Evaluation of vaccine competition using HVT vector vaccines

Authors: DUNN, JOHN - US Department Of Agriculture (USDA)

Submitted to: American Veterinary Medical Association Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/3/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Turkey herpesvirus (HVT) has been widely used as a vaccine for Marek’s disease (MD) since the 1970s. Because HVT is a safe vaccine that is poorly sensitive to interference from maternally derived antibodies, it has seen rising use as a vector for vaccines developed for protection against other common poultry viruses. These recombinant HVT vector (rHVT) vaccines have been shown to offer similar protection against MDV challenge compared to standard HVT vaccination, however, it has been suggested that different rHVT products cannot be combined with each other or with standard HVT due to interference among HVT strains. This study aimed to evaluate competition between similar vaccine strains, an issue that perhaps is just now coming to light as multiple types of very similar vaccines are being mixed together for the first time. Individual HVT and rHVT vaccine strains were compared for replication kinetics both in vitro and in vivo and found to have significant differences in virus loads. Vaccines were classified as either low or high replicating strains. Pairs of rHVT vaccines were then administered together to measure competition based on replication status (high vs. high, low vs. low, and low vs. high). Results of vaccine replication will be presented based on the various rHVT vaccine combinations.