Antibodies to plant-produced plasmodium falciparum sexual stage protein PFS25 exhibit transmission blocking activity
Malaria is a serious and sometimes fatal mosquito-borne disease caused by a protozoan parasite. Each year, millions of new cases of malaria occur throughout the world, and it is estimated that over one million people are killed by Plasmodium falciparum each year. The disease burden is especially high in Africa with devastating impact on both human lives and the economy. Yet malaria is preventable and treatable. Developing vaccines against the parasite is a critical component of the fight against malaria and can target different stages of the pathogen's life cycle. We are targeting sexual stage proteins of P. falciparum which are found only on the surfaces of the parasite reproductive cells which imbed themselves in the mosquito gut. Antibodies against these proteins block the progression of the parasite's life cycle in the mosquito, and thus block transmission to the next human host. We have successfully produced multiple versions of the Pfs25 antigen in our plant-based launch-vector system and evaluated these vaccine candidates in animal models. All the proteins express in plants at a high level, are soluble and most importantly, generate strong transmission blocking activity as determined by a standard membrane feeding assay. These data demonstrate the feasibility of expressing Plasmodium antigens in a plant-based system for the economic production of a transmission blocking vaccine.