Pathogenesis of Korean SapelovirusA in piglets and chicks

Sapelovirus A (SV-A), formerly known as porcine sapelovirus as a member of a new genus Sapelovirus, is known to cause enteritis, pneumonia, polioencephalomyelitis and reproductive disorders in pigs. We have recently identified α2,3-linked sialic acid on GD1a ganglioside as a functional SV-A receptor rich in the cells of pigs and chickens. However, the role of GD1a in viral pathogenesis remains elusive. Here, we demonstrated that a Korean SV-A strain could induce diarrhoea and intestinal pathology in piglets but not in chicks. Moreover, this Korean SV-A strain had mild extra-intestinal tropisms appearing as mild, non-suppurative myelitis, encephalitis and pneumonia in piglets, but not in chicks. By real-time reverse transcription (RT) PCR, higher viral RNA levels were detected in faecal samples than in sera or extra-intestinal organs from virus-inoculated piglets. Immunohistochemistry confirmed that high viral antigens were detected in the epithelial cells of intestines from virus-inoculated piglets but not from chicks. This Korean SV-A strain could bind the cultured cell lines originated from various species, but replication occurred only in cells of porcine origin. These data indicated that this Korean SV-A strain could replicate and induce pathology in piglets but not in chicks, suggesting that additional porcine-specific factors are required for virus entry and replication. In addition, this Korean SV-A strain is enteropathogenic, but could spread to the bloodstream from the gut and disseminate to extra-intestinal organs and tissues. These results will contribute to our understanding of SV-A pathogenesis so that efficient anti-sapelovirus drugs and vaccines could be developed in the future.

Distribution and genetic characterization of Enterovirus G and Sapelovirus A in six Spanish swine herds

The prevalence of Enterovirus G (EV-G) and Sapelovirus A (PSV-1) was investigated in Spanish swine herds by means of cross-sectional studies. Faecal samples from clinically healthy pigs were collected from six farms, and analysed by RT-PCR. The results indicated a high prevalence of EV-G detected in nearly all the animals older than 3 weeks of age. Otherwise, PSV-1 was only detected in 3-week-old piglets from one of the farms. Genetic analyses performed in the VP1 region of the EV-G indicated circulation of diverse strains in the same farm, related to genotypes G1, G2, G3, G4, G6, G9, G12, G13 and G14. Moreover, co-infection of several PSV-1 variants in the same animal was evident, typical of viral quasispecies. Evolutionary pressure analysis indicated that microevolution of PSV-1 seems to be driven by negative selection. This study gives further insights in the epidemiology of EV-G and PSV-1.

Novel picornavirus in domestic rabbits (Oryctolagus cuniculus var. domestica)

Picornaviruses (family Picornaviridae) are small, non-enveloped viruses with positive sense, single-stranded RNA genomes. The numbers of the novel picornavirus species and genera are continuously increasing. Picornaviruses infect numerous vertebrate species from fish to mammals, but have not been identified in a member of the Lagomorpha order (pikas, hares and rabbits). In this study, a novel picornavirus was identified in 16 (28.6%) out of 56 faecal samples collected from clinically healthy rabbits (Oryctolagus cuniculus var. domestica) in two (one commercial and one family farms) of four rabbit farms in Hungary. The 8364 nucleotide (2486 amino acid) long complete genome sequence of strain Rabbit01/2013/HUN (KT325852) has typical picornavirus genome organization with type-V IRES at the 5'UTR, encodes a leader (L) and a single 2A(H-box/NC) proteins, contains a hepatitis-A-virus-like cis-acting replication element (CRE) in the 2A, but it does not contain the sequence forming a "barbell-like" secondary structure in the 3'UTR. Rabbit01/2013/HUN has 52.9%, 52% and 57.2% amino acid identity to corresponding proteins of species Aichivirus A (genus Kobuvirus): to murine Kobuvirus (JF755427) in P1, to canine Kobuvirus (JN387133) in P2 and to feline Kobuvirus (KF831027) in P3, respectively. The sequence and phylogenetic analysis indicated that Rabbit01/2013/HUN represents a novel picornavirus species possibly in genus Kobuvirus. This is the first report of detection of picornavirus in rabbit. Further study is needed to clarify whether this novel picornavirus plays a part in any diseases in domestic or wild rabbits.

