Marek's disease virus (MDV) leads to a lytic
infection of B-lymphocytes in chickens, and also latently infects T-lymphocytes. Although
Marek's disease vaccines have been widely in use, little is known about the innate immune response of this important livestock
vaccine. In this study, we tested the effect of different commercially applied
Marek's disease vaccines on the expression pattern of selected genes related to chicken
interferon-alpha (chIFN-α) (
melanoma differentiation associated gene 5 "MDA5″ dependent) signal transduction pathway. Both MDV serotype I (Rispens) and serotype III (Herpesvirus of turkey "HVT")
vaccines could stimulate MDA5 dependent-
type I interferon response as early as three days post vaccination in a dose-dependent manner. The stimulation continued up to 10 days in the instance of HVT
vaccine and declined in the case of Rispens. Surprisingly, increasing the doses of the two
vaccines led to dose-dependent down-regulation in the expression pattern of the investigated pathway, five and ten days post vaccination. Additionally, to shed the light on the consequent effect on the immune responses of the other
viral vaccine, another experimental model based on Newcastle disease virus (NDV)
vaccines was designed using HVT, HVT-VP2 and Rispens MDV
vaccines. The three MDV
vaccines were found to reduce chicken humoral immune response post NDV vaccination. However, only Rispens and HVT-VP2 had suppressive effects on the expression of MDA5-dependent-chIFN-α related
cytokines. Consistent with this finding, the protection rate and NDV- humoral immune response post challenge with virulent NDV strain was lower in case of Rispens and HVT-VP2
vaccines.