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

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.

SUBMITTER: Rojas JM

PROVIDER: S-EPMC5492282 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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

Rojas José-Manuel JM Rodríguez-Calvo Teresa T Sevilla Noemí N

Veterinary research 20170629 1

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<sup>+</sup> and CD8<sup>+</sup> T cell responses during primary and recall responses. During primary immune responses, ...[more]

PMID: 28662714

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Project description:Bluetongue virus (BTV), the prototypical Orbivirus that belongs to the Sedoreoviridae family, is transmitted by the bite of infected Culicoides midges and affects domestic and wild ruminants producing great economic losses. The infection induces an IFN response, followed by an adaptive immune response that plays a critical role in disease clearance. BTV can nonetheless impair IFN and humoral responses. The main goal of this study was to gain a more detailed understanding of BTV pathogenesis and its effects on immune cell populations. To this end, we combined flow cytometry and transcriptomic analyses of several immune cells at different times post-infection (pi). Four sheep were infected with BTV serotype 8 and blood samples collected at days 0, 3, 7 and 15pi to isolate peripheral blood mononuclear cells. Transcriptomic analysis of B-cell marker+, CD4+, CD8+, and CD14+ sorted cells showed that the maximum number of differentially expressed genes occurred at day 7pi, which coincided with the peak of infection. KEGG pathway enrichment analysis in B-cell marker+, CD4+, and CD14+ cells indicated that genes belonging to virus sensing and immune response initiation pathways were enriched and day 3 and 7 pi. Transcriptomic analysis also showed that T cell exhaustion pathway was enriched in CD4+ cells at day 7pi, while CD8+ cells showed downregulated immune response initiation pathways at this timepoint. When T cell functionality was assessed, ELISpot assays, intracellular cytokine staining, and proliferation assays demonstrated that BTV produced an acute inhibition of CD4+ and CD8+ T cell activation at the peak of replication. Furthermore, this coincided with PD-L1 upregulation on the surface of CD4+ and CD8+ T cells as well as monocytes. Taken together, these data indicate that BTV exploits the PD1/PD-L1 immune checkpoint to impair T cell responses. These findings identify several mechanisms in the interaction between host and BTV, which could help develop better tools to combat the disease.

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

Publications

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

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