Antiviral Effects Of Type Research Articles

Antiviral Response Induced by Toll-Like Receptor (TLR) 7/TLR8 Activation Inhibits Human Immunodeficiency Virus Type 1 Infection in Cord Blood Macrophages.

Vertical transmission is the main mechanism of human immunodeficiency virus type 1 (HIV-1) infection in infants, who may develop high viremia and rapidly progress to AIDS. Innate immunity agonists can control HIV-1 replication in vitro, but the protective effect in the neonatal period remains unknown. Herein, we evaluated the immunomodulatory and antiviral effects of type I interferon (IFN-I) adjuvants on cord blood monocyte-derived macrophages upon HIV-1 infection. Despite the phenotypic and transcriptional similarities between cord blood and adult macrophages, cord blood cells were prone to viral replication when infected with HIV-1. However, treatment with CL097 efficiently promoted the antiviral and inflammatory responses and inhibited HIV-1 replication in cord blood cells in an NF-κB and autophagy activation-independent manner. Our data suggest that cord blood macrophages are able to establish antiviral responses induced by IFN-I adjuvants similar to those of their adult counterparts, revealing a potential adjuvant candidate to enhance the neonatal immune response.

Goose Mx and OASL Play Vital Roles in the Antiviral Effects of Type I, II, and III Interferon against Newly Emerging Avian Flavivirus.

Duck Tembusu virus (TMUV), an emerging avian flavivirus, is highly pathogenic to birds and has the potential to become a zoonotic pathogen. Here, the molecular antiviral mechanism of goose type I, II, and III interferon (goIFNα, goIFNγ, and goIFNλ), the key components of the innate immune pathway, against TMUV was studied. We found that the transcription of goIFNs was obviously driven by TMUV infection in vivo and in vitro, and the titers and copies of TMUV were significantly reduced following treatment with goIFNs. The results of RNA sequencing (RNA-seq) revealed that goIFN stimulation triggered a set of differentially expressed genes at different levels and a positive regulatory feedback loop of IFN release against infection. Two important interferon-stimulated genes, goMx and goOASL, were identified as workhorse IFNs in the inhibition of TMUV replication. The antiviral effects of goMx and goOASL were confirmed by transient overexpression and knockdown assay in vitro. Overall, our findings defined that goose Mx and OASL play key roles in the antiviral effects of type I, II, and III interferon against the TMUV. These results extend our understanding of the transcriptional profile of the goose IFN-mediated signaling pathway and provide insight into the antiviral mechanism of goIFNs against flavivirus infection.

TREX1 Knockdown Induces an Interferon Response to HIV that Delays Viral Infection in Humanized Mice.

Despite their antiviral effect, the invivo effect of interferons on HIV transmission is difficult to predict, because interferons also activate and recruit HIV-susceptible cells to sites of infection. HIV does not normally induce type I interferons in infected cells, but does if TREX1 is knocked down. Here, we investigated the effect of topical TREX1 knockdown and local interferon production on HIV transmission in human cervicovaginal explants and humanized mice. Inexplants in which TREX1 was knocked down, HIV induced interferons, which blocked infection. In humanized mice, even though TREX1 knockdown increased infiltrating immune cells, it delayed viral replication for 3-4weeks. Similarly intravaginal application of type I interferons the day before HIV infection induced interferon responsive genes, reduced inflammation, and decreased viral replication. However, intravenous interferon enhanced inflammation and infection. Thus, in models of human sexual transmission, a localized interferon response inhibits HIV transmission but systemic interferons do not.

