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Hemagglutinin of influenza A virus binds specifically to cell surface nucleolin and plays a role in virus internalization.
Abstract The hemagglutinin (HA) protein of influenza A virus initiates cell entry by binding to sialic acids on target cells. In the current study, we demonstrated that in addition to sialic acids, influenza A/Puerto Rico/8/34 H1N1 (PR8) virus HA specifically binds to cell surface nucleolin (NCL). The interaction between HA and NCL was initially revealed with virus overlay protein binding assay (VOPBA) and subsequently verified with co-immunoprecipitation. Importantly, inhibiting cell surface NCL with NCL antibody, blocking PR8 viruses with purified NCL protein, or depleting endogenous NCL with siRNA all substanti...
Source: Virology - April 12, 2016 Category: Virology Authors: Chan CM, Chu H, Zhang AJ, Leung LH, Sze KH, Kao RY, Chik KK, To KK, Chan JF, Chen H, Jin DY, Liu L, Yuen KY Tags: Virology Source Type: research

Caveolin- and clathrin-independent entry of BKPyV into primary human proximal tubule epithelial cells.
Abstract BK polyomavirus (BKPyV) is a human pathogen that causes polyomavirus-associated nephropathy and hemorrhagic cystitis in transplant patients. Gangliosides and caveolin proteins have previously been reported to be required for BKPyV infection in animal cell models. Recent studies from our lab and others, however, have indicated that the identity of the cells used for infection studies can greatly influence the behavior of the virus. We therefore wished to re-examine BKPyV entry in a physiologically relevant primary cell culture model, human renal proximal tubule epithelial cells. Using siRNA knockdowns, we ...
Source: Virology - February 19, 2016 Category: Virology Authors: Zhao L, Marciano AT, Rivet CR, Imperiale MJ Tags: Virology Source Type: research

Phosphorylation of NS5A Serine-235 is essential to hepatitis C virus RNA replication and normal replication compartment formation.
Abstract Hepatitis C virus (HCV) NS5A protein is essential for HCV RNA replication and virus assembly. Here we report the identification of NS5A phosphorylation sites Ser-222, Ser-235 and Thr-348 during an infectious HCV replication cycle and demonstrate that Ser-235 phosphorylation is essential for HCV RNA replication. Confocal microscopy revealed that both phosphoablatant (S235A) and phosphomimetic (S235D) mutants redistribute NS5A to large juxta-nuclear foci that display altered colocalization with known replication complex components. Using electron microscopy (EM) we found that S235D alters virus-induced memb...
Source: Virology - February 10, 2016 Category: Virology Authors: Eyre NS, Hampton-Smith RJ, Aloia AL, Eddes JS, Simpson KJ, Hoffmann P, Beard MR Tags: Virology Source Type: research

Epstein-Barr virus glycoprotein gM can interact with the cellular protein p32 and knockdown of p32 impairs virus.
We report here that the long predicted cytoplasmic tail of gM is not required for complex formation and that it interacts with the cellular protein p32, which has been reported to be involved in nuclear egress of human cytomegalovirus and herpes simplex virus. Although redistribution of p32 and colocalization with gM was not observed in virus infected cells, knockdown of p32 expression by siRNA or lentivirus-delivered shRNA recapitulated the phenotype of a virus lacking expression of gNgM. A proportion of virus released from cells sedimented with characteristics of virus lacking an intact envelope and there was an increase...
Source: Virology - January 13, 2016 Category: Virology Authors: Changotra H, Turk SM, Artigues A, Thakur N, Gore M, Muggeridge MI, Hutt-Fletcher LM Tags: Virology Source Type: research

DC-SIGN as an attachment factor mediates Japanese encephalitis virus infection of human dendritic cells via interaction with a single high-mannose residue of viral E glycoprotein.
Abstract The skin-resident dendritic cells (DCs) are thought to be the first defender to encounter incoming viruses and likely play a role in Japanese encephalitis virus (JEV) early infection. In the current study, following the demonstration of JEV productive infection in DCs, we revealed that the interaction between JEV envelope glycoprotein (E glycoprotein) and DC-SIGN was important for such infection as evidenced by antibody neutralization and siRNA knockdown experiments. Moreover, the high-mannose N-linked glycan at N154 of E glycoprotein was shown to be crucial for JEV binding to DC-SIGN and subsequent inter...
Source: Virology - November 26, 2015 Category: Virology Authors: Wang P, Hu K, Luo S, Zhang M, Deng X, Li C, Jin W, Hu B, He S, Li M, Du T, Xiao G, Zhang B, Liu Y, Hu Q Tags: Virology Source Type: research

