Eukaryotic translation elongation factor 1 alpha (eEF1A) inhibits Siniperca chuatsi rhabdovirus (SCRV) infection through two distinct mechanisms.

IMPORTANCE: Although a virus can regulate many cellular responses to facilitate its replication by interacting with host proteins, the host can also restrict virus infection through these interactions. In the present study, we showed that the host eukaryotic translation elongation factor 1 alpha (eEF1A), an essential protein in the translation machinery, interacted with two proteins of a fish rhabdovirus, Siniperca chuatsi rhabdovirus (SCRV), and inhibited virus infection via two different mechanisms: (i) inhibiting the formation of crucial viral protein complexes required for virus transcription and replication and (ii) promoting the ubiquitin-proteasome degradation of viral protein. We also revealed the functional regions of eEF1A that are involved in the two processes. Such a host protein inhibiting a rhabdovirus infection in two ways is rarely reported. These findings provided new information for the interactions between host and fish rhabdovirus.

Fusing a TurboID tag with the Andrias davidianus ranavirus 2L reduced virus adsorption efficiency.

Andrias davidianus ranavirus (ADRV) is a member of the genus ranavirus (family Iridoviridae). ADRV 2L is an envelope protein that could be essential in viral infection. In the present study, the function of ADRV 2L was investigated by fusion with the biotin ligase TurboID tag. A recombinant ADRV with a V5-TurboID tag fused in the N-terminal of 2L (ADRVT-2L) and a recombinant ADRV expressing V5-TurboID (ADRVT) were constructed, respectively. Infection of the recombinant viruses and wild-type ADRV (ADRVWT) in the Chinese giant salamander thymus cell line (GSTC) showed that ADRVT-2L had reduced cytopathic effect and lower virus titers than the other two viruses, indicating the fusion of a big tag affected ADRV infection. Analysis of the temporal expression profile showed that the expression of V5-TurboID-2L was delayed than wild-type 2L. However, electron microscopy found that the virion morphogenesis was not affected in ADRVT-2L-infected cells. Furthermore, the virus binding assay revealed that the adsorption efficiency of ADRVT-2L was considerably decreased compared to the other two viruses. Therefore, these data showed that linking the TurboID tag to ADRV 2L affected virus adsorption to the cell membrane, which suggested an important role of 2L in virus entry into cells.

Genome Characteristics of Two Ranavirus Isolates from Mandarin Fish and Largemouth Bass.

Ranaviruses are promiscuous pathogens that threaten lower vertebrates globally. In the present study, two ranaviruses (SCRaV and MSRaV) were isolated from two fishes of the order Perciformes: mandarin fish (Siniperca chuatsi) and largemouth bass (Micropterus salmoides). The two ranaviruses both induced cytopathic effects in cultured cells from fish and amphibians and have the typical morphologic characteristics of ranaviruses. Complete genomes of the two ranaviruses were then sequenced and analyzed. Genomes of SCRaV and MSRaV have a length of 99, 405, and 99, 171 bp, respectively, and both contain 105 predicted open reading frames (ORFs). Eleven of the predicted proteins have differences between SCRaV and MSRaV, in which only one (79L) possessed a relatively large difference. A comparison of the sequenced six ranaviruses from the two fish species worldwide revealed that sequence identities of the six proteins (11R, 19R, 34L, 68L, 77L, and 103R) were related to the place where the virus was isolated. However, there were obvious differences in protein sequence identities between the two viruses and iridoviruses from other hosts, with more than half lower than 55%. Especially, 12 proteins of the two isolates had no homologs in viruses from other hosts. Phylogenetic analysis revealed that ranaviruses from the two fishes clustered in one clade. Further genome alignment showed five groups of genome arrangements of ranaviruses based on the locally collinear blocks, in which the ranaviruses, including SCRaV and MSRaV, constitute the fifth group. These results provide new information on the ranaviruses infecting fishes of Perciformes and also are useful for further research of functional genomics of the type of ranaviruses.

Development and characterization of a skin cell line from Chinese perch (Siniperca chuatsi) and its application in aquatic animal viruses.

