Duck Tembusu Virus Nonstructural Protein 1 Antagonizes IFN-ß Signaling Pathways by Targeting VISA.

Duck Tembusu virus (DTMUV) is an emergent infectious pathogen that has caused severe disease in ducks and huge economic losses to the poultry industry in China since 2009. Previously, we showed that DTMUV inhibits IFN-ß induction early in infection; however, the mechanisms of the inhibition of innate immune responses remain poorly understood. In this study, we screened DTMUV-encoded structural and nonstructural proteins using reporter assays and found that DTMUV NS1 markedly suppressed virus-triggered IFN-ß expression by inhibiting retinoic acid-inducible gene I-like receptor signaling. Moreover, we found that DTMUV NS1 specifically interacted with the C-terminal domain of virus-induced signaling adaptor and impaired the association of retinoic acid-inducible gene I or melanoma differentiation-associated gene 5 and virus-induced signaling adaptor, thereby downregulating the retinoic acid-inducible gene I-like receptor-mediated signal transduction and cellular antiviral responses, leading to evasion of the innate immune response. Together, our findings reveal a novel mechanism manipulated by DTMUV to circumvent the host antiviral immune response.

Chinese border disease virus strain JSLS12-01 infects piglets and down-regulates the antibody responses of classical swine fever virus C strain vaccination.

During 2012 and 2013, several border disease virus (BDV) strains were identified from Chinese goat and sheep herds. At the same time, pigs from the same areas were found to be seropositive to BDV by ELISA, without showing clinical signs (unpublished data). To examine the susceptibility of pigs to the Chinese BDV strains, BDV isolate JSLS12-01, isolated from naturally infected sheep, was used to infect pigs. Antibody responses, viremia, clinical signs and pathological changes of the infected animals were examined. It confirmed that the current BDV strain could infect the domestic pigs, the animals showed viremia during 4 to 14 days post infection (dpi) and sero-conversion from 14dpi; no clinical and pathological changes were observed. In addition, CSFV maternal antibody did not influence BDV infection. Subsequently, pigs were infected with the BDV isolate and vaccinated with Hog cholera lapinized virus (HCLV) 21 days later to determine the effect of BDV infection on antibody induction of CSFV vaccination. The specific CSFV antibody and neutralizing antibody titers of the BDV infected group remained negative after the primary vaccination. Even after the boost vaccination, they were still significantly lower than those of the uninfected groups (p<0.05). These results indicated that BDV infection could down-regulate the antibody responses of CSFV C-strain vaccination. It should be paid attention that BDV prevalence in pig herds and in live vaccines might hamper the vaccination of CSF.

A novel parainfluenza virus type 3 (PIV3) identified from goat herds with respiratory diseases in eastern China.

Parainfluenza virus type 3 (PIV3) is one of the most important viral respiratory pathogens for humans and for many animals, but goat infection has been rarely reported. Starting in Aug 2013, goats in the Jiangsu and Anhui provinces of eastern China suffered severe respiratory diseases. In order to identify the causative agent, numerous related pathogens were tested with RT-PCR or PCR. A unique PIV3 strain was detected in most of the clinical nasal swabs or serum samples. The virus was isolated on MDBK cells and characterized by RT-PCR, nucleotide sequence analysis and hemagglutination test. The entire M and F gene coding regions, HN, 5'-UTR-N and L gene fragments were amplified using pairs of degenerate primers. Nucleotide, amino acid sequence alignments and phylogenetic analyses based on these genes indicated that the goat-derived PIV3 strain was distinct from previously reported BPIV3 genotypes and HPIV3 strains. The novel isolate, named JS2013, might be a potentially new member of the respirovirus genus. Goats were experimentally infected with JS2013 culture. The virus-inoculated goats displayed coughing and nasal discharges that were related to respiratory diseases. Viremia and virus shedding were detected during 4-10 days post-inoculation (dpi). Virus-specific HI antibodies became positive from 14 dpi. This is the first report of the detection of PIV3 from Chinese goat herds and genetic and pathogenetic characterization of the novel goat-derived PIV3.

Isolation and characterization of a Neisseria strain from the liver of a Chinese Peking duck.

