Junction adhesion molecule is a receptor for reovirus

NRP1 is a receptor for mammalian orthoreovirus engaged by distinct capsid subunits

Mammalian orthoreovirus (reovirus) is a nonenveloped virus that establishes primary infection in the intestine and disseminates to sites of secondary infection, including the CNS. Reovirus entry involves multiple engagement factors, but how the virus disseminates systemically and targets neurons remains unclear. In this study, we identified murine neuropilin 1 (mNRP1) as a receptor for reovirus. mNRP1 binds reovirus with nanomolar affinity using a unique mechanism of virus-receptor interaction, which is coordinated by multiple interactions between distinct reovirus capsid subunits and multiple NRP1 extracellular domains. By exchanging essential capsid protein-encoding gene segments, we determined that the multivalent interaction is mediated by outer-capsid protein σ3 and capsid turret protein λ2. Using capsid mutants incapable of binding NRP1, we found that NRP1 contributes to reovirus dissemination and neurovirulence in mice. Collectively, our results demonstrate that NRP1 is an entry receptor for reovirus and uncover mechanisms by which NRPs promote viral entry and pathogenesis.

Evaluating a combination treatment of NK cells and reovirus against bladder cancer cells using an in vitro assay to simulate intravesical therapy

Intravesical treatment using either reovirus or natural killer (NK) cells serves as an efficient strategy for the treatment of bladder cancer cells (BCCs); however, corresponding monotherapies have often shown modest cytotoxicity. The potential of a locoregional combination using high-dose reovirus and NK cell therapy in an intravesical approach has not yet been studied. In this study, we evaluated the effectiveness of reoviruses and expanded NK cells (eNK) as potential strategies for the treatment of bladder cancer. The anti-tumor effects of mono-treatment with reovirus type 3 Dearing strain (RC402 and RP116) and in combination with interleukin (IL)-18/-21-pretreated eNK cells were investigated on BCC lines (5637, HT-1376, and 253J-BV) using intravesical therapy to simulate in vitro model. RP116 and IL-18/-21-pretreated eNK cells exhibited effective cytotoxicity against grade 1 carcinoma (5637 cells) when used alone, but not against HT-1376 (grade 2 carcinoma) and 253J-BV cells (derived from a metastatic site). Notably, combining RP116 with IL-18/-21-pretreated eNK cells displayed effective cytotoxicity against both HT-1376 and 253J-BV cells. Our findings underscore the potential of a combination therapy using reoviruses and NK cells as a promising strategy for treating bladder cancer.

Cytocidal Effect of Irradiation on Gastric Cancer Cells Infected with a Recombinant Mammalian Orthoreovirus Expressing a Membrane-Targeted KillerRed

The outcomes of unresectable gastric cancer (GC) are unfavorable even with chemotherapy; therefore, a new treatment modality is required. The combination of an oncolytic virus and photodynamic therapy can be one of the promising modalities to overcome this. Mammalian orthoreovirus (MRV) is an oncolytic virus that has been used in clinical trials for several cancers. In this study, we developed and evaluated a recombinant MRV strain type 3 Dearing (T3D) that expresses membrane-targeting KillerRed (KRmem), a phototoxic fluorescent protein that produces cytotoxic reactive oxygen species upon light irradiation. KRmem was fused in-frame to the 3' end of the σ2 viral gene in the S2 segment using a 2A peptide linker, enabling the expression of multiple proteins from a single transcript. RNA electrophoresis, Western blotting, and immunofluorescence analyses confirmed functional insertion of KRmem into the recombinant virus. The growth activity of the recombinant virus was comparable to that of the wild-type MRV in a cultured cell line. The recombinant virus infected two GC cell lines (MKN45P and MKN7), and a significant cytocidal effect was observed in MKN45P cells infected with the recombinant virus after light irradiation. Thus, recombinant MRV-expressing KRmem has the potential to serve as a novel treatment tool for GC.

Proteasome activity is required for reovirus entry into cells

IMPORTANCE

Due to their limited genetic capacity, viruses are reliant on multiple host systems to replicate successfully. Mammalian orthoreovirus (reovirus) is commonly used as a model system for understanding host-virus interactions. In this study, we identify that the proteasome system, which is critical for cellular protein turnover, affects reovirus entry. Inhibition of the proteasome using a chemical inhibitor blocks reovirus uncoating. Blocking these events reduces subsequent replication of the virus. This work identifies that additional host factors control reovirus entry.

Creation and characterization of a recombinant mammalian orthoreovirus expressing σ1 fusion proteins encoding human epidermal growth factor receptor 2 peptides

Mammalian orthoreovirus (MRV) is an oncolytic virus that has been tested in over 30 clinical trials. Increased clinical success has been achieved when MRV is used in combination with other onco-immunotherapies. This has led the field to explore the creation of recombinant MRVs which incorporate immunotherapeutic sequences into the virus genome. This work focuses on creation and characterization of a recombinant MRV, S1/HER2nhd, which encodes a truncated σ1 protein fused in frame with three human epidermal growth factor receptor 2 (HER2) peptides (E75, AE36, and GP2) known to induce HER2 specific CD8+ and CD4+ T cells. We show S1/HER2nhd expresses the σ1 fusion protein containing HER2 peptides in infected cells and on the virion, and infects, replicates in, and reduces survival of HER2+ breast cancer cells. The oncolytic properties of MRV combined with HER2 peptide expression holds potential as a vaccine to prevent recurrences of HER2 expressing cancers.

GB Virus B and Hepatitis C Virus, Distantly Related Hepaciviruses, Share an Entry Factor, Claudin-1

Due to increased and broadened screening efforts, the last decade has seen a rapid expansion in the number of viral species classified into the Hepacivirus genus. Conserved genetic features of hepaciviruses suggest that they have undergone specific adaptation and have evolved to hijack similar host proteins for efficient propagation in the liver. Here, we developed pseudotyped viruses to elucidate the entry factors of GB virus B (GBV-B), the first hepacivirus described in an animal after hepatitis C virus (HCV). GBV-B-pseudotyped viral particles (GBVBpp) were shown to be uniquely sensitive to the sera of tamarins infected with GBV-B, validating their usefulness as a surrogate for GBV-B entry studies. We screened GBVBpp infection of human hepatoma cell lines that were CRISPR/Cas9 engineered to ablate the expression of individual HCV receptors/entry factors and found that claudin-1 is essential for GBV-B infection, indicating the GBV-B and HCV share an entry factor. Our data suggest that claudin-1 facilitates HCV and GBV-B entry through distinct mechanisms since the former requires the first extracellular loop and the latter is reliant on a C-terminal region containing the second extracellular loop. The observation that claudin-1 is an entry factor shared between these two hepaciviruses suggests that the tight junction protein is of fundamental mechanistic importance during cell entry. IMPORTANCE Hepatitis C virus (HCV) is a major public health burden; approximately 58 million individuals have chronic HCV infection and are at risk of developing cirrhosis and liver cancer. To achieve the World Health Organization's target of eliminating hepatitis by 2030, new therapeutics and vaccines are needed. Understanding how HCV enters cells can inform the design of new vaccines and treatments targeting the first stage of infection. However, the HCV cell entry mechanism is complex and has been sparsely described. Studying the entry of related hepaciviruses will increase the knowledge of the molecular mechanisms of the first stages of HCV infection, such as membrane fusion, and inform structure-guided HCV vaccine design; in this work, we have identified a protein, claudin-1, that facilitates the entry of an HCV-related hepacivirus but with a mechanism not described for HCV. Similar work on other hepaciviruses may unveil a commonality of entry factors and, possibly, new mechanisms.

Modulation of Reoviral Cytolysis (II): Cellular Stemness

Oncolytic viruses (OVs) are an emerging cancer therapeutic that are intended to act by selectively targeting and lysing cancerous cells and by stimulating anti-tumour immune responses, while leaving normal cells mainly unaffected. Reovirus is a well-studied OV that is undergoing advanced clinical trials and has received FDA approval in selected circumstances. However, the mechanisms governing reoviral selectivity are not well characterised despite many years of effort, including those in our accompanying paper where we characterize pathways that do not consistently modulate reoviral cytolysis. We have earlier shown that reovirus is capable of infecting and lysing both certain types of cancer cells and also cancer stem cells, and here we demonstrate its ability to also infect and kill healthy pluripotent stem cells (PSCs). This led us to hypothesize that pathways responsible for stemness may constitute a novel route for the modulation of reoviral tropism. We find that reovirus is capable of killing both murine and human embryonic and induced pluripotent stem cells. Differentiation of PSCs alters the cells' reoviral-permissive state to a resistant one. In a breast cancer cell line that was resistant to reoviral oncolysis, induction of pluripotency programming rendered the cells permissive to cytolysis. Bioinformatic analysis indicates that expression of the Yamanaka pluripotency factors may be associated with regulating reoviral selectivity. Mechanistic insights from these studies will be useful for the advancement of reoviral oncolytic therapy.

