AMELIA CRISTINA PINTO - Academia.edu (original) (raw)

Papers by AMELIA CRISTINA PINTO

Research paper thumbnail of Antigen-independent recruitment of CTL to pancreatic islets expressing an NKG2D ligand (44.38)

The Journal of Immunology

The mechanisms by which CTLs enter and are retained in non-lymphoid tissue are not well-character... more The mechanisms by which CTLs enter and are retained in non-lymphoid tissue are not well-characterized. Using a novel transgenic mouse expressing the NKG2D ligand RAE1ϵ in β-islet cells of the pancreas, we found RAE1 expression was sufficient to induce the recruitment of adoptively transferred CTLs to islets. This was dependent on NKG2D expression by the CTLs and independent of antigen recognition. While transgenic mice did not develop diabetes, RAE1 expression was sufficient to induce insulitis in older, unmanipulated transgenic mice that was enhanced by viral infection and pancreatic inflammation. Surprisingly, the recruitment of CTLs resulted in the subsequent recruitment of a large number of endogenous lymphocytes. These results demonstrate that the expression of NKG2D ligands in islets is sufficient to recruit CTLs and induce a significant insulitis.

Research paper thumbnail of The impact of type I interferon on the development of the adaptive immune response (67.14)

The Journal of Immunology

Determining the impact of type I interferon on immune responses using mice missing the common IFN... more Determining the impact of type I interferon on immune responses using mice missing the common IFN-α/β signaling receptor (IFNAR- /-) is limited to studying the functions of type I IFN at all stages of viral infection. To define the temporal functions of type I IFN signaling in the context of infection by West Nile virus (WNV), we treated mice with MAR1-5A3, a neutralizing, non cell-depleting anti-IFNAR antibody at later stages of infection. Inhibition of type I IFN signaling at or before day 2 after infection was associated with markedly enhanced viral burden, whereas treatment at day 4 altered WNV dissemination less dramatically. Blockade of type I IFN signaling starting at day 4 induced dysfunctional CD8+ T cells with depressed cytokine responses and expression of phenotypic markers suggesting exhaustion. The later maturation phase (days 4-8) of anti-WNV CD8+ T cell development requires type I IFN signaling. Collectively, our results suggest that cell non-autonomous type I IFN sig...

Research paper thumbnail of Interferon-λ restricts West Nile virus neuroinvasion by tightening the blood-brain barrier

Science translational medicine, Jan 22, 2015

Although interferon-λ [also known as type III interferon or interleukin-28 (IL-28)/IL-29] restric... more Although interferon-λ [also known as type III interferon or interleukin-28 (IL-28)/IL-29] restricts infection by several viruses, its inhibitory mechanism has remained uncertain. We used recombinant interferon-λ and mice lacking the interferon-λ receptor (IFNLR1) to evaluate the effect of interferon-λ on infection with West Nile virus, an encephalitic flavivirus. Cell culture studies in mouse keratinocytes and dendritic cells showed no direct antiviral effect of exogenous interferon-λ, even though expression of interferon-stimulated genes was induced. We observed no differences in West Nile virus burden between wild-type and Ifnlr1(-/-) mice in the draining lymph nodes, spleen, or blood. We detected increased West Nile virus infection in the brain and spinal cord of Ifnlr1(-/-) mice, yet this was not associated with a direct antiviral effect in mouse neurons. Instead, we observed an increase in blood-brain barrier permeability in Ifnlr1(-/-) mice. Treatment of mice with pegylated in...

Research paper thumbnail of Oropouche Virus Infection and Pathogenesis Are Restricted by MAVS, IRF-3, IRF-7, and Type I Interferon Signaling Pathways in Nonmyeloid Cells

Journal of Virology, 2015

Oropouche virus (OROV) is a member of the Orthobunyavirus genus in the Bunyaviridae family and a ... more Oropouche virus (OROV) is a member of the Orthobunyavirus genus in the Bunyaviridae family and a prominent cause of insect-transmitted viral disease in Central and South America. Despite its clinical relevance, little is known about OROV pathogenesis. To define the host defense pathways that control OROV infection and disease, we evaluated OROV pathogenesis and immune responses in primary cells and mice that were deficient in the RIG-I-like receptor signaling pathway (MDA5, RIG-I, or MAVS), downstream regulatory transcription factors (IRF-3 or IRF-7), beta interferon (IFN-β), or the receptor for type I IFN signaling (IFNAR). OROV replicated to higher levels in primary fibroblasts and dendritic cells lacking MAVS signaling, the transcription factors IRF-3 and IRF-7, or IFNAR than in wild-type (WT) cells. In mice, deletion of IFNAR, MAVS, or IRF-3 and IRF-7 resulted in uncontrolled OROV replication, hypercytokinemia, extensive liver damage, and death, whereas WT congenic animals faile...

Research paper thumbnail of Interferon regulatory factor 5-dependent immune responses in the draining lymph node protect against West Nile virus infection

Journal of virology, 2014

Upon activation of Toll-like and RIG-I-like receptor signaling pathways, the transcription factor... more Upon activation of Toll-like and RIG-I-like receptor signaling pathways, the transcription factor IRF5 translocates to the nucleus and induces antiviral immune programs. The recent discovery of a homozygous mutation in the immunoregulatory gene guanine exchange factor dedicator of cytokinesis 2 (Dock2mu/mu) in several Irf5-/- mouse colonies has complicated interpretation of immune functions previously ascribed to IRF5. To define the antiviral functions of IRF5 in vivo, we infected backcrossed Irf5-/-×Dock2wt/wt mice (here called Irf5-/- mice) and independently generated CMV-Cre Irf5fl/fl mice with West Nile virus (WNV), a pathogenic neurotropic flavivirus. Compared to congenic wild-type animals, Irf5-/- and CMV-Cre Irf5fl/fl mice were more vulnerable to WNV infection, and this phenotype was associated with increased infection in peripheral organs, which resulted in higher virus titers in the central nervous system. The loss of IRF5, however, was associated with only small difference...

