Phosphorylation of viral proteins plays important roles in the influenza A virus (IAV) life cycle. By using mass spectrometry, we identified tyrosine 132 (Y132) as a phosphorylation site of the matrix protein (M1) of the influenza virus A/WSN/1933(H1N1). Phosphorylation at this site is essential to the process of virus replication by controlling the nuclear import of M1. We further demonstrated that the phosphorylated tyrosine is crucial for the binding of M1 to the nuclear import factor importin-α1, since any substitutions at this site severely reduce this protein-protein interaction and damage the importin-α1-mediated nuclear import of M1. Additionally, the tyrosine phosphorylation which leads to the nuclear import of M1 is blocked by a Janus kinase inhibitor. The present study reveals a pivotal role of this tyrosine phosphorylation in the intracellular transportation of M1, which controls the process of viral replication.
An epidemic of an avian-origin H7N9 influenza virus has recently emerged in China, infecting 134 patients of which 45 have died. This is the first time that an influenza virus harboring an N9 serotype neuraminidase (NA) has been known to infect humans. H7N9 viruses are divergent and at least two distinct NAs and hemagglutinins (HAs) have been found, respectively, from clinical isolates. The prototypes of these viruses are A/Anhui/1/2013 and A/Shanghai/1/2013. NAs from these two viruses are distinct as the A/Shanghai/1/2013 NA has an R294K substitution that can confer NA inhibitor oseltamivir resistance. Oseltamivir is by far the most commonly used anti-influenza drug due to its potency and high bioavailability. In this study, we show that an R294K substitution results in multidrug resistance with extreme oseltamivir resistance (over 100 000-fold) using protein- and virus-based assays. To determine the molecular basis for the inhibitor resistance, we solved high-resolution crystal structures of NAs from A/Anhui/1/2013 N9 (R294-containing) and A/Shanghai/1/2013 N9 (K294-containing). R294K substitution results in an unfavorable E276 conformation for oseltamivir binding, and consequently loss of inhibitor carboxylate interactions, which compromises the binding of all classical NA ligands/inhibitors. Moreover, we found that R294K substitution results in reduced NA catalytic efficiency along with lower viral fitness. This helps to explain why K294 has predominantly been found in clinical cases of H7N9 infection under the selective pressure of oseltamivir treatment and not in the dominant human-infecting viruses. This implies that oseltamivir can still be efficiently used in the treatment of H7N9 infections.
H7N9; neuraminidase; virus fitness; sialidase activity; drug resistance; structural basis
As the most abundant liver-specific microRNA, miR-122 is involved in diverse aspects of hepatic function and neoplastic transformation. Our previous study showed that miR-122 levels are significantly decreased in hepatitis B virus (HBV)-infected patients, which may facilitate viral replication and persistence (S. Wang, L. Qiu, X. Yan, W. Jin, Y. Wang, L. Chen, E. Wu, X. Ye, G. F. Gao, F. Wang, Y. Chen, Z. Duan, and S. Meng, Hepatology 55:730–741, 2012). Loss of miR-122 expression in patients with hepatitis B enhances hepatitis B virus replication through cyclin G1-modulated P53 activity.). In this study, we provide evidence that all HBV mRNAs harboring an miR-122 complementary site act as sponges to bind and sequester endogenous miR-122, indicating that the highly redundant HBV transcripts are involved in HBV-mediated miR-122 suppression. We next identified pituitary tumor-transforming gene 1 (PTTG1) binding factor (PBF) as a target of miR-122 and demonstrated that HBV replication causes an obvious increase in PBF levels. Furthermore, we observed that the miR-122 levels were decreased and PBF was upregulated in chronic hepatitis B (CHB) and hepatocellular carcinoma (HCC). Overexpression and knockdown studies both revealed that PBF enhances proliferation and invasion of HCC cells, and silencing PBF resulted in a dramatic reduction of HCC tumor growth in vivo. Mechanistic analysis demonstrated that PBF interacts with PTTG1 and facilitates PTTG1 nuclear translocation, subsequently increasing its transcriptional activities. Therefore, we identified a novel HBV mRNA-miR-122-PBF regulatory pathway that facilitates malignant hepatocyte growth and invasion in CHB which may contribute to CHB-induced HCC development and progression. Our work underscores the reciprocal interplay of host miRNA sequestration and depletion by viral mRNAs, which may contribute to chronic-infection-related cancer.
