Egg Drop Syndrome Research Articles

Nitric Oxide Production and Fc Receptor-Mediated Phagocytosis as Functional Readouts of Macrophage Activity upon Stimulation with Inactivated Poultry Vaccines In Vitro.

Vaccine batches must pass routine quality control to confirm that their ability to induce protection against disease is consistent with batches of proven efficacy from development studies. For poultry vaccines, these tests are often performed in laboratory chickens by vaccination-challenge trials or serological assays. The aim of this study was to investigate innate immune responses against inactivated poultry vaccines and identify candidate immune parameters for in vitro quality tests as alternatives for animal-based quality tests. For this purpose, we set up assays to measure nitric oxide production and phagocytosis by the macrophage-like cell line HD11, upon stimulation with inactivated poultry vaccines for infectious bronchitis virus (IBV), Newcastle disease virus (NDV), and egg drop syndrome virus (EDSV). In both assays, macrophages became activated after stimulation with various toll-like receptor agonists. Inactivated poultry vaccines stimulated HD11 cells to produce nitric oxide due to the presence of mineral oil adjuvant. Moreover, inactivated poultry vaccines were found to enhance Fc receptor-mediated phagocytosis due to the presence of allantoic fluid in the vaccine antigen preparations. We showed that inactivated poultry vaccines stimulated nitric oxide production and Fc receptor-mediated phagocytosis by chicken macrophages. Similar to antigen quantification methods, the cell-based assays described here can be used for future assessment of vaccine batch-to-batch consistency. The ability of the assays to determine the immunopotentiating properties of inactivated poultry vaccines provides an additional step in the replacement of current in vivo batch-release quality tests.

Duck Tembusu Virus Utilizes miR-221-3p Expression to Facilitate Viral Replication via Targeting of Suppressor of Cytokine Signaling 5.

Duck Tembusu virus (DTMUV), a member of Flaviviridae family, causes acute egg-drop syndrome in ducks. MicroRNAs (miRNAs) have been found to be involved in various biological processes, including tumor genesis, viral infection, and immune response. However, the functional effect of miRNAs on DTMUV replication remains largely unclear. This study aimed to elucidate the role of host microRNA-221-3p (miR−221-3p) in regulating DTMUV replication. Here, we indicated that the expression of miR−221-3p was significantly upregulated in duck embryo fibroblasts (DEFs) during DTMUV infection. Transfection of miR-221-3p mimic significantly reduced interferon (IFN) β production, whereas transfection of miR-221-3p inhibitor conversely significantly increased the expression of IFN-β in DTMUV-infected DEF. Moreover, we found that viral RNA copies, viral E protein expression level, and virus titer, which represent the replication and proliferation of virus, were all enhanced when transfecting the miR-221-3p mimic into DEF; reverse results were also observed by transfecting the miR-221-3p inhibitor. We also found that the expression of suppressor of cytokine signaling 5 (SOCS5) was downregulated in DEF infected with DTMUV. Besides, we further proved that SOCS5 is a target of miR-221-3p and that miR-221-3p could negatively modulate SOCS5 expression at both mRNA and protein levels. Finally, our results showed that overexpression of SOCS5 inhibited DTMUV replication and knockdown of SOCS5 enhanced DTMUV replication. Thus, our findings reveal a novel host evasion mechanism adopted by DTMUV via miR-221-3p, which may hew out novel strategies for designing miRNA-based vaccines and therapies.

Potential Vector Competence of Mosquitoes to Transmit Baiyangdian Virus, a New Tembusu-Related Virus in China.