Modulation of Reoviral Cytolysis (I): Combination Therapeutics

Patients with stage IV gastric cancer suffer from dismal outcomes, a challenge especially in many Asian populations and for which new therapeutic options are needed. To explore this issue, we used oncolytic reovirus in combination with currently used chemotherapeutic drugs (irinotecan, paclitaxel, and docetaxel) for the treatment of gastric and other gastrointestinal cancer cells in vitro and in a mouse model. Cell viability in vitro was quantified by WST-1 assays in human cancer cell lines treated with reovirus and/or chemotherapeutic agents. The expression of reovirus protein and caspase activity was determined by flow cytometry. For in vivo studies, athymic mice received intratumoral injections of reovirus in combination with irinotecan or paclitaxel, after which tumor size was monitored. In contrast to expectations, we found that reoviral oncolysis was only poorly correlated with Ras pathway activation. Even so, the combination of reovirus with chemotherapeutic agents showed synergistic cytopathic effects in vitro, plus enhanced reovirus replication and apoptosis. In vivo experiments showed that reovirus alone can reduce tumor size and that the combination of reovirus with chemotherapeutic agents enhances this effect. Thus, we find that oncolytic reovirus therapy is effective against gastric cancer. Moreover, the combination of reovirus and chemotherapeutic agents synergistically enhanced cytotoxicity in human gastric cancer cell lines in vitro and in vivo. Our data support the use of reovirus in combination with chemotherapy in further clinical trials, and highlight the need for better biomarkers for reoviral oncolytic responsiveness.

NgR1 binding to reovirus reveals an unusual bivalent interaction and a new viral attachment protein

Nogo-66 receptor 1 (NgR1) binds a variety of structurally dissimilar ligands in the adult central nervous system to inhibit axon extension. Disruption of ligand binding to NgR1 and subsequent signaling can improve neuron outgrowth, making NgR1 an important therapeutic target for diverse neurological conditions such as spinal crush injuries and Alzheimer's disease. Human NgR1 serves as a receptor for mammalian orthoreovirus (reovirus), but the mechanism of virus-receptor engagement is unknown. To elucidate how NgR1 mediates cell binding and entry of reovirus, we defined the affinity of interaction between virus and receptor, determined the structure of the virus-receptor complex, and identified residues in the receptor required for virus binding and infection. These studies revealed that central NgR1 surfaces form a bridge between two copies of viral capsid protein σ3, establishing that σ3 serves as a receptor ligand for reovirus. This unusual binding interface produces high-avidity interactions between virus and receptor to prime early entry steps. These studies refine models of reovirus cell-attachment and highlight the evolution of viruses to engage multiple receptors using distinct capsid components.

The Reovirus σ1 Attachment Protein Influences the Stability of Its Entry Intermediate

Structural metastability of viral capsids is pivotal for viruses to survive in harsh environments and to undergo timely conformational changes required for cell entry. Mammalian orthoreovirus (reovirus) is a model to study capsid metastability. Following initial disassembly of the reovirus particle mediated by proteases, a metastable intermediate called the infectious subvirion particle (ISVP) is generated. Using a σ1 monoreassortant virus, we recently showed that σ1 properties affect its encapsidation on particles and the metastability of ISVPs. How metastability is impacted by σ1 and whether the lower encapsidation level of σ1 is connected to this property is unknown. To define a correlation between encapsidation of σ1 and ISVP stability, we generated mutant viruses with single amino acid polymorphisms in σ1 or those that contain chimeric σ1 molecules composed of σ1 portions from type 1 and type 3 reovirus strains. We found that under most conditions where σ1 encapsidation on the particle was lower, ISVPs displayed lower stability. Characterization of mutant viruses selected for enhanced stability via a forward genetic approach also revealed that in some cases, σ1 properties influence stability without influencing σ1 encapsidation. These data indicate that σ1 can also influence ISVP stability independent of its level of incorporation. Together, our work reveals an underappreciated effect of the σ1 attachment protein on the properties of the reovirus capsid. IMPORTANCE Reovirus particles are comprised of eight proteins. Among them, the reovirus σ1 protein functions engages cellular receptors. σ1 also influences the stability of an entry intermediate called ISVP. Here, we sought to define the basis of the link between σ1 properties and stability of ISVPs. Using variety of mutant strains, we determined that when virus preparations contain particles with a high amount of encapsidated σ1, ISVP stability is higher. Additionally, we identified portions of σ1 that impact its encapsidation and consequently the stability of ISVPs. We also determined that in some cases, σ1 properties alter stability of ISVPs without affecting encapsidation. This work highlights that proteins of these complex particles are arranged in an intricate, interconnected manner such that changing the properties of these proteins has a profound impact on the remainder of the particle.

Deciphering molecular mechanisms stabilizing the reovirus-binding complex

Mammalian orthoreoviruses (reoviruses) serve as potential triggers of celiac disease and have oncolytic properties, making these viruses potential cancer therapeutics. Primary attachment of reovirus to host cells is mainly mediated by the trimeric viral protein, σ1, which engages cell-surface glycans, followed by high-affinity binding to junctional adhesion molecule-A (JAM-A). This multistep process is thought to be accompanied by major conformational changes in σ1, but direct evidence is lacking. By combining biophysical, molecular, and simulation approaches, we define how viral capsid protein mechanics influence virus-binding capacity and infectivity. Single-virus force spectroscopy experiments corroborated by in silico simulations show that GM2 increases the affinity of σ1 for JAM-A by providing a more stable contact interface. We demonstrate that conformational changes in σ1 that lead to an extended rigid conformation also significantly increase avidity for JAM-A. Although its associated lower flexibility impairs multivalent cell attachment, our findings suggest that diminished σ1 flexibility enhances infectivity, indicating that fine-tuning of σ1 conformational changes is required to successfully initiate infection. Understanding properties underlying the nanomechanics of viral attachment proteins offers perspectives in the development of antiviral drugs and improved oncolytic vectors.

Paired immunoglobulin-like receptor B is an entry receptor for mammalian orthoreovirus

Mammalian orthoreovirus (reovirus) infects most mammals and is associated with celiac disease in humans. In mice, reovirus infects the intestine and disseminates systemically to cause serotype-specific patterns of disease in the brain. To identify receptors conferring reovirus serotype-dependent neuropathogenesis, we conducted a genome-wide CRISPRa screen and identified paired immunoglobulin-like receptor B (PirB) as a receptor candidate. Ectopic expression of PirB allowed reovirus binding and infection. PirB extracelluar D3D4 region is required for reovirus attachment and infectivity. Reovirus binds to PirB with nM affinity as determined by single molecule force spectroscopy. Efficient reovirus endocytosis requires PirB signaling motifs. In inoculated mice, PirB is required for maximal replication in the brain and full neuropathogenicity of neurotropic serotype 3 (T3) reovirus. In primary cortical neurons, PirB expression contributes to T3 reovirus infectivity. Thus, PirB is an entry receptor for reovirus and contributes to T3 reovirus replication and pathogenesis in the murine brain.

Oncolytic Reoviruses: Can These Emerging Zoonotic Reoviruses Be Tamed and Utilized?

