The human respiratory syncytial virus nonstructural protein 1 regulates type I and type II interferon pathways

The implication of infection with respiratory syncytial virus in pediatric recurrent wheezing and asthma: knowledge expanded post-COVID-19 era

BACKGROUND

Respiratory syncytial virus (RSV) infection has been identified to serve as the primary cause of acute lower respiratory infectious diseases in children under the age of one and a significant risk factor for the emergence and development of pediatric recurrent wheezing and asthma, though the exact mechanism is still unknown.

METHODS AND RESULTS

In this study, we discuss the key routes that lead to recurrent wheezing and bronchial asthma following RSV infection. It is interesting to note that following the coronavirus disease 2019 (COVID-19) epidemic, the prevalence of RSV changes significantly. This presents us with a rare opportunity to better understand the associated mechanism for RSV infection, its effects on the respiratory system, and the immunological response to RSV following the COVID-19 epidemic. To better understand the associated mechanisms in the occurrence and progression of pediatric asthma, we thoroughly described how the RSV infection directly destroys the physical barrier of airway epithelial tissue, promotes inflammatory responses, enhances airway hyper-responsiveness, and ultimately causes the airway remodeling. More critically, extensive discussion was also conducted regarding the potential impact of RSV infection on host pulmonary immune response.

CONCLUSION

In conclusion, this study offers a comprehensive perspective to better understand how the RSV infection interacts in the control of the host's pulmonary immune system, causing recurrent wheezing and the development of asthma, and it sheds fresh light on potential avenues for pharmaceutical therapy in the future.

Pathogenicity and virulence of human respiratory syncytial virus: Multifunctional nonstructural proteins NS1 and NS2

Human respiratory syncytial virus (hRSV) is a major cause of acute lower respiratory tract infections in children under the age of two as well as in the elderly and immunocompromised worldwide. Despite its discovery over 60 years ago and the global impact on human health, limited specific and effective prophylactic or therapeutic options have been available for hRSV infections. Part of the lack of treatment options is attributed to the legacy of vaccine failure in the 1960s using a formalin-inactivated RSV (FI-RSV), which led to enhancement of disease post exposure to hRSV infection and hampered subsequent development of vaccine candidates. Recent FDA approval of a vaccine for older adults and impending approval for a maternal vaccine are major advancements but leaves children between 6 months and 5 years of age unprotected. Part of this limitation can be attributed to a lack of complete understanding of the factors that contribute to hRSV pathogenesis. The nonstructural proteins NS1 and NS2 are multifunctional virulence factors that are unique to hRSV and that play critical roles during hRSV infection, including antagonizing interferon (IFN) signalling to modulate host responses to hRSV infection. However, the molecular mechanisms by which the nonstructural proteins mediate their IFN inhibitory functions have not been completely defined. Current progress on the characterization of NS1 and NS2 during infection provides deeper insight into their roles. Furthermore, reverse genetics systems for hRSV provide a viable strategy to generate attenuated viruses by introduction of select mutations while maintaining immunogenicity required to elicit a long-term protective response. Here we will review the current state of knowledge of the nonstructural proteins, their contributions to RSV pathogenesis, and their potential as targets for therapeutic development.

Current Landscape of IFN-λ: Induction, Inhibition, and Potential Clinical Applications to Treat Respiratory Viral Infections

IFN-λ or type III IFN is an important mediator of antiviral response. Several respiratory viruses induce the production of IFN-λ during their course of infection. However, they have also developed intricate mechanisms to inhibit its expression and activity. Despite a considerable amount of research on the regulatory mechanisms of respiratory viruses on the IFN-λ response, little is still known about the effect of this cytokine on immune cells and the antiviral effects of all IFN-λ isoforms, and a better understanding of the detrimental effects of IFN-λ treatment is required. Here we highlight the relevance of IFN-λ as an antiviral cytokine in the respiratory tract. Data from studies in vitro, ex vivo, experimental animal models, and ongoing clinical trials emphasize the therapeutic opportunity that IFN-λ represents to treat and prevent different types of respiratory viral infections.

Viral RNA N6-methyladenosine modification modulates both innate and adaptive immune responses of human respiratory syncytial virus

Human respiratory syncytial virus (RSV) is the leading cause of respiratory tract infections in humans. A well-known challenge in the development of a live attenuated RSV vaccine is that interferon (IFN)-mediated antiviral responses are strongly suppressed by RSV nonstructural proteins which, in turn, dampens the subsequent adaptive immune responses. Here, we discovered a novel strategy to enhance innate and adaptive immunity to RSV infection. Specifically, we found that recombinant RSVs deficient in viral RNA N6-methyladenosine (m6A) and RSV grown in m6A methyltransferase (METTL3)-knockdown cells induce higher expression of RIG-I, bind more efficiently to RIG-I, and enhance RIG-I ubiquitination and IRF3 phosphorylation compared to wild-type virion RNA, leading to enhanced type I IFN production. Importantly, these m6A-deficient RSV mutants also induce a stronger IFN response in vivo, are significantly attenuated, induce higher neutralizing antibody and T cell immune responses in mice and provide complete protection against RSV challenge in cotton rats. Collectively, our results demonstrate that inhibition of RSV RNA m6A methylation enhances innate immune responses which in turn promote adaptive immunity.

Evolution of proteomics technologies for understanding respiratory syncytial virus pathogenesis

Introduction: Respiratory syncytial virus (RSV) is a major human pathogen associated with long term morbidity. RSV replication occurs primarily in the epithelium, producing a complex cellular response associated with acute inflammation and long-lived changes in pulmonary function and allergic disease. Proteomics approaches provide important insights into post-transcriptional regulatory processes including alterations in cellular complexes regulating the coordinated innate response and epigenome.Areas covered: Peer-reviewed proteomics studies of host responses to RSV infections and proteomics techniques were analyzed. Methodologies identified include 1)." bottom-up" discovery proteomics, 2). Organellar proteomics by LC-gel fractionation; 3). Dynamic changes in protein interaction networks by LC-MS; and 4). selective reaction monitoring MS. We introduce recent developments in single-cell proteomics, top-down mass spectrometry, and photo-cleavable surfactant chemistries that will have impact on understanding how RSV induces extracellular matrix (ECM) composition and airway remodeling.Expert opinion: RSV replication induces global changes in the cellular proteome, dynamic shifts in nuclear proteins, and remodeling of epigenetic regulatory complexes linked to the innate response. Pathways discovered by proteomics technologies have led to deeper mechanistic understanding of the roles of heat shock proteins, redox response, transcriptional elongation complex remodeling and ECM secretion remodeling in host responses to RSV infections and pathological sequelae.

