Dendritic cells and macrophages are productively infected by poliovirus

Poliovirus capsid protein VP3 can penetrate vascular endothelial cells

The poliovirus (PV) enters the central nervous system (CNS) via the bloodstream, suggesting the existence of a mechanism to cross the blood-brain barrier. Here, we report that PV capsid proteins (VP1 and VP3) can penetrate cells, with VP3 being more invasive. Two independent parts of VP3 are responsible for this function. Both peptides can penetrate human umbilical cord vascular endothelial cells, and one peptide of VP3 could also penetrate peripheral blood mononuclear cells. In an in vitro blood-brain barrier model using rat-derived astrocytes, pericytes, and endothelial cells, both peptides were observed to traverse from the blood side to the brain side at 6 h after administration. These results provide insights into the molecular mechanisms underlying PV invasion into the CNS.

Jagged2 targeting in lung cancer activates anti-tumor immunity via Notch-induced functional reprogramming of tumor-associated macrophages

Signaling through Notch receptors intrinsically regulates tumor cell development and growth. Here, we studied the role of the Notch ligand Jagged2 on immune evasion in non-small cell lung cancer (NSCLC). Higher expression of JAG2 in NSCLC negatively correlated with survival. In NSCLC pre-clinical models, deletion of Jag2, but not Jag1, in cancer cells attenuated tumor growth and activated protective anti-tumor T cell responses. Jag2-/- lung tumors exhibited higher frequencies of macrophages that expressed immunostimulatory mediators and triggered T cell-dependent anti-tumor immunity. Mechanistically, Jag2 ablation promoted Nr4a-mediated induction of Notch ligands DLL1/4 on cancer cells. DLL1/4-initiated Notch1/2 signaling in macrophages induced the expression of transcription factor IRF4 and macrophage immunostimulatory functionality. IRF4 expression was required for the anti-tumor effects of Jag2 deletion in lung tumors. Antibody targeting of Jagged2 inhibited tumor growth and activated IRF4-driven macrophage-mediated anti-tumor immunity. Thus, Jagged2 orchestrates immunosuppressive systems in NSCLC that can be overcome to incite macrophage-mediated anti-tumor immunity.

Immunomodulatory properties of Bacillus subtilis extracellular vesicles on rainbow trout intestinal cells and splenic leukocytes

Extracellular vesicles (EVs) are cell-derived membrane-surrounded vesicles that carry bioactive molecules. Among EVs, outer membrane vesicles (OMVs), specifically produced by Gram-negative bacteria, have been extensively characterized and their potential as vaccines, adjuvants or immunotherapeutic agents, broadly explored in mammals. Nonetheless, Gram-positive bacteria can also produce bilayered spherical structures from 20 to 400 nm involved in pathogenesis, antibiotic resistance, nutrient uptake and nucleic acid transfer. However, information regarding their immunomodulatory potential is very scarce, both in mammals and fish. In the current study, we have produced EVs from the Gram-positive probiotic Bacillus subtilis and evaluated their immunomodulatory capacities using a rainbow trout intestinal epithelial cell line (RTgutGC) and splenic leukocytes. B. subtilis EVs significantly up-regulated the transcription of several pro-inflammatory and antimicrobial genes in both RTgutGC cells and splenocytes, while also up-regulating many genes associated with B cell differentiation in the later. In concordance, B. subtilis EVs increased the number of IgM-secreting cells in splenocyte cultures, while at the same time increased the MHC II surface levels and antigen-processing capacities of splenic IgM+ B cells. Interestingly, some of these experiments were repeated comparing the effects of B. subtilis EVs to EVs obtained from another Bacillus species, Bacillus megaterium, identifying important differences. The data presented provides evidence of the immunomodulatory capacities of Gram-positive EVs, pointing to the potential of B. subtilis EVs as adjuvants or immunostimulants for aquaculture.

Human B cells and dendritic cells are susceptible and permissive to enterovirus D68 infection

Enterovirus D68 (EV-D68) is predominantly associated with mild respiratory infections, but can also cause severe respiratory disease and extra-respiratory complications, including acute flaccid myelitis. Systemic dissemination of EV-D68 is crucial for the development of extra-respiratory diseases, but it is currently unclear how EV-D68 spreads systemically (viremia). We hypothesize that immune cells contribute to the systemic dissemination of EV-D68, as this is a mechanism commonly used by other enteroviruses. Therefore, we investigated the susceptibility and permissiveness of human primary immune cells for different EV-D68 isolates. In human peripheral blood mononuclear cells inoculated with EV-D68, only B cells were susceptible but virus replication was limited. However, in B cell-rich cultures, such as Epstein-Barr virus-transformed B-lymphoblastoid cell line (BLCL) and primary lentivirus-transduced B cells, which better represent lymphoid B cells, were productively infected. Subsequently, we showed that dendritic cells (DCs), particularly immature DCs, are susceptible and permissive for EV-D68 infection and that they can spread EV-D68 to autologous BLCL. Altogether, our findings suggest that immune cells, especially B cells and DCs, could play an important role in the pathogenesis of EV-D68 infection. Infection of these cells may contribute to systemic dissemination of EV-D68, which is an essential step toward the development of extra-respiratory complications.IMPORTANCEEnterovirus D68 (EV-D68) is an emerging respiratory virus that has caused outbreaks worldwide since 2014. EV-D68 infects primarily respiratory epithelial cells resulting in mild respiratory diseases. However, EV-D68 infection is also associated with extra-respiratory complications, including polio-like paralysis. It is unclear how EV-D68 spreads systemically and infects other organs. We hypothesized that immune cells could play a role in the extra-respiratory spread of EV-D68. We showed that EV-D68 can infect and replicate in specific immune cells, that is, B cells and dendritic cells (DCs), and that virus could be transferred from DCs to B cells. Our data reveal a potential role of immune cells in the pathogenesis of EV-D68 infection. Intervention strategies that prevent EV-D68 infection of immune cells will therefore potentially prevent systemic spread of virus and thereby severe extra-respiratory complications.

Early enterovirus translation deficits extend viral RNA replication and elicit sustained MDA5-directed innate signaling

IMPORTANCE

Multiple pattern recognition receptors sense vRNAs and initiate downstream innate signaling: endosomal Toll-like receptors (TLRs) 3, 7, and 8 and cytoplasmic RIG-I-like receptors (RLRs) RIG-I, and MDA5. They engage distinct signaling scaffolds: mitochondrial antiviral signaling protein (RLR), MyD88, and TLR-adaptor interacting with SLC15A4 on the lysosome (TLR7 and TLR8) and toll/IL-1R domain-containing adaptor inducing IFN (TLR3). By virtue of their unusual vRNA structure and direct host cell entry path, the innate response to EVs uniquely is orchestrated by MDA5. We reported that PVSRIPO's profound attenuation and loss of cytopathogenicity triggers MDA5-directed polar TBK1-IRF3 signaling that generates priming of polyfunctional antitumor CD8+ T-cell responses and durable antitumor surveillance in vivo. Here we unraveled EV-host relations that control suppression of host type-I IFN responses and show that PVSRIPO's deficient immediate host eIF4G cleavage generates unopposed MDA5-directed downstream signaling cascades resulting in sustained type-I IFN release.

