Avian encephalomyelitis virus is a picornavirus and is most closely related to hepatitis A virus.
(1/8)
The complete RNA genome of avian encephalomyelitis virus (AEV) has been molecularly cloned and sequenced. This revealed AEV to be a member of the Picornaviridae and consequently it is the first avian picornavirus for which the genome has been sequenced. Excluding the poly(A) tail the genome comprises 7032 nucleotides, which is shorter than that of any mammalian picornavirus sequenced to date. An open reading frame commencing at nucleotide 495 and terminating at position 6896 (6402 nucleotides) potentially encodes a polyprotein of 2134 amino acids. The polyprotein sequence has 39% overall amino acid identity with hepatitis A virus (HAV; genus Hepatovirus), compared to 19 to 21% for viruses from the other five picornavirus genera. Eleven cleavage products were predicted. The highest identity (49%) with HAV was in the P1 region, encoding the capsid proteins. The 5' and 3' untranslated regions (UTRs) comprise 494 and 136 nucleotides, respectively. The 5' UTR is the shortest of any picornavirus sequenced to date and, unlike HAV, it does not contain a long polypyrimidine tract. (+info)
Serological monitoring on layer farms with specific pathogen-free chickens.
(2/8)
To monitor the existence of avian pathogens in laying chicken flocks, specific pathogen-free (SPF) chickens were introduced into two layer farms and reared with laying hens for 12 months. SPF chickens were bled several times after their introduction and examined for their sero-conversion to avian pathogens. As a result, antibodies to eight or ten kinds of pathogens were detected in SPF chickens on each farm. Antibodies to infectious bronchitis virus (IBV), avian nephritis virus, Mycoplasma gallisepticum and M. synoviae were detected early within the first month. Antibody titer to IBV suggested that the laying chickens were infected with IBV repeatedly during the experiment on both farms. However, antibodies to infectious bursal disease virus and 6 pathogens were not detected. (+info)
Avian encephalomyelitis virus induces apoptosis via major structural protein VP3.
(3/8)
Avian encephalomyelitis virus (AEV) strain L(2)Z was investigated for its apoptotic activity in specific-pathogen-free chick embryo brain tissue. DNA fragmentation analysis and electron microscopy observation demonstrated that AEV could induce apoptosis in chick embryo brain tissues characterized by chromatin condensation, plasma membrane blebbing, cell shrinkage, and nucleosomal DNA fragmentation after 4 days postinfection. AEV structural protein genes VP1, VP2, and VP3 were transfected into Cos-7 and chick embryo brain (CEB) cells, respectively. The results showed that only VP3 protein was an apoptotic inducer, as demonstrated by DNA fragmentation analysis and TUNEL assay at 24 and 48 h posttransfection. Furthermore, expression of VP3 protein resulted in the activation of caspase-3-like proteases in both cells, which could be inhibited by a caspase-3-like protease-specific inhibitor Ac-DEVD-CHO peptide, suggesting that AEV VP3 protein induces apoptosis through a caspase-3-like protease pathway. In addition, VP3 protein localized to mitochondria in the Cos-7 and CEB cells at 24 h posttransfection observed by confocal microscopy, indicating that mitochondria may play an important role in VP3-induced apoptosis. Taken together, our results show that AEV could induce apoptosis in chick embryo brain tissue, structural protein VP3 could serve as an apoptotic inducer resulting in apoptosis in cell culture through a caspase-3-like protease pathway, which may be related to its localization to mitochondria. (+info)
Avian encephalomyelitis virus nonstructural protein 2C induces apoptosis by activating cytochrome c/caspase-9 pathway.
(4/8)
The nonstructural protein 2C is highly conserved among picornaviruses and plays an important role in the assembly of mature virions, membrane association, and viral RNA synthesis. The investigation of other potential functions of nonstructural protein 2C from avian encephalomyelitis virus (AEV) resulted in identifying for the first time that the protein 2C is involved in apoptosis. Expression of the protein 2C on chick embryo brain (CEB) and Cos-7 cells produced TUNEL-positive cells characterized by a cleavage of cellular DNA and the formation of membrane-enclosed apoptotic bodies. Analysis of the protein 2C showed that the N-terminal domain containing 35 amino acid (aa) residues (between 46 and 80 aa) is associated with apoptotic function. Transfection of the deletion mutant lacking this 35 aa's into CEB and Cos-7 cells failed to induce apoptosis. Furthermore, the protein 2C induced apoptosis in the transfected CEB and Cos-7 cells through activation of caspase-9 rather than caspase-8 followed by activation of caspase-3 pathway. Analysis of the Western blots of caspase-3 and caspase-9 showed the characteristics of active caspase-3 and -9 in the 2C-transfected CEB and Cos-7 cells as seen in the AEV-infected CEB cells while they were in the form of procaspase-3 and procaspase-9 in the 2C mutant-transfected cells. To further elucidate the mechanism of the 2C-induced apoptosis, the 2C-transfected CEB and Cos-7 cells were fractionated into mitochondria and cytosol and subjected for Western blotting, located cytochrome c in the mitochondria as well as the cytosol fractions, while it was only sequestered in the mitochondrial fraction in the mutant 2C-transfected cells. The protein 2C was located in the mitochondria and cytosol of the transfected/infected CEB and transfected Cos-7 cells, but the mutant lost its ability to localize to the mitochondria. Altogether, the results demonstrate that the protein 2C localized to the mitochondria of the transfected cells triggered the efflux of cytochrome c into the cytosol in turn activating the upstream caspase-9 and then the downstream caspase-3, thus leading to apoptosis in the cells. (+info)
Membrane-association properties of avian encephalomyelitis virus protein 3A.
