Molecular characterization of Brazilian avian pneumovirus isolates: comparison between immunochemiluminescent Southern blot and nested PCR

Integrative Transcriptomics and Proteomics Analysis Provide a Deep Insight Into Bovine Viral Diarrhea Virus-Host Interactions During BVDV Infection

Bovine viral diarrhea virus (BVDV) is the causative agent of bovine viral diarrhea-mucosal disease (BVD-MD), an important viral disease in cattle that is responsible for extensive economic losses to the cattle industry worldwide. Currently, several underlying mechanisms involved in viral replication, pathogenesis, and evading host innate immunity of BVDV remain to be elucidated, particularly during the early stage of virus infection. To further explore the mechanisms of BVDV-host interactions, the transcriptomics and proteomics profiles of BVDV-infected MDBK cells were sequenced using RNA-seq and iTRAQ techniques, respectively, and followed by an integrative analysis. Compared with mock-infected MDBK cells, a total of 665 differentially expressed genes (DEGs) (391 down-regulated, 274 up-regulated) and 725 differentially expressed proteins (DEPs) (461 down-regulated, 264 up-regulated) were identified. Among these, several DEGs and DEPs were further verified using quantitative RT-PCR and western blot. Following gene ontology (GO) annotation and KEGG enrichment analysis, we determined that these DEGs and DEPs were significantly enriched in multiple important cellular signaling pathways including NOD-like receptor, Toll-like receptor, TNF, NF-κB, MAPK, cAMP, lysosome, protein processing in endoplasmic reticulum, lipid metabolism, and apoptosis signaling pathways. Significantly, the down-regulated DEGs and DEPs were predominantly associated with apoptosis-regulated elements, inflammatory factors, and antiviral elements that were involved in innate immunity, thus, indicating that BVDV could inhibit apoptosis and the expression of host antiviral genes to facilitate viral replication. Meanwhile, up-regulated DEGs and DEPs were primarily involved in metabolism and autophagy signaling pathways, indicating that BVDV could utilize the host metabolic resources and cell autophagy to promote replication. However, the potential mechanisms BVDV-host interactions required further experimental validation. Our data provide an overview of changes in transcriptomics and proteomics profiles of BVDV-infected MDBK cells, thus, providing an important basis for further exploring the mechanisms of BVDV-host interactions.

A survey of jaagsiekte sheep retrovirus (JSRV) infection in sheep in the three northeastern provinces of China

Ovine pulmonary adenomatosis (OPA) is caused by jaagsiekte sheep retrovirus (JSRV) and is a chronic, progressive, and infectious neoplastic lung disease in sheep, which causes significant economic losses to the sheep industry. Neither a vaccine nor serological diagnostic methods to detect OPA are available. We performed a JSRV infection survey in sheep using blood samples (n = 1,372) collected in the three northeastern provinces of China (i.e., Inner Mongolia, Heilongjiang, and Jilin) to determine JSRV infection status in sheep herds using a real-time PCR assay targeting the gag gene of JSRV. The ovine endogenous retrovirus sequence was successfully amplified in all sheep samples tested (296 from the Inner Mongolia Autonomous Region, 255 from Jilin province, and 821 from Heilongjiang province). Subsequently, we attempted to distinguish exogenous JSRV (exJSRV) and endogenous JSRV (enJSRV) infections in these JSRV-positive samples using a combination assay that identifies a ScaI restriction site in an amplified 229-bp fragment of the gag gene of JSRV and a "LHMKYXXM" motif in the cytoplasmic tail region of the JSRV envelope protein. The ScaI restriction site is present in all known oncogenic JSRVs but absent in ovine endogenous retroviruses, while the "LHMKYXXM" motif is in all known exJSRVs but not in enJSRVs. Interestingly, one JSRV strain (HH13) from Heilongjiang province contained the "LHMKYXXM" motif but not the ScaI enzyme site. Phylogenetic analysis showed that strain HH13 was closely related to strain enJSRV-21 reported in the USA, indicating that HH13 could be an exogenous virus. Our results provide valuable information for further research on the genetic evolution and pathogenesis of JSRV.

