Susceptibility of human embryonic stem cell-derived neural cells to Japanese encephalitis virus infection

Noninvasive Imaging of Tumor Glycolysis and Chemotherapeutic Resistance via De Novo Design of Molecular Afterglow Scaffold

Chemotherapeutic resistance poses a significant challenge in cancer treatment, resulting in the reduced efficacy of standard chemotherapeutic agents. Abnormal metabolism, particularly increased anaerobic glycolysis, has been identified as a major contributing factor to chemotherapeutic resistance. To address this issue, noninvasive imaging techniques capable of visualizing tumor glycolysis are crucial. However, the currently available methods (such as PET, MRI, and fluorescence) possess limitations in terms of sensitivity, safety, dynamic imaging capability, and autofluorescence. Here, we present the de novo design of a unique afterglow molecular scaffold based on hemicyanine and rhodamine dyes, which holds promise for low-background optical imaging. In contrast to previous designs, this scaffold exhibits responsive "OFF-ON" afterglow signals through spirocyclization, thus enabling simultaneous control of photodynamic effects and luminescence efficacy. This leads to a larger dynamic range, broader detection range, higher signal enhancement ratio, and higher sensitivity. Furthermore, the integration of multiple functionalities simplifies probe design, eliminates the need for spectral overlap, and enhances reliability. Moreover, we have expanded the applications of this afterglow molecular scaffold by developing various probes for different molecular targets. Notably, we developed a water-soluble pH-responsive afterglow nanoprobe for visualizing glycolysis in living mice. This nanoprobe monitors the effects of glycolytic inhibitors or oxidative phosphorylation inhibitors on tumor glycolysis, providing a valuable tool for evaluating the tumor cell sensitivity to these inhibitors. Therefore, the new afterglow molecular scaffold presents a promising approach for understanding tumor metabolism, monitoring chemotherapeutic resistance, and guiding precision medicine in the future.

Molecular pathogenesis of Japanese encephalitis and possible therapeutic strategies

Japanese encephalitis virus (JEV), a single-stranded, enveloped RNA virus, is a health concern across Asian countries, associated with severe neurological disorders, especially in children. Primarily, pigs, bats, and birds are the natural hosts for JEV, but humans are infected incidentally. JEV requires a few host proteins for its entry and replication inside the mammalian host cell. The endoplasmic reticulum (ER) plays a significant role in JEV genome replication and assembly. During this process, the ER undergoes stress due to its remodelling and accumulation of viral particles and unfolded proteins, leading to an unfolded protein response (UPR). Here, we review the overall strategy used by JEV to infect the host cell and various cytopathic effects caused by JEV infection. We also highlight the role of JEV structural proteins (SPs) and non-structural proteins (NSPs) at various stages of the JEV life cycle that are involved in up- and downregulation of different host proteins and are potentially relevant for developing efficient therapeutic drugs.

Using 2D and 3D pluripotent stem cell models to study neurotropic viruses

Understanding the impact of viral pathogens on the human central nervous system (CNS) has been challenging due to the lack of viable human CNS models for controlled experiments to determine the causal factors underlying pathogenesis. Human embryonic stem cells (ESCs) and, more recently, cellular reprogramming of adult somatic cells to generate human induced pluripotent stem cells (iPSCs) provide opportunities for directed differentiation to neural cells that can be used to evaluate the impact of known and emerging viruses on neural cell types. Pluripotent stem cells (PSCs) can be induced to neural lineages in either two- (2D) or three-dimensional (3D) cultures, each bearing distinct advantages and limitations for modeling viral pathogenesis and evaluating effective therapeutics. Here we review the current state of technology in stem cell-based modeling of the CNS and how these models can be used to determine viral tropism and identify cellular phenotypes to investigate virus-host interactions and facilitate drug screening. We focus on several viruses (e.g., human immunodeficiency virus (HIV), herpes simplex virus (HSV), Zika virus (ZIKV), human cytomegalovirus (HCMV), SARS-CoV-2, West Nile virus (WNV)) to illustrate key advantages, as well as challenges, of PSC-based models. We also discuss how human PSC-based models can be used to evaluate the safety and efficacy of therapeutic drugs by generating data that are complementary to existing preclinical models. Ultimately, these efforts could facilitate the movement towards personalized medicine and provide patients and physicians with an additional source of information to consider when evaluating available treatment strategies.

