Poultry farming is one of the pillar industries of global animal husbandry. In order to guarantee production, poultry are frequently vaccinated from the moment they are hatched. Even so, the initial immunity of chicks is still very poor as they are in the “window period” of immune protection. In ovo vaccination pushes the initial immunization time forward to the incubation period, thereby providing earlier immune protection for chicks. In ovo vaccination is currently a research hotspot of poultry disease prevention and control, which is in line with the intensification of poultry production. However, the vaccines currently available for in ovo vaccination are limited and cannot meet the needs of industrial development, so how to efficiently activate the adaptive immune response of chicken embryos becomes the key to restrict product development and technological progress of in ovo vaccination. Its breakthrough, to a large extent, depends on systematic illustration of the mechanism underlying the adaptive immune response post immunization. Clarification of this issue will provide us with theoretical support and potential solutions for the development of novel vaccines for in ovo vaccination, the augmentation of efficacy of current vaccines and the optimization of immune programs.

Infectious laryngotracheitis virus (ILTV) exhibits a cascade expression pattern of encoded genes, and ICP4 is the only immediate-early gene of ILTV, which plays a crucial role in initiating the subsequent viral genes. Therefore, studying the transcriptional regulation mechanism of ICP4 holds promise for effectively blocking ILTV infection and spread. Host transcriptional factors p53 and Fos are proven to regulate a variety of viral infections, and our previous studies have demonstrated their synergistic effects in regulating ILTV infection. In this study, we constructed eukaryotic expression vectors for p53 and Fos as well as their specific siRNAs and transfected them into a chicken hepatoma cell line. The results showed that knocking down p53 or Fos significantly inhibited ICP4 transcription, while overexpressing p53 or Fos had an opposite effect. A further CoIP and ChIP-qPCR assay suggested p53 and Fos physically interacted with each other, and jointly bound to the upstream transcriptional regulatory region of ICP4. To elucidate the specific mechanisms of p53 and Fos in regulating ICP4 transcription, we designed p53 and Fos protein mutants by mutating their DNA binding domains, which significantly reduced their binding ability to DNA without affecting their interaction. The results showed that Fos directly bound to the promoter region of ICP4 as a binding target of p53, and the p53–Fos protein complex acted as a transcriptional co-regulator of ICP4. Studying the transcriptional process and regulatory pattern of ICP4 is of great significance for understanding the molecular mechanism of ILTV infection, and thus for finding effective methods to control and prevent it.

Infectious laryngotracheitis virus (ILTV), formally known as Gallid alphaherpesvirus 1, represents a prominent alphaherpesvirus that poses a significant threat to the global poultry industry. Current routine vaccination strategies fail to eliminate latent infection. Host–pathogen interaction networks have become a key focus in antiviral research. Our previous study demonstrated that activation of the MEK/ERK signaling pathway upon ILTV infection restricts host cellular metabolic activity to mount protective host antiviral responses, yet the underlying molecular mechanism remains unclear. The present work systematically dissects the contribution of MEK/ERK signaling to intrinsic host defense against ILTV. The results show that ILTV infection activates the MEK/ERK pathway, which in turn promotes the expression, activation, and nuclear translocation of the transcription factor Fos. As a core transcriptional regulator, Fos represses host metabolic gene expression, thereby restricting viral replication and proliferation. Integrated multi-omics analyses further demonstrate that the MEK/ERK-Fos-metabolic regulatory axis operates uniformly during infection with avian, human, and porcine alphaherpesviruses, suggesting a broadly conserved host antiviral mechanism. This consistent cross species signaling pattern points toward an evolutionarily conserved host antiviral strategy and provides potential molecular targets for the development of broad-spectrum antiviral strategies against alphaherpesviruses.