Humoral and cellular immune responses in fully vaccinated individuals with or without SARS-CoV-2 breakthrough infection: Results from the CoV-ADAPT cohort

Despite recent advances in prophylactic vaccination, SARS-CoV-2 infections continue to cause significant morbidity. A better understanding of immune response differences between vaccinated individuals with and without later SARS-CoV-2 breakthrough infection is urgently needed. CoV-ADAPT is a prospective long-term study comparing humoral (anti-spike-RBD-IgG, neutralization capacity, avidity) and cellular (spike-induced T-cell interferon-γ [IFN-γ] release) immune responses in individuals vaccinated against SARS-CoV-2 at four different time points (three before and one after third vaccination). In this cohort study, 62 fully vaccinated individuals presented with SARS-CoV-2 breakthrough infections vs 151 without infection 3-7 months following third vaccination. Breakthrough infections significantly increased anti-spike-RBD-IgG (p < 0.01), but not spike-directed T-cell IFN-γ release (TC) or antibody avidity. Despite comparable surrogate neutralization indices, the functional neutralization capacity against SARS-CoV-2-assessed via a tissue culture-based assay-was significantly higher following breakthrough vs no breakthrough infection. Anti-spike-RBD-IgG and antibody avidity decreased with age (p < 0.01) and females showed higher anti-spike-RBD-IgG (p < 0.01), and a tendency towards higher antibody avidity (p = 0.051). The association between humoral and cellular immune responses previously reported at various time points was lost in subjects after breakthrough infections (p = 0.807). Finally, a machine-learning approach based on our large immunological dataset (a total of 49 variables) from different time points was unable to predict breakthrough infections (area under the curve: 0.55). In conclusion, distinct differences in humoral vs cellular immune responses in fully vaccinated individuals with or without breakthrough infection could be demonstrated. Breakthrough infections predominantly drive the humoral response without boosting the cellular component. Breakthrough infections could not be predicted based on immunological data, which indicates a superior role of environmental factors (e.g., virus exposure) in individualized risk assessment.

Astrocytes evoke a robust IRF7-independent type I interferon response upon neurotropic viral infection

BACKGROUND

Type I interferons (IFN-I) are fundamental in controlling viral infections but fatal interferonopathy is restricted in the immune-privileged central nervous system (CNS). In contrast to the well-established role of Interferon Regulatory Factor 7 (IRF7) in the regulation of IFN-I response in the periphery, little is known about the specific function in the CNS.

METHODS

To investigate the role for IRF7 in antiviral response during neurotropic virus infection, mice deficient for IRF3 and IRF7 were infected systemically with Langat virus (LGTV). Viral burden and IFN-I response was analyzed in the periphery and the CNS by focus formation assay, RT-PCR, immunohistochemistry and in vivo imaging. Microglia and infiltration of CNS-infiltration of immune cells were characterized by flow cytometry.

RESULTS

Here, we demonstrate that during infection with the neurotropic Langat virus (LGTV), an attenuated member of the tick-borne encephalitis virus (TBEV) subgroup, neurons do not rely on IRF7 for cell-intrinsic antiviral resistance and IFN-I induction. An increased viral replication in IRF7-deficient mice suggests an indirect antiviral mechanism. Astrocytes rely on IRF7 to establish a cell-autonomous antiviral response. Notably, the loss of IRF7 particularly in astrocytes resulted in a high IFN-I production. Sustained production of IFN-I in astrocytes is independent of an IRF7-mediated positive feedback loop.

CONCLUSION

IFN-I induction in the CNS is profoundly regulated in a cell type-specific fashion.

Translatome analyses by bio-orthogonal non-canonical amino acid labeling reveal that MR1-activated MAIT cells induce an M1 phenotype and antiviral programming in antigen-presenting monocytes

MAIT cells are multifunctional innate-like effector cells recognizing bacterial-derived vitamin B metabolites presented by the non-polymorphic MHC class I related protein 1 (MR1). However, our understanding of MR1-mediated responses of MAIT cells upon their interaction with other immune cells is still incomplete. Here, we performed the first translatome study of primary human MAIT cells interacting with THP-1 monocytes in a bicellular system. We analyzed the interaction between MAIT and THP-1 cells in the presence of the activating 5-OP-RU or the inhibitory Ac-6-FP MR1-ligand. Using bio-orthogonal non-canonical amino acid tagging (BONCAT) we were able to enrich selectively those proteins that were newly translated during MR1-dependent cellular interaction. Subsequently, newly translated proteins were measured cell-type-specifically by ultrasensitive proteomics to decipher the coinciding immune responses in both cell types. This strategy identified over 2,000 MAIT and 3,000 THP-1 active protein translations following MR1 ligand stimulations. Translation in both cell types was found to be increased by 5-OP-RU, which correlated with their conjugation frequency and CD3 polarization at MAIT cell immunological synapses in the presence of 5-OP-RU. In contrast, Ac-6-FP only regulated a few protein translations, including GSK3B, indicating an anergic phenotype. In addition to known effector responses, 5-OP-RU-induced protein translations uncovered type I and type II Interferon-driven protein expression profiles in both MAIT and THP-1 cells. Interestingly, the translatome of THP-1 cells suggested that activated MAIT cells can impact M1/M2 polarization in these cells. Indeed, gene and surface expression of CXCL10, IL-1β, CD80, and CD206 confirmed an M1-like phenotype of macrophages being induced in the presence of 5-OP-RU-activated MAIT cells. Furthermore, we validated that the Interferon-driven translatome was accompanied by the induction of an antiviral phenotype in THP-1 cells, which were found able to suppress viral replication following conjugation with MR1-activated MAIT cells. In conclusion, BONCAT translatomics extended our knowledge of MAIT cell immune responses at the protein level and discovered that MR1-activated MAIT cells are sufficient to induce M1 polarization and an anti-viral program of macrophages.

Immune response and pathogen invasion at the choroid plexus in the onset of cerebral toxoplasmosis

BACKGROUND

Toxoplasma gondii (T. gondii) is a highly successful parasite being able to cross all biological barriers of the body, finally reaching the central nervous system (CNS). Previous studies have highlighted the critical involvement of the blood-brain barrier (BBB) during T. gondii invasion and development of subsequent neuroinflammation. Still, the potential contribution of the choroid plexus (CP), the main structure forming the blood-cerebrospinal fluid (CSF) barrier (BCSFB) have not been addressed.

METHODS

To investigate T. gondii invasion at the onset of neuroinflammation, the CP and brain microvessels (BMV) were isolated and analyzed for parasite burden. Additionally, immuno-stained brain sections and three-dimensional whole mount preparations were evaluated for parasite localization and morphological alterations. Activation of choroidal and brain endothelial cells were characterized by flow cytometry. To evaluate the impact of early immune responses on CP and BMV, expression levels of inflammatory mediators, tight junctions (TJ) and matrix metalloproteinases (MMPs) were quantified. Additionally, FITC-dextran was applied to determine infection-related changes in BCSFB permeability. Finally, the response of primary CP epithelial cells to T. gondii parasites was tested in vitro.

