In vivo egress of an alphaherpesvirus from axons.
(17/106)
Many alphaherpesviruses establish a latent infection in the peripheral nervous systems of their hosts. This life cycle requires the virus to move long distances in axons toward the neuron's cell body during infection and away from the cell body during reactivation. While the events underlying entry of the virion into neurons during infection are understood in principle, no such consensus exists regarding viral egress from neurons after reactivation. In this study, we challenged two different models of viral egress from neurons by using pseudorabies virus (PRV) infection of the rat retina: does PRV egress solely from axon terminals, or can the virus egress from axon shafts as well as axon terminals? We took advantage of PRV gD mutants that are not infectious as extracellular particles but are capable of spreading by cell-cell contact. We observed that both wild-type virus and a PRV gD null mutant are capable of spreading from axons to closely apposed nonneuronal cells within the rat optic nerve after intravitreal infection. However, infection does not spread from these infected nonneuronal cells. We suggest that viral egress can occur sporadically along the length of infected axons and is not confined solely to axon terminals. Moreover, it is likely that extracellular particles are not involved in nonneuronal cell infections. Taking these together with previous data, we suggest a model of viral egress from neurons that unifies previous apparently contradictory data. (+info)
The immediate early gene of canine herpesvirus is transcribed through early and late phases.
(18/106)
The immediate early (IE) gene of canine herpesvirus (CHV), homologue of the infected cell protein 4 (ICP4) gene of herpes simplex virus 1, is transcribed as a 4.9kb mRNA during IE phase. The IE gene was further transcribed as a 4.8kb mRNA through early (E) and late (L) phases of productive infection. Transcription of the 4.8kb mRNA initiated from downstream of the TATA box in an intron which was spliced out during IE phase. The reverse transcription-polymerase chain reaction revealed that the IE promoter was turned off during L phase at a permissive temperature. We, thus, propose to redesignate the IE gene of CHV as CICP4 gene. (+info)
Identification and expression of immunogenic proteins of a disease-associated marine turtle herpesvirus.
(19/106)
Herpesviruses are associated with several diseases of marine turtles, including lung-eye-trachea disease (LETD) and fibropapillomatosis. Two approaches were used to identify immunodominant antigens of LETV, the LETD-associated herpesvirus. The first approach targeted glycoprotein B, which is known to be immunogenic and neutralizing in other species. The second strategy identified LETV proteins recognized on Western blots by antibodies in immune green turtle plasma. A 38-kDa protein was resolved by two-dimensional gel electrophoresis, sequenced, and identified as a scaffolding protein encoded by the overlapping open reading frames of UL26 and UL26.5. Glycoprotein B and the scaffolding protein were cloned and expressed in Escherichia coli. The expressed proteins were recognized on Western blots by antibodies in immune green turtle plasma. Phylogenetic studies based on UL26, DNA polymerase, and glycoprotein B revealed that LETV clusters with the alphaherpesviruses. (+info)
Glycoprotein G isoforms from some alphaherpesviruses function as broad-spectrum chemokine binding proteins.
(20/106)
Mimicry of host chemokines and chemokine receptors to modulate chemokine activity is a strategy encoded by beta- and gammaherpesviruses, but very limited information is available on the anti-chemokine strategies encoded by alphaherpesviruses. The secretion of chemokine binding proteins (vCKBPs) has hitherto been considered a unique strategy encoded by poxviruses and gammaherpesviruses. We describe a family of novel vCKBPs in equine herpesvirus 1, bovine herpesvirus 1 and 5, and related alphaherpesviruses with no sequence similarity to chemokine receptors or other vCKBPs. We show that glycoprotein G (gG) is secreted from infected cells, binds a broad range of chemokines with high affinity and blocks chemokine activity by preventing their interaction with specific receptors. Moreover, gG also blocks chemokine binding to glycosaminoglycans, an interaction required for the correct presentation and function of chemokines in vivo. In contrast to other vCKBPs, gG may also be membrane anchored and, consistently, we show chemokine binding activity at the surface of cells expressing full-length protein. These alphaherpesvirus vCKBPs represent a novel family of proteins that bind chemokines both at the membrane and in solution. (+info)
Genetic characterization of the unique short segment of phocid herpesvirus type 1 reveals close relationships among alphaherpesviruses of hosts of the order Carnivora.
(21/106)
To further characterize phocid herpesvirus type 1 (PhHV-1) at the molecular level, a cluster of genes comprising the complete unique short (Us) region of PhHV-1 has been cloned and sequenced. Within this region, ORFs were detected that code for the equivalent of the Us 2- protein of herpes simplex virus (HSV), a putative protein kinase, and for the glycoprotein equivalents gG, gD, gI and gE. In addition, two small ORFs downstream of gE, homologous to the Us 8.5 and Us 9 proteins of HSV were identified. Comparative analysis of the ORF encoding the gD equivalent of PhHV-1 identified the corresponding proteins of the alphaherpesviruses canine herpesvirus and, to lesser degree, feline herpesvirus as the closest relatives. (+info)
Molecular phylogeny of the psittacid herpesviruses causing Pacheco's disease: correlation of genotype with phenotypic expression.