Research paper thumbnail of c-Myc-induced transcription factor AP4 is required for host protection mediated by CD8+ T cells

Nature Immunology, 2014

Although c-Myc is essential to establish a metabolically active and proliferative state in T cell... more Although c-Myc is essential to establish a metabolically active and proliferative state in T cells after priming, its expression is transient. It remains unknown how T cell activation is maintained after c-Myc down-regulation. Here, we identify AP4 as the transcription factor that is induced by c-Myc and sustains activation of antigen-specific CD8 + T cells. Despite normal priming, AP4deficient CD8 + T cells fail to continue transcription of a broad range of c-Myc-dependent targets. Mice lacking AP4 specifically in CD8 + T cells showed enhanced susceptibility to West Nile virus infection. Genome-wide analysis suggests that many activation-induced metabolic genes are shared targets of c-Myc and AP4. Thus, AP4 maintains c-Myc-initiated cellular activation programs in CD8 + T cells to control microbial infections. Protective immunity by CD8 + T cells is critical for host defense against many pathogens that cause death or chronic infection. During an acute infection by a virus or intracellular bacterium, antigen (Ag)-specific CD8 + T cells are primed by signals through the T cell receptor (TCR), co-stimulatory molecules and cytokine receptors and undergo rapid expansion, effector differentiation, and memory cell formation 1, 2. In the priming phase, activated CD8 + T cells grow in size by increasing global gene transcription and protein translation and utilize aerobic glycolysis pathways to produce the energy and materials for biosynthesis prior to cell cycle entry 3, 4, 5, 6, 7. Previous studies established that the transcription factor (TF) c-Myc is essential for the initiation of the global cellular activation Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Research paper thumbnail of The lectin pathway of complement activation contributes to protection from West Nile virus infection

Virology, 2011

The function of the lectin pathway of complement activation in vivo against West Nile virus (WNV)... more The function of the lectin pathway of complement activation in vivo against West Nile virus (WNV) or many other pathogenic viruses has not been defined. Mice deficient in lectin pathway recognition molecules (mannose binding lectin-A (MBL-A) and mannose binding lectin-C (MBL-C)) or the effector enzyme mannanbinding lectin-associated serine protease-2 (MASP-2), were more vulnerable to WNV infection than wild type mice. Compared with studies of mice deficient in factors of the classical or alternative pathway, MBL-A −/− × MBL-C −/− or MASP-2 −/− mice showed a less severe course of WNV infection. Indeed, a deficiency in lectin pathway activation did not significantly affect the kinetics of viral spread to the central nervous system (CNS) nor did it profoundly alter generation of adaptive B and T cell immune responses. We conclude that MBLmediated recognition and lectin pathway activation have important yet subordinate functions in protecting against WNV infection and disease.

Research paper thumbnail of Hidden death gene in ‘flu

Trends in Microbiology, 2002

Influenza A virus (IAV) is a significant human pathogen that is responsible for millions of death... more Influenza A virus (IAV) is a significant human pathogen that is responsible for millions of deaths across the globe. Although sequenced >20 years ago, no new gene products had been discovered until recently. Now, Chen et al. [1xA novel influenza A virus mitochondrial protein that induces cell death. Chen, W. et al. Nat. Med. 2001; 7: 1306–1312Crossref | Scopus (635)See all References][1] have described a novel protein encoded by IAV.This new protein was identified as a novel 87-residue ORF while scanning alternative reading-frame peptides for antigenicity. After identifying the new ORF (PB1-F2), the group confirmed that the reading frame was both transcribed and translated in IAV-infected cells, indicating that PB1-F2 was a bona fide IAV gene product. Interestingly, PB1-F2 was found to localize in the mitochondria and, when expressed in IAV-infected cells, resulted in increased apoptotic cell death.Although an in vivo correlation has not yet been established, the authors hypothesize that PB1-F2-induced apoptosis might enhance viral dissemination and reduce immunological responses by directly killing innate immune cells such as monocytes and macrophages. The identification of this novel gene product could provide a greater understanding of how IAV might evade the host immune response.

Research paper thumbnail of Deficient IFN Signaling by Myeloid Cells Leads to MAVS-Dependent Virus-Induced Sepsis

PLoS Pathogens, 2014

The type I interferon (IFN) signaling response limits infection of many RNA and DNA viruses. To d... more The type I interferon (IFN) signaling response limits infection of many RNA and DNA viruses. To define key cell types that require type I IFN signaling to orchestrate immunity against West Nile virus (WNV), we infected mice with conditional deletions of the type I IFN receptor (IFNAR) gene. Deletion of the Ifnar gene in subsets of myeloid cells resulted in uncontrolled WNV replication, vasoactive cytokine production, sepsis, organ damage, and death that were remarkably similar to infection of Ifnar 2/2 mice completely lacking type I IFN signaling. In Mavs 2/2 6Ifnar 2/2 myeloid cells and mice lacking both Ifnar and the RIG-I-like receptor adaptor gene Mavs, cytokine production was muted despite high levels of WNV infection. Thus, in myeloid cells, viral infection triggers signaling through MAVS to induce proinflammatory cytokines that can result in sepsis and organ damage. Viral pathogenesis was caused in part by massive complement activation, as liver damage was minimized in animals lacking complement components C3 or factor B or treated with neutralizing anti-C5 antibodies. Disease in Ifnar 2/2 and CD11c Cre + Ifnar f/f mice also was facilitated by the proinflammatory cytokine TNF-a, as blocking antibodies diminished complement activation and prolonged survival without altering viral burden. Collectively, our findings establish the dominant role of type I IFN signaling in myeloid cells in restricting virus infection and controlling pathological inflammation and tissue injury.