Dicer and PKR as Novel Regulators of Embryonic Stem Cell Fate and Antiviral Innate Immunity

Embryonic stem cells (ESCs) represent a unique cell population in the blastocyst stage embryo. They have been intensively studied as a promising cell source for regenerative medicine. Recent studies have revealed that both human and mouse ESCs are deficient in expressing IFNs and have attenuated inflammatory responses. Apparently, the ability to express IFNs and respond to certain inflammatory cytokines is not "innate" to ESCs but rather is developmentally acquired by somatic cells during differentiation. Accumulating evidence supports a hypothesis that the attenuated innate immune response may serve as a protective mechanism allowing ESCs to avoid immunological cytotoxicity. This review describes our current understanding of the molecular basis that shapes the immune properties of ESCs. We highlight the recent findings on Dicer and dsRNA-activated protein kinase R as novel regulators of ESC fate and antiviral immunity and discuss how ESCs use alternative mechanisms to accommodate their stem cell properties.

Proteomic analyses identify intracellular targets for Japanese encephalitis virus nonstructural protein 1 (NS1)

Japanese encephalitis is a zoonotic disease caused by Japanese encephalitis virus (JEV). JEV nonstructural protein 1 (NS1) is involved in many crucial biological events during viral infection and immune suppression. To investigate the role of JEV NS1 in virus-infected cells, the molecules with which it interacts intracellularly were screened with a pull-down assay and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The interaction between heterogeneous nuclear ribonucleoprotein K (hnRNP K), vimentin and NS1 were verified with coimmunoprecipitation and confocal assays. Our results show that JEV NS1 interacts with vimentin, hnRNP K and colocalizes with cellular vimentin and hnRNP K. Furthermore, our results demonstrate that the expression of vimentin and hnRNP K were up-regulated in both NS1-transfected and JEV-infected cells. Knocking down vimentin and hnRNP K reduced viral replication while conversely, over-expression of vimentin and hnRNP K improved viral replication, suggesting an important role for this protein in the viral life cycle. Also, We found that vimentin also interacted with hnRNP K after overexpression of NS1 or JEV infection. These findings provide insight into the molecular mechanism of JEV replication and highlight the key role the NS1 in JEV infection.

Farr R, Green D, M. Haynes J, Bingham J, O’Brien CM, Dearnley M. Modelling Lyssavirus Infections in Human Stem Cell-Derived Neural Cultures

Rabies is a zoonotic neurological infection caused by lyssavirus that continues to result in devastating loss of human life. Many aspects of rabies pathogenesis in human neurons are not well understood. Lack of appropriate ex-vivo models for studying rabies infection in human neurons has contributed to this knowledge gap. In this study, we utilize advances in stem cell technology to characterize rabies infection in human stem cell-derived neurons. We show key cellular features of rabies infection in our human neural cultures, including upregulation of inflammatory chemokines, lack of neuronal apoptosis, and axonal transmission of viruses in neuronal networks. In addition, we highlight specific differences in cellular pathogenesis between laboratory-adapted and field strain lyssavirus. This study therefore defines the first stem cell-derived ex-vivo model system to study rabies pathogenesis in human neurons. This new model system demonstrates the potential for enabling an increased understanding of molecular mechanisms in human rabies, which could lead to improved control methods.

NF-κB Activation Promotes Alphavirus Replication in Mature Neurons

Alphaviruses are enveloped, positive-sense RNA viruses that are important causes of viral encephalomyelitis. Sindbis virus (SINV) infects the neurons of rodents and is a model for studying factors that regulate infection of neuronal cells. The outcome of alphavirus infection of the central nervous system is dependent on neuronal maturation status. Differentiated mature neurons survive and control viral replication better than undifferentiated immature neurons. The cellular factors involved in age-dependent susceptibility include higher levels of antiapoptotic and innate immune factors in mature neurons. Because NF-κB pathway activation is required for the initiation of both apoptosis and the host antiviral response, we analyzed the role of NF-κB during SINV infection of differentiated and undifferentiated rat neuronal cells. SINV infection induced canonical NF-κB activation, as evidenced by the degradation of IκBα and the phosphorylation and nuclear translocation of p65. Inhibition or deletion of the upstream IκB kinase substantially reduced SINV replication in differentiated but not in undifferentiated neuronal cells or mouse embryo fibroblasts. NF-κB inhibition did not affect the establishment of infection, replication complex formation, the synthesis of nonstructural proteins, or viral RNA synthesis in differentiated neurons. However, the translation of structural proteins was impaired, phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α) was decreased, and host protein synthesis was maintained, suggesting that NF-κB activation was involved in the regulation of translation during infection of mature neurons. Inhibition or deletion of double-stranded RNA-activated protein kinase (PKR) also decreased eIF2α phosphorylation, the translation of viral structural proteins, and virus production. Therefore, canonical NF-κB activation synergizes with PKR to promote SINV replication in differentiated neurons by facilitating viral structural protein translation.IMPORTANCE Mosquito-borne alphaviruses are a significant and growing cause of viral encephalomyelitis worldwide. The outcome of alphaviral neuronal infections is host age dependent and greatly affected by neuronal maturation status, with differentiated, mature neurons being more resistant to infection than undifferentiated, immature neurons. The biological factors that change during neuronal maturation and that influence the outcome of viral infection are currently only partially defined. These studies investigated the role of NF-κB in determining the outcome of alphaviral infection in mature and immature neurons. Inhibition of canonical NF-κB activation decreased alphavirus replication in mature neurons by regulating protein synthesis and limiting the production of the viral structural proteins but had little effect on viral replication in immature neurons or fibroblasts. Therefore, NF-κB is a signaling pathway that influences the maturation-dependent outcome of alphaviral infection in neurons and that highlights the importance of cellular context in determining the effects of signal pathway activation.

