Role of hypercytokinemia in NF-kappaB p50-deficient mice after H5N1 influenza A virus infection

During H5N1 influenza virus infection, proinflammatory cytokines are markedly elevated in the lungs of infected hosts. The significance of this dysregulated cytokine response in H5N1-mediated pathogenesis remains to be determined. To investigate the influence of hypercytokinemia, or "cytokine storm," a transgenic mouse technology was used. The classical NF-kappaB pathway regulates the induction of most proinflammatory cytokines. Deletion of the p50 subunit leads to a markedly reduced expression of the NF-kappaB-regulated cytokines and chemokines. Here we show that H5N1 influenza virus infection of this transgenic mouse model resulted in a lack of hypercytokinemia but not in altered pathogenesis.     

MicroRNA Expression and Virulence in Pandemic Influenza Virus-Infected Mice

The worst known H1N1 influenza pandemic in history resulted in more than 20 million deaths in 1918 and 1919. Although the underlying mechanism causing the extreme virulence of the 1918 influenza virus is still obscure, our previous functional genomics analyses revealed a correlation between the lethality of the reconstructed 1918 influenza virus (r1918) in mice and a unique gene expression pattern associated with severe immune responses in the lungs. Lately, microRNAs have emerged as a class of crucial regulators for gene expression. To determine whether differential expression of cellular microRNAs plays a role in the host response to r1918 infection, we compared the lung cellular “microRNAome” of mice infected by r1918 virus with that of mice infected by a nonlethal seasonal influenza virus, A/Texas/36/91. We found that a group of microRNAs, including miR-200a and miR-223, were differentially expressed in response to influenza virus infection and that r1918 and A/Texas/36/91 infection induced distinct microRNA expression profiles. Moreover, we observed significant enrichment in the number of predicted cellular target mRNAs whose expression was inversely correlated with the expression of these microRNAs. Intriguingly, gene ontology analysis revealed that many of these mRNAs play roles in immune response and cell death pathways, which are known to be associated with the extreme virulence of r1918. This is the first demonstration that cellular gene expression patterns in influenza virus-infected mice may be attributed in part to microRNA regulation and that such regulation may be a contributing factor to the extreme virulence of the r1918.H1N1 influenza A viruses continue to pose serious threats to public health, as exemplified by the ongoing 2009 H1N1 influenza pandemic. The 1918-1919 H1N1 influenza pandemic was even deadlier in comparison, causing more than 20 million deaths worldwide. The keys to unlocking the mystery of the extreme virulence of the 1918 virus were provided with the reconstruction of the virus (reconstructed 1918 influenza virus [r1918]) by reverse genetics (37). The lethality of r1918 has since been examined in both mouse and macaque models (17, 18). Unlike the nonlethal infections of some other H1N1 influenza virus strains, such as A/Texas/36/91 (Tx/91) or A/Kawasaki/173/01 (K173), the r1918 causes severe and lethal pulmonary disease. We subsequently conducted functional genomics analyses that revealed that the extreme virulence of r1918 was correlated with atypical expression of immune response-related genes, including massive induction of cellular genes related to inflammatory response and cell death pathways (17, 18). In spite of these findings, the mechanistic basis for these atypical gene expression patterns remains unknown.Cellular gene expression is a complicated process and is subject to regulation by many cellular factors. As a group of newly identified cellular regulators, microRNAs are known to regulate the expression of a large number of targets, mainly cellular genes. Through mRNA degradation or translational repression of their targets, microRNAs regulate a wide range of crucial physiologic and pathological processes. For example, miR-34a acts as a tumor suppressor by inhibiting the expression of sirt1 (40), whereas miR-21 contributes to myocardial disease by inhibiting the expression of spry1 (36). By targeting zeb1/2, the miR-200 family members play roles in maintaining the epithelial phenotype of cancer cells (27). Furthermore, Let-7s regulates the expression of hbl-1, which drives the developmental progression of epidermal stem cells (5). Cellular microRNAs also play critical roles in virus-host interactions. The cellular microRNA miR-122 is an indispensable factor in supporting hepatitis C virus (HCV) replication (16), whereas miR-196 and miR-296 substantially attenuate viral replication through type I interferon (IFN)-associated pathways in liver cells (28). Furthermore, miR-125b and miR-223 directly target human immunodeficiency virus type 1 (HIV-1) mRNA, thereby attenuating viral gene expression in resting CD4⁺ T cells (14), and miR-198 modulates HIV-1 replication indirectly by repressing the expression of ccnt1 (34), a cellular factor necessary for HIV-1 replication. More importantly, viruses may promote their life cycles by modulating the intracellular environment through actively regulating the expression of multiple cellular microRNAs. For example, human T-cell lymphotropic virus type 1 (HTLV-1) modulates the expression of a number of cellular microRNAs in order to control T-cell differentiation (3). Similarly, human cytomegalovirus (HCMV) selectively manipulates the expression of miR-100 and miR-101 to facilitate its own replication (38). In contrast, the involvement of microRNAs during influenza A virus infection or pathogenesis is largely unknown.To determine whether cellular microRNAs play a role in the host response to influenza virus infection, we performed a systematic profiling of cellular microRNAs in lung tissues from mice infected with r1918 or a nonlethal seasonal influenza virus, Tx/91 (17). We identified a group of microRNAs whose expression patterns differentiated the host response to r1918 and Tx/91 infection. We assessed the potential functions of differentially expressed microRNAs by analyzing the predicted target genes whose expression was inversely correlated with the expression of these microRNAs. Our report provides a new perspective on the contribution of microRNAs to the pathogenesis of lethal 1918 influenza virus infection.     

