Bifidobacterium longum and Chlorella sorokiniana Combination Modulates IFN-γ, IL-10, and SOCS3 in Rotavirus-Infected Cells

Rotavirus is the main cause of acute diarrhea in children up to five years of age. In this regard, probiotics are commonly used to treat or prevent gastroenteritis including viral infections. The anti-rotavirus effect of Bifidobacterium longum and Chlorella sorokiniana, by reducing viral infectivity and improving IFN-type I response, has been previously reported. The present study aimed to study the effect of B. longum and/or C. sorokiniana on modulating the antiviral cellular immune response mediated by IFN-γ, IL-10, SOCS3, STAT1, and STAT2 genes in rotavirus-infected cells. To determine the mRNA relative expression of these genes, HT-29 cells were treated with B. longum and C. sorokiniana alone or in combination, followed by rotavirus infection. In addition, infected cells were treated with B. longum and/or C. sorokiniana. Cellular RNA was purified, used for cDNA synthesis, and amplified by qPCR. Our results demonstrated that the combination of B. longum and C. sorokiniana stimulates the antiviral cellular immune response by upregulating IFN-γ and may block pro-inflammatory cytokines by upregulating IL-10 and SOCS3. The results of our study indicated that B. longum, C. sorokiniana, or their combination improve antiviral cellular immune response and might modulate pro-inflammatory responses.

Candida albicans-enteric viral interactions-The prostaglandin E2 connection and host immune responses

The human microbiome comprises trillions of microorganisms residing within different mucosal cavities and across the body surface. The gut microbiota modulates host susceptibility to viral infections in several ways, and microbial interkingdom interactions increase viral infectivity within the gut. Candida albicans, a frequently encountered fungal species in the gut, produces highly structured biofilms and eicosanoids such as prostaglandin E₂ (PGE₂), which aid in viral protection and replication. These biofilms encompass viruses and provide a shield from antiviral drugs or the immune system. PGE₂ is a key modulator of active inflammation with the potential to regulate interferon signaling upon microbial invasion or viral infections. In this review, we raise the perspective of gut interkingdom interactions involving C. albicans and enteric viruses, with a special focus on biofilms, PGE₂, and viral replication. Ultimately, we discuss the possible implications of C. albicans-enteric virus associations on host immune responses, particularly the interferon signaling pathway.

Suppression of classical nuclear import pathway by importazole and ivermectin inhibits rotavirus replication

BACKGROUND

Rotavirus is the foremost cause of acute gastroenteritis among infants in resource-poor countries, causing severe morbidity and mortality. The currently available rotavirus vaccines are effective in reducing severity of the disease but not the infection rates, thus antivirals as an adjunct therapy are needed to reduce the morbidity in children. Viruses rely on host cellular machinery for nearly every step of the replication cycle. Therefore, targeting host factors that are indispensable for virus replication could be a promising strategy.

OBJECTIVES

To assess the therapeutic potential of ivermectin and importazole against rotaviruses.

METHODS

Antirotaviral activity of importazole and ivermectin was measured against various rotavirus strains (RV-SA11, RV-Wa, RV-A5-13, RV-EW) in vitro and in vivo by quantifying viral protein expression by western blot, analysing viroplasm formation by confocal microscopy, and measuring virus yield by plaque assay.

RESULTS

Importin-β1 and Ran were found to be induced during rotavirus infection. Knocking down importin-β1 severely impaired rotavirus replication, suggesting a critical role for importin-β1 in the rotavirus life cycle. In vitro studies revealed that treatment of ivermectin and importazole resulted in reduced synthesis of viral proteins, diminished production of infectious virus particles, and decrease in viroplasm-positive cells. Mechanistic study proved that both drugs perform antirotavirus activity by inhibiting the function of importin-β1. In vivo investigations in mice also confirmed the antirotavirus potential of importazole and ivermectin at non-toxic doses. Treatments of rotavirus-infected mice with either drug resulted in diminished shedding of viral particles in the stool sample, reduced expression of viral protein in the small intestine and restoration of damaged intestinal villi comapared to untreated infected mice.

CONCLUSIONS

The study highlights the potential of importazole and ivermectin as antirotavirus therapeutics.

