Plasmodium falciparum AMA-1 erythrocyte binding peptides implicate AMA-1 as erythrocyte binding protein

Urquiza, Mauricio; Suárez, Jorge; Cárdenas, Constanza; López, Ramsés; Puentes, Álvaro; Chávez, Francisco P.; Calvo, Julio C.; Patarroyo, Manuel E.

doi:10.1016/s0264-410x(00)00185-7

Cited by 58 publications

(68 citation statements)

References 18 publications

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“…45 The same occurs with other conserved HABPs such as AMA-1-derived 4325 and MSP-derived 4044. The biological functions that have been determined for these native conserved HABPs (i.e., host cell binding ability [34][35][36][37][38][39][40] ) and immunological characteristics such as an immunological code of silence could thus be equal to or very similar to those presented by native proteins, strongly supporting our approach aimed at working with 15-25-mer, chemically synthesized peptides as a logical and rational methodology for minimal subunit-based synthetic vaccine development. FIGURE 2.…”

Section: Native and Modified Habp 3d Structurementioning

confidence: 79%

Emerging Rules for Subunit-Based, Multiantigenic, Multistage Chemically Synthesized Vaccines

2008

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S eventeen million people die of transmittable diseases and 2/3 of the world's population suffer them annually. Malaria, tuberculosis, AIDS, hepatitis, and reemerging and new diseases are a great threat to humankind. A logical and rational approach for vaccine development is thus desperately needed.Protein chemistry provides the best tools for tackling these problems. The tremendous complexity of microbes, the different pathways they use for invading host cells, and the immune responses they induce can only be resolved by using the minimum subunit-based (chemically produced ∼20-mer peptides), multiantigenic (most proteins involved in invasion), multistage (different invasion mechanisms) vaccine development approach.The most lethal form of malaria caused by Plasmodium falciparum (killing 3 million and affecting 500 million people worldwide annually) was used as target disease since many of its proteins, its invasion pathways, and its genome have been described recently. A New World primate (the Aotus monkey) is highly susceptibly to human malaria; its immune system molecules are 80 -100% identical to those of its human counterpart, making it an excellent model for vaccine development.Chemically synthesized ∼20-mer peptides, covering all the P. falciparum malaria proteins involved in red blood cell (RBC) invasion were synthesized by the classical t-Boc technology (based on synthetic SPf66 antimalarial vaccine information for identifying targets) and assayed in a highly sensitive, specific, and robust test for detecting receptor-ligand interactions between high-activity binding peptides (HABPs) and RBCs. HABPs were identified, some in which the molecule displays genetic variability (to be discarded due to their tremendous complexity) and elicits a strain-specific immune response and others that are conserved (no amino acid sequence variation).Conserved HABPs were synthesized in a polymeric form by adding cysteines at their N-and C-terminal ends to be used for monkey immunization. They became nonimmunogenic (no antibodies were induced) nonprotection inducers (monkeys were not protected against P. falciparum malaria challenge with a highly infective strain) suggesting a code of immunological silence or nonresponsiveness for these conserved HABPs.A large number of monkey trials involving a considerable number of Aotus monkeys were performed to break this code of immunological silence by replacing critical residues (determined by glycine peptide analogue scanning) to find that the following amino acid changes had to be made to render them antibody and protection inducing: FTR; WTY; LTH; ITN; MTK; PTD; QTE; CTT.The three-dimensional (3D) structure of >100 of these native modified HABPs (determined by 1 H NMR) revealed that the following structural changes had all to be achieved to allow a better fit into the major histocompatibility complex class II (MHC II)-peptide-TCR complex to properly activate the immune system: R-helix shortening, modifying their -turn, adopting segmental R-helix configuration, changing residue or...

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Section: Native and Modified Habp 3d Structurementioning

confidence: 79%

Emerging Rules for Subunit-Based, Multiantigenic, Multistage Chemically Synthesized Vaccines

2008

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“…Some reports have assigned an erythrocyte binding role to AMA-1 (7,27), although the ability of the AMA-1 ectodomain to bind erythrocytes remains controversial (13). Coexpression of Plasmodium chabaudi AMA-1 in P. falciparum increases the ability of P. falciparum merozoites to invade rodent erythrocytes (26), further implicating AMA-1 in erythrocyte recognition.…”

Section: Discussionmentioning

confidence: 99%

Mode of Action of Invasion-Inhibitory Antibodies Directed against Apical Membrane Antigen 1 of Plasmodium falciparum

et al. 2005

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Antibodies against apical membrane antigen 1 (AMA-1) of Plasmodium falciparum inhibit merozoite invasion into erythrocytes. Invasion-inhibitory polyclonal AMA-1 antibodies inhibit secondary proteolytic processing and surface redistribution of AMA-1 on merozoites. We present evidence supporting inhibition of processing and redistribution as probable causes of inhibition of invasion by polyclonal antibodies. Polyclonal anti-AMA-1 was much more inhibitory than monoclonal antibody (MAb) 4G2dc1 in an invasion assay. Although both polyclonal and monoclonal immunoglobulin G (IgG) inhibited secondary processing of the 66-kDa form of AMA-1, only polyclonal IgG caused its anomalous processing, inhibited its redistribution, and cross-linked soluble forms of AMA-1 on merozoites. Moreover, Fab fragments of polyclonal IgG that fail to cross-link did not show the enhancement of inhibitory effect over intact IgG, as observed in the case of Fab fragments of MAb 4G2dc1. We propose that although blocking of biologically important sites is a common direct mode of action of anti-AMA-1 antibodies, blocking of AMA-1 secondary processing and redistribution are additional indirect inhibitory mechanisms by which polyclonal IgG inhibits invasion. We also report a processing inhibition assay that uses a C-terminal AMA-1-specific MAb, 28G2dc1, to detect merozoite-bound remnants of processing (ϳ20 kDa from normal processing to 48 and 44 kDa and ϳ10 kDa from anomalous processing to a 52-kDa soluble form of AMA-1). The ratio of intensity of 10-kDa bands to the sum of 10-and 20-kDa bands was positively correlated with inhibition of invasion by polyclonal antibodies. This assay may serve as an important immunochemical correlate for inhibition of invasion.

