The Equine Herpesvirus 1 IR6 Protein Influences Virus Growth at Elevated Temperature and Is a Major Determinant of Virulence

144

114

Here we present the complete genomic sequence of bovine herpesvirus 5 (BHV-5), an alphaherpesvirus responsible for fatal meningoencephalitis in cattle. The 138,390-bp genome encodes 70 putative proteins and resembles the ␣2 subgroup of herpesviruses in genomic organization and gene content. BHV-5 is very similar to BHV-1, the etiological agent of infectious bovine rhinotracheitis, as reflected by the high level of amino acid identity in their protein repertoires (average, 82%). The highest similarity to BHV-1 products (>95% amino acid identity) is found in proteins involved in viral DNA replication and processing (UL5, UL15, UL29, and UL39) and in virion proteins (UL14, UL19, UL48, and US6). Among the least conserved (<75%) are the homologues of immediate-early (IE) proteins BICP0, BICP4, and BICP22, the three proteins being longer in BHV-5 than in BHV-1. The structure of the BHV-5 latency-related (LR) region departs markedly from that of BHV-1 in both coding and transcriptional regulatory regions. Given the potential significance of IE genes and the LR region in virus-neuron interactions, it is likely these differences contribute to BHV-5 neuropathogenicity.

Section: Resultsmentioning

confidence: 99%

Genome of Bovine Herpesvirus 5

Delhon

Moraes

et al. 2003

144

114

“…The pathogenic wild-type EHV-1 strain Rac L11 was propagated on RK13 or Edmin337 cells (38). Cells were infected at a multiplicity of infection (MOI) of 0.5 to 1 and incubated at 37°C.…”

Section: Cells and Virusesmentioning

confidence: 99%

Egress of Alphaherpesviruses: Comparative Ultrastructural Study

Granzow¹,

Klupp

Fuchs

et al. 2001

Self Cite

243

241

Egress of four important alphaherpesviruses, equine herpesvirus 1 (EHV-1), herpes simplex virus type 1 (HSV-1), infectious laryngotracheitis virus (ILTV), and pseudorabies virus (PrV), was investigated by electron microscopy of infected cell lines of different origins. In all virus-cell systems analyzed, similar observations were made concerning the different stages of virion morphogenesis. After intranuclear assembly, nucleocapsids bud at the inner leaflet of the nuclear membrane, resulting in enveloped particles in the perinuclear space that contain a sharply bordered rim of tegument and a smooth envelope surface. Egress from the perinuclear cisterna primarily occurs by fusion of the primary envelope with the outer leaflet of the nuclear membrane, which has been visualized for HSV-1 and EHV-1 for the first time. The resulting intracytoplasmic naked nucleocapsids are enveloped at membranes of the trans-Golgi network (TGN), as shown by immunogold labeling with a TGN-specific antiserum. Virions containing their final envelope differ in morphology from particles within the perinuclear cisterna by visible surface projections and a diffuse tegument. Particularly striking was the addition of a large amount of tegument material to ILTV capsids in the cytoplasm. Extracellular virions were morphologically identical to virions within Golgi-derived vesicles, but distinct from virions in the perinuclear space. Studies with gB-and gH-deleted PrV mutants indicated that these two glycoproteins, which are essential for virus entry and direct cell-to-cell spread, are dispensable for egress. Taken together, our studies indicate that the deenvelopment-reenvelopment process of herpesvirus maturation also occurs in EHV-1, HSV-1, and ILTV and that membrane fusion processes occurring during egress are substantially different from those during entry and direct viral cell-to-cell spread.Herpesviruses are large DNA-containing enveloped viruses that replicate in the nuclei of infected cells. Based on biological parameters and sequence data, the family Herpesviridae is divided into the subfamilies Alpha-, Beta-, and Gammaherpesvirinae (58). Despite their biological diversity, many steps of herpesvirus morphogenesis seem to be conserved. Attached herpesvirus virions penetrate the cell membrane by direct fusion between the viral envelope and the plasma membrane, and the deenveloped nucleocapsids reach the nucleopores by movement along cellular microtubuli, where the genomic DNA is released into the nucleus (19,50,51,52). Progeny nucleocapsids assemble in the nucleus and exit this compartment by budding at the inner nuclear membrane into the perinuclear space (35,47). The subsequent events of envelopment and egress remain controversial. Whereas for herpes simplex virus type 1 (HSV-1), a model that entails vesicular transport of enveloped virions through the secretory pathway with concomitant in situ modification of virion glycoproteins was initially proposed, for varicella-zoster virus (VZV), pseudorabies virus (PrV), and human cytomegalovir...