[Development and evaluation of an inactivated bivalent vaccine against duck viral hepatitis]

The rapid mutation and widely spread of duck hepatitis A virus (DHAV) lead to the vast economic loss of the duck industry. To prepare and evaluate bivalent inactivated vaccine laboratory products of DHAV, 6 strains were screened from 201 DHAV-1 strains and 38 DHAV-3 strains by using serotype epidemiological analysis in most of the duck factory. Vaccine candidate strains were selected by ELD50 and LD50 tests in the 6 strains. Continuously passaged, the 5th passaged duck embryos bodies grinding fluid was selected as vaccine virus seeds. The virus seeds were treated with formaldehyde and water in oil in water (W/O/W) emulsions, making into three batches of two bivalent inactivated vaccine laboratory products. The safety test, antibody neutralization test, challenged protection and cross immune protection experiment suggested that the vaccines possessed good safety, and neutralizing antibodies were detected at 7th day and the challenged protection rate reached 90% to 100% at the 14th and 21st day. Moreover, immune duration of ducklings lasted more than five weeks. However, cross-immunity protection experiments with DHAV-SH and DHAV-FS only had 20%-30%. The two bivalent inactivated vaccine laboratory products of duck viral hepatitis were effective and reliable, providing a new method as well as a new product for DHAV prevention and control.

Genetic characterization of porcine kobuvirus variants identified from healthy piglets in China

In this study, two porcine kobuvirus strains, JS-01-CHN and JS-02a-CHN were detected from piglets with diarrhea and asymptomatic, respectively. The sequences of the two strains were analyzed using a bioinformatics software package. The full-length genome of JS-02a-CHN, was detected in healthy piglets was 8121 nucleotides (nt) long excluding the poly(A) tail. There was a 30 amino acid deletion in the 2B-coding region of JS-02a-CHN. We are the first to report a 30 amino acid deletion in porcine kobuvirus from asymptomatic piglets, indicating that porcine kobuvirus may have evolved differently based on geography and host differences. Fecal samples were obtained from pigs with diarrhea (n=91) and healthy (n=126) pigs and analyzed using RT-PCR. Of these, 64.8% (59/91) of diarrheic piglets and 19.8% (25/126) of healthy piglets were positive for PKV using VP1 specific primers. Twenty-eight (28) virus positive samples were randomly selected and the VP1 gene was analyzed. Phylogenetic analysis indicated that the 15 strains isolated from pigs with diarrhea clustered into different branches, while the VP1 sequences from clinically healthy pigs clustered into a single large group. These results indicate that the VP1 gene is diverse in pigs with diarrhea but conserved in healthy pigs in the Jiangsu Province.

Antibodies to VP1 of swine pasivirus in humans without evidence of transmission from a pig source

BACKGROUND

Swine pasivirus (SPaV1) is a recently described enteric virus close to human parechoviruses and highly prevalent in pigs. Antibodies to Escherichia coli-expressed VP1 of SpaV1 have been found in a majority of humans in China.

OBJECTIVES

The objectives were to estimate the antibody prevalence in a European country, to test if exposure to the virus was linked to pig products and if this exposure was a risk factor for the development of diabetes type 1.

STUDY DESIGN

An ELISA test was developed and used to screen 842 healthy subjects with known exposure to pig products, 39 patients with diabetes type 1 and 20 controls.

RESULTS

We identified a high seroprevalence (15.6%) reacting to VP1 of SPaV1 among healthy human subjects. Analysis of risk factors argues against cross-species transmission from pigs as the source of infection. Data also indicate that the presence of SPaV1 VP1-binding antibodies is not associated with diabetes type 1 in humans.

CONCLUSION

Our results suggest that the seroreactivity frequently found in humans against SpaV1 is due to cross-reactivity with related antigen, perhaps a picornavirus, and that SpaV1 is not a zoonotic virus.

Bovine rhinitis viruses are common in U.S. cattle with bovine respiratory disease

Bovine rhinitis viruses (BRV) are established etiological agents of bovine respiratory disease complex however little research into their epidemiology and ecology has been published for several decades. In the U.S., only bovine rhinitis A virus 1 (BRAV1) has been identified while bovine rhinitis A virus 2 (BRAV2) and bovine rhinitis B virus (BRBV) were previously only identified in England and Japan, respectively. Metagenomic sequencing of a nasal swab from a bovine respiratory disease (BRD) diagnostic submission from Kansas identified contigs with approximately 90% nucleotide similarity to BRAV2 and BRBV. A combination of de novo and templated assemblies using reference genomes yielded near complete BRAV2 and BRBV genomes. The near complete genome of bovine rhinitis A virus 1 (BRAV1) was also determined from a historical isolate to enable further molecular epidemiological studies. A 5’-nuclease reverse transcription PCR assay targeting the 3D polymerase gene was designed and used to screen 204 archived BRD clinical specimens. Thirteen (6.4%) were positive. Metagenomic sequencing of six positive samples identified mixed BRAV1/BRAV2, BRAV1/BRBV and BRAV2/BRBV infections for five samples. One sample showed infection only with BRAV1. Seroprevalence studies using a cell culture adapted BRBV found immunofluorescence assay-reactive antibodies were common in the herds analyzed. Altogether, these results demonstrate that BRV infections are common in cattle with respiratory disease and that BRAV1, BRAV2 and BRBV co-circulate in U.S. cattle and have high similarity to viruses isolated more than 30 years ago from diverse locations.