In vitro and in vivo models for the study of EV-D68 infection

Enterovirus D68 (EV-D68) is one of hundreds of non-polio enteroviruses that typically cause cold-like respiratory illness. The first EV-D68 outbreak in the United States in 2014 aroused widespread concern among the public and health authorities. The infection was found to be associated with increased surveillance of acute flaccid myelitis, a neurological condition that causes limb paralysis in conjunction with spinal cord inflammation. In vitro studies utilising two-dimensional (2D) and three-dimensional (3D) culture systems have been employed to elucidate the pathogenic mechanism of EV-D68. Various animal models have also been developed to investigate viral tropism and distribution, pathogenesis, and immune responses during EV-D68 infection. EV-D68 infections have primarily been investigated in respiratory, intestinal and neural cell lines/tissues, as well as in small-size immunocompetent rodent models that were limited to a young age. Some studies have implemented strategies to overcome the barriers by using immunodeficient mice or virus adaptation. Although the existing models may not fully recapitulate both respiratory and neurological disease observed in human EV-D68 infection, they have been valuable for studying pathogenesis and evaluating potential vaccine or therapeutic candidates. In this review, we summarise the methodologies and findings from each experimental model and discuss their applications and limitations.

pH-gated nanoparticles selectively regulate lysosomal function of tumour-associated macrophages for cancer immunotherapy

Tumour-associated macrophages (TAMs), as one of the most abundant tumour-infiltrating immune cells, play a pivotal role in tumour antigen clearance and immune suppression. M2-like TAMs present a heightened lysosomal acidity and protease activity, limiting an effective antigen cross-presentation. How to selectively reprogram M2-like TAMs to reinvigorate anti-tumour immune responses is challenging. Here, we report a pH-gated nanoadjuvant (PGN) that selectively targets the lysosomes of M2-like TAMs in tumours rather than the corresponding organelles from macrophages in healthy tissues. Enabled by the PGN nanotechnology, M2-like TAMs are specifically switched to a M1-like phenotype with attenuated lysosomal acidity and cathepsin activity for improved antigen cross-presentation, thus eliciting adaptive immune response and sustained tumour regression in tumour-bearing female mice. Our findings provide insights into how to specifically regulate lysosomal function of TAMs for efficient cancer immunotherapy.

Polio virotherapy targets the malignant glioma myeloid infiltrate with diffuse microglia activation engulfing the CNS

BACKGROUND

Malignant gliomas commandeer dense inflammatory infiltrates with glioma-associated macrophages and microglia (GAMM) promoting immune suppression, evasion, and tumor progression. Like all cells in the mononuclear phagocytic system, GAMM constitutively express the poliovirus receptor, CD155. Besides myeloid cells, CD155 is widely upregulated in the neoplastic compartment of malignant gliomas. Intratumor treatment with the highly attenuated rhino:poliovirus chimera, PVSRIPO, yielded long-term survival with durable radiographic responses in patients with recurrent glioblastoma (Desjardins et al. New England Journal of Medicine, 2018). This scenario raises questions about the contributions of myeloid versus neoplastic cells to polio virotherapy of malignant gliomas.

METHODS

We investigated PVSRIPO immunotherapy in immunocompetent mouse brain tumor models with blinded, board-certified neuropathologist review, a range of neuropathological, immunohistochemical, and immunofluorescence analyses, and RNAseq of the tumor region.

RESULTS

PVSRIPO treatment caused intense engagement of the GAMM infiltrate associated with substantial, but transient tumor regression. This was accompanied by marked microglia activation and proliferation in normal brain surrounding the tumor, in the ipsilateral hemisphere and extending into the contralateral hemisphere. There was no evidence for lytic infection of malignant cells. PVSRIPO-instigated microglia activation occurred against a backdrop of sustained innate antiviral inflammation, associated with induction of the Programmed Cell Death Ligand 1 (PD-L1) immune checkpoint on GAMM. Combining PVSRIPO with PD1/PD-L1 blockade led to durable remissions.

CONCLUSIONS

Our work implicates GAMM as active drivers of PVSRIPO-induced antitumor inflammation and reveals profound and widespread neuroinflammatory activation of the brain-resident myeloid compartment by PVSRIPO.

Plant-made poliovirus vaccines - Safe alternatives for global vaccination

Human polioviruses are highly infectious viruses that are spread mainly through the fecal-oral route. Infection of the central nervous system frequently results in irreversible paralysis, a disease called poliomyelitis. Children under five years are mainly affected if they have not acquired immunity through natural infection or via vaccination. Current polio vaccines comprise the injectable inactivated polio vaccine (IPV, also called the Salk vaccine) and the live-attenuated oral polio vaccine (OPV, also called the Sabin vaccine). The main limitations of the IPV are the reduced protection at the intestinal mucosa, the site of virus replication, and the high costs for manufacturing due to use of live viruses. While the OPV is more effective and stimulates mucosal immunity, it is manufactured using live-attenuated strains that can revert into pathogenic viruses resulting in major safety concerns and vaccine-derived outbreaks. During the last fifteen years, plant-based poliovirus vaccines have been explored by several groups as a safe and low-cost alternative, and promising results in protection against challenges with viruses and induction of neutralizing antibodies have been obtained. However, low yields and a high frequency in dose administration highlight the need for improvements in polioviral antigen production. In this review, we provide insights into recent efforts to develop plant-made poliovirus candidates, with an emphasis on strategies to optimize the production of viral antigens.

GATA1 controls numbers of hematopoietic progenitors and their response to autoimmune neuroinflammation

GATA-binding factor 1 (GATA1) is a transcription factor that governs the development and function of multiple hematopoietic cell lineages. GATA1 is expressed in hematopoietic stem and progenitor cells (HSPCs) and is essential for erythroid lineage commitment; however, whether it plays a role in hematopoietic stem cell (HSC) biology and the development of myeloid cells, and what that role might be, remains unclear. We initially set out to test the role of eosinophils in experimental autoimmune encephalomyelitis (EAE), a model of central nervous system autoimmunity, using mice lacking a double GATA-site (ΔdblGATA), which lacks eosinophils due to the deletion of the dblGATA enhancer to Gata1, which alters its expression. ΔdblGATA mice were resistant to EAE, but not because of a lack of eosinophils, suggesting that these mice have an additional defect. ΔdblGATA mice with EAE had fewer inflammatory myeloid cells than the control mice, suggesting that resistance to EAE is caused by a defect in myeloid cells. Naïve ΔdblGATA mice also showed reduced frequency of CD11b+ myeloid cells in the blood, indicating a defect in myeloid cell production. Examination of HSPCs revealed fewer HSCs and myeloid cell progenitors in the ΔdblGATA bone marrow (BM), and competitive BM chimera experiments showed a reduced capacity of the ΔdblGATA BM to reconstitute immune cells, suggesting that reduced numbers of ΔdblGATA HSPCs cause a functional deficit during inflammation. Taken together, our data show that GATA1 regulates the number of HSPCs and that reduced GATA1 expression due to dblGATA deletion results in a diminished immune response following the inflammatory challenge.

