Biochemical and Immunological Characterization of Bacterially Expressed and Refolded<i>Plasmodium falciparum</i>42-Kilodalton C-Terminal Merozoite Surface Protein 1

Singh, Sanjay; Kennedy, Michael; Long, Carole A.; Saul, Allan; Miller, Louis H.; Stowers, Anthony W.

doi:10.1128/iai.71.12.6766-6774.2003

Cited by 66 publications

(67 citation statements)

References 31 publications

(60 reference statements)

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“…The present study demonstrates that in a naturally exposed population, the invasion of inhibition assay was in fact a superior predictor of protection from infection. Although we did not determine the genotypes of MSP-1 19 alleles in infected study subjects, prior studies have demonstrated extensive cross-reactivity of IIA to the variant MSP-1 19 and MSP-1 42 epitopes (15,45), suggesting that the levels of IIA to other alleles possibly circulating in this area would be similar to the MAD-20 allele tested in this study.…”

Section: Discussionmentioning

confidence: 98%

Evidence That Invasion-Inhibitory Antibodies Specific for the 19-kDa Fragment of Merozoite Surface Protein-1 (MSP-119) Can Play a Protective Role against Blood-Stage Plasmodium falciparum Infection in Individuals in a Malaria Endemic Area of Africa

John

O’Donnell

Sumba

et al. 2004

The Journal of Immunology

145

157

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The C-terminal 19-kDa fragment of Plasmodium falciparum merozoite surface protein-1 (MSP-119) is a target of protective Abs against blood-stage infection and a leading candidate for inclusion in a human malaria vaccine. However, the precise role, relative importance, and mechanism of action of Abs that target this protein remain unclear. To examine the potential protective role of Abs to MSP-119 in individuals naturally exposed to malaria, we conducted a treatment time to infection study over a 10-wk period in 76 residents of a highland area of western Kenya during a malaria epidemic. These semi-immune individuals were not all equally susceptible to reinfection with P. falciparum following drug cure. Using a new neutralization assay based on transgenic P. falciparum expressing the P. chabaudi MSP-119 orthologue, individuals with high-level MSP-119-specific invasion-inhibitory Abs (>75th percentile) had a 66% reduction in the risk of blood-stage infection relative to others in the population (95% confidence interval, 3–88%). In contrast, high levels of MSP-119 IgG or IgG subclass Abs measured by enzyme immunoassay with six different recombinant MSP-119 Ags did not correlate with protection from infection. IgG Abs measured by serology and functional invasion-inhibitory activity did not correlate with each other. These findings implicate an important protective role for MSP-119-specific invasion inhibitory Abs in immunity to blood-stage P. falciparum infection, and suggest that the measurement of MSP-119 specific inhibitory Abs may serve as an accurate correlate of protection in clinical trials of MSP-1-based vaccines.

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Section: Discussionmentioning

confidence: 98%

Evidence That Invasion-Inhibitory Antibodies Specific for the 19-kDa Fragment of Merozoite Surface Protein-1 (MSP-119) Can Play a Protective Role against Blood-Stage Plasmodium falciparum Infection in Individuals in a Malaria Endemic Area of Africa

John

O’Donnell

Sumba

et al. 2004

The Journal of Immunology

145

157

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“…Parasite extract equivalent to Ϸ2 ϫ 10 6 schizonts were loaded per lane of the 4-12% gradient Bis-Tris gel under reducing conditions. On electrophoretic separation, proteins were transferred to a nitrocellulose membrane and subjected to immunoblot analysis as described earlier (31). In brief, the blot was blocked with 5% skimmed milk.…”