A new duck Tembusu-related flavivirus, Baiyangdian virus (BYDV), caused duck egg-drop syndrome in China. The rapid spread, unknown transmission routes, and zoonotic nature, raise serious concern about BYDV as a potential threat to human health. The study provides the first evaluation on the vector competence of Culex and Aedes mosquitoes to transmit BYDV in China. The results show that Culex tritaeniorhynchus, Culex pipiens pallens, Culex pipiens quinquefasciatus, and Aedes albopictus can become infected with BYD-1 virus (BYDV-1) on different days after oral infection. Although the viral copies in Ae. albopictus was higher than that in Cx. p. quinquefasciatus at 13 days postinfection (χ2 = 10.385, p = 0.016), there was no significant differences between infection rates of four mosquito species (χ2 = 3.98, p = 0.137). In transmission experiment, healthy ducks were infected after being bitten by virus-positive mosquitoes and BYDV-1 disseminated to and replicated in the duck brains. These findings verified the potential role of Cx. p. quinquefasciatus and Cx. tritaeniorhynchus as vectors of BYDV-1. BYDV-1 was also detected in salivary gland of Cx. p. pallens, which indicated that this virus could be transmitted by mosquitoes. These results provide evidence for the role of Culex mosquitoes in the transmission cycles involving BYDV-1 and avian hosts in China.

Non-specific resistance and specific immunogenesis of the body of the bird cross Loman Brown on the background of biostimulation

PV-1 immunostimulant influence on the parameters of non-specific resistance and specific immunogenesis of bird cross Loman Brown is discussed in the paper. It was established experimentally that feeding chickens by the PV-1 preparation in doses of 0.05 ml/kg, 0.10 and 0.15 ml/kg of body weight, respectively, once a day within 10 days with a 10-day break, with repeating cycles up to 111-day of their age, stimulates the growth and development of young. Immunization of a bird against the background of the use of the immunotropic drug PV-1 is accompanied by an increase in immunity: when chickens are vaccinated against Gumboro disease, the titers of specific antibodies are increased by 53.3%, against Newcastle’s disease - by 50.0% and against egg drop syndrome-76 - by 26.5%. An increase in the egg productivity of laying hens grown on the background of the use of PV-1 was established: egg production for the initial hen increased by 9.2 - 17.8%, egg weight - by 0.5 - 4.6%. Studying the meat productivity of poultry grown on the background of the use of the PV-1 preparation, an increase in the slaughter yield of 1.7–5.0% was established, the yield of edible parts increased by 6 ±3.20 – 155±3.40 g (P <0.001).

Seroprevalensi Penyakit Egg Drop Syndrome pada Itik di Desa Tumbak Bayuh, Kecamatan Mengwi, Badung, Bali

Egg Drop Syndrome can cause detrimental impacts on breeders due to reducing production and quality of theaffected eggs.This study aim was to determine the seroprevalece ofantibody against Egg Drop Syndrome (EDS) virus in ducks. Antibody titers examination was done from 75blood samplesof ducks thathave not been vaccinatedagainstEDS virus. The duck samples were collected from Tumbak Bayuh Village, Mengwi, Badung. Serological examination was held at the Virology Laboratory,Faculty of Veterinary Medicine, Udayana University by usingHaemagglutination Inhibition (HI) test. HI test results showed that 24 samples were positive contained antibody of the EDS,while 51 samples were negative. Range of EDS antibody titer observed was from24 to 27 HI units. This results indicates that the ducks have protective antibody titer against EDS virus. The positive serum samples were also tested using HI test against Newcastle Disease (ND) virus with negative result. It can be concluded that the ducks in Tumbak Bayuh Village, Mengwi, Badung have 32% of antibody titer against EDS virus whichmight result from being exposed by EDS virus naturally.

Development of novel subunit vaccine based on truncated fiber protein of egg drop syndrome virus and its immunogenicity in chickens

Egg-drop syndrome virus (EDSV) is an avian adenovirus that causes markedly decrease in egg production and in the quality of the eggs when it infects chickens. In this report, we engineered truncated fiber protein containing the entire knob domain and part of the shaft region as a vaccine candidate. The protein was obtained in the soluble fraction in Escherichia coli (E. coli), and expression level after nickel-affinity purification was 126 mg/L. By means of multiple characterization methods, it is demonstrated that the recombinant protein retains the native trimeric structure. A single inoculation with the structure-stabilized recombinant protein, even at the lowest dose of 2 μg, stimulated hemagglutination inhibition (HI) antibody responses in chickens, for at least 16 weeks. Neutralizing titers in sera from the protein immunized groups was similar to that of inactivated vaccine immunized group. The lymphocyte proliferation response and cytokine secretion were also induced in immunized SPF chickens. In addition, immunization with the fiber protein also significantly reduced the viral load in the liver. Taken together, these results suggest the truncated fiber protein as an effective single dose, long lasting and rapidly effective vaccine to protect against EDSV.

