Malaria vaccines: Focus on adenovirus based vectors

Protection against malaria through vaccination is known to be achievable, as first demonstrated over 30 years ago. Vaccination via repeated bites with Plasmodium falciparum infected and irradiated mosquitoes provided short lived protection from malaria infection to these vaccinees. Though this method still remains the most protective malaria vaccine to date, it is likely impractical for widespread use. However, recent developments in sub-unit malaria vaccine platforms are bridging the gap between high levels of protection and feasibility. The current leading sub-unit vaccine, RTS,S (which consists of a fusion of a portion of the P. falciparum derived circumsporozoite protein to the Hepatitis B surface antigen), has demonstrated the ability to induce protection from malaria infection in up 56% of RTS,S vaccinees. Though encouraging, these results may fall short of protection levels generally considered to be required to achieve eradication of malaria. Therefore, the use of viral vectored vaccine platforms has recently been pursued to further improve the efficacy of malaria targeted vaccines. Adenovirus based vaccine platforms have demonstrated potent anti-malaria immune responses when used alone, as well when utilized in heterologous prime boost regimens. This review will provide an update as to the current advancements in malaria vaccine development, with a focus on the use of adenovirus vectored malaria vaccines.