ICAM-1 regulates the survival of influenza virus in lung epithelial cells during the early stages of infection.
Abstract Intercellular cell adhesion molecule-1 (ICAM-1) is an inducible cell surface glycoprotein that is expressed on many cell types. Influenza virus infection enhanced ICAM-1 expression and messenger RNA levels. Human bronchial epithelial cells (HBEpC) and nasal epithelial cells, on exposure to different strains of influenza virus (H1N1, H3N2, and H9N1) showed significant increase in ICAM-1 gene expression (p<0.001) along with the ICAM-1 protein levels (surface and secreted). Depleting ICAM-1 in HBEpC with ICAM-1 siRNA and subsequently infecting with H1N1 showed increased viral copy numbers. Influenza virus...
Source: Virology - October 22, 2015 Category: Virology Authors: Othumpangat S, Noti JD, McMillen CM, Beezhold DH Tags: Virology Source Type: research

Mungbean yellow mosaic Indian virus encoded AC2 protein suppresses RNA silencing by inhibiting Arabidopsis RDR6 and AGO1 activities.
Abstract RNA silencing refers to a conserved RNA-directed gene regulatory mechanism in a wide range of eukaryotes. It plays an important role in many processes including growth, development, genome stability, and antiviral defense in the plants. Geminivirus encoded AC2 is identified as an RNA silencing suppressor protein, however, the mechanism of action has not been characterized. In this paper, we elucidate another mechanism of AC2-mediated suppression activity of Mungbean Yellow Mosaic India Virus (MYMIV). The AC2 protein, unlike many other suppressors, does not bind to siRNA or dsRNA species and its suppressio...
Source: Virology - September 30, 2015 Category: Virology Authors: Kumar V, Mishra SK, Rahman J, Taneja J, Sundaresan G, Mishra NS, Mukherjee SK Tags: Virology Source Type: research

Flavivirus sfRNA suppresses antiviral RNA interference in cultured cells and mosquitoes and directly interacts with the RNAi machinery.
In this study, we demonstrate that two flaviviruses, Dengue virus and Kunjin virus, significantly repress siRNA-mediated RNAi in infected human cells as well as during infection of the mosquito vector Culex quinquefasciatus. Arthropod-borne flaviviruses generate a small structured non-coding RNA from the viral 3' UTR referred to as sfRNA. Analysis of infections with a mutant Kunjin virus that is unable to generate appreciable amounts of the major sfRNA species indicated that RNAi suppression was associated with the generation of the non-coding sfRNA. Co-immunoprecipitation of sfRNA with RNAi mediators Dicer and Ago2 sugges...
Source: Virology - August 28, 2015 Category: Virology Authors: Moon SL, Dodd BJ, Brackney DE, Wilusz CJ, Ebel GD, Wilusz J Tags: Virology Source Type: research

Ceramide formation mediated by acid sphingomyelinase facilitates endosomal escape of caliciviruses.
We report a novel finding that bile acids can be substituted by cold treatment for endosomal escape and virus replication. This endosomal escape by cold treatment or bile acids is associated with ceramide formation by acid sphingomyelinase (ASM). ASM catalyzes hydrolysis of sphingomyelin into ceramide, which is known to destabilize lipid bilayer. Treatment of LLC-PK cells with bile acids or cold led to ceramide formation, and small molecule antagonists or siRNA of ASM blocked ceramide formation in the endosomes and significantly reduced PEC replication. Inhibition of ASM resulted in the retention of PEC, feline calicivirus...
Source: Virology - May 14, 2015 Category: Virology Authors: Shivanna V, Kim Y, Chang KO Tags: Virology Source Type: research

RIG-I and TLR3 are both required for maximum interferon induction by influenza virus in human lung alveolar epithelial cells.
Abstract Pattern recognition receptors, such as retinoic acid-inducible protein I (RIG-I), Toll-like receptors 3 and 7 (TLR3 and 7), and nucleotide-binding oligomerization domain containing protein 2 (NOD2), play important roles in the recognition of influenza A virus (IAV), but their role in interferon (IFN) induction is still unclear, particularly in human lung. We investigated IFN induction by IAV in the A549 cell line as well as in primary human alveolar epithelial cells (AEC). TLR3/7, NOD2, RIG-I, and IFN expression levels were measured by qRT-PCR and ELISA in cells infected with IAV PR8. We found that TLR7 a...
Source: Virology - April 10, 2015 Category: Virology Authors: Wu W, Zhang W, Duggan ES, Booth JL, Zou MH, Metcalf JP Tags: Virology Source Type: research