Unravelling the receptor binding property of egg drop syndrome virus (EDSV) from the crystal structure of EDSV fiber head

Egg drop syndrome virus (EDSV) is an avian adenovirus that causes markedly decrease in egg production, and in the quality of the eggs when it infects chickens. Until now, EDSV virus-cell interactions are poorly understood, and the cellular receptor is still unknown. In the present study, we determined the atomic structure of the fiber head of EDSV (residues 377–644) at 2.74 Å resolution. Structure comparison with the (chick embryo lethal orphan) CELO long fiber head and human adenovirus fiber heads reveals that the avian adenovirus may interact with the same attachment factor in a unique fashion. Based on the previous studies of CELO virus, we assumed that the chicken coxsackievirus and adenovirus receptor (CAR) may be the attachment factor. We then demonstrate that the chicken CAR serves as a cellular attachment factor for EDSV based on three lines of evidences. Taken together, the results presented here are helpful for further exploring the pathogenesis related to the interaction between EDSV and host cells, and may be used for vaccine development and intervention strategies against EDSV infection.

Therapeutic effects of duck Tembusu virus capsid protein fused with staphylococcal nuclease protein to target Tembusu infection in vitro

Tembusu virus (TMUV), a member of the genus flavivirus, primarily causes egg-drop syndrome in ducks and is associated with low disease mortality but high morbidity. The commercially available live vaccines for treating TMUV currently include the main WF100, HB, and FX2010-180P strains, and efficient treatment and/or preventative measures are still urgently needed. Capsid-targeted viral inactivation (CTVI) is a conceptually powerful new antiviral strategy that is based on two proteins from the capsid protein of a virus and a crucial effector molecule. The effector molecule can destroy the viral DNA/RNA or interfere with the proper folding of key viral proteins, while the capsid protein mainly plays a role in viral integration and assembly; the fusion proteins are incorporated into virions during packaging. This study aimed to explore the potential use of this strategy in duck TMUV. Our results revealed that these fusion proteins can be expressed in susceptible BHK21 cells without cytotoxicity and possess excellent Ca2+-dependent nuclease activity, and their expression is also detectable in DF-1 cells. Compared to those in the negative controls (BHK21 and BHK21/pcDNA3.1(+) cells), the numbers of viral RNA copies in TMUV-infected BHK21/Cap-SNase and BHK21/Cap-Linker-SNase cells were reduced by 48 h, and the effect of Cap-Linker-SNase was superior to that of Cap-SNase. As anticipated, these results suggest that these fusion proteins contribute to viral resistance to treatment. Thus, CTVI might be applicable for TMUV inhibition as a novel antiviral therapeutic candidate during viral infection.

Molecular evolution of Salmonella enterica subsp. enterica serovar Gallinarum biovar Gallinarum in the field