(22/106)
Fragments of 419 bp of the UL16 open reading frame from 73 psittacid herpesviruses (PsHVs) from the United States and Europe were sequenced. All viruses caused Pacheco's disease, and serotypes of the European isolates were known. A phylogenetic tree derived from these sequences demonstrated that the PsHVs that cause Pacheco's disease comprised four major genotypes, with each genotype including between two and four variants. With the exception of two viruses, the serotypes of the virus isolates could be predicted by the genotypes. Genotypes 1 and 4 corresponded to serotype 1 isolates, genotype 2 corresponded to serotype 2 isolates, and genotype 3 corresponded to serotype 3 isolates. The single serotype 4 virus mapped to genotype 4. DNA from a virus with a unique serotype could not be amplified with primers that amplified DNA from all other PsHVs, and its classification remains unknown. Viruses representing all four genotypes were found in both the United States and Europe, and it was therefore predicted that serotypes 1, 2, and 3 were present in the United States. Serotype 4 was represented by a single European isolate that could not be genetically distinguished from serotype 1 viruses; therefore, the presence of serotype 4 in the United States could not be predicted. Viruses of genotype 4 were found to be the most commonly associated with Pacheco's disease in macaws and conures and were least likely to be isolated in chicken embryo fibroblasts in the United States. All four genotypes caused deaths in Amazon parrots, but genotype 4 was associated with Pacheco's disease only in Amazons in Europe. Genotypes 2, 3, and 4, but not 1, were found in African grey parrots. Although parrots from the Pacific distribution represent a relatively small percentage of the total number of birds with Pacheco's disease, all four genotypes were found to cause disease in these species. (+info)
Reannotation of the CELO genome characterizes a set of previously unassigned open reading frames and points to novel modes of host interaction in avian adenoviruses.
(23/106)
BACKGROUND: The genome of the avian adenovirus Chicken Embryo Lethal Orphan (CELO) has two terminal regions without detectable homology in mammalian adenoviruses that are left without annotation in the initial analysis. Since adenoviruses have been a rich source of new insights into molecular cell biology and practical applications of CELO as gene a delivery vector are being considered, this genome appeared worth revisiting. We conducted a systematic reannotation and in-depth sequence analysis of the CELO genome. RESULTS: We describe a strongly diverged paralogous cluster including ORF-2, ORF-12, ORF-13, and ORF-14 with an ATPase/helicase domain most likely acquired from adeno-associated parvoviruses. None of these ORFs appear to have retained ATPase/helicase function and alternative functions (e.g. modulation of gene expression during the early life-cycle) must be considered in an adenoviral context. Further, we identified a cluster of three putative type-1-transmembrane glycoproteins with IG-like domains (ORF-9, ORF-10, ORF-11) which are good candidates to substitute for the missing immunomodulatory functions of mammalian adenoviruses. ORF-16 (located directly adjacent) displays distant homology to vertebrate mono-ADP-ribosyltransferases. Members of this family are known to be involved in immuno-regulation and similiar functions during CELO life cycle can be considered for this ORF. Finally, we describe a putative triglyceride lipase (merged ORF-18/19) with additional domains, which can be expected to have specific roles during the infection of birds, since they are unique to avian adenoviruses and Marek's disease-like viruses, a group of pathogenic avian herpesviruses. CONCLUSIONS: We could characterize most of the previously unassigned ORFs pointing to functions in host-virus interaction. The results provide new directives for rationally designed experiments. (+info)
Characterization of vnr-13, the first alphaherpesvirus gene of the bcl-2 family.
(24/106)
The Bcl-2 family, including antiapoptotic and proapoptotic members, plays key regulating roles in programmed cell death. We report the characterization of a new member of the bcl-2 family, encoded by herpesvirus of turkeys (HVT). The product of this gene shares 80% homology with Nr-13, an apoptosis inhibitor, which is overexpressed in avian cells transformed by the v-src oncogene. This new gene, that we propose to call vnr-13, is the first member of the bcl-2 family to be isolated among alpha-herpesviruses. Results from cells expressing the HVT-vnr-13 gene product show that the encoded protein inhibits apoptosis and also reduces the rate of cellular proliferation. Contrary to all bcl-2 homologues found in gamma-herpesvirus, which are intronless, vnr-13 has the same organization as the cellular nr-13 gene. Hence, the HVT vnr-13 gene may have been acquired from a reverse transcriptase product of an unspliced precursor RNA, or via direct recombination with the host chromosomal DNA. (+info)