VP1 codon deoptimization and high-fidelity substitutions in 3D polymerase as potential vaccine strategies for eliciting immune responses against enterovirus A71.

Enterovirus A71 (EV-A71) can induce severe neurological complications and even fatal encephalitis in children, and it has caused several large outbreaks in Taiwan since 1998. We previously generated VP1 codon-deoptimized (VP1-CD) reverse genetics (rg) EV-A71 viruses (rgEV-A71s) that harbor a high-fidelity (HF) 3D polymerase. These VP1-CD-HF rgEV-A71s showed lower replication kinetics in vitro and decreased virulence in an Institute of Cancer Research (ICR) mouse model of EV-A71 infection, while still retaining their antigenicity in comparison to the wild-type virus. In this study, we aimed to further investigate the humoral and cellular immune responses elicited by VP1-CD-HF rgEV-A71s to assess the potential efficacy of these EV-A71 vaccine candidates. Following intraperitoneal (i.p.) injection of VP1-CD-HF rgEV-A71s in mice, we observed a robust induction of EV-A71-specific neutralizing IgG antibodies in the antisera after 21 days. Splenocytes isolated from VP1-CD-HF rgEV-A71s-immunized mice exhibited enhanced proliferative activities and cytokine production (IL-2, IFN-γ, IL-4, IL-6, and TNF-α) upon re-stimulation with VP1-CD-HF rgEV-A71, as compared to control mice treated with adjuvant only. Importantly, administration of antisera from VP1-CD-HF rgEV-A71s-immunized mice protected against lethal EV-A71 challenge in neonatal mice. These findings highlight that our generated VP1-CD-HF rgEV-A71 viruses are capable of inducing both cellular and humoral immune responses, supporting their potential as next-generation EV-A71 vaccines for combating EV-A71 infection.IMPORTANCEEV-A71 can cause severe neurological diseases and cause death in young children. Here, we report the development of synthetic rgEV-A71s with the combination of codon deoptimization and high-fidelity (HF) substitutions that generate genetically stable reverse genetics (rg) viruses as potential attenuated vaccine candidates. Our work provides insight into the development of low-virulence candidate vaccines through a series of viral genetic editing for maintaining antigenicity and genome stability and suggests a strategy for the development of an innovative next-generation vaccine against EV-A71.

Plasmacytoid Dendritic Cells Enhance T-Independent B Cell Response through a p38 MAPK-STAT1 Axis.

TLR signaling in B cells triggers their activation and differentiation independent of help from T cells. Plasmacytoid dendritic cells (pDCs) cooperate with B cells to boost TLR-stimulated T-independent humoral immunity; however, the molecular mechanisms remain elusive. In this study, we demonstrate that in the mouse system, the adjuvant effects of pDCs also occurred following challenge with pathogens and that follicular (FO) B cells were more sensitive to pDC-induced enhancement than were marginal zone (MZ) B cells. Moreover, pDCs migrated to the FO zones and interacted with FO B cells upon stimulation in vivo. CXCL10, a ligand for CXCR3 expressed on pDCs, was superinduced in the coculture system and facilitated the cooperative activation of B cells. Moreover, pDCs also promoted TLR-stimulated autoantibody production in FO B and MZ B cells. Ingenuity Pathway Analysis and gene set enrichment analysis revealed that type I IFN (IFN-I)-mediated JAK-STAT and Ras-MAPK pathways were highly enriched in R848-stimulated B cells cocultured with pDCs compared with B cells alone. Whereas IFN-I receptor 1 deficiency reduced pDC-enhanced B cell responses, STAT1 deficiency displayed a more pronounced defect. One of the STAT1-dependent but IFN-I-independent mechanisms was TLR-induced STAT1-S727 phosphorylation by p38 MAPK. Serine 727 to alanine mutation attenuated the synergism between pDCs and B cells. In conclusion, we uncover a molecular mechanism for pDC-enhanced B cell response and define a crucial role of the IFN-I/TLR-mediated signaling pathway through a p38 MAPK-STAT1 axis in controlling T-independent humoral immunity and providing a novel therapeutic target for treating autoimmune diseases.

