The RTS,S vaccine was engineered using a fusion hepatitis B surface protein containing epitopes of the outer protein of Plasmodium falciparum malaria sporozite, which is produced in yeast cells. It also contains a chemical adjuvant to boost the immune system response.[12] The vaccine is being developed by PATH and GlaxoSmithKline (GSK), which has spent about $300 million on the project, plus about $200 million more from the Bill and Melinda Gates Foundation.[13]