Chinese perch (Siniperca chuatsi), an important fish for the aquaculture industry of China, is often affected by viral diseases. A stable and sensitive cell line can play an important role in virus identification and isolation, functional gene identification, virus pathogenic mechanism and antiviral immunity study. In the present study, a new cell line (S. chuatsi skin cell, SCSC) derived from the skin of S. chuatsi was established. The SCSC mainly consisted of fibroblastic-like cells, which grew well in M199 medium supplemented with 10% foetal bovine serum at 25°C. Chromosome analysis revealed that the SCSC (44%) has a diploid chromosome number of 2n = 48. The SCSC can be transfected and expressed exogenous gene efficiently. It also showed high sensitivity to several aquatic animal viruses from different families including Rhabdoviridae, Iridoviridae and Reoviridae. In addition, RT-PCR showed that S. chuatsi rhabdovirus (SCRV) started genome replication as early as 3 h post infection in the cells, which also induced the up-regulation of a variety of immune-related genes including these related to interleukin family, pattern recognition receptors, JAK-STAT pathway and interferon regulatory factors. In summary, current study provided a new tool in research of fish viruses and its interaction with host.

Replication and transcription machinery for ranaviruses: components, correlation, and functional architecture.

BACKGROUND: Ranaviruses (family Iridoviridae) are promiscuous pathogens that can infect across species barriers in poikilotherms and can replicate in amphibian and fish cells and even in cultured mammalian cells. However, as nucleocytoplasmic large DNA viruses (NCLDVs), their replication and transcription mechanisms remain largely unknown. Here, we screened and uncovered the replication and transcription machinery of two ranaviruses, Andrias davidianus ranavirus (ADRV) and Rana grylio virus (RGV), by a combination of methods, including the isolation of proteins on nascent DNA, recombinant virus-based affinity, and NanoLuc complementation assay. RESULTS: The ranavirus replication and transcription machinery was deeply dissected and identified as a complicated apparatus containing at least 30 viral and 6 host proteins. The viral proteins ADRV-47L/RGV-63R (DNA polymerase, vDPOL), ADRV-23L/RGV-91R (proliferating cell nuclear antigen, vPCNA), ADRV-85L/RGV-27R (single-stranded DNA binding protein, vSSB), ADRV-88L/RGV-24R (vhelicase/primase), etc., constitute the core replisome. Specifically, the core of the transcription complex, the viral RNA polymerase, contain the host RNAPII subunits Rpb3, Rpb6, and Rpb11, which was a first report in NCLDVs. Furthermore, correlations and interactions among these factors in the machinery were described. Significantly, the replisome core protein vDPOL (ADRV-47L) can interact with numerous viral and host proteins and could act as a linker and regulation center in viral DNA replication and transcription. Thus, these results depicted an architecture for ranavirus replication and transcription. CONCLUSIONS: Up to 36 components from ranavirus and their host were found to form viral replisomes and transcription complexes using a series of precise methods, which further constructed an architecture for ranavirus replication and transcription in which vDPOL was a key central factor and various components correlated and cooperated. Therefore, it provides a cornerstone for further understanding the mechanisms of the replication and transcription of ranaviruses which can ensure the efficient production of progeny virus and adaptation to cross-species infection.

Copper inhibits hatching of fish embryos via inducing reactive oxygen species and down-regulating Wnt signaling.

The copper ion (Cu2+) has been reported to suppress the hatching of fish. However, little is known about the underlying mechanism. In this study, copper nanoparticles (CuNPs) and Cu2+ were shown to significantly suppress hatching of zebrafish in a dosage-dependent manner, and reactive oxygen species (ROS) scavengers NAC (N-acetylcysteine) & GSH (reduced glutathione) and Wnt signaling agonist BIO (6-bromoindirubin-3'-oxime) significantly alleviated the suppressing effects of Cu2+ and CuNPs on egg hatching. Mechanistically, NAC, GSH, and BIO recovered the egg hatching in copper-treated group via increasing the embryonic motility rather than stimulating the expression and secretion of hatching enzymes before hatching. Additionally, no significant difference in egg hatching was observed between the control and Cu2+-treated group at 72 hpf (hours post fertilization) in cox17 mutant embryos, in which little ROS was producd after copper stimulation. This may be the first report that Cu2+ and CuNPs suppress embryonic motility and the subsequent hatching via inducing ROS and at the same time down-regulating Wnt signaling in fish embryos.