RESULTS

Here we revealed that endothelial cells in the CP are initially infected by T. gondii, and become activated prior to BBB endothelial cells indicated by MHCII upregulation. Additionally, CP elicited early local immune response with upregulation of IFN-γ, TNF, IL-6, host-defence factors as well as swift expression of CXCL9 chemokine, when compared to the BMV. Consequently, we uncovered distinct TJ disturbances of claudins, associated with upregulation of MMP-8 and MMP-13 expression in infected CP in vivo, which was confirmed by in vitro infection of primary CP epithelial cells. Notably, we detected early barrier damage and functional loss by increased BCSFB permeability to FITC-dextran in vivo, which was extended over the infection course.

CONCLUSIONS

Altogether, our data reveal a close interaction between T. gondii infection at the CP and the impairment of the BCSFB function indicating that infection-related neuroinflammation is initiated in the CP.

Physiologically Based Pharmacokinetic/Pharmacodynamic Model for the Treatment of Dengue Infections Applied to the Broad Spectrum Antiviral Soraphen A

While a drug treatment is unavailable, the global incidence of Dengue virus (DENV) infections and its associated severe manifestations continues to rise. We report the construction of the first physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model that predicts viremia levels in relevant target organs based on preclinical data with the broad spectrum antiviral soraphen A (SorA), an inhibitor of the host cell target acetyl-CoA-carboxylase. SorA was highly effective against DENV in vitro (EC₅₀ = 4.7 nM) and showed in vivo efficacy by inducing a significant reduction of viral load in the spleen and liver of IFNAR^-/- mice infected with DENV-2. PBPK/PD predictions for SorA matched well with the experimental infection data. Transfer to a human PBPK/PD model for DENV to mimic a clinical scenario predicted a reduction in viremia by more than one log₁₀ unit for an intravenous infusion regimen of SorA. The PBPK/PD model is applicable to any DENV drug lead and, thus, represents a valuable tool to accelerate and facilitate DENV drug discovery and development.

COVID-19: Seroprevalence and Vaccine Responses in UK Dental Care Professionals

Dental care professionals (DCPs) are thought to be at enhanced risk of occupational exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, robust data to support this from large-scale seroepidemiological studies are lacking. We report a longitudinal seroprevalence analysis of antibodies to SARS-CoV-2 spike glycoprotein, with baseline sampling prior to large-scale practice reopening in July 2020 and follow-up postimplementation of new public health guidance on infection prevention control (IPC) and enhanced personal protective equipment (PPE). In total, 1,507 West Midlands DCPs were recruited into this study in June 2020. Baseline seroprevalence was determined using a combined IgGAM enzyme-linked immunosorbent assay and the cohort followed longitudinally for 6 mo until January/February 2021 through the second wave of the coronavirus disease 2019 pandemic in the United Kingdom and vaccination commencement. Baseline seroprevalence was 16.3%, compared to estimates in the regional population of 6% to 7%. Seropositivity was retained in over 70% of participants at 3- and 6-mo follow-up and conferred a 75% reduced risk of infection. Nonwhite ethnicity and living in areas of greater deprivation were associated with increased baseline seroprevalence. During follow-up, no polymerase chain reaction-proven infections occurred in individuals with a baseline anti-SARS-CoV-2 IgG level greater than 147.6 IU/ml with respect to the World Health Organization international standard 20-136. After vaccination, antibody responses were more rapid and of higher magnitude in those individuals who were seropositive at baseline. Natural infection with SARS-CoV-2 prior to enhanced PPE was significantly higher in DCPs than the regional population. Natural infection leads to a serological response that remains detectable in over 70% of individuals 6 mo after initial sampling and 9 mo from the peak of the first wave of the pandemic. This response is associated with protection from future infection. Even if serological responses wane, a single dose of the Pfizer-BioNTech 162b vaccine is associated with an antibody response indicative of immunological memory.

OTUB1 prevents lethal hepatocyte necroptosis through stabilization of c-IAP1 during murine liver inflammation

In bacterial and sterile inflammation of the liver, hepatocyte apoptosis is, in contrast to necroptosis, a common feature. The molecular mechanisms preventing hepatocyte necroptosis and the potential consequences of hepatocyte necroptosis are largely unknown. Apoptosis and necroptosis are critically regulated by the ubiquitination of signaling molecules but especially the regulatory function of deubiquitinating enzymes (DUBs) is imperfectly defined. Here, we addressed the role of the DUB OTU domain aldehyde binding-1 (OTUB1) in hepatocyte cell death upon both infection with the hepatocyte-infecting bacterium Listeria monocytogenes (Lm) and D-Galactosamine (DGal)/Tumor necrosis factor (TNF)-induced sterile inflammation. Combined in vivo and in vitro experiments comprising mice lacking OTUB1 specifically in liver parenchymal cells (OTUB1LPC-KO) and human OTUB1-deficient HepG2 cells revealed that OTUB1 prevented hepatocyte necroptosis but not apoptosis upon infection with Lm and DGal/TNF challenge. Lm-induced necroptosis in OTUB1LPC-KO mice resulted in increased alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) release and rapid lethality. Treatment with the receptor-interacting serine/threonine-protein kinase (RIPK) 1 inhibitor necrostatin-1s and deletion of the pseudokinase mixed lineage kinase domain-like protein (MLKL) prevented liver damage and death of infected OTUB1LPC-KO mice. Mechanistically, OTUB1 reduced K48-linked polyubiquitination of the cellular inhibitor of apoptosis 1 (c-IAP1), thereby diminishing its degradation. In the absence of OTUB1, c-IAP1 degradation resulted in reduced K63-linked polyubiquitination and increased phosphorylation of RIPK1, RIPK1/RIPK3 necrosome formation, MLKL-phosphorylation and hepatocyte death. Additionally, OTUB1-deficiency induced RIPK1-dependent extracellular-signal-regulated kinase (ERK) activation and TNF production in Lm-infected hepatocytes. Collectively, these findings identify OTUB1 as a novel regulator of hepatocyte-intrinsic necroptosis and a critical factor for survival of bacterial hepatitis and TNF challenge.

SARS-CoV-2 neutralizing human recombinant antibodies selected from pre-pandemic healthy donors binding at RBD-ACE2 interface

COVID-19 is a severe acute respiratory disease caused by SARS-CoV-2, a new recently emerged sarbecovirus. This virus uses the human ACE2 enzyme as receptor for cell entry, recognizing it with the receptor binding domain (RBD) of the S1 subunit of the viral spike protein. We present the use of phage display to select anti-SARS-CoV-2 spike antibodies from the human naïve antibody gene libraries HAL9/10 and subsequent identification of 309 unique fully human antibodies against S1. 17 antibodies are binding to the RBD, showing inhibition of spike binding to cells expressing ACE2 as scFv-Fc and neutralize active SARS-CoV-2 virus infection of VeroE6 cells. The antibody STE73-2E9 is showing neutralization of active SARS-CoV-2 as IgG and is binding to the ACE2-RBD interface. Thus, universal libraries from healthy human donors offer the advantage that antibodies can be generated quickly and independent from the availability of material from recovering patients in a pandemic situation.

