Molecular characterization of three major outer membrane proteins, TSA56, TSA47 and TSA22, in Orientia tsutsugamushi

Abstract

Abstract. Orientia tsutsugamushi (O. tsutsugamushi), the causative agent of scrub typhus, is an obligate intracellular pathogen. Recent studies have demonstrated the complete genome of O. tsutsugamushi. However, the route and detailed molecular mechanism for O. tsutsugamushi to get accessed into mammalian cells remains unclear. In this study, we demonstrated different adhesive properties of three major outer membrane proteins of O. tsutsugamushi, TSA56, TSA47 and TSA22. TSA56 showed higher antibody responses against patient serum samples compared with those of TSA47 and TSA22. In the adhesion assay, TSA56 exhibited a relative higher adhesion to host cells than TSA47 and TSA22, suggesting that TSA56 is the major outer membrane protein required for O. tsutsugamushi adhesion. Furthermore, the antigen domain (AD) I (residues 19-114) corresponding to the extracellular domain of TSA56 demonstrated a relative high antibody response against the patients' sera than the previously reported ADIII (residues 237-366), which has been suggested to facilitate the invasion of O. tsutsugamushi through interaction with fibronectin. Taken together, our results consistently showed that TSA56 of O. tsutsugamushi is important in the adhesion of Escherichia coli (E. coli) transformants to Vero cells. Moreover, in contrast to known ADIII-fibronectin interactions, TSA56-ADI may also play a role in the adhesion and/or invasion of O. tsutsugamushi to its host cells through unidentified receptors. A further study aimed at delineating the receptor of TSA56-ADI during O. tsutsugamushi infection is warranted.

Representative Genotyping, Recombination and Evolutionary Dynamics Analysis of TSA56 Gene Segment of Orientia tsutsugamushi

“…Although the virulence truth still needs the further analysis, the TSA56 is a useful target to inhibit bacterial virulence. As for the biological function of TSA56 protein, it is required for O. tsutsugamushi adhesion by binding to fibronectin and facilitating bacterial invasion of mammalian host cells (Lin et al, 2012 ). So successful invasion gives bacteria chances to exert virulence, while inhibiting this protein can prevent O. tsutsugamushi from invading cells, no matter what virulence it is.…”

A surface antigen of Orientia tsutsugamushi activates human monocyte-derived dendritic cells via nuclear factor-kB & p38 mitogen-activated protein kinase pathways

“…Expression of recombinant Sta56 : Escherichia coli M15 was used as the host strain for the pET-32a expression vector (Qiagen GmbH, Hilden, Germany) carrying the Sta56-encoding gene 16 . Recombinant bacteria were grown in Luria-Bertani (LB) medium supplemented with ampicillin (50 μg/ml) and kanamycin (50 μg/ml) at 37°C with vigorous shaking overnight, and 1 ml of culture was used to inoculate 100 ml of fresh antibiotic-containing LB.…”

OMPdb: A Global Hub of Beta-Barrel Outer Membrane Proteins

“…In O. tsutsugamushi, there are three major outer membrane proteins: TSA56, TSA47, and TSA22. The TSA56 is the major outer membrane protein responsible for O. tsutsugamushi adhesion (Lin et al, 2012;Trung et al, 2019). (vii) Relapsing fever is a worldwide, endemic disease caused by several spirochetal species belonging to the genus Borrelia.…”