Suppression of annexin A1 and its receptor reduces herpes simplex virus 1 lethality in mice.

Herpes simplex virus 1 (HSV-1)-induced encephalitis is the most common cause of sporadic, fatal encephalitis in humans. HSV-1 has at least 10 different envelope glycoproteins, which can promote virus infection. The ligands for most of the envelope glycoproteins and the significance of these ligands in virus-induced encephalitis remain elusive. Here, we show that glycoprotein E (gE) binds to the cellular protein, annexin A1 (Anx-A1) to enhance infection. Anx-A1 can be detected on the surface of cells permissive for HSV-1 before infection and on virions. Suppression of Anx-A1 or its receptor, formyl peptide receptor 2 (FPR2), on the cell surface and gE or Anx-A1 on HSV-1 envelopes reduced virus binding to cells. Importantly, Anx-A1 knockout, Anx-A1 knockdown, or treatments with the FPR2 antagonist reduced the mortality and tissue viral loads of infected mice. Our results show that Anx-A1 is a novel enhancing factor of HSV-1 infection. Anx-A1-deficient mice displayed no evident physiology and behavior changes. Hence, targeting Anx-A1 and FPR2 could be a promising prophylaxis or adjuvant therapy to decrease HSV-1 lethality.

Acyclovir-resistant HSV-1 isolates among immunocompromised patients in southern Taiwan: Low prevalence and novel mutations.

Herpes simplex virus type 1 (HSV-1) can establish latency in humans and easily relapse in immunocompromised patients, with significant mortality. Treatment with acyclovir (ACV) can result in the emergence of HSV resistance. A total of 440 frozen HSV-1 isolates collected from 318 patients from January 2014 to July 2019 were obtained from National Cheng Kung University Hospital in southern Taiwan. These 440 isolates were subjected to phenotypic studies for ACV-resistance by initial screening with the plaque reduction assay (PRA) and further validation by the DNA reduction assay (DRA). The ACV-resistant strains were further investigated by Sanger sequencing for the full-length UL23 and UL30 genes, which encode thymidine kinase and DNA polymerase, respectively. Hematological malignancies or hematopoietic stem-cell transplantation patients accounted for 56.9% (124/218) among the immunocompromised patients (218/318) in this study. Repeated sampling for HSV testing was 50% (109/218) in immunocompromised patients. Only 1.38% (3/218) of immunocompromised patients and 0.9% (3/318) of all patients developed ACV-resistant HSV-1 as measured by phenotypic screening assays. It is noteworthy that a novel Y248D mutation in the UL23 gene from an immunocompromised patient was found by both PRA and DRA. In 3D protein predicting analysis, uncharged Y248 was located at an alpha-helix and substituted by negative-charged D248, which may alter the function of viral thymidine kinase. Besides, three unreported mutations related to natural polymorphism were found in virus isolates from two immunocompetent patients, including 683-688 deletion, R227H, and A351D in the UL30 gene. These data show that the prevalence of ACV-resistant HSV-1 among immunocompromised patients in southern Taiwan is low. These results will be helpful for the clinical management and treatment of HSV infections.

Absence of the lectin-like domain of thrombomodulin reduces HSV-1 lethality of mice with increased microglia responses.

BACKGROUND: Herpes simplex virus 1 (HSV-1) can induce fatal encephalitis. Cellular factors regulate the host immunity to affect the severity of HSV-1 encephalitis. Recent reports focus on the significance of thrombomodulin (TM), especially the domain 1, lectin-like domain (TM-LeD), which modulates the immune responses to bacterial infections and toxins and various diseases in murine models. Few studies have investigated the importance of TM-LeD in viral infections, which are also regulated by the host immunity. METHODS: In vivo studies comparing wild-type and TM-LeD knockout mice were performed to determine the role of TM-LeD on HSV-1 lethality. In vitro studies using brain microglia cultured from mice or a human microglia cell line to investigate whether and how TM-LeD affects microglia to reduce HSV-1 replication in brain neurons cultured from mice or in a human neuronal cell line. RESULTS: Absence of TM-LeD decreased the mortality, tissue viral loads, and brain neuron apoptosis of HSV-1-infected mice with increases in the number, proliferation, and phagocytic activity of brain microglia. Moreover, TM-LeD deficiency enhanced the phagocytic activity of brain microglia cultured from mice or of a human microglia cell line. Co-culture of mouse primary brain microglia and neurons or human microglia and neuronal cell lines revealed that TM-LeD deficiency augmented the capacity of microglia to reduce HSV-1 replication in neurons. CONCLUSIONS: Overall, TM-LeD suppresses microglia responses to enhance HSV-1 infection.