Research paper thumbnail of A Temporal Role Of Type I Interferon Signaling in CD8+ T Cell Maturation during Acute West Nile Virus Infection

PLoS Pathogens, 2011

A genetic absence of the common IFN-a/b signaling receptor (IFNAR) in mice is associated with enh... more A genetic absence of the common IFN-a/b signaling receptor (IFNAR) in mice is associated with enhanced viral replication and altered adaptive immune responses. However, analysis of IFNAR-/mice is limited for studying the functions of type I IFN at discrete stages of viral infection. To define the temporal functions of type I IFN signaling in the context of infection by West Nile virus (WNV), we treated mice with MAR1-5A3, a neutralizing, non cell-depleting anti-IFNAR antibody. Inhibition of type I IFN signaling at or before day 2 after infection was associated with markedly enhanced viral burden, whereas treatment at day 4 had substantially less effect on WNV dissemination. While antibody treatment prior to infection resulted in massive expansion of virus-specific CD8 + T cells, blockade of type I IFN signaling starting at day 4 induced dysfunctional CD8 + T cells with depressed cytokine responses and expression of phenotypic markers suggesting exhaustion. Thus, only the later maturation phase of anti-WNV CD8 + T cell development requires type I IFN signaling. WNV infection experiments in BATF3-/mice, which lack CD8-a dendritic cells and have impaired priming due to inefficient antigen cross-presentation, revealed a similar effect of blocking IFN signaling on CD8 + T cell maturation. Collectively, our results suggest that cell nonautonomous type I IFN signaling shapes maturation of antiviral CD8 + T cell response at a stage distinct from the initial priming event.

Research paper thumbnail of Headache in intracerebral hematomas

Neurology, 1996

Objectives: We sought to describe the frequency and location of headache in intracerebral hematom... more Objectives: We sought to describe the frequency and location of headache in intracerebral hematoma (ICH) and to analyze its clinical and CT predictors by means of multivariate analysis. Background: Headache is more common in intracerebral hemorrhage than in ischemic stroke, and its frequency varies with hematoma location, but the pathophysiologic mechanisms of headache associated with ICH are not fully known. Methods: We examined a cohort of 289 patients with ICH during a 14-month period in a university hospital. Clinical, including the presence and location of headache, and CT features were collected by two neurologists. Results: One hundred and sixty-five (57%) patients with ICH had a headache at the onset of their stroke. Headache was more common in cerebellar and lobar hemorrhages than in deep ones (thalamic, caudate, capsuloputaminal, brainstem). Headache was also more common in women, patients younger than 70 years, those who vomited, and those with meningeal signs, a Glasgow ...

Research paper thumbnail of T cell immunodominance and maintenance of memory regulated by unexpectedly cross-reactive pathogens

Nature Immunology, 2002

We show here that T cell cross-reactivity between heterologous viruses influences the immunodomin... more We show here that T cell cross-reactivity between heterologous viruses influences the immunodominance of virus-specific CD8 + T cells by two mechanisms. First, T cells specific for cross-reactive epitopes dominate acute responses to viral infections; second, within the memory pool, T cells specific for cross-reactive epitopes are maintained while those specific for non-cross-reactive epitopes are selectively lost. These findings suggest an immunological paradigm in which viral infections shape the available T cell repertoire, causing alterations in the hierarchies of both the primary and memory CD8 + T cell responses elicited by subsequent viral infections. Thus, immunodominance is a function of the host's previous exposure to unrelated pathogens, and this may have an impact on protective immunity and immunopathology.

Research paper thumbnail of Effects of Acute and Chronic Murine Norovirus Infections on Immune Responses and Recovery from Friend Retrovirus Infection

Journal of Virology, 2009

Murine norovirus (MNV) is a highly infectious but generally nonpathogenic agent that is commonly ... more Murine norovirus (MNV) is a highly infectious but generally nonpathogenic agent that is commonly found in research mouse colonies in both North America and Europe. In the present study, the effects of acute and chronic infections with MNV on immune responses and recovery from concurrent Friend virus (FV) infections were investigated. No significant differences in T-cell or NK-cell responses, FV-neutralizing antibody responses, or long-term recovery from FV infection were observed. We conclude that concurrent MNV infections had no major impacts on FV infections.

Research paper thumbnail of CD8 + T Cells Use TRAIL To Restrict West Nile Virus Pathogenesis by Controlling Infection in Neurons

Journal of Virology, 2012

Previous studies of mice have demonstrated that an orchestrated sequence of innate and adaptive i... more Previous studies of mice have demonstrated that an orchestrated sequence of innate and adaptive immune responses is required to control West Nile virus (WNV) infection in peripheral and central nervous system (CNS) tissues. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; also known as CD253) has been reported to inhibit infection with dengue virus, a closely related flavivirus, in cell culture. To determine the physiological function of TRAIL in the context of flavivirus infection, we compared the pathogenesis of WNV in wild-type and TRAIL −/− mice. Mice lacking TRAIL showed increased vulnerability and death after subcutaneous WNV infection. Although no difference in viral burden was detected in peripheral tissues, greater viral infection was detected in the brain and spinal cord at late times after infection, and this was associated with delayed viral clearance in the few surviving TRAIL −/− mice. While priming of adaptive B and T cell responses and trafficking of i...