Altered microRNA expression in COVID-19 patients enables identification of SARS-CoV-2 infection

The host response to SARS-CoV-2 infection provide insights into both viral pathogenesis and patient management. The host-encoded microRNA (miRNA) response to SARS-CoV-2 infection, however, remains poorly defined. Here we profiled circulating miRNAs from ten COVID-19 patients sampled longitudinally and ten age and gender matched healthy donors. We observed 55 miRNAs that were altered in COVID-19 patients during early-stage disease, with the inflammatory miR-31-5p the most strongly upregulated. Supervised machine learning analysis revealed that a three-miRNA signature (miR-423-5p, miR-23a-3p and miR-195-5p) independently classified COVID-19 cases with an accuracy of 99.9%. In a ferret COVID-19 model, the three-miRNA signature again detected SARS-CoV-2 infection with 99.7% accuracy, and distinguished SARS-CoV-2 infection from influenza A (H1N1) infection and healthy controls with 95% accuracy. Distinct miRNA profiles were also observed in COVID-19 patients requiring oxygenation. This study demonstrates that SARS-CoV-2 infection induces a robust host miRNA response that could improve COVID-19 detection and patient management.     

Epigenetic changes mediated by microRNA miR29 activate cyclooxygenase 2 and lambda-1 interferon production during viral infection

Lambda-1 interferon (IFN-λ1) and cyclooxygenase-2 (COX-2) were reported to play an important role in host antiviral defense. However, the mechanism by which IFN-λ1 and COX2 are activated and modulated during viral infection remains unclear. In this study, we found that expression of both circulating IFN-λ1 and COX2-derived prostaglandin E2 (PGE2) was coordinately elevated in a cohort of influenza patients compared to healthy individuals. Expression of IFN-λ1 was blocked by a selective COX2 inhibitor during influenza A virus infection in A549 human lung epithelial cells but enhanced by overexpression of COX2, indicating that the production of IFN-λ1 is COX2 dependent. COX2 was able to increase IFN-λ1 expression by promoting NF-κB binding to the enhancer in the IFN-λ1 promoter. We found that epigenetic changes activate COX2 expression and PGE2 accumulation during viral infection. The expression of DNA methyltransferase 3a (DNMT3a) and DNMT3b, but not that of DNMT1, was downregulated following influenza A virus infection in both A549 cells and peripheral blood mononuclear cells (PBMCs). We showed that microRNA miR29 suppresses DNMT activity and thus induces expression of COX2 and PGE2. Furthermore, miR29 expression was elevated 50-fold in virally infected A549 cells and 10-fold in PBMCs from influenza patients, compared to expression after mock infection of A549 cells or in healthy individuals, respectively. Activation of the protein kinase A signaling pathway and phosphorylation of CREB1 also contributed to COX2 expression. Collectively, our work defines a novel proinflammatory cascade in the control of influenza A virus infection.     