Gene signature of children with severe respiratory syncytial virus infection

BACKGROUND

The limited treatment options for children with severe respiratory syncytial virus (RSV) infection highlights the need for a comprehensive understanding of the host cellular response during infection. We aimed to identify host genes that are associated with severe RSV disease and to identify drugs that can be repurposed for the treatment of severe RSV infection.

METHODS

We examined clinical data and blood samples from 37 hospitalized children (29 mild and 8 severe) with RSV infection. We tested RNA from blood samples using next-generation sequencing to profile global mRNA expression and identify cellular processes.

RESULTS

Retractions, decreased breath sounds, and tachypnea were associated with disease severity. We observed upregulation of genes related to neutrophil, inflammatory response, blood coagulation, and downregulation of genes related to T cell response in children with severe RSV. Using network-based approach, 43 drugs were identified that are predicted to interact with the gene products of these differentially expressed genes.

CONCLUSIONS

These results suggest that the changes in the expression pattern in the innate and adaptive immune responses may be associated with RSV clinical severity. Compounds that target these cellular processes can be repositioned as candidate drugs in the treatment of severe RSV.

IMPACT

Neutrophil, inflammation, and blood coagulation genes are upregulated in children with severe RSV infection. Expression of T cell response genes are suppressed in cases of severe RSV. Genes identified in this study can contribute in understanding the pathogenesis of RSV disease severity. Drugs that target cellular processes associated with severe RSV can be repositioned as potential therapeutic options.

Revisiting respiratory syncytial virus's interaction with host immunity, towards novel therapeutics

Every year there are > 33 million cases of Respiratory Syncytial Virus (RSV)-related respiratory infection in children under the age of five, making RSV the leading cause of lower respiratory tract infection (LRTI) in infants. RSV is a global infection, but 99% of related mortality is in low/middle-income countries. Unbelievably, 62 years after its identification, there remains no effective treatment nor vaccine for this deadly virus, leaving infants, elderly and immunocompromised patients at high risk. The success of all pathogens depends on their ability to evade and modulate the host immune response. RSV has a complex and intricate relationship with our immune systems, but a clearer understanding of these interactions is essential in the development of effective medicines. Therefore, in a bid to update and focus our research community's understanding of RSV's interaction with immune defences, this review aims to discuss how our current knowledgebase could be used to combat this global viral threat.

Function and Modulation of Type I Interferons during Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory infections in infants and young children, accounting for an estimated 3 million hospitalizations annually worldwide. Despite the major health burden, there is currently no licensed RSV vaccine. RSV is recognized by a range of cellular receptors including both toll-like receptors (TLR) and retinoic acid-inducible gene-I-like receptors (RIG-I). This interaction initiates signaling through mitochondrial antiviral signaling (MAVS) and interferon regulatory factor (IRF) proteins, resulting in the induction of type I interferons (IFN). Early viral control is mediated by either IFN-α or IFN-β signaling through the IFN receptor (IFNAR), inducing the production of antiviral interferon-stimulating genes (ISGs). Type I IFNs also initiate the early production of proinflammatory cytokines including interleukin 6 (IL-6), tumor necrosis factor (TNF), and IFN-γ. Type I IFN levels correlate with age, and inadequate production may be a critical factor in facilitating the increased RSV disease severity observed in infants. Here, we review the current literature on the function of type I IFNs in RSV pathogenesis, as well as their involvement in the differential immune responses observed in infants and adults.

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Importance of Virus Characteristics in Respiratory Syncytial Virus-Induced Disease

Severe lower respiratory tract infection in infants and young children is most frequently caused by respiratory syncytial virus (RSV). RSV infects the smallest airways, making breathing difficult and in some infants requiring medical support. Severity is affected by viral dose, infant age, virus genotype, and effectiveness of the innate/adaptive immune responses. Severe disease correlates with later wheezing and asthma in some children. The adaptive immune response is protective but wanes after each infection, likely due to the ability of the RSV NS1/NS2 proteins to inhibit the innate immune response. Several vaccine approaches and candidates are currently in clinical trials.

Proteomic analysis of Plasmodium falciparum histone deacetylase 1 complex proteins

Plasmodium falciparum histone deacetylases (PfHDACs) are an important class of epigenetic regulators that alter protein lysine acetylation, contributing to regulation of gene expression and normal parasite growth and development. PfHDACs are therefore under investigation as drug targets for malaria. Despite this, our understanding of the biological roles of these enzymes is only just beginning to emerge. In higher eukaryotes, HDACs function as part of multi-protein complexes and act on both histone and non-histone substrates. Here, we present a proteomics analysis of PfHDAC1 immunoprecipitates, identifying 26 putative P. falciparum complex proteins in trophozoite-stage asexual intraerythrocytic parasites. The co-migration of two of these (P. falciparum heat shock proteins 70-1 and 90) with PfHDAC1 was validated using Blue Native PAGE combined with Western blot. These data provide a snapshot of possible PfHDAC1 interactions and a starting point for future studies focused on elucidating the broader function of PfHDACs in Plasmodium parasites.

Redox Biology of Respiratory Viral Infections

Respiratory viruses cause infections of the upper or lower respiratory tract and they are responsible for the common cold—the most prevalent disease in the world. In many cases the common cold results in severe illness due to complications, such as fever or pneumonia. Children, old people, and immunosuppressed patients are at the highest risk and require fast diagnosis and therapeutic intervention. However, the availability and efficiencies of existing therapeutic approaches vary depending on the virus. Investigation of the pathologies that are associated with infection by respiratory viruses will be paramount for diagnosis, treatment modalities, and the development of new therapies. Changes in redox homeostasis in infected cells are one of the key events that is linked to infection with respiratory viruses and linked to inflammation and subsequent tissue damage. Our review summarizes current knowledge on changes to redox homeostasis, as induced by the different respiratory viruses.