Orthoreovirus is a nonenveloped double-stranded RNA virus under the Reoviridae family. This group of viruses, especially mammalian orthoreovirus (MRV), are reported with great therapeutic values due to their oncolytic effects. In this review, the life cycle and oncolytic effect of MRV and a few emerging reoviruses were summarized. This article also highlights the challenges and strategies of utilizing MRV and the emerging reoviruses, avian orthoreovirus (ARV) and pteropine orthoreovirus (PRV), as oncolytic viruses (OVs). Besides, the emergence of potential ARV and PRV as OVs were discussed in comparison to MRV. Finally, the risk of reovirus as zoonosis or reverse zoonosis (zooanthroponosis) were debated, and concerns were raised in this article, which warrant continue surveillance of reovirus (MRV, ARV, and PRV) in animals, humans, and the environment.

p38 Mitogen-Activated Protein Kinase Signaling Enhances Reovirus Replication by Facilitating Efficient Virus Entry, Capsid Uncoating, and Postuncoating Steps

Mammalian orthoreovirus serotype 3 Dearing is an oncolytic virus currently undergoing multiple clinical trials as a potential cancer therapy. Previous clinical trials have emphasized the importance of prescreening patients for prognostic markers to improve therapeutic success. However, only generic cancer markers such as epidermal growth factor receptor (EGFR), Hras, Kras, Nras, Braf, and p53 are currently utilized, with limited benefit in predicting therapeutic efficacy. This study aimed to investigate the role of p38 mitogen-activated protein kinase (MAPK) signaling during reovirus infection. Using a panel of specific p38 MAPK inhibitors and an inactive inhibitor analogue, p38 MAPK signaling was found to be essential for establishment of reovirus infection by enhancing reovirus endocytosis, facilitating efficient reovirus uncoating at the endo-lysosomal stage, and augmenting postuncoating replication steps. Using a broad panel of human breast cancer cell lines, susceptibility to reovirus infection corresponded with virus binding and uncoating efficiency, which strongly correlated with status of the p38β isoform. Together, results suggest p38β isoform as a potential prognostic marker for early stages of reovirus infection that are crucial to successful reovirus infection. IMPORTANCE The use of Pelareorep (mammalian orthoreovirus) as a therapy for metastatic breast cancer has shown promising results in recent clinical trials. However, the selection of prognostic markers to stratify patients has had limited success due to the fact that these markers are upstream receptors and signaling pathways that are present in a high percentage of cancers. This study demonstrates that the mechanism of action of p38 MAPK signaling plays a key role in establishment of reovirus infection at both early entry and late replication steps. Using a panel of breast cancer cell lines, we found that the expression levels of the MAPK11 (p38β) isoform are a strong determinant of reovirus uncoating and infection establishment. Our findings suggest that selecting prognostic markers that target key steps in reovirus replication may improve patient stratification during oncolytic reovirus therapy.

Gain of function studies on predicted host receptors for white spot virus

Three decades after its first outbreak, the shrimp white spot virus (WSV) is still a global cause of concern due to considerable losses and lack of effective control measures. Several candidate host receptor proteins have been identified, but the pathogenesis is not clearly understood, although the key role of the WSV envelope protein VP28 in virus internalization is established. Here, protein-protein docking is applied to evaluate the interaction of VP28 trimeric extracellular region with four host (Penaeus monodon) receptors reported earlier, Rab7 GTPase (PmRab7), glucose transporter 1 (PmGLUT1), C-type lectin (PmCTL) and calreticulin (PmCRT). The stability of predicted complexes evaluated in terms of binding energy per unit buried surface area ranged from -8.46 to -11.82 cal mol^-1/Ų, which is not sufficient for functional interaction. Nevertheless, each of these host proteins was tested by a gain-of-function approach by observing their ability to make a fish cell line permissive to the shrimp WSV. Full-length expression constructs of the four receptors were transfected into SSN1 snakehead fish cells that are non-permissive to WSV. Transfected SSN1 cells and WSV permissive insect Sf9 cells were challenged with purified WSV. After 24 h, the presence of receptor transcripts was confirmed in the treated SSN1 cells, and not in the non-transfected SSN1 cells. Further, vp28 transcript was detected in Sf9 cells, but not in any of the treated SSN1 cells, indicating that none of the receptors were singly sufficient to make SSN1 cells permissive to WSV, even though PmRab7 was a strong candidate that alone showed >85% protection in virus neutralization experiments. For the other 3 candidates, previous reports predicted the involvement of co-receptors, which is confirmed here by their inability to act singly.

Analysis of the Immune Response and Identification of Antibody Epitopes Against the Sigma C Protein of Avian Orthoreovirus Following Immunization with Live or Inactivated Vaccines

Avian orthoreoviruses are causative agents of tenosynovitis and viral arthritis in both chickens and turkeys. Current commercial reovirus vaccines do not protect against disease caused by emerging variants. Custom-made inactivated reovirus vaccines are commonly utilized to help protect commercial poultry against disease. Antibody epitopes located on the viral attachment protein, σC, involved in virus neutralization, have not been clearly identified. In this study, the S1133 vaccine strain (Genetic Cluster 1 [GC1], a GC1 field isolate (117816), and a GC5 field isolate (94826) were determined to be genetically and serologically unrelated. In addition, chickens were vaccinated with either a commercial S1133 vaccine, 117816 GC1, or 94826 GC5, and sera were used in peptide microarrays to identify linear B-cell epitopes within the σC protein. Specific-pathogen-free (SPF) chickens were vaccinated twice with either: 1) live and live, 2) inactivated and inactivated, or 3) a combination of live and inactivated vaccines. Epitope mapping was performed on individual serum samples from birds in each group using S1133, 117816, and 94826 σC sequences translated into an overlapping peptides and spotted onto microarray chips. Vaccination with a combination of live and inactivated viruses resulted in a greater number of B-cell binding sites on the outer-capsid domains of σC for 117816 and 94826, but not for S1133. In contrast, the S1133-vaccinated birds demonstrated fewer epitopes, and those epitopes were located in the stalk region of the protein. However, within each of the vaccinated groups, the highest virus-neutralization titers were observed in the live/inactivated groups. This study demonstrates differences in antibody binding sites within σC between genetically and antigenically distinct reoviruses and provides initial antigenic characterization of avian orthoreoviruses and insight into the inability of vaccine-induced antibodies to provide adequate protection against variant reovirus-induced disease.

Junctional complexes in epithelial cells: sentinels for extracellular insults and intracellular homeostasis

The cell-cell and cell-ECM junctions within the epithelial tissues are crucial anchoring structures that provide architectural stability, mechanical resistance, and permeability control. Their indispensable role as signaling hubs orchestrating cell shape-related changes such as proliferation, differentiation, migration, and apoptosis has also been well recognized. However, growing amount of evidence now suggests that the multitasking nature of epithelial junctions extends well beyond anchorage-dependent or cell shape change-related biological processes. In this review, we discuss the emerging roles of junctional complexes in regulating innate immune defense, stress resistance, and intracellular proteostasis of the epithelial cells, with emphasis on the upstream regulation of epithelial junctions on various aspects of the epithelial barrier.

Review of Viral Arthritis in Canada

Viral arthritis/tenosynovitis, a disease caused by avian reovirus (ARV), leads to great economic losses for the chicken industry worldwide. Since autumn 2011, the poultry industries in the United States and Canada have sustained significant economic losses in the progeny of broiler breeders vaccinated with classic strains of ARV. Vaccination failure has been caused by field challenge with variant ARVs. The variant field ARVs are refractory to the immunity stimulated by classic vaccines and have become the prevalent challenge in the field. Because all genotypes described in the literature have been reported to be circulating in Canada, genotyping of circulating ARVs is paramount for the selection of appropriate isolates, representative of the field challenge, for use in autogenous vaccines. In this review, the history of ARVs and the current situation in Canada are discussed. On the basis of recent field data, inadequate measures commonly used in the field are discussed, and successful vaccination strategies are recommended.