Chicken interferon α (ChIFN-α) and ChIFN-β are type I IFNs that are important antiviral cytokines in the innate immune system. In the present study, we identified the virus-induced expression of ChIFN-α and ChIFN-β in chicken fibroblast DF-1 cells and systematically evaluated the antiviral activities of recombinant ChIFN-α and ChIFN-β by cytopathic-effect (CPE) inhibition assays. We found that ChIFN-α exhibited stronger antiviral activity than ChIFN-β in terms of inhibiting the replication of vesicular stomatitis virus, Newcastle disease virus and avian influenza virus, respectively. To elucidate the mechanism of differential antiviral activities between the two ChIFNs, we measured the relative mRNA levels of IFN-stimulated genes (ISGs) in IFN-treated DF-1 cells by real-time PCR. ChIFN-α displayed greater induction potency than ChIFN-β on several ISGs encoding antiviral proteins and MHC-I, whereas ChIFN-α was less potent than ChIFN-β for inducing ISGs involved in signaling pathways. In conclusion, ChIFN-α and ChIFN-β presented differential induction potency on various sets of ISGs, and the stronger antiviral activity of ChIFN-α is likely attributed to the greater expression levels of downstream antiviral ISGs.
Cyclophilin A (CypA) is the main member of the immunophilin superfamily that has peptidyl-prolyl cis-trans isomerase activity. CypA participates in protein folding, cell signaling, inflammation and tumorigenesis. Further, CypA plays critical roles in the replication of several viruses. Upon influenza virus infection, CypA inhibits viral replication by interacting with the M1 protein. In addition, CypA is incorporated into the influenza virus virions. Finally, Cyclosporin A (CsA), the main inhibitor of CypA, inhibits influenza virus replication through CypA-dependent and -independent pathways. This review briefly summarizes recent advances in understanding the roles of CypA during influenza virus infection.
influenza virus; Cyclophilin A; Cyclosporin A; virus-host interaction
The present study aimed to screen for urinary biomarkers of steroid-resistant nephrotic syndrome (SRNS) in children. These biomarkers were divided into three groups, the control, the steroid-sensitive nephrotic syndrome (SSNS) and the SRNS groups, which were composed of 45, 32 and 9 children, respectively. Urine samples were obtained and analyzed using Au-chips. Compared with the control group, the peak intensities of four proteins, measured using mass-to-charge ratios, were significantly increased in the primary nephrotic syndrome (PNS; SSNS and SRNS combined) group (P<0.01). The intensity of three and one peaks increased significantly in the SSNS and SRNS groups, respectively, compared with the control (P<0.01). Compared with the SRNS group, the intensity of one protein peak increased in the SSNS group (P<0.01). The diagnostic model was established based on these four protein peaks. The sensitivity and specificity of the model were 88.89 and 93.75%, respectively. Four differentially expressed proteins may consequently serve as urinary biomarkers for SRNS in children.
urinary proteomics; urine; steroid-resistant; biomarkers; nephrotic syndrome
The influenza A virus matrix 1 protein (M1) shuttles between the cytoplasm and the nucleus during the viral life cycle and plays an important role in the replication, assembly, and budding of viruses. Here, a leucine-rich nuclear export signal (NES) was identified specifically for the nuclear export of the M1 protein. The predicted NES, designated the Flu-A-M1 NES, is highly conserved among all sequences from the influenza A virus subtype, but no similar NES motifs are found in the M1 sequences of influenza B or C viruses. The biological function of the Flu-A-M1 NES was demonstrated by its ability to translocate an enhanced green fluorescent protein (EGFP)-NES fusion protein from the nucleus to the cytoplasm in transfected cells, compared to the even nuclear and cytoplasmic distribution of EGFP. The translocation of EGFP-NES from the nucleus to the cytoplasm was not inhibited by leptomycin B. NES mutations in M1 caused a nuclear retention of the protein and an increased nuclear accumulation of NEP during transfection. Indeed, as shown by rescued recombinant viruses, the mutation of the NES impaired the nuclear export of M1 and significantly reduced the virus titer compared to titers of wild-type viruses. The NES-defective M1 protein was retained in the nucleus during infection, accompanied by a lowered efficiency of the nuclear export of viral RNPs (vRNPs). In conclusion, M1 nuclear export was specifically dependent on the Flu-A-M1 NES and critical for influenza A virus replication.
