Influence of staphylococcal enterotoxin B (SEB) on the course of murine listeriosis.

Confrontation of the immune system with bacterial superantigens leads to an initial activation of the immune system followed by a state of profound immunosuppression. To investigate the role of a superantigen in an acute infection with a facultatively intracellular bacterium, we have studied the effect of staphylococcal enterotoxin B on the course of murine listeriosis. Intraperitoneal injection of SEB led to a statistically significant growth restriction of Listeria monocytogenes in the organs of mice infected intravenously or intraperitoneally when treatment with SEB and infection with L. monocytogenes were given simultaneously or when the mice were treated two days before infection. No effect of SEB on murine listeriosis was found when SEB was given more than two days before infection or one or more days after infection. We conclude that initial immunostimulation by SEB which is indicated by a massive liberation of all interleukins measured (IL1 alpha, IL6, TNF alpha, IL2, IFN gamma, IL4) is responsible for the growth restriction of L. monocytogenes in the organs of treated mice. Apoptosis of V beta 8 positive T cells which was accompanied by a 30% reduction of these cells at day 7 after treatment seems to be totally compensated.