Yifan Huang

Roles of Rho GTPases in Intracellular Transport and Cellular Transformation

Rho family GTPases belong to the Ras GTPase superfamily and transduce intracellular signals known to regulate a variety of cellular processes, including cell polarity, morphogenesis, migration, apoptosis, vesicle trafficking, viral transport and cellular transformation. The three best-characterized Rho family members are Cdc42, RhoA and Rac1. Cdc42 regulates endocytosis, the transport between the endoplasmic reticulum and Golgi apparatus, post-Golgi transport and exocytosis. Cdc42 influences trafficking through interaction with Wiskott-Aldrich syndrome protein (N-WASP) and the Arp2/3 complex, leading to changes in actin dynamics. Rac1 mediates endocytic and exocytic vesicle trafficking by interaction with its effectors, PI3kinase, synaptojanin 2, IQGAP1 and phospholipase D1. RhoA participates in the regulation of endocytosis through controlling its downstream target, Rho kinase. Interestingly, these GTPases play important roles at different stages of viral protein and genome transport in infected host cells. Importantly, dysregulation of Cdc42, Rac1 and RhoA leads to numerous disorders, including malignant transformation. In some cases, hyperactivation of Rho GTPases is required for cellular transformation. In this article, we review a number of findings related to Rho GTPase function in intracellular transport and cellular transformation.

Complete genome sequence analysis of goatpox virus isolated from China shows high variation.

Goatpox virus (GTPV), a member of the Capripoxvirus genus of the Poxviridae family, is the causative agent of variolo caprina (goatpox). GTPV can cause significant economic losses of domestic ruminants in endemic regions and can threaten breeding stocks. In this study, we report on the compilation of the complete genomic sequence of an isolated GTPV field strain FZ (GTPV_FZ). The 150,194bp GTPV genome consists of a central coding region bounded by two identical 2301bp inverted terminal repeats and contains 151 putative genes. Comparative genomic analysis reveals the apparent genetic relationships among Capripoxviruses are close, but sufficient genomic variants in the field isolate strain FZ have been identified to distinguish it from other GTPV strains and other Capripoxvirus species. Phylogenetic analysis based on the p32 and complete GTPV genome can be used to differentiate SPPVs, GTPVs and LSDVs. These data may contribute to the epidemiological study of the Chinese capripoxvirus and help to develop more specific detection methods to distinguish GTPVs, SPPVs and LSDVs.

Muscovy duck reovirus infection rapidly activates host innate immune signaling and induces an effective antiviral immune response involving critical interferons

Muscovy duck reovirus (MDRV) is a highly pathogenic virus in waterfowl and causes significant economic loss in the poultry industry worldwide. Because the host innate immunity plays a key role in defending against virus invasion, more and more attentions have been paid to the immune response triggered by viral infection. Here we found that the genomic RNA of MDRV was able to rapidly induce the production of interferons (IFNs) in host. Mechanistically, MDRV infection induced robust expression of IFNs in host mainly through RIG-I, MDA5 and TLR3-dependent signaling pathways. In addition, we observed that silencing VISA expression in 293T cells could significantly inhibit the secretion of IFNs. Remarkably, the production of IFNs was reduced by inhibiting the activation of NF-κB or knocking down the expression of IRF-7. Furthermore, our study showed that treatment of 293T cells and Muscovy duck embryo fibroblasts with IFNs markedly impaired MDRV replication, suggesting that these IFNs play an important role in antiviral response during the MDRV infection. Importantly, we also detected the induced expression of RIG-I, MDA5, TLR3 and type I IFN in Muscovy ducks infected with MDRV at different time points post infection. The results from in vivo studies were consistent with those in 293T cells infected with MDRV. Taken together, our findings reveal that the host can resist MDRV invasion by activating innate immune response involving RIG-I, MDA5 and TLR3-dependent signaling pathways that govern IFN production.