Research paper thumbnail of Pattern Recognition Receptor MDA5 Modulates CD8 + T Cell-Dependent Clearance of West Nile Virus from the Central Nervous System

Journal of Virology, 2013

Many viruses induce type I interferon responses by activating cytoplasmic RNA sensors, including ... more Many viruses induce type I interferon responses by activating cytoplasmic RNA sensors, including the RIG-I-like receptors (RLRs). Although two members of the RLR family, RIG-I and MDA5, have been implicated in host control of virus infection, the relative role of each RLR in restricting pathogenesis in vivo remains unclear. Recent studies have demonstrated that MAVS, the adaptor central to RLR signaling, is required to trigger innate immune defenses and program adaptive immune responses, which together restrict West Nile virus (WNV) infection in vivo . In this study, we examined the specific contribution of MDA5 in controlling WNV in animals. MDA5 −/− mice exhibited enhanced susceptibility, as characterized by reduced survival and elevated viral burden in the central nervous system (CNS) at late times after infection, even though small effects on systemic type I interferon response or viral replication were observed in peripheral tissues. Intracranial inoculation studies and infecti...

Research paper thumbnail of Beta Interferon Controls West Nile Virus Infection and Pathogenesis in Mice

Journal of Virology, 2011

Studies with mice lacking the common plasma membrane receptor for type I interferon ( IFN-αβR − /... more Studies with mice lacking the common plasma membrane receptor for type I interferon ( IFN-αβR − / − ) have revealed that IFN signaling restricts tropism, dissemination, and lethality after infection with West Nile virus (WNV) or several other pathogenic viruses. However, the specific functions of individual IFN subtypes remain uncertain. Here, using IFN-β − / − mice, we defined the antiviral and immunomodulatory function of this IFN subtype in restricting viral infection. IFN-β − / − mice were more vulnerable to WNV infection than wild-type mice, succumbing more quickly and with greater overall mortality, although the phenotype was less severe than that of IFN-αβR − / − mice. The increased susceptibility of IFN-β − / − mice was accompanied by enhanced viral replication in different tissues. Consistent with a direct role for IFN-β in control of WNV replication, viral titers in ex vivo cultures of macrophages, dendritic cells, fibroblasts, and cerebellar granule cell neurons, but not ...

Research paper thumbnail of Murine Norovirus Infection Has No Significant Effect on Adaptive Immunity to Vaccinia Virus or Influenza A Virus

Journal of Virology, 2009

Murine norovirus (MNV) is endemic in many research mouse colonies. Although MNV infections are ty... more Murine norovirus (MNV) is endemic in many research mouse colonies. Although MNV infections are typically asymptomatic in immunocompetent mice, the effects of MNV infection on subsequent experimental viral infections are poorly documented. Here, we infected C57BL/6 mice with MNV and then with either vaccinia virus or influenza A virus. MNV infection had no effect on CD8 + T-cell or antibody responses to secondary viruses or to secondary virus-induced morbidity or mortality. While our findings suggest that MNV has little influence on host immunity in immunocompetent mice, we would urge caution regarding the potential effects of MNV on immune responses to viruses and other pathogens, which must be determined on a system-by-system basis.

Research paper thumbnail of Seizures at the onset of subarachnoid haemorrhage

Journal of Neurology, 1996

In a prospective study of 253 patients with subarachnoid haemorrhage, 16 (6.3%) had seizures at t... more In a prospective study of 253 patients with subarachnoid haemorrhage, 16 (6.3%) had seizures at the onset of bleeding. None had a previous history of seizures. One was an alcoholic. None had metabolic imbalance. Hemiparesis, Hunt's grade > 3, the amount of subarachnoid blood and the presence of an aneurysm were significantly more frequent in patients with seizures at the onset of subarachnoid haemorrhage. Although rebleeding and mortality or severe disability at discharge were more frequent in these patients, seizures were not a significant predictor of prognosis. One of the survivors with early seizures developed recurrent epileptic seizures 1 year later.

Research paper thumbnail of Innate Immunity to Viruses: Control of Vaccinia Virus Infection by γδ T Cells

The Journal of Immunology, 2001

The existence of γδ T cells has been known for over 15 years, but their significance in innate im... more The existence of γδ T cells has been known for over 15 years, but their significance in innate immunity to virus infections has not been determined. We show here that γδ T cells are well suited to provide a rapid response to virus infection and demonstrate their role in innate resistance to vaccinia virus (VV) infection in both normal C57BL/6 and β TCR knockout (KO) mice. VV-infected mice deficient in γδ T cells had significantly higher VV titers early postinfection (PI) and increased mortality when compared with control mice. There was a rapid and profound VV-induced increase in IFN-γ-producing γδ T cells in the peritoneal cavity and spleen of VV-infected mice beginning as early as day 2 PI. This rapid response occurred in the absence of priming, as there was constitutively a significant frequency of VV-specific γδ T cells in the spleen in uninfected β TCR KO mice, as demonstrated by limiting dilution assay. Also, like NK cells, another mediator of innate immunity to viruses, γδ T ...

Research paper thumbnail of Viral Interference with Antigen Presentation Does Not Alter Acute or Chronic CD8 T Cell Immunodominance in Murine Cytomegalovirus Infection

The Journal of Immunology, 2007

Both human CMV and murine CMV (MCMV) elicit large CD8 T cell responses, despite the potent effect... more Both human CMV and murine CMV (MCMV) elicit large CD8 T cell responses, despite the potent effects of viral genes that interfere with the MHC class I (MHC I) pathway of Ag presentation. To investigate the impact of immune evasion on CD8 T cell priming, we infected mice with wild-type (wt) MCMV or a mutant lacking its MHC I immune evasion genes, Δm4+m6+m152 MCMV. In acute infection, the two viruses elicited a CD8 T cell response to 26 peptide epitopes that was virtually identical in total size, kinetics, and immunodominance hierarchy. This occurred despite results demonstrating that primary DCs are susceptible to the effects of MCMV’s MHC I immune evasion genes. Eight months later, responses to both wt and mutant MCMV displayed the same CD8 T cell “memory inflation” and altered immunodominance that characterize the transition to chronic MCMV infection in C57BL/6 mice. Taken together, these findings suggest either that cross-priming dominates over direct CD8 T cell priming in both acu...

