the present invention provides nucleic acid and amino acid sequences useful as the immunogenic portion of vaccines or immunogenic compositions effective for lessening the severity of the clinical symptoms associated with lawsonia intracellularis infection or conferring protective immunity to an animal susceptible to such infection . preferred amino acid sequences include at least 9 contiguous amino acids from seq id nos 1 , 3 , or 7 . thus , the nucleic acid sequences encoding such proteins , or the proteins themselves are included in vaccine compositions , together with veterinary - acceptable carrier and administered to an animal in need thereof .