B. fragilis- and b. thetaiotaomicron-derived outer membrane vesicles control toll-like receptors expressions in opposite directions as new immune response mediators

Sara Ahmadi badi,1 Seyed davar siadat,2,* Arfa moshiri,3 Fateme ettehad marvastti,4 Shohre khatami ,5 Shiva irani,6

1. Microbiology Research Center (MRC), Pasteur Institute of Iran, Tehran, Iran
2. Microbiology Research Center (MRC), Pasteur Institute of Iran, Tehran, Iran
3. Microbiology Research Center (MRC), Pasteur Institute of Iran, Tehran, Iran
5. Biochemistry Department, Pasteur Institute of Iran, Tehran, Iran
6. 1Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran

Abstract

Introduction

The gastrointestinal tract is colonized by a microbial community which referred as gut microbiota. it produces microbial immunogenic compounds and products including outer membrane vesicles (omvs) that are sensed by toll like receptors (tlrs). bacteroides spp. and their omvs have significant roles in host immune response. in this regard, we evaluated tlrs mrna levels and cytokines concentration of caco-2 cell line treated with bacteroides fragilis, b. thetaiotaomicron, and their omvs.

Methods

Omvs extracted using tris-edta -sodium deoxycholate buffers and sequential centrifugation. omvs physicochemical properties were assayed using electron microscopy and sds-page. qpcr was performed to quantify tlrs mrna relative expression. ifn-ᵧ, il-17, il-10 and il-4 concentrations were assayed using elisa. our data were analyzed with statistical tests.

Results

The level of tlrs transcripts in caco-2 cells treated with b. fragilis compared to control had limited increase. while, b. thetaiotaomicron prevents expression of tlrs, administration of b. thetaiotaomicron derived omvs seems to have the same inhibitory effect on tlrs in caco-2 cells. also ifn-ᵧ, il-17 and il-4 concentrations were increased in all of treatments. b. fragilis elevated il-10 but its omvs decreased il-10 concentration. interestingly, although b. thetaiotaomicron did not have effect on il-10, but its omvs increased il-10 concentration.

Conclusion

According to our data, we propose the use of b. thetaiotaomicron derived omvs as possible immune response mediators.

Keywords

B. fragilis, b. thetaiotaomicron, gut microbiota, omvs, tlr and cytokines concentration