A MicroRNA Network Dysregulated in Asthma Controls IL-6 Production in Bronchial Epithelial Cells

MicroRNAs are short non-coding single stranded RNAs that regulate gene expression. While much is known about the effects of individual microRNAs, there is now growing evidence that they can work in co-operative networks. MicroRNAs are known to be dysregulated in many diseases and affect pathways involved in the pathology. We investigated dysregulation of microRNA networks using asthma as the disease model. Asthma is a chronic inflammatory disease of the airways characterized by bronchial hyperresponsiveness and airway remodelling. The airway epithelium is a major contributor to asthma pathology and has been shown to produce an excess of inflammatory and pro-remodelling cytokines such as TGF-β, IL-6 and IL-8 as well as deficient amounts of anti-viral interferons. After performing microRNA arrays, we found that microRNAs -18a, -27a, -128 and -155 are down-regulated in asthmatic bronchial epithelial cells, compared to cells from healthy donors. Interestingly, these microRNAs are predicted in silico to target several components of the TGF-β, IL-6, IL-8 and interferons pathways. Manipulation of the levels of individual microRNAs in bronchial epithelial cells did not have an effect on any of these pathways. Importantly, knock-down of the network of microRNAs miR-18a, -27a, -128 and -155 led to a significant increase of IL-8 and IL-6 expression. Interestingly, despite strong in silico predictions, down-regulation of the pool of microRNAs did not have an effect on the TGF-β and Interferon pathways. In conclusion, using both bioinformatics and experimental tools we found a highly relevant potential role for microRNA dysregulation in the control of IL-6 and IL-8 expression in asthma. Our results suggest that microRNAs may have different roles depending on the presence of other microRNAs. Thus, interpretation of in silico analysis of microRNA function should be confirmed experimentally in the relevant cellular context taking into account interactions with other microRNAs when studying disease.     

Novel Avian Influenza A (H7N9) Virus Induces Impaired Interferon Responses in Human Dendritic Cells

In March 2013 a new avian influenza A(H7N9) virus emerged in China and infected humans with a case fatality rate of over 30%. Like the highly pathogenic H5N1 virus, H7N9 virus is causing severe respiratory distress syndrome in most patients. Based on genetic analysis this avian influenza A virus shows to some extent adaptation to mammalian host. In the present study, we analyzed the activation of innate immune responses by this novel H7N9 influenza A virus and compared these responses to those induced by the avian H5N1 and seasonal H3N2 viruses in human monocyte-derived dendritic cells (moDCs). We observed that in H7N9 virus-infected cells, interferon (IFN) responses were weak although the virus replicated as well as the H5N1 and H3N2 viruses in moDCs. H7N9 virus-induced expression of pro-inflammatory cytokines remained at a significantly lower level as compared to H5N1 virus-induced “cytokine storm” seen in human moDCs. However, the H7N9 virus was extremely sensitive to the antiviral effects of IFN-α and IFN-β in pretreated cells. Our data indicates that different highly pathogenic avian viruses may show considerable differences in their ability to induce host antiviral responses in human primary cell models such as moDCs. The unexpected appearance of the novel H7N9 virus clearly emphasizes the importance of the global influenza surveillance system. It is, however, equally important to systematically characterize in normal human cells the replication capacity of the new viruses and their ability to induce and respond to natural antiviral substances such as IFNs.     