NanoCsA improves the survival of human iPSC transplant in hemiparkinsonian rats

Increasing evidence has supported that transplantation of human stem cells induces neuroprotective and reparative effects in animal models of Parkinson's disease (PD). However, without systemic immunosuppressive therapy, most of these grafted cells are rejected by the hosts. Long term and systemic injection of cyclosporine-A (CsA) is required to maintain the survival of grafted cells. The purpose this study is to examine a new treatment strategy to suppress the immunorejection by locally co-grafting of polylactic/glycolic acid nanoparticles containing CsA (NanoCsA) with differentiated human induced pluripotent stem cells (iPSCs). In the in vitro media, NanoCsA provided sustained release of CsA for >6 weeks. The differentiated human iPSCs were co-grafted with NanoCsA or NanoVeh (nanoparticle without CsA) to the striatum of unilaterally 6-hydroxydopamine -lesioned rats. NanoCsA/iPSCs co-graft significantly improved locomotor activity compared to NanoVeh/iPSCs co-grafts or iPSC grafts + sytemic CsA at 1 month after transplantation. Brain tissues were collected for measurements of tyrosine hydroxylase (TH) and human marker Stem121 immunoreactivity. Cografting with NanoCsA/iPSCs, compared to NanoVeh/iPSCs, significantly increased TH and Stem121 immunoreactivity as well as tumor formation in the lesioned striatum. Taken together, our study supports that NanoCsA provides long-lasting CsA release and reduces immunorejection of human iPSCs xenograft in a 6-hydroxydopamine rat model of PD.

Differential antiviral immunity to Japanese encephalitis virus in developing cortical organoids

Japanese encephalitis (JE) caused by Japanese encephalitis virus (JEV) poses a serious threat to the world’s public health yet without a cure. Certain JEV-infected neural cells express a subset of previously identified intrinsic antiviral interferon stimulated genes (ISGs), indicating brain cells retain autonomous antiviral immunity. However, whether this happens in composited brain remains unclear. Human pluripotent stem cell (hPSC)-derived organoids can model disorders caused by human endemic pathogens such as Zika virus, which may potentially address this question and facilitate the discovery of a cure for JE. We thus generated telencephalon organoid and infected them with JEV. We found JEV infection caused significant decline of cell proliferation and increase of cell death in brain organoid, resulting in smaller organoid spheres. JEV tended to infect astrocytes and neural progenitors, especially the population representing outer radial glial cells (oRGCs) of developing human brain. In addition, we revealed variable antiviral immunity in brain organoids of different stages of culture. In organoids of longer culture (older than 8 weeks), but not of early ones (less than 4 weeks), JEV infection caused typical activation of interferon signaling pathway. Preferential infection of oRGCs and differential antiviral response at various stages might explain the much more severe outcomes of JEV infection in the younger, which also provide clues to develop effective therapeutics of such diseases.

miR-16-1 expression, heat shock protein 70 and inflammatory reactions in astrocytes of mice with epilepsy induced by encephalitis B virus infection