From EGFR kinase inhibitors to anti-inflammatory drugs: Optimization and biological evaluation of (4-(phenylamino)quinazolinyl)-phenylthiourea derivatives as novel NF-κB inhibitors.

The transcription factor NF-κB is a pivotal mediator of chronic inflammatory and autoimmune diseases. Based on our previously published dual EGFR/NF-κB inhibitors, we designed and synthesized new thiourea quinazoline derivatives that retained only the NF-κB inhibitory activity. Several congeners displayed a strong suppression of NF-κB activity in a reporter gene assay, yet low cytotoxicity, and were further evaluated in differentiated macrophage-like THP-1 cells. The compounds exhibited a strong inhibition of IL-6 and, less potently, of TNFα release, which was accompanied by a selective induction of macrophage cell death. The mode of action was investigated with a selected inhibitor, 18, revealing that the translocation of p65/RelA to the nucleus but not its release from the IκB complex was inhibited. Eventually, 18 was identified as the first small molecule inhibitor affecting only the phosphorylation of p65-Ser468 but not of Ser536, which may be causally related to the retention of NF-κB in the cytoplasm. Altogether, our novel NF-κB inhibitors seem applicable for the suppression of cytokine release and the additional selective depletion of activated macrophages in various inflammatory diseases.

JAK2-Mediated Phosphorylation of Stress-Induced Phosphoprotein-1 (STIP1) in Human Cells.

Stress-induced phosphoprotein-1 (STIP1)-a heat shock protein (HSP)70/HSP90 adaptor protein-is commonly overexpressed in malignant cells, where it controls proliferation via multiple signaling pathways, including JAK2/STAT3. We have previously shown that STIP1 stabilizes the protein tyrosine kinase JAK2 in cancer cells via HSP90 binding. In this study, we demonstrate that STIP1 may act as a substrate for JAK2 and that phosphorylation of tyrosine residues 134 and 152 promoted STIP1 protein stability, induced its nuclear-cytoplasmic shuttling, and promoted its secretion into the extracellular space. We also found that JAK2-mediated STIP1 phosphorylation enhanced cell viability and increased resistance to cisplatin-induced cell death. Conversely, interference STIP1 with JAK2 interaction-attained either through site-directed mutagenesis or the use of cell-penetrating peptides-decreased JAK2 protein levels, ultimately leading to cell death. On analyzing human ovarian cancer specimens, JAK2 and STIP1 expression levels were found to be positively correlated with each other. Collectively, these results indicate that JAK2-mediated phosphorylation of STIP-1 is critical for sustaining the JAK2/STAT3 signaling pathway in cancer cells.

Doxycycline Ameliorates the Severity of Experimental Proliferative Vitreoretinopathy in Mice.

After successful surgeries for patients with rhegmatogenous retinal detachment, the most common cause of retinal redetachment is proliferative vitreoretinopathy (PVR), which causes severe vision impairment and even blindness worldwide. Until now, the major treatment for PVR is surgical removal of the epiretinal membrane, while effective treatment to prevent PVR is still unavailable. Therefore, we investigated the potential of doxycycline, an antibiotic in the tetracycline class, to treat PVR using a mouse model. We used the human retinal pigment epithelial cell line, ARPE-19, for in vitro and in vivo studies to test doxycycline for PVR treatment. We found that doxycycline suppressed the migration, proliferation, and contraction of ARPE-19 cells with reduced p38 MAPK activation and total MMP activity. Intravitreal doxycycline and topical tetracycline treatment significantly ameliorated the PVR severity induced by ARPE-19 cells in mice. PVR increased the expression of MMP-9 and IL-4 and p38 MAPK phosphorylation and modestly decreased IL-10. These effects were reversed by doxycycline and tetracycline treatment in the mouse retina. These results suggest that doxycycline will be a potential treatment for PVR in the future.