Genome analysis of orf virus isolates from goats in the Fujian Province of southern China

Orf virus (ORFV), a species of the genus Parapoxvirus of the family Poxviridae, causes non-systemic, highly contagious, and eruptive disease in sheep, goat, and other wild and domestic ruminants. Our previous work shows orf to be ubiquitous in the Fujian Province of China, a region where there is considerable heterogeneity among ORFVs. In this study, we sequenced full genomes of four Fujian goat ORFV strains (OV-GO, OV-YX, OV-NP, and OV-SJ1). The four strains were 132–139 kb in length, with each containing 124–132 genes and about 64% G+C content. The most notable differences between the four strains were found near the genome termini. OV-NP lacked seven and OV-SJ1 lacked three genes near the right terminus when compared against other ORFVs. We also investigated the skin-virulence of the four Fujian ORFVs in goats. The ORFVs with gene deletions showed low virulence while the ORFVs without gene deletions showed high virulence in goats suggesting gene deletion possibly leads to attenuation of ORFVs. Gene 134 was disrupted in OV-NP genome due to the lack of initial code. The phylogenetic tree based on complete Parapoxviruse genomes showed that sheep originated and goat originated ORFVs formed distinctly separate branches with 100% bootstrap. Based on the single gene phylogenetic tree of 132 genes of ORFVs, 47 genes can be easily distinguished as having originated from sheep or goats. In order to further reveal genetic variation presented in goat ORFVs and sheep ORFVs, we analyzed the deduced amino acid sequences of gene 008, multiple alignment of amino acid sequences of gene 008 from the genome of five goat ORFVs and four sheep ORFVs revealed 33 unique amino acids differentiating it as having sheep or goats as host. The availability of genomic sequences of four Fujian goat ORFVs aids in our understanding of the diversity of orf virus isolates in this region and can assist in distinguishing between orf strains that originate in sheep and goats.

Isolation and Identification of Duck Tembusu Virus Strain LH and Development of Latex-Agglutination Diagnostic Method for Rapid Detection of Antibodies

SUMMARY An outbreak of egg-drop syndrome occurred on a Sheldrake duck farm in Longhai in Fujian Province, China, in 2012. The main clinical symptoms were sharply reduced egg production, crooked necks, and death. We isolated the virus from the sick ducks, identified it, and observed the histopathologic changes after viral infection. We detected viral RNA in the blood and feces of the infected ducks and developed a latex-agglutination diagnostic method to detect anti–Tembusu-virus antibodies. Our results show that the pathogenic virus is a Tembusu virus. The histopathologic changes included follicular cell degeneration and necrosis, follicular cavity filled with blood cells, massive necrosis in the brain, and degeneration and necrosis of the nerve and glial cells. When the transmission of the virus in the infected ducks was studied, the duck blood was positive for viral nucleic acid for up to 29 days, and the feces were positive for viral nucleic acid for up to 13 days. We successfully established a simple, rapid, and easy-to-use latex-agglutination diagnostic method for the detection of antibodies against duck Tembusu virus. RESUMEN Aislamiento e identificación de la cepa LH del virus Tembusu de los patos y el desarrollo de un método diagnóstico de aglutinación con látex para la detección rápida de anticuerpos. Se produjo un brote con un síndrome de baja de la postura en una granja de patos tarro blancos en Longhai, provincia de Fujian, en China, en el año 2012. Los principales síntomas clínicos fueron una reducción drástica de la producción de huevos, cuellos torcidos, y muerte. Se aisló el virus de los patos enfermos, se identificó y se observaron cambios histopatológicos después de la infección viral. Se detectó el ARN viral en la sangre y en las heces de los patos infectados y se desarrolló un método de diagnóstico mediante aglutinación de látex para detectar anticuerpos contra el virus Tembusu. Los resultados muestran que el virus patógeno es el virus Tembusu. Los cambios histopatológicos incluyeron degeneración y necrosis celular folicular, la cavidad folicular estaba llena de células sanguíneas, necrosis masiva en el cerebro y degeneración y necrosis de nervios y células gliales. Cuando se estudió la transmisión del virus en los patos infectados, la sangre de pato fue positiva para la presencia el ácido nucleico viral por un máximo de 29 días, y las heces fueron positivas para la presencia del ácido nucleico viral por un máximo de 13 días. Se estableció con éxito un método de diagnóstico simple, rápido y fácil de usar mediante aglutinación con látex para la detección de anticuerpos contra el virus de Tembusu de los patos.

