Neutralization epitopes on the antigenic domain II of the Orientia tsutsugamushi 56-kDa protein revealed by monoclonal antibodies

Monoclonal antibodies (MoAbs) reactive with the authentic Orientia tsutsuga mushi 56-kDa protein were generated. MoAb FS10 and FS15 showed in vitro, as well as, in vivo neutralizing activity upon O. tsutsugamushi infection. De letion mutants of the gene for 56-kDa protein of O. tsutsugamushi Boryong w ere expressed to map the binding region. FS10 and FS15 are bound to amino a cids (aa) located in an antigenic domain II, at residues 140-160 and 187-21 4, respectively. Computer modeling indicated that aa 146-153 were important for antigenicity against FS10. A sequence for aa 142-150 was highly homolo gous between oriential strains. These results suggest that the antigenic de terminant for neutralizing MoAbs is an epitope within aa 140-160. Furthermo re, this region may be important for the adhesion/invasion or intracellular survival of O. tsutsugamushi within host cells. (C) 2000 Elsevier Science Ltd. All rights reserved.