**3. Subunit vaccine candidate antigens**

The advent of recombinant DNA technology has greatly facilitated the development of subunit malaria vaccines by providing the tools with which to synthesise large amounts of parasite protein, and to disrupt gene expression for detailed functional characterisation [40- 42]. Preclinical development for many candidate antigens has been successful and Phase II clinical trials have proceeded for at least eight candidate antigens, with evidence of antimalarial efficacy for MSP2 [6], CSP [43, 44], MSP3 [45] and AMA1 [46].

The release of the first full malaria genome sequence in 2002 allowed the systematic identification of novel malaria vaccine candidates amongst approximately 5300 genes. Genome wide screening for single nucleotide polymorphisms (SNPs) has been used to reveal loci under positive selection and therefore encoding proteins that may be targeted by the immune response [4, 47]. Proteomics approaches have characterised the "immunome" [48], and measured the abundance of parasite proteins on the parasite surface [49]. A pipeline of bioinformatic screens has also been used to identify surface proteins, gene knockouts and high-throughput immunological assays to identify novel surface antigens (e.g. [50]). In the last 10 years, the list of potential malaria vaccine candidates has rapidly expanded to encompass many antigens about which there is still much to be learnt. Targets that were discovered first are therefore further down the development pipeline rather than novel proteins that may ultimately be more successful.

Below, we describe the most developed malaria vaccine candidates for the two major malaria parasites, *P. falciparum* and *P. vivax* as well as some novel vaccine candidates that have recently been identified for *P. falciparum*. This is not a comprehensive listing, a complete list of preclinical, clinical and inactive or discontinued malaria vaccine projects can be found in the World Health Organisation's Malaria Vaccine Rainbow Tables [51].