Re-Examining Rotavirus Innate Immune Evasion: Potential Applications of the Reverse Genetics System

Rotaviruses represent one of the most successful pathogens in the world, with high infectivity and efficient transmission between the young of many animal species, including humans. To overcome host defenses, rotaviruses have evolved a plethora of strategies to effectively evade the innate immune response, establish initial infection in the small intestine, produce progeny, and shed into the environment. Previously, studying the roles and relative contributions of specific rotaviral factors in innate immune evasion had been challenging without a plasmid-only reverse genetics system. Although still in its infancy, current reverse genetics technology will help address important research questions regarding rotavirus innate immune evasion, host range restriction, and viral pathogenesis. In this review, we summarize the current knowledge about the antiviral host innate immune defense mechanisms, countermeasures of rotavirus-encoded factors, and strategies to better understand these interactions using the rotavirus reverse genetics system.

Rotavirus NSP1 Contributes to Intestinal Viral Replication, Pathogenesis, and Transmission

Rotavirus (RV)-encoded nonstructural protein 1 (NSP1), the product of gene segment 5, effectively antagonizes host interferon (IFN) signaling via multiple mechanisms. Recent studies with the newly established RV reverse genetics system indicate that NSP1 is not essential for the replication of the simian RV SA11 strain in cell culture. However, the role of NSP1 in RV infection in vivo remains poorly characterized due to the limited replication of heterologous simian RVs in the suckling mouse model. Here, we used an optimized reverse genetics system and successfully recovered recombinant murine RVs with or without NSP1 expression. While the NSP1-null virus replicated comparably with the parental murine RV in IFN-deficient and IFN-competent cell lines in vitro, it was highly attenuated in 5-day-old wild-type suckling pups in both the 129sv and C57BL/6 backgrounds. In the absence of NSP1 expression, murine RV had significantly reduced replication in the ileum, systemic spread to mesenteric lymph nodes, fecal shedding, diarrhea occurrence, and transmission to uninoculated littermates. The defective replication of the NSP1-null RV in small intestinal tissues occurred as early as 1 day postinfection. Of interest, the replication and pathogenesis defects of NSP1-null RV were only minimally rescued in Stat1 knockout pups, suggesting that NSP1 facilitates RV replication in an IFN-independent manner. Our findings highlight a pivotal function of NSP1 during homologous RV infections in vivo and identify NSP1 as an ideal viral protein for targeted attenuation for future vaccine development.

Rotavirus research: 2014-2020

Rotaviruses are major causes of acute gastroenteritis in infants and young children worldwide and also cause disease in the young of many other mammalian and of avian species. During the recent 5-6 years rotavirus research has benefitted in a major way from the establishment of plasmid only-based reverse genetics systems, the creation of human and other mammalian intestinal enteroids, and from the wide application of structural biology (cryo-electron microscopy, cryo-EM tomography) and complementary biophysical approaches. All of these have permitted to gain new insights into structure-function relationships of rotaviruses and their interactions with the host. This review follows different stages of the viral replication cycle and summarizes highlights of structure-function studies of rotavirus-encoded proteins (both structural and non-structural), molecular mechanisms of viral replication including involvement of cellular proteins and lipids, the spectrum of viral genomic and antigenic diversity, progress in understanding of innate and acquired immune responses, and further developments of prevention of rotavirus-associated disease.

African horse sickness virus NS4 protein is an important virulence factor and interferes with JAK-STAT signaling during viral infection

African horse sickness virus (AHSV) non-structural protein NS4 is a nucleocytoplasmic protein that is expressed in the heart, lung, and spleen of infected horses, binds dsDNA, and colocalizes with promyelocytic leukemia nuclear bodies (PML-NBs). The aim of this study was to investigate the role of AHSV NS4 in viral replication, virulence and the host immune response. Using a reverse genetics-derived virulent strain of AHSV-5 and NS4 deletion mutants, we showed that knockdown of NS4 expression has no impact in cell culture, but results in virus attenuation in infected horses. RNA sequencing (RNA-seq) was used to investigate the transcriptional response in these horses, to see how the lack of NS4 mediates the transition of the virus from virulent to attenuated. The presence of NS4 was shown to result in a 24 hour (h) delay in the transcriptional activation of several immune system processes compared to when the protein was absent. Included in these processes were the RIG-I-like, Toll-like receptor, and JAK-STAT signaling pathways, which are key pathways involved in innate immunity and the antiviral response. Thus, it was shown that AHSV NS4 suppresses the host innate immune transcriptional response in the early stages of the infection cycle. We investigated whether AHSV NS4 affects the innate immune response by impacting the JAK-STAT signaling pathway specifically. Using confocal laser scanning microscopy (CLSM) we showed that AHSV NS4 disrupts JAK-STAT signaling by interfering with the phosphorylation and/or translocation of STAT1 and pSTAT1 into the nucleus. Overall, these results showed that AHSV NS4 is a key virulence factor in horses and allows AHSV to overcome host antiviral responses in order to promote viral replication and spread.

