Expression of the Mycobacterium bovis P36 gene in Mycobacterium smegmatis and the baculovirus/insect cell system

In the present study we evaluated different systems for the expression of m ycobacterial antigen P36 secreted by Mycobacterium bovis. P36 was detected by Western blot using a specific antiserum. The P36 gene was initially expr essed in E. coli, under the control of the T7 promoter, but severe proteoly sis prevented its purification. We then tried to express P36 in M. smegmati s and insect cells. For M. smegmatis, we used three different plasmid vecto rs differing in copy number and in the presence of a promoter for expressio n of heterologous proteins. P36 was detected in the cell extract and cultur e supernatant in both expression systems and was recognized by sera from M bovis-infected cattle. To compare the expression level and compartmentaliza tion, the MPB70 antigen was also expressed. The highest production was reac hed in insect cell supernatants. In conclusion, M smegmatis and especially the baculovirus expression system are good choices for the production of pr oteins from pathogenic mycobacteria for the development of mycobacterial va ccines and diagnostic reagents.