Salmonella enterica subsp. enterica serovar Gallinarum biovar Gallinarum (SG) causes fowl typhoid (FT) and substantial economic loss in Korea due to egg drop syndrome and mortality. Despite the extensive use of vaccines, FT still occurs in the field. Therefore, the emergence of more pathogenic SG or the recovered pathogenicity of a vaccine strain has been suspected. SpvB, an ADP-ribosyl transferase, is a major pathogenesis determinant, and the length of the polyproline linker (PPL) of SpvB affects pathogenic potency. SG strains accumulate pseudogenes in their genomes during host adaptation, and pseudogene profiling may provide evolutionary information. In this study, we found that the PPL length of Korean SG isolates varied from 11 to 21 prolines and was longer than that of a live vaccine strain, SG 9R (9 prolines). According to growth competition in chickens, the growth of an SG isolate with a PPL length of 17 prolines exceeded that of an SG isolate with a PPL length of 15 prolines. We investigated the pseudogenes of the field isolates, SG 9R and reference strains in GenBank by resequencing and comparative genomics. The pseudogene profiles of the field isolates were notably different from those of the foreign SG strains, and they were subdivided into 7 pseudogene subgroups. Collectively, the field isolates had gradually evolved by changing PPL length and acquiring additional pseudogenes. Thus, the characterization of PPL length and pseudogene profiling may be useful to understand the molecular evolution of SG and the epidemiology of FT.

Genetically stable reporter virus, subgenomic replicon and packaging system of duck Tembusu virus based on a reverse genetics system

Duck Tembusu virus (DTMUV) is a novel flavivirus that has caused an outbreak of severe duck egg-drop syndrome since 2010. It has spread rapidly to other avian species, causing enormous economic loss. In the present study, we generated a reporter virus expressing NanoLuc luciferase, which was stable after 10 rounds of continuous propagation without reporter gene deletion. Moreover, we generated two types of replicons driven by the T7 promoter or CMV promoter, both of which worked well in BHK21 cells. Furthermore, we developed the first packaging system for DTMUV by co-transfection into BHK21 cells of a replicon (containing mature C) and a plasmid encoding C16-prM-E, which resulted in the production of single round infectious particles (SRIPs). We also generated a packaging cell line for DTMUV to produce SRIPs. We believe that these multicomponent platform tools are important for DTMUV pathogenesis research and novel vaccine development.

Development of a Hemagglutination Inhibition Assay for Duck Tembusu Virus.

The HB strain of duck Tembusu virus (DTMUV) propagated in the brains of newborn mice was used to prepare antigens for use in the hemagglutination inhibition (HI) test. Results showed that such prepared antigens are highly specific to the serum samples derived from DTMUV-infected animals. No spurious hemagglutination reactions against serum samples specific to avian influenza virus H5, H7, H9 subtypes, Newcastle disease virus, egg drop syndrome virus, duck plague virus, and duck hepatitis A virus were observed. The HI test can detect specific antibodies in the serum samples as early as day 4 after experimental infection of ducks with DTMUV. When compared to a virus neutralization test, the sensitivity is 100%. Overall, the HI test developed is highly specific to DTMUV and can be used in clinical diagnosis of diseases and in vaccine studies to monitor the kinetics of antibody response.

RNA-Seq analysis of duck embryo fibroblast cell gene expression during the early stage of egg drop syndrome virus infection

Egg drop syndrome virus (EDSV), a member of the family Adenoviridae and an economically important pathogen with a broad host range, leads to markedly decreased egg production. However, the molecular mechanism underlying the host-EDSV interaction remains unclear. Here, we performed high-throughput RNA sequencing (RNA-Seq) to study the dynamic changes in host gene expression at 6, 12, and 24 hours post-infection in duck embryo fibroblasts (DEFs) infected with EDSV. Atotal of 441 differentially expressed genes (DEGs) were identified after EDSV infection. Gene Ontology category and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that these DEGs were associated with multiple biological functions, including signal transduction, host immunity, virus infection, cell apoptosis, cell proliferation, and pathogenicity-related and metabolic process signaling pathways. We screened and identified 12 DEGs for further examination by using qRT-PCR. The qRT-PCR and RNA-Seq results were highly consistent. This study analyzed viral infection and host immunity induced by EDSV infection from a novel perspective, and the results provide valuable information regarding the mechanisms underlying host-EDSV interactions, which will prove useful for the future development of antiviral drugs or vaccines for poultry, thus benefiting the entire poultry industry.

