More than 500 million people worldwide are persistently infected with hepatitis B virus or hepatitis C virus. Although both viruses are poorly cytopathic, persistence of either virus carries a risk ...of chronic liver inflammation, potentially resulting in liver steatosis, liver cirrhosis, end-stage liver failure or hepatocellular carcinoma. Virus-specific T cells are a major determinant of the outcome of hepatitis, as they contribute to the early control of chronic hepatitis viruses, but they also mediate immunopathology during persistent virus infection. We have analyzed the role of platelet-derived vasoactive serotonin during virus-induced CD8+ T cell-dependent immunopathological hepatitis in mice infected with the noncytopathic lymphocytic choriomeningitis virus. After virus infection, platelets were recruited to the liver, and their activation correlated with severely reduced sinusoidal microcirculation, delayed virus elimination and increased immunopathological liver cell damage. Lack of platelet-derived serotonin in serotonin-deficient mice normalized hepatic microcirculatory dysfunction, accelerated virus clearance in the liver and reduced CD8+ T cell-dependent liver cell damage. In keeping with these observations, serotonin treatment of infected mice delayed entry of activated CD8+ T cells into the liver, delayed virus control and aggravated immunopathological hepatitis. Thus, vasoactive serotonin supports virus persistence in the liver and aggravates virus-induced immunopathology.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The ecto-5'-nucleotidase (CD73) is expressed by T-cell subsets, myeloid derived suppressive cells and endothelial cells. It works in conjunction with CD39 to regulate the formation and degradation of ...adenosine in vivo. Adenosine has previously been shown to suppress the proliferation and cytokine secretion of T-cells and recent evidence suggests that inhibition of CD73 has the potential to enhance T-cell directed therapies. Here we utilised a CD73 knockout mouse model to assess the suppressive ability of CD73 on CD8+ T-cell classical memory and memory "inflation", induced by murine cytomegalovirus (MCMV) infection and adenovirus immunisation. We show that CD73 is dispensable for normal CD8+ T-cell differentiation and function in both models. Thus CD73 as a suppressor of CD8+ T-cells is unlikely to play a deterministic role in the generation and functional characteristics of antiviral memory in these settings.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The efficacies of many new T cell vaccines rely on generating large populations of long-lived pathogen-specific effector memory CD8 T cells. However, it is now increasingly recognized that prior ...infection history impacts on the host immune response. Additionally, the order in which these infections are acquired could have a major effect. Exploiting the ability to generate large sustained effector memory (i.e. inflationary) T cell populations from murine cytomegalovirus (MCMV) and human Adenovirus-subtype (AdHu5) 5-beta-galactosidase (Ad-lacZ) vector, the impact of new infections on pre-existing memory and the capacity of the host's memory compartment to accommodate multiple inflationary populations from unrelated pathogens was investigated in a murine model. Simultaneous and sequential infections, first with MCMV followed by Ad-lacZ, generated inflationary populations towards both viruses with similar kinetics and magnitude to mono-infected groups. However, in Ad-lacZ immune mice, subsequent acute MCMV infection led to a rapid decline of the pre-existing Ad-LacZ-specific inflating population, associated with bystander activation of Fas-dependent apoptotic pathways. However, responses were maintained long-term and boosting with Ad-lacZ led to rapid re-expansion of the inflating population. These data indicate firstly that multiple specificities of inflating memory cells can be acquired at different times and stably co-exist. Some acute infections may also deplete pre-existing memory populations, thus revealing the importance of the order of infection acquisition. Importantly, immunization with an AdHu5 vector did not alter the size of the pre-existing memory. These phenomena are relevant to the development of adenoviral vectors as novel vaccination strategies for diverse infections and cancers. (241 words).
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Following exposure to vaccines, antigen-specific CD8+ T cell responses develop as long-term memory pools. Vaccine strategies based on adenoviral vectors, e.g., those developed for HCV, are able to ...induce and sustain substantial CD8+ T cell populations. How such populations evolve following vaccination remains to be defined at a transcriptional level. We addressed the transcriptional regulation of divergent CD8+ T cell memory pools induced by an adenovector encoding a model antigen (beta-galactosidase). We observe transcriptional profiles that mimic those following infection with persistent pathogens, murine and human cytomegalovirus (CMV). Key transcriptional hallmarks include upregulation of homing receptors and anti-apoptotic pathways, driven by conserved networks of transcription factors, including T-bet. In humans, an adenovirus vaccine induced similar CMV-like phenotypes and transcription factor regulation. These data clarify the core features of CD8+ T cell memory following vaccination with adenovectors and indicate a conserved pathway for memory development shared with persistent herpesviruses.
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•Adenovector vaccination induces two transcriptionally distinct CD8 memory responses•The sustained response induced by adenovectors and CMV is closely related•The core molecular features are shared tightly in mouse and man•Adenovaccines in humans induce a CD8 response that recapitulates these core features
Bolinger et al. define the transcriptional program associated with sustained CD8+ T cell memory induced by adenoviral vaccination. They relate these to memory “inflation” induced following infection by persistent CMVs. Core features are found to be shared by mouse and man, including a prominent role for TBX21.
