled carbon dioxide production from exogenous labelled glucose decreased strongly and then increases. Only one of these variations (pentose phosphate shunt) could be attributed to the release of topoinhibition by serum. The other three also occured in the absence of serum and probably resulted from the variation in substrate avaibility induced by medium replenishment.     

THE ACTIVITY OF PARTIAL REACTIONS IN THE CHAIN ELONGATION OF PALMITOYL-CoA AND STEAROYL-CoA BY MOUSE BRAIN MICROSOMES

Partial reactions in the overall chain elongation of palmitoyl-CoA and stearoyl-CoA by mouse brain microsomes have been analyzed. The rate of the initial condensation reaction between palmitoyl-CoA and malonyl-CoA was more than 5 times greater than the rate obtained with stearoyl-CoA, and in both cases good agreement between condensation and overall chain elongation rates was observed. By contrast, both β-hydroxyoctadecanoyl-CoA and β-hydroxyeicosanoyl-CoA were quite rapidly dehydrated by brain microsomes at similar rates. Similar results were obtained with 2-trans-octadecenoyl-CoA and 2-trans-eicosenoyl-CoA in which both substrates were rapidly reduced at nearly the same rate in the presence of NADPH. In all cases, intermediate reactions subsequent to condensation were much more rapid than overall chain elongation. These results suggest that the mechanism of malonyl-CoA-dependent fatty acid chain elongation in brain microsomes is similar to that observed in other tissues, and are consistent with an overall regulation of chain elongation mediated primarily by the initial condensation reaction.     

Electroanalytical Study on Nicotinamide 7-Methylguanine Dinucleotide (Nm7GD+), Analog of Coenzyme NAD+ and Related Compounds

Abstract

Electrochemical methods (direct-current polarography, cyclic voltammetry and differential pulse polarography) were used for analysis of 7-methylguanine nucleosides and nucleotides.     

Increased Synapse Formation Obtained by T Cell Epitopes Containing a CxxC Motif in Flanking Residues Convert CD4+ T Cells into Cytolytic Effectors

The nature of MHC class II-binding epitopes not only determines the specificity of T cell responses, but may also alter effector cell functions. Cytolytic CD4+ T cells have been observed primarily in anti-viral responses, but very little is known about the conditions under which they can be elicited. Their potential as regulators of immune responses, however, deserves investigations. We describe here that inclusion of a thiol-disulfide oxidoreductase motif within flanking residues of class II-restricted epitopes results, both in vitro and in vivo, in elicitation of antigen-specific cytolytic CD4+ T cells through increased synapse formation. We show that both naïve and polarized CD4+ T cells, including Th17 cells, can be converted by cognate recognition of such modified epitopes. Cytolytic CD4+ T cells induce apoptosis on APCs by Fas-FasL interaction. These findings potentially open the way towards a novel form of antigen-specific immunosuppression.