Microglia Reduce Herpes Simplex Virus 1 Lethality of Mice with Decreased T Cell and Interferon Responses in Brains.

Herpes simplex virus 1 (HSV-1) infects the majority of the human population and can induce encephalitis, which is the most common cause of sporadic, fatal encephalitis. An increase of microglia is detected in the brains of encephalitis patients. The issues regarding whether and how microglia protect the host and neurons from HSV-1 infection remain elusive. Using a murine infection model, we showed that HSV-1 infection on corneas increased the number of microglia to outnumber those of infiltrating leukocytes (macrophages, neutrophils, and T cells) and enhanced microglia activation in brains. HSV-1 antigens were detected in brain neurons, which were surrounded by microglia. Microglia depletion increased HSV-1 lethality of mice with elevated brain levels of viral loads, infected neurons, neuron loss, CD4 T cells, CD8 T cells, neutrophils, interferon (IFN)-ß, and IFN-γ. In vitro studies demonstrated that microglia from infected mice reduced virus infectivity. Moreover, microglia induced IFN-ß and the signaling pathway of signal transducer and activator of transcription (STAT) 1 to inhibit viral replication and damage of neurons. Our study reveals how microglia protect the host and neurons from HSV-1 infection.

The cellular immunophenotype expression of influenza A virus and influenza B virus infection in children.

BACKGROUND: The innate immune response is the primary defense against influenza virus infection. METHODS: This is a prospective study carried out in children <18 years of age who were diagnosed with influenza A or influenza B infection. Demographic and clinical data, laboratory findings and cell immunophenotypes on first presentation were compared. RESULTS: With respect to immunophenotype, influenza A infection resulted in a higher fraction of CD14+ and CD4+IL-17A+cells compared to children infected with influenza B. By contrast, influenza B infection resulted in a comparatively higher percentage of double-negative CD4-CD8- lymphocyte subsets. Influenza A infection was associated with comparatively higher percentages of CD4+CD25highFoxp3+ and CD4+CD25lowFoxp3+ cells. By contrast, the percentage of CD8+CD25high and CD8+CD25low cells was similar among patients with influenza A infection and influenza B infection. CONCLUSIONS: An improved understanding of the fraction of regulatory T cells with influenza virus infections may provide further understandings on immune responses.

Chitosan Oligosaccharides Suppress Nuclear Factor-Kappa B Activation and Ameliorate Experimental Autoimmune Uveoretinitis in Mice.

We investigated the therapeutic potential and mechanism of chitosan oligosaccharides (COS) for experimental autoimmune uveoretinitis (EAU) in mice. EAU was induced in C57/BL6 mice by injection of human interphotoreceptor retinoid-binding protein (IRBP) peptides. At the same time, a high or low dose (20 or 10 mg/kg) of COS or phosphate-buffered saline (PBS) was given to mice daily after EAU induction. We found that mouse EAU is ameliorated by the high-dose COS treatment when compared with PBS treatment. In the retinas of high-dose COS-treated mice, the nuclear translocation of NF-κB subunit (p65) was suppressed, and the expression of several key EAU inflammatory mediators, IFN-γ, TNF-α, IL-1α, IL-4, IL-5, IL-6, IL-10, IL-17 and MCP-1 was lowered. These results suggest that COS may be a potential treatment for posterior uveitis.

Suppression of the Reactive Oxygen Response Alleviates Experimental Autoimmune Uveitis in Mice.

