Abstract
Vaccination with live attenuated classical swine fever virus (CSFV) vaccines induces a rapid onset of protection which has been associated with virus-specific CD8 T cell IFN-γ responses. In this study, we assessed the specificity of this response, by screening a peptide library spanning the CSFV C-strain vaccine polyprotein to identify and characterise CD8 T cell epitopes. Synthetic peptides were pooled to represent each of the 12 CSFV proteins and used to stimulate PBMC from four pigs rendered immune to CSFV by C-strain vaccination and subsequently challenged with the virulent Brescia strain. Significant IFN-γ expression by CD8 T cells, assessed by flow cytometry, was induced by peptide pools representing the core, E2, NS2, NS3 and NS5A proteins. Dissection of these antigenic peptide pools indicated that, in each instance, a single discrete antigenic peptide or pair of overlapping peptides was responsible for the IFN-γ induction. Screening and titration of antigenic peptides or truncated derivatives identified the following antigenic regions: core241–255 PESRKKLEKALLAWA and NS31902–1912 VEYSFIFLDEY, or minimal length antigenic peptides: E2996–1003 YEPRDSYF, NS21223–1230 STVTGIFL and NS5A3070–3078 RVDNALLKF. The epitopes are highly conserved across CSFV strains and variable sequence divergence was observed with related pestiviruses. Characterisation of epitope-specific CD8 T cells revealed evidence of cytotoxicity, as determined by CD107a mobilisation, and a significant proportion expressed TNF-α in addition to IFN-γ. Finally, the variability in the antigen-specificity of these immunodominant CD8 T cell responses was confirmed to be associated with expression of distinct MHC class I haplotypes. Moreover, recognition of NS21223–1230 STVTGIFL and NS31902–1912 VEYSFIFLDEY by a larger group of C-strain vaccinated animals showed that these peptides could be restricted by additional haplotypes. Thus the antigenic regions and epitopes identified represent attractive targets for evaluation of their vaccine potential against CSFV.
Highlights
Classical swine fever (CSF) is a severe and often lethal viral disease of domestic pigs and wild boars
Despite presenting the porcine immune system with a polyprotein of almost 4000 amino acids in length, this study has shown that the CD8 T cell response to classical swine fever virus (CSFV) is highly focussed, dominated by only one or two epitopes each located on five different viral antigens
Low resolution swine leukocyte antigen (SLA) class I typing suggested that pig AN5 carried haplotype 4.0 and this was confirmed by allele specific PCR
Summary
Classical swine fever (CSF) is a severe and often lethal viral disease of domestic pigs and wild boars. Epitopes may be located on other viral proteins, since peptides pooled to represent Erns, E1, NS2, NS4B and NS5A were able to induce PBMC proliferation in vaccinated pigs, but their ability to elicit an IFN-c or cytotoxic response was not tested [9]. Most of these studies utilised inbred homozygous pigs so were focussed on a single haplotype [7,9,10] and the phenotype of the responding T cells/MHC restriction was not or only partially characterized [6,7,8,9,10]. The conservation of these peptides across CSFV strains was assessed as were the restricting MHC class I haplotypes and the CSFV-specific T cells responding were phenotypically and functionally characterized
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