The upregulation of miR-16-1 expression and heat shock protein 70 (HSP70) and inflammatory reaction mechanism in astrocytes of mice with epilepsy induced by encephalitis B virus infection were studied. Six-to-eight-week-old healthy male C57BL/6 mice received intraperitoneal injection of pilocarpine (320-340 mg/kg, 40 mg/ml) to induce status epilepsy. After 7 days, mice were inoculated with 100 µl Dulbecco's modified Eagle's medium (DMEM) in the neck, including 6.25×23 PFU Japanese encephalitis virus P3 wild strain. The experiment was divided into 4 groups, including, the healthy control group, the epilepsy model group, the model group + negative inoculation group and the virus infection group with 10 mice in each group. The healthy control group received intraperitoneal injection of the same amount of normal saline; the model group + negative inoculation group was injected with the same amount of DMEM without P3. One and three days after infection, 5 mice from each group were sacrificed, hippocampus tissues were obtained and astrocytes were isolated. After purification, glial fibrillary acidic protein was identified by immunohistochemical staining. Infected glial cells were detected by P3 antigen of immunofluorescence staining. RT-PCR method was used to detect the expression of miR-16-1 mRNA in astrocytes. Western blot analysis was used to detect the expression of HSP70. ELISA method was used to detect the levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α and nuclear factor-κB (NF-κB) inflammatory factors in tail vein blood. Level of expression of miR-16-1 mRNA, HSP70 as well as IL-6, TNF-α and NF-κB inflammatory factor levels of virus infected mice of 1 and 3 days were significantly higher (P<0.05) than those of model group and negative inoculation group and lowest in control group. In conclusion, the level of expression of miR-16-1 and HSP70 can be increased by the infection of Japanese encephalitis virus on the astrocytes of mice with epilepsy, to promote the expression of IL-6, TNF-α and NF-κB of inflammatory factors.

Zika virus tropism and interactions in myelinating neural cell cultures: CNS cells and myelin are preferentially affected

The recent global outbreak of Zika virus (ZIKV) infection has been linked to severe neurological disorders affecting the peripheral and central nervous systems (PNS and CNS, respectively). The pathobiology underlying these diverse clinical phenotypes are the subject of intense research; however, even the principal neural cell types vulnerable to productive Zika infection remain poorly characterised. Here we used CNS and PNS myelinating cultures from wild type and Ifnar1 knockout mice to examine neuronal and glial tropism and short-term consequences of direct infection with a Brazilian variant of ZIKV. Cell cultures were infected pre- or post-myelination for various intervals, then stained with cell-type and ZIKV-specific antibodies. In bypassing systemic immunity using ex vivo culture, and the type I interferon response in Ifnar1 deficient cells, we were able to evaluate the intrinsic infectivity of neural cells. Through systematic quantification of ZIKV infected cells in myelinating cultures, we found that ZIKV infection is enhanced in the absence of the type I interferon responses and that CNS cells are considerably more susceptible to infection than PNS cells. In particular, we demonstrate that CNS axons and myelinating oligodendrocytes are especially vulnerable to injury. These results have implications for understanding the pathobiology of neurological symptoms associated with ZIKV infection. Furthermore, we provide a quantifiable ex vivo infection model that can be used for fundamental and therapeutic studies on viral neuroinvasion and its consequences.

Susceptibility of naïve and differentiated PC12 cells to Japanese encephalitis virus infection

Japanese encephalitis is a mosquito-borne disease caused by Japanese encephalitis virus (JEV) infection. Although JEV infects and replicates in cells with multiple tissue origins, neurons are the preferential cells for JEV infection. Currently, the identities of JEV cell tropism are largely unclear. To gain better insight into the underlying identities of JEV cell tropism, this study was designed to compare the JEV cell tropism with naïve or differentiated PC12 cells. Through nerve growth factor-differentiated PC12 cells, we discovered that JEV efficiently replicated in differentiated PC12 cells rather than naïve cells. Mechanistic studies revealed that viral adsorption/attachment seemed not to be a crucial factor. Supporting data showed that antagonizing postreceptor intracellular signaling of interferons, along with the activation of suppressor of cytokine signaling-3 (SOCS3) expression and protein tyrosine phosphatase activity, were apparent in differentiated PC12 cells after JEV infection. Independent of differentiating inducing agents, the upregulation of SOCS3 expression and protein tyrosine phosphatase activity, as well as preferential JEV tropism, were common in JEV-infected differentiated PC12 cells. Using cultured primary neurons, JEV efficiently replicated in embryonic neurons rather than adult neurons, and the preference was accompanied by higher SOCS3 expression and protein tyrosine phosphatase activity. Given that both SOCS3 and protein tyrosine phosphatases have been implicated in the process of neuronal differentiation, JEV infection seems to not only create an antagonizing strategy to escape host's interferon antiviral response but also takes advantage of cellular machinery to favor its replication. Taken together, current findings imply that dynamic changes within cellular regulators of antiviral machinery could be accompanied by events of neuronal differentiation, thus concurrently playing roles in the control of JEV cell tropism and replication. © 2017 IUBMB Life, 69(2):79-87, 2017.