Role of p53/NF-κB functional balance in respiratory syncytial virus-induced inflammation response

The interplay between respiratory syncytial virus (RSV) and the p53 pathway has only been reported in a limited number of studies, yet the underlying abrogation mechanisms of p53 activity during the time course of infection, possibly involving viral proteins, remained unclear. Here, we demonstrate that RSV infection impairs global p53 transcriptional activity, notably via its proteasome-dependent degradation at late stages of infection. We also demonstrate that NS1 and NS2 contribute to the abrogation of p53 activity, and used different experimental strategies (e.g. siRNA, small molecules) to underline the antiviral contribution of p53 in the context of RSV infection. Notably, our study highlights a strong RSV-induced disequilibrium of the p53/NF-κB functional balance, which appears to contribute to the up-regulation of the expression of several proinflammatory cytokines and chemokines.

Modulation of Host Immunity by Human Respiratory Syncytial Virus Virulence Factors: A Synergic Inhibition of Both Innate and Adaptive Immunity

The Human Respiratory Syncytial Virus (hRSV) is a major cause of acute lower respiratory tract infections (ARTIs) and high rates of hospitalizations in children and in the elderly worldwide. Symptoms of hRSV infection include bronchiolitis and pneumonia. The lung pathology observed during hRSV infection is due in part to an exacerbated host immune response, characterized by immune cell infiltration to the lungs. HRSV is an enveloped virus, a member of the Pneumoviridae family, with a non-segmented genome and negative polarity-single RNA that contains 10 genes encoding for 11 proteins. These include the Fusion protein (F), the Glycoprotein (G), and the Small Hydrophobic (SH) protein, which are located on the virus surface. In addition, the Nucleoprotein (N), Phosphoprotein (P) large polymerase protein (L) part of the RNA-dependent RNA polymerase complex, the M2-1 protein as a transcription elongation factor, the M2-2 protein as a regulator of viral transcription and (M) protein all of which locate inside the virion. Apart from the structural proteins, the hRSV genome encodes for the non-structural 1 and 2 proteins (NS1 and NS2). HRSV has developed different strategies to evade the host immunity by means of the function of some of these proteins that work as virulence factors to improve the infection in the lung tissue. Also, hRSV NS-1 and NS-2 proteins have been shown to inhibit the activation of the type I interferon response. Furthermore, the hRSV nucleoprotein has been shown to inhibit the immunological synapsis between the dendritic cells and T cells during infection, resulting in an inefficient T cell activation. Here, we discuss the hRSV virulence factors and the host immunological features raised during infection with this virus.

Structural basis for human respiratory syncytial virus NS1-mediated modulation of host responses

Human respiratory syncytial virus (hRSV) is a major cause of morbidity and mortality in the paediatric, elderly and immune-compromised populations^1,2. A gap in our understanding of hRSV disease pathology is the interplay between virally encoded immune antagonists and host components that limit hRSV replication. hRSV encodes for non-structural (NS) proteins that are important immune antagonists^3-6; however, the role of these proteins in viral pathogenesis is incompletely understood. Here, we report the crystal structure of hRSV NS1 protein, which suggests that NS1 is a structural paralogue of hRSV matrix (M) protein. Comparative analysis of the shared structural fold with M revealed regions unique to NS1. Studies on NS1 wild type or mutant alone or in recombinant RSVs demonstrate that structural regions unique to NS1 contribute to modulation of host responses, including inhibition of type I interferon responses, suppression of dendritic cell maturation and promotion of inflammatory responses. Transcriptional profiles of A549 cells infected with recombinant RSVs show significant differences in multiple host pathways, suggesting that NS1 may have a greater role in regulating host responses than previously appreciated. These results provide a framework to target NS1 for therapeutic development to limit hRSV-associated morbidity and mortality.

Ankyrin Repeat Proteins of Orf Virus Influence the Cellular Hypoxia Response Pathway

Hypoxia-inducible factor (HIF) is a transcriptional activator with a central role in regulating cellular responses to hypoxia. It is also emerging as a major target for viral manipulation of the cellular environment. Under normoxic conditions, HIF is tightly suppressed by the activity of oxygen-dependent prolyl and asparaginyl hydroxylases. The asparaginyl hydroxylase active against HIF, factor inhibiting HIF (FIH), has also been shown to hydroxylate some ankyrin repeat (ANK) proteins. Using bioinformatic analysis, we identified the five ANK proteins of the parapoxvirus orf virus (ORFV) as potential substrates of FIH. Consistent with this prediction, coimmunoprecipitation of FIH was detected with each of the ORFV ANK proteins, and for one representative ORFV ANK protein, the interaction was shown to be dependent on the ANK domain. Immunofluorescence studies revealed colocalization of FIH and the viral ANK proteins. In addition, mass spectrometry confirmed that three of the five ORFV ANK proteins are efficiently hydroxylated by FIH in vitro While FIH levels were unaffected by ORFV infection, transient expression of each of the ORFV ANK proteins resulted in derepression of HIF-1α activity in reporter gene assays. Furthermore, ORFV-infected cells showed upregulated HIF target gene expression. Our data suggest that sequestration of FIH by ORFV ANK proteins leads to derepression of HIF activity. These findings reveal a previously unknown mechanism of viral activation of HIF that may extend to other members of the poxvirus family.

IMPORTANCE

The protein-protein binding motif formed from multiple repeats of the ankyrin motif is common among chordopoxviruses. However, information on the roles of these poxviral ankyrin repeat (ANK) proteins remains limited. Our data indicate that the parapoxvirus orf virus (ORFV) is able to upregulate hypoxia-inducible factor (HIF) target gene expression. This response is mediated by the viral ANK proteins, which sequester the HIF regulator FIH (factor inhibiting HIF). This is the first demonstration of any viral protein interacting directly with FIH. Our data reveal a new mechanism by which viruses reprogram HIF, a master regulator of cellular metabolism, and also show a new role for the ANK family of poxvirus proteins.

