Analysis of Porcine Pro- and Anti-Inflammatory Cytokine Induction by <i>S. suis</i> In Vivo and In Vitro

• Main Authors: Florian S. Hohnstein, Marita Meurer, Nicole de Buhr, Maren von Köckritz-Blickwede, Christoph G. Baums, Gottfried Alber, Nicole Schütze
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Pathogens
• Subjects: <i>s. suis</i>; pig; whole-blood model; pbmc; monocytes; interleukin-6; interleukin-10; tumor necrosis factor-alpha; bacterial killing
• Online Access: https://www.mdpi.com/2076-0817/9/1/40

Weaning piglets are susceptible to the invasive <i>Streptococcus (S.) suis</i> infection, which can result in septicemia. The aim of this study was to investigate the cytokine profile induced upon <i>S. suis</i> infection of blood, to determine the cellular sources of those cytokines, and to study the potential effects of the induced cytokines on bacterial killing. We measured TNF-&#945;, IL-6, IFN-&#947;, IL-17A and IL-10 after an experimental intravenous infection with <i>S. suis</i> serotype 2 in vivo, and analyzed whole blood, peripheral blood mononuclear cells (PBMC) and separated leukocytes to identify the cytokine-producing cell type(s). In addition, we used a reconstituted whole blood assay to investigate the effect of TNF-&#945; on bacterial killing in the presence of different <i>S. suis</i>-specific IgG levels. An increase in IL-6 and IL-10, but not in IFN-&#947; or IL-17A, was observed in two of three piglets with pronounced bacteremia 16 to 20 h after infection, but not in piglets with controlled bacteremia. Our results confirmed previous findings that <i>S. suis</i> induces TNF-&#945; and IL-6 and could demonstrate that TNF-&#945; is produced by monocytes in vitro. We further found that IL-10 induction resulted in reduced secretion of TNF-&#945; and IL-6. Rapid induction of TNF-&#945; was, however, not crucial for in vitro bacterial killing, not even in the absence of specific IgG.