The Role of Porcine Monocyte Derived Dendritic Cells (MoDC) in the Inflammation Storm Caused by Streptococcus suis Serotype 2 Infection.

BACKGROUND: Streptococcus suis is an important swine pathogen and zoonotic agent. Infection with this highly pathogenic strain can cause streptococcal toxic shock-like syndrome (STSLS), characterized by a Th-1 inflammatory cytokine storm, and a high mortality rate. Monocyte derived dendritic cells (MoDCs) are known to stimulate Th-1 cell differentiation, but the role of MoDCs in STSLS remains to be elucidated. METHODOLOGY AND FINDINGS: Porcine CD14-positive monocytes, purified from peripheral blood mononuclear cells (PBMCs), were used to generate MoDCs using granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Highly pure MoDCs were generated, as proved by their morphology, phenotype analysis, phagocytic ability, and induction of T cells proliferation. The MoDCs were further stimulated by the virulent S. suis serotype 2 (SS2) SC19 strain which triggered a strong release of several pro-inflammatory cytokines, including IL-1ß, IL-8, TNF-α, IFN-γ, and IL-12. Furthermore, the stimulated MoDCs induced CD4+ T cell differentiation towards Th-1 cells in vitro. CONCLUSIONS: The results of this study indicated that the porcine MoDCs stimulated by SS2 could release high levels of Th-1 inflammatory cytokines and induce CD4+ T cell differentiation towards Th-1 cells. Hence, it is likely that porcine MoDCs play an important role in the STSLS caused by SS2.

[Induction or inhibition of apoptosis by pseudorabies virus ea strain in suckling piglets].

To study induction or inhibition of apoptosis by pseudorabies virus (PrV) Ea strain in suckling piglets, Aujeszky s disease was replicated by artificially inoculating 15 day-old piglets with PrV-Ea strain. Various tissue sections, such as lymphoid tissues and nervous tissues were collected. Transmission electron microscopy, DNA fragmentation assay, and in situ terminal-deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining were carried to analyze apoptotic cells. It was shown that piglets infected with PrV-Ea strain took on typical clinical symptoms and apoptotic cells were found in lymphoid tissues but not in nerve tissues. The results indicated that the PrV infection caused apoptosis in a big number of lymphatic cells, thus leading to death of suckling piglets due to lowered immune function. It might play an important role in PrV s attack on immune system. A latent infection of pseudorabies virus was established in the neuronal tissue cells by inhibition of nervous cell apoptosis; this might be the way for PrV to establish latent infection, leading to sporadic recurrence of the disease.