Reactive oxygen species (ROS) are produced by host phagocytes and play an important role in antimicrobial actions against various pathogens. Autoimmune uveitis causes blindness and severe visual impairment in humans at all ages worldwide. However, the role of ROS in autoimmune uveitis remains unclear. We used ROS-deficient (Ncf1-/-) mice to investigate the role of ROS in experimental autoimmune uveitis (EAU). Besides, we also used the antioxidant N-acetylcysteine (NAC) treatment to evaluate the effect of suppression of ROS on EAU in mice. The EAU disease scores of Ncf1-/- mice were significantly lower than those of wild-type mice. EAU induction increased the levels of cytokines (interleukin (IL)-1α, IL-1ß, IL-4, IL-6, IL-12, IL-17, and tumor necrosis factor (TNF)-α) and chemokines (monocyte chemoattractant protein (MCP)-1) in the retinas of wild-type mice but not in those of Ncf1-/- mice. EAU induction enhanced the level of NF-κB activity in wild-type mice. However, the level of NF-κB activity in Ncf1-/- mice with EAU induction was low. Treatment with the antioxidant NAC also decreased the severity of EAU in mice with reduced levels of oxidative stress, inflammatory mediators, and NF-κB activation in the retina. We successfully revealed a novel role of ROS in the pathogenesis of EAU and suggest a potential antioxidant role for the treatment of autoimmune uveitis in the future.

Interleukin-6 from Adipose-Derived Stem Cells Promotes Tissue Repair by the Increase of Cell Proliferation and Hair Follicles in Ischemia/Reperfusion-Treated Skin Flaps.

The most common postoperative complication after reconstructive surgery is flap necrosis. Adipose-derived stem cells (ADSCs) and their secretomes are reported to mediate skin repair. This study was designed to investigate whether conditioned media from ADSCs (ADSC-CM) protects ischemia/reperfusion- (I/R-) induced injury in skin flaps by promoting cell proliferation and increasing the number of hair follicles. The mouse flap model of ischemia was ligating the long thoracic vessels for 3 h, followed by blood reperfusion. ADSC-CM was administered to the flaps, and their survival was observed on postoperative day 5. ADSC-CM treatment led to a significant increase in cell proliferation and the number of hair follicles. IL-6 levels in the lysate and CM from ADSCs were significantly higher than those from Hs68 fibroblasts. Furthermore, a strong decrease in cell proliferation and the number of hair follicles was observed after treatment with IL-6-neutralizing antibodies or si-IL-6-ADSC. In addition, ADSC transplantation increased flap repair, cell proliferation, and hair follicle number in I/R injury of IL-6-knockout mice. In conclusion, IL-6 secreted from ADSCs promotes the survival of I/R-induced flaps by increasing cell proliferation and the number of hair follicles. ADSCs represent a promising therapy for preventing skin flap necrosis following reconstructive and plastic surgery.

Thymidine Kinase-Negative Herpes Simplex Virus 1 Can Efficiently Establish Persistent Infection in Neural Tissues of Nude Mice.

Herpes simplex virus 1 (HSV-1) establishes latency in neural tissues of immunocompetent mice but persists in both peripheral and neural tissues of lymphocyte-deficient mice. Thymidine kinase (TK) is believed to be essential for HSV-1 to persist in neural tissues of immunocompromised mice, because infectious virus of a mutant with defects in both TK and UL24 is detected only in peripheral tissues, but not in neural tissues, of severe combined immunodeficiency mice (T. Valyi-Nagy, R. M. Gesser, B. Raengsakulrach, S. L. Deshmane, B. P. Randazzo, A. J. Dillner, and N. W. Fraser, Virology 199:484-490, 1994, https://doi.org/10.1006/viro.1994.1150). Here we find infiltration of CD4 and CD8 T cells in peripheral and neural tissues of mice infected with a TK-negative mutant. We therefore investigated the significance of viral TK and host T cells for HSV-1 to persist in neural tissues using three genetically engineered mutants with defects in only TK or in both TK and UL24 and two strains of nude mice. Surprisingly, all three mutants establish persistent infection in up to 100% of brain stems and 93% of trigeminal ganglia of adult nude mice at 28 days postinfection, as measured by the recovery of infectious virus. Thus, in mouse neural tissues, host T cells block persistent HSV-1 infection, and viral TK is dispensable for the virus to establish persistent infection. Furthermore, we found 30- to 200-fold more virus in neural tissues than in the eye and detected glycoprotein C, a true late viral antigen, in brainstem neurons of nude mice persistently infected with the TK-negative mutant, suggesting that adult mouse neurons can support the replication of TK-negative HSV-1. IMPORTANCE: Acyclovir is used to treat herpes simplex virus 1 (HSV-1)-infected immunocompromised patients, but treatment is hindered by the emergence of drug-resistant viruses, mostly those with mutations in viral thymidine kinase (TK), which activates acyclovir. TK mutants are detected in brains of immunocompromised patients with persistent infection. However, answers to the questions as to whether TK-negative (TK-) HSV-1 can establish persistent infection in brains of immunocompromised hosts and whether neurons in vivo are permissive for TK- HSV-1 remain elusive. Using three genetically engineered HSV-1 TK- mutants and two strains of nude mice deficient in T cells, we found that all three HSV-1 TK- mutants can efficiently establish persistent infection in the brain stem and trigeminal ganglion and detected glycoprotein C, a true late viral antigen, in brainstem neurons. Our study provides evidence that TK- HSV-1 can persist in neural tissues and replicate in brain neurons of immunocompromised hosts.