Transcriptional and Post-Translational Regulation of Junctional Adhesion Molecule-B (JAM-B) in Leukocytes under Inflammatory Stimuli

Junctional adhesion molecules (JAMs; comprising JAM-A, -B and -C) act as receptors for viruses, mediate cell permeability, facilitate leukocyte migration during sterile and non-sterile inflammation and are important for the maintenance of epithelial barrier integrity. As such, they are implicated in the development of both communicable and non-communicable chronic diseases. Here, we investigated the expression and regulation of JAM-B in leukocytes under pathogen- and host-derived inflammatory stimuli using immunoassays, qPCR and pharmacological inhibitors of inflammatory signalling pathways. We show that JAM-B is expressed at both the mRNA and protein level in leukocytes. JAM-B protein is localised to the cytoplasm, Golgi apparatus and in the nucleus around ring-shaped structures. We also provide evidence that JAM-B nuclear localisation occurs via the classical importin-α/β pathway, which is likely mediated through JAM-B protein nuclear localisation signals (NLS) and export signals (NES). In addition, we provide evidence that under both pathogen- and host-derived inflammatory stimuli, JAM-B transcription is regulated via the NF-κB-dependent pathways, whereas at the post-translational level JAM-B is regulated by ubiquitin-proteosome pathways. Anaphase-promoting ubiquitin ligase complex (APC/C) and herpes simplex virus-associated ubiquitin-specific protease (HAUSP/USP) were identified as candidates for JAM-B ubiquitination and de-ubiquitination, respectively. The expression and regulation of JAM-B in leukocytes reported here is a novel observation and contrasts with previous reports. The data reported here suggest that JAM-B expression in leukocytes is under the control of common inflammatory pathways.

Reovirus Activated Cell Death Pathways

Mammalian orthoreoviruses (ReoV) are non-enveloped viruses with segmented double-stranded RNA genomes. In humans, ReoV are generally considered non-pathogenic, although members of this family have been proven to cause mild gastroenteritis in young children and may contribute to the development of inflammatory conditions, including Celiac disease. Because of its low pathogenic potential and its ability to efficiently infect and kill transformed cells, the ReoV strain Type 3 Dearing (T3D) is clinical trials as an oncolytic agent. ReoV manifests its oncolytic effects in large part by infecting tumor cells and activating programmed cell death pathways (PCDs). It was previously believed that apoptosis was the dominant PCD pathway triggered by ReoV infection. However, new studies suggest that ReoV also activates other PCD pathways, such as autophagy, pyroptosis, and necroptosis. Necroptosis is a caspase-independent form of PCD reliant on receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and its substrate, the pseudokinase mixed-lineage kinase domain-like protein (MLKL). As necroptosis is highly inflammatory, ReoV-induced necroptosis may contribute to the oncolytic potential of this virus, not only by promoting necrotic lysis of the infected cell, but also by inflaming the surrounding tumor microenvironment and provoking beneficial anti-tumor immune responses. In this review, we summarize our current understanding of the ReoV replication cycle, the known and potential mechanisms by which ReoV induces PCD, and discuss the consequences of non-apoptotic cell death—particularly necroptosis—to ReoV pathogenesis and oncolysis.

Tight junction proteins occludin and ZO-1 as regulators of epithelial proliferation and survival

Epithelial cells are the first line of mucosal defense. In the intestine, a single layer of epithelial cells must establish a selectively permeable barrier that supports nutrient absorption and waste secretion while preventing the leakage of potentially harmful luminal materials. Key to this is the tight junction, which seals the paracellular space and prevents unrestricted leakage. The tight junction is a protein complex established by interactions between members of the claudin, zonula occludens, and tight junction-associated MARVEL protein (TAMP) families. Claudins form the characteristic tight junction strands seen by freeze-fracture microscopy and create paracellular channels, but the functions of ZO-1 and occludin, founding members of the zonula occludens and TAMP families, respectively, are less well defined. Recent studies have revealed that these proteins have essential noncanonical (nonbarrier) functions that allow them to regulate epithelial apoptosis and proliferation, facilitate viral entry, and organize specialized epithelial structures. Surprisingly, neither is required for intestinal barrier function or overall health in the absence of exogenous stressors. Here, we provide a brief overview of ZO-1 and occludin canonical (barrier-related) functions, and a more detailed examination of their noncanonical functions.

The Murine Neuronal Receptor NgR1 Is Dispensable for Reovirus Pathogenesis

Engagement of host receptors is essential for viruses to enter target cells and initiate infection. Expression patterns of receptors in turn dictate host range, tissue tropism, and disease pathogenesis during infection. Mammalian orthoreovirus (reovirus) displays serotype-dependent patterns of tropism in the murine central nervous system (CNS) that are dictated by the viral attachment protein σ1. However, the receptor that mediates reovirus CNS tropism is unknown. Two proteinaceous receptors have been identified for reovirus, junctional adhesion molecule A (JAM-A) and Nogo-66 receptor 1 (NgR1). Engagement of JAM-A is required for reovirus hematogenous dissemination but is dispensable for neural spread and infection of the CNS. To determine whether NgR1 functions in reovirus neuropathogenesis, we compared virus replication and disease in wild-type (WT) and NgR1-/- mice. Genetic ablation of NgR1 did not alter reovirus replication in the intestine or transmission to the brain following peroral inoculation. Viral titers in neural tissues following intramuscular inoculation, which provides access to neural dissemination routes, also were comparable in WT and NgR1-/- mice, suggesting that NgR1 is dispensable for reovirus neural spread to the CNS. The absence of NgR1 also did not alter reovirus replication, neural tropism, and virulence following direct intracranial inoculation. In agreement with these findings, we found that the human but not the murine homolog of NgR1 functions as a receptor and confers efficient reovirus binding and infection of nonsusceptible cells in vitro. Thus, neither JAM-A nor NgR1 is required for reovirus CNS tropism in mice, suggesting that other unidentified receptors support this function. IMPORTANCE Viruses engage diverse molecules on host cell surfaces to navigate barriers, gain cell entry, and establish infection. Despite discovery of several reovirus receptors, host factors responsible for reovirus neurotropism are unknown. Human NgR1 functions as a reovirus receptor in vitro and is expressed in CNS neurons in a pattern overlapping reovirus tropism. We used mice lacking NgR1 to test whether NgR1 functions as a reovirus neural receptor. Following different routes of inoculation, we found that murine NgR1 is dispensable for reovirus dissemination to the CNS, tropism and replication in the brain, and resultant disease. Concordantly, expression of human but not murine NgR1 confers reovirus binding and infection of nonsusceptible cells in vitro. These results highlight species-specific use of alternate receptors by reovirus. A detailed understanding of species- and tissue-specific factors that dictate viral tropism will inform development of antiviral interventions and targeted gene delivery and therapeutic viral vectors.

Circulative Transmission of Cileviruses in Brevipalpus Mites May Involve the Paracellular Movement of Virions

Plant viruses transmitted by mites of the genus Brevipalpus are members of the genera Cilevirus, family Kitaviridae, or Dichorhavirus, family Rhabdoviridae. They produce non-systemic infections that typically display necrotic and/or chlorotic lesions around the inoculation loci. The cilevirus citrus leprosis virus C (CiLV-C) causes citrus leprosis, rated as one of the most destructive diseases affecting this crop in the Americas. CiLV-C is vectored in a persistent manner by the flat mite Brevipalpus yothersi. Upon the ingestion of viral particles with the content of the infected plant cell, virions must pass through the midgut epithelium and the anterior podocephalic gland of the mites. Following the duct from this gland, virions reach the salivary canal before their inoculation into a new plant cell through the stylet canal. It is still unclear whether CiLV-C multiplies in mite cells and what mechanisms contribute to its movement through mite tissues. In this study, based on direct observation of histological sections from viruliferous mites using the transmission electron microscope, we posit the hypothesis of the paracellular movement of CiLV-C in mites which may involve the manipulation of septate junctions. We detail the presence of viral particles aligned in the intercellular spaces between cells and the gastrovascular system of Brevipalpus mites. Accordingly, we propose putative genes that could control either active or passive paracellular circulation of viral particles inside the mites.

Lentivirus-mediated subcutaneous JAM-A modification promotes skin wound healing in a mouse model by strengthening the secretory function and proliferation of fibroblasts

A better understanding of the molecular regulation of wound healing may provide novel therapeutic targets. A previous study revealed that junctional adhesion molecule A (JAM-A)-modified mesenchymal stem cells promoted wound healing. However, whether direct JAM-A modification in the skin wound edge area accelerates the wound repair process is not clear. We determined whether JAM-A modification at the skin wound edge accelerated the wound healing process. We established JAM-A modification mouse wound models and mouse primary fibroblast cell models. Wound pictures were taken to compare the wound size. H&E staining was performed to monitor the morphology of the wound and quality of the newborn skin. CCK-8 assays and immunofluorescence (IF) for Ki67 were used to measure the cell proliferation of mouse primary fibroblasts. Quantitative real-time PCR, immunohistochemistry, IF, and Western blot analysis were used to detect bFGF and EGF expression in vivo and in vitro. The JAM-A-overexpressing group exhibited a smaller residual wound size than the control group at Day 7. Thicker epidermal layers and more hair follicle-like structures were found in the JAM-A-overexpressing group at Day 21. Cell proliferation capacity was higher in JAM-A-modified mouse fibroblasts. Elevated levels of bFGF and EGF were found in the JAM-A-modified group in vivo and in vitro. JAM-A modification significantly promoted fibroblast proliferation and wound healing. Increased levels of bFGF and EGF growth factors may be part of the mechanism.