A novel avian retrovirus associated with lymphocytoma isolated from a local Chinese flock induced significantly reduced growth and immune suppression in SPF chickens

Avian Leukosis Viruses (ALVs) are associated with neoplasias, immune suppression and reduced performance in chicken flocks. In the present study, a naturally occurring recombinant strain of ALV (FJ15HT0) was isolated from an infected flock of Chinese Hetian chickens, and was subsequently identified as an exogenous ALV by immuno-fluorescence assay (IFA), PCR and following entire proviral DNA nucleotide sequencing. This isolate is revealed as a novel recombinant virus, lacking viral oncogenes, with the gp85 (93.4%) of subgroup B, the U3 (92.1%) and R (95.2%) region of subgroup J, the U5 (93.8%) region and 5UTR (95.7%) of subgroup C, as well as the gp37 (90.6%) and 3 (92.2%) of ALV-E. The simulative congenital infection with this isolate in SPF chickens resulted in significant weight loss (P<0.05) and a significant reduction in the humoral immune response to the live NDV vaccine (P<0.05), but not to the inactive AIV-H5 vaccine (P>0.05). Foci of lymphocytomas were observed in tissues of congenitally infected chickens at 11 weeks post-hatch, demonstrating the acute oncogenicity of the isolate.

Hericium erinaceus polysaccharide facilitates restoration of injured intestinal mucosal immunity in Muscovy duck reovirus-infected Muscovy ducklings

To elucidate the effect of Hericium erinaceus polysaccharide (HEP) on the intestinal mucosal immunity in normal and Muscovy duck reovirus (MDRV)-infected Muscovy ducklings, 1-day-old healthy Muscovy ducklings were pretreated with 0.2g/L HEP and/or following by MDRV infection in this study, duodenal samples were respectively collected at 1, 3, 6, 10, 15 and 21day post-infection, tissue sections were prepared for observation of morphological structure and determination of intestinal parameters (villus height/crypt depth ratio, villus surface area) as well as counts of intraepithelial lymphocytes (IELs), goblet cells, mast cells. Additionally, dynamics of secretory immunoglobin A (sIgA), interferon-γ (IFN-γ) and interleukin-4 (IL-4) productions in intestinal mucosa were measured with radioimmunoassay. Results showed that HEP significantly improved intestinal morphological structure and related indexes, and significantly inhibited the reduction of intestinal mucosal IELs, goblet cells and mast cells caused by MDRV infection. Furthermore, HEP significantly increased the secretion of sIgA, IFN-γ and IL-4 to enhance intestinal mucosal immune functions. Our findings indicate that HEP treatment can effectively repair MDRV-caused injures of small intestinal mucosal immune barrier, and improve mucosal immune function in sick Muscovy ducklings, which will provide valuable help for further application of HEP in prevention and treatment of MDRV infection.

Muscovy duck reovirus σNS protein triggers autophagy enhancing virus replication

BackgroundMuscovy duck reovirus (MDRV) causes high morbidity and mortality in Muscovy ducklings at 10xa0days old and can persist in an infected flock until the ducklings of 6xa0weeks old. It shares common physicochemical properties with avian reovirus (ARV) and differs in coding assignment and pathogenicity. The ARV p17 protein has been shown to trigger autophagy via activation multiple signaling pathways, which benefits virus replication. Since MDRV lacks the p17 protein, whether and how MDRV induces autophagy remains unknown. The aim of this study was to explore whether MDRV induces autophagy and which viral proteins are involved in MDRV-induced autophagy.MethodsThe autophagosome-like structures in MDRV-infected cells was observed under transmission electron microscopy. MDRV-induced autophagy was examined by analyzing the LC3-II level and phosphorylated form of mammalian target of rapamycin (mTOR) by Western blot assays. The effects of 3-methyladenine, rapamycin, chloroquine on viral yields were measured with quantitative(q) real-time reverse transcription (RT)-polymerase chain reaction (PCR) and 50% tissue culture infective dose (TCID50) assays, respectively. Additionally, to determine which viral protein is responsible for MDRV-induced autophagy, both p10.8- and σNS-encoding genes of MDRV were cloned into the pCI-neo-flag vector and transfected into DF-1 cells for detection of LC3-II.ResultsThe typical double-membrane vesicles containing cytoplasmic inclusions were visible in MDRV-infected immortalized chicken embryo fibroblast (DF-1) cells under transmission electron microscopy. Both primary Muscovy duck embryo fibroblasts (MDEF) and DF-1 cells infected with MDRV exhibited a significant increased levels of LC3-II accompanied with downregulation of phosphorylated form of mTOR, further confirming that MDRV is capable of inducing autophagy. Autophagy could be suppressed by 3-methylademine and induced by rapamycin and chloroquine. Furthermore, we found that σNS induces an increased levels of LC3-II, suggesting that the MDRV σNS protein is one of viral proteins involved in induction of autophagy. Both qRT-PCR and TCID50 assays showed that virus yield was increased in rapamycin treated DF-1 cells following MDRV infection. Conversely, when infected cells were pretreated with chloroquine, virus yield was decreased.ConclusionsThe MDRV σNS nonstructural protein is responsible for MDRV-induced autophagy and benefits virus replication.