Research paper thumbnail of Antigen-independent recruitment of CTL to pancreatic islets expressing an NKG2D ligand (44.38)

The Journal of Immunology

The mechanisms by which CTLs enter and are retained in non-lymphoid tissue are not well-character... more The mechanisms by which CTLs enter and are retained in non-lymphoid tissue are not well-characterized. Using a novel transgenic mouse expressing the NKG2D ligand RAE1ϵ in β-islet cells of the pancreas, we found RAE1 expression was sufficient to induce the recruitment of adoptively transferred CTLs to islets. This was dependent on NKG2D expression by the CTLs and independent of antigen recognition. While transgenic mice did not develop diabetes, RAE1 expression was sufficient to induce insulitis in older, unmanipulated transgenic mice that was enhanced by viral infection and pancreatic inflammation. Surprisingly, the recruitment of CTLs resulted in the subsequent recruitment of a large number of endogenous lymphocytes. These results demonstrate that the expression of NKG2D ligands in islets is sufficient to recruit CTLs and induce a significant insulitis.

Research paper thumbnail of The impact of type I interferon on the development of the adaptive immune response (67.14)

The Journal of Immunology

Determining the impact of type I interferon on immune responses using mice missing the common IFN... more Determining the impact of type I interferon on immune responses using mice missing the common IFN-α/β signaling receptor (IFNAR- /-) is limited to studying the functions of type I IFN at all stages of viral infection. To define the temporal functions of type I IFN signaling in the context of infection by West Nile virus (WNV), we treated mice with MAR1-5A3, a neutralizing, non cell-depleting anti-IFNAR antibody at later stages of infection. Inhibition of type I IFN signaling at or before day 2 after infection was associated with markedly enhanced viral burden, whereas treatment at day 4 altered WNV dissemination less dramatically. Blockade of type I IFN signaling starting at day 4 induced dysfunctional CD8+ T cells with depressed cytokine responses and expression of phenotypic markers suggesting exhaustion. The later maturation phase (days 4-8) of anti-WNV CD8+ T cell development requires type I IFN signaling. Collectively, our results suggest that cell non-autonomous type I IFN sig...

Research paper thumbnail of Interferon-λ restricts West Nile virus neuroinvasion by tightening the blood-brain barrier

Science translational medicine, Jan 22, 2015

Although interferon-λ [also known as type III interferon or interleukin-28 (IL-28)/IL-29] restric... more Although interferon-λ [also known as type III interferon or interleukin-28 (IL-28)/IL-29] restricts infection by several viruses, its inhibitory mechanism has remained uncertain. We used recombinant interferon-λ and mice lacking the interferon-λ receptor (IFNLR1) to evaluate the effect of interferon-λ on infection with West Nile virus, an encephalitic flavivirus. Cell culture studies in mouse keratinocytes and dendritic cells showed no direct antiviral effect of exogenous interferon-λ, even though expression of interferon-stimulated genes was induced. We observed no differences in West Nile virus burden between wild-type and Ifnlr1(-/-) mice in the draining lymph nodes, spleen, or blood. We detected increased West Nile virus infection in the brain and spinal cord of Ifnlr1(-/-) mice, yet this was not associated with a direct antiviral effect in mouse neurons. Instead, we observed an increase in blood-brain barrier permeability in Ifnlr1(-/-) mice. Treatment of mice with pegylated in...

Research paper thumbnail of Oropouche Virus Infection and Pathogenesis Are Restricted by MAVS, IRF-3, IRF-7, and Type I Interferon Signaling Pathways in Nonmyeloid Cells

Journal of Virology, 2015

Oropouche virus (OROV) is a member of the Orthobunyavirus genus in the Bunyaviridae family and a ... more Oropouche virus (OROV) is a member of the Orthobunyavirus genus in the Bunyaviridae family and a prominent cause of insect-transmitted viral disease in Central and South America. Despite its clinical relevance, little is known about OROV pathogenesis. To define the host defense pathways that control OROV infection and disease, we evaluated OROV pathogenesis and immune responses in primary cells and mice that were deficient in the RIG-I-like receptor signaling pathway (MDA5, RIG-I, or MAVS), downstream regulatory transcription factors (IRF-3 or IRF-7), beta interferon (IFN-β), or the receptor for type I IFN signaling (IFNAR). OROV replicated to higher levels in primary fibroblasts and dendritic cells lacking MAVS signaling, the transcription factors IRF-3 and IRF-7, or IFNAR than in wild-type (WT) cells. In mice, deletion of IFNAR, MAVS, or IRF-3 and IRF-7 resulted in uncontrolled OROV replication, hypercytokinemia, extensive liver damage, and death, whereas WT congenic animals faile...

Research paper thumbnail of Interferon regulatory factor 5-dependent immune responses in the draining lymph node protect against West Nile virus infection

Journal of virology, 2014

Upon activation of Toll-like and RIG-I-like receptor signaling pathways, the transcription factor... more Upon activation of Toll-like and RIG-I-like receptor signaling pathways, the transcription factor IRF5 translocates to the nucleus and induces antiviral immune programs. The recent discovery of a homozygous mutation in the immunoregulatory gene guanine exchange factor dedicator of cytokinesis 2 (Dock2mu/mu) in several Irf5-/- mouse colonies has complicated interpretation of immune functions previously ascribed to IRF5. To define the antiviral functions of IRF5 in vivo, we infected backcrossed Irf5-/-×Dock2wt/wt mice (here called Irf5-/- mice) and independently generated CMV-Cre Irf5fl/fl mice with West Nile virus (WNV), a pathogenic neurotropic flavivirus. Compared to congenic wild-type animals, Irf5-/- and CMV-Cre Irf5fl/fl mice were more vulnerable to WNV infection, and this phenotype was associated with increased infection in peripheral organs, which resulted in higher virus titers in the central nervous system. The loss of IRF5, however, was associated with only small difference...

