Lactobacillus crispatus mediates anti-inflammatory cytokine interleukin-10 induction in response to Chlamydia trachomatis infection in vitro

Chlamydia trachomatis, a human pathogen, is a Gram-negative bacillus and a compulsory intracellularparasite. It is the most common cause of bacterial sexually transmitted infections in both industrializedand developing countries. In women, untreated genital infections can result in devastating consequencessuch as pelvic inflammatory disease, ectopic pregnancy, and even infertility. Lactobacillus crispatus isan important urogenital species that is routinely found in the vagina of healthy women. Lactobacilliare involved in the maintenance of the normal vaginal microbiota and their dominance in the vaginasuggests that they play a crucial role in protecting the genitourinary tract against pathological condi-tions. Lactobacilli can act through the activation of the immune system, but C. trachomatis is able toeffectively evade immune surveillance in some individuals. The aim of our study was to investigate theimmunomodulatory efficacy of the potential probiotic strain L. crispatus in HeLa and J774 cells subjectedto C. trachomatis infection by studying the expression of the inflammatory cytokines IL-6, IL-8, TNF-and IL-10. Our results demonstrated, firstly, the lack of any cytotoxic effect on the epithelial cells andmacrophages when treated with L. crispatus and its supernatant; in addition, L. crispatus and its super-natant inhibited C. trachomatis adhesion and infectivity in human epithelial cells and macrophages. Ourstudy then showed that L. crispatus and its supernatant reduced IL-6, IL-8 and TNF- production in C.trachomatis-infected HeLa and J774 cells. In contrast, a significant upregulation of the IL-10 expressionin HeLa and J774 cells by L. crispatus and supernatant was also demonstrated. Our data indicate that L.crispatus specifically enhances the production of the IL-10 anti-inflammatory cytokine in contrast to theinhibitory effect of L. crispatus on the pro-inflammatory cytokines.