Quantification of MDP1 by ELISA. Proteins were extracted from broth cultures of the strains M. bovis BCG(pAS-MDP1) and M. bovis BCG(pMV261) grown until OD (600 nm) of 2.0. (A) 5, 1 and 0.2 μg of total protein were loaded into Microwell plates and incubated with either a MDP1-specific antiserum or with pre-immune serum. The OD at 450 nm reflects the amount of MDP1 antibody bound by the MDP1 protein. The diagram shows the values obtained after subtraction of the ODs measured with the pre-immune serum from the ODs measured with the MDP1 antiserum. (B) 30 μg of total protein from BCG(pMV261) were separated in a 10% SDS-PAGE, transferred onto a PVDV membrane and incubated either with MDP1 antiserum (1) or with the corresponding pre-immune serum (2). M: protein marker.