The nuclear export of the influenza A virus ribonucleoprotein (vRNP) is crucial for virus replication. As a major component of the vRNP, nucleoprotein (NP) alone can also be shuttled out of the nucleus by interacting with chromosome region maintenance 1 (CRM1) and is therefore hypothesized to promote the nuclear export of the vRNP. In the present study, three novel nuclear export signals (NESs) of the NP—NES1, NES2, and NES3—were identified as being responsible for mediating its nuclear export. The nuclear export of NES3 was CRM1 dependent, whereas that of NES1 or NES2 was CRM1 independent. Inactivation of these NESs led to an overall nuclear accumulation of NP. Mutation of all three NP-NESs significantly impaired viral replication. Based on structures of influenza virus NP oligomers, these three hydrophobic NESs are found present on the surface of oligomeric NPs. Functional studies indicated that oligomerization is also required for nuclear export of NP. Together, these results suggest that the nuclear export of NP is important for virus replication and relies on its NESs and oligomerization.
Bioimpedance analysis (BIA) has been reported as helpful in identifying hypervolemia. Observation data showed that hypervolemic maintenance hemodialysis (MHD) patients identified using BIA methods have higher mortality risk. However, it is not known if BIA-guided fluid management can improve MHD patients’ survival. The objectives of the BOCOMO study are to evaluate the outcome of BIA guided fluid management compared with standard care.
This is a multicenter, prospective, randomized, controlled trial. More than 1300 participants from 16 clinical sites will be included in the study. The enrolment period will last 6 months, and minimum length of follow-up will be 36 months. MHD patients aged between 18 years and 80 years who have been on MHD for at least 3 months and meet eligibility criteria will be invited to participate in the study. Participants will be randomized to BIA arm or control arm in a 1:1 ratio. A portable whole body bioimpedance spectroscopy device (BCM—Fresenius Medical Care D GmbH) will be used for BIA measurement at baseline for both arms of the study. In the BIA arm, additional BCM measurements will be performed every 2 months. The primary intent-to-treat analysis will compare outcomes for a composite endpoint of death, acute myocardial infarction, stroke or incident peripheral arterial occlusive disease between groups. Secondary endpoints will include left ventricular wall thickness, blood pressure, medications, and incidence and length of hospitalization.
Previous results regarding the benefit of strict fluid control are conflicting due to small sample sizes and unstable dry weight estimating methods. To our knowledge this is the first large-scale, multicentre, prospective, randomized controlled trial to assess whether BIS-guided volume management improves outcomes of MHD patients. The endpoints of the BOCOMO study are of utmost importance to health care providers. In order to obtain that aim, the study was designed with very careful important considerations related to the endpoints, sample size, inclusion criteria, exclusion criteria and so on. For example, annual mortality of Beijing MHD patients was around 10%. To reach statistical significance, the sample size will be very large. By using composite endpoint, the sample size becomes reasonable and feasible. Limiting inclusion to patients with urine volume less than 800 ml/day the day before dialysis session will limit confounding due to residual renal function effects on the measured parameters. Patients who had received BIS measurement within 3 months prior to enrolment are excluded as data from such measurements might lead to protocol violation. Although not all patients enrolled will be incident patients, we will record the vintage of dialysis in the multivariable analysis.