Rotavirus NSP1 Inhibits Type I and Type III Interferon Induction

Type I interferons (IFNs) are produced by most cells in response to virus infection and stimulate a program of anti-viral gene expression in neighboring cells to suppress virus replication. Type III IFNs have similar properties, however their effects are limited to epithelial cells at mucosal surfaces due to restricted expression of the type III IFN receptor. Rotavirus (RV) replicates in intestinal epithelial cells that respond predominantly to type III IFNs, and it has been shown that type III rather than type I IFNs are important for controlling RV infections in vivo. The RV NSP1 protein antagonizes the host type I IFN response by targeting IRF-3, IRF-5, IRF-7, or β-TrCP for proteasome-mediated degradation in a strain-specific manner. Here we provide the first demonstration that NSP1 proteins from several human and animal RV strains antagonize type III as well as type I IFN induction. We also show that NSP1 is a potent inhibitor of IRF-1, a previously undescribed property of NSP1 which is conserved among human and animal RVs. Interestingly, all NSP1 proteins were substantially more effective inhibitors of IRF-1 than either IRF-3 or IRF-7 which has significance for evasion of basal anti-viral immunity and type III IFN induction in the intestinal epithelium.

Serial Passaging of the Human Rotavirus CDC-9 Strain in Cell Culture Leads to Attenuation: Characterization from In Vitro and In Vivo Studies

Live oral rotavirus vaccines have been developed by serial passaging in cell culture and found to be safe in infants. However, mechanisms for the adaptation and attenuation of rotavirus vaccines are not fully understood. We prepared a human rotavirus vaccine strain, CDC-9 (G1P[8]), which when grown in MA104 cells to passage 11 or 12 (P11/P12) had no nucleotide or amino acid sequence changes from the original virus in stool. Upon adaptation and passages in Vero cells, the strain underwent five amino acid changes at P28 and one additional change at P44/P45 in the VP4 gene. We performed virologic, immunological, and pathogenic characterization of wild-type CDC-9 virus at P11/P12 and its two mutants at P28 or P44/P45 using in vitro and in vivo model systems. We found that mutants CDC-9 P28 and P44 induced upregulated expression of immunomodulatory cytokines. On the other hand, the two mutant viruses induced lower STAT1 phosphorylation and grew to 2-log-higher titers than wild-type virus in human Caco-2 cells and simian Vero cells. In neonatal rats, CDC-9 P45 showed reduced rotavirus shedding in fecal specimens and did not induce diarrhea compared to wild-type virus and modulated cytokine responses comparably to Rotarix infection. These findings indicate that mutant CDC-9 is attenuated and safe. Our study is the first to provide insight into the possible mechanisms of human rotavirus adaptation and attenuation and supports ongoing efforts to develop CDC-9 as a new generation of rotavirus vaccine for live oral or parenteral administration.IMPORTANCE Mechanisms for in vitro adaptation and in vivo attenuation of human rotavirus vaccines are not known. The present study is the first to comprehensively compare the in vitro growth characteristics, virulence, and host response of a wild-type and an attenuated human rotavirus strain, CDC-9, in Caco-2 cells and neonatal rats. Our study identifies critical sequence changes in the genome that render human rotavirus adapted to growth to high levels in Vero cells and attenuated and safe in neonatal rats; thus, the study supports clinical development of CDC-9 for oral or parenteral vaccination in children.