Eaf1 and Eaf2 mediate zebrafish dorsal-ventral axis patterning via suppressing Wnt/ß-Catenin activity.

During early vertebrate embryogenesis, maternal Wnt/ß-catenin signaling is thought to locally initiate expression of dorsal-specific genes. Here, eaf1 and eaf2 were identified as important maternal and zygotic modulators of Wnt signaling to initiate and specify ventral genes. Expression of ventral ved, vent, and vox was all obviously enhanced in either maternal or zygotic eaf1/2 morphants, and in both eaf1 heterozygous and homozygous mutants, but their expression was suppressed in embryos with over-expression of eaf1/2. Additionally, eaf1/2 were revealed to suppress ventral fates in embryos via Wnt/ß-catenin1/Tcf signaling, complimentary to their roles in suppressing dorsal fates via Wnt/ß-catenin2 signaling. Moreover, eaf1/2 were also revealed to obviously suppress the expression of axin2 induced by ß-catenin2 rather than by ß-catenin1, and the dorsal expression of axin2 in embryos was obviously suppressed by ectopic expression of eaf1/2. This study uncovers a novel dorsal-ventral patterning pathway, with eaf1 and eaf2 inhibiting ventral cells via suppressing Wnt/ß-catenin1/Tcf signaling and inducing dorsal cells indirectly via suppressing ß-catenin2-induced-axin2 on the dorsal side of embryos.

Transcriptional factors Eaf1/2 inhibit endoderm and mesoderm formation via suppressing TGF-ß signaling.

Eaf family genes act in multiple cellular responses such as tumor suppression and embryonic development. In our previous work, Eaf1/2 was found to modulate convergence and extension (C&E) movements and pattern the embryonic anterior-posterior axis during zebrafish embryogenesis. Here, we found that loss-of-function of eaf1/2 caused expanded mesoderm and endoderm in zebrafish embryos and led to the recovery of endoderm specification in TGF-ß factor-mzoeptz257 mutants, while gain-of-function of eaf1/2 induced reduced mesoderm and endoderm. Analyses of gene expression profiles in Eaf deleted or over-expressed mammalian cells indicated that the roles of Eaf1 and Eaf2 in inhibiting TGF-ß signals were conserved from fish to mammals. By taking advantages of TGF-ß reporters, eaf1/2-fused engrailed proteins, and P53M214K mutant, we revealed that Eaf1 and Eaf2 might suppress TGF-ß transduction by synergistically inhibiting none-P53 and P53-required TGF-ß signaling. Furthermore, Eaf1/2 might co-localize and interact with TGF-ß transcriptional factors in the transcriptional complex as repressors to target and suppress TGF-ß signaling activity. Our study unveiled a previously unrecognized link of Eaf1/2 genes with TGF-ß and P53 in vertebrates and demonstrated a conservation of TGF-ß suppression activity for Eaf1/2 family genes from fish to mammals, which might shed some light on the molecular mechanistic basis of Eaf1 and Eaf2 in tumor suppression.

Meta-analysis of serum non-high-density lipoprotein cholesterol and risk of coronary heart disease in the general population.

BACKGROUND: Non-high-density lipoprotein cholesterol (non-HDL-C) has been proposed an independent risk factor for coronary heart disease (CHD). However, the magnitude of this association in the general population varied considerably. OBJECTIVE: To investigate the association of baseline non-HDL-C level with CHD risk in the general population by conducting a meta-analysis. METHODS: A comprehensive literature search was performed in the Pubmed and Embase until January 2017. Prospective observational studies that investigated the association between baseline non-HDL-C level and CHD risk in the general population were included. Pooled hazard ratio (HR) and corresponding 95% confidence interval (CI) were calculated for the highest vs. the lowest non-HDL-C category. RESULTS: Seven articles with 9 independent prospective studies involving 448,732 individuals were included. Meta-analysis showed that individuals with the highest non-HDL-C level at baseline were associated with greater risk of CHD (RR 1.79; 95% CI 1.68-1.91) than those in the lowest non-HDL-C level category. Subgroup analysis suggested that the risk of CHD seemed more pronounced among men (HR 1.98; 95% CI 1.70-2.30) than among women (HR 1.63; 95% CI 1.35-1.96). CONCLUSIONS: Higher baseline non-HDL-C level is associated with increased risk of CHD in the general population. This risk seems more pronounced in men than in women. However, gender difference in non-HDL-C level associated with CHD risk should be verified by more well-designed prospective studies.

