Abstract
Lymphocyte depletion and immunosuppression are typical clinical characteristics of pigs infected with classical swine fever virus (CSFV). The apoptosis of virus-infected and bystander cells plays a role in the immunopathology of classical swine fever (CSF). Here, we offer the first evidence that autophagy is involved in apoptosis and death of T lymphocytes in the spleen of pigs infected with CSFV. Using immunohistochemical assays, we observed that more LC3II-positive cells appear in the T-cell zone of spleens. Spleen cell apoptosis was demonstrated using flow cytometry and TUNEL staining. Confocal immunofluorescence revealed that partial LC3II-positive cells were simultaneously TUNEL-positive. By cultivating spleen cells ex vivo, we demonstrated that the inhibition of autophagy by 3-MA treatment inhibited apoptosis and death of T lymphocytes caused by CSFV infection but did not have this effect on B lymphocytes. Further observations demonstrated that uninfected cells in the spleen were also undergoing autophagy in vivo. In summary, these results linked autophagy with the apoptosis and cell death of splenic T cells, providing a new outlook to understand the mechanism of T lymphocyte depletion and immunosuppression during CSF.
Highlights
Apoptosis, a well-known type I programmed cell death, mediates the elimination of damaged, aberrant or infected cells in multicellular organisms[8]
We demonstrate that autophagy is involved in the apoptosis and death of T lymphocytes in the spleen of pigs infected with classical swine fever virus (CSFV)
Based on the findings that LC3II-positive cells were predominant in the T-cell zone of the spleen (Fig. 3B and D) and that partial LC3II-positive cells were transferase-mediated dUTP nick end labeling (TUNEL)-positive in CSFV-infected spleens (Fig. 4), we assessed whether autophagy played a role in the apoptosis of T lymphocytes in the spleen of pigs infected with CSFV
Summary
A well-known type I programmed cell death, mediates the elimination of damaged, aberrant or infected cells in multicellular organisms[8]. CSFV does not cause the death of alveolar macrophages and even inhibits the apoptosis of primary porcine endothelial cells in in vitro studies[7,11] These controversial results confuse the cell death mechanism of lymphocytes during CSFV infection and raise the possibility that other cell death mechanisms may be involved. We demonstrate that autophagy is involved in the apoptosis and death of T lymphocytes in the spleen of pigs infected with CSFV. This finding provides a new idea for exploring the mechanism of immunosuppression caused by CSFV infection
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