FIG 7.

Defect of processing of rOmpA in the R. rickettsii low-egg-passage Iowa small-plaque variant. (A) Immunoblot of the low-egg-passage Iowa small (S)- and large (L)-plaque variants, high-egg-passage Iowa, and virulent R. rickettsii Sheila Smith (SS) or Hino strains with a monoclonal antibody (13-3) against the rOmpA passenger domain (α, anti). The unprocessed precursor forms are indicated by white arrowheads, and the proteolytically processed passenger domains are indicated by black arrowheads. (B) Immunoblot of strains described for panel A using the rabbit polyclonal antibody against the rOmpA β fragment. The unprocessed precursor forms are indicated by white arrowheads, and the proteolytically processed autotransporter domains are indicated by black arrowheads. (C) Immunoblot against rOmpB using a polyclonal rabbit antibody against the passenger domain of rOmpB demonstrating the deficiency in rOmpB cleavage by all of the Iowa variants. It is important to note that this particular antibody preferentially recognizes the processed, passenger domain of rOmpB despite its being a relatively minor species in the Iowa strain.