The Role of Innate Immunity in Regulating Rotavirus Replication, Pathogenesis, and Host Range Restriction and the Implications for Live Rotaviral Vaccine Development

Rotaviruses (RVs) are important causative agents of viral gastroenteritis in the young of most mammalian species studied, including humans, in which they are the most important cause of severe gastroenteritis worldwide despite the availability of several safe and effective vaccines. Replication of RVs is restricted in a host species-specific manner, and this barrier is determined predominantly by the host interferon (IFN) signaling and the ability of different RV strains to successfully negate IFN activation and amplification pathways. In addition, viral attachment to the target intestinal epithelial cells also regulates host range restriction. Several studies have focused on the role of the innate immune response in regulating RV replication and pathogenesis. The knowledge accrued from these efforts is likely to result in rational attenuation of RV vaccines to closely match circulating (and host species-matched) virus strains. In this chapter, we review prevalent models of RV interactions with innate immune factors, viral strategies employed to regulate their function, and the implications of these findings for improved RV vaccine development.

Respiratory Syncytial Virus Nonstructural Protein 1 Blocks Glucocorticoid Receptor Nuclear Translocation by Targeting IPO13 and May Account for Glucocorticoid Insensitivity

Despite their powerful antiinflammatory effect, glucocorticoids have shown no significant clinical benefit in respiratory syncytial virus (RSV)-induced bronchiolitis, the reason for which remains unclear. Upon glucocorticoid binding, the cytoplasmic glucocorticoid receptor (GR) translocates to the nucleus with the help of importin 13 (IPO13). Here, we report that RSV infection reduced GR nuclear translocation in nasopharyngeal aspirates from RSV-infected infants, lungs of infected mice, and A549 cells, which coincided with decreased IPO13 expression. This led to repression of GR-induced antiinflammatory genes, such that dexamethasone failed to suppress airway inflammation and airway hyperresponsiveness in the infected mice. The anti-GR effect of RSV was mediated by viral nonstructural protein 1 , which likely functioned by competing with IPO13 for GR binding. Our findings provide a mechanism for the ineffectiveness of glucocorticoids in RSV-related disease and highlight the potential to target the IPO13-GR axis as a treatment for multiple glucocorticoid-related diseases.

Rotavirus infection beyond the gut

The landscape of rotavirus (RV) infection has changed substantially in recent years. Autoimmune triggering has been added to clinical spectrum of this pathology, which is now known to be much broader than diarrhea. The impact of RV vaccines in these other conditions is becoming a growing field of research. The importance of host genetic background in RV susceptibility has been revealed, therefore increasing our understanding of vaccine effectiveness and giving some clues about the limited efficacy of RV vaccines in low-income settings. Also, interaction of RV with intestinal microbiota seems to play a key role in the process of infection vaccine effect. This article reviews current findings on the extraintestinal impact of RV infection and their widening clinical picture, and the recently described mechanisms of host susceptibility to infection and vaccine effectiveness. RV infection is a systemic disease with clinical and pathophysiological implications beyond the gut. We propose an “iceberg” model for this pathology with almost hidden clinical implications away from the gastrointestinal tract and eventually triggering the development of autoimmune diseases. Impact of current vaccines is being influenced by host genetics and gut microbiota interactions and these factors must be taken into account in the development of public health programs.

Cytoplasmic Relocalization and Colocalization with Viroplasms of Host Cell Proteins, and Their Role in Rotavirus Infection

Rotavirus replicates in the cytoplasm of infected cells in unique virus-induced cytoplasmic inclusion bodies called viroplasms (VMs), which are nucleated by two essential viral nonstructural proteins, NSP2 and NSP5. However, the precise composition of the VM, the intracellular localization of host proteins during virus infection, and their association with VMs or role in rotavirus growth remained largely unexplored. Mass spectrometry analyses revealed the presence of several host heterogeneous nuclear ribonucleoproteins (hnRNPs), AU-rich element-binding proteins (ARE-BPs), and cytoplasmic proteins from uninfected MA104 cell extracts in the pulldown (PD) complexes of the purified viroplasmic proteins NSP2 and NSP5. Immunoblot analyses of PD complexes from RNase-treated and untreated cell extracts, analyses of coimmunoprecipitation complexes using RNase-treated infected cell lysates, and direct binding assays using purified recombinant proteins further demonstrated that the interactions of the majority of the hnRNPs and ARE-BPs with viroplasmic proteins are RNA independent. Time course immunoblot analysis of the nuclear and cytoplasmic fractions from rotavirus-infected and mock-infected cells and immunofluorescence confocal microscopy analyses of virus-infected cells revealed a surprising sequestration of the majority of the relocalized host proteins in viroplasms. Analyses of ectopic overexpression and small interfering RNA (siRNA)-mediated downregulation of expression revealed that host proteins either promote or inhibit viral protein expression and progeny virus production in virus-infected cells. This study demonstrates that rotavirus induces the cytoplasmic relocalization and sequestration of a large number of nuclear and cytoplasmic proteins in viroplasms, subverting essential cellular processes in both compartments to promote rapid virus growth, and reveals that the composition of rotavirus viroplasms is much more complex than is currently understood.IMPORTANCE Rotavirus replicates exclusively in the cytoplasm. Knowledge on the relocalization of nuclear proteins to the cytoplasm or the role(s) of host proteins in rotavirus infection is very limited. In this study, it is demonstrated that rotavirus infection induces the cytoplasmic relocalization of a large number of nuclear RNA-binding proteins (hnRNPs and AU-rich element-binding proteins). Except for a few, most nuclear hnRNPs and ARE-BPs, nuclear transport proteins, and some cytoplasmic proteins directly interact with the viroplasmic proteins NSP2 and NSP5 in an RNA-independent manner and become sequestered in the viroplasms of infected cells. The host proteins differentially affected viral gene expression and virus growth. This study demonstrates that rotavirus induces the relocalization and sequestration of a large number of host proteins in viroplasms, affecting host processes in both compartments and generating conditions conducive for virus growth in the cytoplasm of infected cells.

