Dual infection and superinfection inhibition of epithelial skin cells by two alphaherpesviruses co-occur in the natural host.

Keith W Jarosinski

doi:10.1371/journal.pone.0037428

Abstract

Hosts can be infected with multiple herpesviruses, known as superinfection; however, superinfection of cells is rare due to the phenomenon known as superinfection inhibition. It is believed that dual infection of cells occurs in nature, based on studies examining genetic exchange between homologous alphaherpesviruses in the host, but to date, this has not been directly shown in a natural model. In this report, gallid herpesvirus 2 (GaHV-2), better known as Marek’s disease virus (MDV), was used in its natural host, the chicken, to determine whether two homologous alphaherpesviruses can infect the same cells in vivo. MDV shares close similarities with the human alphaherpesvirus, varicella zoster virus (VZV), with respect to replication in the skin and exit from the host. Recombinant MDVs were generated that express either the enhanced GFP (eGFP) or monomeric RFP (mRFP) fused to the UL47 (VP13/14) herpesvirus tegument protein. These viruses exhibited no alteration in pathogenic potential and expressed abundant UL47-eGFP or -mRFP in feather follicle epithelial cells in vivo. Using laser scanning confocal microscopy, it was evident that these two similar, but distinguishable, viruses were able to replicate within the same cells of their natural host. Evidence of superinfection inhibition was also observed. These results have important implications for two reasons. First, these results show that during natural infection, both dual infection of cells and superinfection inhibition can co-occur at the cellular level. Secondly, vaccination against MDV with homologous alphaherpesvirus like attenuated GaHV-2, or non-oncogenic GaHV-3 or meleagrid herpesvirus (MeHV-1) has driven the virus to greater virulence and these results implicate the potential for genetic exchange between homologous avian alphaherpesviruses that could drive increased virulence. Because the live attenuated varicella vaccine is currently being administered to children, who in turn could be superinfected by wild-type VZV, this could potentiate recombination events of VZV as well.

Highlights

Marek’s disease (MD) is caused by gallid herpesvirus 2 (GaHV-2), better known as MD virus (MDV)
AChickens were inoculated with 2,000 plaque-forming units (PFU) of vUL47-enhanced GFP (eGFP) or vUL47-monomeric RFP (mRFP), or with a mixture of 1,000 PFU of vUL47-eGFP and vUL47-mRFP each at 7 days of age. bSkin samples were collected at 28 days post-inoculation (p.i.). cThe number of follicles examined for each chicken. dThe number of follicles positive for green fluorescence and percent follicles infected per group. eThe number of follicles positive for red fluorescence and percent follicles infected per group. fThe number of follicles positive for both green and red fluorescence and percent follicles infected with both viruses per group. gThe number of regions within follicles that were positive for both green and red fluorescence and the total per group
This study is the first report directly showing that dual infection with two alphaherpesviruses actively replicating within the same cells occurs in a natural virus-host model, while within the same host, superinfection inhibition can co-occur

Summary

Introduction

Marek’s disease (MD) is caused by gallid herpesvirus 2 (GaHV-2), better known as MD virus (MDV). The lifecycle of MDV is similar to a human alphaherpesvirus, varicella zoster virus (VZV, human herpesvirus 3, HHV-3), that causes varicella, commonly called chicken pox, during primary infection and herpes zoster, commonly referred to as shingles, during reactivation from latency. Both viruses enter the host through the respiratory tract, initially infect epithelial cells and lymphocytes, which transport virus to the skin where infectious virus is produced in epithelial skin cells and shed into the environment [2,4]

Methods

Results

Conclusion