IRF-1 is critical for IFNγ mediated immune surveillance

We recently described that IRF-1 is important for IFNγ mediated immune surveillance in metastasis. Despite the upregulation of MHC Class I in tumor cells, IRF-1 leads to a NK cell-dependent elimination of tumor cells. This mechanism is independent on inhibitory receptors and cytotoxic granules but dependent on DNAM-1.

The envelope protein of tick-borne encephalitis virus influences neuron entry, pathogenicity, and vaccine protection

Background

Tick-borne encephalitis virus (TBEV) is considered to be the medically most important arthropod-borne virus in Europe. The symptoms of an infection range from subclinical to mild flu-like disease to lethal encephalitis. The exact determinants of disease severity are not known; however, the virulence of the strain as well as the immune status of the host are thought to be important factors for the outcome of the infection. Here we investigated virulence determinants in TBEV infection.

Method

Mice were infected with different TBEV strains, and high virulent and low virulent TBEV strains were chosen. Sequence alignment identified differences that were cloned to generate chimera virus. The infection rate of the parental and chimeric virus were evaluated in primary mouse neurons, astrocytes, mouse embryonic fibroblasts, and in vivo. Neutralizing capacity of serum from individuals vaccinated with the FSME-IMMUN® and Encepur® or combined were evaluated.

Results

We identified a highly pathogenic and neurovirulent TBEV strain, 93/783. Using sequence analysis, we identified the envelope (E) protein of 93/783 as a potential virulence determinant and cloned it into the less pathogenic TBEV strain Torö. We found that the chimeric virus specifically infected primary neurons more efficiently compared to wild-type (WT) Torö and this correlated with enhanced pathogenicity and higher levels of viral RNA in vivo. The E protein is also the major target of neutralizing antibodies; thus, genetic variation in the E protein could influence the efficiency of the two available vaccines, FSME-IMMUN® and Encepur®. As TBEV vaccine breakthroughs have occurred in Europe, we chose to compare neutralizing capacity from individuals vaccinated with the two different vaccines or a combination of them. Our data suggest that the different vaccines do not perform equally well against the two Swedish strains.

Conclusions

Our findings show that two amino acid substitutions of the E protein found in 93/783, A83T, and A463S enhanced Torö infection of neurons as well as pathogenesis and viral replication in vivo; furthermore, we found that genetic divergence from the vaccine strain resulted in lower neutralizing antibody titers in vaccinated individuals.

Langat virus infection affects hippocampal neuron morphology and function in mice without disease signs

Background

Tick-borne encephalitis virus (TBEV) is an important human pathogen that can cause the serious illness tick-borne encephalitis (TBE). Patients with clinical symptoms can suffer from severe meningoencephalitis with sequelae that include cognitive disorders and paralysis. While less than 30% of patients with clinical symptoms develop meningoencephalitis, the number of seropositive individuals in some regions indicates a much higher prevalence of TBEV infections, either with no or subclinical symptoms. The functional relevance of these subclinical TBEV infections and their influence on brain functions, such as learning and memory, has not been investigated so far.

Methods

To compare the effect of low and high viral replication in the brain, wildtype and Irf-7^−/− mice were infected with Langat virus (LGTV), which belongs to the TBEV-serogroup. The viral burden was analyzed in the olfactory bulb and the hippocampus. Open field, elevated plus maze, and Morris water maze experiments were performed to determine the impact on anxiety-like behavior, learning, and memory formation. Spine density of hippocampal neurons and activation of microglia and astrocytes were analyzed.

Results

In contrast to susceptible Irf-7^−/− mice, wildtype mice showed no disease signs upon LGTV infection. Detection of viral RNA in the olfactory bulb revealed CNS infections in wildtype and Irf-7^−/− mice. Very low levels of viral replication were detectable in the hippocampus of wildtype mice. Although wildtype mice develop no disease signs, they showed reduced anxiety-like behavior and impaired memory formation, whereas Irf-7^−/− mice were not affected. This impairment was associated with a significant decrease in spine density of neurons in the hippocampal CA1 region of wildtype mice. Microglia activation and astrogliosis were detected in the hippocampus.

Conclusion

In this study, we demonstrate that subclinical infections by viruses from the TBEV-serogroup affected anxiety-like behavior. Virus replication in the olfactory bulb induced far-reaching effects on hippocampal neuron morphology and impaired hippocampus-dependent learning and memory formation.

Correlation of Severity of Human Tick-Borne Encephalitis Virus Disease and Pathogenicity in Mice

We compared 2 tick-borne encephalitis virus strains isolated from 2 different foci that cause different symptoms in tick-borne encephalitis patients, from neurologic to mild gastrointestinal symptoms. We compared neuroinvasiveness, neurovirulence, and proinflammatory cytokine response in mice and found unique differences that contribute to our understanding of pathogenesis.

Blocking IL-10 receptor signaling ameliorates Mycobacterium tuberculosis infection during influenza-induced exacerbation

Epidemiological findings indicate that coinfection with influenza viruses is associated with an increased risk of death in patients suffering from tuberculosis, but the underlying pathomechanisms are not well understood. In this study, we demonstrate that influenza A virus (IAV) coinfection rapidly impairs control of Mycobacterium tuberculosis (Mtb) in C57BL/6 mice. IAV coinfection was associated with significantly increased bacterial loads, reduced survival, and a substantial modulation of innate and adaptive immune defenses including an impaired onset and development of Mtb-specific CD4⁺ T cell responses and the accumulation of macrophages with increased arginase-1 production in the lungs. Our findings strongly indicate that IAV coinfection compromises the host’s ability to control Mtb infection via the production of IL-10, which was rapidly induced upon viral infection. The blockade of IL-10 receptor signaling reduced the bacterial load in coinfected mice to a level comparable to that in Mtb-only-infected animals. Taken together, our data suggest that IL-10 signaling constitutes a major pathway that enhances susceptibility to Mtb during concurrent IAV infection.

IL-10R signaling constitutes a major pathway that impairs control of Mycobacterium tuberculosis during influenza co-infection.

The brain-immune cells axis controls tissue specific immunopathology

During viral infections, cell death can be induced as a direct result of cytopathic virus replication in various cell types and tissues or as an immune response of the host to the infectious agent. This leads to an infiltration of inflammatory cells, causing subsequent tissue damage. The balance between effective elimination of the pathogen and prevention of fatal tissue damage is decisive for life. The host has developed various mechanisms to inhibit excessive immune responses.

Respiratory Influenza A Virus Infection Triggers Local and Systemic Natural Killer Cell Activation via Toll-Like Receptor 7

The innate immune system senses influenza A virus (IAV) through different pathogen-recognition receptors including Toll-like receptor 7 (TLR7). Downstream of viral recognition natural killer (NK) cells are activated as part of the anti-IAV immune response. Despite the known decisive role of TLR7 for NK cell activation by therapeutic immunostimulatory RNAs, the contribution of TLR7 to the NK cell response following IAV infection has not been addressed. We have analyzed lung cytokine responses as well as the activation, interferon (IFN)-γ production, and cytotoxicity of lung and splenic NK cells following sublethal respiratory IAV infection in wild-type and TLR7ko mice. Early airway IFN-γ levels as well as the induction of lung NK cell CD69 expression and IFN-γ production in response to IAV infection were significantly attenuated in TLR7-deficient hosts. Strikingly, respiratory IAV infection also primed splenic NK cells for IFN-γ production, degranulation, and target cell lysis, all of which were fully dependent on TLR7. At the same time, lung type I IFN levels were significantly reduced in TLR7ko mice early following IAV infection, displaying a potential upstream mechanism of the attenuated NK cell activation observed. Taken together, our data clearly demonstrate a specific role for TLR7 signaling in local and systemic NK cell activation following respiratory IAV infection despite the presence of redundant innate IAV-recognition pathways.