Section: Pfrom1 Epitope Tagging and Generation Of Transgenic Parasitesmentioning

confidence: 99%

Mononeme: A new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease

Singh

Plassmeyer

Gaur

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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Compartmentalization of proteins into subcellular organelles in eukaryotic cells is a fundamental mechanism of regulating complex cellular functions. Many proteins of Plasmodium falciparum merozoites involved in invasion are compartmentalized into apical organelles. We have identified a new merozoite organelle that contains P. falciparum rhomboid-1 (PfROM1), a protease that cleaves the transmembrane regions of proteins involved in invasion. By immunoconfocal microscopy, PfROM1 was localized to a single, thread-like structure on one side of the merozoites that appears to be in close proximity to the subpellicular microtubules. PfROM1 was not found associated with micronemes, rhoptries, or dense granules, the three identified secretory organelles of invasion. Release of merozoites from schizonts resulted in the movement of PfROM1 from the lateral asymmetric localization to the merozoite apical pole and the posterior pole. We have named this single thread-like organelle in merozoites, the mononeme. malaria A picomplexa are named for a set of secretory organelles (rhoptries, micronemes, and dense granules) found at the apical end of these parasites, the end that invades cells in the vertebrate host (1). These organelles were first identified by their distinct morphological appearances in transmission electron microscopy (2-4). Many parasite proteins required for invasion of erythrocytes are segregated into the micronemes (5, 6). For example, Plasmodium falciparum apical membrane antigen 1 (AMA1) is held in the micronemes in merozoites inside of erythrocytes. Release from the erythrocyte triggers the movement of AMA1 to the cell surface where it functions in invasion (7,8). Similarly, rhoptries sequester a different set of proteins and their contents are released onto the erythrocyte surface (4, 9), presumably to break the local cytoskeleton and to initiate formation of the parasitophorous vacuole. Taken together, these observations provide evidence for compartmentalization of parasite proteins into distinct organelles with related functions in invasion. Presumably, such compartmentalization provides a mechanism for orchestrating the timing of delivery or activity of the proteins during the complex process of invasion.Apicomplexan rhomboid proteases have been implicated to play an important role in host cell invasion (10, 11). PfROM1 substrates have been identified in P. falciparum by using a mammalian cell-based proteolytic assay (12) that identified various micronemal proteins as potential substrates including AMA1. Because AMA1 has been implicated as essential for invasion, separation of PfROM1 from this substrate within the parasite may be important to prevent premature cleavage. Studies defining the spatiotemporal distribution of PfROM1 in P. falciparum merozoites are, therefore, likely to contribute to a clearer understanding of its role in erythrocyte invasion. Expression of hemagglutinin (HA)-tagged P. falciparum rhomboid-1 (PfROM1) localizes it to a new subcellular compartment distinct from other known meroz...

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“…P. falciparum MSP1 19 -specific invasion inhibitory activity has been shown to be associated with resistance to reinfection in Kenyans (6). Antibody-mediated protection against parasite infection challenge was produced in animal models immunized with either 42-kDa MSP-1 or MSP-1 19 (7)(8)(9)(10)(11). Several studies have shown that MSP-1, especially MSP-1 19 , is a target of protective antibodies against the blood-stage infection (12,13).…”

Section: Introductionmentioning

confidence: 99%

Effect of GPI anchor moiety on the immunogenicity of DNA plasmids encoding the 19‐kDa C‐terminal portion of Plasmodium falciparum MSP‐1

Basagoudanavar

Gowda

2008

Parasite Immunology

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SUMMARY The glycosylphosphatidylinositol (GPI)‐anchored Plasmodium falciparum merozoite surface protein 1 (MSP‐1) is a widely studied malaria vaccine candidate. The C‐terminal 19‐kDa portion of MSP‐1 (MSP‐119) is of particular interest because this polypeptide moiety remains bound to the parasite even after erythrocyte invasion, while the remainder of MSP‐1 is shed during invasion. Studies have shown that antibodies against MSP‐119 inhibit merozoite invasion of erythrocytes efficiently, and that MSP‐119 produces protective immunity in mice and monkeys. To investigate the efficacy of MSP‐119 DNA vaccine and role of GPI anchor moiety in the immunogenicity of MSP‐119, we constructed expression vectors that produce MSP‐119 as either secretory or GPI‐anchored polypeptide. Both constructs efficiently expressed MSP‐119 in transfected HEK‐293 cells. While the recombinant plasmid lacking GPI anchor signal sequence expressed MSP‐119 mainly as secreted polypeptide, that containing GPI anchor signal sequence produced GPI‐anchored MSP‐119 on cell surface. In immunized mice, both constructs produced substantial levels of MSP‐119‐specific IgG1, IgG2a, IgG2b, IgG3, IgA and IgM antibodies. In both cases, the IgG1 level was significantly higher than other isotypes. Interestingly, the plasmid containing GPI anchor signal sequence produced significantly higher levels of IgG2a and IgG2b than the plasmid that lacks GPI signal sequence.

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Biochemical and Immunological Characterization of Bacterially Expressed and RefoldedPlasmodium falciparum42-Kilodalton C-Terminal Merozoite Surface Protein 1

Cited by 66 publications

References 31 publications

Evidence That Invasion-Inhibitory Antibodies Specific for the 19-kDa Fragment of Merozoite Surface Protein-1 (MSP-119) Can Play a Protective Role against Blood-Stage Plasmodium falciparum Infection in Individuals in a Malaria Endemic Area of Africa

Evidence That Invasion-Inhibitory Antibodies Specific for the 19-kDa Fragment of Merozoite Surface Protein-1 (MSP-119) Can Play a Protective Role against Blood-Stage Plasmodium falciparum Infection in Individuals in a Malaria Endemic Area of Africa

Mononeme: A new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease

Effect of GPI anchor moiety on the immunogenicity of DNA plasmids encoding the 19‐kDa C‐terminal portion of Plasmodium falciparum MSP‐1

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