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“…Domains I and II belong to the PAN module superfamily, suggesting that they may function in adhesion This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E05-04 -0281) on July 6, 2005. to protein or carbohydrate receptors (Pizarro et al, 2005). Antibodies against AMA1 inhibit invasion ( Thomas et al, 1984;Deans et al, 1988;Hehl et al, 2000;Kocken et al, 2000;Mitchell et al, 2004), as do phage-displayed peptides derived from (Urquiza et al, 2000) or with affinity for Plasmodium AMA1 (Li et al, 2002;Keizer et al, 2003). Together with trans-species complementation experiments (Triglia et al, 2000) and heterologous expression experiments (Fraser et al, 2001;Kato et al, 2005), these data suggest that AMA1 plays a role in host cell invasion, perhaps as an adhesin.…”

Section: Introductionmentioning

confidence: 96%

Conditional Expression ofToxoplasma gondiiApical Membrane Antigen-1 (TgAMA1) Demonstrates That TgAMA1 Plays a Critical Role in Host Cell Invasion

Mital

Meissner

Soldati

et al. 2005

MBoC

227

250

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Toxoplasma gondii is an obligate intracellular parasite and an important human pathogen. Relatively little is known about the proteins that orchestrate host cell invasion by T. gondii or related apicomplexan parasites (including Plasmodium spp., which cause malaria), due to the difficulty of studying essential genes in these organisms. We have used a recently developed regulatable promoter to create a conditional knockout of T. gondii apical membrane antigen-1 (TgAMA1). TgAMA1 is a transmembrane protein that localizes to the parasite's micronemes, secretory organelles that discharge during invasion. AMA1 proteins are conserved among apicomplexan parasites and are of intense interest as malaria vaccine candidates. We show here that T. gondii tachyzoites depleted of TgAMA1 are severely compromised in their ability to invade host cells, providing direct genetic evidence that AMA1 functions during invasion. The TgAMA1 deficiency has no effect on microneme secretion or initial attachment of the parasite to the host cell, but it does inhibit secretion of the rhoptries, organelles whose discharge is coupled to active host cell penetration. The data suggest a model in which attachment of the parasite to the host cell occurs in two distinct stages, the second of which requires TgAMA1 and is involved in regulating rhoptry secretion. INTRODUCTIONToxoplasma gondii is one of the one most common protozoan parasites of humans, infecting approximately one-third of the world's population. The disease caused by an acute T. gondii infection, toxoplasmosis, can be life threatening in the congenitally infected fetus and immunocompromised hosts. Like all members of the Phylum Apicomplexa, including Plasmodium spp. (the causative agents of malaria) and Cryptosporidium parvum (a significant worldwide cause of waterborne illness), T. gondii is an obligate intracellular parasite. Host cell invasion is a critical step in the pathogenesis of the diseases caused by apicomplexan parasites, including toxoplasmosis. T. gondii represents an excellent model system for studying the relatively conserved process of apicomplexan invasion, because of the ease with which this parasite can be cultured and genetically manipulated (Roos et al., 1994;Black and Boothroyd, 2000;Kim and Weiss, 2004).Host cell invasion by apicomplexan parasites is a complex, multistep process (reviewed in Black and Boothroyd, 2000;Chitnis and Blackman, 2000). In T. gondii, the asexual stage tachyzoites move over solid surfaces, including cells, by an unusual form of substrate-dependent gliding motility (Sibley et al., 1998;Hakansson et al., 1999). After the apical end of a parasite comes in contact with the host cell membrane, apical secretory organelles (micronemes and rhoptries) sequentially discharge their contents (Dubremetz et al., 1993;Carruthers and Sibley, 1997) and a zone of tight interaction forms between the two cells (Nichols and O'Connor, 1981;Dubremetz et al., 1985;Grimwood and Smith, 1995). An invagination in the host cell plasma membrane develops at the point ...

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Plasmodium falciparum AMA-1 erythrocyte binding peptides implicate AMA-1 as erythrocyte binding protein

Cited by 58 publications

References 18 publications

Emerging Rules for Subunit-Based, Multiantigenic, Multistage Chemically Synthesized Vaccines

Emerging Rules for Subunit-Based, Multiantigenic, Multistage Chemically Synthesized Vaccines

Mode of Action of Invasion-Inhibitory Antibodies Directed against Apical Membrane Antigen 1 of Plasmodium falciparum

Conditional Expression ofToxoplasma gondiiApical Membrane Antigen-1 (TgAMA1) Demonstrates That TgAMA1 Plays a Critical Role in Host Cell Invasion

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