Intrabodies against the Polysialyltransferases ST8SiaII and ST8SiaIV inhibit Polysialylation of NCAM in rhabdomyosarcoma tumor cells

Background

Polysialic acid (polySia) is a carbohydrate modification of the neural cell adhesion molecule (NCAM), which is implicated in neural differentiation and plays an important role in tumor development and metastasis. Polysialylation of NCAM is mediated by two Golgi-resident polysialyltransferases (polyST) ST8SiaII and ST8SiaIV. Intracellular antibodies (intrabodies; IB) expressed inside the ER and retaining proteins passing the ER such as cell surface receptors or secretory proteins provide an efficient means of protein knockdown. To inhibit the function of ST8SiaII and ST8SiaIV specific ER IBs were generated starting from two corresponding hybridoma clones. Both IBs αST8SiaII-IB and αST8SiaIV-IB were constructed in the scFv format and their functions characterized in vitro and in vivo.

Results

IBs directed against the polySTs prevented the translocation of the enzymes from the ER to the Golgi-apparatus. Co-immunoprecipitation of ST8SiaII and ST8SiaIV with the corresponding IBs confirmed the intracellular interaction with their cognate antigens. In CHO cells overexpressing ST8SiaII and ST8SiaIV, respectively, the transfection with αST8SiaII-IB or αST8SiaIV-IB inhibited significantly the cell surface expression of polysialylated NCAM. Furthermore stable expression of ST8SiaII-IB, ST8SiaIV-IB and luciferase in the rhabdomyosarcoma cell line TE671 reduced cell surface expression of polySia and delayed tumor growth if cells were xenografted into C57BL/6 J RAG-2 mice.

Conclusion

Data obtained strongly indicate that αST8SiaII-IB and αST8SiaIV-IB are promising experimental tools to analyze the individual role of the two enzymes during brain development and during migration and proliferation of tumor cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-017-0360-7) contains supplementary material, which is available to authorized users.

Fast type I interferon response protects astrocytes from flavivirus infection and virus-induced cytopathic effects

Background

Neurotropic flaviviruses such as tick-borne encephalitis virus (TBEV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and Zika virus (ZIKV) are causative agents of severe brain-related diseases including meningitis, encephalitis, and microcephaly. We have previously shown that local type I interferon response within the central nervous system (CNS) is involved in the protection of mice against tick-borne flavivirus infection. However, the cells responsible for mounting this protective response are not defined.

Methods

Primary astrocytes were isolated from wild-type (WT) and interferon alpha receptor knock out (IFNAR^−/−) mice and infected with neurotropic flaviviruses. Viral replication and spread, IFN induction and response, and cellular viability were analyzed. Transcriptional levels in primary astrocytes treated with interferon or supernatant from virus-infected cells were analyzed by RNA sequencing and evaluated by different bioinformatics tools.

Results

Here, we show that astrocytes control viral replication of different TBEV strains, JEV, WNV, and ZIKV. In contrast to fibroblast, astrocytes mount a rapid interferon response and restrict viral spread. Furthermore, basal expression levels of key interferon-stimulated genes are high in astrocytes compared to mouse embryonic fibroblasts. Bioinformatic analysis of RNA-sequencing data reveals that astrocytes have established a basal antiviral state which contributes to the rapid viral recognition and upregulation of interferons. The most highly upregulated pathways in neighboring cells were linked to type I interferon response and innate immunity. The restriction in viral growth was dependent on interferon signaling, since loss of the interferon receptor, or its blockade in wild-type cells, resulted in high viral replication and virus-induced cytopathic effects. Astrocyte supernatant from TBEV-infected cells can restrict TBEV growth in astrocytes already 6 h post infection, the effect on neurons is highly reinforced, and astrocyte supernatant from 3 h post infection is already protective.

Conclusions

These findings suggest that the combination of an intrinsic constitutive antiviral response and the fast induction of type I IFN production by astrocytes play an important role in self-protection of astrocytes and suppression of flavivirus replication in the CNS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0748-7) contains supplementary material, which is available to authorized users.

Brain heterogeneity leads to differential innate immune responses and modulates pathogenesis of viral infections

The central nervous system (CNS) is a highly complex organ with highly specialized cell subtypes. Viral infections often target specific structures of the brain and replicate in certain regions. Studies in mice deficient in type I Interferon (IFN) receptor or IFN-β have highlighted the importance of the type I IFN system against viral infections and non-viral autoimmune disorders in the CNS. Direct antiviral effects of type I IFNs appear to be crucial in limiting early spread of a number of viruses in CNS tissues. Increased efforts have been made to characterize IFN expression and responses in the brain. In this context, it is important to identify cells that produce IFN, decipher pathways leading to type I IFN expression and to characterize responding cells. In this review we give an overview about region specific aspects that influence local innate immune responses. The route of entry is critical, but also the susceptibility of different cell types, heterogeneity in subpopulations and micro-environmental cues play an important role in antiviral responses. Recent work has outlined the tremendous importance of type I IFNs, particularly in the limitation of viral spread within the CNS. This review will address recent advances in understanding the mechanisms of local type I IFN production and response, in the particular context of the CNS.

Type I Interferon Signaling Prevents IL-1β-Driven Lethal Systemic Hyperinflammation during Invasive Bacterial Infection of Soft Tissue

Type I interferons (IFN-Is) are fundamental for antiviral immunity, but their role in bacterial infections is contradictory and incompletely described. Streptococcus pyogenes activates IFN-I production in innate immune cells, and IFN-I receptor 1 (Ifnar1)-deficient mice are highly susceptible to S. pyogenes infection. Here we report that IFN-I signaling protects the host against invasive S. pyogenes infection by restricting inflammation-driven damage in distant tissues. Lethality following infection in Ifnar1-deficient mice is caused by systemically exacerbated levels of the proinflammatory cytokine IL-1β. Critical cellular effectors of IFN-I in vivo are LysM+ and CD11c+ myeloid cells, which exhibit suppression of Il1b transcription upon Ifnar1 engagement. These cells are also the major source of IFN-β, which is significantly induced by S. pyogenes 23S rRNA in an Irf5-dependent manner. Our study establishes IL-1β and IFN-I levels as key homeostatic variables of protective, yet tuned, immune responses against severe invasive bacterial infection.