Proteoform-Specific Insights into Cellular Proteome Regulation

Knowledge regarding compositions of proteomes at the proteoform level enhances insights into cellular phenotypes. A strategy is described herein for discovery of proteoform-specific information about cellular proteomes. This strategy involved analysis of data obtained by bottom-up mass spectrometry of multiple protein OGE separations on a fraction by fraction basis. The strategy was exemplified using five matched sets of lysates of uninfected and human respiratory syncytial virus-infected A549 cells. Template matching demonstrated that 67.3% of 10475 protein profiles identified focused to narrow pI windows indicative of efficacious focusing. Furthermore, correlation between experimental and theoretical pI gradients indicated reproducible focusing. Based on these observations a proteoform profiling strategy was developed to identify proteoforms, detect proteoform diversity and discover potential proteoform regulation. One component of this strategy involved examination of the focusing profiles for protein groups. A novel concordance analysis facilitated differentiation between proteoforms, including proteoforms generated by alternate splicing and proteolysis. Evaluation of focusing profiles and concordance analysis were applicable to cells from a single and/or multiple biological states. Statistical analyses identified proteoform variation between biological states. Regulation relevant to cellular responses to human respiratory syncytial virus was revealed. Western blotting and Protomap analyses validated the proteoform regulation. Discovery of STAT1, WARS, MX1, and HSPB1 proteoform regulation by human respiratory syncytial virus highlighted the impact of the profiling strategy. Novel truncated proteoforms of MX1 were identified in infected cells and phosphorylation driven regulation of HSPB1 proteoforms was correlated with infection. The proteoform profiling strategy is generally applicable to investigating interactions between viruses and host cells and the analysis of other biological systems.

Comprehensive Annotation of the Parastagonospora nodorum Reference Genome Using Next-Generation Genomics, Transcriptomics and Proteogenomics

Parastagonospora nodorum, the causal agent of Septoria nodorum blotch (SNB), is an economically important pathogen of wheat (Triticum spp.), and a model for the study of necrotrophic pathology and genome evolution. The reference P. nodorum strain SN15 was the first Dothideomycete with a published genome sequence, and has been used as the basis for comparison within and between species. Here we present an updated reference genome assembly with corrections of SNP and indel errors in the underlying genome assembly from deep resequencing data as well as extensive manual annotation of gene models using transcriptomic and proteomic sources of evidence (https://github.com/robsyme/Parastagonospora_nodorum_SN15). The updated assembly and annotation includes 8,366 genes with modified protein sequence and 866 new genes. This study shows the benefits of using a wide variety of experimental methods allied to expert curation to generate a reliable set of gene models.

Novel insights into human respiratory syncytial virus-host factor interactions through integrated proteomics and transcriptomics analysis

The lack of vaccine and limited antiviral options against respiratory syncytial virus (RSV) highlights the need for novel therapeutic strategies. One alternative is to develop drugs that target host factors required for viral replication. Several microarray and proteomics studies had been published to identify possible host factors that are affected during RSV replication. In order to obtain a comprehensive understanding of RSV-host interaction, we integrated available proteome and transcriptome datasets and used it to construct a virus-host interaction network. Then, we interrogated the network to identify host factors that are targeted by the virus and we searched for drugs from the DrugBank database that interact with these host factors, which may have potential applications in repositioning for future treatment options of RSV infection.

Discovery and characterisation of a new insect-specific bunyavirus from Culex mosquitoes captured in northern Australia

Insect-specific viruses belonging to significant arboviral families have recently been discovered. These viruses appear to be maintained within the insect population without the requirement for replication in a vertebrate host. Mosquitoes collected from Badu Island in the Torres Strait in 2003 were analysed for insect-specific viruses. A novel bunyavirus was isolated in high prevalence from Culex spp. The new virus, provisionally called Badu virus (BADUV), replicated in mosquito cells of both Culex and Aedes origin, but failed to replicate in vertebrate cells. Genomic sequencing revealed that the virus was distinct from sequenced bunyavirus isolates reported to date, but phylogenetically clustered most closely with recently discovered mosquito-borne, insect-specific bunyaviruses in the newly proposed Goukovirus genus. The detection of a functional furin cleavage motif upstream of the two glycoproteins in the M segment-encoded polyprotein suggests that BADUV may employ a unique strategy to process the virion glycoproteins.

Respiratory Syncytial Virus Nonstructural Proteins Upregulate SOCS1 and SOCS3 in the Different Manner from Endogenous IFN Signaling

Respiratory syncytial virus (RSV) infection upregulates genes of the suppressor of cytokine signaling (SOCS) family, which utilize a feedback loop to inhibit type I interferon dependent antiviral signaling pathway. Here, we reconstituted RSV nonstructural (NS) protein expression plasmids (pNS1, pNS2, and pNS1/2) and tested whether NS1 or NS2 would trigger SOCS1 and SOCS3 protein expression. These NS proteins inhibited interferon- (IFN-) α signaling through a mechanism involving the induction of SOCS1 and SOCS3, which appeared to be different from autocrine IFN dependent. NS1 induced both SOCS1 and SOCS3 upregulation, while NS2 only induced SOCS1 expression. The induced expression of SOCS1 and SOCS3 preceded endogenous IFN-signaling activation and inhibited the IFN-inducible antiviral response as well as chemokine induction. Treatments with INF-α and NS proteins both induced SOCS1 expression; however, they had opposing effects on IFN-α-dependent antiviral gene expression. Our results indicate that NS1 and NS2, which induce the expression of SOCS1 or SOCS3, might represent an independent pathway of stimulating endogenous IFN signaling.

Mass spectrometry identification of age-associated proteins from the malaria mosquitoes Anopheles gambiae s.s. and Anopheles stephensi

This study investigated proteomic changes occurring in Anopheles gambiae and Anopheles stephensi during adult mosquito aging. These changes were evaluated using two-dimensional difference gel electrophoresis (2D-DIGE) and the identities of aging related proteins were determined using capillary high-pressure liquid chromatography (capHPLC) coupled with a linear ion-trap (LTQ)-Orbitrap XL hybrid mass spectrometry (MS). Here, we have described the techniques used to determine age associated proteomic changes occurring in heads and thoraces across three age groups; 1, 9 and 17 d old A. gambiae and 4 age groups; 1, 9, 17 and 34 d old A. stephensi. We have provided normalised spot volume raw data for all protein spots that were visible on 2D-DIGE images for both species and processed Orbitrap mass spectrometry data. For public access, mass spectrometry raw data are available via ProteomeXchange with identifier PXD002153. A detailed description of this study has been described elsewhere [1].

Shp-2 contributes to anti-RSV activity in human pulmonary alveolar epithelial cells by interfering with the IFN-α-induced Jak/Stat1 pathway

Src homology phosphotyrosyl phosphatase 2 (Shp-2) is a ubiquitously expressed protein that is involved in a variety of cellular processes, including antiviral interferon signalling pathways. In this study, we investigated the role of Shp-2 in the host cell interactions of human respiratory syncytial virus (RSV). We report significant changes in the expression of Shp-2 in human pulmonary alveolar epithelial cells (A549) upon RSV infection. We also report that blocking Shp-2 does not affect viral replication or virus-induced interferon-alpha (IFN-α) production. Interestingly, whereas A549 cells were activated by IFN-α, the blocking of Shp-2 resulted in increased viral replication that was associated with the reduced expression of the IFN-stimulated genes of 2',5'-oligoadenylate synthetases and Mx1, and the concomitant inhibition of Stat1 tyrosine phosphorylation. Our findings suggest that Shp-2 contributes to the control of RSV replication and progeny production in pulmonary alveolar epithelial cells by interfering with IFN-α-induced Jak/Stat1 pathway activation rather than by affecting the production of IFN-α itself.

