New Insights for Native Production of MSP1(19), the Disulfide-Rich C-Terminal Fragment from Plasmodium falciparum Merozoite Surface Protein 1

Malaria represents a major public health problem and an important cause of mortality and morbidity. The malaria parasites are becoming resistant to drugs used to treat the disease and still no efficient vaccine has been developed. One promising vaccine candidate is the merozoite surface protein 1 (MSP1), which has been extensively investigated as a vaccine target. The surface protein MSP1 plays an essential role in the erythrocyte invasion process and is an accessible target for the immune system. Antibodies to the carboxy-terminal region of the protein, named MSP1(19), can inhibit erythrocyte invasion and parasite growth. In order to develop an effective MSP1(19)- based vaccine against malaria, production of an antigen that is recognized by protective antibodies is mandatory. To this aim, we propose a method to produce the disulfide-rich MSP1(19) in its native conformation based on its in vitro oxidative refolding. The native conformation of the renatured MSP1(19) is carefully established by immunochemical reactivity experiments, circular dichroism and NMR. MSP1(19) can successfully be refolded in vitro as an isolated protein or as a fusion with the maltose binding protein. The possibility to properly fold MSP1(19) in vitro paves the way to new approaches for high titer production of native MSP1(19) using Escherichia coli as a host.