Reverse genetics screen identifies six proteins important for malaria development in the mosquito

Ecker, Andrea; Bushell, Ellen; Tewari, Rita; Sinden, Robert E.

doi:10.1111/j.1365-2958.2008.06407.x

Cited by 132 publications

(168 citation statements)

References 54 publications

(96 reference statements)

Supporting

Mentioning

160

Contrasting

Unclassified

Order By: Relevance

“…S1 in the supplemental material), and thus we believe that GAMA is essential to P. falciparum parasite invasion. However, it can be seen that the genetic disruption of the GAMA ortholog was successful in P. berghei (12). This discrepancy may be due to the differences in host erythrocyte receptors.…”

Section: Discussionmentioning

confidence: 86%

Discovery of GAMA, a Plasmodium falciparum Merozoite Micronemal Protein, as a Novel Blood-Stage Vaccine Candidate Antigen

et al. 2011

View full text Add to dashboard Cite

One of the solutions for reducing the global mortality and morbidity due to malaria is multivalent vaccines comprising antigens of several life cycle stages of the malarial parasite. Hence, there is a need for supplementing the current set of malaria vaccine candidate antigens. Here, we aimed to characterize glycosylphosphatidylinositol (GPI)-anchored micronemal antigen (GAMA) encoded by the PF08_0008 gene in Plasmodium falciparum. Antibodies were raised against recombinant GAMA synthesized by using a wheat germ cell-free system. Immunoelectron microscopy demonstrated for the first time that GAMA is a microneme protein of the merozoite. Erythrocyte binding assays revealed that GAMA possesses an erythrocyte binding epitope in the C-terminal region and it binds a nonsialylated protein receptor on human erythrocytes. Growth inhibition assays revealed that anti-GAMA antibodies can inhibit P. falciparum invasion in a dose-dependent manner and GAMA plays a role in the sialic acid (SA)-independent invasion pathway. Anti-GAMA antibodies in combination with anti-erythrocyte binding antigen 175 exhibited a significantly higher level of invasion inhibition, supporting the rationale that targeting of both SA-dependent and SA-independent ligands/pathways is better than targeting either of them alone. Human sera collected from areas of malaria endemicity in Mali and Thailand recognized GAMA. Since GAMA in P. falciparum is refractory to gene knockout attempts, it is essential to parasite invasion. Overall, our study indicates that GAMA is a novel blood-stage vaccine candidate antigen.

show abstract

Section: Discussionmentioning

confidence: 86%

Discovery of GAMA, a Plasmodium falciparum Merozoite Micronemal Protein, as a Novel Blood-Stage Vaccine Candidate Antigen

et al. 2011

View full text Add to dashboard Cite

show abstract

“…2). BLAST search identified the mosquito-stage protein PSOP12 (PFE0680) as paralog of CyRPA (69). This protein shares nine positionally conserved cysteine residues in the homologous N-terminal part, but additionally has a 6-cysteine-protein domain at the C terminus (70).…”

Section: Resultsmentioning

confidence: 99%

Passive Immunoprotection of Plasmodium falciparum-Infected Mice Designates the CyRPA as Candidate Malaria Vaccine Antigen

Dreyer

Matile

Papastogiannidis

et al. 2012

The Journal of Immunology

114

View full text Add to dashboard Cite

An effective malaria vaccine could prove to be the most cost-effective and efficacious means of preventing severe disease and death from malaria. In an endeavor to identify novel vaccine targets, we tested predicted Plasmodium falciparum open reading frames for proteins that elicit parasite-inhibitory Abs. This has led to the identification of the cysteine-rich protective Ag (CyRPA). CyRPA is a cysteine-rich protein harboring a predicted signal sequence. The stage-specific expression of CyRPA in late schizonts resembles that of proteins known to be involved in merozoite invasion. Immunofluorescence staining localized CyRPA at the apex of merozoites. The entire protein is conserved as shown by sequencing of the CyRPA encoding gene from a diverse range of P. falciparum isolates. CyRPA-specific mAbs substantially inhibited parasite growth in vitro as well as in a P. falciparum animal model based on NOD-scid IL2Rγnull mice engrafted with human erythrocytes. In contrast to other P. falciparum mouse models, this system generated very consistent results and evinced a dose-response relationship and therefore represents an unprecedented in vivo model for quantitative comparison of the functional potencies of malaria-specific Abs. Our data suggest a role for CyRPA in erythrocyte invasion by the merozoite. Inhibition of merozoite invasion by CyRPA-specific mAbs in vitro and in vivo renders this protein a promising malaria asexual blood-stage vaccine candidate Ag.

