nzhu Xia

Lowly pathogenic avian influenza (H9N2) infection in Plateau pika (Ochotona curzoniae), Qinghai Lake, China

Avian influenza viruses (AIVs) are globally important contagions. Several domestic mammals can be infected with AIVs and may play important roles in the adaptation and transmission of these viruses in mammals, although the roles of wild mammals in the natural ecology of AIVs are not yet clear. Here, we performed a serological survey of apparently healthy Plateau pikas at Qinghai Lake in China to assess the prevalence of exposure to AIVs. Ninety-two of 293 (31%) of wild Plateau pikas possessed serum antibodies against a lowly pathogenic avian influenza (LPAI) H9N2 virus. Experimental inoculation of Plateau pikas with a LPAI H9N2 virus resulted in productive viral replication in respiratory tissues without prior adaptation. Our findings suggest that Plateau pikas represent a natural mammalian host to H9N2 AIVs and may play a role in the ongoing circulation of H9N2 viruses at Qinghai Lake in China. Surveillance for AIV infection in Plateau pika populations and other mammals that have close contact with the Plateau pikas should be considered.

Innate immune response gene expression profiles in central nervous system of mice infected with rabies virus.

The present study was focused on the modulation of innate immune response genes in CNS of mouse in response to rabies virus (RABV) infection. The global gene expression changes in brains of RABV- or mock-infected mice were investigated using DNA microarray analysis and quantitative real-time PCR. Then functional enrichment of the differentially expressed mRNAs was performed. Microarray analysis showed that 390 genes in brain were significantly (P<0.01) regulated in response to RABV infection, with obviously up-regulated genes like interferon (IFN) stimulated genes (ISGs), IFN inducible transcription factors, cytokines and complement, etc. The significant pathways of differentially expressed genes are mainly involved in JAK-STAT signaling pathway, antigen processing and presentation, ubiquitin mediated proteolysis and complement cascades. The results suggest that the modulated genes in infected CNS were possibly involved in pathogenesis of rabies. Conversely, they may have protective effects.

Inhibition of highly pathogenic avian influenza virus H5N1 replication by the small interfering RNA targeting polymerase A gene.

RNA interference is a form of post-transcriptional gene silencing mediated by small interfering RNAs (siRNAs), and it provides a powerful new means to specifically inhibit viral infection. In this study, three siRNAs (ps-PA496, ps-PA1116, and ps-PA1473) targeting the polymerase A (PA) gene of highly pathogenic avian influenza virus (HPAIV) H5N1 were designed and evaluated for their abilities to inhibit HPAIV replication. Results in vitro showed that the viral replication in the siRNAs-treated cells was 78-fold lower than that of the control for ps-PA496. Real-time PCR and indirect immunofluorescence assay also showed a significant reduction of the viral RNA level and protein expression. In vivo results showed a significant decrease of lung virus titers and an increase in the survival rate of infected mice pretreated with ps-PA496. These findings suggested that siRNAs targeting PA could efficiently inhibit HPAIV replication and these conserved regions might become potential therapeutic targets against influenza virus infection.

Adaptive amino acid substitutions enhance the virulence of a reassortant H7N1 avian influenza virus isolated from wild waterfowl in mice

H7 avian influenza viruses (AIVs) have caused a number of human infections, highlighting the pandemic potential of them. However, the factors that promote their replication in mammals remain poorly understood. Here, we generated mouse-adapted variants of a reassortant H7N1 virus to identify adaptive changes that confer enhanced virulence in mammals. The mouse lethal doses (MLD50) of the variants were reduced >10,000-fold compared to the parental virus. Adapted variants displayed enhanced replication kinetics in vitro and vivo, and were capable of replicating in multiple organs. Analysis of the variant virus genomes revealed amino acid changes in the PB2 (E627K), HA (H3 numbering; E114K, G205E, and G218E), and NA (S350N) proteins. Notably, some amino acid changes have been identified in natural H7 isolates. Our results implicate a number of amino acid substitutions that collectively enhance the ability of a wild bird-origin H7N1 AIV to replicate and cause severe disease in mice.