Research paper thumbnail of c-Myc-induced transcription factor AP4 is required for host protection mediated by CD8+ T cells

Nature Immunology, 2014

Although c-Myc is essential to establish a metabolically active and proliferative state in T cell... more Although c-Myc is essential to establish a metabolically active and proliferative state in T cells after priming, its expression is transient. It remains unknown how T cell activation is maintained after c-Myc down-regulation. Here, we identify AP4 as the transcription factor that is induced by c-Myc and sustains activation of antigen-specific CD8 + T cells. Despite normal priming, AP4deficient CD8 + T cells fail to continue transcription of a broad range of c-Myc-dependent targets. Mice lacking AP4 specifically in CD8 + T cells showed enhanced susceptibility to West Nile virus infection. Genome-wide analysis suggests that many activation-induced metabolic genes are shared targets of c-Myc and AP4. Thus, AP4 maintains c-Myc-initiated cellular activation programs in CD8 + T cells to control microbial infections. Protective immunity by CD8 + T cells is critical for host defense against many pathogens that cause death or chronic infection. During an acute infection by a virus or intracellular bacterium, antigen (Ag)-specific CD8 + T cells are primed by signals through the T cell receptor (TCR), co-stimulatory molecules and cytokine receptors and undergo rapid expansion, effector differentiation, and memory cell formation 1, 2. In the priming phase, activated CD8 + T cells grow in size by increasing global gene transcription and protein translation and utilize aerobic glycolysis pathways to produce the energy and materials for biosynthesis prior to cell cycle entry 3, 4, 5, 6, 7. Previous studies established that the transcription factor (TF) c-Myc is essential for the initiation of the global cellular activation Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Research paper thumbnail of The lectin pathway of complement activation contributes to protection from West Nile virus infection

Virology, 2011

The function of the lectin pathway of complement activation in vivo against West Nile virus (WNV)... more The function of the lectin pathway of complement activation in vivo against West Nile virus (WNV) or many other pathogenic viruses has not been defined. Mice deficient in lectin pathway recognition molecules (mannose binding lectin-A (MBL-A) and mannose binding lectin-C (MBL-C)) or the effector enzyme mannanbinding lectin-associated serine protease-2 (MASP-2), were more vulnerable to WNV infection than wild type mice. Compared with studies of mice deficient in factors of the classical or alternative pathway, MBL-A −/− × MBL-C −/− or MASP-2 −/− mice showed a less severe course of WNV infection. Indeed, a deficiency in lectin pathway activation did not significantly affect the kinetics of viral spread to the central nervous system (CNS) nor did it profoundly alter generation of adaptive B and T cell immune responses. We conclude that MBLmediated recognition and lectin pathway activation have important yet subordinate functions in protecting against WNV infection and disease.

Research paper thumbnail of Hidden death gene in ‘flu

Trends in Microbiology, 2002

Influenza A virus (IAV) is a significant human pathogen that is responsible for millions of death... more Influenza A virus (IAV) is a significant human pathogen that is responsible for millions of deaths across the globe. Although sequenced >20 years ago, no new gene products had been discovered until recently. Now, Chen et al. [1xA novel influenza A virus mitochondrial protein that induces cell death. Chen, W. et al. Nat. Med. 2001; 7: 1306–1312Crossref | Scopus (635)See all References][1] have described a novel protein encoded by IAV.This new protein was identified as a novel 87-residue ORF while scanning alternative reading-frame peptides for antigenicity. After identifying the new ORF (PB1-F2), the group confirmed that the reading frame was both transcribed and translated in IAV-infected cells, indicating that PB1-F2 was a bona fide IAV gene product. Interestingly, PB1-F2 was found to localize in the mitochondria and, when expressed in IAV-infected cells, resulted in increased apoptotic cell death.Although an in vivo correlation has not yet been established, the authors hypothesize that PB1-F2-induced apoptosis might enhance viral dissemination and reduce immunological responses by directly killing innate immune cells such as monocytes and macrophages. The identification of this novel gene product could provide a greater understanding of how IAV might evade the host immune response.

Research paper thumbnail of Deficient IFN Signaling by Myeloid Cells Leads to MAVS-Dependent Virus-Induced Sepsis

PLoS Pathogens, 2014

The type I interferon (IFN) signaling response limits infection of many RNA and DNA viruses. To d... more The type I interferon (IFN) signaling response limits infection of many RNA and DNA viruses. To define key cell types that require type I IFN signaling to orchestrate immunity against West Nile virus (WNV), we infected mice with conditional deletions of the type I IFN receptor (IFNAR) gene. Deletion of the Ifnar gene in subsets of myeloid cells resulted in uncontrolled WNV replication, vasoactive cytokine production, sepsis, organ damage, and death that were remarkably similar to infection of Ifnar 2/2 mice completely lacking type I IFN signaling. In Mavs 2/2 6Ifnar 2/2 myeloid cells and mice lacking both Ifnar and the RIG-I-like receptor adaptor gene Mavs, cytokine production was muted despite high levels of WNV infection. Thus, in myeloid cells, viral infection triggers signaling through MAVS to induce proinflammatory cytokines that can result in sepsis and organ damage. Viral pathogenesis was caused in part by massive complement activation, as liver damage was minimized in animals lacking complement components C3 or factor B or treated with neutralizing anti-C5 antibodies. Disease in Ifnar 2/2 and CD11c Cre + Ifnar f/f mice also was facilitated by the proinflammatory cytokine TNF-a, as blocking antibodies diminished complement activation and prolonged survival without altering viral burden. Collectively, our findings establish the dominant role of type I IFN signaling in myeloid cells in restricting virus infection and controlling pathological inflammation and tissue injury.