HIV-1-Infected CD4+ T Cells Present MHC Class II-Restricted Epitope via Endogenous Processing

HIV-1-specific CD4⁺ T cells (T_CD4+s) play a critical role in controlling HIV-1 infection. Canonically, T_CD4+s are activated by peptides derived from extracellular ("exogenous") Ags displayed in complex with MHC class II (MHC II) molecules on the surfaces of "professional" APCs such as dendritic cells (DCs). In contrast, activated human T_CD4+s, which express MHC II, are not typically considered for their APC potential because of their low endocytic capacity and the exogenous Ag systems historically used for assessment. Using primary T_CD4+s and monocyte-derived DCs from healthy donors, we show that activated human T_CD4+s are highly effective at MHC II-restricted presentation of an immunodominant HIV-1-derived epitope postinfection and subsequent noncanonical processing and presentation of endogenously produced Ag. Our results indicate that, in addition to marshalling HIV-1-specific immune responses during infection, T_CD4+s also act as APCs, leading to the activation of HIV-1-specific T_CD4+s.

PKR Binds Enterovirus IRESs, Displaces Host Translation Factors, and Impairs Viral Translation to Enable Innate Antiviral Signaling

For RNA virus families except Picornaviridae, viral RNA sensing includes Toll-like receptors and/or RIG-I. Picornavirus RNAs, whose 5' termini are shielded by a genome-linked protein, are predominately recognized by MDA5. This has important ramifications for adaptive immunity, as MDA5-specific patterns of type-I interferon (IFN) release are optimal for CD4+T cell TH1 polarization and CD8+T cell priming. We are exploiting this principle for cancer immunotherapy with recombinant poliovirus (PV), PVSRIPO, the type 1 (Sabin) PV vaccine containing a rhinovirus type 2 internal ribosomal entry site (IRES). Here we show that PVSRIPO-elicited MDA5 signaling is preceded by early sensing of the IRES by the double-stranded (ds)RNA-activated protein kinase (PKR). PKR binding to IRES stem-loop domains 5-6 led to dimerization and autoactivation, displaced host translation initiation factors, and suppressed viral protein synthesis. Early PKR-mediated antiviral responses tempered incipient viral translation and the activity of cytopathogenic viral proteinases, setting up accentuated MDA5 innate inflammation in response to PVSRIPO infection. IMPORTANCE Among the RIG-I-like pattern recognition receptors, MDA5 stands out because it senses long dsRNA duplexes independent of their 5' features (RIG-I recognizes viral [v]RNA 5'-ppp blunt ends). Uniquely among RNA viruses, the innate defense against picornaviruses is controlled by MDA5. We show that prior to engaging MDA5, recombinant PV RNA is sensed upon PKR binding to the viral IRES at a site that overlaps with the footprint for host translation factors mediating 40S subunit recruitment. Our study demonstrates that innate antiviral type-I IFN responses orchestrated by MDA5 involve separate innate modules that recognize distinct vRNA features and interfere with viral functions at multiple levels.

Enteroviruses and Type 1 Diabetes: Multiple Mechanisms and Factors?

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by insulin deficiency and resultant hyperglycemia. Complex interactions of genetic and environmental factors trigger the onset of autoimmune mechanisms responsible for development of autoimmunity to β cell antigens and subsequent development of T1D. A potential role of virus infections has long been hypothesized, and growing evidence continues to implicate enteroviruses as the most probable triggering viruses. Recent studies have strengthened the association between enteroviruses and development of autoimmunity in T1D patients, potentially through persistent infections. Enterovirus infections may contribute to different stages of disease development. We review data from both human cohort studies and experimental research exploring the potential roles and molecular mechanisms by which enterovirus infections can impact disease outcome.

Enteroviruses and Type 1 Diabetes: Multiple Mechanisms and Factors?

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by insulin deficiency and resultant hyperglycemia. Complex interactions of genetic and environmental factors trigger the onset of autoimmune mechanisms responsible for development of autoimmunity to β cell antigens and subsequent development of T1D. A potential role of virus infections has long been hypothesized, and growing evidence continues to implicate enteroviruses as the most probable triggering viruses. Recent studies have strengthened the association between enteroviruses and development of autoimmunity in T1D patients, potentially through persistent infections. Enterovirus infections may contribute to different stages of disease development. We review data from both human cohort studies and experimental research exploring the potential roles and molecular mechanisms by which enterovirus infections can impact disease outcome.

Inhibition of IRGM establishes a robust antiviral immune state to restrict pathogenic viruses

The type I interferon (IFN) response is the major host arsenal against invading viruses. IRGM is a negative regulator of IFN responses under basal conditions. However, the role of human IRGM during viral infection has remained unclear. In this study, we show that IRGM expression is increased upon viral infection. IFN responses induced by viral PAMPs are negatively regulated by IRGM. Conversely, IRGM depletion results in a robust induction of key viral restriction factors including IFITMs, APOBECs, SAMHD1, tetherin, viperin, and HERC5/6. Additionally, antiviral processes such as MHC‐I antigen presentation and stress granule signaling are enhanced in IRGM‐deficient cells, indicating a robust cell‐intrinsic antiviral immune state. Consistently, IRGM‐depleted cells are resistant to the infection with seven viruses from five different families, including Togaviridae, Herpesviridae, Flaviviverdae, Rhabdoviridae, and Coronaviridae. Moreover, we show that Irgm1 knockout mice are highly resistant to chikungunya virus (CHIKV) infection. Altogether, our work highlights IRGM as a broad therapeutic target to promote defense against a large number of human viruses, including SARS‐CoV‐2, CHIKV, and Zika virus.

Essential role of autophagy in restricting poliovirus infection revealed by identification of an ATG7 defect in a poliomyelitis patient

Paralytic poliomyelitis is a rare disease manifestation following poliovirus (PV) infection. The disease determinants remain largely unknown. We used whole exome sequencing to uncover possible contributions of host genetics to the development of disease outcome in humans with poliomyelitis. We identified a patient with a variant in ATG7, an important regulatory gene in the macroautophagy/autophagy pathway. PV infection did not induce a prominent type I interferon response, but rather activated autophagy in neuronal-like cells, and this was essential for viral control. Importantly, virus-induced autophagy was impaired in patient fibroblasts and associated with increased viral burden and enhanced cell death following infection. Lack of ATG7 prevented control of infection in neuronal-like cells, and reconstitution of patient cells with wild-type ATG7 reestablished autophagy-mediated control of infection. Collectively, these data suggest that ATG7 defect contributes to host susceptibility to PV infection and propose autophagy as an unappreciated antiviral effector in viral infection in humans.

The role of picornavirus infection in epileptogenesis

Picornaviridae are a family of small positive-strand RNA viruses, and transmitted via the respiratory or fecal-oral route. The neurotropic picornaviruses can induce acute or late recurrent seizures following central nervous system infection, by infecting the peripheral nerve, crossing the blood-brain barrier and migrating in the Trojan-horse method. Theiler’s murine encephalomyelitis virus (TMEV), as a member of Picornaviridae family, can cause encephalitis, leading to chronic spontaneous seizures. TMEV-infected C57BL/6 mice have been used as an animal model for exploring the mechanism of epileptogenesis and assessing new antiepileptic drugs. Astrogliosis, neuronal death and microglial recruitment have been detected in the hippocampus following the picornaviruse-induced encephalitis. The macrophages, monocytes, neutrophils, as well as IL-6 and TNF-α released by them, play an important role in the epileptogenesis. In this review, we summarize the clinical characteristics of picornavirus infection, and the immunopathology involved in the TMEV-induced epilepsy.