Current Controlled Trials NCT01509937
Hemodialysis; Bioimpedance; Dry weight; Body composition monitor; Randomized controlled trial
An attenuated Australian strain of West Nile virus (WNV), Kunjin (KUN), shares ~98% amino acid homology with the pathogenic New York 99 NY99 strain (NY99). To investigate the viral factors involved in NY99 virulence we generated an infectious cDNA clone of the WNV NY99 4132 isolate from which virus was recovered and was shown to be indistinguishable from the parental isolate. We then introduced the regions of the NY99 non-structural (NS) proteins and/or untranslated regions (UTRs) into the KUN backbone. Chimeric KUN viruses containing NY99 5′UTR and the parts of NS coding region were more virulent in mice than parental KUN virus. Chimeric NY99 viruses, containing KUN NS2A protein with alanine 30 to proline substitution were significantly less cytopathic in cells and less virulent in mice. Our results identify the 5′UTR and NS proteins as WNV virulence determinants and confirm a role for the NS2A in WNV cytopathicity and virulence.
Flavivirus; West Nile virus; Kunjin virus; virulence factors; infectious clone; chimeric viruses
The matrix 1 (M1) protein of Influenza A virus plays many critical roles throughout the virus life cycle. The oligomerization of M1 is essential for the formation of the viral matrix layer during the assembly and budding process.
In the present study, we report that M1 can oligomerize in vitro, and that the oligomerization is pH-dependent. The N-terminal domain of M1 alone exists as multiple-order oligomers at pH 7.4, and the C-terminal domain alone forms an exclusively stable dimer. As a result, intact M1 can display different forms of oligomers and dimer is the smallest oligomerization state, at neutral pH. At pH 5.0, oligomers of the N-terminal domain completely dissociate into monomers, while the C-terminal domain remains in dimeric form. As a result, oligomers of intact M1 dissociate into a stable dimer at acidic pH.
Oligomerization of M1 involves both the N- and C-terminal domains. The N-terminal domain determines the pH-dependent oligomerization characteristic, and C-terminal domain forms a stable dimer, which contributes to the dimerization of M1. The present study will help to unveil the mechanisms of influenza A virus assembly and uncoating process.
The immunosuppressive drug cyclosporin A (CsA) has inhibitory effects on the replication of several viruses. The antiviral effects are through targeting the interaction between viral proteins and host factor cyclophilin A (CypA). CypA has been identified to interact with influenza A virus M1 protein and impair the early stage of the viral life cycle. In order to identify the effect of CsA on influenza virus replication, a CypA-depleted 293T cell line, which was named as 293T/CypA−, was constructed. The cytopathic effect (CPE) assay and the growth curve results indicated that CsA specifically suppressed the influenza A virus replication in a dose-dependent manner. CsA treatment had no effect on the viral genome replication and transcription but selectively suppressed the viral proteins expression. Further studies indicated that CsA could impair the nuclear export of viral mRNA in the absence of CypA. In addition, the antiviral activity of CsA was independent of calcineurin signaling. Finally, CsA could enhance the binding between CypA and M1. The above results suggested that CsA inhibited the replication of influenza A virus through CypA-dependent and -independent pathways.
Cyclophilin A (CypA) is a typical member of the cyclophilin family of peptidyl-prolyl isomerases and is involved in the replication of several viruses. Previous studies indicate that CypA interacts with influenza virus M1 protein and impairs the early stage of the viral replication. To further understand the molecular mechanism by which CypA impairs influenza virus replication, a 293T cell line depleted for endogenous CypA was established. The results indicated that CypA inhibited the initiation of virus replication. In addition, the infectivity of influenza virus increased in the absence of CypA. Further studies indicated that CypA had no effect on the stages of virus genome replication or transcription and also did not impair the nuclear export of the viral mRNA. However, CypA decreased the viral protein level. Additional studies indicated that CypA enhanced the degradation of M1 through the ubiquitin/proteasome-dependent pathway. Our results suggest that CypA restricts influenza virus replication through accelerating degradation of the M1 protein.