Transcriptomic analysis reveals the molecular mechanism of apoptosis induced by Muscovy duck reovirus

This study was to investigate the molecular mechanism underlying the apoptosis induced by Muscovy duck reovirus (MDRV) through a transcriptomic analysis. Muscovy ducklings were infected with MDRV strain YB and the apoptotic cells in their livers were examined with terminal-deoxynucleotidyl-transferase-mediated nick end labeling and flow cytometry. Genes differentially expressed in the livers of the MDRV-infected ducklings were screened by comparing them with those of uninfected ducklings and were analyzed with a transcriptomic method to illuminate the mechanism of MDRV infection. The results showed that MDRV infection strongly induced apoptotic cells in liver. Significant pathway enrichment determined by a Kyoto Encyclopedia of Genes and Genomes analysis showed that MDRV activated the death receptor family signaling pathway (Fas, TNFR1), the interleukin receptor signaling pathway (IL1, IL3), the phosphatidylinositol 3-kinase signaling pathway, NF-ҝB signaling pathway and calcium ions signaling pathway to induce apoptosis. This was verified by SYBR-Green-based fluorescence quantitative PCR. In conclusion, MDRV induce apoptosis by activation multi signaling pathways.

Inhibitive effect on apoptosis in splenic lymphocytes of mice pretreated with Lingzhi (Ganoderma Lucidum) spores

OBJECTIVEnTo investigate how the pretreatment of mice with Ganoderma spores affected the apoptosis of their splenic lymphocytes induced by dexamethasone after 19 days treatment.nnnMETHODSnSixty Kunming mice were randomly divided into six groups: blank control groupdrenched with normal saline; a drug control group drenched with 150 mg/mL Ganoderma spores; a model group treated with saline; a low dose group with 50 mg/mL Ganoderma spores; a moderate dose group with 100 mg/mL Ganoderma spores; and a high dose group with 150 mg/mL Ganoderma spores. The effect of Ganoderma spores on apoptosis in spleen lymphocytes was analyzed. All groups were treated for 19 days. On day 20, the model group and the 3 treatment groups were intraperitoneally injected dexamethasone to induce apoptosis. Splenic index and apoptosis indes were employed to measure cell apoptosis.nnnRESULTSnThe results showed that Ganoderma spores reduced the splenic index to different degrees in each group and the best effect was seen in the high dose group (P < 0.05).Terminal dexynucleotidyl transferase (TdT)-mediated 2-Deoxyuridine 5-Triphosphate nick end labeling staining revealed that the apoptotic index in all groups administered Ganoderma spores differed significantly from the model group, and a dose-response was observed. Flow cytometric analysis indicated that spleen lymphocyte apoptosis in the model group was extensive. Each dose of Ganoderma spores inhibited dexamethasone-induced apoptosis in spleen lymphocytes, and a dose-response was observed as well. The highest dose of Ganoderma spores decreased Malondialdehyde content in serum induced by dexamethasone (P < 0.05).nnnCONCLUSIONnThe findings imply that the pretreatment of the mice with Ganoderma spores could reduce the apoptosis rate induced by dexamethasone in their splenic lymphocytes.