Enterovirus D68 molecular and cellular biology and pathogenesis

In recent years, enterovirus D68 (EV-D68) has advanced from a rarely detected respiratory virus to a widespread pathogen responsible for increasing rates of severe respiratory illness and acute flaccid myelitis (AFM) in children worldwide. In this review, we discuss the accumulating data on the molecular features of EV-D68 and place these into the context of enterovirus biology in general. We highlight similarities and differences with other enteroviruses and genetic divergence from own historical prototype strains of EV-D68. These include changes in capsid antigens, host cell receptor usage, and viral RNA metabolism collectively leading to increased virulence. Furthermore, we discuss the impact of EV-D68 infection on the biology of its host cells, and how these changes are hypothesized to contribute to motor neuron toxicity in AFM. We highlight areas in need of further research, including the identification of its primary receptor and an understanding of the pathogenic cascade leading to motor neuron injury in AFM. Finally, we discuss the epidemiology of the EV-D68 and potential therapeutic approaches.

Harnessing virus tropism for dendritic cells for vaccine design

Dendritic cells (DCs) are pivotal stimulators of T cell responses. They provide essential signals (epitope presentation, proinflammatory cytokines, co-stimulation) to T cells and prime adaptive immunity. Therefore, they are paramount to immunization strategies geared to generate T cell immunity. The inflammatory signals DCs respond to, classically occur in the context of acute virus infection. Yet, enlisting viruses for engaging DCs is hampered by their penchant for targeting DCs with sophisticated immune evasive and suppressive ploys. In this review, we discuss our work on devising vectors based on a recombinant polio:rhinovirus chimera for effectively targeting and engaging DCs. We are juxtaposing this approach with commonly used, recently studied dsDNA virus vector platforms.

Genetically stable poliovirus vectors activate dendritic cells and prime antitumor CD8 T cell immunity

Viruses naturally engage innate immunity, induce antigen presentation, and mediate CD8 T cell priming against foreign antigens. Polioviruses can provide a context optimal for generating antigen-specific CD8 T cells, as they have natural tropism for dendritic cells, preeminent inducers of CD8 T cell immunity; elicit Th1-promoting inflammation; and lack interference with innate or adaptive immunity. However, notorious genetic instability and underlying neuropathogenicity has hampered poliovirus-based vector applications. Here we devised a strategy based on the polio:rhinovirus chimera PVSRIPO, devoid of viral neuropathogenicity after intracerebral inoculation in human subjects, for stable expression of exogenous antigens. PVSRIPO vectors infect, activate, and induce epitope presentation in DCs in vitro; they recruit and activate DCs with Th1-dominant cytokine profiles at the injection site in vivo. They efficiently prime tumor antigen-specific CD8 T cells in vivo, induce CD8 T cell migration to the tumor site, delay tumor growth and enhance survival in murine tumor models.

Experimental PVSRIPO oncolytic virus therapy of glioblastoma has shown long-term efficacy in a subset of patients. Here the authors engineer the virus to enable incorporation of tumor-specific antigens, and show proof-of-principle evidence that this modification increases anti-tumor immunity and extends survival in mice.

Recombinant Poliovirus for Cancer Immunotherapy

Mechanisms to elicit antiviral immunity, a natural host response to viral pathogen challenge, are of eminent relevance to cancer immunotherapy. "Oncolytic" viruses, naturally existing or genetically engineered viral agents with cell type-specific propagation in malignant cells, were ostensibly conceived for their tumor cytotoxic properties. Yet, their true therapeutic value may rest in their ability to provoke antiviral signals that engage antitumor immune responses within the immunosuppressive tumor microenvironment. Coopting oncolytic viral agents to instigate antitumor immunity is not an easy feat. In the course of coevolution with their hosts, viruses have acquired sophisticated strategies to block inflammatory signals, intercept innate antiviral interferon responses, and prevent antiviral effector responses, e.g., by interfering with antigen presentation and T cell costimulation. The resulting struggle of host innate inflammatory and antiviral responses versus viral immune evasion and suppression determines the potential for antitumor immunity to occur. Moreover, paradigms of early host:virus interaction established in normal immunocompetent organisms may not hold in the profoundly immunosuppressive tumor microenvironment. In this review, we explain the mechanisms of recombinant nonpathogenic poliovirus, PVSRIPO, which is currently in phase I clinical trials against recurrent glioblastoma. We focus on an unusual host:virus relationship defined by the simple and cytotoxic replication strategy of poliovirus, which generates inflammatory perturbations conducive to tumor antigen-specific immune priming.

Identification of genes and pathways in human antigen-presenting cell subsets in response to polio vaccine by bioinformatical analysis

BACKGROUND

Polio eradication has been achieved in the world except for three countries due to the widespread use of the inactivated poliovirus vaccine (IPV) and the live-attenuated oral poliovirus vaccine. Following polio eradication, the IPV would be the only polio vaccine available. However, the mechanisms of the interactions between IPV and human antigen-presenting cells (APCs) remain largely unclear.

METHODS

To investigate the involvement of the IPV in human monocytes, we downloaded the gene chip GSE44721 from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified using the GEO2R analysis tool. Functional and pathway enrichment analyses were performed for DEGs using the Metascape database. DEG-associated protein-protein-interactions (PPIs) were established by the Search Tool for the Retrieval of Interacting Genes website and visualized by Cytoscape.

RESULTS

There were 240 DEGs (51 upregulated and 189 downregulated genes) identified from the GSE44721 data set, and they were significantly enriched in several biological processes, including antigen processing and presentation of lipid antigen via MHC class Ib, adaptive immune response, and response to interferon-gamma. One hundred thirty-six nodes were screened from the DEG PPI network. There were six significant hub proteins (WDR36, MRTO4, RPF2, PPAN, CD40, and BMS1) that regulated the IPV in human monocytes.

CONCLUSIONS

In summary, using bioinformatical analysis, we have information for the immunization activated by the IPV in monocytes. Moreover, hormones and cytokines regulate the activation of APCs.

Host Genetics, Innate Immune Responses, and Cellular Death Pathways in Poliomyelitis Patients

Purpose

Poliovirus (PV) is one of the most studied viruses. Despite efforts to understand PV infection within the host, fundamental questions remain unanswered. These include the mechanisms determining the progression to viremia, the pathogenesis of neuronal infection and paralysis in only a minority of patients. Because of the rare disease phenotype of paralytic poliomyelitis (PPM), we hypothesize that a genetic etiology may contribute to the disease course and outcome.

Methods

We used whole-exome sequencing (WES) to investigate the genetic profile of 18 patients with PPM. Functional analyses were performed on peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages (MdMs).

Results

We identified rare variants in host genes involved in interferon signaling, viral replication, apoptosis, and autophagy. Upon PV infection of MdMs, we observed a tendency toward increased viral burden in patients compared to controls, suggesting reduced control of PV infection. In MdMs from patients, the IFNβ response correlated with the viral burden.

