Cellular invasion of Orientia tsutsugamushi requires initial interaction with cell surface heparan sulfate

Role of transmembrane heparan sulfate proteoglycans on invasion of Orientia tsutsugamushi into host cells was investigated. Pretreatment with heparan sulfate and heparin inhibited the infection of O. tsutsugamushi for L cell, mouse fibroblast, whereas other glycosaminoglycans had little effect. Thes e same treatments were also shown to reduce the infection in a dose-depende nt manner, and enzymatic treatment of cells with heparitinase, but not chon droitinase ABC, inhibited the infection. In addition, mutant cell lines of Chinese hamster ovarian cell defective in heparan sulfate synthesis but not chondrotin sulfate synthesis and defective in all glycosaminoglycan synthe sis showed marked reduction in susceptibility to infection by O. tsutsugamu shi. Also mutant cell lines, which express heparan sulfate proteoglycans at low level, showed intermediate level of infectivity. Finally O. tsutsugamu shi bind to S-35-labelled heparin. Collectively, these findings provide str ong evidence that heparan sulfate proteoglycans contribute to the attachmen t of O. tsutsugamushi to the cells. (C) 2000 Academic Press.