Oral Presentation 12th Australasian Virology Society Meeting 2024

New Insights Into Immune Dysregulation Following Infection of Domestic Pigs With Virulent African Swine Fever Virus (#56)

Samantha K Davis 1 , Rachel Layton 1 , Andrea Certoma 1 , Lenny Izzard 1 , Daniel Layton 1 , Jonathan E Allen 2 , James B Thissen 3 , John Bingham 1 , Brenton Rowe 1 , John R White 1 , James W Wynne 1 , Dayna Johnson 1 , Matthew J Neave 1 , Natasha N Gaudreault 4 , Crystal Jaing 3 , Raymond R Rowland 5 , David T Williams 1
  1. Australian Centre for Disease Preparedness (ACDP), CSIRO, Geelong, Victoria, Australia
  2. Computations Directorate, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
  3. Physical & Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, United States of America
  4. Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, KS, United States of America
  5. College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America

African swine fever (ASF) is fatal in almost 100% of infected pigs. The ASF virus (ASFV) expresses many viral immunomodulators, making development of a safe and effective vaccine difficult. Here we aimed to understand the systemic disease state of ASFV using bulk RNAseq and characterise the impact of ASFV infection on cellular immunity using flow cytometry. We assessed the systemic transcriptome of pigs (n = 3) infected with a moderately virulent ASFV isolate (Malta/78), using bulk RNAseq. Whole blood specimens collected on days 0, 3, 6, 13 post-inoculation (dpi), and at clinical endpoints were compared to identify differentially expressed genes and gene pathways. Transcriptional activity peaked at 6dpi, coinciding with peak viremia. Notably, no significant changes in Type I IFN related genes were observed in this study. Several cell death associated genes/pathways were significantly upregulated between 6 and 13dpi, while genes associated with antigen presentation were significantly downregulated at 6dpi. Furthermore, genes associated with T-cell receptor signalling were significantly upregulated at 6dpi, however this signature was absent by 13dpi. Upregulation of immunoregulatory genes associated with regulatory T-cells, including IL-10, combined with downregulation of genes for cytokines involved in T-cell activation (IL-1A and IL-18), indicates T-cell dysfunction during infection. Using flowcytometry, we also investigated the phenotype of immune subsets of bio-banked PBMC samples of pigs (n = 6) infected with a highly virulent ASFV isolate (Georgia/07). Notably, we observed a reduction in total cell counts of several subsets, including B-cells and CD4+ T-cells between 4 and 6dpi and MHC-II positive cells at 6dpi consistent with upregulation of cell death gene pathways and downregulation of genes related to antigen presentation. Overall, this data further highlights systemic dysregulation of the host immune response at the transcriptional and cellular level following virulent ASFV infection, providing a basis for rational design of vaccines and therapeutics.