Duckling short beak and dwarfism syndrome virus infection activates host innate immune response involving both DNA and RNA sensors.

Duckling short beak and dwarfism syndrome virus (SBDSV), a newly identified goose parvovirus, causes devastating disease in domestic waterfowl and considerable economic losses to Chinese waterfowl industry. The molecular pathogenesis of SBDSV infection, nature and dynamics of host immune responses against SBDSV infection remained elusive. In this study, we systematically explored the relative mRNA expression profiles of major innate immune-related genes in SBDSV infected duck embryo fibroblasts. We found that SBDSV infection effectively activated host innate immune responses and resulted in significant up-regulation of IFN-ß and several vital IFN-stimulated genes (ISGs). These up-regulation responses were mainly attributed to viral genomic DNA and dsRNA replication intermediates. Importantly, the expression of cGAS was significantly induced, whereas the expression of other DNA receptors including DDX41, STING, ZBP1, LSM14A and LRRFIP1 have no significant change. Furthermore, SBDSV infection also activates the up-regulation of TLR3 and inhibited the expression of TLR2 and TLR4; however, no effect was observed on the expression of TLR1, TLR5, TLR7, TLR15 and TLR21. Intriguingly, SBDSV infection significantly up-regulated the expression of RNA sensors such as MDA5 and LGP2, and resulted in a delayed but significant up-regulation of RIG-I gene. Taken together, these data indicate that host multiple sensors including DNA sensor (cGAS) and RNA sensors (TLR3, MDA5 and LGP2) are involved in recognizing a variety of different pathogen associated molecular patterns (PAMPs) including viral genomic ssDNA and dsRNA replication intermediates, which trigger an effective antiviral innate immune response.

Development of a duplex SYBR Green I-based quantitative real-time PCR assay for the rapid differentiation of goose and Muscovy duck parvoviruses.

BACKGROUND: Waterfowl parvoviruses, including goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV), can cause seriously diseases in geese and ducks. Developing a fast and precise diagnosis assay for these two parvoviruses is particularly important. RESULTS: A duplex SYBR Green I-based quantitative real-time PCR assay was developed for the simultaneous detection and differentiation of GPV and MDPV. The assay yielded melting curves with specific single peak (Tm = 87.3 ± 0.26 °C or Tm = 85.4 ± 0.23 °C) when GPV or MDPV was evaluated, respectively. When both parvoviruses were assessed in one reaction, melting curves with specific double peaks were yielded. CONCLUSION: This duplex quantitative RT-PCR can be used to rapid identify of GPV and MDPV in field cases and artificial trials, which make it a powerful tool for diagnosing, preventing and controlling waterfowl parvovirus infections.

Isolation and characterization of a distinct duck-origin goose parvovirus causing an outbreak of duckling short beak and dwarfism syndrome in China.

Many mule duck and Cherry Valley duck flocks in different duck-producing regions of China have shown signs of an apparently new disease designated "short beak and dwarfism syndrome" (SBDS) since 2015. The disease is characterized by dyspraxia, weight loss, a protruding tongue, and high morbidity and low mortality rates. In order to characterize the etiological agent, a virus designated SBDSV M15 was isolated from allantoic fluid of dead embryos following serial passage in duck embryos. This virus causes a cytopathic effect in duck embryo fibroblast (DEF) cells. Using monoclonal antibody diagnostic assays, the SBDSV M15 isolate was positive for the antigen of goose parvovirus but not Muscovy duck parvovirus. A 348-bp (2604-2951) VP1gene fragment was amplified, and its sequence indicated that the virus was most closely related to a Hungarian GPV strain that was also isolated from mule ducks with SBDS disease. A similar disease was reproduced by inoculating birds with SBDSV M15. Together, these data indicate that SBDSV M15 is a GPV-related parvovirus causing SBDS disease and that it is divergent from classical GPV isolates.

Molecular characterization and phylogenetic analysis of porcine epidemic diarrhea virus (PEDV) samples from field cases in Fujian, China.

The outbreak of porcine epidemic diarrhea virus (PEDV) has been a big problem of swine industry in China in recent years. In this study, we investigated molecular diversity, phylogenetic relationships, and protein characterization of Fujian field samples with other PEDV reference strains. Sequence analysis of the S1 and sM genes showed that each sample had unique characteristics, and the sample P55 may be differentiated from the others by the unique deletions and insertions of sM gene. Phylogenetic analysis based on S1 or sM gene, which have high levels of variations, indicated that each sample was related to the specific reference strain, and this finding was consistent with the protein characterization prediction analysis. The study is useful to better understand the prevalence of PEDV and its prevention and control in Fujian.

The newly emerging duck-origin goose parvovirus in China exhibits a wide range of pathogenicity to main domesticated waterfowl.

Short beak and dwarfism syndrome virus (SBDSV) is a newly emerging distinct duck-origin goose parvovirus that belongs to the genus Dependovirus. Our previous studies have found that SBDSV was highly pathogenic to Cherry Valley ducklings and mule ducklings. However, little is known about its pathogenicity to other waterfowls. In the present study, the pathogenicity of SBDSV was evaluated in domesticated waterfowl including Muscovy ducklings, Sheldrake ducklings and domestic goslings. All experimentally infected birds exhibited remarkable growth retardation, anorexia and diarrhea similar to naturally infected birds. Interestingly, atrophic beaks and protruded tongues were not observed in all infection groups. At necropsies, no diagnostic pathological lesions were observed. Viral antigens existed in most organ tissues such as heart, liver, spleen, kidney, pancreas and intestine. All ducks in Muscovy duckling and Sheldrake duckling infected groups and 70% goslings in infected groups were seropositive for goose parvovirus (GPV) antibodies at 21dpi with the average titers as 28.4, 26.9, 24.0, respectively. Muscovy ducklings were more prominent in viral load and weight loss with a higher GPV antibodies titer than Sheldrake ducklings and goslings. Taken together, SBDSV exhibits a wide range of pathogenicity to main domesticated waterfowl with variable symptoms and cause considerable economic losses in China.

Sequence heterogeneity of the ORF3 gene of porcine epidemic diarrhea viruses field samples in Fujian, China, 2010-2012.

Twenty-seven field samples that showed positive in PEDV detection were collected from different farms of Fujian province from 2010 to 2012. Their heterogeneity was investigated by analysis of the ORF3 gene because of its potential function as a representation of virulence. According to the results, six Fujian strains in Group 1 showed a different genotype with unique point mutations, which might be used in differentiation between PEDV groups and brought potential antigenic variation. P55 and five reference strains in Group 2 had a long length deletion, showing another genotype and might be involved in the variation of virulence. Phylogenetic analysis revealed that the collected Fujian strains were very distant from the vaccine development strain CV777, which might be the reason why the vaccine was inefficient to control the disease. The results can help to reconsider the strategy of PEDV vaccine management and prevent outbreaks of PEDV-induced diarrhea more efficiently.