Identification and complete genome analysis of kobuvirus in faecal samples of European roller (Coracias garrulus): for the first time in a bird

The genus Kobuvirus (Picornaviridae) consists of three species, Aichivirus A (e.g., Aichi virus, which infects humans), Aichivirus B and Aichivirus C. Kobuvirus have not been detected in non-mammal species including birds. In this study, a novel kobuvirus was identified in 3 (17 %) out of 18 faecal samples collected from European rollers (Coracias garrulus) in Hungary. The complete genome sequence of strain SZAL6-KoV/2011/HUN (KJ934637), which was determined using a novel 5'/3' RACE method (dsRNA-RACE) involving a double-stranded (ds)RNA intermediate, has a type-V IRES at the 5' end and a cis-acting element (CRE) in the 3C gene and encodes L and 2A(H-box/NC) proteins, but it does not contain the sequence forming a "barbell-like" secondary RNA structure in the 3'UTR. SZAL6-KoV/2011/HUN has 72 %, 73 %, and 81 % amino acid sequence identity to the P1, P2, and P3 protein, respectively, of Aichi virus. Evolutionary analysis showed that SZAL6-KoV/2011/HUN shares a common ancestor with other kobuviruses but belongs to a more ancient lineage in the species Aichivirus A. Investigation of the known kobuviruses in different animals and discovery of novel kobuviruses in potential host species helps to clarify the evolutionary connection and zoonotic potential of kobuviruses.

Isolation and molecular characterization of a novel picornavirus from baitfish in the USA

During both regulatory and routine surveillance sampling of baitfish from the states of Illinois, Minnesota, Montana, and Wisconsin, USA, isolates (n = 20) of a previously unknown picornavirus were obtained from kidney/spleen or entire viscera of fathead minnows (Pimephales promelas) and brassy minnows (Hybognathus hankinsoni). Following the appearance of a diffuse cytopathic effect, examination of cell culture supernatant by negative contrast electron microscopy revealed the presence of small, round virus particles (∼ 30-32 nm), with picornavirus-like morphology. Amplification and sequence analysis of viral RNA identified the agent as a novel member of the Picornaviridae family, tentatively named fathead minnow picornavirus (FHMPV). The full FHMPV genome consisted of 7834 nucleotides. Phylogenetic analysis based on 491 amino acid residues of the 3D gene showed 98.6% to 100% identity among the 20 isolates of FHMPV compared in this study while only 49.5% identity with its nearest neighbor, the bluegill picornavirus (BGPV) isolated from bluegill (Lepomis macrochirus). Based on complete polyprotein analysis, the FHMPV shared 58% (P1), 33% (P2) and 43% (P3) amino acid identities with BGPV and shared less than 40% amino acid identity with all other picornaviruses. Hence, we propose the creation of a new genus (Piscevirus) within the Picornaviridae family. The impact of FHMPV on the health of fish populations is unknown at present.

Soft plastron, soft carapace with skeletal abnormality in juvenile tortoises. Histopathology and isolation of a novel picornavirus from Testudo graeca and Geochelone elegans

OBJECTIVE

A disease is described in juvenile tortoises (Testudo graeca and Geochelone elegans) consisting mainly of a soft carapace, soft plastron and deformed skeleton. The aim of this study was to determine histopathological lesions and the biological properties of the isolated viruses.

MATERIALS AND METHODS

Clinical signs and gross pathology were determined on diseased and healthy appearing tortoises. Paraffin sections were stained with HE, PAS and Prussian Blue and histologically examined. Terrapene heart (TH-1) cell cultures served for virus isolations from 64 tissues and 104 swabs. One isolate (isolate 1243/37 tongue) was used in neutralization tests on 19 sera.