An avian influenza virus H6N1 outbreak in commercial layers: case report and reproduction of the disease

ABSTRACTAn outbreak of low pathogenic avian influenza (LPAI) subtype H6N1 (intravenous pathogenicity index = 0.11) infection occurred in four productive brown layer flocks on three farms in the Netherlands within a period of two months. The farms were located at a maximum distance of 4.6 km from each other. The infections were associated with egg production drops up to 74%, pale eggshells and persisting high mortality up to 3.2% per week. Three flocks were slaughtered prematurely as they were not profitable anymore. Newcastle disease, infectious bronchitis, egg drop syndrome and Mycoplasma gallisepticum infections could very likely be excluded as cause of or contributor to the condition in the field. Also, the anticoccidial drug nicarbazin, which can cause egg production drops and eggshell decolouration, was not detected in eggs from affected flocks. Furthermore, post mortem examinations revealed no lesions indicative of bacterial infection. Moreover, bacteriological analysis of hens was negative. The condition was reproduced in commercial brown layers after intratracheal inoculation with virus isolates from affected flocks. It is concluded that the LPAI H6N1 virus is very likely the only cause of the disease. An overview of main manuscripts published since 1976 describing non-H5 and non-H7 avian influenza (AI) virus infections in chickens and their biological significance is included in the present study, in which once more is shown that not only high pathogenic AI virus subtypes H5 and H7 can be detrimental to flocks of productive layers, but also non-H5 and non-H7 LPAI viruses (H6N1 virus).RESEARCH HIGHLIGHTSLPAI H6N1 can be detrimental to productive layersDetrimental effects are severe egg drop and persistent high mortalityLPAI H6N1 virus outbreak seems to be self-limiting

Sane and sound: a serologic and molecular survey for selected infectious agents in neozootic Egyptian geese (Alopochen aegyptiacus) in Germany

Aquatic birds can act as vectors and reservoir hosts for pathogens relevant for wild birds and poultry as well as human health. In this study, we address the questions (1) if the Egyptian goose (Alopochen aegyptiacus), as one of the most successful neozootic bird species in Europe, carry infectious agents that are relevant for poultry and wild birds and (2) if seasonal prevalences of these infectious agents differ from those of native geese species. In 2015 and 2016, up to 190 Egyptian geese from Western Germany were investigated serologically for antibodies (Ab) against influenza A viruses (IAV), Avian avulavirus 1 (AAvV-1), aviadenoviruses, Duck atadenovirus A (syn.: egg drop syndrome 1976 virus) (EDSV), and West Nile virus (WNV). Ab were detected against IAV in 6.1% (10/164), against AAvV-1 in 2.4% (4/165), against EDSV in 15.2% (16/105), and against aviadenoviruses in 0.86% (1/116) of the geese blood samples, respectively. None of the birds had Ab against WNV (0/84). PCR-based techniques (cloacal and/or pharyngeal swabs) were applied for the presence of IAV, AAvV-1, Mycoplasma spp., and Riemerella anatipestifer. Riemerella DNA was detected in the pharyngeal swabs with an overall prevalence of 70.3% (104/148). Neither Mycoplasma DNA nor IAV or AAvV-1 RNA could be detected in the pharynx or cloaca of the examined birds. Our study shows that Egyptian geese are frequent carriers of Riemerella anatipestifer and furthermore provides serological evidence of exposure to IAV, AAvV-1, and EDSV. It is one of very few studies on infectious agents of neozootic bird species. Comparing our results from a neozootic non-migratory goose species with published results from native migratory geese species (bean goose (Anser fabalis) and white-fronted goose (A. albifrons)) and another neozootic non-migratory goose species (Canada goose (Branta canadensis)), we found differences in the seroprevalence of viral pathogens. Native goose species show higher seroprevalences of IAV and AAvV-1, whereas neozootic non-migratory geese reveal higher seroprevalences for EDSV. The findings are discussed in the frame of seasonal variations in selected infectious agents, differences in sampling periods, and contrasting movement ecology of the different geese species.

