The kinetics of gene expression related to innate and adaptive immunity in the lung and spleen following Newcastle disease virus (NDV) infection in vaccinated broiler chickens employing different vaccination regimes

Abstract

Newcastle disease virus (NDV) classified as an avian paramyxovirus-1 poses a significant risk to the global poultry sector. This study explored the kinetics of the innate and adaptive immune responses in chickens exposed to virulent Newcastle Disease Virus (vNDV) genotype VII. A challenge experiment was carried out with both non-vaccinated and NDV-vaccinated chickens utilizing different vaccination strategies commonly used in the industry. The four groups of vaccinated birds were administered either two doses of live NDV vaccines, live vaccines boosted with an inactivated vaccine, the rHVT-NDV-IBDV vaccine alone, or the rHVT-NDV-IBDV vaccine in conjunction with a live vaccine booster. To assess seven cytokines linked to antiviral and proinflammatory innate responses quantitative real-time polymerase chain reaction (qRT-PCR) analyses were implemented. The analyses revealed robust innate immune responses in all cytokines measured in lung and spleen tissues of the group that received both live and inactivated vaccines. Notably these increases were found to correlate with the humoral immune response within that same group. Significant transcriptional activity in the lung and spleen tissues of non-vaccinated chickens at 24 hour post-infection (pi). The most significant upregulations were identified in toll-like receptor 7 (TLR7), TLR5, interleukin 6 (IL6), chicken interferon-alpha (chIFN-α), and myxovirus resistance protein 1 (Mx1), which later exhibited a regression. The administration of both live and inactivated vaccines has proven effective in restoring the suppression or inhibition of vNDV infection across a wide range of cytokines, including TLR7, TLR5, chIFN-α, Mx1, IL6, and MHC-1. Various vaccination strategies have been shown to either mitigate or prevent cytokine storms within 24 hour pi in the lungs, spleen, or both, in certain cytokines such as chIFN-α, Mx1, and IL6. Collectively these results suggest that different vaccination strategies modify the kinetics and pathophysiological responses associated with vNDV infection in chickens.

Keywords: Chicken; IL6; Innate; MHC-1; Newcastle disease virus; TLR; Vaccine.