Fos Facilitates Gallid Alpha-Herpesvirus 1 Infection by Transcriptional Control of Host Metabolic Genes and Viral Immediate Early Gene

MAPK pathway orchestrates gallid alphaherpesvirus 1 infection through the biphasic activation of MEK/ERK and p38 MAPK signaling

Therapies targeting virus-host interactions are seen as promising strategies for treating gallid alphaherpesvirus 1 (ILTV) infection. Our study revealed a biphasic activation of two MAPK cascade pathways, MEK/ERK and p38 MAPK, as a notably activated host molecular event in response to ILTV infection. It exhibits antiviral functions at different stages of infection. Initially, the MEK/ERK pathway is activated upon viral invasion, leading to a broad suppression of metabolic pathways crucial for ILTV replication, thereby inhibiting viral replication from the early stage of ILTV infection. As the viral replication progresses, the p38 MAPK pathway activates its downstream transcription factor, STAT1, further hindering viral replication. Interestingly, ILTV overcomes this biphasic antiviral barrier by hijacking host p38-AKT axis, which protects infected cells from the apoptosis induced by infection and establishes an intracellular equilibrium conducive to extensive ILTV replication. These insights could provide potential therapeutic targets for ILTV infection.

Integrative RNA-seq and ChIP-seq analysis unveils metabolic regulation as a conserved antiviral mechanism of chicken p53

The tumor suppressor p53, primarily functioning as a transcription factor, has exhibited antiviral capabilities against various viruses in chickens, including infectious bursal disease virus (IBDV), avian leukosis virus subgroup J (ALV-J), and avian infectious laryngotracheitis virus (ILTV). Nevertheless, the existence of a universal antiviral mechanism employed by chicken p53 (chp53) against these viruses remains uncertain. This study conducted a comprehensive comparison of molecular networks involved in chp53's antiviral function against IBDV, ALV-J, and ILTV. This was achieved through an integrated analysis of ChIP-seq data, examining chp53's genome-wide chromatin occupancy, and RNA-seq data from chicken cells infected with these viruses. The consistent observation of chp53 target gene enrichment in metabolic pathways, confirmed via ChIP-qPCR, suggests a ubiquitous regulation of host cellular metabolism by chp53 across different viruses. Further genome binding motif conservation analysis and transcriptional co-factor prediction suggest conserved transcriptional regulation mechanism by which chp53 regulates host cellular metabolism during viral infection. These findings offer novel insights into the antiviral role of chp53 and propose that targeting the virus-host metabolic interaction through regulating p53 could serve as a universal strategy for antiviral therapies in chickens.IMPORTANCEThe current study conducted a comprehensive analysis, comparing molecular networks underlying chp53's antiviral role against infectious bursal disease virus (IBDV), avian leukosis virus subgroup J (ALV-J), and avian infectious laryngotracheitis virus (ILTV). This was achieved through a combined assessment of ChIP-seq and RNA-seq data obtained from infected chicken cells. Notably, enrichment of chp53 target genes in metabolic pathways was consistently observed across viral infections, indicating a universal role of chp53 in regulating cellular metabolism during diverse viral infections. These findings offer novel insights into the antiviral capabilities of chicken p53, laying a foundation for the potential development of broad-spectrum antiviral therapies in chickens.

Characterization of the Effects of Host p53 and Fos on Gallid Alpha Herpesvirus 1 Replication

Treatment options for herpesvirus infections that target the interactions between the virus and the host have been identified as promising. Our previous studies have shown that transcription factors p53 and Fos are essential host determinants of gallid alpha herpesvirus 1 (ILTV) infection. The impact of p53 and Fos on ILTV replication has 'not been fully understood yet. Using the sole ILTV-permissive chicken cell line LMH as a model, we examined the effects of hosts p53 and Fos on all phases of ILTV replication, including viral gene transcription, viral genome replication, and infectious virion generation. We achieved this by manipulating the expression of p53 and Fos in LMH cells. Our results demonstrate that the overexpression of either p53 or Fos can promote viral gene transcription at all stages of the temporal cascade of ILTV gene expression, viral genome replication, and infectious virion production, as assessed through absolute quantitative real-time PCR, ILTV-specific RT-qPCR assays, and TCID50 assays. These findings are consistent with our previous analyses of the effects of Fos and p53 knockdowns on virus production and also suggest that both p53 and Fos may be dispensable for ILTV replication. Based on the synergistic effect of regulating ILTV, we further found that there is an interaction between p53 and Fos. Interestingly, we found that p53 also has targeted sites upstream of ICP4, and these sites are very close to the Fos sites. In conclusion, our research offers an in-depth understanding of how hosts p53 and Fos affect ILTV replication. Understanding the processes by which p53 and Fos regulate ILTV infection will be improved by this knowledge, potentially paving the way for the development of novel therapeutics targeting virus-host interactions as a means of treating herpesvirus infections.

