Fibronectin facilitates the invasion of Orientia tsutsugamushi into host cells through interaction with a 56-kDa type-specific antigen.
BACKGROUND
Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium. The pathogen's mechanism of cellular invasion is poorly characterized.


METHODS
Through ligand immunoblots, glutathione S-transferase (GST) pull-down assays, and in vitro inhibition assays of intracellular invasion, a bacterial ligand was identified and was shown to interact with fibronectin (Fn) to enhance the intracellular invasion of O. tsutsugamushi.


RESULTS
O. tsutsugamushi can bind to immobilized Fn in vitro, and exogenous Fn stimulates bacterial invasion of mammalian host cells. Bacterial invasion in the presence of Fn was abrogated by the addition of Arg-Gly-Asp peptides or by an anti-alpha5beta1 integrin antibody. Through a ligand immunoblot and GST pull-down assay, a 56-kDa type-specific antigen (TSA56) was identified as the bacterial ligand responsible for the interaction with Fn. Antigenic domain III and the adjacent C-terminal region (aa 243-349) of TSA56 interacted with Fn. Furthermore, we found that the enhanced invasion of the pathogen was abrogated by the addition of purified recombinant peptides derived from TSA56.


CONCLUSIONS
Fn facilitates the invasion of O. tsutsugamushi through its interaction with TSA56.
Lee
Jung-Hee
JH
Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Republic of Korea.
Cho
Nam-Hyuk
NH
Kim
Se-Yoon
SY
Bang
Sun-Young
SY
Chu
Hyuk
H
Choi
Myung-Sik
MS
Kim
Ik-Sang
IS
D000818:Animals; D000942:Antigens, Bacterial / Q000502:physiology*; D001422:Bacterial Adhesion / Q000502:physiology*; D001665:Binding Sites; D002455:Cell Division; D005353:Fibronectins / Q000502:physiology*; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007739:L Cells; D051379:Mice; D012285:Orientia tsutsugamushi / Q000472:pathogenicity*; D011994:Recombinant Proteins / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000502:physiology
D000942:Antigens, Bacterial; D005353:Fibronectins; D011994:Recombinant Proteins; D012710:Serum Albumin, Bovine; D005982:Glutathione Transferase