Changes in microRNA expression induced by rabies virus infection in mouse brains.

MicroRNAs (miRNAs) are small RNA (≈ 22 nt) molecules expressed endogenously in cells. They are involved in the regulation of gene expression. Recently, evidence has shown that cellular miRNAs have key regulatory roles in virus-host interactions. The rabies virus (RABV) causes a fatal infection of the central nervous systems (CNS) of warm-blooded animals, yet its pathogenesis remains poorly understood. To gain more insight into the pathogenesis of RABV, a miRNA microarray was performed as part of an investigation of changes in host miRNA expression in the brains of mice infected with RABV. The results showed that RABV infection induced modulation of the expression of sixteen miRNA molecules. These data were verified by real-time PCR. Functional analysis showed the differentially expressed miRNAs to be involved in many immune-related signaling pathways, such as the RIG-I-like receptor signaling pathway, JAK-STAT signaling pathway, chemokine signaling pathway, T-cell receptor signaling pathway, MAPK signaling pathway, leukocyte transendothelial migration, and natural killer cell mediated cytotoxicity. The predicted expression levels of the target genes of these modulated miRNAs correlated with measurements of gene expression measured by DNA microarray and qRT-PCR.

Adaptive amino acid substitutions enhance the virulence of an H7N7 avian influenza virus isolated from wild waterfowl in mice

Although H7N7 AIVs primarily circulate in wild waterfowl, documented cases of human infection with H7N7 viruses suggest they may pose a pandemic threat. Here, we generated mouse-adapted variants of a wild waterfowl-origin H7N7 virus to identify adaptive changes that confer enhanced virulence in mammals. The mouse lethal doses (MLD50) of the adapted variants were reduced >5000-fold compared to the parental virus. Mouse-adapted variants viruses displayed enhanced replication in vitro and in vivo, and acquired the ability to replicate in extrapulmonary tissues. These observations suggest that enhanced growth characteristics and modified cell tropism may increase the virulence of H7N7 AIVs in mice. Genomic analysis of the adapted variant viruses revealed amino acid changes in the PB2 (E627K), PB1 (R118I), PA (L550M), HA (G214R), and NA (S372N) proteins. Our results suggest that these amino acid substitutions collaboratively enhance the ability of H7N7 virus to replicate and cause severe disease in mammals.

Generation and characterization of a fusion protein of single-chain fragment variable antibody against hemagglutinin antigen of avian influenza virus and truncated protamine

The hemagglutinin antigen (HA) of avian influenza virus (AIV) is an immunogen abundant on the surfaces of infected cells, and can be used as a target for specific antibodies to clear viral infection. Protamine has been demonstrated to deliver DNA into cells effectively. Accordingly, a fusion protein of anti-HA single-chain fragment variable (scFv) and truncated protamine (tP) may be used as a vehicle for delivering the anti-AIV siRNA into the AIV-infected cells for gene therapy. To test this hypothesis, we constructed a novel recombinant plasmid, pET28-scFv-tP, by connecting the genes for anti-H5N1 AIV HA-specific scFv with synthesized oligonucleotides encoding the 22 amino acids of human tP and a linker. Furthermore, the recombinant scFV-tP was expressed and purified, with a yield of 7-8mg of scFv-tP and a purity of >92% from 1L of bacterial culture. Characterization of its bioactivity revealed that scFv-tP recognized HA, similar to its scFv control, in a dose-dependent manner and that the scFv-tP, but not its scFv control, bound to DNA and delivered plasmid and oligonucleotide DNA into the AIV-infected MDCK cells effectively. More importantly, transfection with the mixture of the scFv-tP and plasmid for the NP-specific siRNA significantly inhibited the replication of AIV in MDCK cells, as compared with that transfection with the scFv-plasmid mixture, even with the plasmid in liposome. Our data demonstrated that the recombinant scFv-tP retained the functions of both scFv and tP, and might be potentially used for delivering genetic materials for targeting therapy of AIV infection in vivo.

Contagious caprine pleuropneumonia in endangered Tibetan antelope, China, 2012.

