The UL49 gene product of BoHV-1: a major factor in efficient cell-to-cell spread

Abstract

The role of the UL49 gene product, VP22, of bovine herpesvirus type 1 (BoHV-1) in virus replication was characterized with respect to a putative functional interaction of VP22 with the viral glycoprotein E (gE) during BoHV-1 cell-to-cell spread. Deletion of the open reading frames of UL49 and/or gE from an infectious BoHV-1 bacterial artificial chromosome clone did not severely impair the production of viral progeny in single-step growth experiments. However, plaque sizes induced by a VP22-negative BoHV-1 were reduced by 52 %, whilst for the gE/VP22-negative double-deletion mutant a reduction of 83 % could be observed in comparison with parental and revertant viruses, which was consistent with a marked reduction in multi-step growth experiments at early time points. These results suggest that gE and VP22 are important for BoHV-1 cell-to-cell spread, and that both are likely to act independently of each other in a critical pathway for virus cell-to-cell spread.Bovine herpesvirus type 1 (BoHV-1), a member of the subfamily Alphaherpesvirinae (Fauquet et al., 2005), is a major cause of respiratory and genital tract disease in cattle (Gibbs & Rweyemamu, 1977). Like other alphaherpesviruses, such as herpes simplex virus type 1 (HSV-1), pseudorabies virus (PrV) and varicella-zoster virus (VZV), BoHV-1 infects both epithelial and neuronal tissues (Arvin, 1996;Corey & Spear, 1986;Field & Hill, 1975;Tikoo et al., 1995). Within these specialized compartments, virus can disseminate efficiently by means of direct cell-to-cell spread, which protects infectious virions from the adverse effects of neutralizing antibodies (Johnson & Huber, 2002). Virus cell-to-cell spread and entry of extracellular virus particles frequently share mechanistic details, e.g. the utilization of similar membrane fusion machinery, but cell-to-cell spread also involves other intra-and extracellular biophysical events determining virus delivery to cell junctions, as well as the use of receptors found exclusively at cell junctions (Johnson & Huber, 2002).As in other alphaherpesviruses, the BoHV-1 complex of glycoprotein E (gE) and gI is not involved in the entry of extracellular particles (Rebordosa et al., 1996;Yoshitake et al., 1997) and hence viral gE deletion mutants display unimpaired penetration kinetics and virus yields in cell culture (Rebordosa et al., 1996). However, deletion of BoHV-1 gE is generally associated with a marked reduction in plaque size in vitro (Rebordosa et al., 1996;Trapp et al., 2003), and gE deletion mutants have been shown to be attenuated in their respective bovine host (van Engelenburg et al., 1994). Interestingly, for cell-associated alphaherpesviruses, such as VZV and Marek's disease virus (MDV), formation of the gE/gI complex is critical for virus replication in vitro (Mallory et al., 1997;Schumacher et al., 2001). With respect to virion morphogenesis, Fuchs et al. (2002) Previously, a BoHV-1DUL49 deletion mutant was shown to produce decreased extracellular virus titres and to be avirulent in its bovine host (Liang et...

Fluorescent tagging of VP22 in N-terminus reveals that VP22 favors Marek’s disease virus (MDV) virulence in chickens and allows morphogenesis study in MD tumor cells

“…The UL49 gene has been shown to be absolutely necessary for the replication of MDV and VZV [16-18] whereas UL49 is dispensable for Pseudorabies virus (PRV), Herpes Simplex type 1 (HSV1), and Bovine Herpes virus type 1 (BoHV1) [19-22]. In BoHV1, the deletion of UL49 reduced extracellular virus titers of about 10-fold [23] and plaques size in MDBK by 52% [21]. In HSV-1, the absence of UL49 impaired virus growth in MDBK, but not in Vero cells [20].…”

Alphaherpesvirus Major Tegument Protein VP22: Its Precise Function in the Viral Life Cycle

“…Deletion of gE resulted in a 53% reduction in plaque diameter, while a single deletion of UL49 resulted in a 52% reduction. However, the simultaneous deletion of gE and UL49 resulted in a 83% reduction in the diameter of the virus plaque, indicating that gE and VP22 are two equally important factors for BoHV-1 cell-to-cell spread and that both are likely to act independently of each other in a critical pathway of virus cell-to-cell spread ( Kalthoff et al, 2008 ).…”

“…important factors for BoHV-1 cell-to-cell spread and that both are likely to act independently of each other in a critical pathway of virus cell-to-cell spread (Kalthoff et al, 2008).…”

The Carboxyl Terminus of Tegument Protein pUL21 Contributes to Pseudorabies Virus Neuroinvasion

“…One-step growth curve determination and plaque morphology comparison were performed as described previously (69,70). Multistep growth curve determination was performed as previously described, with minor modifications (72)(73)(74). Confluent PK-15 cells were infected with PRV at an MOI of 0.01.…”