Recall T cell responses to bluetongue virus produce a narrowing of the T cell repertoire

Vet Res. 2017 Jun 29;48(1):38. doi: 10.1186/s13567-017-0444-3.

Abstract

In most viral infections, recall T cell responses are critical for protection. The magnitude of these secondary responses can also affect the CD8 and CD4 epitope repertoire diversity. Bluetongue virus (BTV) infection in sheep elicits a T cell response that contributes to viremia control and could be relevant for cross-protection between BTV serotypes. Here, we characterized CD4+ and CD8+ T cell responses during primary and recall responses. During primary immune responses, both CD4+ and CD8+ T cell populations expanded by 14 days post-infection (dpi). CD4+ T cell populations showed a lower peak of expansion and prolonged contraction phase compared to CD8+ T cell populations. Recall responses to BTV challenge led to BTV-specific expansion and activation of CD8+ but not of CD4+ T cells. The evolution of the BTV-specific TCR repertoire was also characterized in response to VP7 peptide stimulation. Striking differences in repertoire development were noted over the time-course of infection. During primary responses, a broader repertoire was induced for MHC-I and MHC-II epitopes. However, during memory responses, a narrowed repertoire was activated towards a dominant motif in VP7 comprising amino acids 139-291. Monocytes were also examined, and expanded during acute infection resolution. In addition, pro-inflammatory cytokine levels increased after BTV inoculation and persisted throughout the experiment, indicative of a prolonged inflammatory state during BTV infections. These findings could have implications for vaccine design as the narrowing memory T cell repertoire induced after BTV re-infection could lead to the development of protective immunodominant TCR repertoires that differs between individual sheep.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bluetongue / immunology*
  • Bluetongue virus / immunology*
  • CD4-Positive T-Lymphocytes / immunology
  • CD8-Positive T-Lymphocytes / immunology
  • Enzyme-Linked Immunosorbent Assay / veterinary
  • Female
  • Flow Cytometry / veterinary
  • Immunologic Memory / immunology*
  • Real-Time Polymerase Chain Reaction / veterinary
  • Sheep / immunology
  • Sheep / virology
  • T-Lymphocytes / immunology*
  • Viral Load / veterinary