Expression and localization of tight junction-related proteins in adult rat pituitary stem/progenitor cell niches

Pituitary endocrine cells are supplied by Sox2-expressing stem/progenitor cells in the anterior lobe of the adult pituitary gland. These SOX2-positive cells are maintained in two types of microenvironments (niches): the marginal cell layer (MCL)-niche and the parenchymal-niche. Recently, we isolated dense SOX2-positive cell clusters from the parenchymal-niche by taking advantage of their resistance to protease treatment as parenchymal stem/progenitor cell (PS)-clusters. In the present study, by analyzing these isolated PS-clusters, we attempted to identify novel structural characteristics of pituitary stem/progenitor cell niches. Quantitative real-time PCR showed that tight junction-related genes were distinctly expressed in the isolated PS-clusters. Immunocytostaining showed that the tight junction molecules, ZO-1 and occludin, were localized in the apical membrane facing the pseudo-follicle-like structure of the isolated PS-clusters regardless of the expression of S100β, which distinguishes the sub-population of SOX2-positive cells. Furthermore, immunohistochemistry of the pituitary glands of adult rats clearly demonstrated that ZO-1 and occludin were densely present in the parenchymal-niche encircling the pseudo-follicle, while they were observed in the apical membrane in the MCL-niche facing the residual lumen. Collectively, these tight junction-related proteins might be involved in the architecture and maintenance of the plasticity of pituitary stem/progenitor cell niches.

ACE2 and COVID-19 Susceptibility and Severity

Sick, male, and older populations are more vulnerable to COVID-19. However, it remains unclear whether a common mechanism exists across different demographic characteristics. SARS-CoV-2 infection is initiated by the specific binding of the viral spike protein to angiotensin-converting enzyme 2 (ACE2). This study analyzed the demographics of pulmonary ACE2 expression, Mendelian randomization (MR) of ACE2 and COVID-19, and comparative tropism of SARS-CoV-2. The key features of SARS-CoV-2 tropism, including pulmonary ACE2 expression and ACE2-expressing cell types, showed distinct subphenotypes associated with the demographics of vulnerable COVID-19 populations, suggesting a hypothesis centered on “ACE2” to explain their interplay. Next, by integrating multiple COVID-19 cohorts of genome-wide association studies (GWASs) and cis-expression quantitative trait loci (cis-eQTLs) of ACE2, MR analysis demonstrated that ACE2 played a causal role in COVID-19 susceptibility and severity, suggesting ACE2 as a promising target for early COVID-19 treatment. Next, by analyzing the expression of host cell receptors using single-cell RNA sequencing (scRNA-seq) data of human lung tissues, comparative tropism analysis showed that SARS-CoV-2 and other respiratory viruses, but not non-respiratory viruses, had remarkably overlapping and enriched cellular tropism in alveolar type 2 (AT2) cells. This finding indicates the possibility of coinfection with SARS-CoV-2 and other respiratory viruses, perhaps implying sociovirology at the cellular level. Moreover, the binding of viral entry proteins to the compatible host cell receptors is under strong natural selection pressure. Therefore, comparative tropism might reveal the footprint of natural selection that shapes the virus population, which provides a novel perspective for understanding zoonotic spillover events.

A CRISPR-Cas9 screen reveals a role for WD repeat-containing protein 81 (WDR81) in the entry of late penetrating viruses

Successful initiation of infection by many different viruses requires their uptake into the endosomal compartment. While some viruses exit this compartment early, others must reach the degradative, acidic environment of the late endosome. Mammalian orthoreovirus (reovirus) is one such late penetrating virus. To identify host factors that are important for reovirus infection, we performed a CRISPR-Cas9 knockout (KO) screen that targets over 20,000 genes in fibroblasts derived from the embryos of C57/BL6 mice. We identified seven genes (WDR81, WDR91, RAB7, CCZ1, CTSL, GNPTAB, and SLC35A1) that were required for the induction of cell death by reovirus. Notably, CRISPR-mediated KO of WD repeat-containing protein 81 (WDR81) rendered cells resistant to reovirus infection. Susceptibility to reovirus infection was restored by complementing KO cells with human WDR81. Although the absence of WDR81 did not affect viral attachment efficiency or uptake into the endosomal compartments for initial disassembly, it reduced viral gene expression and diminished infectious virus production. Consistent with the role of WDR81 in impacting the maturation of endosomes, WDR81-deficiency led to the accumulation of reovirus particles in dead-end compartments. Though WDR81 was dispensable for infection by VSV (vesicular stomatitis virus), which exits the endosomal system at an early stage, it was required for VSV-EBO GP (VSV that expresses the Ebolavirus glycoprotein), which must reach the late endosome to initiate infection. These results reveal a previously unappreciated role for WDR81 in promoting the replication of viruses that transit through late endosomes.

Viruses are obligate intracellular parasites that require the contributions of numerous host factors to complete the viral life cycle. Thus, the host-pathogen interaction can regulate cell death signaling and virus entry, replication, assembly, and egress. Functional genetic screens are useful tools to identify host factors that are important for establishing infection. Such information can also be used to understand cell biology. Notably, genome-scale CRISPR-Cas9 knockout screens are robust due to their specificity and the loss of host gene expression. Mammalian orthoreovirus (reovirus) is a tractable model system to investigate the pathogenesis of neurotropic and cardiotropic viruses. Using a CRISPR-Cas9 screen, we identified WD repeat-containing protein 81 (WDR81) as a host factor required for efficient reovirus infection of murine cells. Ablation of WDR81 blocked a late step in the viral entry pathway. Further, our work indicates that WDR81 is required for the entry of vesicular stomatitis virus that expresses the Ebolavirus glycoprotein.

Gastrointestinal cancer-associated fibroblasts expressing Junctional Adhesion Molecule-A are amenable to infection by oncolytic reovirus

Gastrointestinal (GI) cancers are characterized by extensive tumor stroma that both promotes tumor progression and acts as a physical barrier for adjacent tumor cells, limiting the effect of current treatment modalities. Oncolytic virotherapy is currently investigated in clinical trials as a novel therapeutic agent for different malignancies of the GI tract, but it is largely unknown whether these viruses can also target the tumor stroma. Here, we investigated the tropism of two commonly studied OVs, adenovirus and reovirus, towards primary GI fibroblasts from human oesophageal, gastric, duodenal and pancreatic carcinomas (N = 36). GI fibroblasts were susceptible to type 3 Dearing (T3D) strain R124 and bioselected mutant reovirus (jin-3) infection but not oncolytic adenovirus (Ad5-Δ24). Efficient infection and apoptosis of human and mouse GI cancer-derived fibroblasts by these reoviruses was partially dependent on the expression of the reovirus entry receptor, Junctional Adhesion Molecule-A (JAM-A). Moreover, human GI cancer organoid-fibroblast co-cultures showed higher overall infectivity when containing JAM-A expressing fibroblasts as compared to JAM-A negative fibroblasts, indicating a potential role of JAM-A expressing fibroblasts for viral dissemination. We further show that JAM-A is not only necessary for efficient reovirus infection of fibroblasts but also partially mediates reovirus-induced apoptosis, dependent on signaling through the C-terminal PDZ-domain of JAM-A. Altogether, our data show the presence of JAM-A expressing fibroblasts in both human and murine GI cancers that are amenable to infection and induction of apoptosis by reovirus, extending the potential anti-cancer actions of reovirus with stromal targeting.