To the Editor: Contagious caprine pleuropneumonia is a severe respiratory disease of goats caused by Mycoplasma capricolum subsp. capripneumoniae (Mccp), a member of the M. mycoides cluster (1). Mccp infection is associated with a 60% mortality rate and 90% illness rate, and the disease can cause substantial losses of livestock (1,2). We report a 2012 outbreak of contagious caprine pleuropneumonia in endangered Tibetan antelope (Pantholops hodgsonii) in China. n nIn 2000, the International Union of Conservation of Nature first listed the Tibetan antelope as an endangered species (3), and in 2004, the number of these antelope was estimated at 150,000 (4). Most Tibetan antelope live on China’s Qinghai–Tibet Plateau at an altitude of 3,700–5,500 m (3). n nDuring September–December 2012, ≈2,400 endangered Tibetan antelope were found dead in the Naqu area of Tibet; the dead animals represented 16% of the 15,000 Tibetan antelope thought to live in the area. Necropsy was performed on 13 of the antelope at sites within the Shenzha, Shuanghu, and Nima localities of the Naqu area (Technical Appendix Table 1). Gross pathologic lesions were localized exclusively to the lung, where severe pleuropneumonia with partial hepatization was observed (Figure, panel A). The lungs of some affected antelope displayed a thickening of the interlobular septa, pleuritis, and an accumulation of straw-colored pleural fluid. The pleural exudate solidified to form a gelatinous covering on the lung (Figure, panel B). n n n nFigure n nPneumonia caused by Mycoplasma capricolum subsp. capripneumoniae in Tibetan antelope (Pantholops hodgsonii), Tibet, 2012. A) Lung of a caprine pleuropneumonia–infected Tibetan antelope (sample SZM2) showing lung hepatization. B) Lung of a caprine ... n n n nSamples of lung tissue from 5 of the antelope were selected for histologic examination. Four of the samples showed fibrinous pneumonia with serofibrinous fluid and an inflammatory cell infiltrate consisting mainly of lymphocytes in the alveoli (Figure, panel C) and bronchioles (Figure, panel D). One sample showed pulmonary edema with a protein-rich fluid effusion in alveoli. n nLung tissue from each of the 13 antelope was minced and inoculated into modified Hayflick broth, which has been used extensively to isolate Mycoplasma spp. from animals. Cultures were incubated at 37°C in a humidified atmosphere of 5% CO2 (5). The medium was examined daily by comparing inoculated broth with an uninoculated control broth. Moderate turbidity, a color change from pink to yellow, and an appreciable swirl of the culture when rotated were used as indicators of mycoplasma growth. After 2–3 passages in culture, 11 of 13 samples showed growth of mycoplasma. The presence of mycoplasma-like particles in the 11 growth-positive cultures was confirmed by electron microscopy (Technical Appendix Figure 1). Collectively, these observations implicated mycoplasma as the cause of disease in the affected antelope. n nWe next screened lung samples from each of the 13 Tibetan antelope by PCR for evidence of M. mycoides cluster and M. bovis. Eleven samples were positive for Mccp, but no other types of mycoplasma were detected (Technical Appendix Tables 1, 2). We conducted PCR as described (6) on the arcD gene of Mccp. In brief, we conducted 35 cycles of 30 s at 94°C, 15 s at 47°C, and 15 s at 72°C. Of note, lung sample SH7, which showed pulmonary edema, was negative for mycoplasma by PCR and culture. Lung samples from the 13 dead Tibetan antelope were also tested for an additional 16 potential pathogens (Technical Appendix Tables 1, 2) by PCR or reverse transcription PCR. No pathogens other than Mccp were detected. n nTo assess the relationship of the Mccp strain isolated from infected Tibetan antelope with previously isolated Mccp strains and the closely related M. capricolum subsp. capricolum (Mcc), we analyzed a 562-bp segment of the H2 gene of Mccp, which was used to distinguish the Mccp and Mcc as reported by Lorenzon et al. (7), isolated from an infected Tibetan antelope in Shuanghu county (sample SH3). The partial H2 sequence (GenBank accession no. {type:entrez-nucleotide,attrs:{text:KC441725,term_id:478860002,term_text:KC441725}}KC441725) had higher sequence identity with Mccp isolates (99.3%–99.7%) than with Mcc isolates (90.2%–91.2% (Technical Appendix Figure 2). This phylogenetic analysis demonstrated that the Mccp isolated from infected Tibetan antelope belongs to the same clade as Mccp strains previously isolated in Africa and Asia. n nThe changing habitat of endangered Tibetan antelope may lead to increased exposure to Mccp, which can cause devastating outbreaks, such as the one reported here. Goats and sheep are herded on grasslands at an altitude of 4,300–5,000 m, the same area where Tibetan antelope reside. Goats are a reservoir for Mccp, and Mccp has been isolated from sheep in mixed herds with goats (8). Rail lines traverse the rangelands in this region, limiting the normal migration patterns of the Tibetan antelope population. Interaction among goats, sheep, and Tibetan antelope in this region, combined with the effect of human infringement on their rangeland, may increase the risk for disease emergence and transmission. n nOur results show that contagious caprine pleuropneumonia may pose a substantial threat to the survival of endangered Tibetan antelope. Surveillance for Mccp infection among Tibetan antelope populations and domestic and wild goat and sheep populations that have close contact with the Tibetan antelope should be considered. n nTechnical Appendix: nHistopathologic findings and results of pathogen testing, primer pairs used for pathogen testing, lung tissue findings, and phylogenetic tree. n nClick here to view.(546K, pdf)