Research paper thumbnail of A Temporal Role Of Type I Interferon Signaling in CD8+ T Cell Maturation during Acute West Nile Virus Infection

PLoS Pathogens, 2011

A genetic absence of the common IFN-a/b signaling receptor (IFNAR) in mice is associated with enh... more A genetic absence of the common IFN-a/b signaling receptor (IFNAR) in mice is associated with enhanced viral replication and altered adaptive immune responses. However, analysis of IFNAR-/mice is limited for studying the functions of type I IFN at discrete stages of viral infection. To define the temporal functions of type I IFN signaling in the context of infection by West Nile virus (WNV), we treated mice with MAR1-5A3, a neutralizing, non cell-depleting anti-IFNAR antibody. Inhibition of type I IFN signaling at or before day 2 after infection was associated with markedly enhanced viral burden, whereas treatment at day 4 had substantially less effect on WNV dissemination. While antibody treatment prior to infection resulted in massive expansion of virus-specific CD8 + T cells, blockade of type I IFN signaling starting at day 4 induced dysfunctional CD8 + T cells with depressed cytokine responses and expression of phenotypic markers suggesting exhaustion. Thus, only the later maturation phase of anti-WNV CD8 + T cell development requires type I IFN signaling. WNV infection experiments in BATF3-/mice, which lack CD8-a dendritic cells and have impaired priming due to inefficient antigen cross-presentation, revealed a similar effect of blocking IFN signaling on CD8 + T cell maturation. Collectively, our results suggest that cell nonautonomous type I IFN signaling shapes maturation of antiviral CD8 + T cell response at a stage distinct from the initial priming event.

Research paper thumbnail of Headache in intracerebral hematomas

Neurology, 1996

Objectives: We sought to describe the frequency and location of headache in intracerebral hematom... more Objectives: We sought to describe the frequency and location of headache in intracerebral hematoma (ICH) and to analyze its clinical and CT predictors by means of multivariate analysis. Background: Headache is more common in intracerebral hemorrhage than in ischemic stroke, and its frequency varies with hematoma location, but the pathophysiologic mechanisms of headache associated with ICH are not fully known. Methods: We examined a cohort of 289 patients with ICH during a 14-month period in a university hospital. Clinical, including the presence and location of headache, and CT features were collected by two neurologists. Results: One hundred and sixty-five (57%) patients with ICH had a headache at the onset of their stroke. Headache was more common in cerebellar and lobar hemorrhages than in deep ones (thalamic, caudate, capsuloputaminal, brainstem). Headache was also more common in women, patients younger than 70 years, those who vomited, and those with meningeal signs, a Glasgow ...

Research paper thumbnail of T cell immunodominance and maintenance of memory regulated by unexpectedly cross-reactive pathogens

Nature Immunology, 2002

We show here that T cell cross-reactivity between heterologous viruses influences the immunodomin... more We show here that T cell cross-reactivity between heterologous viruses influences the immunodominance of virus-specific CD8 + T cells by two mechanisms. First, T cells specific for cross-reactive epitopes dominate acute responses to viral infections; second, within the memory pool, T cells specific for cross-reactive epitopes are maintained while those specific for non-cross-reactive epitopes are selectively lost. These findings suggest an immunological paradigm in which viral infections shape the available T cell repertoire, causing alterations in the hierarchies of both the primary and memory CD8 + T cell responses elicited by subsequent viral infections. Thus, immunodominance is a function of the host's previous exposure to unrelated pathogens, and this may have an impact on protective immunity and immunopathology.

Research paper thumbnail of Effects of Acute and Chronic Murine Norovirus Infections on Immune Responses and Recovery from Friend Retrovirus Infection

Journal of Virology, 2009

Murine norovirus (MNV) is a highly infectious but generally nonpathogenic agent that is commonly ... more Murine norovirus (MNV) is a highly infectious but generally nonpathogenic agent that is commonly found in research mouse colonies in both North America and Europe. In the present study, the effects of acute and chronic infections with MNV on immune responses and recovery from concurrent Friend virus (FV) infections were investigated. No significant differences in T-cell or NK-cell responses, FV-neutralizing antibody responses, or long-term recovery from FV infection were observed. We conclude that concurrent MNV infections had no major impacts on FV infections.

Research paper thumbnail of CD8 + T Cells Use TRAIL To Restrict West Nile Virus Pathogenesis by Controlling Infection in Neurons

Journal of Virology, 2012

Previous studies of mice have demonstrated that an orchestrated sequence of innate and adaptive i... more Previous studies of mice have demonstrated that an orchestrated sequence of innate and adaptive immune responses is required to control West Nile virus (WNV) infection in peripheral and central nervous system (CNS) tissues. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; also known as CD253) has been reported to inhibit infection with dengue virus, a closely related flavivirus, in cell culture. To determine the physiological function of TRAIL in the context of flavivirus infection, we compared the pathogenesis of WNV in wild-type and TRAIL −/− mice. Mice lacking TRAIL showed increased vulnerability and death after subcutaneous WNV infection. Although no difference in viral burden was detected in peripheral tissues, greater viral infection was detected in the brain and spinal cord at late times after infection, and this was associated with delayed viral clearance in the few surviving TRAIL −/− mice. While priming of adaptive B and T cell responses and trafficking of i...