Conclusion

We suggest that genetic variants in innate immune defenses and cell death pathways contribute to the clinical presentation of PV infection. Importantly, this study is the first to uncover the genetic profile in patients with PPM combined with investigations of immune responses and viral burden in primary cells.

Ebola Virus Disease in Humans: Pathophysiology and Immunity

Viruses of the Ebolavirus genus cause sporadic epidemics of severe and systemic febrile disease that are fueled by human-to-human transmission. Despite the notoriety of ebolaviruses, particularly Ebola virus (EBOV), as prominent viral hemorrhagic fever agents, and the international concern regarding Ebola virus disease (EVD) outbreaks, very little is known about the pathophysiology of EVD in humans and, in particular, about the human immune correlates of survival and immune memory. This lack of basic knowledge about physiological characteristics of EVD is probably attributable to the dearth of clinical and laboratory data gathered from past outbreaks. The unprecedented magnitude of the EVD epidemic that occurred in West Africa from 2013 to 2016 has allowed, for the first time, evaluation of clinical, epidemiological, and immunological parameters in a significant number of patients using state-of-the-art laboratory equipment. This review will summarize the data from the literature regarding human pathophysiologic and immunologic responses to filoviral infection.

Regulation of IgM+ B Cell Activities by Rainbow Trout APRIL Reveals Specific Effects of This Cytokine in Lower Vertebrates

Tumor necrosis factor ligand superfamily members such as B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) have been identified in mammals as key regulators of B cell homeostasis and activation. However, the immune functions of APRIL are not as well defined as those of BAFF. Furthermore, while BAFF is present in all vertebrates, APRIL is missing in some animal groups, suggesting that BAFF has compensated the functions of APRIL in these species. In this context, we thought of great interest to explore the effects of APRIL on teleost B cells, given that APRIL appears for the first time in evolution in bony fish. Thus, in this study, we have performed an extensive analysis of the effect of APRIL on B cells using rainbow trout (Oncorhynchus mykiss) as a model species. Our results demonstrate that APRIL induces a specific proliferation of IgM⁺ B cells by itself and increases IgM secretion without promoting a terminal differentiation to plasma cells. APRIL also increased the levels of surface MHC II and augmented the capacity of these cells to process antigen, effects that were exclusively exerted on IgM⁺ B cells. Although our results point to a highly conserved role of APRIL on B cell homeostasis and activation throughout evolution, some specific differential effects have been observed in fish in comparison to the effects of APRIL previously described in mammals. Finally, the effects that APRIL induces on rainbow trout IgM⁺ B cells described in this paper have been compared with those previously reported in response to BAFF.

Cancer immunotherapy with recombinant poliovirus induces IFN-dominant activation of dendritic cells and tumor antigen-specific CTLs

Tumors thrive in an immunosuppressive microenvironment that impedes antitumor innate and adaptive immune responses. Thus, approaches that can overcome immunosuppression and engage antitumor immunity are needed. This study defines the adjuvant and cancer immunotherapy potential of the recombinant poliovirus/rhinovirus chimera PVSRIPO. PVSRIPO is currently in clinical trials against recurrent World Health Organization grade IV malignant glioma, a notoriously treatment-refractory cancer. Cytopathogenic infection of neoplastic cells releases the proteome and exposes pathogen- and damage-associated molecular patterns. At the same time, sublethal infection of antigen-presenting cells, such as dendritic cells and macrophages, yields potent, sustained type I interferon-dominant activation in an immunosuppressed microenvironment and promotes the development of tumor antigen-specific T cell responses in vitro and antitumor immunity in vivo. PVSRIPO's immune adjuvancy stimulates canonical innate anti-pathogen inflammatory responses within the tumor microenvironment that culminate in dendritic cell and T cell infiltration. Our findings provide mechanistic evidence that PVSRIPO functions as a potent intratumor immune adjuvant that generates tumor antigen-specific cytotoxic T lymphocyte responses.

Employing RNA viruses to fight cancer: novel insights into oncolytic virotherapy

Within recent decades, viruses that specifically target tumor cells have emerged as novel therapeutic agents against cancer. These viruses do not only act via their cell-lytic properties, but also harbor immunostimulatory features to re-direct the tumor microenvironment and stimulate tumor-directed immune responses. Furthermore, oncolytic viruses are considered to be superior to classical cancer therapies due to higher selectivity towards tumor cell destruction and, consequently, less collateral damage of non-transformed healthy tissue. In particular, the field of oncolytic RNA viruses is rapidly developing since these agents possess alternative tumor-targeting strategies compared to established oncolytic DNA viruses. Thus, oncolytic RNA viruses have broadened the field of virotherapy facilitating new strategies to fight cancer. In addition to several naturally occurring oncolytic viruses, genetically modified RNA viruses that are armed to express foreign factors such as immunostimulatory molecules have been successfully tested in early clinical trials showing promising efficacy. This review aims to provide an overview of the most promising RNA viruses in clinical development, to summarize the current knowledge of clinical trials using these viral agents, and to discuss the main issues as well as future perspectives of clinical approaches using oncolytic RNA viruses.

Human picornaviruses associated with neurological diseases and their neutralization by antibodies

Picornaviruses are the most commonly encountered infectious agents in mankind. They typically cause mild infections of the gastrointestinal or respiratory tract, but sometimes also invade the central nervous system. There, they can cause severe diseases with long-term sequelae and even be lethal. The most infamous picornavirus is poliovirus, for which significant epidemics of poliomyelitis were reported from the end of the nineteenth century. A successful vaccination campaign has brought poliovirus close to eradication, but neurological diseases caused by other picornaviruses have increasingly been reported since the late 1990s. In this review we focus on enterovirus 71, coxsackievirus A16, enterovirus 68 and human parechovirus 3, which have recently drawn attention because of their links to severe neurological diseases. We discuss the clinical relevance of these viruses and the primary role of humoral immunity in controlling them, and summarize current knowledge on the neutralization of such viruses by antibodies.

Functional paralysis of GM-CSF-derived bone marrow cells productively infected with ectromelia virus

Ectromelia virus (ECTV) is an orthopoxvirus responsible for mousepox, a lethal disease of certain strains of mice that is similar to smallpox in humans, caused by variola virus (VARV). ECTV, similar to VARV, exhibits a narrow host range and has co-evolved with its natural host. Consequently, ECTV employs sophisticated and host-specific strategies to control the immune cells that are important for induction of antiviral immune response. In the present study we investigated the influence of ECTV infection on immune functions of murine GM-CSF-derived bone marrow cells (GM-BM), comprised of conventional dendritic cells (cDCs) and macrophages. Our results showed for the first time that ECTV is able to replicate productively in GM-BM and severely impaired their innate and adaptive immune functions. Infected GM-BM exhibited dramatic changes in morphology and increased apoptosis during the late stages of infection. Moreover, GM-BM cells were unable to uptake and process antigen, reach full maturity and mount a proinflammatory response. Inhibition of cytokine/chemokine response may result from the alteration of nuclear translocation of NF-κB, IRF3 and IRF7 transcription factors and down-regulation of many genes involved in TLR, RLR, NLR and type I IFN signaling pathways. Consequently, GM-BM show inability to stimulate proliferation of purified allogeneic CD4+ T cells in a primary mixed leukocyte reaction (MLR). Taken together, our data clearly indicate that ECTV induces immunosuppressive mechanisms in GM-BM leading to their functional paralysis, thus compromising their ability to initiate downstream T-cell activation events.