Distinct Effects of Type I and III Interferons on Enteric Viruses

Interferons (IFNs) are key host cytokines in the innate immune response to viral infection, and recent work has identified unique roles for IFN subtypes in regulating different aspects of infection. Currently emerging is a common theme that type III IFNs are critical in localized control of infection at mucosal barrier sites, while type I IFNs are important for broad systemic control of infections. The intestine is a particular site of interest for exploring these effects, as in addition to being the port of entry for a multitude of pathogens, it is a complex tissue with a variety of cell types as well as the presence of the intestinal microbiota. Here we focus on the roles of type I and III IFNs in control of enteric viruses, discussing what is known about signaling downstream from these cytokines, including induction of specific IFN-stimulated genes. We review viral strategies to evade IFN responses, effects of IFNs on the intestine, interactions between IFNs and the microbiota, and briefly discuss the role of IFNs in controlling viral infections at other barrier sites. Enhanced understanding of the coordinate roles of IFNs in control of viral infections may facilitate development of antiviral therapeutic strategies; here we highlight potential avenues for future exploration.

MHC class I expression in intestinal cells is reduced by rotavirus infection and increased in bystander cells lacking rotavirus antigen

Detection of viral infection by host cells leads to secretion of type I interferon, which induces antiviral gene expression. The class I major histocompatibility complex (MHCI) is required for viral antigen presentation and subsequent infected cell killing by cytotoxic T lymphocytes. STAT1 activation by interferon can induce NLRC5 expression, promoting MHCI expression. Rotavirus, an important pathogen, blocks interferon signalling through inhibition of STAT1 nuclear translocation. We assessed MHCI expression in HT-29 intestinal epithelial cells following rotavirus infection. MHCI levels were upregulated in a partially type I interferon-dependent manner in bystander cells lacking rotavirus antigen, but not in infected cells. MHCI and NLRC5 mRNA expression also was elevated in bystander, but not infected, cells, suggesting a transcriptional block in infected cells. STAT1 was activated in bystander and infected cells, but showed nuclear localisation in bystander cells only. Overall, the lack of MHCI upregulation in rotavirus-infected cells may be at least partially due to rotavirus blockade of interferon-induced STAT1 nuclear translocation. The reduced MHCI protein levels in infected cells support the existence of an additional, non-transcriptional mechanism that reduces MHCI expression. It is possible that rotavirus also may suppress MHCI expression in vivo, which might limit T cell-mediated killing of rotavirus-infected enterocytes.