PM2.5-induced oxidative stress increases intercellular adhesion molecule-1 expression in lung epithelial cells through the IL-6/AKT/STAT3/NF-κB-dependent pathway.

BACKGROUND: Epidemiological studies have shown that ambient air pollution is closely associated with increased respiratory inflammation and decreased lung function. Particulate matters (PMs) are major components of air pollution that damages lung cells. However, the mechanisms remain to be elucidated. This study examines the effects of PMs on intercellular adhesion molecule-1 (ICAM-1) expression and the related mechanisms in vitro and in vivo. RESULT: The cytotoxicity, reactive oxygen species (ROS) generation, and monocyte adherence to A549 cells were more severely affected by treatment with O-PMs (organic solvent-extractable fraction of SRM1649b) than with W-PMs (water-soluble fraction of SRM1649b). We observed a significant increase in ICAM-1 expression by O-PMs, but not W-PMs. O-PMs also induced the phosphorylation of AKT, p65, and STAT3. Pretreating A549 cells with N-acetyl cysteine (NAC), an antioxidant, attenuated O-PMs-induced ROS generation, the phosphorylation of the mentioned kinases, and the expression of ICAM-1. Furthermore, an AKT inhibitor (LY294002), NF-κB inhibitor (BAY11-7082), and STAT3 inhibitor (Stattic) significantly down-regulated O-PMs-induced ICAM-1 expression as well as the adhesion of U937 cells to epithelial cells. Interleukin-6 (IL-6) was the most significantly changed cytokine in O-PMs-treated A549 cells according to the analysis of the cytokine antibody array. The IL-6 receptor inhibitor tocilizumab (TCZ) and small interfering RNA for IL-6 significantly reduced ICAM-1 secretion and expression as well as the reduction of the AKT, p65, and STAT3 phosphorylation in O-PMs-treated A549 cells. In addition, the intratracheal instillation of PMs significantly increased the levels of the ICAM-1 and IL-6 in lung tissues and plasma in WT mice, but not in IL-6 knockout mice. Pre-administration of NAC attenuated those PMs-induced adverse effects in WT mice. Furthermore, patients with chronic obstructive pulmonary disease (COPD) had higher plasma levels of ICAM-1 and IL-6 compared to healthy subjects. CONCLUSION: These results suggest that PMs increase ICAM-1 expression in pulmonary epithelial cells in vitro and in vivo through the IL-6/AKT/STAT3/NF-κB signaling pathway.

Co-housing reverses memory decline by epigenetic regulation of brain-derived neurotrophic factor expression in an animal model of Alzheimer's disease.

