Table 1.

Asexual blood-stage antigens under development as vaccines

AntigenLocalization and processingFunctionEffect of gene disruption/deletion1Best evidence of protectionLevel of vaccine developmentConclusions from human trialsSelected references
MSP1Merozoite surface; cleaved into four fragments during schizogeny; final cleavage during invasionInvolved in inter-merozoite and merozoite-RBC interactionsLethal; cross-species complementation possible between P. falciparum and P. chabaudiProtection from challenge in NHPPhase I/II (MSP1190L)Reduction in parasite density; responsible component not identifiedGenton et al., 2002; Holder, 1996; Stowers and Carter, 2001
Phase I (MSP142)No data available
AMA1Micronemes; move to surface membrane of merozoiteUnknownLethalProtection from challenge in NHPPhase INo data availableDeans, 1984; Hodder et al., 2001; Stowers et al., 2002
SERAParasitophorous space; binds to merozoite and schizont surfacePapain-like enzyme with presumed protease activityLethalVaccine trials in rodents and AotusUnknownNot publishedAoki et al., 2002; Inselburg et al., 1993
MSP2Merozoite surfaceUnknownNot reportedProtection from challenge in NHPPhase IIReduction in parasite density; apparent selection pressure on MSP2 suggested a role in protectionGenton et al., 2002; Graves and Gelbrand, 2003
MSP3Merozoite surfaceUnknownDecreased invasion; decreased expression of ABRAProtection from challenge in rodents and NHPPhase INo data availableHisaeda et al., 2002; Oeuvray et al., 1994a
ADCI
MSP4/5Merozoite surfaceUnknownNot reportedProtection in rodentsUnknownNo data availableKedzierski et al., 2002
EBA-175MicronemeRBC binding via glycophorin AStable switching to alternative invasion pathwayProtection from challenge in NHPTrials anticipatedNot applicableJones et al., 2001; Sim et al., 1994
RESAMicronemeUnknownNot reportedProtection from challenge in NHPPhase I/IIReduction in parasite density; responsible component not identifiedBerzins et al., 1991; Collins et al., 1986; Genton et al., 2000
RAP1 and RAP2RhoptryUnknownKnockout of RAP1 survives; RAP2 knockout is lethalPartial protection from challenge in NHPUnknownNot applicableCollins et al., 2000; Ridley et al., 1990
GLURPParasitophorous vacuole; binds to merozoite surfaceUnknownNot reportedADCIUnknownNo data availableOeuvray et al., 2000; Theisen et al., 2001
pfEMP1Red cell surfaceBinding to RBC, endothelial cells and syncytio-trophoblastsViableVaccine trial in monkeys (using CIDR)Requires proof of principleNot applicableBaruch et al., 2002; Leech et al., 1984
  • NHP, non-human primates; ADCI, antibody-dependent cellular inhibition; RBC, red blood cells; ABRA, acidic-basic repeat antigen; CIDR, cysteine-rich interdomain region; HLA, human leucocyte antigen.

  • 1 Data from Cowman et al. (2002) and publications cited therein.