RESULTS

Retarded growth and increasingly soft plastron and carapace were the prominent signs in diseased tortoises. Pathological lesions consisted of dilated urinary sac, enlarged kidneys and livers. Histopathologically, hepatic hemosiderosis, hypoplastic anaemia, congestive glomerulonephrosis and osteodystrophy were seen. A novel vi- rus ("virus X") was isolated from 64 organs and 79 of 104 swabs. The isolated viruses were identified as a novel chelonid picornavirus based on cytopathic effect, resistance to chloroform and stability at low pH. Co-cultivation with 5-iodo-2'-deoxyuridine and actinomycin D did not reduce virus titres. Electron microscopically, round, non-enveloped particles (25-30 nm) were detected. Neutralizing antibodies to the isolate 1243/37tongue were present in 17 of 19 sera from seven species of tortoises.

CONCLUSION AND CLINICAL RELEVANCE

Nephropathy, osteodystrophy and virus isolations suggest a viral aetiology. Metabolic bone disease is the major differential diagnosis. Further investigations in vivo are needed to evaluate the likely effects of the picornavirus on tortoises.

Prevalence and genetic diversity of bovine kobuvirus in China

A total of 166 faecal specimens from diarrheic cattle were collected in China for detection of bovine kobuvirus (BKV) by reverse transcription PCR (RT-PCR) targeting the region a portion of the 3D nonstructural protein, with an amplicon size of 631 bp. The RNA corresponding to the BKV 3D region was detected in 34.9 % of faecal samples (58/166) in four major dairy-cattle-production areas in China, and sequence analysis based on the partial 3D sequences (35/58) indicated that the Chinese BKVs shared 88.9-96.2 % nucleotide sequence identity to BKV reference strains. Further phylogenetic analysis based on the complete VP1-encoding sequences (17/35) revealed that the Chinese BKVs shared 81-83.4 % nucleotide sequence identity to the U-1 strain, and these Chinese BKV strains, together with the U-1 strain, are apparently divided into four lineages, representing four genotypes of BKV, designated as A, B, C and D. Our results show that BKV infection is widely distributed, with high genetic diversity in China.

Molecular detection and genetic characterization of kobuviruses and astroviruses in asymptomatic local pigs in East Africa

In this study, swine fecal specimens (n = 251) collected from nursing and weaned piglets raised under smallholder production systems were screened for the presence of kobuviruses by RT-PCR. Porcine kobuviruses were detected in 13.1 % (33/251) of the samples. We demonstrated that porcine kobuvirus infections exist in indigenous pigs in Kenya and Uganda and that the prevalence was higher in young piglets than older pigs: nursing piglets (15 %), post-weaning (3-month-old) pigs (17 %), 4-month-old pigs (10 %). Genetic analysis of the partial RNA-dependent RNA polymerase (RdRp) region (690 nt) revealed that kobuviruses circulating in East Africa are diverse, sharing nucleotide sequence identities ranging from 89.7 to 99.1 % and 88 to 92.3 % among them and with known porcine kobuviruses, respectively. The nucleotide sequence identities between our kobuvirus strains and those of human, bovine and canine kobuviruses were 69.4-70.7 %, 73.1-74.4 % and 67-70.7 %, respectively. Additionally, upon sequencing selected samples that showed consistent 720-bp RT-PCR bands while using the same primer set, we detected porcine astroviruses in our samples belonging to type 2 and type 3 mamastroviruses. To our knowledge, this study reports the first detection and molecular analysis of both porcine kobuviruses and astroviruses in an African region. Further studies are required to determine the role of these viruses in gastrointestinal infections of pigs in this region and to determine the genetic diversity of the circulating strains to develop accurate diagnostic tools and implement appropriate control strategies.

Effect of age on the pathogenesis of DHV-1 in Pekin ducks and on the innate immune responses of ducks to infection