Proteomic changes occurring in the malaria mosquitoes Anopheles gambiae and Anopheles stephensi during aging

The age of mosquitoes is a crucial determinant of their ability to transmit pathogens and their resistance to insecticides. We investigated changes to the abundance of proteins found in heads and thoraces of the malaria mosquitoes Anopheles gambiae and Anopheles stephensi as they aged. Protein expression changes were assessed using two-dimensional difference gel electrophoresis and the identity of differentially expressed proteins was determined by using either matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometry or capillary high-pressure liquid chromatography coupled with a linear ion-trap (LTQ)-Orbitrap XL hybrid mass spectrometer. Protein biomarkers were validated by semi quantitative Western blot analysis. Nineteen and nine age dependent protein spots were identified for A. stephensi and A. gambiae, respectively. Among the proteins down-regulated with age were homologs of ADF/Cofilin, cytochome c1, heat shock protein-70 and eukaryotic translation initiation factor 5A (eIF5a). Proteins up-regulated with age included probable methylmalonate-semialdehyde dehydrogenase, voltage-dependent anion-selective channel and fructose bisphosphate aldolase. Semi quantitative Western blot analysis confirmed expression patterns observed by 2-D DIGE for eIF5a and ADF/Cofilin. Further work is recommended to determine whether these biomarkers are robust to infection, blood feeding and insecticide resistance. Robust biomarkers could then be incorporated into rapid diagnostic assays for ecological and epidemiological studies.

BIOLOGICAL SIGNIFICANCE

In this study, we have identified several proteins with characteristic changes in abundance in both A. gambiae and A. stephensi during their aging process. These changes may highlight underlying mechanisms beneath the relationship between mosquito age and factors affecting Plasmodium transmission and mosquito control. The similarity of changes in protein abundance between these species and the primary dengue vector Aedes aegypti, has revealed conserved patterns of aging-specific protein regulation.

The Chikungunya Virus Capsid Protein Contains Linear B Cell Epitopes in the N- and C-Terminal Regions that are Dependent on an Intact C-Terminus for Antibody Recognition

Chikungunya virus (CHIKV) is an arthropod-borne agent that causes severe arthritic disease in humans and is considered a serious health threat in areas where competent mosquito vectors are prevalent. CHIKV has recently been responsible for several millions of cases of disease, involving over 40 countries. The recent re-emergence of CHIKV and its potential threat to human health has stimulated interest in better understanding of the biology and pathogenesis of the virus, and requirement for improved treatment, prevention and control measures. In this study, we mapped the binding sites of a panel of eleven monoclonal antibodies (mAbs) previously generated towards the capsid protein (CP) of CHIKV. Using N- and C-terminally truncated recombinant forms of the CHIKV CP, two putative binding regions, between residues 1–35 and 140–210, were identified. Competitive binding also revealed that five of the CP-specific mAbs recognized a series of overlapping epitopes in the latter domain. We also identified a smaller, N-terminally truncated product of native CP that may represent an alternative translation product of the CHIKV 26S RNA and have potential functional significance during CHIKV replication. Our data also provides evidence that the C-terminus of CP is required for authentic antigenic structure of CP. This study shows that these anti-CP mAbs will be valuable research tools for further investigating the structure and function of the CHIKV CP.

A comprehensive proteomic view of responses of A549 type II alveolar epithelial cells to human respiratory syncytial virus infection

Human respiratory syncytial virus is a major respiratory pathogen for which there are no suitable antivirals or vaccines. A better understanding of the host cell response to this virus may redress this problem. The present report concerns analysis of multiple independent biological replicates of control and 24 h infected lysates of A549 cells by two different proteomic workflows. One workflow involved fractionation of lysates by in-solution protein IEF and individual fractions were digested using trypsin prior to capillary HPLC-LTQ-OrbitrapXL-MS/MS. A second workflow involved digestion of whole cell lysates and analysis by nanoUltraHPLC-LTQ-OrbitrapElite-MS/MS. Both workflows resulted in the quantification of viral proteins exclusively in lysates of infected cells in the relative abundances anticipated from previous studies. Unprecedented numbers (3247 - 5010) of host cell protein groups were also quantified and the infection-specific regulation of a large number (191) of these protein groups was evident based on a stringent false discovery rate cut-off (<1%). Bioinformatic analyses revealed that most of the regulated proteins were potentially regulated by type I, II, and III interferon, TNF-α and noncanonical NF-κB2 mediated antiviral response pathways. Regulation of specific protein groups by infection was validated by quantitative Western blotting and the cytokine-/key regulator-specific nature of their regulation was confirmed by comparable analyses of cytokine treated A549 cells. Overall, it is evident that the workflows described herein have produced the most comprehensive proteomic characterization of host cell responses to human respiratory syncytial virus published to date. These workflows will form the basis for analysis of the impacts of specific genes of human respiratory syncytial virus responses of A549 and other cell lines using a gene-deleted version of the virus. They should also prove valuable for the analysis of the impact of other infectious agents on host cells.

Central nervous system alterations caused by infection with the human respiratory syncytial virus

Worldwide, the human respiratory syncytial virus (hRSV) is the leading cause of infant hospitalization because of acute respiratory tract infections, including severe bronchiolitis and pneumonia. Despite intense research, to date there is neither vaccine nor treatment available to control hRSV disease burden globally. After infection, an incubation period of 3-5 days is usually followed by symptoms, such as cough and low-grade fever. However, hRSV infection can also produce a larger variety of symptoms, some of which relate to the individual's age at infection. Indeed, infants can display severe symptoms, such as dyspnea and chest wall retractions. Upon examination, crackles and wheezes are also common features that suggest infection by hRSV. Additionally, infection in infants younger than 1 year is associated with several non-specific symptoms, such as failure to thrive, periodic breathing or apnea, and feeding difficulties that usually require hospitalization. Recently, neurological symptoms have also been associated with hRSV respiratory infection and include seizures, central apnea, lethargy, feeding or swallowing difficulties, abnormalities in muscle tone, strabismus, abnormalities in the CSF, and encephalopathy. Here, we discuss recent findings linking the neurological, extrapulmonary effects of hRSV with infection and functional impairment of the CNS.