Galectin-3 plays a role in minute virus of mice infection.
Abstract Galectin-3 has previously been found to be required by the parvovirus minute virus of mice prototype strain (MVMp) for infection of mouse fibroblast cells. Since MVMp is an oncotropic virus, and galectin-3 is a multifunctional protein implicated in cancer metastasis, we hypothesized that galectin-3 and Mgat5, the Golgi enzyme that synthesizes high-affinity glycan ligands of galectin-3, might play a role in MVMp infection. Using siRNA-mediated knockdown of galectin-3 in mouse cells transformed with polyomavirus middle T antigen and Mgat5(-/-) mouse mammary tumor cells, we found that galectin-3 and Mgat5 ar...
Source: Virology - March 10, 2015 Category: Virology Authors: Garcin PO, Nabi IR, Panté N Tags: Virology Source Type: research

Porcine aminopeptidase N mediated polarized infection by porcine epidemic diarrhea virus in target cells.
Abstract Infection of polarized intestinal epithelial cells by porcine epidemic diarrhea virus (PEDV) was characterized. Indirect immunofluorescence assay, real-time PCR, and transmission electron microscopy confirmed PEDV can be successfully propagated in immortalized swine small intestine epithelial cells (IECs). Infection involved porcine aminpeptidase N (pAPN), a reported cellular receptor for PEDV, transient expression of pAPN and siRNA targeted pAPN increased and decreased the infectivity of PEDV in IECs, respectively. Subsequently, polarized entry into and release from both Vero E6 and IECs was analyzed. PE...
Source: Virology - February 11, 2015 Category: Virology Authors: Cong Y, Li X, Bai Y, Lv X, Herrler G, Enjuanes L, Zhou X, Qu B, Meng F, Cong C, Ren X, Li G Tags: Virology Source Type: research

Cytorhabdovirus phosphoprotein shows RNA silencing suppressor activity in plants, but not in insect cells.
Abstract RNA silencing in plants and insects provides an antiviral defense and as a countermeasure most viruses encode RNA silencing suppressors (RSS). For the family Rhabdoviridae, no detailed functional RSS studies have been reported in plant hosts and insect vectors. In agroinfiltrated Nicotiana benthamiana leaves we show for the first time for a cytorhabdovirus, lettuce necrotic yellows virus (LNYV), that one of the nucleocapsid core proteins, phosphoprotein (P) has relatively weak local RSS activity and delays systemic silencing of a GFP reporter. Analysis of GFP small RNAs indicated that the P protein did no...
Source: Virology - January 12, 2015 Category: Virology Authors: Mann KS, Johnson KN, Dietzgen RG Tags: Virology Source Type: research

Pathogenesis of Soybean mosaic virus in soybean carrying Rsv1 gene is associated with miRNA and siRNA pathways, and breakdown of AGO1 homeostasis.
Abstract Profiling small RNAs in soybean Williams 82 (rsv), susceptible to Soybean mosaic virus (SMV, the genus Potyvirus, family Potyviridae) strains G2 and G7, and soybean PI96983 (Rsv1), resistant to G2 but susceptible to G7, identified the microRNA miR168 that was highly overexpressed only in G7-infected PI96983 showing a lethal systemic hypersensitive response (LSHR). Overexpression of miR168 was in parallel with the high-level expression of AGO1 mRNA, high-level accumulation of miR168-mediated AGO1 mRNA cleavage products but with severely repressed AGO1 protein. In contrast, AGO1 mRNA, degradation products a...
Source: Virology - January 12, 2015 Category: Virology Authors: Chen H, Zhang L, Yu K, Wang A Tags: Virology Source Type: research

Tetherin restricts HSV-2 release and is counteracted by multiple viral glycoproteins.
Abstract Tetherin has been defined as a restriction factor of HIV-1 and several other enveloped viruses. However, the significance of tetherin in viral infection remains to be further addressed. Here, we investigated whether tetherin plays a role in HSV-2 infection. Our study revealed that overexpression of tetherin restricted the release of HSV-2 into the extracellular medium, while knockdown of tetherin by siRNA enhanced its release. We further demonstrated that HSV-2 infection and viral glycoproteins gB, gD, gH and gL but not gM significantly downregulated the endogenous expression of tetherin. Additional study...
Source: Virology - November 26, 2014 Category: Virology Authors: Liu Y, Luo S, He S, Zhang M, Wang P, Li C, Huang W, Hu B, Griffin GE, Shattock RJ, Hu Q Tags: Virology Source Type: research

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