“…Virus titers and plaque diameters were analyzed by performing an analysis of variance, followed by multiple comparisons of the groups. Therefore, P values were adjusted according to the method of Bonferroni as described previously (29). SAS software (version 8.2; SAS Institute, Cary, N.C.) was used for the statistical calculations.…”

Section: Plasmidsmentioning

confidence: 99%

“…Animal experiments were conducted as described previously (17,29). Briefly, 3-to 4-week old female BALB/c mice (10 mice per group) were infected with the various virus preparations by the intranasal route at 10 (28).…”

Section: Plasmidsmentioning

confidence: 99%

The Truncated Form of Glycoprotein gp2 of Equine Herpesvirus 1 (EHV-1) Vaccine Strain KyA Is Not Functionally Equivalent to Full-Length gp2 Encoded by EHV-1 Wild-Type Strain RacL11

Einem

Wellington

Whalley

et al. 2004

Self Cite

Equine herpesvirus 1 (EHV-1), a member of Varicellovirus genus in the Alphaherpesvirinae subfamily, is one of the most prevalent viruses affecting equine populations worldwide. Infection with EHV-1 may result in rhinopneumonitis, abortion, and often fatal encephalomyelitis. The continuing threat imposed by EHV-1 results in ongoing efforts aiming at a better understanding of EHV-1 pathogenesis and at developing safe and effective vaccines (27). Herpesviral glycoproteins are involved in different stages of virus infection and are major targets of the host's immune response. Envelope glycoproteins of EHV-1 are designated gB, gC, gD, gE, gG, gH, gI, gK, gL, and gM according their homologues in herpes simplex virus type 1 (HSV-1) (reviewed in reference 28). Compared to HSV-1 and other Alphaherpesvirinae, however, EHV-1 encodes two additional glycoproteins. One of the glycoproteins unique to EHV-1 was originally designated gp2 or gp300 (2, 45) and is expressed from gene 71 (EUS4) (38,42). Homologues of gp2 are found in EHV-1, EHV-4, and asinine herpesvirus 3 (8) and are among the mostabundant and -immunogenic glycoproteins in EHV-1 and EHV-4 virions (1, 7). EHV-1 gp2 is rich in serine and threonine residues and is a heavily O-glycosylated protein with a molecular mass in the range of 192 to Ͼ400 kDa (38,39,45). In contrast to EHV-4 gp2, the EHV-1 glycoprotein was shown to be partially cleaved into two polypeptides in infected cells (19). Endoproteolytic cleavage occurs after each of two adjacent arginine (R) residues at positions 506 and 507 in the sequence HRGRAGGR 506 R 507 G, and results in a 42-kDa carboxy-terminal subunit, which contains the transmembrane anchor, and an N-terminal serine/threonine-rich component that is highly O-glycosylated (19, 43). In the absence of gp2, EHV-1 strains were shown to be impaired in virus egress, while secondary envelopment appears to occur with unaltered kinetics and efficiency (31,32,37). It was also reported that deletion of gene 71 in EHV-1 strain Ab4 resulted in attenuation, and the generated virus mutant used as an experimental vaccine conferred protection against pulmonary disease in mice after challenge with wild-type virus (21).A number of EHV-1 strains with different biological properties have been described. While the RacL11 strain was isolated in the late 1950s from an aborted foal and exhibits high virulence in the natural host and laboratory animals, strain KyA, a candidate vaccine strain, is completely apathogenic for both mice and horses after serial passage in mouse L-M cells (6,25,26). As a result of a long history of passages in nonhomologous cells, KyA exhibits several genomic alterations,