Potential and safety tests of egg drop syndrome candidate vaccine from Medan isolate, Indonesia

Aim:The study was aimed to prepare and examine the potential and safety concerns of egg drop syndrome (EDS) vaccine candidate seed. The potential and safety trials of EDS Medan isolate vaccine need to be done before commercial scale of EDS vaccines are made.Materials and Methods:The safety test of EDS candidate vaccine was tested on 4-week-old specified pathogen-free chickens in an experimentally isolated enclosure.Results:The result of the safety test obtained 27.3 hemagglutination inhibition (HI) unit of geometric mean titer antibody post-vaccination. However, the potency test of the EDS candidate vaccine was conducted on 17-week-old laying hens. Test results of the EDS potency vaccine in layer obtained antibody titer increased in every week of blood taking with average titer of antibody: Before vaccinated was 22.9 HI unit, 1 week after vaccination was 23.7 HI unit, 2 weeks post-vaccination was 25 HI unit, and 3 weeks after vaccination was 27.3 HI units. In contrast, decreasing trend was observed in control group (unvaccinated chicken).Conclusion:Serologically, the seed vaccine of EDS virus isolates from Medan was able to produce protective antibody titers starting in the 2nd and 3rd weeks post-vaccination.

Screening and identification of B-cell epitopes within envelope protein of tembusu virus

BackgroundTembusu virus is a newly emerging flavivirus that caused egg-drop syndrome in ducks in China. TMUV envelope protein is a major structural protein locates at the surface of tembusu virus particle. During tembusu virus infection, envelope protein plays a pivotal role in induction of neutralizing antibody. However, B cell epitopes within envelope protein have not been well studied.MethodA series of 13 peptides derived from E protein of tembusu virus were synthesized and screened by Dot blot with tembusu virus-positive duck serum. Potential B-cell epitopes were respectively fused with GST tag and expressed in E. coli. The immunogenicity and protective efficiency of epitopes were assessed in ducks.ResultsDot blot assay identified the peptides P21 (amino acids 301–329), P23 (amino acids 369–387), P27 (amino acids 464–471) and P28 (amino acids 482–496) as potential B-cell epitopes within the envelope protein of tembusu virus. Immunization of prokaryotically expressed epitopes elicited specific antibodies in ducks and the specific antibody elicited by P21, P27 and P28 could neutralized tembusu virus. In addition, protective test suggested that P21 and P27 could completely protect immunized ducks from TMUV challenge.ConclusionFour potential B cell epiotpes within tembusu virus envelope protein were identified and analyzed in vitro and in vivo. It was demonstrated that two of them (P21 and P27) could elicit neutralizing antibodies in ducks and offer complete protection against tembusu virus challenge. This findings will contribute to the development of epitope vaccine for tembusu virus prevention.

Molecular analysis and serological survey of Tembusu virus infection in Zhejiang, China, 2010-2016.

Tembusu virus (TMUV) is an important pathogen that causes acute egg drop syndrome in poultry. To investigate the epidemiological status of Tembusu virus in Zhejiang province, we collected clinical samples and sera from the local area from 2010 to 2016. A total of 41 out of the 88 collected tissue samples were identified as TMUV-infected by RT-PCR and were confirmed by sequencing. Six TMUV strains were isolated from TMUV-positive samples, and their complete genome sequences were determined. In addition, 19 E gene sequences amplified from RT-PCR-positive samples were determined. Sequence identity values among the 19 E genes and reference E sequences ranged from 96.8% to 100.0%, and they ranged from 97.3% to 99.9% when comparing the six genome sequences and references. Nineteen sites with amino acid mutations were identified in the E protein of nineteen strains, and these were at positions that are usually conserved in other TMUV strains. Antibodies to TMUV in serum samples were detected by indirect ELISA using recombinant EDIII (domain III of the E protein) as the antigen. The results showed that TMUV-specific antibodies were widely present in duck populations, with positive rates of 17.38%, 21.99%, 26.68%, and 17.79% in 2013, 2014, 2015 and 2016, respectively. The data from this study provide a good understanding of the epidemiology of TMUV infections in Zhejiang, China.