A Neisseria strain, Neisseria sp. AH-N10, was isolated from liver of a Chinese Peking duck and characterized using a number of phenotypic and genotypic approaches. Based on scanning electron microscopy examination, the isolated strain has the typical structure of Neisseria species. Sequence comparison of 16S rRNA gene and phylogenetic analysis suggest that Neisseria sp. AH-N10 is closely related to Neisseria canis, which was previously isolated from a human dog bite wound. Animal infection experiments demonstrated that the isolated Neisseria sp. AH-N10 is pathogenic in ducks and mice. The pathogenicity to humans and evolutional origin of this Neisseria strain should be further investigated.

Development and validation of one-step SYBR green real-time RT-PCR for the rapid detection of newly emerged duck Tembusu virus.

Duck Tembusu virus (DTMUV) is a single-stranded positive-sense RNA virus that causes disease to emerge in duck flocks and results in huge economic losses to the duck industry. However, no vaccines and control measures are available in China to date. Development of reliable and fast detection methods is necessary to prevent and control this disease. Therefore, a one-step SYBR Green real-time reverse transcription polymerase chain reaction (RT-PCR) method is established here for DTMUV detection. The results show that the method can specifically detect DTMUV without cross-reactions with selected avian pathogens. The sensitivity of the assay was 1000 times greater than that of a conventional RT-PCR and able to test as few as 20 copies from RNA standard samples. The coefficients of variations of inter- and intra-assay values ranged from 0.09% to 0.36% and 0.1% to 0.23%, respectively. Testing 168 field samples and 96 experimentally infected samples by conventional RT-PCR and the one-step SYBR Green real-time RT-PCR, the positive rates were 35.1% and 73.8% from field samples and 30.2% and 64.6% from infected samples. The one-step SYBR Green real-time RT-PCR developed in this study was shown to be a sensitive, specific, high-throughput, cost-effective, and simple diagnostic tool for the rapid detection and epidemiological surveillance of the emerging DTMUV infection.

Genome Sequence of Border Disease Virus Strain JSLS12-01, Isolated from Sheep in China.

Border disease virus (BDV) is a recognized virus in the genus Pestivirus and causes border disease (BD) in sheep and goats. Here, a novel BDV strain, JSLS12-01, was identified from sheep in Jiangsu Province, China. The complete coding sequence (CDS) was finished, which provides a better understanding of the molecular evolution of BDV isolates.

An adapted duck Tembusu virus induces systemic infection and mediates antibody-dependent disease severity in mice.

Duck Tembusu virus (DTMUV) is a newly emerging infectious agent in China. Since 2010, this presumably arthropod-borne virus has caused severe disease in duck flocks. A cell-adapted DTMUV, designated AH10, has been developed. For this particular virus, replication, pathogenicity, and antibody-dependent enhancement (ADE) infection mediated by a specific antibody was investigated in mammalian cells and mice. The virus propagated in Vero or Hepa1-6 cells with a stable titer, and induced a visible cytopathic effect. Expression of pro- and anti-inflammatory cytokine genes in Hepa1-6 cells was elevated during early infection stages. AH10 was able to replicate in the brain, spleen, liver and kidneys of mice, and resulted in a systemic infection by day 5 when administered intracerebrally. When naïve mice were first transfused intraperitoneally with virus-specific antisera, upon subsequent infection, ADE of virus symptoms was observed. Mice displayed clinical symptoms by day 3 post-infection; weight loss in the AH10-specific antibody-treated group was observed 2-3 days earlier than that in the control groups. These findings indicate that AH10 was able to replicate in the mouse model, and that anti-AH10 antibodies caused ADE. The molecular basis of pathogenicity and ADE in the mouse model should be investigated in the future.

Cross-protective efficacy of recombinant transferrin-binding protein A of Haemophilus parasuis in guinea pigs.