In Vivo Visualizing the IFN-β Response Required for Tumor Growth Control in a Therapeutic Model of Polyadenylic-Polyuridylic Acid Administration

The crucial role that endogenously produced IFN-β plays in eliciting an immune response against cancer has recently started to be elucidated. Endogenous IFN-β has an important role in immune surveillance and control of tumor development. Accordingly, the role of TLR agonists as cancer therapeutic agents is being revisited via the strategy of intra/peritumoral injection with the idea of stimulating the production of endogenous type I IFN inside the tumor. Polyadenylic-polyuridylic acid (poly A:U) is a dsRNA mimetic explored empirically in cancer immunotherapy a long time ago with little knowledge regarding its mechanisms of action. In this work, we have in vivo visualized the IFN-β required for the antitumor immune response elicited in a therapeutic model of poly A:U administration. In this study, we have identified the role of host type I IFNs, cell populations that are sources of IFN-β in the tumor microenvironment, and other host requirements for tumor control in this model. One single peritumoral dose of poly A:U was sufficient to induce IFN-β, readily visualized in vivo. IFN-β production relied mainly on the activation of the transcription factor IFN regulatory factor 3 and the molecule UNC93B1, indicating that TLR3 is required for recognizing poly A:U. CD11c(+) cells were an important, but not the only source of IFN-β. Host type I IFN signaling was absolutely required for the reduced tumor growth, prolonged mice survival, and the strong antitumor-specific immune response elicited upon poly A:U administration. These findings add new perspectives to the use of IFN-β-inducing compounds in tumor therapy.

Type I Interferon response in olfactory bulb, the site of tick-borne flavivirus accumulation, is primarily regulated by IPS-1

BACKGROUND

Although type I interferons (IFNs)-key effectors of antiviral innate immunity are known to be induced via different pattern recognition receptors (PRRs), the cellular source and the relative contribution of different PRRs in host protection against viral infection is often unclear. IPS-1 is a downstream adaptor for retinoid-inducible gene I (RIG-I)-like receptor signaling. In this study, we investigate the relative contribution of IPS-1 in the innate immune response in the different brain regions during infection with tick-borne encephalitis virus (TBEV), a flavivirus that causes a variety of severe symptoms like hemorrhagic fevers, encephalitis, and meningitis in the human host.

METHODS

IPS-1 knockout mice were infected with TBEV/Langat virus (LGTV), and viral burden in the peripheral and the central nervous systems, type I IFN induction, brain infiltrating cells, and inflammatory response was analyzed.

RESULTS

We show that IPS-1 is indispensable for controlling TBEV and LGTV infections in the peripheral and central nervous system. Our data indicate that IPS-1 regulates neuropathogenicity in mice. IFN response is differentially regulated in distinct regions of the central nervous system (CNS) influencing viral tropism, as LGTV replication was mainly restricted to olfactory bulb in wild-type (WT) mice. In contrast to the other brain regions, IFN upregulation in the olfactory bulb was dependent on IPS-1 signaling. IPS-1 regulates basal levels of antiviral interferon-stimulated genes (ISGs) like viperin and IRF-1 which contributes to the establishment of early viral replication which inhibits STAT1 activation. This diminishes the antiviral response even in the presence of high IFN-β levels. Consequently, the absence of IPS-1 causes uncontrolled virus replication, in turn resulting in apoptosis, activation of microglia and astrocytes, elevated proinflammatory response, and recruitment of inflammatory cells into the CNS.

CONCLUSIONS

We show that LGTV replication is restricted to the olfactory bulb and that IPS-1 is a very important player in the olfactory bulb in shaping the innate immune response by inhibiting early viral replication and viral spread throughout the central nervous system. In the absence of IPS-1, higher viral replication leads to the evasion of antiviral response by inhibiting interferon signaling. Our data suggest that the local microenvironment of distinct brain regions is critical to determine virus permissiveness.

Concomitant TLR/RLH signaling of radioresistant and radiosensitive cells is essential for protection against vesicular stomatitis virus infection

Several studies indicated that TLR as well as retinoic acid-inducible gene I-like helicase (RLH) signaling contribute to vesicular stomatitis virus (VSV)-mediated triggering of type I IFN (IFN-I) responses. Nevertheless, TLR-deficient MyD88(-/-)Trif(-/-) mice and RLH-deficient caspase activation and recruitment domain adaptor inducing IFN-β (Cardif)(-/-) mice showed only marginally enhanced susceptibility to lethal VSV i.v. infection. Therefore, we addressed whether concomitant TLR and RLH signaling, or some other additional mechanism, played a role. To this end, we generated MyD88(-/-)Trif(-/-)Cardif(-/-) (MyTrCa(-/-)) mice that succumbed to low-dose i.v. VSV infection with similar kinetics as IFN-I receptor-deficient mice. Three independent approaches (i.e., analysis of IFN-α/β serum levels, experiments with IFN-β reporter mice, and investigation of local IFN-stimulated gene induction) revealed that MyTrCa(-/-) mice did not mount IFN-I responses following VSV infection. Of note, treatment with rIFN-α protected the animals, qualifying MyTrCa(-/-) mice as a model to study the contribution of different immune cell subsets to the production of antiviral IFN-I. Upon adoptive transfer of wild-type plasmacytoid dendritic cells and subsequent VSV infection, MyTrCa(-/-) mice displayed significantly reduced viral loads in peripheral organs and showed prolonged survival. On the contrary, adoptive transfer of wild-type myeloid dendritic cells did not have such effects. Analysis of bone marrow chimeric mice revealed that TLR and RLH signaling of radioresistant and radiosensitive cells was required for efficient protection. Thus, upon VSV infection, plasmacytoid dendritic cell-derived IFN-I primarily protects peripheral organs, whereas concomitant TLR and RLH signaling of radioresistant stroma cells as well as of radiosensitive immune cells is needed to effectively protect against lethal disease.

Delayed apoptosis of tumor associated neutrophils in the absence of endogenous IFN-β

The importance of neutrophils in tumor immune surveillance, invasive growth and angiogenesis becomes increasingly clear. Many of neutrophil activities are controlled by endogenous IFN-β. Here, we provide evidence that endogenous IFN-β is regulating the apoptosis of pro-angiogenic tumor infiltrating neutrophils by influencing both, the extrinsic as well as the intrinsic apoptosis pathways. Accordingly, the life span of tumor associated neutrophils (TANs) is remarkably prolonged in tumor bearing Ifnb1(-/-) mice compared to wild type controls. Lower expression of Fas, reactive oxygen species, active Caspase 3 and 9, as well as a change in expression pattern of proapoptotic and antiapoptotic members of the Bcl-2 family and the major apoptosome constituent Apaf-1 is observed under such conditions. In line with inhibition of apoptosis and the prolonged neutrophil survival, in the absence of endogenous IFN-β, a strong enhancement of G-CSF expression and PI3 Kinase phosphorylation is detected. These data explain the increased longevity of tumor infiltrating neutrophils and the accumulation of such cells in tumors. Taken together, our findings add to the important role of Type I IFN in immune surveillance against cancer.

