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This study set to delineate MHC class II immunogenic peptides encoded in proteins expressed by A33R, 14 kDa fusion protein and p42 genes of ectromelia virus (ECTV) Moscow strain (ECTV-Mos), a virus related to variola virus (Variola vera virus) responsible for smallpox in humans. A search for a safe and efficacious vaccine against poxviruses is still required mostly because of the emerging nature of certain viruses among poxviruses. In silico prediction of peptides from the 3 protein sequences revealed 6 potential candidates. Investigations included assessment of the peptide’s ability to bind to MHC class II molecules on antigen-presenting cells and to induce the proliferation, cytokine synthesis and cytotoxicity of CD4⁺ T cells originating from mice previously infected with ECTV-Mos. The results show that peptide ENHAETLRAAMISLA (Pep3) predicted from the protein sequence 14 kDa fusion protein induced significant proliferation, cytokine synthesis and cytotoxicity. Also Pep3 was able to bind strongly to MHC class II molecules on A20 cells. These results suggest that a small population of CD4⁺ T cells play a protective role dependent on cytotoxicity and possibly complement the CD8⁺ T cells population in this regard.
Gamma/delta (γδ) T cells in cattle account for an abundant T cell population. However, little is known regarding the function of γδ T cells as immune cells compared to αβ T cells. Not many pathogen-related antigens have been defined and known to stimulate γδ T cells. To address this information gap, we constructed a soluble receptor for bovine γδ T cells (sγδTCR) that was later used to identify two proteins (156 kDa and 102 kDa) or protein fragments expressed by bovine coronavirus (BCov). The molecular weight of the larger protein suggests it could be the spike glycoprotein of BCov. Subsequently, we used the identified viral proteins to study the reactivity of bovine γδ T cells. In vitro assays showed that purified preparations of the two proteins stimulated WC1+ γδ T cells isolated from cattle. A 4-fold increase in IFNγ production and a significantly higher expression of MHC class II was observed. However, these viral ligands could not stimulate γδ T cells to synthesize IL-8 or GM-CSF, known to be produced by γδ T cells when stimulated with bacterial antigens. Although the γδ T cells assessed here appeared activated by way of IFNγ and MHC II expression, surface markers such as CD2, CD25, CD44, CD62L and CD335 were not expressed at significant levels. Further, the activation elicited by viral ligands was not sufficient to induce cytotoxic capability in γδ T cells in vitro as measured by a flow cytometrybased cytotoxicity assay. This in vitro study shows that WC1+ γδ T cells can directly recognize viral antigen.
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