Identification of swine influenza virus epitopes and analysis of multiple specificities expressed by cytotoxic T cell subsets

Abstract

Background: Major histocompatibility complex (MHC) class I peptide binding and presentation are essential for antigen-specific activation of cytotoxic T lymphocytes (CTLs) and swine MHC class I molecules, also termed swine leukocyte antigens (SLA), thus play a crucial role in the process that leads to elimination of viruses such as swine influenza virus (SwIV). This study describes the identification of SLA-presented peptide epitopes that are targets for a swine CTL response, and further analyses multiple specificities expressed by SwIV activated CTL subsets.

Findings: Four SwIV derived peptides were identified as T cell epitopes using fluorescent influenza:SLA tetramers. In addition, multiple CTL specificities were analyzed using peptide sequence substitutions in two of the four epitope candidates analyzed. Interestingly both conserved and substituted peptides were found to stain the CD4-CD8+ T cell subsets indicating multiple specificities.

Conclusions: This study describes a timely and cost-effective approach for viral epitope identification in livestock animals. Analysis of T cell subsets showed multiple specificities suggesting SLA-bound epitope recognition of different conformations.

Figure 1

Influenza virus tetramer staining of porcine CD4 ^- CD8 α ^high T cells. SwIV tetramer staining of CD4^-CD8α^high T cell subsets. Individual samples were stained by an epitope candidate tetramer (GTEKLTITY) and a negative control tetramer (ASYGAGAGY). Singlet lymphocytes are gated in P1 (blue). CD4^-CD8α^high cells are gated in P2 (orange), and CD4^-CD8α^high APC⁺BV⁺ tetramer double positive cells are shown in P3 (green) for animal number 4. Percentages of tetramer reactive cells within the CD4^-CD8α^high population are shown for each sample.