Epigenetic alteration of microRNAs in DNMT3B-mutated patients of ICF syndrome

Immunodeficiency, Centromeric region instability, Facial anomalies (ICF; OMIM #242860) syndrome, due to mutations in the DNMT3B gene, is characterized by inheritance of aberrant patterns of DNA methylation and heterochromatin defects. Patients show variable agammaglobulinemia and a reduced number of T cells, making them prone to infections and death before adulthood. Other variable symptoms include facial dysmorphism, growth and mental retardation. Despite the recent advances in identifying the dysregulated genes, the molecular mechanisms, which underlie the altered gene expression causing ICF phenotype complexity, are not well understood. Held the recently-shown tight correlation between epigenetics and microRNAs (miRNAs), we searched for miRNAs regulated by DNMT3B activity, comparing cell lines from ICF patients with those from healthy individuals. We observe that eighty-nine miRNAs, some of which involved in immune function, development and neurogenesis, are dysregulated in ICF (LCLs) compared to wild-type cells. Significant DNA hypomethylation of miRNA CpG islands was not observed in cases of miRNA up-regulation in ICF cells, suggesting a more subtle effect of DNMT3B deficiency on their regulation; however, a modification of histone marks, especially H3K27 and H3K4 trimethylation, and H4 acetylation, was observed concomitantly with changes in microRNA expression. Functional correlation between miRNA and mRNA expression of their targets allow us to suppose a regulation either at mRNA level or at protein level. These results provide a better understanding of how DNA methylation and histone code interact to regulate the class of microRNA genes and enable us to predict molecular events possibly contributing to ICF condition.     

Influenza H5N1 and H1N1 Virus Replication and Innate Immune Responses in Bronchial Epithelial Cells Are Influenced by the State of Differentiation

Influenza H5N1 virus continues to be enzootic in poultry and transmits zoonotically to humans. Although a swine-origin H1N1 virus has emerged to become pandemic, its virulence for humans remains modest in comparison to that seen in zoonotic H5N1 disease. As human respiratory epithelium is the primary target cells for influenza viruses, elucidating the viral tropism and host innate immune responses of influenza H5N1 virus in human bronchial epithelium may help to understand the pathogenesis. Here we established primary culture of undifferentiated and well differentiated normal human bronchial epithelial (NHBE) cells and infected with highly pathogenic influenza H5N1 virus (A/Vietnam/3046/2004) and a seasonal influenza H1N1 virus (A/Hong Kong/54/1998), the viral replication kinetics and cytokine and chemokine responses were compared by qPCR and ELISA. We found that the in vitro culture of the well differentiated NHBE cells acquired the physiological properties of normal human bronchi tissue which express high level of α2-6-linked sialic acid receptors and human airway trypsin-like (HAT) protease, in contrast to the low expression in the non-differentiated NHBE cells. When compared to H1N1 virus, the H5N1 virus replicated more efficiently and induced a stronger type I interferon response in the undifferentiated NHBE cells. In contrast, in well differentiated cultures, H5N1 virus replication was less efficient and elicited a lower interferon-beta response in comparison with H1N1 virus. Our data suggest that the differentiation of bronchial epithelial cells has a major influence in cells'' permissiveness to human H1N1 and avian H5N1 viruses and the host innate immune responses. The reduced virus replication efficiency partially accounts for the lower interferon-beta responses in influenza H5N1 virus infected well differentiated NHBE cells. Since influenza infection in the bronchial epithelium will lead to tissue damage and associate with the epithelium regeneration, the data generated from the undifferentiated NHBE cultures may also be relevant to disease pathogenesis.     

Genome Wide Host Gene Expression Analysis in Chicken Lungs Infected with Avian Influenza Viruses

The molecular pathogenesis of avian influenza infection varies greatly with individual bird species and virus strain. The molecular pathogenesis of the highly pathogenic avian influenza virus (HPAIV) or the low pathogenic avian influenza virus (LPAIV) infection in avian species remains poorly understood. Thus, global immune response of chickens infected with HPAI H5N1 (A/duck/India/02CA10/2011) and LPAI H9N2 (A/duck/India/249800/2010) viruses was studied using microarray to identify crucial host genetic components responsive to these infection. HPAI H5N1 virus induced excessive expression of type I IFNs (IFNA and IFNG), cytokines (IL1B, IL18, IL22, IL13, and IL12B), chemokines (CCL4, CCL19, CCL10, and CX3CL1) and IFN stimulated genes (OASL, MX1, RSAD2, IFITM5, IFIT5, GBP 1, and EIF2AK) in lung tissues. This dysregulation of host innate immune genes may be the critical determinant of the severity and the outcome of the influenza infection in chickens. In contrast, the expression levels of most of these genes was not induced in the lungs of LPAI H9N2 virus infected chickens. This study indicated the relationship between host immune genes and their roles in pathogenesis of HPAIV infection in chickens.     