(5/8)
Avian encephalomyelitis virus (AEV) protein 3A is a membrane-interacting protein containing a stretch of 21 hydrophobic amino acid residues. Membrane-association property was assayed using chick embryo brain (CEB) cells transfected with the fusion GFP-3A and its various deletion mutants demonstrate that 3A is integrally interacted with membranes by its hydrophobic domain and further defines that the motif of amino acid residues 45-51, the most C-terminal hydrophobic domain essential for this feature. Expression of 3A in transfected CEB cells results in membrane permeability modifications through association of the third motif with membranes, which can be demonstrated by release of lactate dehydrogenase (LDH) into the medium. Furthermore, the localization of the protein 3A in transfected CEB and Cos-7 cells exhibited an overlapping staining pattern with an endoplasmic reticulum (ER) and involved in the disassembly of the Golgi apparatus under double-staining and confocal microscopic observations, whereas the 3A mutants lacking amino acids 45-51 could not localize to the ER and display an intact Golgi morphology as seen in the mutant devoid of the complete hydrophobic domain after transfection. Taken together, our results demonstrate that the motif (aa 45-51) of the transmembrane domain might be fundamental for the stable interaction of the protein 3A with the ER membrane regardless of the cell types. Although this motif was deleted, the resultant protein did not localize to the ER, which directly results in the loss of the ability to block the ER-to-Golgi transport by 3A protein and hence makes the morphology of the Golgi apparatus return to normal. (+info)
Pathogenesis of avian encephalomyelitis viruses.
(6/8)
The pathogenesis of a field strain, a vaccine strain and the egg-adapted Van Roekel strain of avian encephalomyelitis virus in susceptible chicken embryos and day-old chickens was investigated using enzyme-linked immunosorbent assays for the detection of virus-specific antibody and antigen. The Van Roekel strain was shown to be highly neurotropic whereas the field and vaccine strains were enterotropic. Radioimmuno-precipitation studies using Na125I-labelled purified virus failed to detect any differences in the composition of the structural viral proteins of each strain that could account for these differences. As expected, the field and vaccine strains were more efficient than the Van Roekel strain at inducing antibody following oral administration. Primary cultures of chicken embryo brain cells supported the growth of the Van Roekel strain to a much greater extent than the field and vaccine strains. (+info)
An outbreak of avian encephalomyelitis in turkeys in Canada.
(7/8)
An outbreak of avian encephalomyelitis in two week old turkey poults is described. The disease was diagnosed by the fluorescent antibody technique and was confirmed by neutralization tests conducted in chicks. (+info)
The picornavirus avian encephalomyelitis virus possesses a hepatitis C virus-like internal ribosome entry site element.
(8/8)
Avian encephalomyelitis virus (AEV) is a picornavirus that causes disease in poultry worldwide, and flocks must be vaccinated for protection. AEV is currently classified within the hepatovirus genus, since its proteins are most closely related to those of hepatitis A virus (HAV). We now provide evidence that the 494-nucleotide-long 5' untranslated region of the AEV genome contains an internal ribosome entry site (IRES) element that functions efficiently in vitro and in mammalian cells. Unlike the HAV IRES, the AEV IRES is relatively short and functions in the presence of cleaved eIF4G and it is also resistant to an inhibitor of eIF4A. These properties are reminiscent of the recently discovered class of IRES elements within certain other picornaviruses, such as porcine teschovirus 1 (PTV-1). Like the PTV-1 IRES, the AEV IRES shows significant similarity to the hepatitis C virus (HCV) IRES in sequence, function, and predicted secondary structure. Furthermore, mutational analysis of the predicted pseudoknot structure at the 3' end of the AEV IRES lends support to the secondary structure we present. AEV is therefore another example of a picornavirus harboring an HCV-like IRES element within its genome, and thus, its classification within the hepatovirus genus may need to be reassessed in light of these findings. (+info)