Characterisation and bioactivities of type I interferon subtype E and F in salmonids

Salmonids are important commercial species in the European aquaculture industry. Many viral diseases can impact on the industry, leading to economic losses. Interferons (IFNs) are cytokines involved in antiviral defence, and study of their regulation and function may shed light on how fish can defend themselves against viral infection. Fish type I IFNs are classified into two groups based on cysteine residues in the mature peptide, namely group I and II IFNs, each of which is further divided into 3 subtypes in salmonids. The latest new subtypes, IFN-e and IFN-f, have only recently been identified and their biological activities have still to be characterised. In this presentation, IFN-e and –f genes in Atlantic salmon (Salmo salar) and their bioactivities were reviewed and compared to previous studies of other type I IFN subtypes (a-d). The type I IFN subtypes showed different expression patterns between the 2 groups in cell lines and primary head kidney cells stimulated with poly I:C and in heart and head kidney of cardiomyopathy syndrome (CMS) infected salmon. Transcript levels could be correlated to the antiviral response and the IFN-e and IFN–f recombinant proteins were shown to induce Mx gene expression which is known to mediate antiviral activity. This data together with the reactivity of specific antibodies to the subtypes provides a better understanding of the antiviral effects of type I IFNs in salmonids.

Role of type I interferon receptor signaling on NK cell development and functions.

Type I interferons (IFN) are unique cytokines transcribed from intronless genes. They have been extensively studied because of their anti-viral functions. The anti-viral effects of type I IFN are mediated in part by natural killer (NK) cells. However, the exact contribution of type I IFN on NK cell development, maturation and activation has been somewhat difficult to assess. In this study, we used a variety of approaches to define the consequences of the lack of type I interferon receptor (IFNAR) signaling on NK cells. Using IFNAR deficient mice, we found that type I IFN affect NK cell development at the pre-pro NK stage. We also found that systemic absence of IFNAR signaling impacts NK cell maturation with a significant increase in the CD27+CD11b+ double positive (DP) compartment in all organs. However, there is tissue specificity, and only in liver and bone marrow is the maturation defect strictly dependent on cell intrinsic IFNAR signaling. Finally, using adoptive transfer and mixed bone marrow approaches, we also show that cell intrinsic IFNAR signaling is not required for NK cell IFN-γ production in the context of MCMV infection. Taken together, our studies provide novel insights on how type I IFN receptor signaling regulates NK cell development and functions.

Limited Hepatitis B Virus Replication Space in the Chronically Hepatitis C Virus-Infected Liver

We compared the kinetics and magnitude of hepatitis B virus (HBV) infection in hepatitis C virus (HCV)-naive and chronically HCV-infected chimpanzees in whose livers type I interferon-stimulated gene (ISG) expression is strongly induced. HBV infection was delayed and attenuated in the HCV-infected animals, and the number of HBV-infected hepatocytes was drastically reduced. These results suggest that establishment of HBV infection and its replication space is limited by the antiviral effects of type I interferon in the chronically HCV-infected liver.

The Repression Domain of the E1B 55-Kilodalton Protein Participates in Countering Interferon-Induced Inhibition of Adenovirus Replication

To begin to investigate the mechanism by which the human adenovirus type 5 E1B 55-kDa protein protects against the antiviral effects of type 1 interferon (IFN) (J. S. Chahal, J. Qi, and S. J. Flint, PLoS Pathog. 8:e1002853, 2012 [doi:10.1371/journal.ppat.1002853]), we examined the effects of precise amino acid substitution in this protein on resistance of viral replication to the cytokine. Only substitution of residues 443 to 448 of E1B for alanine (E1B Sub19) specifically impaired production of progeny virus and resulted in a large defect in viral DNA synthesis in IFN-treated normal human fibroblasts. Untreated or IFN-treated cells infected by this mutant virus (AdEasyE1Sub19) contained much higher steady-state concentrations of IFN-inducible GBP1 and IFIT2 mRNAs than did wild-type-infected cells and of the corresponding newly transcribed pre-mRNAs, isolated exploiting 5'-ethynyluridine labeling and click chemistry. These results indicated that the mutations created by substitution of residues 443 to 448 for alanine (Sub19) impair repression of transcription of IFN-inducible genes, by the E1B, 55-kDa protein, consistent with their location in a segment required for repression of p53-dependent transcription. However, when synthesized alone, the E1B 55-kDa protein inhibited expression of the p53-regulated genes BAX and MDM2 but had no impact whatsoever on induction of IFIT2 and GBP1 expression by IFN. These observations correlate repression of transcription of IFN-inducible genes by the E1B 55-kDa protein with protection against inhibition of viral genome replication and indicate that the E1B 55-kDa protein is not sufficient to establish such transcriptional repression.