Major histocompatibility complex class I (MHC I)-restricted CD8+ T-cell responses play a pivotal role in anti-human immunodeficiency virus (HIV) immunity and the control of viremia. The rhesus macaque is an important animal model for HIV-related research. Among the MHC I alleles of the rhesus macaque, Mamu-A*02 is prevalent, presenting in ≥20% of macaques. In this study, we determined the crystal structure of Mamu-A*02, the second structure-determined MHC I from the rhesus macaque after Mamu-A*01. The peptide presentation characteristics of Mamu-A*02 are exhibited in complex structures with two typical Mamu-A*02-restricted CD8+ T-cell epitopes, YY9 (Nef159 to -167; YTSGPGIRY) and GY9 (Gag71 to -79; GSENLKSLY), derived from simian immunodeficiency virus (SIV). These two peptides utilize similar primary anchor residues (Ser or Thr) at position 2 and Tyr at position 9. However, the central region of YY9 is different from that of GY9, a difference that may correlate with the immunogenic variance of these peptides. Further analysis indicated that the distinct conformations of these two peptides are modulated by four flexible residues in the Mamu-A*02 peptide-binding groove. The rare combination of these four residues in Mamu-A*02 leads to a variant presentation for peptides with different residues in their central regions. Additionally, in the two structures of the Mamu-A*02 complex, we compared the binding of rhesus and human β2 microglobulin (β2m) to Mamu-A*02. We found that the peptide presentation of Mamu-A*02 is not affected by the interspecies interaction with human β2m. Our work broadens the understanding of CD8+ T-cell-specific immunity against SIV in the rhesus macaque.
H9N2 influenza A viruses have undergone extensive reassortments in different host species, and could lead to the epidemics or pandemics with the potential emergence of novel viruses.
To understand the genetic and pathogenic features of early and current circulating H9N2 viruses, 15 representative H9N2 viruses isolated from diseased chickens in northern China between 1998 and 2010 were characterized and compared with all Chinese H9N2 viruses available in the NCBI database. Then, the representative viruses of different genotypes were selected to study the pathogenicity in mice with the aim to investigate the adaptation and the potential pathogenicity of the novel H9N2 reassortants to mammals.
Our results demonstrated that most of the 15 isolates were reassortants and generated four novel genotypes (B62-B65), which incorporated the gene segments from Eurasian H9N2 lineage, North American H9N2 branch, and H5N1 viruses. It was noteworthy that the newly identified genotype B65 has been prevalent in China since 2007, and more importantly, different H9N2 influenza viruses displayed a diverse pathogenicity to mice. The isolates of the 2008-2010 epidemic (genotypes B55 and B65) were lowly infectious, while two representative viruses of genotypes B0 and G2 isolated from the late 1990s were highly pathogenic to mice. In addition, Ck/SD/LY-1/08 (genotype 63, containing H5N1-like NP and PA genes) was able to replicate well in mouse lungs with high virus titers but caused mild clinical signs.
Several lines of evidence indicated that the H9N2 influenza viruses constantly change their genetics and pathogenicity. Thus, the genetic evolution of H9N2 viruses and their pathogenicity to mammals should be closely monitored to prevent the emergence of novel pandemic viruses.
avian influenza virus; H9N2; reassortant; genotype; pathogenicity
The nucleoprotein (NP) of influenza A virus is a multifunctional protein that plays a critical role in the replication and transcription of the viral genome. Therefore, examining host factors that interact with NP may shed light on the mechanism of host restriction barriers and the tissue tropism of influenza A virus. Here, Cyclophilin E (CypE), a member of the peptidyl-propyl cis-trans isomerase (PPIase) family, was found to bind to NP and inhibit viral replication and transcription.
In the present study, CypE was found to interact with NP but not with the other components of the viral ribonucleoprotein complex (vRNP): PB1, PB2, and PA. Mutagenesis data revealed that the CypE domain comprised of residues 137–186 is responsible for its binding to NP. Functional analysis results indicated that CypE is a negative regulator in the influenza virus life cycle. Furthermore, knock-down of CypE resulted in increased levels of three types of viral RNA, suggesting that CypE negatively affects viral replication and transcription. Moreover, up-regulation of CypE inhibited the activity of influenza viral polymerase. We determined that the molecular mechanism by which CypE negatively regulates influenza virus replication and transcription is by interfering with NP self-association and the NP-PB1 and NP-PB2 interactions.