Refining the balance of attenuation and immunogenicity of respiratory syncytial virus by targeted codon deoptimization of virulence genes

Respiratory syncytial virus (RSV) is the most important pathogen for lower respiratory tract illness in children for which there is no licensed vaccine. Live-attenuated RSV vaccines are the most clinically advanced in children, but achieving an optimal balance of attenuation and immunogenicity is challenging. One way to potentially retain or enhance immunogenicity of attenuated virus is to mutate virulence genes that suppress host immune responses. The NS1 and NS2 virulence genes of the RSV A2 strain were codon deoptimized according to either human or virus codon usage bias, and the resulting recombinant viruses (dNSh and dNSv, respectively) were rescued by reverse genetics. RSV dNSh exhibited the desired phenotype of reduced NS1 and NS2 expression. RSV dNSh was attenuated in BEAS-2B and primary differentiated airway epithelial cells but not in HEp-2 or Vero cells. In BALB/c mice, RSV dNSh exhibited a lower viral load than did A2, and yet it induced slightly higher levels of RSV-neutralizing antibodies than did A2. RSV A2 and RSV dNSh induced equivalent protection against challenge strains A/1997/12-35 and A2-line19F. RSV dNSh caused less STAT2 degradation and less NF-κB activation than did A2 in vitro. Serial passage of RSV dNSh in BEAS-2B cells did not result in mutations in the deoptimized sequences. Taken together, RSV dNSh was moderately attenuated, more immunogenic, and equally protective compared to wild-type RSV and genetically stable.

Respiratory syncytial virus (RSV) is the leading cause of infant viral death in the United States and worldwide, and no vaccine is available. Live-attenuated RSV vaccines are the most studied in children but have suffered from genetic instability and low immunogenicity. In order to address both obstacles, we selectively changed the codon usage of the RSV nonstructural (NS) virulence genes NS1 and NS2 to the least-used codons in the human genome (deoptimization). Compared to parental RSV, the codon-deoptimized NS1/NS2 RSV was attenuated in vitro and in mice but induced higher levels of neutralizing antibodies and equivalent protection against challenge. We identified a new attenuating module that retains immunogenicity and is genetically stable, achieved through specific targeting of nonessential virulence genes by codon usage deoptimization.

The impact of viral genotype on pathogenesis and disease severity: respiratory syncytial virus and human rhinoviruses

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection (LRI) and viral death in infants. RSV disease in infants is characterized by epithelial desquamation, neutrophilic bronchiolitis and pneumonia and obstructive pulmonary mucus. Human rhinoviruses (HRVs) are by far the most common cause of symptomatic upper respiratory tract infection (URI) in people and are more recently appreciated as a significant cause of LRI. RSV and HRV are also implicated in asthma pathogenesis. Within both RSV and HRV, viral genetic differences play a role in disease severity and/or prevalence in patient populations, and viral genetic differences affect pathogenesis. Here, we review data on how viral genetic differences impact disease using RSV and HRV as examples, including effects on the host immune response. Virus genotype–phenotype relationships can be exploited in the laboratory to gain insight into mechanisms by which respiratory viruses modulate host immune responses and cause disease.

RSV-encoded NS2 promotes epithelial cell shedding and distal airway obstruction

Respiratory syncytial virus (RSV) infection is the major cause of bronchiolitis in young children. The factors that contribute to the increased propensity of RSV-induced distal airway disease compared with other commonly encountered respiratory viruses remain unclear. Here, we identified the RSV-encoded nonstructural 2 (NS2) protein as a viral genetic determinant for initiating RSV-induced distal airway obstruction. Infection of human cartilaginous airway epithelium (HAE) and a hamster model of disease with recombinant respiratory viruses revealed that NS2 promotes shedding of infected epithelial cells, resulting in two consequences of virus infection. First, epithelial cell shedding accelerated the reduction of virus titers, presumably by clearing virus-infected cells from airway mucosa. Second, epithelial cells shedding into the narrow-diameter bronchiolar airway lumens resulted in rapid accumulation of detached, pleomorphic epithelial cells, leading to acute distal airway obstruction. Together, these data indicate that RSV infection of the airway epithelium, via the action of NS2, promotes epithelial cell shedding, which not only accelerates viral clearance but also contributes to acute obstruction of the distal airways. Our results identify RSV NS2 as a contributing factor for the enhanced propensity of RSV to cause severe airway disease in young children and suggest NS2 as a potential therapeutic target for reducing the severity of distal airway disease.

Oxygen-dependent hydroxylation by Factor Inhibiting HIF (FIH) regulates the TRPV3 ion channel

Factor Inhibiting HIF (FIH) is an oxygen-dependent asparaginyl hydroxylase that regulates the hypoxia-inducible factors (HIFs). Several proteins containing ankyrin repeat domains have been characterised as substrates of FIH, although there is little evidence for a functional consequence of hydroxylation on these substrates. This study demonstrates that the transient receptor potential vanilloid 3 (TRPV3) channel is hydroxylated by FIH on asparagine 242 within the cytoplasmic ankyrin repeat domain. Hypoxia, FIH inhibitors and mutation of asparagine 242 all potentiated TRPV3-mediated current, without altering TRPV3 protein levels, indicating that oxygen-dependent hydroxylation inhibits TRPV3 activity. This novel mechanism of channel regulation by oxygen-dependent asparaginyl hydroxylation is likely to extend to other ion channels.