PcTrim prevents early infection with white spot syndrome virus by inhibiting AP1-induced endocytosis

Viruses have evolved various strategies to achieve early infection by initiating transcription of their own early genes via host transcription factors, such as NF-κb, STAT, and AP1. How the host copes with this immune escape has been a topic of interest. Tripartite motif (TRIM) family proteins with RING-type domains have E3 ubiquitin ligase activity and are known as host restriction factors. Trim has been reported to be associated with phagocytosis and is also believed to be involved in the activation of autophagy. Preventing the virus from entering the host cell may be the most economical way for the host to resist virus infection. The role of TRIM in the early stage of virus infection in host cells remains to be further interpreted. In the current study, a crayfish TRIM with a RING-type domain, designated as PcTrim, was significantly upregulated under white spot syndrome virus (WSSV) infection in the red swamp crayfish (Procambarus clarkii). Recombinant PcTrim significantly inhibited WSSV replication in crayfish. RNAi targeting PcTrim or blocking PcTrim with an antibody promoted WSSV replication in crayfish. Pulldown and co-IP assays showed that PcTrim can interact with the virus protein VP26. PcTrim restricts the expression level of dynamin, which is involved in the regulation of phagocytosis, by inhibiting AP1 entry into the nucleus. AP1-RNAi effectively reduced the expression levels of dynamin and inhibited host cell endocytosis of WSSV in vivo. Our study demonstrated that PcTrim might reduce early WSSV infection by binding to VP26 and then inhibiting AP1 activation, resulting in reduced endocytosis of WSSV in crayfish hemocytes. Video Abstract.

Transcriptome-wide N6-methyladenosine modification profiling of mRNAs during infection of Newcastle disease virus in chicken macrophages

N6-methyladenosine (m6A) modification, the most prevalent post-transcriptional modification of eukaryotic mRNAs, is reported to play a crucial role in viral infection. However, the role of m6A modification during Newcastle disease virus (NDV) infection has remained unclear. In this study, we performed MeRIP-seq to investigate the transcriptome-wide m6A methylome and m6A-modified genes in NDV-infected chicken macrophages. A total of 9496 altered peaks were identified, of which 7015 peaks were significantly upregulated across 3320 genes, and 2481 peaks were significantly down-regulated across 1264 genes. Combined analysis of m6A peaks and mRNA expression showed that 1234 mRNAs had significantly altered levels of methylation and expression after NDV infection, and m6A modification tended to have a negative relationship with mRNA expression, suggesting that m6A modification may regulate the process of NDV infection by regulating gene expression, particularly of the genes important in the innate immune response. To the best of our knowledge, this is the first comprehensive characterization of m6A patterns in chicken macrophage mRNA after NDV infection, providing a valuable basis for further exploring the role of m6A modification mechanisms during the course of NDV infection.

Molecular and genetic detection of infectious laryngeotrachitis disease virus in broiler farms after a disease outbreak in Egypt