Rotavirus Degrades Multiple Interferon (IFN) Type Receptors To Inhibit IFN Signaling and Protects against Mortality from Endotoxin in Suckling Mice

STAT1 phosphorylation in response to exogenous interferon (IFN) administration can be inhibited by rotaviral replication both in vitro and in vivo In addition many rotavirus strains are resistant to the actions of different IFN types. The regulation by rotaviruses (RVs) of antiviral pathways mediated by multiple IFN types is not well understood. In this study, we find that during infection in vitro and in vivo, RVs significantly deplete IFN type I, II, and III receptors (IFNRs). Regulation of IFNRs occurred exclusively within RV-infected cells and could be abrogated by inhibiting the lysosomal-endosomal degradation pathway. In vitro, IFNR degradation was conserved across multiple RV strains that differ in their modes of regulating IFN induction. In suckling mice, exogenously administered type I, II, or III IFN induced phosphorylation of STAT1-Y701 within intestinal epithelial cells (IECs) of suckling mice. Murine EW strain RV infection transiently activated intestinal STAT1 at 1 day postinfection (dpi) but not subsequently at 2 to 3 dpi. In response to injection of purified IFN-α/β or -λ, IECs in EW-infected mice exhibited impaired STAT1-Y701 phosphorylation, correlating with depletion of different intestinal IFNRs and impaired IFN-mediated transcription. The ability of EW murine RV to inhibit multiple IFN types led us to test protection of suckling mice from endotoxin-mediated shock, an outcome that is dependent on the host IFN response. Compared to mortality in controls, mice infected with EW murine RV were substantially protected against mortality following parenteral endotoxin administration. These studies identify a novel mechanism of IFN subversion by RV and reveal an unexpected protective effect of RV infection on endotoxin-mediated shock in suckling mice.IMPORTANCE Antiviral functions of types I, II, and III IFNs are mediated by receptor-dependent activation of STAT1. Here, we find that RV degrades the types I, II, and III IFN receptors (IFNRs) in vitro In a suckling mouse model, RV effectively blocked STAT1 activation and transcription following injection of different purified IFNs. This correlated with significantly decreased protein expression of intestinal types I and II IFNRs. Recent studies demonstrate that in mice lipopolysaccharide (LPS)-induced lethality is prevented by genetic ablation of IFN signaling genes such as IFNAR1 and STAT1. When suckling mice were infected with RV, they were substantially protected from lethal exposure to endotoxin. These findings provide novel insights into the mechanisms underlying rotavirus regulation of different interferons and are likely to stimulate new research into both rotavirus pathogenesis and endotoxemia.

Rotavirus infection

Rotavirus infections are a leading cause of severe, dehydrating gastroenteritis in children <5 years of age. Despite the global introduction of vaccinations for rotavirus over a decade ago, rotavirus infections still result in >200,000 deaths annually, mostly in low-income countries. Rotavirus primarily infects enterocytes and induces diarrhoea through the destruction of absorptive enterocytes (leading to malabsorption), intestinal secretion stimulated by rotavirus non-structural protein 4 and activation of the enteric nervous system. In addition, rotavirus infections can lead to antigenaemia (which is associated with more severe manifestations of acute gastroenteritis) and viraemia, and rotavirus can replicate in systemic sites, although this is limited. Reinfections with rotavirus are common throughout life, although the disease severity is reduced with repeat infections. The immune correlates of protection against rotavirus reinfection and recovery from infection are poorly understood, although rotavirus-specific immunoglobulin A has a role in both aspects. The management of rotavirus infection focuses on the prevention and treatment of dehydration, although the use of antiviral and anti-emetic drugs can be indicated in some cases.

Cytokine Regulation of Metastasis and Tumorigenicity

The human body combats infection and promotes wound healing through the remarkable process of inflammation. Inflammation is characterized by the recruitment of stromal cell activity including recruitment of immune cells and induction of angiogenesis. These cellular processes are regulated by a class of soluble molecules called cytokines. Based on function, cell target, and structure, cytokines are subdivided into several classes including: interleukins, chemokines, and lymphokines. While cytokines regulate normal physiological processes, chronic deregulation of cytokine expression and activity contributes to cancer in many ways. Gene polymorphisms of all types of cytokines are associated with risk of disease development. Deregulation RNA and protein expression of interleukins, chemokines, and lymphokines have been detected in many solid tumors and hematopoetic malignancies, correlating with poor patient prognosis. The current body of literature suggests that in some tumor types, interleukins and chemokines work against the human body by signaling to cancer cells and remodeling the local microenvironment to support the growth, survival, and invasion of primary tumors and enhance metastatic colonization. Some lymphokines are downregulated to suppress tumor progression by enhancing cytotoxic T cell activity and inhibiting tumor cell survival. In this review, we will describe the structure/function of several cytokine families and review our current understanding on the roles and mechanisms of cytokines in tumor progression. In addition, we will also discuss strategies for exploiting the expression and activity of cytokines in therapeutic intervention.