Bovine ephemeral fever rhabdovirus α1 protein has viroporin-like properties and binds importin β1 and importin 7

Bovine ephemeral fever virus (BEFV) is an arthropod-borne rhabdovirus that is classified as the type species of the genus Ephemerovirus. In addition to the five canonical rhabdovirus structural proteins (N, P, M, G, and L), the large and complex BEFV genome contains several open reading frames (ORFs) between the G and L genes (α1, α2/α3, β, and γ) encoding proteins of unknown function. We show that the 10.5-kDa BEFV α1 protein is expressed in infected cells and, consistent with previous predictions based on its structure, has the properties of a viroporin. Expression of a BEFV α1-maltose binding protein (MBP) fusion protein in Escherichia coli was observed to inhibit cell growth and increase membrane permeability to hygromycin B. Increased membrane permeability was also observed in BEFV-infected mammalian cells (but not cells infected with an α1-deficient BEFV strain) and in cells expressing a BEFV α1-green fluorescent protein (GFP) fusion protein, which was shown by confocal microscopy to localize to the Golgi complex. Furthermore, the predicted C-terminal cytoplasmic domain of α1, which contains a strong nuclear localization signal (NLS), was translocated to the nucleus when expressed independently, and in an affinity chromatography assay employing a GFP trap, the full-length α1 was observed to interact specifically with importin β1 and importin 7 but not with importin α3. These data suggest that, in addition to its function as a viroporin, BEFV α1 may modulate components of nuclear trafficking pathways, but the specific role thereof remains unclear. Although rhabdovirus accessory genes occur commonly among arthropod-borne rhabdoviruses, little is known of their functions. Here, we demonstrate that the BEFV α1 ORF encodes a protein which has the structural and functional characteristics of a viroporin. We show that α1 localizes in the Golgi complex and increases cellular permeability. We also show that BEFV α1 binds importin β1 and importin 7, suggesting that it may have a yet unknown role in modulating nuclear trafficking. This is the first functional analysis of an ephemerovirus accessory protein and of a rhabdovirus viroporin.

The non-structural NS1 protein unique to respiratory syncytial virus: a two-state folding monomer in quasi-equilibrium with a stable spherical oligomer

Human respiratory syncytial virus (hRSV) is a major infectious agent that cause pediatric respiratory disease worldwide. Considered one of the main virulence factors of hRSV, NS1 is known to suppress type I interferon response and signaling, thus favoring immune evasion. This, together with the fact that NS1 is unique to hRSV among paramyxoviruses, and that has no homology within databases, prompted us to investigate its conformational stability, equilibria and folding. Temperature cooperatively induces conformational changes leading to soluble spherical oligomers (NS1SOs) with amyloid-like or repetitive ß-sheet structures. The onset of the thermal transition is 45°C, and the oligomerization rate is increased by 25-fold from 40 to 46°C. Conformational stability analyzed by chemical perturbation of the NS1 monomer shows a two-state, highly reversible and cooperative unfolding, with a denaturant midpoint of 3.8 M, and a free energy change of 9.6±0.9 kcal⋅mol⁻¹. However, two transitions were observed in the chemical perturbation of NS1SOs: the first, from 2.0 to 3.0 M of denaturant, corresponds to a conformational transition and dissociation of the oligomers to the native monomer, indicating a substantial energy barrier. The second transition (2.0 to 3.5 M denaturant) corresponds to full unfolding of the native NS1 monomer. In addition, different cosolvent perturbations converged on the formation of ß-sheet enriched soluble oligomeric species, with secondary structure resembling those obtained after mild temperature treatment. Thus, a unique protein without homologs, structure or mechanistic information may switch between monomers and oligomers in conditions compatible with the cellular environment and be potentially modulated by crowding or compartmentalization. NS1 may act as a reservoir for increased levels and impact on protein turnover.

Mitochondrial proteomic analysis of human host cells infected with H3N2 swine influenza virus

Swine influenza viruses (SIV) are zoonotic pathogens that pose a potential threat to human health. In this study, we analyzed the differential mitochondrial proteomes of H3N2 SIV-infected human lung A549 cells using two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) analysis. In the comparative analysis, 24 altered proteins (13 upregulated and 11 downregulated) were identified in the mitochondria of H3N2 SIV-infected cells; these proteins were involved in cell-to-cell signaling and interaction, cellular movement, and post-translational modification. Moreover, the transcriptional profiles of 16 genes corresponding to the identified proteins were estimated by real time RT-PCR. IPA analysis suggested that the differentially expressed proteins were clustered primarily into the mammalian target of rapamycin (mTOR) and d-glucose signaling pathways. In addition, oxidative phosphorylation and integrin signaling appeared to be major pathways modulated in the mitochondria of infected cells. We further demonstrated that apolipoprotein L2 was upregulated in the cytoplasm and translocated to mitochondria during virus infection. These results were verified by Western blot analysis coupled with confocal microscopy. Collectively, the mitochondrial proteome data provide insights to further understand the underlying mechanisms of H3N2 SIV cross-species infection.

BIOLOGICAL SIGNIFICANCE

In recent years, proteomics has emerged as an indispensable tool to unveil the complex molecular events in virology. we firstly perform mitochondrial proteomic profiles of human cells infected with H3N2 subtype SIV to understand virus-host interactions, and 24 differentially expressed proteins in mitochondrial proteomes were identified in SIV-infected cells. The proteins that were identified to have differential expression were involved in cell-to-cell signaling and interaction, post-translational modification, cell morphology, cellular assembly, cell death, and energy production. Furthermore, Western blot analysis and a confocal assay further demonstrated that the cellular protein APOL2 partially co-localized with mitochondria after virus infection. This is a very important discovery in the underlying replication and pathogenesis of SIV which provides a potential target clue for the design of anti-SIV drugs. Our results will inspire basic study on SIV infection and drive the understanding for replication and pathogenesis of SIV to control this disease.

Poly(I:C) inhibits porcine reproductive and respiratory syndrome virus replication in MARC-145 cells via activation of IFIT3

Porcine reproductive and respiratory syndrome virus (PRRSV) is a major cause of heavy economic losses in many swine-producing regions. Current vaccination strategies and antiviral drugs provide only limited protection. Interferon (IFN)-induced protein with tetratricopeptide repeats 3 (IFIT3) has been characterized as the product of a novel antiviral gene and as an important modulator in innate immunity. However, the role of IFIT3 in PRRSV infection is scarcely understood. In this study, polyinosinic-polycytidylic acid (poly(I:C)) inhibited PRRSV replication in MARC-145 cells, following the appearance of increased IFIT3. Overexpression of porcine IFIT3 resulted in a decrease of PRRSV. Knockdown of IFIT3 in MARC-145 cells increased PRRSV replication and impaired the antiviral activity mediated by poly(I:C). Moreover, in the presence or absence of IFIT3, poly(I:C)-induced IFN-β promoter activity was significantly boosted or crippled, respectively. IFIT3, TBK1 and phosphorylation of IRF3 were activated in poly(I:C)-transfected MARC-145 cells. It demonstrated that IFIT3 plays an important role in IFN-β induction in MARC-145 cells, and, when activated, it can inhibit PRRSV replication.