show abstract

“…8,2009 GPI-ANCHORED MICRONEMAL ANTIGEN 1875 the corresponding mRNA and protein (encoded by gene PB000129.01.0) have been detected in the P. berghei ookinete transcriptome (57) and proteome (23). The protein is present in the ookinete microneme proteome (31) and the gene identified as coding for putative secreted ookinete protein (PSOP) 9 (12). Interestingly, in the latter study the gene was disrupted, resulting in a striking reduction in infectivity of the mosquito gut and oocyst formation without a reduction in the number of ookinetes formed (12).…”

Section: Discussionmentioning

confidence: 99%

Novel Putative Glycosylphosphatidylinositol-Anchored Micronemal Antigen of Plasmodium falciparum That Binds to Erythrocytes

Hinds¹,

Green²,

Knuepfer³

et al. 2009

Eukaryot Cell

View full text Add to dashboard Cite

We have identified a new Plasmodium falciparum erythrocyte binding protein that appears to be located in the micronemes of the merozoite stage of the parasite and membrane linked through a glycosylphosphatidylinositol (GPI) anchor. The protein is designated GPI-anchored micronemal antigen (GAMA) and was identified by applying a set of selection criteria to identify previously uncharacterized merozoite proteins that may have a role in cell invasion. The protein is also present in the proteomes of the sporozoite and ookinete micronemes and is conserved throughout the genus. GAMA contains a novel domain that may be constrained by disulfide bonds and a predicted C-terminal hydrophobic sequence that is presumably replaced by the GPI. The protein is synthesized late during schizogony, processed into two fragments that are linked by a disulfide bond, and translocated to an apical location, which is probably the micronemes. In a proportion of free merozoites GAMA can also be detected on the parasite surface. Following erythrocyte invasion the bulk of the protein is shed in a soluble form, although a short C-terminal fragment may be carried into the newly invaded red blood cell. The protein was shown to bind reversibly to erythrocytes and therefore represents a new example of a host cell binding protein.Malaria is a potentially fatal disease that still devastates poverty-stricken nations more than a century after the protozoan parasite Plasmodium was identified as its causative agent. An accurate estimation of mortality remains elusive, although recent estimates suggest that just over 2.5 billion people live at risk of infection by Plasmodium falciparum (22), the species of the parasite responsible for the vast majority of deaths. It is believed that there are in the range of 500 million clinical episodes of P. falciparum infection each year, with the vast majority of the estimated 1 million fatalities occurring in children under the age of 5 years in sub-Saharan Africa (50). The often-fruitless efforts to develop a licensed malaria vaccine, along with the emergence of drug-resistant parasites and insecticide-resistant mosquitoes, highlight the urgency with which new points of attack to combat malaria need to be identified. The arrival of the P. falciparum genome sequence (15), along with its transcription (8, 34) and proteomic (14, 33) profiles, has provided great opportunities to identify novel drug and vaccine candidates.The asexual blood stage of the parasite is exclusively responsible for the clinical symptoms of malaria, and so, understandably, great efforts have gone into elucidating the molecular mechanism of erythrocyte invasion that is driven by the parasite's actomyosin motor. Although this process remains largely undefined, it is known that the secretory organelles located at the apical end of the invasive merozoite are pivotal. These organelles consist minimally of micronemes, rhoptries, and dense granules. Proteins belonging to the Duffy binding-like erythrocyte binding protein (18,37,49) and P. falciparum ...

show abstract

Reverse genetics screen identifies six proteins important for malaria development in the mosquito

Cited by 132 publications

References 54 publications

Discovery of GAMA, a Plasmodium falciparum Merozoite Micronemal Protein, as a Novel Blood-Stage Vaccine Candidate Antigen

Discovery of GAMA, a Plasmodium falciparum Merozoite Micronemal Protein, as a Novel Blood-Stage Vaccine Candidate Antigen

Passive Immunoprotection of Plasmodium falciparum-Infected Mice Designates the CyRPA as Candidate Malaria Vaccine Antigen

Novel Putative Glycosylphosphatidylinositol-Anchored Micronemal Antigen of Plasmodium falciparum That Binds to Erythrocytes

Contact Info

Product

Resources

About