A 64 kilodalton (KD) lipoprotein was isolated from Mycoplasma gallisepticum membrane and used for preparation of subunit vaccine. Evalua- tion of the prepared vaccine against colonization of M. gallisepticum (MG) in chicken trachea was studied. Immunoblot of 64 KD protein of M. gullisepticum separated by high performance liquid chromatography (HPLC) and Triton X-114 extraction, against anti- MG chicken serum proved that it is highly immunogenic protein. Sixty one- day old mycoplasma free Hubbard chicks were used. The chicks were divided into 5 groups each of tweleve chicks. Three groups were given 0.25, 0.5 and 0.75 mg of MG vaccine then challenged one month later with 15000 CFU/ 0.1ml /bird/ intratracheally. The remaining two groups were kept as negative and positive controls. Chickens.
Vaccinated with subunit vaccine (0.5 and 0.75 mg/ bird) resulted in 100% protection against tracheal M. gallisepticum colonization. Birds of the group vaccinated with 0.25 mg / bird (group No.1)were positive for mycoplasma isolation up to 4 weeks post-challenge. Vaccinated groups No (2 and 3) were positive by serum plate agglutination test and ELISA along the duration of experiment. While chickens of group No (1) that vaccinated with 0.25 mg / bird gave suspected results by SPA and ELISA in the first week post- challenge, then gave positive results. Vaccination of the chickens with M. gallisepticum subunit vaccine resulted in high antibody response to 64 KD protein at 2 weeks after the booster dose.