Interferon regulatory factor-1 protects from fatal neurotropic infection with vesicular stomatitis virus by specific inhibition of viral replication in neurons

The innate immune system protects cells against invading viral pathogens by the auto- and paracrine action of type I interferon (IFN). In addition, the interferon regulatory factor (IRF)-1 can induce alternative intrinsic antiviral responses. Although both, type I IFN and IRF-1 mediate their antiviral action by inducing overlapping subsets of IFN stimulated genes, the functional role of this alternative antiviral action of IRF-1 in context of viral infections in vivo remains unknown. Here, we report that IRF-1 is essential to counteract the neuropathology of vesicular stomatitis virus (VSV). IFN- and IRF-1-dependent antiviral responses act sequentially to create a layered antiviral protection program against VSV infections. Upon intranasal infection, VSV is cleared in the presence or absence of IRF-1 in peripheral organs, but IRF-1^−/− mice continue to propagate the virus in the brain and succumb. Although rapid IFN induction leads to a decline in VSV titers early on, viral replication is re-enforced in the brains of IRF-1^−/− mice. While IFN provides short-term protection, IRF-1 is induced with delayed kinetics and controls viral replication at later stages of infection. IRF-1 has no influence on viral entry but inhibits viral replication in neurons and viral spread through the CNS, which leads to fatal inflammatory responses in the CNS. These data support a temporal, non-redundant antiviral function of type I IFN and IRF-1, the latter playing a crucial role in late time points of VSV infection in the brain.

IRFs are a family of transcription factors that play a key role in viral defense. Apart from their function in the adaptive immune system, recent work revealed that several IRFs contribute to antiviral response independent of secreted IFN. IRFs have been developed earlier in evolution than IFN and are regarded as precursor of today's IFN system, acting only on an intrinsic level. IRF-1 by itself exhibits antiviral effects that are exerted by the induction of a set of genes that overlaps the set of IFN-induced genes (ISGs). Our data show that IRF-1 contributes decisively for the protection of mice from neurotropic Vesicular stomatitis virus (VSV), a virus similar to rabies virus. Mice, deficient in IRF-1, are highly vulnerable to VSV infection and succumb with signs of encephalitis. Although type I IFN action is a prerequisite for survival from the infection, IRF-1 becomes increasingly crucial in neuronal tissue at a time point where clearance of the virus has not been achieved. The data highlight the importance of IRF-1 as an antiviral agent that acts in combination with the IFN system.

Cell entry, efficient RNA replication, and production of infectious hepatitis C virus progeny in mouse liver-derived cells

Only humans and chimpanzees are susceptible to chronic infection by hepatitis C virus (HCV). The restricted species tropism of HCV is determined by distinct host factor requirements at different steps of the viral life cycle. In addition, effective innate immune targeting precludes efficient propagation of HCV in nonhuman cells. Species-specificity of HCV host factor usage for cell entry and virus release has been explored. However, the reason for inefficient HCV RNA replication efficiency in mouse liver cells remains elusive. To address this, we generated novel mouse liver-derived cell lines with specific lesions in mitochondrial antiviral signaling protein (MAVS), interferon regulatory factor 3 (IRF3), or Interferon-α/β receptor (IFNAR) by in vivo immortalization. Blunted innate immune responses in these cells modestly increased HCV RNA replication. However, ectopic expression of liver-specific human microRNA 122 (miR-122) further boosted RNA replication in all knockout cell lines. Remarkably, MAVS(-/-) miR-122 cells sustained vigorous HCV RNA replication, attaining levels comparable to the highly permissive human hepatoma cell line Huh-7.5. RNA replication was dependent on mouse cyclophilin and phosphatidylinositol-4 kinase III alpha (PI4KIIIα) and was also observed after transfection of full-length viral RNA. Additionally, ectopic expression of either human or mouse apolipoprotein E (ApoE) was sufficient to permit release of infectious particles. Finally, expression of human entry cofactors rendered these cells permissive to HCV infection, thus confirming that all steps of the HCV replication cycle can be reconstituted in mouse liver-derived cells.

CONCLUSION

Blunted innate immunity, abundant miR-122, and HCV entry factor expression permits propagation of HCV in mouse liver-derived cell lines.

Hepatitis C virus replication in mouse cells is restricted by IFN-dependent and -independent mechanisms

BACKGROUND & AIMS

Current treatment strategies for hepatitis C virus (HCV) infection include pegylated interferon (IFN)-alfa and ribavirin. Approximately 50% of patients control HCV infection after treatment, but the broad range of patients' outcomes and responses to treatment, among all genotypes, indicates a role for host factors. Although the IFN system is important in limiting HCV replication, the virus has evolved mechanisms to circumvent the IFN response. However, direct, IFN-independent antiviral processes also might help control HCV replication. We examined the role of IFN-independent responses against HCV replication.

METHODS

We analyzed replication of the subgenomic JFH1 replicon in embryonic fibroblasts and primary hepatocytes from mice with disruptions in genes encoding factors in the IFN-dependent and alternative antiviral pathways (signal transducers and activators of transcription 1 [STAT1], protein kinase R, interferon regulatory factors (IRF) IRF-1, IRF-3, IRF-5, IRF-7, mitochondrial antiviral signaling molecule [MAVS], and IFN receptor [IFNAR]). We also assessed the effects of expression of these factors by mouse primary hepatocytes on HCV replication.

RESULTS

In addition to IRF-3- and IFN-mediated antiviral responses, IFN-independent, but IRF-1- and IRF-5-dependent mechanisms, restrict HCV replication in mouse embryonic fibroblasts. In primary hepatocytes these IFN-independent require MAVS and IRF-1.

CONCLUSIONS

HCV replication is limited by interferon-mediated pathways as well pathways that are independent of type I IFNs. IRF1 and IRF5 control IFN-independent signaling events that lead to antiviral responses. We observed antiviral roles of IRF1 and IRF5 that were IFN-independent and cell-type specific. These mechanisms are important in controlling viruses that interfere with the IFN signaling because cells retain the ability to induce functional but local antiviral states through expression of interferon-stimulated genes.

DNA-Based Vaccination with Polycistronic Expression Plasmids

DNA-based vaccination is a potent technique to prime cellular (T-cell mediated) immune responses (reviewed in 1). Many details of the priming of T-cell precursors by antigen translated from injected expression plasmid DNA are unknown. The relevant cell that is transfected in situ after DNA vaccination and that can process and present the protein in an immunogenic form has not yet been identified. Alternatively, the transfected cell may initiate 'cross-priming' in vivo by transferring processed antigen to a professional antigen-presenting cell (APC).

IRF-1 expression is essential for natural killer cells to suppress metastasis

IFN-γ promotes tumoral immune surveillance, but its involvement in controlling metastases is less clear. Using a mouse model of pulmonary metastases, we show that local IFN-γ treatment inhibits formation of metastases through its regulation of IRF-1 in tumor cells. IRF-1 is an IFN-γ-induced transcription factor pivotal in the regulation of infection and inflammation. IRF-1 blockade abolished the inhibitory effect of IFN-γ on tumor metastases, whereas ectopic expression of IRF-1 phenocopied the inhibitory effects of IFN-γ. IRF-1 did not affect the survival of tumor cells in the circulation or their infiltration into lungs, but it was essential to support the pulmonary attraction and activation of natural killer (NK) cells. Depleting NK cells from mice abolished the protective effect of IFN-γ or IRF-1 on metastases. In addition, cytotoxicity assays revealed that tumor cells expressing IRF-1 were targeted more effectively by NK cells than IRF-1 nonexpressing tumor cells. Moreover, NK cells isolated from lungs inoculated with IRF-1-expressing tumor cells exhibit a greater cytotoxic activity. Mechanistic investigations revealed that IRF-1-induced NK cell cytotoxicity was independent of perforin and granzyme B but dependent on the NK cell activating receptor DNAM-1. Taken together, our findings establish IRF-1 as an essential mediator of the cross-talk between tumor cells and NK cells that mediate immune surveillance in the metastatic niche.