Immunotherapy approaches in the treatment of malignant brain tumors

Glioblastoma is the most common malignant primary brain tumor. Despite standard-of-care treatment, consisting of maximal surgical resection followed by chemoradiation, both morbidity and mortality associated with this disease remain very poor. Therefore, there is an urgent need for more efficacious and well tolerated therapies. Advancing knowledge of the intricate interplay between malignant gliomas and the immune system, coupled with the recent launch of immunotherapy research for other cancers, has led to a veritable increase in immunotherapy investigation for glioblastoma and other malignant gliomas. This clinical review highlights the recent breakthroughs in cancer immunotherapy and the complex correlation of the immune system with primary brain tumors, with special attention to multiple immunotherapy modalities currently being investigated for malignant glioma, including peptide vaccines, dendritic cell vaccines, oncolytic viruses, chimeric T-cell receptors, and checkpoint inhibitors. Cancer 2017;123:734-50. © 2016 American Cancer Society.

Pathologic and immunologic characteristics of coxsackievirus A16 infection in rhesus macaques

Coxsackievirus A16 (CV-A16) causes human hand, foot and mouth disease, but its pathogenesis is unclear. In rhesus macaques, CV-A16 infection causes characteristic vesicles in the oral mucosa and limbs as well as viremia and positive viral loads in the tissues, suggesting that these animals reflect the pathologic process of the infection. An immunologic analysis indicated a defective immune response, which included undetectable neutralizing antibodies and IFN-γ-specific memory T-cells in macaques infected with CV-A16. Furthermore, existing neutralizing antibodies in macaques immunized with the inactivated vaccine were surprisingly unable to protect against a viral challenge despite the presence of a positive T-cell memory response against viral antigens. The virus was capable of infecting pre-conventional dendritic cells and replicating within them, which may correlate with the immunological characteristics observed in the animals.

Cytotoxic and immunogenic mechanisms of recombinant oncolytic poliovirus

An oncolytic virus (OV) based on poliovirus (PV), the highly attenuated polio/rhinovirus recombinant PVSRIPO, may deliver targeted inflammatory cancer cell killing; a principle that is showing promise in clinical trials for recurrent glioblastoma (GBM). The two decisive factors in PVSRIPO anti-tumor efficacy are selective cytotoxicity and its in situ immunogenic imprint. While our work is focused on what constitutes PVSRIPO cancer cytotoxicity, we are also studying how this engenders host immune responses that are vital to tumor regression. We hypothesize that PVSRIPO cytotoxicity and immunogenicity are inextricably linked in essential, complimentary roles that define the anti-neoplastic response. Herein we delineate mechanisms we unraveled to decipher the basis for PVSRIPO cytotoxicity and its immunotherapeutic potential.

Oncolytic immunotherapy through tumor-specific translation and cytotoxicity of poliovirus

Achieving tumor-specific, robust, and durable effector cytotoxic immune responses is key to successful immunotherapy. This has been accomplished with adoptive cell transfer of ex vivo-expanded autologous tumor-infiltrating or engineered T cells, or with immune checkpoint inhibitors, enhancing inherent T cell reactivity. A natural ability to recruit effector responses makes tumor-targeting ('oncolytic') viruses attractive as immunotherapy vehicles. However, most viruses actively block inflammatory and immunogenic events; or, host innate immune responses may prevent immune initiating events in the first place. Moreover, the mechanisms of how virus infection can produce effector responses against host (tumor) neo-antigens are unclear. We are pioneering oncolytic immunotherapy based on poliovirus, which has no specific mechanism to interfere with host immune activation, exhibits lytic cytotoxicity in the presence of an antiviral interferon response and pre-existing immunity, and engages a powerful innate immune sensor implicated in recruiting cytotoxic T cell responses. Central to this approach is a unique confluence of factors that drive tumor-specific viral translation and cytotoxicity.

Post-poliomyelitis syndrome as a possible viral disease

This review summarizes current concepts on post-polio syndrome (PPS), a condition that may arise in polio survivors after partial or complete functional recovery followed by a prolonged interval of stable neurological function. PPS affects 15-20 million people worldwide. Epidemiological data are reported, together with the pathogenic pathways that possibly lead to the progressive degeneration and loss of neuromuscular motor units. As a consequence of PPS, polio survivors experience new weakness, generalized fatigue, atrophy of previously unaffected muscles, and a physical decline that may culminate in the loss of independent life. Emphasis is given to the possible pathogenic role of persistent poliovirus infection and chronic inflammation. These factors could contribute to the neurological and physical decline in polio survivors. A perspective is then given on novel anti-poliovirus compounds and monoclonal antibodies that have been developed to contribute to the final phases of polio eradication. These agents could also be useful for the treatment or prevention of PPS. Some of these compounds/antibodies are in early clinical development. Finally, current clinical trials for PPS are reported. In this area, the intravenous infusion of normal human immunoglobulins appears both feasible and promising.

Differential permissivity of human cerebrovascular endothelial cells to enterovirus infection and specificities of serotype EV-A71 in crossing an in vitro model of the human blood-brain barrier

Human cerebral microvascular endothelial cells (hCMEC/D3 cell line) form a steady polarized barrier when cultured in vitro on a permeable membrane. Their susceptibility to enterovirus (EV) strains was analysed to investigate how these viruses may cross the blood-brain barrier. A sample of 88 virus strains was selected on phylogenetic features amongst 43 epidemiologically relevant types of the four EV species A-D. The EV-A71 genome was replicated at substantial rates, whilst the infectious virus was released at extremely low but sustained rates at both barrier sides for at least 4 days. EV-A71 antigens were detected in a limited number of cells. The properties of the endothelial barrier (structure and permeability) remained intact throughout infection. The chronic EV-A71 infection was in sharp contrast to the productive infection of cytolytic EVs (e.g. echoviruses E-6 and E-30). The hCMEC/D3 barriers infected with the latter EVs exhibited elevated proportions of apoptotic and necrotic cells, which resulted in major injuries to the endothelial barriers with a dramatic increase of paracellular permeability and virus crossing to the abluminal side. The following intracellular rearrangements were also seen: early destruction of the actin cytoskeleton, remodelling of intracellular membranes and reorganization of the mitochondrion network in a small cluster near the perinuclear space.

The immunological effects of oral polio vaccine provided with BCG vaccine at birth: a randomised trial

BACKGROUND

Vaccines may have non-specific effects. An observational study from Guinea-Bissau suggested that oral polio vaccine at birth (OPV0) provided with Bacillus Calmette-Guérin (BCG) vaccine was associated with down-regulation of the immune response to BCG vaccine 6 weeks later. Based on the previous finding, we wanted to test our a priori hypothesis that OPV would dampen the immune response to BCG, and secondarily to test immune responses to other antigens.