Reovirus mutant jin-3 exhibits lytic and immune-stimulatory effects in preclinical human prostate cancer models

Treatment of castration-resistant prostate cancer remains a challenging clinical problem. Despite the promising effects of immunotherapy in other solid cancers, prostate cancer has remained largely unresponsive. Oncolytic viruses represent a promising therapeutic avenue, as oncolytic virus treatment combines tumour cell lysis with activation of the immune system and mounting of effective anti-tumour responses. Mammalian Orthoreoviruses are non-pathogenic human viruses with a preference of lytic replication in human tumour cells. In this study, we evaluated the oncolytic efficacy of the bioselected oncolytic reovirus mutant jin-3 in multiple human prostate cancer models. The jin-3 reovirus displayed efficient infection, replication, and anti-cancer responses in 2D and 3D prostate cancer models, as well as in ex vivo cultured human tumour slices. In addition, the jin-3 reovirus markedly reduced the viability and growth of human cancer cell lines and patient-derived xenografts. The infection induced the expression of mediators of immunogenic cell death, interferon-stimulated genes, and inflammatory cytokines. Taken together, our data demonstrate that the reovirus mutant jin-3 displays tumour tropism, and induces potent oncolytic and immunomodulatory responses in human prostate cancer models. Therefore, jin-3 reovirus represents an attractive candidate for further development as oncolytic agent for treatment of patients with aggressive localised or advanced prostate cancer.

Oral Administration of Bacillus subtilis Subunit Vaccine Significantly Enhances the Immune Protection of Grass Carp against GCRV-II Infection

Grass carp reovirus (GCRV) is a severe virus that causes great losses to grass carp culture every year, and GCRV-II is the current popular and fatal strain. VP56, fibrin on the outer surface of GCRV-II, mediates cell attachment. In this study, we firstly divided the VP56 gene into four fragments to screen the optimal antigen by enzyme-linked immunosorbent assay and neutralizing antibody methods. The second fragment VP56-2 demonstrates the optimal efficiency and was employed as an antigen in the following experiments. Bacillus subtilis were used as a carrier, and VP56-2 was expressed on the surface of the spores. Then, we performed the oral immunization for grass carp and the challenge with GCRV-II. The survival rate was remarkably raised, and mRNA expressions of IgM were significantly up-regulated in spleen and head kidney tissues in the B. s-CotC-VP56-2 group. Three crucial immune indexes (complement C3, lysozyme and total superoxide dismutase) in the sera were also significantly enhanced. mRNA expressions of four important genes (TNF-α, IL-1β, IFN1 and MHC-II) were significantly strengthened. Tissue lesions were obviously attenuated by histopathological slide examination in trunk kidney and spleen tissues. Tissue viral burdens were significantly reduced post-viral challenge. These results indicated that the oral recombinant B. subtilis VP56-2 subunit vaccine is effective for controlling GCRV infection and provides a feasible strategy for the control of fish virus diseases.

The Causes and Long-Term Consequences of Viral Encephalitis

Reports regarding brain inflammation, known as encephalitis, have shown an increasing frequency during the past years. Encephalitis is a relevant concern to public health due to its high morbidity and mortality. Infectious or autoimmune diseases are the most common cause of encephalitis. The clinical symptoms of this pathology can vary depending on the brain zone affected, with mild ones such as fever, headache, confusion, and stiff neck, or severe ones, such as seizures, weakness, hallucinations, and coma, among others. Encephalitis can affect individuals of all ages, but it is frequently observed in pediatric and elderly populations, and the most common causes are viral infections. Several viral agents have been described to induce encephalitis, such as arboviruses, rhabdoviruses, enteroviruses, herpesviruses, retroviruses, orthomyxoviruses, orthopneumovirus, and coronaviruses, among others. Once a neurotropic virus reaches the brain parenchyma, the resident cells such as neurons, astrocytes, and microglia, can be infected, promoting the secretion of pro-inflammatory molecules and the subsequent immune cell infiltration that leads to brain damage. After resolving the viral infection, the local immune response can remain active, contributing to long-term neuropsychiatric disorders, neurocognitive impairment, and degenerative diseases. In this article, we will discuss how viruses can reach the brain, the impact of viral encephalitis on brain function, and we will focus especially on the neurocognitive sequelae reported even after viral clearance.

Altered Glycan Expression on Breast Cancer Cells Facilitates Infection by T3 Seroptype Oncolytic Reovirus

Breast cancer is the most common cancer in women. Although current therapies have increased survival rates for some breast cancer types, other aggressive invasive breast cancers remain difficult to treat. As the onset of breast cancer is often associated with the appearance of extracellular markers, these could be used to better target therapeutic agents. Here, we demonstrated by nanobiophysical approaches that overexpression of α-sialylated glycans in breast cancer provides an opportunity to combat cancer cells with oncolytic reoviruses. Notably, a correlation between cellular glycan expression and the mechanical properties of reovirus attachment and infection is observed in a serotype-dependent manner. Furthermore, we enhance the infectivity of reoviruses in malignant cells by the coinjection of α-sialylated glycans. In conclusion, this study supports both the use of reoviruses as an oncolytic agent in nanomedicine and the role of α-sialylated glycans as adjuvants in oncolysis, offering new perspective in oncolytic cancer therapy.

Mechanisms of Cell Entry by dsRNA Viruses: Insights for Efficient Delivery of dsRNA and Tools for Improved RNAi-Based Pest Control

While RNAi is often heralded as a promising new strategy for insect pest control, a major obstacle that still remains is the efficient delivery of dsRNA molecules within the cells of the targeted insects. However, it seems overlooked that dsRNA viruses already have developed efficient strategies for transport of dsRNA molecules across tissue barriers and cellular membranes. Besides protecting their dsRNA genomes in a protective shell, dsRNA viruses also display outer capsid layers that incorporate sophisticated mechanisms to disrupt the plasma membrane layer and to translocate core particles (with linear dsRNA genome fragments) within the cytoplasm. Because of the perceived efficiency of the translocation mechanism, it is well worth analyzing in detail the molecular processes that are used to achieve this feat. In this review, the mechanism of cell entry by dsRNA viruses belonging to the Reoviridae family is discussed in detail. Because of the large amount of progress in mammalian versus insect models, the mechanism of infections of reoviruses in mammals (orthoreoviruses, rotaviruses, orbiviruses) will be treated as a point of reference against which infections of reoviruses in insects (orbiviruses in midges, plant viruses in hemipterans, insect-specific cypoviruses in lepidopterans) will be compared. The goal of this discussion is to uncover the basic principles by which dsRNA viruses cross tissue barriers and translocate their cargo to the cellular cytoplasm; such knowledge subsequently can be incorporated into the design of dsRNA virus-based viral-like particles for optimal delivery of RNAi triggers in targeted insect pests.

Prevalence of Oral Lesions in COVID-19 Egyptian Patients

OBJECTIVES

The aim of this article is to detect whether oral lesions affect the tongue mainly due to higher cells expressing angiotensin-converting enzyme 2 (ACE2) than in other oral sites in COVID-19 patients. Moreover, the etiology of oral lesions was evaluated either resulting from SARS-CoV-2 sequelae or from adverse effects of drugs used for COVID-19 treatment.

MATERIALS AND METHODS

One hundred and twenty-four patients were admitted to the study. All patients' data were obtained including age and gender, laboratory testing, drug administration, respiratory and systemic conditions, signs and symptoms, and oral manifestations.

RESULTS

Oral manifestations were seen in 112 (90.3%) of all patients. Oral ulcers represented the most prevalent lesions in the oral cavity in 104 patients (92.8%). Lip, tongue, and labial mucosa showed the most common sites for oral ulcers. Most of oral lesions were displayed in the tongue in 96 patients (85.7%). Various medications were used in the treatment of patients.

CONCLUSION

The tongue represented the most common site of oral lesions in COVID-19 patients followed by the labial mucosa. No correlation was found between the oral lesions and the drugs used for the treatment of SARS-CoV-2 infection. The systemic health and the severity of the disease were not related to the spread of the oral lesions.

Virus-associated disruption of mucosal epithelial tight junctions and its role in viral transmission and spread

Oropharyngeal, airway, intestinal, and genital mucosal epithelia are the main portals of entry for the majority of human pathogenic viruses. To initiate systemic infection, viruses must first be transmitted across the mucosal epithelium and then spread across the body. However, mucosal epithelia have well-developed tight junctions, which have a strong barrier function that plays a critical role in preventing the spread and dissemination of viral pathogens. Viruses can overcome these barriers by disrupting the tight junctions of mucosal epithelia, which facilitate paracellular viral penetration and initiate systemic disease. Disruption of tight and adherens junctions may also release the sequestered viral receptors within the junctional areas, and liberation of hidden receptors may facilitate viral infection of mucosal epithelia. This review focuses on possible molecular mechanisms of virus-associated disruption of mucosal epithelial junctions and its role in transmucosal viral transmission and spread.