CypE is a host restriction factor that inhibits the functions of NP, as well as viral replication and transcription, by impairing the formation of the vRNP. The data presented here will help us to better understand the molecular mechanisms of host restriction barriers, host adaptation, and tissue tropism of influenza A virus.
A nested Kirkpatrick–Baez mirror pair has been designed, fabricated and tested for achromatic nanofocusing synchrotron hard X-rays. The prototype system achieved a FWHM focal spot of about 150 nm in both horizontal and vertical directions.
The first test of nanoscale-focusing Kirkpatrick–Baez (KB) mirrors in the nested (or Montel) configuration used at a hard X-ray synchrotron beamline is reported. The two mirrors are both 40 mm long and coated with Pt to produce a focal length of 60 mm at 3 mrad incident angle, and collect up to a 120 µm by 120 µm incident X-ray beam with maximum angular acceptance of 2 mrad and a broad bandwidth of energies up to 30 keV. In an initial test a focal spot of about 150 nm in both horizontal and vertical directions was achieved with either polychromatic or monochromatic beam. The nested mirror geometry, with two mirrors mounted side-by-side and perpendicular to each other, is significantly more compact and provides higher demagnification than the traditional sequential KB mirror arrangement. Ultimately, nested mirrors can focus larger divergence to improve the diffraction limit of achromatic optics. A major challenge with the fabrication of the required mirrors is the need for near-perfect mirror surfaces near the edge of at least one of the mirrors. Special polishing procedures and surface profile coating were used to preserve the mirror surface quality at the reflecting edge. Further developments aimed at achieving diffraction-limited focusing below 50 nm are underway.
hard X-ray nanofocusing; achromatic; nested Kirkpatrick–Baez; Montel
Heat shock protein 70 (Hsp70) was identified as a cellular interaction partner of the influenza virus ribonucleoprotein (RNP) complex. The biological significance of the interaction between Hsp70 and RNP has not been fully investigated.
Here we demonstrated that Hsp70 was involved in the regulation of influenza A viral transcription and replication. It was found that Hsp70 was associated with viral RNP by directly interacting with the PB1 and PB2 subunits, and the ATPase domain of Hsp70 was required for the association. Immunofluorescence analysis showed that Hsp70 was translocated from the cytoplasm into the nucleus in infected cells. Then we found that Hsp70 negatively regulated the expression of viral proteins in infected cells. Real-time PCR analysis revealed that the transcription and replication of all eight viral segments were significantly reduced in Hsp70 overexpressed cells and greatly increased as Hsp70 was knocked down by RNA interference. Luciferase assay showed that overexpression of Hsp70 could inhibit the viral RNP activity on both vRNA and cRNA promoters. Biochemical analysis demonstrated that Hsp70 interfered with the integrity of RNP. Furthermore, delivered Hsp70 could inhibit the replication of influenza A virus in mice.
Our study indicated that Hsp70 interacted with PB1 and PB2 of RNP and could interfere with the integrity of RNP and block the virus replication in vitro and in vivo possibly through disrupting the binding of viral polymerase with viral RNA.
The importance of enhancing influenza resistance in domestic flocks is quite clear both scientifically and economically. Chicken is very susceptible to influenza virus. It has been reported that human cellular cyclophilin A (CypA) impaired influenza virus infection in 293T cells. Whether chicken CypA (chCypA) inhibits influenza virus replication is not known. The molecular mechanism of resistance in chicken to influenza virus remains to be studied.
The chCypA gene was isolated and characterized in the present study. It contained an ORF of 498 bp encoding a polypeptide of 165 amino acids with an estimated molecular mass of 17.8 kDa sharing high identity with mammalian CypA genes. The chCypA demonstrated an anti-influenza activity as expected. ChCypA protein was shown to be able to specifically interact with influenza virus M1 protein. Cell susceptibility to influenza virus was reduced by over-expression of chCypA in CEF cells. The production of recombinant influenza virus A/WSN/33 reduced to one third in chCypA expressing cells comparing to chCypA absent cells. ChCypA was widely distributed in a variety of chicken tissues. It localized in cytoplasm of chicken embryo fibroblast (CEF) cells. Avian influenza virus infection induced its translocation from cytoplasm into nucleus. ChCypA expression was not significantly up-regulated by avian influenza virus infection. The present study indicated that chCypA was an inhibitory protein to influenza virus replication, suggesting a role as an intrinsic immunity factor against influenza virus infection.