Murine CMV (MCMV) infection induces effector CD8+ T cells that continue to increase in frequency after acute infection (“inflation”) and are stably maintained at a high frequency, with up to 20% of ...the CD8+ T‐cell compartment being specific for one epitope, although the flexibility and turnover of these populations is not fully defined. Here we report that effector/memory CD8+ T cells induced by MCMV can be paradoxically boosted following transient depletion of epitope specific CD8+ T cells. Treatment of MCMV‐infected mice with MHC‐Class I‐saporin tetramers led to partial (80–90%) depletion of epitope‐specific CD8+ T cells—rapidly followed by a rebound, leading to expansion and maintenance of up to 40% of total CD8+ T cells, with minimal changes in response to a control epitope (M45). These data indicate the tight balance between host and virus during persistent infection and the functional flexibility of the “inflated” CD8+ T cell responses during persistent infection.
The generation of lymphoid microenvironments in early life depends on the interaction of lymphoid tissue-inducer cells with stromal lymphoid tissue-organizer cells. Whether this cellular interface ...stays operational in adult secondary lymphoid organs has remained elusive. We show here that during acute infection with lymphocytic choriomeningitis virus, antiviral cytotoxic T cells destroyed infected T cell zone stromal cells, which led to profound disruption of secondary lymphoid organ integrity. Furthermore, the ability of the host to respond to secondary antigens was lost. Restoration of the lymphoid microanatomy was dependent on the proliferative accumulation of lymphoid tissue-inducer cells in secondary lymphoid organs during the acute phase of infection and lymphotoxin alpha(1)beta(2) signaling. Thus, crosstalk between lymphoid tissue-inducer cells and stromal cells is reactivated in adults to maintain secondary lymphoid organ integrity and thereby contributes to the preservation of immunocompetence.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The ability of the immune system to discriminate self from non-self is essential for eradicating microbial pathogens but is also responsible for allograft rejection. Whether it is possible to ...selectively suppress alloresponses while maintaining anti-pathogen immunity remains unknown. We found that mice deficient in coronin 1, a regulator of naive T cell homeostasis, fully retained allografts while maintaining T cell-specific responses against microbial pathogens. Mechanistically, coronin 1-deficiency increased cyclic adenosine monophosphate (cAMP) concentrations to suppress allo-specific T cell responses. Costimulation induced on microbe-infected antigen presenting cells was able to overcome cAMP-mediated immunosuppression to maintain anti-pathogen immunity. In vivo pharmacological modulation of this pathway or a prior transfer of coronin 1-deficient T cells actively suppressed allograft rejection. These results define a coronin 1-dependent regulatory axis in T cells important for allograft rejection and suggest that modulation of this pathway may be a promising approach to achieve long-term acceptance of mismatched allografts.
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•Mice lacking coronin 1 show tolerance toward allografts•Costimulation from infected APCs breaks the tolerance to clear pathogens•Coronin 1-deficiency affects CAMKIV-mediated CREB activation in T cells•Prior transfer of coronin 1-deficient T cells promote tolerance toward allografts
Avoiding infection as a consequence of immunosuppression following organ transplantation has been elusive. Here, Jayachandran et al. demonstrate that targeting the immunoregulatory protein coronin 1 in mice results in allograft-specific tolerance in the absence of immunosuppression-associated co-morbidities. Coronin 1-deficiency increased cAMP concentrations to suppress allo-specific T cell responses without compromising pathogen-specific immunity and may represent an attractive therapeutic target.
The establishment of robust T cell memory is critical for the development of novel vaccines for infections and cancers. Classical memory generated by CD8(+)T cells is characterized by contracted ...populations homing to lymphoid organs. T cell memory inflation, as seen for example after CMV infection, is the maintenance of expanded, functional, tissue-associated effector memory cell pools. Such memory pools may also be induced after adenovirus vaccination, and we recently defined common transcriptional and phenotypic features of these populations in mice and humans. However, the rules that govern which epitopes drive memory inflation compared with classical memory are not fully defined, and thus it is not currently possible to direct this process. We used our adenoviral model of memory inflation to first investigate the role of the promoter and then the role of the epitope context in determining memory formation. Specifically, we tested the hypothesis that conventional memory could be converted to inflationary memory by simple presentation of the Ag in the form of minigene vectors. When epitopes from LacZ and murine CMV that normally induce classical memory responses were presented as minigenes, they induced clear memory inflation. These data demonstrate that, regardless of the transgene promoter, the polypeptide context of a CD8(+)T cell epitope may determine whether classical or inflating memory responses are induced. The ability to direct this process by the use of minigenes is relevant to the design of vaccines and understanding of immune responses to pathogens.
Caspase-8, the proximal enzyme in the death-induction pathway of the TNF/nerve growth factor receptor family, is activated upon juxtaposition of its molecules within the receptor complexes and is ...then self-processed. Caspase-8 also contributes to the regulation of cell survival and growth, but little is known about the similarities or the differences between the mechanisms of these nonapoptotic functions and of the enzyme's apoptotic activity. In this study, we report that in bacterial artificial chromosome-transgenic mice, in which the aspartate residue upstream of the initial self-processing site in caspase-8 (D387) was replaced by alanine, induction of cell death by Fas is compromised. However, in contrast to caspase-8-deficient mice, which die in utero at mid-gestation, the mice mutated at D387 were born alive and seemed to develop normally. Moreover, mice with the D387A mutation showed normal in vitro growth responses of T lymphocytes to stimulation of their Ag receptor as well as of B lymphocytes to stimulation by LPS, normal differentiation of bone marrow macrophage precursors in response to M-CSF, and normal generation of myeloid colonies by the bone marrow hematopoietic progenitors, all of which are compromised in cells deficient in caspase-8. These finding indicated that self-processing of activated caspase-8 is differentially involved in the different functions of this enzyme: it is needed for the induction of cell death through the extrinsic cell death pathway but not for nonapoptotic functions of caspase-8.
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