Contribution of toxic shock syndrome toxin-1 to systemic inflammation investigated by a mouse model of cervicovaginal infection with Staphylococcus aureus

Toxic shock syndrome toxin-1 (TSST-1), a superantigen produced by Staphylococcus aureus is a causative agent of toxic shock syndrome (TSS) that is frequently associated with tampon use. It has long been suggested that TSS is induced when TSST-1 circulates through the body. However, the systemic distribution of TSST-1 from vagina or uterus has never been demonstrated. In this study, a mouse cervicovaginal infection model was established. Transcervical inoculation with a virulence strain of S. aureus and its derivative TSST-1-deficient mutant demonstrated that TSST-1 distributed to the bloodstream and spleen, and promoted systemic inflammation without bacteremia. Transcervical administration with the wild-type toxin and a superantigen-deficient mutant of TSST-1 (mTSST-1) demonstrated that the superantigenic activity of TSST-1 was essential to stimulate the systemic inflammation. Furthermore, this activity was not promoted by co-transcervical inoculation with lipopolysaccharides. The circulating TSST-1 and systemic inflammation rapidly reduced at 48 h after administration, suggesting that persistence of S. aureus in the uterus may be involved in long-term complications of TSS. Transcervical inoculation with mTSST-1-producing S. aureus showed that this toxin promoted bacterial number, uterine tissue damage, and localization of bacterial cells around uterine cavity. The results suggest that TSST-1 enhances S. aureus burden in uterine cavity, the secreted TSST-1 distributes into circulation system, and then systemic inflammation is induced.