Virus-associated disruption of mucosal epithelial tight junctions and its role in viral transmission and spread

Oropharyngeal, airway, intestinal, and genital mucosal epithelia are the main portals of entry for the majority of human pathogenic viruses. To initiate systemic infection, viruses must first be transmitted across the mucosal epithelium and then spread across the body. However, mucosal epithelia have well-developed tight junctions, which have a strong barrier function that plays a critical role in preventing the spread and dissemination of viral pathogens. Viruses can overcome these barriers by disrupting the tight junctions of mucosal epithelia, which facilitate paracellular viral penetration and initiate systemic disease. Disruption of tight and adherens junctions may also release the sequestered viral receptors within the junctional areas, and liberation of hidden receptors may facilitate viral infection of mucosal epithelia. This review focuses on possible molecular mechanisms of virus-associated disruption of mucosal epithelial junctions and its role in transmucosal viral transmission and spread.

MIR21-induced loss of junctional adhesion molecule A promotes activation of oncogenic pathways, progression and metastasis in colorectal cancer

Junctional adhesion molecules (JAMs) play a critical role in cell permeability, polarity and migration. JAM-A, a key protein of the JAM family, is altered in a number of conditions including cancer; however, consequences of JAM-A dysregulation on carcinogenesis appear to be tissue dependent and organ dependent with significant implications for the use of JAM-A as a biomarker or therapeutic target. Here, we test the expression and prognostic role of JAM-A downregulation in primary and metastatic colorectal cancer (CRC) (n = 947). We show that JAM-A downregulation is observed in ~60% of CRC and correlates with poor outcome in four cohorts of stages II and III CRC (n = 1098). Using JAM-A knockdown, re-expression and rescue experiments in cell line monolayers, 3D spheroids, patient-derived organoids and xenotransplants, we demonstrate that JAM-A silencing promotes proliferation and migration in 2D and 3D cell models and increases tumour volume and metastases in vivo. Using gene-expression and proteomic analyses, we show that JAM-A downregulation results in the activation of ERK, AKT and ROCK pathways and leads to decreased bone morphogenetic protein 7 expression. We identify MIR21 upregulation as the cause of JAM-A downregulation and show that JAM-A rescue mitigates the effects of MIR21 overexpression on cancer phenotype. Our results identify a novel molecular loop involving MIR21 dysregulation, JAM-A silencing and activation of multiple oncogenic pathways in promoting invasiveness and metastasis in CRC.

The F11 Receptor (F11R)/Junctional Adhesion Molecule-A (JAM-A) (F11R/JAM-A) in cancer progression

The F11 Receptor (F11R), also called Junctional Adhesion Molecule-A (JAM-A) (F11R/JAM-A), is a transmembrane glycoprotein of the immunoglobulin superfamily, which is mainly located in epithelial and endothelial cell tight junctions and also expressed on circulating platelets and leukocytes. It participates in the regulation of various biological processes, as diverse as paracellular permeability, tight junction formation and maintenance, leukocyte transendothelial migration, epithelial-to-mesenchymal transition, angiogenesis, reovirus binding, and platelet activation. Dysregulation of F11R/JAM-A may result in pathological consequences and disorders in normal cell function. A growing body of evidence points to its role in carcinogenesis and invasiveness, but its tissue-specific pro- or anti-tumorigenic role remains a debated issue. The following review focuses on the F11R/JAM-A tissue-dependent manner in tumorigenesis and metastasis and also discusses the correlation between poor patient clinical outcomes and its aberrant expression. In the future, it will be required to clarify the signaling pathways that are activated or suppressed via the F11R/JAM-A protein in various cancer types to understand its multiple roles in cancer progression and further use it as a novel direct target for cancer treatment.

Advances in viral oncolytics for treatment of multiple myeloma - a focused review

INTRODUCTION

Oncolytic viruses are genetically engineered viruses that target myeloma-affected cells by detecting specific cell surface receptors (CD46, CD138), causing cell death by activating the signaling pathway to induce apoptosis or by immune-mediated cellular destruction.

AREAS COVERED

This article summarizes oncolytic virotherapy advancements such as the therapeutic use of viruses by targeting cell surface proteins of myeloma cells as well as the carriers to deliver viruses to the target tissues safely. The major classes of viruses that have been studied for this include measles, myxoma, adenovirus, reovirus, vaccinia, vesicular-stomatitis virus, coxsackie, and others. The measles virus acts as oncolytic viral therapy by binding to the CD46 receptors on the myeloma cells to utilize its surface H protein. These H-protein and CD46 interactions lead to cellular syncytia formation resulting in cellular apoptosis. Vesicular-stomatitis virus acts by downregulation of anti-apoptotic factors (Mcl-2, BCL-2). Based upon the published literature searches till December 2020, we have summarized the data supporting the advances in viral oncolytic for the treatment of MM.

EXPERT OPINION

Oncolytic virotherapy is an experimental approach in multiple myeloma (MM); many issues need to be addressed for safe viral delivery to the target tissue.

Induction of Robust Type I Interferon Levels by Oncolytic Reovirus Requires Both Viral Replication and Interferon-α/β Receptor Signaling

Oncolytic viruses are promising agents for cancer therapy because they selectively infect and kill tumor cells, and because they trigger immune responses that can boost anticancer immunity. Key to the latter process is the production of type I interferons (IFN-Is) that can turn noninflamed "cold" tumors into "hot" ones. Besides this desired anticancer effect, IFN-Is are antiviral and successful oncolytic virotherapy thus relies on tightly controlled IFN-I levels. This requires a profound understanding of when and how tumor cells induce IFN-I in response to specific viruses. In this study, we uncovered two key factors that augment IFN-I production in transformed human myeloid cells infected with a tumor-selective reovirus. Viral replication and IFN-α/β receptor (IFNAR) signaling progressively reinforced the levels of IFN-I expressed by infected cells. Mechanistically, both augmented the activation of interferon regulatory factor 3, a key transcription factor for IFNβ expression. Our findings imply that reovirus-permissive tumor cells themselves are a major source of IFN-I expression. As tumors can perturb the IFNAR pathway for their own survival, reovirus-exposed IFNAR-unresponsive tumors may need additional therapeutic intervention to promote the secretion of sufficient IFN-I into the tumor microenvironment. Our increased understanding of the parameters that affect reovirus-induced IFN-I levels could aid in the design of tailored virus-based cancer therapies.

Effects of ozone and particulate matter on airway epithelial barrier structure and function: a review of in vitro and in vivo studies

The airway epithelium represents a crucial line of defense against the spread of inhaled pathogens. As the epithelium is the first part of the body to be exposed to the inhaled environment, it must act as both a barrier to and sentinel against any inhaled agents. Despite its vital role in limiting the spread of inhaled pathogens, the airway epithelium is also regularly exposed to air pollutants which disrupt its normal function. Here we review the current understanding of the structure and composition of the airway epithelial barrier, as well as the impact of inhaled pollutants, including the reactive gas ozone and particulate matter, on epithelial function. We discuss the current in vitro, rodent model, and human exposure findings surrounding the impact of various inhaled pollutants on epithelial barrier function, mucus production, and mucociliary clearance. Detailed information on how inhaled pollutants impact epithelial structure and function will further our understanding of the adverse health effects of air pollution exposure.