A chimeric dengue virus vaccine using Japanese encephalitis virus vaccine strain SA14-14-2 as backbone is immunogenic and protective against either parental virus in mice and nonhuman primates.

The development of a safe and efficient dengue vaccine represents a global challenge in public health. Chimeric dengue viruses (DENV) based on an attenuated flavivirus have been well developed as vaccine candidates by using reverse genetics. In this study, based on the full-length infectious cDNA clone of the well-known Japanese encephalitis virus live vaccine strain SA14-14-2 as a backbone, a novel chimeric dengue virus (named ChinDENV) was rationally designed and constructed by replacement with the premembrane and envelope genes of dengue 2 virus. The recovered chimeric virus showed growth and plaque properties similar to those of the parental DENV in mammalian and mosquito cells. ChinDENV was highly attenuated in mice, and no viremia was induced in rhesus monkeys upon subcutaneous inoculation. ChinDENV retained its genetic stability and attenuation phenotype after serial 15 passages in cultured cells. A single immunization with various doses of ChinDENV elicited strong neutralizing antibodies in a dose-dependent manner. When vaccinated monkeys were challenged with wild-type DENV, all animals except one that received the lower dose were protected against the development of viremia. Furthermore, immunization with ChinDENV conferred efficient cross protection against lethal JEV challenge in mice in association with robust cellular immunity induced by the replicating nonstructural proteins. Taken together, the results of this preclinical study well demonstrate the great potential of ChinDENV for further development as a dengue vaccine candidate, and this kind of chimeric flavivirus based on JE vaccine virus represents a powerful tool to deliver foreign antigens.

Development and characterization of the replicon system of Japanese encephalitis live vaccine virus SA14-14-2.

BACKGROUND: Viral self-replicating sub-genomic replicons represent a powerful tool for studying viral genome replication, antiviral screening and chimeric vaccine development. Many kinds of flavivirus replicons have been developed with broad applications. FINDINGS: The replicon system of JEV live vaccine strain SA14-14-2 was successfully developed in this study. Two kinds of replicons that express enhanced green fluorescent protein (EGFP) and Renilla luciferase (R.luc) were constructed under the control of SP6 promoter, respectively. Robust EGFP and R.luc signals could be detected in the replicon-transfected BHK-21 cells. Furthermore, the potential effects of selected amino acids in the C-terminal of envelope protein on replication were characterized using the replicon system. CONCLUSIONS: Our results provide a useful platform not only for the study of JEV replication, but also for antiviral screening and chimeric vaccine development.

Complete genome sequence of dengue virus serotype 2 Cosmopolitan genotype strain in Guangdong, China.

Here we report the complete genome sequence of a dengue virus serotype 2 (DENV-2) strain, GZ40, isolated in Guangdong, China, in 2010. A phylogenetic analysis classified GZ40 into the Cosmopolitan genotype, while previous Chinese DENV-2 isolates belong to the Asian I genotype. The reemergence of the Cosmopolitan genotype of DENV-2 in China deserves further investigation.

Development of RT-LAMP and real-time RT-PCR assays for the rapid detection of the new duck Tembusu-like BYD virus.

A new duck Tembusu virus (TMUV), also known as BYD virus, has been identified as the causative agent for the emerging duck egg-drop syndrome in mainland China. The rapid spread and wide distribution of the new TMUV in mainland China result in heavy loss to the poultry industry and pose great threats to public health. Rapid and sensitive detection methods are critical for prevention and control of TMUV infections. In this study, a reverse-transcription loop-mediated isothermal amplification assay (RT-LAMP) and an SYBR Green-I-based real-time RT-PCR assay specific for the duck TMUV were developed and validated with laboratory and field samples, respectively. The detection limits were 1 × 10(-4) and 1 × 10(-3) PFU per reaction for the RT-LAMP assay and real-time RT-PCR assay, respectively. The specificities were analyzed with other related members of the genus Flavivirus, and no cross-reaction was observed. Furthermore, both assays were evaluated with field samples, and they exhibited high sensitivity and specificity. In addition, the real-time RT-PCR assay worked well in viral load analysis, which revealed that the spleen may be the primary target for the replication of new duck TMUV in ducks. The TMUV-specific RT-LAMP and real-time RT-PCR assays will provide useful tools for the diagnosis and epidemiological surveillance of TMUV infection.