Duck hepatitis virus (DHV) affects 1-week-old but not 3-week-old ducks, and it causes a more severe disease in the younger ducks. These differences may be partially due to the host response to DHV infection. In order to understand this difference, we characterized the pathobiology of and innate immune response to DHV infection in 1-day-old (1D) and 3-week-old (3 W) ducks. Viral RNA was detected in duck livers at 24, 36 and 72 h after inoculation with DHV at a dose of 10(3) LD50. Virus-induced pathology ranged from no clinical signs to severe disease and death, and it was more severe in the 1D ducks. Infection with DHV induced up-regulation of gene expression of Toll-like receptor (TLR)-7, TLR3, retinoic-acid-inducible gene I (RIG-I), melanoma differentiation-associated gene 5 (MDA-5), interleukin (IL)-6, interferon (IFN)-α, interferon-induced transmembrane protein 1 (IFITM1), interferon-stimulated gene 12 (ISG12), and 2'-5' oligoadenylate synthetase-like gene (OASL) in the livers of 3 W ducks. Of these, IL-6, OASL and ISG12 mRNA levels were more than 100-fold higher in infected 3 W ducks than in mock-infected ducks of the same age. These genes were induced much less in infected 1D ducklings. We present evidence that a lower level of viral replication in the hepatocytes of 3 W ducks, whose basal level of cytokines is higher than that in 1D ducklings, may be related to the strong innate immunity induced. From our data, we conclude that duck age plays an important role in the pathogenicity of and innate immune responses to DHV.

[Sequence analysis of VP1 gene of the duck hepatitis A virus type 3 strains isolated from Shandong Province of China in 2012]

To reveal the genetic variation of the viral protein 1 (VP1) gene of the duck hepatitis A virus type 3 (DHAV-3), the VP1 gene of 13 virulent DHAV-3 strains isolated from Shandong province of China in 2012 were amplified by RT-PCR, sequenced and analyzed. The results showed that all the VP1 genes of the 13 isolates contained 720 nucleotides encoding 240 amino acids, and shared with nucleotide identities of 94. 6%-99.9% and amino acid identities of 95.0%-100%. The nucleotide and amino acid sequence homologies between the 13 DHAV-3 isolates and other 31 DHAV-3 reference strains were 92.5%-100% and 90. 8%-100%, respectively. Phylogenetic analysis showed that the VP1 gene of DHAV-3 had distinct geographical characteristics. Distribution of genotypes of the 44 DHAV-3 strains was as follows: except the vaccine strain B63, all the other Chinese isolates belonged to genotype I (GI), Vietnamese wild isolates mainly belonged to subtype 1 (S1) of genotype II (GII), and all Korean isolates belonged to subtype 2 (S2) of GII.

Development and application of a reverse transcription loop-mediated isothermal amplification method for rapid detection of Duck hepatitis A virus type 1

We developed and evaluated a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detecting Duck hepatitis A virus type 1 (DHAV-1). The amplification could be finished in 1 h under isothermal conditions at 63 °C by employing a set of four primers targeting the 2C gene of DHAV-1. The RT-LAMP assay showed higher sensitivity than the RT-PCR with a detection limit of 0.1 ELD(50) 0.1 ml(-1) of DHAV-1. The RT-LAMP assay was highly specific; no cross-reactivity was observed from the samples of other related viruses, bacteria, allantoic fluid of normal chicken embryos, or the livers of uninfected ducks. Thirty clinical samples were subjected to detection by RT-LAMP, RT-PCR, and virus isolation, which obtained completely consistent, positive results. As a simple, rapid, and accurate detection method, this RT-LAMP assay has important potential applications in the clinical diagnosis of DHAV-1.

[Research advances in the characteristics and detection of Kobuviruses]

In the present work, we reviewed the discovery, epidemiology, molecular biology and detection of Kobuvirus. Future fields of research were also discussed.

[Overview on duck virus hepatitis A]

This article describes the nomenclature, history and genetic evolution of duck hepatitis A virus, and updates the epidemiology, clinical symptom and surveillances of duck virus hepatitis A. It also summarizes the present status and progress of duck virus hepatitis A and illustrated the necessity and urgency of its research, which provides rationale for the control of duck hepatitis A virus disease in China.

Identification of a novel feline picornavirus from the domestic cat

While picornaviruses are known to infect different animals, their existence in the domestic cat was unknown. We describe the discovery of a novel feline picornavirus (FePV) from stray cats in Hong Kong. From samples from 662 cats, FePV was detected in fecal samples from 14 cats and urine samples from 2 cats by reverse transcription-PCR (RT-PCR). Analysis of five FePV genomes revealed a distinct phylogenetic position and genomic features, with low sequence homologies to known picornaviruses especially in leader and 2A proteins. Among the viruses that belong to the closely related bat picornavirus groups 1 to 3 and the genus Sapelovirus, G+C content and sequence analysis of P1, P2, and P3 regions showed that FePV is most closely related to bat picornavirus group 3. However, FePV possessed other distinct features, including a putative type IV internal ribosome entry site/segment (IRES) instead of type I IRES in bat picornavirus group 3, protein cleavage sites, and H-D-C catalytic triad in 3C(pro) different from those in sapeloviruses and bat picornaviruses, and the shortest leader protein among known picornaviruses. These results suggest that FePV may belong to a new genus in the family Picornaviridae. Western blot analysis using recombinant FePV VP1 polypeptide showed a high seroprevalence of 33.6% for IgG among the plasma samples from 232 cats tested. IgM was also detected in three cats positive for FePV in fecal samples, supporting recent infection in these cats. Further studies are important to understand the pathogenicity, epidemiology, and genetic evolution of FePV in these common pet animals.