Proteomic biomarkers for ageing the mosquito Aedes aegypti to determine risk of pathogen transmission

Biomarkers of the age of mosquitoes are required to determine the risk of transmission of various pathogens as each pathogen undergoes a period of extrinsic incubation in the mosquito host. Using the 2-D Difference Gel Electrophoresis (2-D DIGE) procedure, we investigated the abundance of up to 898 proteins from the Yellow Fever and dengue virus vector, Aedes aegypti, during ageing. By applying a mixed-effects model of protein expression, we identified five common patterns of abundance change during ageing and demonstrated an age-related decrease in variance for four of these. This supported a search for specific proteins with abundance changes that remain tightly associated with ageing for use as ageing biomarkers. Using MALDI-TOF/TOF mass spectrometry we identified ten candidate proteins that satisfied strict biomarker discovery criteria (identified in two out of three multivariate analysis procedures and in two cohorts of mosquitoes). We validated the abundances of the four most suitable candidates (Actin depolymerising factor; ADF, Eukaryotic initiation factor 5A; eIF5A, insect cuticle protein Q17LN8, and Anterior fat body protein; AFP) using semi-quantitative Western analysis of individual mosquitoes of six ages. The redox-response protein Manganese superoxide dismutase (SOD2) and electron shuttling protein Electron transfer oxidoreductase (ETO) were subject to post-translational modifications affecting their charge states with potential effects on function. For the four candidates we show remarkably consistent decreases in abundance during ageing, validating initial selections. In particular, the abundance of AFP is an ideal biomarker candidate for whether a female mosquito has lived long enough to be capable of dengue virus transmission. We have demonstrated proteins to be a suitable class of ageing biomarkers in mosquitoes and have identified candidates for epidemiological studies of dengue and the evaluation of new disease reduction projects targeting mosquito longevity.

Respiratory syncytial virus mechanisms to interfere with type 1 interferons

Respiratory syncytial virus (RSV) is a member of the Paramyxoviridae family that consists of viruses with nonsegmented negative-strand RNA genome. Infection by these viruses triggers the innate antiviral response of the host, mainly type I interferon (IFN). Essentially all other viruses of this family produce IFN suppressor functions by co-transcriptional RNA editing. In contrast, RSV has evolved two unique nonstructural proteins, NS1 and NS2, to effectively serve this purpose. Together, NS1 and NS2 degrade or sequester multiple signaling proteins that affect both IFN induction and IFN effector functions. While the mechanism of action of NS1 and NS2 is a subject of active research, their effect on adaptive immunity is also being recognized. In this review, we discuss various aspects of NS1 and NS2 function with implications for vaccine design.

Proteomic comparison of mcf-7 tumoursphere and monolayer cultures

Breast cancer is a heterogenous disease, composed of tumour cells with differing gene expressions and phenotypes. Very few antigens have been identified and a better understanding of tumour initiating-cells as targets for therapy is critically needed. Recently, a rare subpopulation of cells within tumours has been described with the ability to: (i) initiate and sustain tumour growth; (ii) resist traditional therapies and allow for secondary tumour dissemination; and (iii) display some of the characteristics of stem cells such as self-renewal. These cells are termed tumour-initiating cells or cancer stem cells, or alternatively, in the case of breast cancer, breast cancer stem cells. Previous studies have demonstrated that breast cancer stem cells can be enriched for in “tumoursphere” culture. Proteomics represents a novel way to investigate protein expression between cells. We hypothesise that characterisation of the proteome of the breast cancer line MCF-7 tumourspheres compared to adherent/differentiated cells identifies proteins of novel interest for further isolating or targeting breast cancer stem cells. We present evidence that: (i) the proteome of adherent cells is different to the proteome of cells grown in sphere medium from either early passage (passage 2) or late passage (passage 5) spheres; (ii) that spheres are enriched in expression of a variety of tumour-relevant proteins (including MUC1 and Galectin-3); and (iii) that targeting of one of these identified proteins (galectin-3) using an inhibitor (N-acetyllactosamine) decreases sphere formation/self-renewal of MCF-7 cancer stem cells in vitro and tumourigenicity in vivo. Hence, proteomic analysis of tumourspheres may find use in identifying novel targets for future therapy. The therapeutic targeting of breast cancer stem cells, a highly clinically relevant sub-population of tumour cells, has the potential to eliminate residual disease and may become an important component of a multi-modality treatment of cancer.

TLR3 ligation protects human astrocytes against oxidative stress

Astrocytic Toll-like receptor 3 (TLR3) plays an important role not only in antiviral response but also in regeneration/healing of the CNS. The present study was undertaken to determine whether the neuroprotective effects of TLR3 signaling also include antioxidative protection. TLR3 ligation in human astrocytes induced protracted resistance of the cells to H(2)O(2) toxicity. Similar resistance was induced by conditioned medium from TLR3-ligated astrocytes indicating the involvement of paracrine signaling mechanisms. Out of 13 major antioxidative genes only the gene encoding superoxide dismutase 2 (SOD2) was postligationally upregulated suggesting that SOD2 is the major enzyme responsible for this protection.

The interactome of the human respiratory syncytial virus NS1 protein highlights multiple effects on host cell biology

Viral proteins can have multiple effects on host cell biology. Human respiratory syncytial virus (HRSV) nonstructural protein 1 (NS1) is a good example of this. During the virus life cycle, NS1 can act as an antagonist of host type I and III interferon production and signaling, inhibit apoptosis, suppress dendritic cell maturation, control protein stability, and regulate transcription of host cell mRNAs, among other functions. It is likely that NS1 performs these different roles through interactions with multiple host cell proteins. To investigate this and identify cellular proteins that could interact with NS1, we used quantitative proteomics in combination with green fluorescent protein (GFP)-trap immunoprecipitation and bioinformatic analysis. This analysis identified 221 proteins that were potentially part of complexes that could interact with NS1, with many of these associated with transcriptional regulation as part of the mediator complex, cell cycle regulation, and other functions previously assigned to NS1. Specific immunoprecipitation using the GFP trap was used to confirm the ability of selected cellular proteins to interact individually with NS1. Infection of A549 cells with recombinant viruses deficient in the expression of NS1 and overexpression analysis both demonstrated that NS1 was necessary and sufficient for the enrichment of cells in the G(1) phase of the cell cycle.