BackgroundRodent malaria parasites (RMP) are used extensively as models of human malaria. Draft RMP genomes have been published for Plasmodium yoelii, P. berghei ANKA (PbA) and P. chabaudi AS (PcAS). Although availability of these genomes made a significant impact on recent malaria research, these genomes were highly fragmented and were annotated with little manual curation. The fragmented nature of the genomes has hampered genome wide analysis of Plasmodium gene regulation and function.ResultsWe have greatly improved the genome assemblies of PbA and PcAS, newly sequenced the virulent parasite P. yoelii YM genome, sequenced additional RMP isolates/lines and have characterized genotypic diversity within RMP species. We have produced RNA-seq data and utilised it to improve gene-model prediction and to provide quantitative, genome-wide, data on gene expression. Comparison of the RMP genomes with the genome of the human malaria parasite P. falciparum and RNA-seq mapping permitted gene annotation at base-pair resolution. Full-length chromosomal annotation permitted a comprehensive classification of all subtelomeric multigene families including the ‘Plasmodium interspersed repeat genes’ (pir). Phylogenetic classification of the pir family, combined with pir expression patterns, indicates functional diversification within this family.ConclusionsComplete RMP genomes, RNA-seq and genotypic diversity data are excellent and important resources for gene-function and post-genomic analyses and to better interrogate Plasmodium biology. Genotypic diversity between P. chabaudi isolates makes this species an excellent parasite to study genotype-phenotype relationships. The improved classification of multigene families will enhance studies on the role of (variant) exported proteins in virulence and immune evasion/modulation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-014-0086-0) contains supplementary material, which is available to authorized users.

BackgroundRodent malaria parasites (RMP) are used extensively as models of human malaria. Draft RMP genomes have been published for Plasmodium yoelii, P. berghei ANKA (PbA) and P. chabaudi AS (PcAS). Although availability of these genomes made a significant impact on recent malaria research, these genomes were highly fragmented and were annotated with little manual curation. The fragmented nature of the genomes has hampered genome wide analysis of Plasmodium gene regulation and function.ResultsWe have greatly improved the genome assemblies of PbA and PcAS, newly sequenced the virulent parasite P. yoelii YM genome, sequenced additional RMP isolates/lines and have characterized genotypic diversity within RMP species. We have produced RNA-seq data and utilised it to improve gene-model prediction and to provide quantitative, genome-wide, data on gene expression. Comparison of the RMP genomes with the genome of the human malaria parasite P. falciparum and RNA-seq mapping permitted gene annotation at base-pair resolution. Full-length chromosomal annotation permitted a comprehensive classification of all subtelomeric multigene families including the ‘Plasmodium interspersed repeat genes’ (pir). Phylogenetic classification of the pir family, combined with pir expression patterns, indicates functional diversification within this family.ConclusionsComplete RMP genomes, RNA-seq and genotypic diversity data are excellent and important resources for gene-function and post-genomic analyses and to better interrogate Plasmodium biology. Genotypic diversity between P. chabaudi isolates makes this species an excellent parasite to study genotype-phenotype relationships. The improved classification of multigene families will enhance studies on the role of (variant) exported proteins in virulence and immune evasion/modulation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-014-0086-0) contains supplementary material, which is available to authorized users.

Highly purified protein antigens are usually poor immunogens; in practice, adjuvants are needed to obtain satisfactory immune responses. Plasmodium yoelii 19-kDa merozoite surface protein 1 (MSP1 19 ) is a weak antigen, but mice vaccinated with this antigen in strong adjuvants can survive an otherwise lethal parasite challenge. Fusion proteins comprising this antigen fused to the oligomerization domain of the murine complement inhibitor C4-binding protein (C4bp) and a series of homologues have been produced. These C4bp domains acted as adjuvants for the fused antigen; the MSP1 19 -murine C4bp fusion protein induced protective immunity in BALB/c mice. Because this fusion protein also induced antibodies against circulating murine C4bp, distantly related C4bp oligomerization domains fused to the same antigen were tested. These homologous domains did not induce antibodies against murine C4bp and, surprisingly, induced higher antibody titers against the antigen than the murine C4bp domain induced. These results demonstrate a new adjuvantlike effect of C4bp oligomerization domains.

No abstract

We have purified apical merozoite antigen 1 (AMA-1) from extracts of red blood cells infected with the rodent malaria parasite Plasmodium yoelii yoelii YM. When used to immunize mice, the protein induced a strong protective response against a challenge with the parasite. Monoclonal antibodies specific for P. yoelii yoelii AMA-1 were prepared, and one was very effective against the parasite on passive immunization. A second protein that appears to be located in the apical rhoptry organelles and associated with AMA-1 was identified.Early studies by Cohen et al. (6) and more recently by Sabchareon et al. (39) demonstrated that passive immunization with purified immunoglobulin obtained from adults living in areas holoendemic for malaria transferred clinical protection against Plasmodium falciparum, the causative agent of the most severe form of malaria. The mechanisms involved in this protective effect of antibody have been analyzed in in vivo and in vitro studies using humans and animal models. With respect to merozoites and erythrocyte (red blood cell [RBC]) invasion, it has been proposed that the protective mechanisms include merozoite neutralization by blocking ligand-receptor interactions or agglutination, the targeting of monocytes to secrete cytotoxic factors in an antibody dependent cell-mediated inhibition (4), and the specific inhibition of essential biochemical events such as the processing of merozoite surface protein 1 (MSP-1) (3).Apical membrane antigen 1 (AMA-1) is a merozoite protein that is a target of immune effector mechanisms that most likely neutralize merozoite invasion. The protein is located in the apical rhoptry organelles of the developing and free merozoite (8) and can be relocated from here to the surface of the parasite. In immunofluorescence studies with specific antibodies, a characteristic punctate pattern is observed, together with a circumferential (merozoite surface) staining pattern (32). This protein was initially identified in the simian malaria parasite P. knowlesi and named PK66 (here called PkAMA-1) (12). Monoclonal antibodies (MAbs) and their Fab fragments specific for PkAMA-1 were inhibitory in in vitro cultures, acting at a point in the parasite's asexual blood-stage development beyond schizont maturation (9, 42). Further evidence that AMA-1 can induce a strong protective immune response has been provided by immunization of nonhuman primates against simian malaria parasites (7, 11) and of mice against P. chabaudi (1). The 83-kDa P. falciparum AMA-1 (PfAMA-1; also named PF83 [35,44]) is well conserved at the primary sequence level compared to the simian and rodent malaria proteins, except for an N-terminal extension in PfAMA-1. The sequence conservation within the AMA-1 family, including the protein in other human (5), nonhuman primate (15, 36, 45), and rodent (25) malaria parasites, suggests that there are strong functional constraints on the structure of this protein.The protein contains a large external ectodomain followed by a transmembrane region and a short cytoplas...