Research paper thumbnail of Pattern Recognition Receptor MDA5 Modulates CD8 + T Cell-Dependent Clearance of West Nile Virus from the Central Nervous System

Journal of Virology, 2013

Many viruses induce type I interferon responses by activating cytoplasmic RNA sensors, including ... more Many viruses induce type I interferon responses by activating cytoplasmic RNA sensors, including the RIG-I-like receptors (RLRs). Although two members of the RLR family, RIG-I and MDA5, have been implicated in host control of virus infection, the relative role of each RLR in restricting pathogenesis in vivo remains unclear. Recent studies have demonstrated that MAVS, the adaptor central to RLR signaling, is required to trigger innate immune defenses and program adaptive immune responses, which together restrict West Nile virus (WNV) infection in vivo . In this study, we examined the specific contribution of MDA5 in controlling WNV in animals. MDA5 −/− mice exhibited enhanced susceptibility, as characterized by reduced survival and elevated viral burden in the central nervous system (CNS) at late times after infection, even though small effects on systemic type I interferon response or viral replication were observed in peripheral tissues. Intracranial inoculation studies and infecti...

Research paper thumbnail of Beta Interferon Controls West Nile Virus Infection and Pathogenesis in Mice

Journal of Virology, 2011

Studies with mice lacking the common plasma membrane receptor for type I interferon ( IFN-αβR − /... more Studies with mice lacking the common plasma membrane receptor for type I interferon ( IFN-αβR − / − ) have revealed that IFN signaling restricts tropism, dissemination, and lethality after infection with West Nile virus (WNV) or several other pathogenic viruses. However, the specific functions of individual IFN subtypes remain uncertain. Here, using IFN-β − / − mice, we defined the antiviral and immunomodulatory function of this IFN subtype in restricting viral infection. IFN-β − / − mice were more vulnerable to WNV infection than wild-type mice, succumbing more quickly and with greater overall mortality, although the phenotype was less severe than that of IFN-αβR − / − mice. The increased susceptibility of IFN-β − / − mice was accompanied by enhanced viral replication in different tissues. Consistent with a direct role for IFN-β in control of WNV replication, viral titers in ex vivo cultures of macrophages, dendritic cells, fibroblasts, and cerebellar granule cell neurons, but not ...

Research paper thumbnail of Murine Norovirus Infection Has No Significant Effect on Adaptive Immunity to Vaccinia Virus or Influenza A Virus

Journal of Virology, 2009

Murine norovirus (MNV) is endemic in many research mouse colonies. Although MNV infections are ty... more Murine norovirus (MNV) is endemic in many research mouse colonies. Although MNV infections are typically asymptomatic in immunocompetent mice, the effects of MNV infection on subsequent experimental viral infections are poorly documented. Here, we infected C57BL/6 mice with MNV and then with either vaccinia virus or influenza A virus. MNV infection had no effect on CD8 + T-cell or antibody responses to secondary viruses or to secondary virus-induced morbidity or mortality. While our findings suggest that MNV has little influence on host immunity in immunocompetent mice, we would urge caution regarding the potential effects of MNV on immune responses to viruses and other pathogens, which must be determined on a system-by-system basis.

Research paper thumbnail of Seizures at the onset of subarachnoid haemorrhage

Journal of Neurology, 1996

In a prospective study of 253 patients with subarachnoid haemorrhage, 16 (6.3%) had seizures at t... more In a prospective study of 253 patients with subarachnoid haemorrhage, 16 (6.3%) had seizures at the onset of bleeding. None had a previous history of seizures. One was an alcoholic. None had metabolic imbalance. Hemiparesis, Hunt's grade > 3, the amount of subarachnoid blood and the presence of an aneurysm were significantly more frequent in patients with seizures at the onset of subarachnoid haemorrhage. Although rebleeding and mortality or severe disability at discharge were more frequent in these patients, seizures were not a significant predictor of prognosis. One of the survivors with early seizures developed recurrent epileptic seizures 1 year later.

Research paper thumbnail of Innate Immunity to Viruses: Control of Vaccinia Virus Infection by γδ T Cells

The Journal of Immunology, 2001

The existence of γδ T cells has been known for over 15 years, but their significance in innate im... more The existence of γδ T cells has been known for over 15 years, but their significance in innate immunity to virus infections has not been determined. We show here that γδ T cells are well suited to provide a rapid response to virus infection and demonstrate their role in innate resistance to vaccinia virus (VV) infection in both normal C57BL/6 and β TCR knockout (KO) mice. VV-infected mice deficient in γδ T cells had significantly higher VV titers early postinfection (PI) and increased mortality when compared with control mice. There was a rapid and profound VV-induced increase in IFN-γ-producing γδ T cells in the peritoneal cavity and spleen of VV-infected mice beginning as early as day 2 PI. This rapid response occurred in the absence of priming, as there was constitutively a significant frequency of VV-specific γδ T cells in the spleen in uninfected β TCR KO mice, as demonstrated by limiting dilution assay. Also, like NK cells, another mediator of innate immunity to viruses, γδ T ...

Research paper thumbnail of Viral Interference with Antigen Presentation Does Not Alter Acute or Chronic CD8 T Cell Immunodominance in Murine Cytomegalovirus Infection

The Journal of Immunology, 2007

Both human CMV and murine CMV (MCMV) elicit large CD8 T cell responses, despite the potent effect... more Both human CMV and murine CMV (MCMV) elicit large CD8 T cell responses, despite the potent effects of viral genes that interfere with the MHC class I (MHC I) pathway of Ag presentation. To investigate the impact of immune evasion on CD8 T cell priming, we infected mice with wild-type (wt) MCMV or a mutant lacking its MHC I immune evasion genes, Δm4+m6+m152 MCMV. In acute infection, the two viruses elicited a CD8 T cell response to 26 peptide epitopes that was virtually identical in total size, kinetics, and immunodominance hierarchy. This occurred despite results demonstrating that primary DCs are susceptible to the effects of MCMV’s MHC I immune evasion genes. Eight months later, responses to both wt and mutant MCMV displayed the same CD8 T cell “memory inflation” and altered immunodominance that characterize the transition to chronic MCMV infection in C57BL/6 mice. Taken together, these findings suggest either that cross-priming dominates over direct CD8 T cell priming in both acu...