Infectious laryngotracheitis (ILT) is a viral respiratory illness in poultry that causes massive financial losses. This research aimed to isolate and identify the ILT virus in suspected outbreaks of broiler flocks in Egypt during 2020-2021, besides investigating its genetic link with other circulating strains. Real-time-PCR was used to test 57 samples taken from unvaccinated broiler farms. Ten samples are positive for ILTV, and the virus is being isolated in SPF chicken embryos. The Sanger sequencing was used to conduct (partial) sequencing of the infected cell protein4 gene (ICP4) for eight isolates. Phylogenetic analysis conducted Maximum Likelihood, comparative sequencing analysis of ICP4 of strains under study with vaccination ILT reference strains reveled that all isolates were clustered into two major groups. The (OM291843and OM291846) clustered together with the chicken embryo origin vaccine strains (IV and V group). The remaining six strains belong to the TCO vaccine(I, II and III group). The total sequence similarity between the strains under study and the various Egyptian strains varied from (97 to 100%) while the similarity with TCO or chicken embryo origin -vaccine strains ranged from (95to 100%). There were no deletions detected in the 272-283-bp region of the ICP4 gene. Detection of arginine to methionine substitutions at position 180 (R180M) and change of Serine to Asparagine at position 227 (S227N) in the (OM291843 and OM291846) which were previously described in chicken embryo origin -vaccine strains. This reveals that field strains may have evolved from vaccine strains, notably identification of non-synonymous substitutions which might be linked to the virulence strains' attenuation. Finally, independent of geographical distribution, both chicken embryo origin-vaccine-like and TCO-Vaccine-like virus strains were circulating in Egyptian non-vaccinated broiler flocks in 2020 and 2021. Despite their genetic differences, both viruses caused significant illnesses in the field.

Characterization of chicken p53 transcriptional function via parallel genome-wide chromatin occupancy and gene expression analysis

The tumor suppressor p53, which acts primarily as a transcription factor, can regulate infections from various viruses in chickens. However, the underlying mechanisms of the antiviral functions of chicken p53 (chp53) remain unclear due to the lack of detailed information on its transcriptional regulation. Here, to gain comprehensive insights into chp53 transcriptional regulatory function in a global and unbiased manner, we determined the genome-wide chromatin occupancy of chp53 by chromatin immunoprecipitation, which was followed by sequencing and chp53-mediated gene expression profile by RNA sequencing using chemically immortalized leghorn male hepatoma (LMH) cells with ectopic expression of chp53 as the model. The integrated parallel genome-wide chromatin occupancy and gene expression analysis characterized chp53 chromatin occupancy and identified 754 direct target genes of chp53. Furthermore, functional annotation and cross-species comparative biological analyses revealed the conserved key biological functions and DNA binding motifs of p53 between chickens and humans, which may be due to the consensus amino acid sequence and structure of p53 DNA-binding domains. The present study, to our knowledge, provides the first comprehensive characterization of the chp53 transcriptional regulatory network, and can possibly help to improve our understanding of p53 transcriptional regulatory mechanisms and their antiviral functions in chickens.

Biological Characteristics of Infectious Laryngotracheitis Viruses Isolated in China

Infectious laryngotracheitis virus (ILTV) causes severe respiratory disease in chickens and results in huge economic losses in the poultry industry worldwide. To correlate the genomic difference with the replication and pathogenicity, phenotypes of three ILTVs isolated from chickens in China from 2016 to 2018 were sequenced by high-throughput sequencing. Based on the entire genome, the isolates GD2018 and SH2017 shared 99.9% nucleotide homology, while the isolate SH2016 shared 99.7% nucleotide homology with GD2018 and SH2017, respectively. Each virus genome contained 82 ORFs encoding 77 kinds of protein, 31 of which share the same amino acid sequence in the three viruses. GD2018 and SH2017 shared 57 proteins with the same amino acid sequence, while SH2016 shared 42 and 41 proteins with the amino acid sequences of GD2018 and SH2017, respectively. SH2016 propagated efficiently in allantoic fluid and on chorioallantoic membranes (CAMs) of SPF chicken embryo eggs, while GD2018 and SH2017 proliferated well only on CAMs. GD2018 propagated most efficiently on CAMs and LMH cells among three isolates. SH2016 caused serious clinical symptoms, while GD2018 and SH2017 caused mild and moderate clinical symptoms in chickens, although the sero of the chickens infected with those three isolates were all positive for anti-ILTV antibody at 14 and 21 days after challenge. Three ILTVs with high genetic homology showed significant differences in the replication in different culture systems and the pathogenicity of chickens, providing basic materials for studying the key determinants of pathogenicity of ILTV.