Intensive cytokine induction in pandemic H1N1 influenza virus infection accompanied by robust production of IL-10 and IL-6

Background

The innate immune system is the first line of defense against viruses by inducing expression of cytokines and chemokines. Many pandemic influenza H1N1 virus [P(H1N1)] infected severe cases occur in young adults under 18 years old who were rarely seriously affected by seasonal influenza. Results regarding host cytokine profiles of P(H1N1) are ambivalent. In the present study we investigated host cytokine profiles in P(H1N1) patients and identified cytokines related to disease severity.

Methods and Principal Findings

We retrieved 77, 59, 26 and 26 sera samples from P(H1N1) and non-flu influenza like illness (non-ILIs) cases with mild symptoms (mild patients), P(H1N1) vaccinees and healthy individuals, respectively. Nine and 16 sera were from hospitalized P(H1N1) and non-ILIs patients with severe symptoms (severe patients). Cytokines of IL-1, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IFN-γ and TNF-α were assayed by cytokine bead array, IL-17 and IL-23 measured with ELISA. Mild P(H1N1) patients produced significantly elevated IL-2, IL-12, IFN-γ, IL-6, TNF-α, IL-5, IL-10, IL-17 and IL-23 versus to healthy controls. While an overwhelming IL-6 and IL-10 production were observed in severe P(H1N1) patients. Higher IL-10 secretion in P(H1N1) vaccinees confirmed our observation that highly increased level of sera IL-6 and IL-10 in P(H1N1) patients may lead to disease progression.

Conclusion and Significance

A comprehensive innate immune response was activated at the early stage of P(H1N1) infection with a combine Th1/Th2/Th3 cytokines production. As disease progression, a systemic production of IL-6 and IL-10 were observed in severe P(H1N1) patients. Further analysis found a strong correlation between IL-6 and IL-10 production in the severe P(H1N1) patients. IL-6 may be served as a mediator to induce IL-10 production. Highly elevated level of sera IL-6 and IL-10 in P(H1N1) patients may lead to disease progression, but the underlying mechanism awaits further detailed investigations.     

Activation of type I and III interferon signalling pathways occurs in lung epithelial cells infected with low pathogenic avian influenza viruses

The host response to the low pathogenic avian influenza (LPAI) H5N2, H5N3 and H9N2 viruses were examined in A549, MDCK, and CEF cells using a systems-based approach. The H5N2 and H5N3 viruses replicated efficiently in A549 and MDCK cells, while the H9N2 virus replicated least efficiently in these cell types. However, all LPAI viruses exhibited similar and higher replication efficiencies in CEF cells. A comparison of the host responses of these viruses and the H1N1/WSN virus and low passage pH1N1 clinical isolates was performed in A549 cells. The H9N2 and H5N2 virus subtypes exhibited a robust induction of Type I and Type III interferon (IFN) expression, sustained STAT1 activation from between 3 and 6 hpi, which correlated with large increases in IFN-stimulated gene (ISG) expression by 10 hpi. In contrast, cells infected with the pH1N1 or H1N1/WSN virus showed only small increases in Type III IFN signalling, low levels of ISG expression, and down-regulated expression of the IFN type I receptor. JNK activation and increased expression of the pro-apoptotic XAF1 protein was observed in A549 cells infected with all viruses except the H1N1/WSN virus, while MAPK p38 activation was only observed in cells infected with the pH1N1 and the H5 virus subtypes. No IFN expression and low ISG expression levels were generally observed in CEF cells infected with either AIV, while increased IFN and ISG expression was observed in response to the H1N1/WSN infection. These data suggest differences in the replication characteristics and antivirus signalling responses both among the different LPAI viruses, and between these viruses and the H1N1 viruses examined. These virus-specific differences in host cell signalling highlight the importance of examining the host response to avian influenza viruses that have not been extensively adapted to mammalian tissue culture.     