Viruses in diarrhoeic dogs include novel kobuviruses and sapoviruses

The close interactions of dogs with humans and surrounding wildlife provide frequent opportunities for cross-species virus transmissions. In order to initiate an unbiased characterization of the eukaryotic viruses in the gut of dogs, this study used deep sequencing of partially purified viral capsid-protected nucleic acids from the faeces of 18 diarrhoeic dogs. Known canine parvoviruses, coronaviruses and rotaviruses were identified, and the genomes of the first reported canine kobuvirus and sapovirus were characterized. Canine kobuvirus, the first sequenced canine picornavirus and the closest genetic relative of the diarrhoea-causing human Aichi virus, was detected at high frequency in the faeces of both healthy and diarrhoeic dogs. Canine sapovirus constituted a novel genogroup within the genus Sapovirus, a group of viruses also associated with human and animal diarrhoea. These results highlight the high frequency of new virus detection possible even in extensively studied animal species using metagenomics approaches, and provide viral genomes for further disease-association studies.

Real-time RT-PCR for the detection and quantitative analysis of equine rhinitis viruses

REASONS FOR PERFORMING STUDY

Equine rhinitis viruses (ERV) cause respiratory disease and loss of performance in horses. It has been suggested that the economic significance of these viruses may have been underestimated due to insensitive methods of detection.

OBJECTIVES

To develop a sensitive, rapid, real-time RT-PCR (rRT-PCR) assay suitable for the routine diagnosis and epidemiological surveillance of the A and B variants of ERV.

METHODS

TaqMan primer probe sets for ERAV and ERBV were designed from conserved regions of the 5' UTR of the ERV genome. Over 400 samples from both clinically affected and asymptomatic horses were employed for validation of the assays. ERAV samples positive by rRT-PCR were verified by virus isolation and ERBV positive samples were verified by rRT-PCR using a different set of primers.

RESULTS

The detection limit of the rRT-PCR for both viruses was 10-100 genome copies. Of 250 archival nasal swabs submitted for diagnostic testing over a 7 year period, 29 were ERAV positive and 3 were ERBV positive with an average incidence rate per year of 10 and 1.5%, respectively. There was evidence of co-circulation of ERAV and ERBV with equine influenza virus (EIV). Of 100 post race urine samples tested, 29 were ERAV positive by rRT-PCR. Partial sequencing of 2 ERBV positive samples demonstrated that one was 100% identical to ERBV1 from a 270 bp sequence and the other was more closely related to ERBV2 than ERBV1 (95% compared to 90% nucleotide identity in 178 bp).

CONCLUSIONS

The rRT-PCR assays described here are specific and more sensitive than virus isolation. They have good reproducibility and are suitable for the routine diagnosis of ERAV and ERBV.

POTENTIAL RELEVANCE

These assays should be useful for investigating the temporal association between clinical signs and rhinitis virus shedding.

[Construction of infectious molecular clone of duck hepatitis virus type 1 CL strain]

OBJECTIVE

To construct an infectious clone for studying functions of duck hepatitis virus (DHV) typel genome by reverse genetic technique.

METHODS

Three fidelity DNA fragments covering the full genome of DHV type 1 CL strain were amplified by RT-PCR, and inserted into pBR322 vector, resulting in the full-length cDNA clone BR-CL. The in vitro-transcribed RNA from BR-CL was transfected into duck embryo renal cells and the rescued virus was identified using RT-PCR, indirect immunofluorescence assay and colloidal gold immunoelectron microscopy after six generations. After inoculating the rescued virus into SPF chick embryos, embryo death and pathological changes were observed.

RESULTS

The results of RT-PCR, indirect immunofluorescence assay and immunoelectron microscope showed that infectious virus was rescued. After inoculating into SPF chick embryos, the rescued virus was able to kill embryos with pathogenic changes.

CONCLUSION

This is the first report on generation of infectious cDNA clone of DHV, which provides a valuable platform for further research on functions of DHV genome.