Rotavirus Strategies Against the Innate Antiviral System

"Rotaviruses represent the most important etiological agents of acute, severe gastroenteritis in the young of many animal species, including humans." This statement, variations of which are a common beginning in articles about rotaviruses, reflects the fact that these viruses have evolved efficient strategies for evading the innate immune response of the host and for successfully replicating in the population. In this review, we summarize what is known about the defense mechanisms that host cells employ to prevent rotavirus invasion and the countermeasures that these viruses have successfully developed to surpass cellular defenses. Rotaviruses use at least two viral multifunctional proteins to directly interact with, and prevent the activation of, the interferon system, and they use at least one other protein to halt the protein synthesis machinery and prevent the expression of most of the transcriptional antiviral program of the cell. Characterization of the confrontation between rotaviruses and their host cells has allowed us to learn about the virus-host coevolution that prevents the damaging effects of the innate immune response.

Response of immune response genes to adjuvants poly [di(sodium carboxylatoethylphenoxy)phosphazene] (PCEP), CpG oligodeoxynucleotide and emulsigen at intradermal injection site in pigs

Understanding the mechanisms by which adjuvants mediate their effects provide critical information on how innate immunity influences the development of adaptive immunity. Despite being a critical vaccine component, the mechanisms by which adjuvants mediate their effects are not fully understood and this is especially true when they are used in large animals. This lack of understanding limits our ability to design effective vaccines. In the present study, we administered polyphosphazene (PCEP), CpG oligodeoxynucleotides (CpG), emulsigen or saline via an intradermal injection into pigs and assessed the impact on the expression of reported 'adjuvant response genes' over time. CpG induced a strong upregulation of the chemokine CXL10 several 'Interferon Response Genes', as well as TNFα, and IL-10, and a down-regulation of IL-17 genes. Emulsigen upregulated expression of chemokines CCL2 and CCL5, proinflammatory cytokines IL-6 and TNFα, as well as TLR9, and several IFN response genes. PCEP induced the expression of chemokine CCL2 and proinflammatory cytokine IL-6. These results suggest that emulsigen and CpG may promote recruitment of innate immune cells and Th1 type cytokine production but that PCEP may promote a Th-2 type immune response through the induction of IL-6, an inducer of B cell activity and differentiation.

MicroRNA profile analysis of host cells before and after wild human rotavirus infection

Rotavirus infection is an important cause of acute gastroenteritis in children, but the interaction between rotavirus and host cells is not completely understood. We isolated a wildtype (wt) rotavirus strain, ZTR-68(P [8] G1), which is derived from an infant with diarrhea in southwest China in 2010. In this study, we investigated host cellular miRNA expression profiles changes in response to ZTR-68 in early stage of infection to investigate the role of miRNAs upon rotavirus infection. Differentially expressed miRNAs were identified by deep sequencing and qRT-PCR and the function of their targets predicted by Gene Ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation. A total of 36 candidate miRNAs were identified. Comparative analysis indicated that 29 miRNAs were significantly down-regulated and 7 were up-regulated after infection. The data were provided contrasting the types of microRNAs in two different permissive cell lines (HT29 and MA104). The target assays results showed that mml-miR-7 and mml-miR-125a are involved in anti-rotavirus and virus-host interaction in host cells. These results offer clues for identifying potential candidates in vector-based antiviral strategies. J. Med. Virol. 88:1497-1510, 2016. © 2016 Wiley Periodicals, Inc.

Rotavirus NSP6 localizes to mitochondria via a predicted N-terminal α-helix

Specific roles have been ascribed to each of the 12 known rotavirus proteins apart from the non-structural protein 6 (NSP6). However, NSP6 may be present at sites of viral replication within the cytoplasm. Here we report that NSP6 from diverse species of rotavirus A localizes to mitochondria via conserved sequences in a predicted N-terminal α-helix. This suggests that NSP6 may affect mitochondrial functions during rotavirus infection.