METHODS

The study was conducted at the Bandim Health Project in Guinea-Bissau in 2009-2010. Infants were randomised to OPV0+BCG versus BCG alone at birth, and subsequently randomised to have a blood sample taken at 2, 4 or 6 weeks post-randomisation. Excreted levels of cytokines (IL-2, IL-5, IL-10, TNF-α and IFN-γ) were measured from whole blood in vitro stimulations with a panel of recall vaccine antigens (BCG, PPD, OPV), mitogen (PHA) or innate agonists (LPS, Pam3cys, PolyI:C). Additionally, we measured the local reaction to BCG, white blood cell distribution, C-reactive protein (CRP) and retinol-binding protein (RBP). Cytokine production was analysed as the prevalence ratios of responders above the median.

RESULTS

Blood samples from 430 infants (209 OPV0+BCG; 221 BCG alone) were analysed. There were no strong differences in effects 2, 4 and 6 weeks post-randomisation and subsequent analyses were performed on the pooled data. As hypothesised, receiving OPV0+BCG versus BCG alone was associated with significantly lower prevalence of IFN-γ responses to PPD (prevalence ratio (PR): 0.84 (0.72-0.98)) and reduced IL-5 to PPD (PR: 0.78 (0.64-0.96)). No effects were observed for CPR, RBP, white blood cell distribution, or BCG scar prevalence.

CONCLUSION

The results corroborate that OPV attenuates the immune response to co-administered BCG at birth.

Oncolytic polio virotherapy of cancer

Recently, the century-old idea of targeting cancer with viruses (oncolytic viruses) has come of age, and promise has been documented in early stage and several late-stage clinical trials in a variety of cancers. Although originally prized for their direct tumor cytotoxicity (oncolytic virotherapy), recently, the proinflammatory and immunogenic effects of viral tumor infection (oncolytic immunotherapy) have come into focus. Indeed, a capacity for eliciting broad, sustained antineoplastic effects stemming from combined direct viral cytotoxicity, innate antiviral activation, stromal proinflammatory stimulation, and recruitment of adaptive immune effector responses is the greatest asset of oncolytic viruses. However, it also is the source for enormous mechanistic complexity that must be considered for successful clinical translation. Because of fundamentally different relationships with their hosts (malignant or not), diverse replication strategies, and distinct modes of tumor cytotoxicity/killing, oncolytic viruses should not be referred to collectively. These agents must be evaluated based on their individual merits. In this review, the authors highlight key mechanistic principles of cancer treatment with the polio:rhinovirus chimera PVSRIPO and their implications for oncolytic immunotherapy in the clinic.

Poliomyelitis in transgenic mice expressing CD155 under the control of the Tage4 promoter after oral and parenteral poliovirus inoculation

An important step in poliovirus (PV) infection by the oral route in humans is replication of the virus in lymphatic tissues of the gastrointestinal (GI) tract, thought to be mainly in the Peyer's patches of the small intestine. No immunocompetent transgenic (tg) mice that express human PV receptor (CD155) under the control of different promoters can be infected orally. The mouse orthologue of human CD155 is Tage4, a protein expressed at the surface of enterocytes and in the Peyer's patches. We describe here the generation of a tg mouse model in which the Tage4 promoter was used to drive expression of the human PV receptor-coding region (Tage4-CD155tg mice). In this model, CD155 expression was observed by immunostaining in different regions in the Peyer's patches but not in their germinal centres. Although a similar pattern of staining was observed between 3- and 6-week-old Tage4-CD155tg mice, poliomyelitis was only seen in the younger mice after PV infection by the oral route. When compared with TgPVR21 mice that expressed CD155 driven by its human promoter, 3-week-old Tage4-CD155tg mice were more susceptible to gut infection and paralysis following feeding with PV. Also, Tage4-CD155tg mice exhibited higher susceptibility to poliomyelitis after parenteral inoculation of PV. Remarkably, the LD50 after intracerebral inoculation of PV was similar in both CD155 tg mouse strains. The CD155 tg mouse model reported here, although moderately susceptible to oral infection, may be suitable to study mechanisms of PV replication in the gastrointestinal tract and to dissect important aspects of PV neuroinvasiveness.

Differential susceptibility and response of primary human myeloid BDCA1(+) dendritic cells to infection with different Enteroviruses

Coxsackie B viruses (CVBs) and echoviruses (EVs) form the Human Enterovirus-B (HEV-B) species within the family Picornaviridae. HEV-B infections are widespread and generally cause mild disease; however, severe infections occur and HEV-B are associated with various chronic diseases such as cardiomyopathy and type 1 diabetes. Dendritic cells (DCs) are the professional antigen-presenting cells of our immune system and initiate and control immune responses to invading pathogens, yet also maintain tolerance to self-antigens. We previously reported that EVs, but not CVBs, can productively infect in vitro generated monocyte-derived DCs. The interactions between HEV-B and human myeloid DCs (mDCs) freshly isolated from blood, however, remain unknown. Here, we studied the susceptibility and responses of BDCA1(+) mDC to HEV-B species and found that these mDC are susceptible to EV, but not CVB infection. Productive EV7 infection resulted in massive, rapid cell death without DC activation. Contrary, EV1 infection, which resulted in lower virus input at the same MOI, resulted in DC activation as observed by production of type I interferon-stimulated genes (ISGs), upregulation of co-stimulatory and co-inhibitory molecules (CD80, CD86, PDL1) and production of IL-6 and TNF-α, with a relative moderate decrease in cell viability. EV1-induced ISG expression depended on virus replication. CVB infection did not affect DC viability and resulted in poor induction of ISGs and CD80 induction in part of the donors. These data show for the first time the interaction between HEV-B species and BDCA1(+) mDCs isolated freshly from blood. Our data indicate that different HEV-B species can influence DC homeostasis in various ways, possibly contributing to HEV-B associated pathology.

CD34+ hematopoietic stem cells support entry and replication of poliovirus: a potential new gene introduction route

Pluripotent hematopoietic stem cells (HSC) are critical in sustaining and constantly renewing the blood and immune system. The ability to alter biological characteristics of HSC by introducing and expressing genes would have enormous therapeutic possibilities. Previous unpublished work suggested that human HSC co-express CD34 (cluster of differentiation 34; an HSC marker) and CD155 (poliovirus receptor; also called Necl-5/Tage4/PVR/CD155). In the present study, we demonstrate the co-expression of CD34 and CD155 in primary human HSC. In addition, we demonstrate that poliovirus infects and replicates in human hematopoietic progenitor cell lines. Finally, we show that poliovirus replicates in CD34+ enriched primary HSC. CD34+ enriched HSC co-express CD155 and support poliovirus replication. These data may help further understanding of poliovirus spread in vivo and also demonstrate that human HSC may be amenable for gene therapy via poliovirus-capsid-based vectors. They may also help elucidate the normal function of Necl-5/Tage4/PVR/CD155.

Cytopathic effects: virus-modulated manifestations of innate immunity?

The capacity to injure infected cells is a widespread property of viruses. Usually, this cytopathic effect (CPE) is ascribed to viral hijacking of cellular resources to fulfill viral needs. However, evidence is accumulating that CPE is not necessarily directly coupled to viral reproduction but may largely be due to host defensive and viral antidefensive activities. A major part in this virus–cell interaction appears to be played by a putative host-encoded program with multiple competing branches, leading to necrotic, apoptotic, and, possibly, other types of cell suicide. Manifestations of this program are controlled and modulated by host, viral, and environmental factors.