Ocular tropism of influenza A viruses: identification of H7 subtype-specific host responses in human respiratory and ocular cells

Highly pathogenic avian influenza (HPAI) H7 virus infection in humans frequently results in conjunctivitis as a major symptom. However, our understanding of what properties govern virus subtype-specific tropism, and of the host responses responsible for eliciting ocular inflammation and pathogenicity following influenza virus infection, are not well understood. To study virus-host interactions in ocular tissue, we infected primary human corneal and conjunctival epithelial cells with H7, H5, and H1 subtype viruses. We found that numerous virus subtypes were capable of infecting and replicating in multiple human ocular cell types, with the highest titers observed with highly pathogenic H7N7 and H5N1 viruses. Similar patterns of proinflammatory cytokine and chemokine production following influenza virus infection were observed in ocular and respiratory cells. However, primary ocular cells infected with HPAI H7N7 viruses were found to have elevated levels of interleukin-1β (IL-1β), a cytokine previously implicated in ocular disease pathology. Furthermore, H7N7 virus infection of corneal epithelial cells resulted in enhanced and significant increases in the expression of genes related to NF-κB signal transduction compared with that after H5N1 or H1N1 virus infection. The differential induction of cytokines and signaling pathways in human ocular cells following H7 virus infection marks the first association of H7 subtype-specific host responses with ocular tropism and pathogenicity. In particular, heightened expression of genes related to NF-κB-mediated signaling transduction following HPAI H7N7 virus infection in primary corneal epithelial cells, but not respiratory cells, identifies activation of a signaling pathway that correlates with the ocular tropism of influenza viruses within this subtype.     

Pathogenesis and transmission of triple-reassortant swine H1N1 influenza viruses isolated before the 2009 H1N1 pandemic

The 2009 H1N1 pandemic influenza virus represents the greatest incidence of human infection with an influenza virus of swine origin to date. Moreover, triple-reassortant swine (TRS) H1N1 viruses, which share similar host and lineage origins with 2009 H1N1 viruses, have been responsible for sporadic human cases since 2005. Similar to 2009 H1N1 viruses, TRS viruses are capable of causing severe disease in previously healthy individuals and frequently manifest with gastrointestinal symptoms; however, their ability to cause severe disease has not been extensively studied. Here, we evaluated the pathogenicity and transmissibility of two TRS viruses associated with disease in humans in the ferret model. TRS and 2009 H1N1 viruses exhibited comparable viral titers and histopathologies following virus infection and were similarly unable to transmit efficiently via respiratory droplets in the ferret model. Utilizing TRS and 2009 H1N1 viruses, we conducted extensive hematologic and blood serum analyses on infected ferrets to identify lymphohematopoietic parameters associated with mild to severe influenza virus infection. Following H1N1 or H5N1 influenza virus infection, ferrets were found to recapitulate several laboratory abnormalities previously documented with human disease, furthering the utility of the ferret model for the assessment of influenza virus pathogenicity.     

Identification of Restricted Subsets of Mature microRNA Abnormally Expressed in Inactive Colonic Mucosa of Patients with Inflammatory Bowel Disease

Background

Ulcerative Colitis (UC) and Crohn''s Disease (CD) are two chronic Inflammatory Bowel Diseases (IBD) affecting the intestinal mucosa. Current understanding of IBD pathogenesis points out the interplay of genetic events and environmental cues in the dysregulated immune response. We hypothesized that dysregulated microRNA (miRNA) expression may contribute to IBD pathogenesis. miRNAs are small, non-coding RNAs which prevent protein synthesis through translational suppression or mRNAs degradation, and regulate several physiological processes.

Methodology/Findings

Expression of mature miRNAs was studied by Q-PCR in inactive colonic mucosa of patients with UC (8), CD (8) and expressed relative to that observed in healthy controls (10). Only miRNAs with highly altered expression (>5 or <0.2 -fold relative to control) were considered when Q-PCR data were analyzed. Two subsets of 14 (UC) and 23 (CD) miRNAs with highly altered expression (5.2->100 -fold and 0.05–0.19 -fold for over- and under- expression, respectively; 0.001<p≤0.05) were identified in quiescent colonic mucosa, 8 being commonly dysregulated in non-inflamed UC and CD (mir-26a,-29a,-29b,-30c,-126*,-127-3p,-196a,-324-3p). Several miRNA genes with dysregulated expression co-localize with acknowledged IBD-susceptibility loci while others, (eg. clustered on 14q32.31), map on chromosomal regions not previously recognized as IBD-susceptibility loci. In addition, in silico clustering analysis identified 5 miRNAs (mir-26a,-29b,-126*,-127-3p,-324-3p) that share coordinated dysregulation of expression both in quiescent and in inflamed colonic mucosa of IBD patients. Six miRNAs displayed significantly distinct alteration of expression in non-inflamed colonic biopsies of UC and CD patients (mir-196b,-199a-3p,-199b-5p,-320a,-150,-223).

