The Requirement of Turkey Herpesvirus (HVT) Glycoprotein C During Natural Infection in Chickens and Turkeys

The glycoprotein C (gC) of gallid alphaherpesvirus 2-better known as Marek's disease (MD) virus (MDV)-and gallid alphaherpesvirus 3 is required for horizontal transmission in chickens. Since gC is conserved within the Alphaherpesvirinae subfamily, we hypothesized that gC was also essential for the horizontal transmission of meleagrid alphaherpesvirus 1 (MeAHV1) or turkey herpesvirus (HVT). To test this hypothesis, we generated a fluorescent protein-tagged clone of recombinant (r)HVT (vHVT47G), removed the open reading frame of HVT gC from the genome (vHΔgC), and rescued the deletion by inserting an HA-epitope tagged HVT gC (vHΔgC-R) to test their ability to transmit in chickens and turkeys. We also tested whether MDV gC could compensate for HVT gC during transmission, where HVT gC was replaced with MDV gC (vH-MDVgC). Although all viruses replicated in chickens, none spread from chicken to chicken. However, when tested in turkeys, all viruses except vHΔgC transmitted from turkey to turkey. Importantly, the rescuent virus (vHΔgC-R) and HVT expressing MDV gC (vH-MDVgC) rescued transmission, showing that HVT gC is required and MDV gC can compensate for HVT gC for turkey-to-turkey transmission. These data confirm the host-specific transmission of HVT in turkeys and suggest that the essential function of alphaherpesvirus gC proteins is conserved. This information can be exploited while generating future vaccines against MD that will affect the poultry industry worldwide.