Antibodies raised toward AmOmpA are specific. (A) Wells coated with GST alone, GST-AmOmpA, GST-ApOmpA, or AmOmpA50–67 were screened with antibodies targeting mature AmOmpA or AmOmpA50–67. Results shown are the means ± standard deviations (SD) from triplicate samples. OD450, optical density at 450 nm. ***, P < 0.001. (B) GST-tagged ApOmpA and AmOmpA were subjected to Western blot analyses with anti-GST, anti-ApOmpA59–74, or anti-HisAmOmpA. (C) Western blot analyses of His-ApOmpA, His-AmOmpA, and His-OtOmpA using antibodies specific for the His tag, ApOmpA59–74, and AmOmpA50–67. (D) Rat anti-HisAmOmpA was used to screen Western-blotted A. marginale (Am)-infected (I) and uninfected (U) RF/6A, ISE6 whole-cell lysates, and A. phagocytophilum (Ap)-infected and uninfected HL-60 cell lysates.