Tight junction protein claudin-2 promotes cell entry of Bombyx mori cypovirus

Claudin-2 is a major component of tight junctions (TJs), which play an important role in reovirus entry into host cells. The Bombyx mori cytoplasmic polyhedosis virus (BmCPV) relates to the cypovirus strain of the reovirus family. So far, the role of claudin-2 in the process of BmCPV infection is not known. In the present study, it was observed that increasing expression of the claudin-2 gene (CLDN2) may concomitantly elevate BmCPV infection. Contrarily, knockdown of CLDN2 expression by siRNAs can reduce BmCPV infection. Similarly, antibody-based blockage of claudin-2 could also decrease BmCPV cell entry. These results suggest that claudin-2 can promote BmCPV infection in vitro. Moreover, immunofluorescence (IF) assays showed that claudin-2 can interact with BmCPV during viral infection. Specifically, co-immunoprecipitation experiments indicated that claudin-2 binds the BmCPV VP7 (instead of VP3 proteins). The interaction between VP7 and claudin-2 was further confirmed by bimolecular fluorescence complementation (BIFC). Altogether, our results suggest that BmCPV cell entry can be promoted upon interaction of VP7 with claudin-2. These findings provide new mechanistic insights related to BmCPV infection. KEY POINTS: •Claudin-2 could promote BmCPV infection of cells. •Claudin-2 interacted with BmCPV during BmCPV infection. •Claudin-2 could interact with BmCPV VP7 protein, but not with VP3 proteins.

Targeting JAK/STAT Signaling Antagonizes Resistance to Oncolytic Reovirus Therapy Driven by Prior Infection with HTLV-1 in Models of T-Cell Lymphoma

Human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that infects at least 10 million people worldwide and is associated with the development of T-cell lymphoma (TCL). The treatment of TCL remains challenging and new treatment options are urgently needed. With the goal of developing a novel therapeutic approach for TCL, we investigated the activity of the clinical formulation of oncolytic reovirus (Reolysin, Pelareorep) in TCL models. Our studies revealed that HTLV-1-negative TCL cells were highly sensitive to Reolysin-induced cell death, but HTLV-1-positive TCL cells were resistant. Consistent with these data, reovirus displayed significant viral accumulation in HTLV-1-negative cells, but failed to efficiently replicate in HTLV-1-positive cells. Transcriptome analyses of HTLV-1-positive vs. negative cells revealed a significant increase in genes associated with retroviral infection including interleukin-13 and signal transducer and activator of transcription 5 (STAT5). To investigate the relationship between HTLV-1 status and sensitivity to Reolysin, we infected HTLV-1-negative cells with HTLV-1. The presence of HTLV-1 resulted in significantly decreased sensitivity to Reolysin. Treatment with the JAK inhibitor ruxolitinib suppressed STAT5 phosphorylation and expression of the key anti-viral response protein MX1 and enhanced the anti-TCL activity of Reolysin in both HTLV-1-positive and negative cells. Our data demonstrate that the inhibition of the JAK/STAT pathway can be used as a novel approach to antagonize the resistance of HTLV-1-positive cells to oncolytic virus therapy.

Isolation and characterization of novel reassortant mammalian orthoreovirus from pigs in the United States

Mammalian orthoreovirus (MRV) infects multiple mammalian species including humans. A United States Midwest swine farm with approximately one thousand 3-month-old pigs experienced an event, in which more than 300 pigs showed neurological signs, like "down and peddling", with approximately 40% mortality. A novel MRV was isolated from the diseased pigs. Sequence and phylogenetic analysis revealed that the isolate was a reassortant virus containing viral gene segments from three MRV serotypes that infect human, bovine and swine. The M2 and S1 segment of the isolate showed 94% and 92% nucleotide similarity to the M2 of the MRV2 D5/Jones and the S1 of the MRV1 C/bovine/Indiana/MRV00304/2014, respectively; the remaining eight segments displayed 93%-95% nucleotide similarity to those of the MRV3 FS-03/Porcine/USA/2014. Pig studies showed that both MRV-infected and native contact pigs displayed fever, diarrhoea and nasal discharge. MRV RNA was detected in different intestinal locations of both infected and contact pigs, indicating that the MRV isolate is pathogenic and transmissible in pigs. Seroconversion was also observed in experimentally infected pigs. A prevalence study on more than 180 swine serum samples collected from two states without disease revealed 40%-52% positive to MRV. All results warrant the necessity to monitor MRV epidemiology and reassortment as the MRV could be an important pathogen for the swine industry and a novel MRV might emerge to threaten animal and public health.

Resistance to histone deacetylase inhibitors confers hypersensitivity to oncolytic reovirus therapy

Despite the promising antilymphoma activity of histone deacetylase (HDAC) inhibitors as a drug class, resistance is a significant clinical issue. Elucidating the molecular mechanisms driving HDAC inhibitor resistance and/or the specific targets that are altered in drug-resistant cells may facilitate the development of strategies that overcome drug resistance and are more effective for refractory patients. We generated novel T-cell lymphoma (TCL) cell line models of acquired resistance to the HDAC inhibitor belinostat to identify potential effective therapies. Belinostat-resistant cells displayed significant cross-resistance to other HDAC inhibitors including romidepsin, panobinostat, and vorinostat. Consistent with a lack of sensitivity to HDAC inhibitors, the resistant cells failed to induce increased acetylated histones. Drug-resistant cells featured significantly decreased expression of the key antiviral mediators IRF1 and STAT1. On the basis of these findings, we investigated the efficacy of the clinical formulation of reovirus (Reolysin) in parental and drug-resistant models. Our investigation revealed that HDAC inhibitor-resistant cells displayed enhanced vulnerability to reovirus replication and cell death in both in vitro and in vivo models compared with their parental counterparts. Importantly, Reolysin also significantly increased the antilymphoma activity of belinostat in HDAC inhibitor-resistant cells. Our data demonstrate that Reolysin alone or in combination with belinostat is a novel therapeutic strategy to treat TCL patients who develop resistance to HDAC inhibitors.

The Immunomodulatory CEA Cell Adhesion Molecule 6 (CEACAM6/CD66c) Is a Protein Receptor for the Influenza a Virus

To establish a productive infection in host cells, viruses often use one or multiple host membrane glycoproteins as their receptors. For Influenza A virus (IAV) such a glycoprotein receptor has not been described, to date. Here we show that IAV is using the host membrane glycoprotein CD66c as a receptor for entry into human epithelial lung cells. Neuraminidase (NA), a viral spike protein, binds to CD66c on the cell surface during IAV entry into the host cells. Lung cells overexpressing CD66c showed an increase in virus binding and subsequent entry into the cell. Upon comparison, CD66c demonstrated higher binding capacity than other membrane glycoproteins (EGFR and DC-SIGN) reported earlier to facilitate IAV entry into host cells. siRNA mediated knockdown of CD66c from lung cells inhibited virus binding on cell surface and entry into cells. Blocking CD66c by antibody on the cell surface resulted in decreased virus entry. We found that CD66c is a specific glycoprotein receptor for influenza A virus that did not affect entry of non-IAV RNA virus (Hepatitis C virus). Finally, IAV pre-incubated with recombinant CD66c protein when administered intranasally in mice showed decreased cytopathic effects in mice lungs. This publication is the first to report CD66c (Carcinoembryonic cell adhesion molecule 6 or CEACAM6) as a glycoprotein receptor for Influenza A virus.

Isolation, Identification, and Genomic Analysis of a Novel Reovirus from Healthy Grass Carp and Its Dynamic Proliferation In Vitro and In Vivo

A new grass carp reovirus (GCRV), healthy grass carp reovirus (HGCRV), was isolated from grass carp in 2019. Its complete genome sequence was determined and contained 11 dsRNAs with a total size of 23,688 bp and 57.2 mol% G+C content, encoding 12 proteins. All segments had conserved 5' and 3' termini. Sequence comparisons showed that HGCRV was closely related to GCRV-873 (GCRV-I; 69.57-96.71% protein sequence identity) but shared only 22.65-45.85% and 23.37-43.39% identities with GCRV-HZ08 and Hubei grass carp disease reovirus (HGDRV), respectively. RNA-dependent RNA-polymerase (RdRp) protein-based phylogenetic analysis showed that HGCRV clustered with Aquareovirus-C (AqRV-C) prior to joining a branch common with other aquareoviruses. Further analysis using VP6 amino acid sequences from Chinese GCRV strains showed that HGCRV was in the same evolutionary cluster as GCRV-I. Thus, HGCRV could be a new GCRV isolate of GCRV-I but is distantly related to other known GCRVs. Grass carp infected with HGCRV did not exhibit signs of hemorrhage. Interestingly, the isolate induced a typical cytopathic effect in fish cell lines, such as infected cell shrank, apoptosis, and plague-like syncytia. Further analysis showed that HGCRV could proliferate in grass carp liver (L28824), gibel carp brain (GiCB), and other fish cell lines, reaching a titer of up to 7.5 × 10⁴ copies/μL.