Fig. 2

Purification of target recombinant protein by heat-treatment. a Heat treatment of L. lactis raw culture supernatant expressing recombinant MSPDBL2; Left panel: Coomassie blue stained SDS-PAGE analysis of MSPDBL2 containing supernatant before (lane 1) and after (lane 2) heat treatment; Right panel: Corresponding Western blot probed with anti-His antibodies. b Heat treatment of L. lactis raw culture supernatant expressing R0-MSPDBL2 fusion protein; Left panel: Coomassie blue stained SDS-PAGE analysis of R0-MSPDBL2 containing culture supernatant before (lane 1) and after (lane 2) heat treatment; lane 3: TEV protease treatment of recombinant R0-MSPDBL2 and ion-exchange chromatography based separation of R0 fusion partner (lane 4) and MSPDBL2 (lane 5) fragments after TEV protease cleavage of R0-MSPDBL2 derived from heat treated culture supernatant; Right panel: Corresponding Western blot probed with anti-His antibodies. The arrow-heads indicate the position of MSPDBL2 fragment. c Size exclusion chromatography analysis of purified recombinant MSPDBL2 as obtained from L. lactis culture supernatants expressing R0-MSPDBL2 (left panel) and MSPDBL2 expressed without carrier fusion partner (right panel). SE-HPLC was performed under native conditions in a phosphate buffer pH 7.2 to determine the amount of monomer in the sample. d Comparative antigenicity assessment of purified recombinant MSPDBL2 protein. The scatter-plot shows Pearson’s co-relation coefficient between the ELISA values observed for reactivity of a panel of 54 malaria hyperimmune Liberian sera samples against the recombinant MSPDBL2 protein preparations purified by heat treatment (y-axis) or without heat (x-axis)