P127 Triptolide inhibits virus-induced interferon antiviral response and enhances vesicular stomatitis virus oncolysis

Introduction Rapid induction of type I interferon (IFN) expression is a central event in establishing the innate antiviral response. It requires pathogen-inducible activation of transcription factors that function in a synergistic fashion to induce gene expression. Vesicular stomatitis virus (VSV) is highly sensitive to the antiviral effects of type I IFN, as well as other innate immune effectors that strongly inhibit VSV in non-malignant cells and tissues; malignant cells acquire diminished responsiveness to IFN action and are specifically infected and killed by VSV. However, some cancer types, including androgen-independent prostate cancer, appear to be resistant to VSV-induced oncolysis. To overcome this resistance, experimental strategies are now combining oncolytic viruses with different cytotoxic compounds to enhance tumor cell killing. Triptolide (TPL) is a key biologically active component purified from the Chinese herb Tripterygium wilfordii Hook F . This small molecule mediates a variety of biological activities including immune suppression and anti-inflammatory effects. Interestingly, TPL has been well characterized as a proapoptotic and antiproliferative agent in vitro and in vivo . TPL and its derivatives have entered human clinical trials for several diseases, including cancer. In the present study, we investigate the role of TPL in relation to VSV oncolysis in the human prostate cancer cell line PC-3. Methods PC-3 prostate cancer cells were pretreated with TPL then infected with VSV. The induction of various ISGs expression following VSV infection was monitored by qPCR and Western blot. VSV-induced apoptosis and viral replication were assessed by flow cytometry and plaque assay, respectively. For in vivo studies, PC-3 cells were injected subcutaneously in athymic nude mice and VSV-infected mice received intraperitoneal injection of TPL or control vehicle. Tumor size was measured using a caliper, and tumor volume was calculated as length X width 2 /2. Results We demonstrate that TPL potently inhibits induction of the type I IFN innate antiviral response. Additionally, we also observe that TPL increases VSV replication in PC-3 cells in a dose-dependent manner. Furthermore, we tested the effect of known RNA polymerase II inhibitors (flavopiridol and α-amanitin) in combination with VSV and observed a similar effect on interferon-stimulated gene (ISG) expression and viral replication as with TPL. Thus, as previously reported, TPL inhibition of ISG induction appears to be mediated via the inhibition of RNA polymerase II activity. TPL enhanced VSV-induced apoptosis in a dose- and time-dependent manner in PC3, as measured by PI/annexin V staining. All together, these results indicate that TPL enhances VSV replication and induces cell death following VSV infection by inhibiting the induction of IFN signaling. In vivo, using a PC-3 xenograft model in athymic male nude mice, TPL inhibited tumor growth, indicating that TPL is a promising candidate to enhance VSV oncolytic activity in vivo . Conclusion This study reveals for the first time the role of TPL in the regulation of IFN antiviral activity and enhancement of VSV-induced apoptosis.

Mx is dispensable for interferon-mediated resistance of chicken cells against influenza A virus.

The type I interferon (IFN) system plays an important role in antiviral defense against influenza A viruses (FLUAV), which are natural chicken pathogens. Studies of mice identified the Mx1 protein as a key effector molecule of the IFN-induced antiviral state against FLUAV. Chicken Mx genes are highly polymorphic, and recent studies suggested that an Asn/Ser polymorphism at amino acid position 631 determines the antiviral activity of the chicken Mx protein. By employing chicken embryo fibroblasts with defined Mx-631 polymorphisms and retroviral vectors for the expression of Mx isoforms in chicken cells and embryonated eggs, we show here that neither the 631Asn nor the 631Ser variant of chicken Mx was able to confer antiviral protection against several lowly and highly pathogenic FLUAV strains. Using a short interfering RNA (siRNA)-mediated knockdown approach, we noted that the antiviral effect of type I IFN in chicken cells was not dependent on Mx, suggesting that some other IFN-induced factors must contribute to the inhibition of FLUAV in chicken cells. Finally, we found that both isoforms of chicken Mx protein appear to lack GTPase activity, which might explain the observed lack of antiviral activity.