Complete genome sequence of a chikungunya virus isolated in Guangdong, China.

Chikungunya virus belongs to the genus Alphavirus in the family Togaviridae. Here we report the complete genome sequence of a chikungunya virus strain, GD05/2010, isolated in 2010 from a patient with chikungunya fever in Guangdong, China. The sequence information is important for surveillance of this emerging arboviral infection in China.

Co-circulation of two genotypes of dengue virus serotype 3 in Guangzhou, China, 2009.

Dengue is emerging as the most important mosquito borne viral disease in the world. In mainland China, sporadic and large outbreaks of dengue illness caused by the four serotypes of dengue virus (DENV-1 to DENV-4) have been well documented. Guangdong province is the major affected area in China, and DENV-1 has dominantly circulated in Guangdong for a long time. In this study, a family cluster of DENV-3 infection in Guangzhou was described. Three cases were diagnosed as dengue fever based on clinical manifestation, serological and RT-PCR assays. Two DENV-3 strains were isolated in C6/36 cells and the complete genome sequences were determined. Phylogenetic analysis revealed that the new DENV-3 isolates from the family cluster were grouped within genotype III. Considering the fact that several DENV-3 strains within genotype V were also identified in Guangzhou in 2009, at least two genotypes of DENV-3 co-circulated in Guangzhou. Careful investigation and virological analysis should be warranted in the future.

Complete genome sequence of a dengue virus serotype 4 strain isolated in Guangdong, China.

Here we report the first complete genome sequence of a dengue virus serotype 4 genotype II strain, GZ30, isolated in Guangzhou, Guangdong Province, China, in 2010. The sequence information provided herein will help us to understand the molecular epidemiology of dengue virus and predict the risk of severe diseases in mainland China.

A DNA-based West Nile virus replicon elicits humoral and cellular immune responses in mice.

While self-replicating, non-infectious subgenomic flavivirus replicons have been described, most of them are RNA transcripts under the control of an Sp6 or T7 promoter. In this study, using West Nile virus (WNV) as a model, a series of DNA-based reporter replicons under the control of a minimal cytomegalovirus (CMV) immediate-early promoter were constructed, and functional analysis showed that these reporter replicons replicate efficiently in mammalian cells. When the DNA-based WNV replicon was used to immunize mice, NS1-specific IgG antibodies and anti-WNV neutralizing antibodies were both induced. Additionally, immunization with this DNA-based WNV replicon induced high levels of lymphocyte proliferation and enhanced the secretion of IFN-γ. These results suggest that this type of DNA-based replicon can induce humoral and cellular immune responses in mice, indicating that this type of DNA-based replicon may serve as a useful platform for vaccine development and protein expression.

Cross protection against lethal West Nile virus challenge in mice immunized with recombinant E protein domain III of Japanese encephalitis virus.

Japanese encephalitis virus (JEV) and West Nile virus (WNV) are closely related mosquito-borne flaviviruses that cause severe encephalitic diseases with global impact. Cross protection among JEV and WNV has been previously described, and most cross reactive epitopes were identified within the domain II of E protein (EDII). In this study, the E protein domain III (EDIII) of JEV was successfully expressed in Escherichia coli, purified by a Ni-NTA column and characterized by Western blotting assay. Competitive inhibition assay showed that this recombinant JEV EDIII blocks the entry of JEV into BHK-21 cells. Mice immunized with the recombinant JEV EDIII developed high IgG and neutralizing antibodies titers against JEV. Most importantly, antibodies induced by JEV EDIII could neutralize WNV in vitro and partially protected mice against lethal WNV challenge. These results demonstrate that immunization with JEV EDIII induces cross-protective immunity against WNV infection, indicating a possible role of EDIII for the cross-protection among flavivirus.