Molecular detection and isolation of avian metapneumovirus in Mexico

We conducted a longitudinal study to detect and isolate avian metapneumovirus (aMPV) in two highly productive poultry areas in Mexico. A total of 968 breeder hens and pullets from 2 to 73 weeks of age were analysed. Serology was performed to detect aMPV antibodies and 105 samples of tracheal tissue were collected, pooled by age, and used for attempted virus isolation and aMPV nested reverse transcriptase-polymerase chain reaction (nRT-PCR). The serological analysis indicated that 100% of the sampled chickens showed aMPV antibodies by 12 weeks of age. Five pools of pullet samples collected at 3 to 8 weeks of age were positive by nRT-PCR and the sequences obtained indicated 98 to 99% similarity with the reported sequences for aMPV subtype A. Virus isolation of nRT-PCR-positive samples was successfully attempted using chicken embryo lung and trachea mixed cultures with subsequent adaptation to Vero cells. This is the first report of detection and isolation of aMPV in Mexico.

Detection of and phylogenetic studies with avian metapneumovirus recovered from feral pigeons and wild birds in Brazil

The aim of the present study was to determine whether avian metapneumovirus (aMPV)-related viruses were present in wild and synanthropic birds in Brazil. Therefore, we analysed samples from wild birds, feral pigeons and domestic chickens in order to perform a phylogenetic comparison. To detect the presence of aMPV, a nested reverse transcriptase-polymerase chain reaction was performed with the aim of amplifying a fragment of 270 bases for subtype A and 330 bases for subtype B, comprising the gene coding the G glycoprotein. Positive samples for aMPV subtypes A and B were found in seven (13.2%) different asymptomatic wild birds and pigeons (50%) that had been received at the Bosque dos Jequitibás Zoo Triage Center, Brazil. Also analysed were positive samples from 15 (12.9%) domestic chickens with swollen head syndrome from several regions of Brazil. The positive samples from wild birds, pigeons and domestic chickens clustered in two major phylogenetic groups: some with aMPV subtype A and others with subtype B. The similarity of the G fragment nucleotide sequence of aMPV isolated from chickens and synanthropic and wild avian species ranged from 100 to 97.5% (from 100 to 92.5% for the amino acids). Some positive aMPV samples, which were obtained from wild birds classified in the Orders Psittaciformes, Anseriformes and Craciformes, clustered with subtype A, and others from the Anas and Dendrocygma genera (Anseriformes Order) with subtype B. The understanding of the epizootiology of aMPV is very important, especially if this involves the participation of non-domestic bird species, which would add complexity to their control on farms and to implementation of vaccination programmes for aMPV.

Propagation of avian metapneumovirus subtypes A and B using chicken embryo related and other cell systems

Primary isolation of avian metapneumovirus (aMPV) is carried out using tracheal organ culture (TOC) or chicken embryonated eggs with subsequent adaptation in chicken embryo fibroblasts (CEF) or Vero cultures. This study was conducted to evaluate six different cell lines and two avian culture systems for the propagation of aMPV subtypes A and B. The chicken embryo related (CER) cells were used successfully for primary isolation. In addition to Vero and baby hamster kidney (BHK-21) cells, CER cells were also shown to be the most appropriate for propagation of aMPV considering high titres. Propagation of A and B subtypes in CEF and TOC remained efficient after the primary isolation and several passages of viruses in the CER cell line. The growth curves were created using CER, Vero and BHK-21 cell lines. Compared with growth, both yielded higher titres in CER cells during the first 30 h after infection, but no significant difference was observed in the results obtained from CER and Vero cells. This data show that CER cells are adequate for aMPV subtypes A and B propagation, giving similar results to Vero cells.