Innate immune responses to rotavirus infection in macrophages depend on MAVS but involve neither the NLRP3 inflammasome nor JNK and p38 signaling pathways

Rotavirus infection is a major cause of life-threatening infantile gastroenteritis. The innate immune system provides an immediate mechanism of suppressing viral replication and is necessary for an effective adaptive immune response. Innate immunity involves host recognition of viral infection and establishment of a powerful antiviral state through the expression of pro-inflammatory cytokines such as type-1 interferon (IFN). Macrophages, the front-line cells of innate immunity, produce IFN and other cytokines in response to viral infection. However, the role of macrophages during rotavirus infection is not well defined. We demonstrate here that RRV rotavirus triggers the production of proinflammatory cytokines from mouse bone marrow-derived macrophages. IFN and antiviral cytokine production was abolished in rotavirus-infected MAVS (-/-) macrophages. This indicates that rotavirus triggers innate immunity in macrophages through RIG-I and/or MDA5 viral recognition, and MAVS signaling is essential for cytokine responses in macrophages. Rotavirus induced IFN expression in both wild type and MDA5 (-/-) macrophages, showing that MDA5 is not essential for IFN secretion following infection, and RIG-I and MDA5 may act redundantly in promoting rotavirus recognition. Interestingly, rotavirus neither stimulated mitogen-activated protein kinases p38 and JNK nor activated the NLRP3 inflammasome, demonstrating that these components might not be involved in innate responses to rotavirus infection in macrophages. Our results indicate that rotavirus elicits intracellular signaling in macrophages, resulting in the induction of IFN and antiviral cytokines, and advance our understanding of the involvement of these cells in innate responses against rotavirus.

Silencing the alarms: Innate immune antagonism by rotavirus NSP1 and VP3

The innate immune response involves a broad array of pathogen sensors that stimulate the production of interferons (IFNs) to induce an antiviral state. Rotavirus, a significant cause of childhood gastroenteritis and a member of the Reoviridae family of segmented, double-stranded RNA viruses, encodes at least two direct antagonists of host innate immunity: NSP1 and VP3. NSP1, a putative E3 ubiquitin ligase, mediates the degradation of cellular factors involved in both IFN induction and downstream signaling. VP3, the viral capping enzyme, utilizes a 2H-phosphodiesterase domain to prevent activation of the cellular oligoadenylate synthase (OAS)/RNase L pathway. Computational, molecular, and biochemical studies have provided key insights into the structural and mechanistic basis of innate immune antagonism by NSP1 and VP3 of group A rotaviruses (RVA). Future studies with non-RVA isolates will be essential to understand how other rotavirus species evade host innate immune responses.

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Rotavirus NSP1 and VP3 directly antagonize host innate immune pathways.

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NSP1, a putative E3 ubiquitin ligase, mediates turnover of multiple immune factors.

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VP3, the viral capping enzyme, has phosphodiesterase activity to block OAS/RNase L.

NSP1 of human rotaviruses commonly inhibits NF-κB signalling by inducing β-TrCP degradation

Rotavirus is a leading cause of severe gastroenteritis in infants worldwide. Rotavirus nonstructural protein 1 (NSP1) is a virulence factor that inhibits innate host immune responses. NSP1 from some rotaviruses targets host interferon response factors (IRFs), leading to inhibition of type I interferon expression. A few rotaviruses encode an NSP1 that inhibits the NF-κB pathway by targeting β-TrCP, a protein required for IκB degradation and NF-κB activation. Available evidence suggests that these NSP1 properties involve proteosomal degradation of target proteins. We show here that NSP1 from several human rotaviruses and porcine rotavirus CRW-8 inhibits the NF-κB pathway, but cannot degrade IRF3. Furthermore, β-TrCP levels were much reduced in cells infected with these rotaviruses. This provides strong evidence that β-TrCP degradation is required for NF-κB pathway inhibition by NSP1 and demonstrates the relevance of β-TrCP degradation to rotavirus infection. C-terminal regions of NSP1, including a serine-containing motif resembling the β-TrCP recognition motif of IκB, were required for NF-κB inhibition. CRW-8 infection of HT-29 intestinal epithelial cells induced significant levels of IFN-β and CCL5 but not IL-8. This contrasts with monkey rotavirus SA11-4F, whose NSP1 inhibits IRF3 but not NF-κB. Substantial amounts of IL-8 but not IFN-β or CCL5 were secreted from HT-29 cells infected with SA11-4F. Our results show that human rotaviruses commonly inhibit the NF-κB pathway by degrading β-TrCP and thus stabilizing IκB. They suggest that NSP1 plays an important role during human rotavirus infection by inhibiting the expression of NF-κB-dependent cytokines, such as IL-8.