Comparative Transcriptomic Analysis of Immune-Related Gene Expression in Duck Embryo Fibroblasts Following Duck Tembusu Virus Infection.

Duck is a major waterfowl species in China, providing high-economic benefit with a population of up to 20–30 billion per year. Ducks are commonly affected by severe diseases, including egg-drop syndrome caused by duck Tembusu virus (DTMUV). The immune mechanisms against DTMUV invasion and infection remain poorly understood. In this study, duck embryo fibroblasts (DEFs) were infected with DTMUV and harvested at 12 and 24 h post-infection (hpi), and their genomes were sequenced. In total, 911 (764 upregulated and 147 downregulated genes) and 3008 (1791 upregulated and 1217 downregulated) differentially expressed genes (DEGs) were identified at 12 and 24 hpi, respectively. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that DEGs were considerably enriched in immune-relevant pathways, including Toll-like receptor signaling pathway, Cytosolic DNA-sensing pathway, RIG-I-like receptor signaling pathway, Chemokine signaling pathway, NOD-like receptor signaling pathway, and Hematopoietic cell lineage at both time points. The key DEGs in immune system included those of the cytokines (IFN α2, IL-6, IL-8L, IL-12B, CCR7, CCL19, and CCL20), transcription factors or signaling molecules (IRF7, NF-κB, STAT1, TMEM173, and TNFAIP3), pattern recognition receptors (RIG-I and MDA5), and antigen-presenting proteins (CD44 and CD70). This suggests DTMUV infection induces strong proinflammatory/antiviral effects with enormous production of cytokines. However, these cytokines could not protect DEFs against viral attack. Our data revealed valuable transcriptional information regarding DTMUV-infected DEFs, thereby broadening our understanding of the immune response against DTMUV infection; this information might contribute in developing strategies for controlling the prevalence of DTMUV infection.

Novel duck hepatitis A virus type 1 isolates from adult ducks showing egg drop syndrome

Generally, duck hepatitis A virus type 1 (DHAV-1) only infects young ducklings. Since December 2016, severe outbreaks of duck viral infection with egg drop, feed consumption decline, and ovary-oviduct disease have occurred in some laying duck flocks in Shandong Province of China. DHAV-1 isolated from the affected ducks was confirmed as the causative pathogen of the egg drop. Compared with other DHAV-1 strains, the novel isolate has three special amino acid mutation points in the most variable regions at the C-terminus of VP1. The experimental infection in laying ducks indicated that successful immunization with DHAV-1 vaccine could protect laying duck from infection. To the best of our knowledge, this is the first reported incidence of a severe duck disease outbreak involving egg drop syndrome caused by DHAV-1.

Autophagy Benefits the Replication of Egg Drop Syndrome Virus in Duck Embryo Fibroblasts.

Egg drop syndrome virus (EDSV) is an economically important pathogen with a broad host range, and it causes disease that leads to markedly decreased egg production. Although EDSV is known to induce apoptosis in duck embryo fibroblasts (DEFs), the interaction between EDSV and its host needs to be further researched. Here, we provide the first evidence that EDSV infection triggers autophagy in DEFs through increases in autophagosome-like double-membrane vesicles, the conversion of LC3-I to LC3-II, and LC3 colocalization with viral hexon proteins. Conversely, P62/SQSTM1 degradation, LC3-II turnover, and colocalization of LAMP and LC3 confirmed that EDSV infection triggers complete autophagy. Furthermore, we demonstrated that inhibition of autophagy by chloroquine (CQ) and 3-methyladenine (3MA) or RNA interference targeting ATG-7 decreased the yield of EDSV progeny. In contrast, induction of autophagy by rapamycin increased the EDSV progeny yield. In addition, we preliminarily demonstrated that the class I phosphoinositide 3-kinase (PI3K)/Akt/mTOR pathway contributes to autophagic induction following EDSV infection. Altogether, these finding lead us to conclude that EDSV infection induces autophagy, which benefits its own replication in host cells. These findings provide novel insights into EDSV–host interactions.