Conclusions/Significance

Our study supports miRNAs as crucial players in the onset and/or relapse of inflammation from quiescent mucosal tissues in IBD patients. It allows speculating a role for miRNAs as contributors to IBD susceptibility and suggests that some of the miRNA with altered expression in the quiescent mucosa of IBD patients may define miRNA signatures for UC and CD and help develop new diagnostic biomarkers.     

Non structural protein of avian influenza A (H11N1) virus is a weaker suppressor of immune responses but capable of inducing apoptosis in host cells

ABSTRACT: BACKGROUND: The Non-Structural (NS1) protein of Influenza A viruses is an extensively studied multifunctional protein which is commonly considered as key viral component to fight against host immune responses. Even though there has been a lot of studies on the involvement of NS1 protein in host immune responses there are still ambiguities regarding its role in apoptosis in infected cells. Interactions of NS1 protein with host factors, role of NS1 protein in regulating cellular responses and apoptosis are quiet complicated and further studies are still needed to understand it completely. RESULTS: NS1 genes of influenza A/Chicken/India/WBNIV2664/2008 (H5N1) and A/Aquatic bird/India/NIV-17095/2007(H11N1) were cloned and expressed in Human embryonic kidney (293T) cells. Microarray based approach to study the host cellular responses to NS1 protein of the two influenza A viruses of different pathogenicity showed significant differences in the host gene expression profile. NS1 protein of H5N1 resulted in suppression of IFN-beta mediated innate immune responses in 293T cells, leading to down-regulation of the components of JAK-STAT pathway like STAT1 which further suppressed the expression of pro-inflammatory cytokines like CXCL10 and CCL5. The degree of suppression of host immune genes was found considerable with NS1 protein of H11N1 but was not as prominent as with H5N1-NS1. TUNEL assay analyses were found to be positive in both the NS1 transfected cells indicating both H5N1 as well as H11N1 NS1 proteins were able to induce apoptosis in transfected cells. CONCLUSIONS: We propose that NS1 protein of both H5N1 and H11N1 subtypes of influenza viruses are capable of influencing host immune responses and possess necessary functionality to support apoptosis in host cells. H11N1, a low pathogenic virus without any proven evidence to infect mammals, contains a highly potential NS1 gene which might contribute to greater virus virulence in different gene combinations.     

The highly pathogenic H5N1 influenza A virus down‐regulated several cellular MicroRNAs which target viral genome

Higher and prolonged viral replication is critical for the increased pathogenesis of the highly pathogenic avian influenza (HPAI) subtype of H5N1 influenza A virus (IAV) over the lowly pathogenic H1N1 IAV strain. Recent studies highlighted the considerable roles of cellular miRNAs in host defence against viral infection. In this report, using a 3′UTR reporter system, we identified several putative miRNA target sites buried in the H5N1 virus genome. We found two miRNAs, miR‐584‐5p and miR‐1249, that matched with the PB2 binding sequence. Moreover, we showed that these miRNAs dramatically down‐regulated PB2 expression, and inhibited replication of H5N1 and H1N1 IAVs in A549 cells. Intriguingly, these miRNAs expression was differently regulated in A549 cells infected with the H5N1 and H1N1 viruses. Furthermore, transfection of miR‐1249 inhibitor enhanced the PB2 expression and promoted the replication of H5N1 and H1N1 IAVs. These results suggest that H5N1 virus may have evolved a mechanism to escape host‐mediated inhibition of viral replication through down‐regulation of cellular miRNAs, which target its viral genome.