370 Cigarette smoke products suppress anti-viral effects of Type I interferon via phosphorylation-dependent down-regulation of its receptor

370 Cigarette smoke products suppress anti-viral effects of Type I interferon via phosphorylation-dependent down-regulation of its receptor

Interferon-Inducible Stat2 Activation of JUND and CLDN4: Mediators of IFN Responses

Signal transducer and activator of transcription 2 (Stat2) is a critical signaling protein involved in mediating interferon-alpha/beta (IFN-alpha/beta) responses. Using site-directed mutagenesis in conjunction with gene microarray and biologic studies, we have previously demonstrated that in addition to Stat2 functioning as a transactivator of transcription of a subset of IFN-inducible genes (ISG), Stat2-DNA binding mediates the transcriptional activation of other ISGs required for IFN-inducible antiviral and growth inhibitory responses. Among these, two candidate genes identified were Jun-D (JUND) and claudin-4 (CLDN4). To further explore the role of JUND and CLDN4 in IFN responses, we conducted knockdown studies using siRNA specific for either JUND or CLDN4 in 2fTGH fibroblast cells, and consistent with cells expressing the DNA-binding mutant of Stat2 (U6A-2VV-II), siRNA-mediated knockdown resulted in cells that exhibited reduced antiproliferative and antiviral responses to IFN. Our data suggest that JUND and CLDN4 are critical mediators of the antiproliferative and antiviral effects of type I IFNs and further confirm the functional importance of the DNA-binding domain of Stat2.

Viruses Evade the Immune System through Type I Interferon-Mediated STAT2-Dependent, but STAT1-Independent, Signaling

Understanding, treating, and preventing diseases caused by immunosuppression and/or persistent infections remain both a major challenge in biomedical research and an important health goal. For a virus or any infectious agent to persist, it must utilize strategies to suppress or evade the host's immune response. Here, we report that two dissimilar viruses employ a common maneuver to cause a profound immunosuppression. Measles virus (MV) and lymphocytic choriomeningitis virus (LCMV) interfere with dendritic cell (DC) development and expansion in vivo and in vitro. The underlying mechanism for this is through the generation of type I interferon (IFN) that acts via a signal transducer and activator of a transcription (STAT)2-dependent, but STAT1-independent, pathway. Thus, viruses subvert the known antiviral effect of type I IFN through STAT2-specific signaling to benefit their survival. These observations have implications for understanding and developing therapies to treat diseases caused by immunosuppression and/or persistent infections.

Interferon-resistant Human Melanoma Cells Are Deficient in ISGF3 Components, STAT1, STAT2, and p48-ISGF3γ

The mechanism of IFN resistance was examined in three long-term cell lines, SK-MEL-28, SK-MEL-3, and MM96, exhibiting significant variation in responsiveness to the antiproliferative and antiviral effects of type I IFNs. The JAK-STAT components involved in IFN signal transduction were analyzed in detail. After exposure to IFN, activation of the IFN type I receptor-linked tyrosine kinases, JAK-1 and TYK-2, was detected at similar levels in both IFN-sensitive and IFN-resistant cell types, indicating that IFN resistance did not result from a deficiency in signaling at the level of receptor-associated kinase activation. However, analysis of ISGF3 transcription factor components, STAT1, STAT2, and p48-ISGF3gamma, revealed that their expression and activation correlated with cellular IFN responsiveness. The analysis was extended to also include IFN-sensitive primary melanocytes, three additional IFN-resistant melanoma cell lines, and seven cell cultures recently established from melanoma patient biopsies. It was consistently observed that the most marked difference in ISGF3 was a lack of STAT1 in the resistant versus the sensitive cells. Transfection of the IFN-resistant MM96 cell line to express increased levels of STAT1 protein partially restored IFN responsiveness in an antiviral assay. We conclude that a defect in the level of STAT1 and possibly all three ISGF3 components in IFN-resistant human melanoma cells may be a general phenomenon responsible for reduced cellular responsiveness of melanomas to IFNs.