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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Endemic Poultry Viral Diseases Research » Research » Research Project #432152

Research Project: Genetic and Biological Determinants of Avian Herpesviruses Pathogenicity, Transmission, and Evolution to Inform the Development of Effective Control Strategies

Location: Endemic Poultry Viral Diseases Research

Project Number: 6040-32000-074-000-D
Project Type: In-House Appropriated

Start Date: Oct 1, 2016
End Date: Sep 30, 2021

1. Characterize the evolution of avian tumor viruses in poultry production systems, including characterizing the effect of vaccination on the evolution of Marek’s disease virus field strains. 1.1. Characterize the effect of vaccination on the evolution of Marek’s disease virus field strains. 1.2. Surveillance for virulent strains of avian tumor viruses in field flocks and development of improved diagnostics for new strains. 2. Identify host-pathogen interactions that drive the transmission of avian herpesviruses, including identifying viral determinants that drive transmission and determining host genetic effects on virus transmission. 2.1. Host and virus gene expression patterns in the skin cells facilitate production of cell-free enveloped infectious virus particles. 2.2. Determine host genetic effect on virus transmission. 3. Elucidate the genetic and biological mechanisms that drive Marek’s disease resistance, including characterizing and defining innate defense mechanisms that contribute to Marek’s disease resistance. 3.1. Define innate defense mechanisms that contribute to Marek’s disease vaccinal synergy. 4. Discover safe and highly effective vaccine platforms that convey protection against avian herpesviruses, including developing a vaccine strain of Marek’s disease virus serotype 1 that is cell free and does not require liquid nitrogen for storage and shipment, and discovering novel Infectious laryngotracheitis virus (ILTV) vaccine platforms that are safe, efficacious, and cost-effective. 4.1. Develop cell-free Marek’s disease vaccine. 4.2. Generate novel infectious laryngotracheitis virus vaccines.

Marek’s disease (MD) and infectious laryngotracheitis (ILT) are agronomically-important diseases of chickens caused by two alphaherpesviruses, Marek’s disease virus (MDV) and infectious laryngotracheitis virus (ILTV), respectively. Although chickens have been vaccinated against these diseases for decades and though highly successful, the vaccines fail to protect against reinfection and transmission. One significant consequence has been the evolution of more virulent MDV field strains in MD-vaccinated flocks. This vicious cycle of virus evolution followed by introduction of new expensive vaccines is not sustainable in the large, expanding, and highly concentrated chicken meat and egg industries. Another shortcoming of MD vaccination is the requirement for storage and transportation of viable vaccine virus in liquid nitrogen. These vaccines are prone to breaks in vaccine control due to improper handling and have restricted usage on a global basis due to the limits of cold chain processes in developing countries. Since current vaccines fail to induce complete immunity, we plan on investigate the role of innate immunity in preventing MDV infection, identify host and virus determinants involved in transmission that undoubtedly play a role in virus evolution, and define the mechanism by which MDV vaccine strains act synergistically in protective immunity. ILTV vaccines are also imperfect and recent research suggests that not only can they revert to virulence by simple bird-to-bird transmission, but also vaccine strains can recombine to generate new virulent strains. There is a need to engineer better modified-live ILT vaccines incapable of reversion to virulence and subunit vaccines incapable of recombination.