The causative agent of Glasser's disease in swine is Haemophilus parasuis. Commercial bacterins are widely used for protection of the swine population. However, cross protection is limited because H. parasuis has more than 15 serovars. Transferrin-binding protein A has shown potential as a broad-spectrum vaccine candidate against homologous and heterologous strains. Here we amplified the full-length tbpA gene from an H. parasuis serovar 13 isolate and cloned it into a pET-SUMO expression vector. We then expressed and purified the TbpA protein by Ni affinity chromatography. First, the immunogenicity and protective efficacy of the protein were evaluated in guinea pigs by two subcutaneous immunizations with different doses of Montanide IMS 206 VG adjuvant. The immunized guinea pigs were, respectively, challenged on week 3 after a booster immunization with homologous strain LJ3 (serovar 13) and heterologous strain FX1 (serovar 4), and vaccine-inoculated groups were compared with nonvaccinated controls. All immunized groups showed serum antibody titers higher than those of negative-control groups. Furthermore, the cytokine and chemokine levels were evaluated at the transcriptional level by the real-time PCR analysis of six cytokines and chemokines. Gamma interferon and interleukin-5 in groups immunized with 100 µg were elevated more than 15-fold over those in negative-control groups. The protection rates were 80 and 60% after a challenge with strains LJ3 and FX1, respectively, in the groups vaccinated with 100 µg of recombinant TbpA protein. Subsequently, the data showed that guinea pigs immunized with a single dose (100 µg) were protected at levels of 80, 80, and 60% against LJ3, FX1, and another heterologous strain, SZ (serovar 14), respectively. The results indicate for the first time that TbpA protein cross protects guinea pigs against serovars 13, 4, and 14 of H. parasuis. Taken together, these results suggest that the recombinant TbpA protein is a promising vaccine candidate that needs to be confirmed in a swine population.

Complete genome sequence of a novel porcine enterovirus strain in China.

The porcine enteroviruses (PEVs) belong to the family Picornaviridae. We report a complete genome sequence of a novel PEV strain that is widely prevalent in pigs at least in central and eastern China. The complete genome consists of 7,390 nucleotides, excluding the 3' poly(A) tail, and has an open reading frame that maps between nucleotide positions 812 and 7318 and encodes a 2,168-amino-acid polyprotein. Phylogenetic analysis based on the 3CD and VP1 regions reveals that this PEV strain belongs to a species of PEV9 but may represent a novel sero-/genotype in CPE group III. We also report the major findings from bootscan analysis based on the whole genomes of PEVs in the present study and those available in GenBank.

Hepatitis E virus infection in central China reveals no evidence of cross-species transmission between human and swine in this area.

Hepatitis E virus (HEV) is a zoonotic pathogen of which several species of animal were reported as reservoirs. Swine stands out as the major reservoir for HEV infection in humans, as suggested by the close genetic relationship of swine and human virus. Since 2000, Genotype 4 HEV has become the dominant cause of hepatitis E disease in China. Recent reports showed that genotype 4 HEV is freely transmitted between humans and swine in eastern and southern China. However, the infection status of HEV in human and swine populations in central China is still unclear. This study was conducted in a rural area of central China, where there are many commercial swine farms. A total of 1476 serum and 554 fecal specimens were collected from the general human and swine populations in this area, respectively. The seroepidemiological study was conducted by enzyme-linked immunosorbent assay. Conserved genomic sequences of open reading frame 2 were detected using reverse transcription-PCR. The results indicated that the overall viral burden of the general human subjects was 0.95% (14/1476), while 7.0% (39/554) of the swine excreted HEV in stool. The positive rate of anti-HEV IgG and IgM in the serum samples was 7.9% (117/1476) and 1.6% (24/1476), respectively. Phylogenetic analysis based on the 150 nt partial sequence of the capsid protein gene showed that the 53 swine and human HEV isolates in the current study all belonged to genotype 4, clustering into three major groups. However, the HEV isolates prevalent in the human and swine populations were classified into known distinct subgenotypes, which suggested that no cross-species transmission between swine and humans had taken place in this area. This result was confirmed by cloning and phylogenetic analysis of the complete capsid protein gene sequence of three representative HEV strains in the three major groups. The cross reactivity between anti-HEV IgG from human sera and the two representative strains from swine in central China was confirmed by Dot-blot assay. In conclusion, although all the HEV strains prevalent in central China belonged to genotype 4, there is no evidence of cross-species transmission between human and swine in this area.