Infectious bronchitis virus replication in the chicken embryo related cell line

The susceptibility of the chicken embryo related (CER) cell line to infectious bronchitis virus (IBV M41) was characterized after five consecutive passages in CER cells. Virus replication was monitored by cytopathic effect observation, electron microscopy, indirect immunofluorescence, and reverse transcription polymerase chain reaction (RT-PCR). At 96 h post-infection (p.i.), the cytopathic effect was graded 75% by cell fusion, rounding up of cells and monolayer detachment, and the electron microscopy image characterized by coronavirus morphology. Cytoplasmic fluorescence was readily observed by from 24 h p.i. onwards, and at all times the respective viral RNA from IBV-infected monolayers was demonstrated by RT-PCR. Extra-cellular virus was measured by virus titration performed on chicken kidney cells and embryonated chicken eggs, and respective titres ranged from 4.0 to 6.0 log10 EID50/ml on embryonated chicken eggs, and from 2.0 to 6.0 log10 TCID50/ml on both CER cells and chicken kidney cells studied from 24 to 120 h p.i. These results confirmed that the M41 strain replicated well in the CER cell line.

Metapneumoviruses in birds and humans

Avian pneumovirus (APV, Turkey rhinotracheitis virus) and Human metapneumovirus (hMPV) are pathogens of birds and humans, respectively, that are associated with upper respiratory tract infections. Based on their different genomic organization and low level of nucleotide (nt) and amino acid (aa) identity with paramyxoviruses in the genus Pneumovirus, APV and hMPV have been classified into a new genus referred to as Metapneumovirus. First isolated in 1970s, APV strains have since been isolated in Europe, Africa, middle east, and United States (US) and classified in four subgroups, APV/A, APV/B, APV/C, and APV/D based on nt and predicted aa sequence identity. Although it was first isolated in 2001, serological evidence indicates that hMPV may have been present in human population from as early as the 1950s. There is only one subgroup of hMPV so far, whose nt and aa sequence identity indicates that it is more closely related to APV/C than to APV/A, APV/B, or APV/D.

Characterization of avian metapneumoviruses isolated in the USA

Avian pneumovirus (APV; officially known as turkey rhinotracheitis virus) is an emergent pathogen of birds in the USA that results in upper respiratory tract disease in turkeys. Six years after the first outbreak in the USA, the disease continues to ravage turkey flocks, primarily in the state of Minnesota. From 1997 to 2000, the industry recorded losses estimated at 15 million US dollars per annum. Researchers have developed sensitive diagnostic techniques, including the enzyme-linked immunosorbent assay and the reverse transcriptase-polymerase chain reaction. which, when used together, are highly sensitive in detecting APV outbreaks in commercial turkey flocks. Phylogenetic analysis of the nucleotide and predicted amino acid sequence of 15 US viruses isolated between 1996 and 2000 demonstrated that the US viruses are relatively homogenous but different from the European APV subgroups A and B, resulting in the classification of US isolates into subgroup C. Infectious APV was isolated from sentinel waterfowls placed close to an infected commercial turkey farm and from wild Canada geese captured in Minnesota, suggesting that free-ranging birds may be involved in the spread of APV. Current efforts to prevent and control the infection include improving management and biosecurity practices and developing attenuated live and deletion mutant vaccines capable of conferring protection.

Susceptibility of ducks to avian pneumovirus of turkey origin

OBJECTIVE

To determine the susceptibility of ducks to avian pneumovirus (APV) of turkey origin.

ANIMALS

30 Pekin ducks that were 2 weeks old.

PROCEDURE

Ducks were assigned to 3 groups (10 ducks/group). Ducks of groups 1 and 2 were inoculated (day 0) with 200 microl of cell-culture fluid containing APV of turkey origin (10(5.5) median tissue-culture infective dose/ml) by the oculonasal (group 1) or oral (group 2) route. Ducks of group 3 served as noninoculated control birds. Two ducks from each group were euthanatized 3, 6, 9, 15, and 21 days after inoculation. Blood samples, tissue samples from the lungs, trachea, nasal turbinates, duodenum, diverticulum vitellinum (Meckel's diverticulum), and cecum, and swab specimens from the choana, cloaca, and trachea were obtained from all birds during necropsy and examined for APV by use of reverse transcriptase-polymerase chain reaction (RT-PCR), virus isolation, and histologic examination. Blood samples also were examined for APV antibodies, using an ELISA.

