Biochemical and Immunological Characterization of Bacterially Expressed and Refolded Plasmodium falciparum 42-Kilodalton C-Terminal Merozoite Surface Protein 1

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American Society for Microbiology

RESUMO

Protection against Plasmodium falciparum can be induced by vaccination in animal models with merozoite surface protein 1 (MSP1), which makes this protein an attractive vaccine candidate for malaria. In an attempt to produce a product that is easily scaleable and inexpensive, we expressed the C-terminal 42 kDa of MSP1 (MSP142) in Escherichia coli, refolded the protein to its native form from insoluble inclusion bodies, and tested its ability to elicit antibodies with in vitro and in vivo activities. Biochemical, biophysical, and immunological characterization confirmed that refolded E. coli MSP142 was homogeneous and highly immunogenic. In a formulation suitable for human use, rabbit antibodies were raised against refolded E. coli MSP142 and tested in vitro in a P. falciparum growth invasion assay. The antibodies inhibited the growth of parasites expressing either homologous or heterologous forms of P. falciparum MSP142. However, the inhibitory activity was primarily a consequence of antibodies directed against the C- terminal 19 kDa of MSP1 (MSP119). Vaccination of nonhuman primates with E. coli MSP142 in Freund's adjuvant protected six of seven Aotus monkeys from virulent infection with P. falciparum. The protection correlated with antibody-dependent mechanisms. Thus, this new construct, E. coli MSP142, is a viable candidate for human vaccine trials.

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