Perspectives on Regulatory T Cell Therapies

Adoptive transfer in animal models clearly indicate an essential role of CD4+ CD25+ FOXP3+ regulatory T (T(reg)) cells in prevention and treatment of autoimmune and graft-versus-host disease. Thus, T(reg) cell therapies and development of drugs that specifically enhance T(reg) cell function and development represent promising tools to establish dominant tolerance. So far, lack of specific markers to differentiate human T(reg) cells from activated CD4+ CD25+ effector T cells, which also express FOXP3 at different levels, hampered such an approach. Recent identification of the orphan receptor glycoprotein-A repetitions predominant (GARP or LRRC32) as T(reg) cell-specific key molecule that dominantly controls FOXP3 via a positive feedback loop opens up new perspectives for molecular and cellular therapies. This brief review focuses on the role of GARP as a safeguard of a complex regulatory network of human T(reg) cells and its implications for regulatory T cell therapies in autoimmunity and graft-versus-host disease.

GARP: a key receptor controlling FOXP3 in human regulatory T cells

Recent evidence suggests that regulatory pathways might control sustained high levels of FOXP3 in regulatory CD4(+)CD25(hi) T (T(reg)) cells. Based on transcriptional profiling of ex vivo activated T(reg) and helper CD4(+)CD25(-) T (T(h)) cells we have identified GARP (glycoprotein-A repetitions predominant), LGALS3 (lectin, galactoside-binding, soluble, 3) and LGMN (legumain) as novel genes implicated in human T(reg) cell function, which are induced upon T-cell receptor stimulation. Retroviral overexpression of GARP in antigen-specific T(h) cells leads to an efficient and stable re-programming of an effector T cell towards a regulatory T cell, which involves up-regulation of FOXP3, LGALS3, LGMN and other T(reg)-associated markers. In contrast, overexpression of LGALS3 and LGMN enhance FOXP3 and GARP expression, but only partially induced a regulatory phenotype. Lentiviral down-regulation of GARP in T(reg) cells significantly impaired the suppressor function and was associated with down-regulation of FOXP3. Moreover, down-regulation of FOXP3 resulted in similar phenotypic changes and down-regulation of GARP. This provides compelling evidence for a GARP-FOXP3 positive feedback loop and provides a rational molecular basis for the known difference between natural and transforming growth factor-beta induced T(reg) cells as we show here that the latter do not up-regulate GARP. In summary, we have identified GARP as a key receptor controlling FOXP3 in T(reg) cells following T-cell activation in a positive feedback loop assisted by LGALS3 and LGMN, which represents a promising new system for the therapeutic manipulation of T cells in human disease.

Type I IFN-induced, NKT cell-mediated negative control of CD8 T cell priming by dendritic cells

We investigated the negative effect of type I IFN (IFN-I) on the priming of specific CD8 T cell immunity. Priming of murine CD8 T cells is down-modulated if Ag is codelivered with IFN-I-inducing polyinosinic:polycytidylic acid (pI/C) that induces (NK cell- and T/B cell-independent) acute changes in the composition and surface phenotype of dendritic cells (DC). In wild-type but not IFN-I receptor-deficient mice, pI/C reduces the plasmacytoid DC but expands the CD8(+) conventional DC (cDC) population and up-regulates surface expression of activation-associated (CD69, BST2), MHC (class I/II), costimulator (CD40, CD80/CD86), and coinhibitor (PD-L1/L2) molecules by cDC. Naive T cells are efficiently primed in vitro by IFN-I-stimulated CD8 cDC (the key APC involved in CD8 T cell priming) although these DC produced less IL-12 p40 and IL-6. pI/C (IFN-I)-mediated down modulation of CD8 T cell priming in vivo was not observed in NKT cell-deficient CD1d(-/-) mice. CD8 cDC from pI/C-treated mice inefficiently stimulated IFN-gamma, IL-4, and IL-2 responses of NKT cells. In vitro, CD8 cDC that had activated NKT cells in the presence of IFN-I primed CD8 T cells that produced less IFN-gamma but more IL-10. The described immunosuppressive effect of IFN-I thus involves an NKT cell-mediated change in the phenotype of CD8 cDC that favors priming of IL-10-producing CD8 T cells. In the presence of IFN-I, NKT cells hence impair the competence of CD8 cDC to prime proinflammatory CD8 T cell responses.

Tumor suppression by IFN regulatory factor-1 is mediated by transcriptional down-regulation of cyclin D1

IFNs have been ascribed to mediate antitumor effects. IFN regulatory factor-1 (IRF-1) is a major target gene of IFNs. It inhibits cell proliferation and oncogenic transformation. Here, we show that 60% of all mRNAs deregulated by oncogenic transformation mediated by c-myc and H-ras are reverted to the expression levels of nontransformed cells by IRF-1. These include cell cycle-regulating genes. An indirect target is cyclin D1. Activation of IRF-1 decreased cyclin D1 expression and cyclin-dependent kinase 4 kinase activity concomitant with change in the levels of hyperphosphorylated retinoblastoma protein. These effects are mediated by inhibition of the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathway and a transcriptional repression of cyclin D1. As shown by in vitro assays and tumor growth in nude mice, IRF-1-mediated effects on cell cycle progression were found to be overridden by ectopic expression of cyclin D1. Conversely, decrease of cyclin D1 by RNA interference experiments prevents transformation and tumor growth. The data show that cyclin D1 is a key target for IRF-1-mediated tumor-suppressive effects.

Distinct modes of action applied by transcription factors STAT1 and IRF1 to initiate transcription of the IFN-gamma-inducible gbp2 gene

A subgroup of genes induced by IFN-gamma requires both STAT1 and IRF1 for transcriptional activation. Using WT, stat1(-/-), or irf1(-/-) cells, we analyzed the changes induced by IFN-gamma in gbp2 promoter chromatin. STAT1 associated with the promoter independently of IRF1 and played an essential role in the ordered recruitment of the coactivator/histone acetyl transferase CREB-binding protein (CBP) and the histone deacetylase HDAC1. Hyperacetylation of histone 4 also required STAT1. Phosphorylation at S727 in the transactivating domain increased transcriptional activity of STAT1. In cells expressing a STAT1S727A-mutant CBP recruitment, histone 4 hyperacetylation and RNA polymerase II association with the gbp2 promoter were strongly reduced. IRF1 association with the gbp2 promoter followed that of STAT1, but STAT1 association with DNA or histone hyperacetylation were not necessary for IRF1 binding. RNA polymerase II association with the gbp2 promoter required both STAT1 and IRF1, suggesting that both proteins mediate essential steps in transcriptional activation. IRF1, but not STAT1, was found to coimmunoprecipitate with RNA polymerase II. Together, the data support the assumption that the main role of STAT1 in activating gbp2 transcription is to provide transcriptionally competent chromatin, whereas the function of IRF1 may lie in directly contacting RNA polymerase II-containing transcriptional complexes.