Co-housing with a company exerts profound effects on memory decline in animal model of Alzheimer's disease (AD). Recently, we found that APP/PS1 mice of 9-month-old improved their memories after co-housing with wide-type mice for 3months by increasing hippocampal brain-derived neurotrophic factor (BDNF) expression. However, the mechanism of how co-housing could induce BDNF expression remains elusive. Here we examined epigenetic changes in the mouse hippocampus that accompanied the co-housing-induced memory improvement. We found that the level of histone deacetylase 2 (HDAC2), but not that of HDAC1, was significantly lower in the memory improved mice than in the control and memory un-improved APP/PS1 mice after co-housing. Knockdown of Hdac2 resulted in a higher freezing response after co-housing. Conversely, over-expression of HDAC2 blocked co-housing-induced memory improvement. The level of Bdnf exon IV mRNA increased significantly after knockdown of Hdac2. ChIP assay revealed a decreased occupancy of HDAC2 in the promoter region of Bdnf exon IV of memory improved mice but not memory un-improved and control APP/PS1 mice. Consistently, the acetylation of histone 3 on Lys 9 (H3K9) and histone 4 on Lys12 (H4K12) increased significantly in the promoter region of Bdnf exon IV. These results suggest HDAC2 expression is reduced after co-housing resulting in a decreased occupancy of HDAC2 and increased histone H3K9 and H4K12 acetylation in the promoter region of Bdnf exon IV, leading to increased BDNF expression in the hippocampus that improves memory.

Suppression of interleukin-6 increases enterovirus A71 lethality in mice.

BACKGROUND: Enterovirus A71 (EV-A71) infection can induce fatal encephalitis in young children. Clinical reports show that interleukin-6 (IL-6) levels in the serum and cerebrospinal fluid of infected patients with brainstem encephalitis are significantly elevated. We used a murine model to address the significance of endogenous IL-6 in EV-A71 infection. RESULTS: EV-A71 infection transiently increased serum and brain IL-6 protein levels in mice. Most importantly, absence of IL-6 due to gene knockout or depletion of IL-6 using neutralizing monoclonal antibody enhanced the mortality and tissue viral load of infected mice. Absence of IL-6 increased the damage in the central nervous system and decreased the lymphocyte and virus-specific antibody responses of infected mice. CONCLUSIONS: Endogenous IL-6 functions to clear virus and protect the host from EV-A71 infection. Our study raises caution over the use of anti-IL-6 antibody or pentoxifylline to reduce IL-6 for patient treatment.

Cell surface nucleolin facilitates enterovirus 71 binding and infection.

UNLABELLED: Because the pathogenesis of enterovirus 71 (EV71) remains mostly ambiguous, identifying the factors that mediate viral binding and entry to host cells is indispensable to ultimately uncover the mechanisms that underlie virus infection and pathogenesis. Despite the identification of several receptors/attachment molecules for EV71, the binding, entry, and infection mechanisms of EV71 remain unclear. Herein, we employed glycoproteomic approaches to identify human nucleolin as a novel binding receptor for EV71. Glycoproteins purified by lectin chromatography from the membrane extraction of human cells were treated with sialidase, followed by immunoprecipitation with EV71 particles. Among the 16 proteins identified by tandem mass spectrometry analysis, cell surface nucleolin attracted our attention. We found that EV71 interacted directly with nucleolin via the VP1 capsid protein and that an antinucleolin antibody reduced the binding of EV71 to human cells. In addition, the knockdown of cell surface nucleolin decreased EV71 binding, infection, and production in human cells. Furthermore, the expression of human nucleolin on the cell surface of a mouse cell line increased EV71 binding and conferred EV71 infection and production in the cells. These results strongly indicate that human nucleolin can mediate EV71 binding to and infection of cells. Our findings also demonstrate that the use of glycoproteomic approaches is a reliable methodology to discover novel receptors for pathogens. IMPORTANCE: Outbreaks of EV71 have been reported in Asia-Pacific countries and have caused thousands of deaths in young children during the last 2 decades. The discovery of new EV71-interacting molecules to understand the infection mechanism has become an emergent issue. Hence, this study uses glycoproteomic approaches to comprehensively investigate the EV71-interacting glycoproteins. Several EV71-interacting glycoproteins are identified, and the role of cell surface nucleolin in mediating the attachment and entry of EV71 is characterized and validated. Our findings not only indicate a novel target for uncovering the EV71 infection mechanism and anti-EV71 drug discovery but also provide a new strategy for virus receptor identification.