RESULTS

Tissue samples obtained up to 21 days after inoculation had positive results when tested by use of RT-PCR. Virus was isolated from nasal turbinates of birds inoculated via the oculonasal route. Serum samples obtained 15 and 21 days after inoculation had positive results when tested for APV-specific antibody. Clinical signs of disease were not observed in ducks inoculated with APV of turkey origin.

CONCLUSIONS AND CLINICAL RELEVANCE

Ducks inoculated with APV of turkey origin may not develop clinical signs of disease, but they are suspected to play a role as nonclinical carriers of APV.

PCR-based detection of an emerging avian pneumovirus in US turkey flocks

Avian pneumovirus (APV) or turkey rhinotracheitis virus (TRTV) is an important respiratory pathogen of domesticated poultry in many countries in Europe, Africa, and Asia. Until recently, the United States was considered free of APV. In late 1996, an atypical upper respiratory tract infection appeared in turkey flocks in Colorado and shortly thereafter in turkey flocks in Minnesota. An avian pneumovirus (APV-US) that was serologically distinct from the previously described TRTV was isolated as the primary cause of the new syndrome. The nucleotide sequence of a fragment of the APV-US fusion gene was determined and used to develop a polymerase chain reaction-based assay that specifically detects APV-US viral nucleic acid sequences in RNA extracts of tracheal swabs and turbinate homogenates. The assay is highly sensitive in that it can detect <0.01 TCID50 of APV. The availability of this assay enables the rapid and accurate determination of APV-US in infected poultry flocks.

Avian pneumoviruses and emergence of a new type in the United States of America

Avian pneumovirus (APV) primarily causes an upper respiratory disease recognized as turkey rhinotracheitis (TRT) or swollen head syndrome (SHS) in chickens. The virus was first isolated in South Africa during the early 1970s and has subsequently been reported in Europe, Asia and South America. In February 1997, a serologically distinct APV isolate was officially reported in the USA following an outbreak of TRT during the previous year. This was the first report of these virus types in the USA; they were previously considered exotic to the USA and Canada. The predicted matrix (M) proteins of European APV type A and B isolates share 89% identity in their amino acid sequence. However, the predicted M protein of APV/CO is only 78% similar to the APV type A and 77% similar to the APV type B protein sequence. The predicted amino acid sequence of the US APV isolate's fusion (F) protein has 72% sequence identity to the F protein of APV type A and 71% sequence identity to the F protein of type B. This compares with the 83% sequence identity between the predicted amino acid sequences of the F proteins of APV types A and B. The lack of sequence heterogeneity among the US APV isolates over 2 years suggests that these viruses have maintained a relatively stable population since the first outbreak of TRT. Phylogenetic analysis of the M and F proteins, together with the serological uniqueness of the US APV isolates, supports their classification as a new APV, designated type C.

Fusion protein predicted amino acid sequence of the first US avian pneumovirus isolate and lack of heterogeneity among other US isolates

Avian pneumovirus (APV) was first isolated from turkeys in the west-central US following emergence of turkey rhinotracheitis (TRT) during 1996. Subsequently, several APV isolates were obtained from the north-central US. Matrix (M) and fusion (F) protein genes of these isolates were examined for sequence heterogeneity and compared with European APV subtypes A and B. Among US isolates the M gene shared greater than 98% nucleotide sequence identity with only one nonsynonymous change occurring in a single US isolate. Although the F gene among US APV isolates shared 98% nucleotide sequence identity, nine conserved substitutions were detected in the predicted amino acid sequence. The predicted amino acid sequence of the US APV isolate's F protein had 72% sequence identity to the F protein of APV subtype A and 71% sequence identity to the F protein of APV subtype B. This compares with 83% sequence identity between the APV subtype A and B predicted amino acid sequences of the F protein. The US isolates were phylogenetically distinguishable from their European counterparts based on F gene nucleotide or predicted amino acid sequences. Lack of sequence heterogeneity among US APV subtypes indicates these viruses have maintained a relatively stable population since the first outbreak of TRT. Phylogenetic analysis of the F protein among APV isolates supports classification of US isolates as a new APV subtype C.