The present data demonstrates that chCypA possesses anti-influenza virus activity which allows the consideration of genetic improvement for resistance to influenza virus in chickens.
Flaviviruses transmitted by arthropods represent a tremendous disease burden for humans, causing millions of infections annually. All vector-borne flaviviruses studied to date suppress host innate responses to infection by inhibiting alpha/beta interferon (IFN-α/β)-mediated JAK-STAT signal transduction. The viral nonstructural protein NS5 of some flaviviruses functions as the major IFN antagonist, associated with inhibition of IFN-dependent STAT1 phosphorylation (pY-STAT1) or with STAT2 degradation. West Nile virus (WNV) infection prevents pY-STAT1 although a role for WNV NS5 in IFN antagonism has not been fully explored. Here, we report that NS5 from the virulent NY99 strain of WNV prevented pY-STAT1 accumulation, suppressed IFN-dependent gene expression, and rescued the growth of a highly IFN-sensitive virus (Newcastle disease virus) in the presence of IFN, suggesting that this protein can function as an efficient IFN antagonist. In contrast, NS5 from Kunjin virus (KUN), a naturally attenuated subtype of WNV, was a poor suppressor of pY-STAT1. Mutation of a single residue in KUN NS5 to the analogous residue in WNV-NY99 NS5 (S653F) rendered KUN NS5 an efficient inhibitor of pY-STAT1. Incorporation of this mutation into recombinant KUN resulted in 30-fold greater inhibition of JAK-STAT signaling than with the wild-type virus and enhanced KUN replication in the presence of IFN. Thus, a naturally occurring mutation is associated with the function of NS5 in IFN antagonism and may influence virulence of WNV field isolates.
H3N2 is one of the main subtypes of influenza virus which circulates in human and swine population throughout the world.
To investigate the genetic correlation between H3N2 human and swine influenza viruses from the same region during the same season.
Five H3N2 human and four H3N2 swine influenza viruses were isolated from Guangdong province of China in the winter of 2005. The molecular evolution of eight gene segments was analyzed.
In the phylogenetic trees of gene segments, all H3N2 human isolates along with the 2000’s human isolates formed a cluster, and most of the H3N2 swine isolates along with the 1990’s human isolates formed another cluster except that the M and NS gene of A/Swine/Guangdong/01/2005 and the PA gene of A/Swine/Guangdong/02/2005 fell into the cluster of the classical swine influenza virus, indicating the reassortment between H3N2 human and H1N1 swine influenza viruses.
In this study, H3N2 swine influenza viruses in 2005 did not originate from the 2000’s H3N2 human influenza viruses, but from the 1990’s H3N2 human isolates. In addition, the reassortment of H3N2 human and H1N1 swine influenza virus in pigs was common in recent years.
influenza virus; H3N2 subtype; human; swine; genetic correlation; reassortment
Single-crystal diffuse X-ray microdiffraction was used to characterize radiation-induced defects in individual grains of a polycrystalline proton-irradiated Fe foil.
Single-crystal diffuse X-ray scattering was used to characterize radiation-induced defects in individual grains of a polycrystalline proton-irradiated Fe foil. The grains were probed with an intense 1 µm X-ray beam to demonstrate that both polycrystalline and micrometer-scale samples can be studied with single-crystal-like signal-to-noise. Scattering was measured with an X-ray-sensitive area detector, which measures intensity over a surface in reciprocal space. By scanning the X-ray energy, the intensity was measured over reciprocal-space volumes. Since the sample is not rotated, the real-space scattering volume does not change. Methods to minimize experimental artifacts arising from the use of an area detector are described.
microdiffraction; irradiation; diffuse scattering