Priming Protective CD8 T Cell Immunity by DNA Vaccines Encoding Chimeric, Stress Protein-Capturing Tumor-Associated Antigen

DNA vaccines encoding heat shock protein (hsp)-capturing, chimeric peptides containing antigenic determinants of the tumor-associated Ag (TAA) gp70 (an envelope protein of endogenous retrovirus) primed stable, specific, and tumor-protective CD8 T cell immunity. Expression of gp70 transcripts was detectable in most normal tissues but was particularly striking in some (but not all) tumor cell lines tested (including the adenocarcinoma cell line CT26). An approximately 200 residue gp70 fragment or its L(d)-binding antigenic AH1 peptide cloned in-frame behind an hsp-capturing (cT(272)) or noncapturing (T(60)) N-terminal large SV40 tumor Ag sequence was expressed as either hsp-binding or -nonbinding chimeric Ags. Only hsp-capturing, chimeric fusion proteins were expressed efficiently in transfected cell lines and primed TAA-specific CD8 T cell immunity. This immunity mediated protection in the CT26 and mKSA models. A vaccination strategy based on delivering antigenic, hsp-associated TAA fragments can thus prime protective CD8 T cell immunity even if these TAA are of low intrinsic immunogenicity.

Innate immune responses in NF-kappaB-repressing factor-deficient mice

NF-kappaB-repressing factor (NRF) is a transcriptional silencer protein that specifically counteracts the basal activity of several NF-kappaB-dependent promoters by direct binding to specific neighboring DNA sequences. In cell culture experiments, the reduction of NRF mRNA leads to a derepression of beta interferon, interleukin-8, and inducible nitric oxide synthase transcription. The X chromosome-located single-copy NRF gene is ubiquitously expressed and encodes a protein of 690 amino acids. The N-terminal part contains a nuclear localization signal, the DNA-binding domain, and the NF-kappaB-repressing domain, while the C-terminal part is responsible for double-stranded RNA binding and nucleolar localization. To study the function of NRF in a systemic context, transgenic mice lacking the NRF gene were created. Against predictions from in vitro experiments, mice with a deletion of the NRF gene are viable and have a phenotype that is indistinguishable from wild-type mice, even after challenge with different pathogens. The data hint towards an unexpected functional redundancy of NRF.

Less chronic pain following mesh fixation using a fibrin sealant in TEP inguinal hernia repair

Endoscopic hernia repair methods have become increasingly popular over the past 15 years. The postulated main advantages of the endoscopic technique are less postoperative pain, early recovery and lower recurrence rates. Fixation of the endoscopic mesh seems to be necessary to minimize the risk of recurrence. Stapling has been implicated to cause chronic inguinal pain syndromes. We performed a retrospective study on male patients who were endoscopically operated on primary inguinal hernias. Our aim was to clarify whether mesh fixation using a fibrin sealant is as safe and reliable as conventional stapling. Additionally, we compared the prevalence of chronic inguinal pain. A standardized population of 133 male patients (mean age 55.9 years) with 186 (80 unilateral; 53 bilateral) consecutive primary laparoscopic total extraperitoneal inguinal hernia repairs was assigned to two groups, depending on whether stapling or a fibrin sealant had been used for mesh fixation. A retrospective case control study was performed to conduct statistical analysis based on the following parameters: recurrence, complications, chronic inguinal pain, foreign body sensation and numbness. Hernia repairs numbering 173 (staples n=87; fibrin n=86) were followed up for a mean duration of 23.7 (11-47) months. The prevalence of chronic inguinal pain was significantly (P=0.002; Fisher exact test) higher in the stapled group-20.7% than in the fibrin sealant group with a prevalence of 4.7%. In terms of recurrence rate, complications and foreign body sensation, fewer patients were affected in the fibrin group than in the reference population, although the differences were not statistically significant. There were no major complications in either of the groups. The mean postoperative stay in hospital was 1.4 days. Fibrin sealing is as effective as stapling in providing secure mesh fixation. The fibrin group displayed a statistically significant lower prevalence of chronic pain syndromes. Mesh sealing provides adequate fixation and reduces the risk of chronic inguinal pain as a complication of the intervention.

Establishment of murine cell lines by constitutive and conditional immortalization

Mouse cell lines were immortalized by introduction of specific immortalizing genes. Embryonic and adult animals and an embryonal stem cell line were used as a source of primary cells. The immortalizing genes were either introduced by DNA transfection or by ecotropic retrovirus transduction. Fibroblasts were obtained by expression of SV40 virus large T antigen (TAg). The properties of the resulting fibroblast cell lines were reproducible, independent of the donor mouse strains employed and the cells showed no transformed properties in vitro and did not form tumors in vivo. Endothelial cell lines were generated by Polyoma virus middle T antigen expression in primary embryonal cells. These cell lines consistently expressed relevant endothelial cell surface markers. Since the expression of the immortalizing genes was expected to strongly influence the cellular characteristics fibroblastoid cells were reversibly immortalized by using a vector that allows conditional expression of the TAg. Under inducing conditions, these cells exhibited properties that were highly similar to the properties of constitutively immortalized cells. In the absence of TAg expression, cell proliferation stops. Cell growth is resumed when TAg expression is restored. Gene expression profiling indicates that TAg influences the expression levels of more than 1000 genes that are involved in diverse cellular processes. The data show that conditionally immortalized cell lines have several advantageous properties over constitutively immortalized cells.

Type I IFN negatively regulates CD8+ T cell responses through IL-10-producing CD4+ T regulatory 1 cells

Pleiotropic, immunomodulatory effects of type I IFN on T cell responses are emerging. We used vaccine-induced, antiviral CD8(+) T cell responses in IFN-beta (IFN-beta(-/-))- or type I IFN receptor (IFNAR(-/-))-deficient mice to study immunomodulating effects of type I IFN that are not complicated by the interference of a concomitant virus infection. Compared with normal B6 mice, IFNAR(-/-) or IFN-beta(-/-) mice have normal numbers of CD4(+) and CD8(+) T cells, and CD25(+)FoxP3(+) T regulatory (T(R)) cells in liver and spleen. Twice as many CD8(+) T cells specific for different class I-restricted epitopes develop in IFNAR(-/-) or IFN-beta(-/-) mice than in normal animals after peptide- or DNA-based vaccination. IFN-gamma and TNF-alpha production and clonal expansion of specific CD8(+) T cells from normal and knockout mice are similar. CD25(+)FoxP3(+) T(R) cells down-modulate vaccine-primed CD8(+) T cell responses in normal, IFNAR(-/-), or IFN-beta(-/-) mice to a comparable extent. Low IFN-alpha or IFN-beta doses (500-10(3) U/mouse) down-modulate CD8(+) T cells priming in vivo. IFNAR- and IFN-beta-deficient mice generate 2- to 3-fold lower numbers of IL-10-producing CD4(+) T cells after polyclonal or specific stimulation in vitro or in vivo. CD8(+) T cell responses are thus subjected to negative control by both CD25(+)FoxP3(+) T(R) cells and CD4(+)IL-10(+) T(R1) cells, but only development of the latter T(R) cells depends on type I IFN.