Antisense oligonucleotides targeting the RNA binding region of the NP gene inhibit replication of highly pathogenic avian influenza virus H5N1

The H5N1 avian influenza virus (AIV) causes widespread infections in bird and human respiratory tracts, and vaccines and drug therapy are limited in their effectiveness. Recent studies of AIV structures have been published and provide new targets for designing antiviral drugs such as antisense oligonucleotides (AS ODNs), which effectively inhibit gene replication. In this study, we designed and synthesized three AS ODNs (NP267, NP628, NP749) that were specific for the RNA binding region of nucleoprotein (NP) based on AIV structure. Results showed that all three AS ODNs could inhibit viral replication in MDCK cells. The NP628 showed the best antiviral effect of all through viral titers, quantitative RT-PCR and indirect immunofluorescence (IFA) assays. In addition, the liposome mediated NP628 could partially protect the mice from a lethal H5N1 influenza virus challenge. Moreover, the NP628 group had a lower viral titer and lung index in the infected mice when compared with the viral control. Our results showed that AS ODN targeting of the AIV NP gene could potently inhibit AIV H5N1 reproduction, thus, formulating a candidate for an emergent therapeutic drug for the pathogenic H5N1 influenza virus infection.

Infection with street strain rabies virus induces modulation of the microRNA profile of the mouse brain

BackgroundRabies virus (RABV) causes a fatal infection of the central nervous systems (CNS) of warm-blooded animals. Once the clinical symptoms develop, rabies is almost invariably fatal. The mechanism of RABV pathogenesis remains poorly understood. Recent studies have shown that microRNA (miRNA) plays an important role in the pathogenesis of viral infections. Our recent findings have revealed that infection with laboratory-fixed rabies virus strain can induce modulation of the microRNA profile of mouse brains. However, no previous report has evaluated the miRNA expression profile of mouse brains infected with RABV street strain.ResultsThe results of microarray analysis show that miRNA expression becomes modulated in the brains of mice infected with street RABV. Quantitative real-time PCR assay of the differentially expressed miRNAs confirmed the results of microarray assay. Functional analysis showed the differentially expressed miRNAs to be involved in many immune-related signaling pathways, such as the Jak-STAT signaling pathway, the MAPK signaling pathway, cytokine-cytokine receptor interactions, and Fc gamma R-mediated phagocytosis. The predicted expression levels of the target genes of these modulated miRNAs were found to be correlated with gene expression as measured by DNA microarray and qRT-PCR.ConclusionRABV causes significant changes in the miRNA expression profiles of infected mouse brains. Predicted target genes of the differentially expression miRNAs are associated with host immune response, which may provide important information for investigation of RABV pathogenesis and therapeutic method.