Author(s): Zhenhong Sun, Ping Fu, Kai Wei, Haiyan Zhang, Yuewei Zhang, Jian Xu, Fei Jiang, Xu Liu, Wei Xu, Wenxue Wu *
Mycoplasma bovis (M. bovis ) is a major but often overlooked pathogen. It mainly causes respiratory disease, mastitis, arthritis, keratoconjunctivitis, and otitis. M. bovis was first isolated from a case of severe mastitis in cattle in 1961 . It has since been reported to be connected with bovine respiratory disease . In China, it was first isolated in 2008, from the lungs of calves infected with pneumonia . This disease exists worldwide today. In Europe, about 25-33% of cases of calf pneumonia are caused by or associated with M. bovis . In the U.S., M. bovis is responsible for annual losses of USD 140 million resulting from bovine respiratory disease and breast disease, with a maximum infection rate of up to 70% per cattle feedlot -.
Under natural conditions, M. bovis infection is difficult to identify and easy to confuse with contagious pleuropneumonia because their clinical symptoms and pathologic changes are very similar. This leaves laboratory differential diagnosis as the best available way to identify M. bovis infection. Generally, serological diagnosis is more sensitive than M. bovis isolation, especially for the chronic cases or animals treated with antibiotics . Currently, a few commercial indirect ELISA kits have been used for this purpose. The commonly used are the Mycoplasma bovis Antibody Test Kit which is produced by Canada's Biovet Company and Bio-X Mycoplasma bovis ELISA Kit produced by Belgium's Bio-X Diagnostics Company. Most kits are based on whole-cell proteins, and the effects with respect to the detection of M. bovis infection in different geographic regions have yet to be verified. However, the use of specific, highly pure antigens with high affinity to antibodies as coating antigens may render the diagnosis more accurate.
Early reported M. bovis immunogenic proteins involved variable surface proteins (Vsps). These membrane-surface antigens can vary in phase and size. This involves high-frequency rearrangements of the DNA region encoding the Vsp genes. These rearrangements play a major role in evading the immune system of the host , . In recent years, several relatively conserved immunogenic proteins have been discovered. These include the conserved P26  and P48  lipoproteins, heat-shock proteins , and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) . These proteins may be suitable for use as candidate antigens for diagnosis and subunit vaccines against M. bovis . Currently, only a few of the immunogenic proteins of M. bovis are well understood. More immunogenic proteins must be identified to facilitate development of more effective approaches to both the diagnosis and prevention of M. bovis .
Proteome analysis is a useful complementary method of studying pathogens. It facilitates genome annotation and protein identification , . Immunoproteomics, which combines conventional proteomics with serology, is a powerful method of identifying immunodominant antigens that have diagnostic and protective value . In this study, 19 immunogenic proteins were identified in a strain of M. bovis that had been isolated in China. These proteins were identified using...