Molecular Signatures in Swine Innate and Adaptive Immune Responses to African Swine Fever Virus Antigens p30/p54/CD2v Expressed Using a Highly Efficient Semliki Forest Virus Replicon System.

African swine fever virus (ASFV) causes a devastating viral hemorrhagic disease in domestic pigs and Eurasian wild boars, posing a foremost threat to the swine industry and pig farming. The development of an effective vaccine is urgently needed, but has been hampered by the lack of an in-depth, mechanistic understanding of the host immune response to ASFV infection and the induction of protective immunity. In this study, we report that immunization of pigs with Semliki Forest Virus (SFV) replicon-based vaccine candidates expressing ASFV p30, p54, and CD2v, as well as their ubiquitin-fused derivatives, elicits T cell differentiation and expansion, promoting specific T cell and humoral immunity. Due to significant variations in the individual non-inbred pigs in response to the vaccination, a personalized analysis was conducted. Using integrated analysis of differentially expressed genes (DEGs), Venn, KEGG and WGCNA, Toll-like receptor, C-type lectin receptor, IL17 receptor, NOD-like receptor and nucleic acid sensor-mediated signaling pathways were demonstrated to be positively correlated to the antigen-stimulated antibody production and inversely correlated to the IFN-γ secreting cell counts in peripheral blood mononuclear cells (PBMCs). An up-regulation of CIQA, CIQB, CIQC, C4BPA, SOSC3, S100A8 and S100A9, and down-regulation of CTLA4, CXCL2, CXCL8, FOS, RGS1, EGR1 and SNAI1 are general in the innate immune response post-the second boost. This study reveals that pattern recognition receptors TLR4, DHX58/DDX58 and ZBP1, and chemokines CXCL2, CXCL8 and CXCL10 may play important roles in regulating this vaccination-stimulated adaptive immune response.

Expression and Immunogenicity of Recombinant African Swine Fever Virus Proteins Using the Semliki Forest Virus.

African swine fever virus (ASFV) is a large DNA virus belonging to the Asfarviridae family that damages the immune system of pigs, resulting in the death or slaughter of millions of animals worldwide. Recent modern techniques in ASFV vaccination have highlighted the potential of viral replicon particles (RPs), which can efficiently express foreign proteins and induce robust cellular and humoral immune responses compared with the existing vaccines. In this study, we established a Semliki Forest virus (SFV) vector by producing replication-defective viral particles. This vector was used to deliver RPs expressing ASFV antigens. SFV-RPs expressing ASFV p32 (SFV-p32) and p54 (SFV-p54) were tested in baby hamster kidney (BHK-21) cells. Proteins expression was evaluated via western blotting and indirect immunofluorescence, while immunogenicity was evaluated in BALB/c mice. The resulting RPs exhibited high levels of protein expression and elicited robust humoral and cellular immune responses.