A domino-like chlamydial attachment process: Parachlamydia acanthamoebae attachment to amoebae is concurrently required for several amoebal released molecules and serine-protease activity

摘要

Parachlamydia acanthamoebae is an obligate intracellular bacterium that infects free-living amoebae (Acanthamoeba), and is a potential human pathogen associated with hospital-acquired pneumonia. The attachment mechanism of this bacteria to host cells is a crucial step in bacterial pathogenesis, yet remains undetermined. Hence, we established monoclonal antibodies (mAbs) specific to either P. acanthamoebae or amoebae in an attempt to elucidate the involved attachment mechanism. Hybridomas of 954 clones were assessed, and we found four mAbs (mAb38, mAb300, mAb311, mAb562) that were reactive to the amoebae significantly inhibited bacterial attachment. All mAbs recognized amoebal released molecules, and mAb311 also recognized the amoebal surface. MAbs reacted with the bacteria not only in amoebae, but also those released from amoebae (except mAb311). Furthermore, serine-protease inhibitor had an inhibitory effect on the bacterial attachment to amoebae, although none of the mAbs had any synergetic effect on the attachment inhibition by the protease inhibitor. Taken together, we concluded that P. acanthoamebae attachment to amoebae is concurrently required for several amoebal released molecules and serine-protease activity, implying the existence of a complicated host-parasite relationship.