Excessive proinflammatory cytokine and chemokine responses of human monocyte-derived macrophages to enterovirus 71 infection

BACKGROUND

The levels of proinflammatory cytokine or chemokine in blood and cerebrospinal fluid are thought to be one of predictors for clinical severity of enterovirus 71 (EV71) infection, yet the cellular sources or signalling mechanism remain undefined. Here, we focused on the response of human primary monocyte-derived macrophages (MDMs) to EV71 virus and its possible mechanisms.

METHODS

Human primary MDMs were infected by EV71 virus in vitro. Infectivity and viral replication were assayed, and cytokine responses were determined by Cytometric Bead Array(CBA) analysis. The relative changes of Toll-like receptors, retinoic acid-inducible gene I (RIG-I) and melamoma differentiation associated gene 5 (MDA5) mRNA expression were detected by real-time RT-PCR.

RESULTS

Effective infection and viral replication were detected in EV71-infected MDMs. The titters of progeny virus released from EV71-infected MDMs gradually increased from 6-h to 48-h point of infection (POI.). Proinflammatory cytokines: IL-1, IL-6, TNF-α but not IFN-α and γ were induced in MDMs by EV71. EV71 infection significantly increased the release of IL-8, IP-10 and RANTES at 12-h or 24-h POI. Upregulation of TLR2, TLR7 and TLR8 mRNA expression rather than TLR3, TLR4, TLR6, TLR9, TLR10, RIG-I, MDA5 were found at different time points in EV71-infected MDMs.

CONCLUSIONS

Our findings suggested that macrophages are not only the important target cells but also the effectors during EV71 infection, and they may play an important role in the pathogenesis of EV71 infection. And the proinflammatory cytokine and chemokine responses in EV71-infected MDMs may be mediated by the activation of differential pattern of TLRs.

Wild-type coxsackievirus infection dramatically alters the abundance, heterogeneity, and immunostimulatory capacity of conventional dendritic cells in vivo

In vitro studies have shown that enteroviruses employ strategies that may impair the ability of DCs to trigger T cell immunity, but it is unclear how these viruses affect DCs in vivo. Here, we evaluate the effects of wild-type (wt) coxsackievirus B3 on DCs in vitro and in a murine model in vivo. Although CVB3 does not productively infect the vast majority of DCs, virus infection profoundly reduces splenic conventional DC numbers and diminishes their capacity to prime naïve CD8(+) T cells in vitro. In contrast to recombinant CVB3, highly pathogenic wt virus infection significantly diminishes the host's capacity to mount T cell responses, which is temporally associated with the loss of CD8α(+) DCs. Our findings demonstrate that enterovirus infection substantially alters the number, heterogeneity, and stimulatory capacity of DCs in vivo, and these dramatic immunomodulatory effects may weaken the host's capacity to mount antiviral T cell responses.

Viral and host factors that contribute to pathogenicity of enterovirus 71

The single-stranded RNA virus enterovirus 71 (EV71), which belongs to the Picornaviridae family, has caused epidemics worldwide, particularly in the Asia–Pacific region. Most EV71 infections result in mild clinical symptoms, including herpangina and hand, foot and mouth disease. However, serious pathological complications have also been reported, especially for young children. The mechanisms of EV71 disease progression remain unclear. The pathogenesis of adverse clinical outcomes may relate to many factors, including cell tropism, cell death and host immune responses. This article reviews the recent advances in the identification of factors determining EV71 cell tropism, the associated mechanisms of viral infection-induced cell death and the interplay between EV71 and immunity.

Different mechanisms preserve translation of programmed cell death 8 and JunB in virus-infected endothelial cells

OBJECTIVE

Translation initiation of eukaryotic mRNAs typically occurs by cap-dependent ribosome scanning mechanism. However, certain mRNAs are translated by ribosome assembly at internal ribosome entry sites (IRESs). Whether IRES-mediated translation occurs in stressed primary human endothelial cells (ECs) is unknown.

METHODS AND RESULTS

We performed microarray analysis of polyribosomal mRNA from ECs to identify IRES-containing mRNAs. Cap-dependent translation was disabled by poliovirus (PV) infection and confirmed by loss of polysome peaks, detection of eukaryotic initiation factor (eIF) 4G cleavage, and decreased protein synthesis. We found that 87.4% of mRNAs were dissociated from polysomes in virus-infected ECs. Twelve percent of mRNAs remained associated with polysomes, and 0.6% were enriched ≥2-fold in polysome fractions from infected ECs. Quantitative reverse transcription-polymerase chain reaction confirmed the microarray findings for 31 selected mRNAs. We found that enriched polysome associations of programmed cell death 8 (PDCD8) and JunB mRNA resulted in increased protein expression in PV-infected ECs. The presence of IRESs in the 5' untranslated region of PDCD8 mRNA, but not of JunB mRNA, was confirmed by dicistronic analysis.

CONCLUSIONS

We show that microarray profiling of polyribosomal mRNA transcripts from PV-infected ECs successfully identifies mRNAs whose translation is preserved in the face of stress-induced, near complete cessation of cap-dependent initiation. Nevertheless, internal ribosome entry is not the only mechanism responsible for this privileged translation.

Characterization of infections of human leukocytes by non-polio enteroviruses

To elucidate the detailed susceptibilities of leukocytes to clinically important non-polio enteroviruses (EVs), primary monocytes and various human leukocyte cell lines were infected with coxsackievirus A24 (CVA24), coxsackievirus B3 (CVB3), and enterovirus 70 (EV70). The permissiveness was then assessed by determining virus replication and resultant cytopathic effects. Different EVs varied markedly in their ability to infect leukocyte cell lines. CVB3 replicated effectively in leukocytes of B-cell, T-cell, and monocyte origin, CVA24 in leukocytes of B-cell and monocyte origin, and EV70 in leukocytes of monocyte origin. Primary monocytes, as well as monocyte-derived U-937 cells, were permissive to all three EVs. We observed a positive correlation between cytotoxicity and active virus replication, except in CVB3-infected monocytes. U-937 cells efficiently generated CVB3 progeny virus without severe cellular damage, including cell death. Moreover, infectivity on leukocytes was not absolutely associated with the availability of viral receptors. These findings suggest that the susceptibility of human leukocytes to non-polio EVs may be responsible for virus transport during the viremic phase, particularly to secondary target organs, and that active replication of CVB3 in all human leukocyte lineages leads to greater dissemination, in agreement with the ability of CVB to cause systemic diseases.

Enterovirus infections of the central nervous system

Enteroviruses (EV) frequently infect the central nervous system (CNS) and induce neurological diseases. Although the CNS is composed of many different cell types, the spectrum of tropism for each EV is considerable. These viruses have the ability to completely shut down host translational machinery and are considered highly cytolytic, thereby causing cytopathic effects. Hence, CNS dysfunction following EV infection of neuronal or glial cells might be expected. Perhaps unexpectedly given their cytolytic nature, EVs may establish a persistent infection within the CNS, and the lasting effects on the host might be significant with unanticipated consequences. This review will describe the clinical aspects of EV-mediated disease, mechanisms of disease, determinants of tropism, immune activation within the CNS, and potential treatment regimes.