Enterovirus 71 Proteins 2A and 3D Antagonize the Antiviral Activity of Gamma Interferon via Signaling Attenuation.

UNLABELLED: Enterovirus 71 (EV71) infection causes severe mortality involving multiple possible mechanisms, including cytokine storm, brain stem encephalitis, and fulminant pulmonary edema. Gamma interferon (IFN-γ) may confer anti-EV71 activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. This study, investigating the role of IFN-γ in EV71 infection using a murine model, showed that IFN-γ was elevated. Moreover, IFN-γ receptor-deficient mice showed higher mortality rates and more severe disease progression with slower viral clearance than wild-type mice. In vitro results showed that IFN-γ pretreatment reduced EV71 yield, whereas EV71 infection caused IFN-γ resistance with attenuated IFN-γ signaling in IFN regulatory factor 1 (IRF1) gene transactivation. To study the immunoediting ability of EV71 proteins in IFN-γ signaling, 11 viral proteins were stably expressed in cells without cytotoxicity; however, viral proteins 2A and 3D blocked IFN-γ-induced IRF1 transactivation following a loss of signal transducer and activator of transcription 1 (STAT1) nuclear translocation. Viral 3D attenuated IFN-γ signaling accompanied by a STAT1 decrease without interfering with IFN-γ receptor expression. Restoration of STAT1 or blocking 3D activity was able to rescue IFN-γ signaling. Interestingly, viral 2A attenuated IFN-γ signaling using another mechanism by reducing the serine phosphorylation of STAT1 following the inactivation of extracellular signal-regulated kinase without affecting STAT1 expression. These results demonstrate the anti-EV71 ability of IFN-γ and the immunoediting ability by EV71 2A and 3D, which attenuate IFN-γ signaling through different mechanisms. IMPORTANCE: Immunosurveillance by gamma interferon (IFN-γ) may confer anti-enterovirus 71 (anti-EV71) activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. IFN-γ receptor-deficient mice showed higher mortality and more severe disease progression, indicating the anti-EV71 property of IFN-γ. However, EV71 infection caused cellular insusceptibility in response to IFN-γ stimulation. We used an in vitro system with viral protein expression to explore the novel IFN-γ inhibitory properties of the EV71 2A and 3D proteins through the different mechanisms. According to this study, targeting either 2A or 3D pharmacologically and/or genetically may sustain a cellular susceptibility in response to IFN-γ, particularly for IFN-γ-mediated anti-EV71 activity.

Social interaction rescues memory deficit in an animal model of Alzheimer's disease by increasing BDNF-dependent hippocampal neurogenesis.

It has been recognized that the risk of cognitive decline during aging can be reduced if one maintains strong social connections, yet the neural events underlying this beneficial effect have not been rigorously studied. Here, we show that amyloid precursor protein (APP) and presenilin 1 (PS1) double-transgenic (APP/PS1) mice demonstrate improvement in memory after they are cohoused with wild-type mice. The improvement was associated with increased protein and mRNA levels of BDNF in the hippocampus. Concomitantly, the number of BrdU(+)/NeuN(+) cells in the hippocampal dentate gyrus was significantly elevated after cohousing. Methylazoxymethanol acetate, a cell proliferation blocker, markedly reduced BrdU(+) and BrdU/NeuN(+) cells and abolished the effect of social interaction. Selective ablation of mitotic neurons using diphtheria toxin (DT) and a retrovirus vector encoding DT receptor abolished the beneficial effect of cohousing. Knockdown of BDNF by shRNA transfection blocked, whereas overexpression of BDNF mimicked the memory-improving effect. A tropomyosin-related kinase B agonist, 7,8-dihydroxyflavone, occluded the effect of social interaction. These results demonstrate that increased BDNF expression and neurogenesis in the hippocampus after cohousing underlie the reversal of memory deficit in APP/PS1 mice.