Molecular cloning and sequencing of the circumsporozoite protein gene from Plasmodium falciparum strain FCC-1/HN and expression of the gene in Mycobacteria.

Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been used as a live bacterial vaccine to immunize more than 2 billion people against tuberculosis. In an attempt to use this vaccine strain as a vehicle for protective antigens, the Plasmodium falciparum gene from strain FCC-1/HN encoding circumsporozoite protein (CSP) was amplified from the P. falciparum genome, sequenced, and expressed in M. bovis BCG under the control of an expression cassette carrying the promoter of heat shock protein 70 (HSP70) from Mycobacterium tuberculosis. The recombinant shuttle plasmid pBCG/CSP was introduced into mycobacteria by electroporation, and the recombinant mycobacteria harboring pBCG/CSP could be induced by heating to express CSP; the molecular mass of recombinant CSP was about 42 kDa. This report of expression of the almost-full-length P. falciparum CSP gene in BCG provides scientific evidence for the application of the HSP70 promoter in expressing a foreign gene in BCG and in development of BCG as a multivalent vectoral vaccine for malaria.