| dc.description.abstract | Newcastle disease (ND) is a viral disease causing severe economic losses. The extensive use of currently available ND vaccines and biosecurity appears to keep NDV under control in developed countries. However, current vaccination strategies are not fully effective under different environmental conditions. The development of new concepts for generating new ND vaccines is needed to effectively control NDV infection. The present study aimed to identify genes and mechanisms contributing to different light regimes by studying the innate immune response in chick embryos after ND virus challenge. The innate immune system of chick embryos becomes immunocompetent pre-hatching. By using chick embryos, experimental costs will be significantly reduced with larger sample sizes, minimal biosecurity is required, and the effects of confounding variables will be minimized. This study first validated the optimum pH to deliver the NDV vaccine. The results showed that the minimum reduction in NDV infectivity titer was recorded in pH 7.00 diluent held on ice. Second, by using chick embryos, we were able to uncover the immune response to in ovo ND virus challenge in three different lighting regimes (dark 0L:24D, blue 12L:12D, and white 12L:12D). This determined the highest virus Fold change (FC) occurs 36-h post-ND virus challenge, the dark treatment (2.84 FC) had a significantly higher virus FC than blue and white light treatments (1.03 and 1.73 FC, respectively) (P < 0.01). At 96-h post-challenge, the blue treatment had the lowest viral FC (0.11 FC), and the dark treatment had the highest viral FC (0.73 FC) (P < 0.05). The transcriptional response of innate immune genes is differentially expressed in blue light treatment versus dark and white light treatments. The comparison between the dark and blue light treatments validated that they have similar differences in some immune responses by expressing similar genes in both treatments; however, both lighting treatments respond differently in viral particle enumerations. Through these studies, we were able to propose a panel of genes that are associated with the innate immune response under different light regimes, which constitutes the first line of viral defense against NDV and relies on a large family of pattern recognition receptors (PRRs), including TLR 7, which detect the viral single-stranded RNA, termed pathogen-associated molecular patterns (PAMPs). Overall, this study has provided a new tool to examine the innate immune response to NDV. Future studies would benefit from including chick embryos from different breeds and lines as well as examining other poultry pathogens using the chick embryos. | |
