Dual analysis of wild-type and attenuated Orf virus and host cell transcriptomes revealed novel virus-host cell interactions

Abstract

ABSTRACT The attenuated Orf virus (ORFV) strain (aFX0910), derived from continuous passages of wild-type strain FX0910 in vitro , displays obviously lower virulence in kids. However, the latent virulence determinants and intracellular mechanisms for the attenuated variant remain unknown. In this study, we constructed a comprehensive analysis of the ORFV and goat lip fibroblasts transcriptomes during viral infection using RNA sequencing. Focusing on the host transcriptome, we performed gene expression analysis, Gene Ontology analysis, and biological pathway analysis, among others. This integrated analysis allowed us to assess potential changes in mRNA expression and single nucleotide polymorphisms (SNPs) in both viral and host genes. In general, the global patterns of immune gene expression induced by different ORFV isolates were mostly shared. However, host transcripts and non-synonymous of viral genes differed between the wild-type and attenuated ORFV strains. Notably, the natural ORFV isolate (FX0910) predominantly triggered an innate immune response in host cells, while aFX0910 downregulated innate immune response and antiviral response. Analysis of viral transcriptomes manifested that FX0910 and aFX0910 had different SNP events in multiple functional genes. Collectively, our findings highlighted novel insights into virus-host interactions and shed light on the molecular basis of ORFV virulence at the genomic level. Furthermore, this study may contribute to the development of targeted intervention strategies and the advancement of vaccine research in the field of ORFV. IMPORTANCE Currently, the only available commercial vaccines for Orf virus (ORFV) are live attenuated vaccines, which present a potential risk of reversion to virulence. Therefore, understanding the pathogenic mechanisms of different virulent strains of ORFV and host immune responses triggered by these viruses is crucial for developing new vaccines and interventions. In this study, we found that the attenuated strain downregulates the host innate immune response and antiviral activity. In addition, we noted that the wild-type strain can induce the immune response pattern centered on interferon-stimulated genes and interferon regulatory factor gene family. We predicted that STAT1 and STAT2 are the main transcription factors upstream of target gene promoters through gene regulatory networks and exert significant regulatory effects on co-expressed genes. Our study elucidated the complex interaction between ORFV strains and host cell immune responses, providing new insights into vaccine research for ORFV.