scholarly journals In Vitro Studies with Recombinant Plasmodium falciparum Apical Membrane Antigen 1 (AMA1): Production and Activity of an AMA1 Vaccine and Generation of a Multiallelic Response

2002 ◽  
Vol 70 (12) ◽  
pp. 6948-6960 ◽  
Author(s):  
Michael C. Kennedy ◽  
Jin Wang ◽  
Yanling Zhang ◽  
Aaron P. Miles ◽  
Farideh Chitsaz ◽  
...  
Keyword(s):  
Apical Membrane ◽  
Allelic Diversity ◽  
Cross Reactivity ◽  
Human Infection ◽  
Apical Membrane Antigen 1 ◽  
Economy Of Scale ◽  
Apical Membrane Antigen ◽  
Immune Pressure ◽  
Single Antigen

ABSTRACT Apical membrane antigen 1 (AMA1) is regarded as a leading malaria blood-stage vaccine candidate. While the overall structure of AMA1 is conserved in Plasmodium spp., numerous AMA1 allelic variants of P. falciparum have been described. The effect of AMA1 allelic diversity on the ability of a recombinant AMA1 vaccine to protect against human infection by different P. falciparum strains is unknown. We characterize two allelic forms of AMA1 that were both produced in Pichia pastoris at a sufficient economy of scale to be usable for clinical vaccine studies. Both proteins were used to immunize rabbits, singly and in combination, in order to evaluate their immunogenicity and the ability of elicited antibodies to block the growth of different P. falciparum clones. Both antigens, when used alone, elicited high homologous anti-AMA1 titers, with reduced strain cross-reactivity. Similarly, sera from rabbits immunized with a single antigen were capable of blocking the growth of homologous parasite strains at levels theoretically sufficient to clear parasite infections. However, heterologous inhibition was significantly reduced, providing experimental evidence that AMA1 allelic diversity is a result of immune pressure. Encouragingly, rabbits immunized with a combination of both antigens exhibited titers and levels of parasite inhibition as good as those of the single-antigen-immunized rabbits for each of the homologous parasite lines, and consequently exhibited a broadening of allelic diversity coverage.

scholarly journals The Most Polymorphic Residue on Plasmodium falciparum Apical Membrane Antigen 1 Determines Binding of an Invasion-Inhibitory Antibody

2006 ◽  
Vol 74 (5) ◽  
pp. 2628-2636 ◽  
Author(s):  
A. M. Coley ◽  
K. Parisi ◽  
R. Masciantonio ◽  
J. Hoeck ◽  
J. L. Casey ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Apical Membrane ◽  
Site Directed Mutagenesis ◽  
Supporting Evidence ◽  
Inhibitory Antibody ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen ◽  
Immune Pressure ◽  
Polymorphic Residue

ABSTRACT Apical membrane antigen 1 (AMA1) is currently one of the leading malarial vaccine candidates. Anti-AMA1 antibodies can inhibit the invasion of erythrocytes by Plasmodium merozoites and prevent the multiplication of blood-stage parasites. Here we describe an anti-AMA1 monoclonal antibody (MAb 1F9) that inhibits the invasion of Plasmodium falciparum parasites in vitro. We show that both reactivity of MAb 1F9 with AMA1 and MAb 1F9-mediated invasion inhibition were strain specific. Site-directed mutagenesis of a fragment of AMA1 displayed on M13 bacteriophage identified a single polymorphic residue in domain I of AMA1 that is critical for MAb 1F9 binding. The identities of all other polymorphic residues investigated in this domain had little effect on the binding of the antibody. Examination of the P. falciparum AMA1 crystal structure localized this residue to a surface-exposed α-helix at the apex of the polypeptide. This description of a polymorphic inhibitory epitope on AMA1 adds supporting evidence to the hypothesis that immune pressure is responsible for the polymorphisms seen in this molecule.

scholarly journals Specificity of the Protective Antibody Response to Apical Membrane Antigen 1

2001 ◽  
Vol 69 (5) ◽  
pp. 3286-3294 ◽  
Author(s):  
Anthony N. Hodder ◽  
Pauline E. Crewther ◽  
Robin F. Anders
Keyword(s):  
Apical Membrane ◽  
Affinity Purification ◽  
Point Mutations ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen ◽  
Potential Vaccine ◽  
Inhibitory Antibodies ◽  
Domain I ◽  
The Impact

ABSTRACT Apical membrane antigen 1 (AMA1) is considered one of the leading candidates for inclusion in a vaccine against blood stages ofPlasmodium falciparum. Although the ama1 gene is relatively conserved compared to those for some other potential vaccine components, numerous point mutations have resulted in amino acid substitutions at many sites in the polypeptide. The polymorphisms in AMA1 have been attributed to the diversifying selection pressure of the protective immune responses. It was therefore of interest to investigate the impact of sequence diversity in P. falciparum AMA1 on the ability of anti-AMA1 antibodies to inhibit the invasion of erythrocytes in vitro by P. falciparummerozoites. For these studies, we used antibodies to recombinantP. falciparum 3D7 AMA1 ectodomain, which was prepared for testing in early clinical trials. Antibodies were raised in rabbits to the antigen formulated in Montanide ISA720, and human antibodies to AMA1 were isolated by affinity purification from the plasma of adults living in regions of Papua New Guinea where malaria is endemic. Both rabbit and human anti-AMA1 antibodies were found to be strongly inhibitory to the invasion of erythrocytes by merozoites from both the homologous and two heterologous lines of P. falciparum. The inhibitory antibodies targeted both conserved and strain-specific epitopes within the ectodomain of AMA1; however, it appears that the majority of these antibodies reacted with strain-specific epitopes in domain I, the N-terminal disulfide-bonded domain, which is the most polymorphic region of AMA1.

scholarly journals A Diversity-Covering Approach to Immunization with Plasmodium falciparum Apical Membrane Antigen 1 Induces Broader Allelic Recognition and Growth Inhibition Responses in Rabbits

2008 ◽  
Vol 76 (6) ◽  
pp. 2660-2670 ◽  
Author(s):  
Edmond J. Remarque ◽  
Bart W. Faber ◽  
Clemens H. M. Kocken ◽  
Alan W. Thomas
Keyword(s):  
Plasmodium Falciparum ◽  
Amino Acid ◽  
Growth Inhibition ◽  
Apical Membrane ◽  
Recombinant Expression ◽  
Methylotrophic Yeast ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen ◽  
Amino Acid Variability

ABSTRACT Plasmodium falciparum apical membrane antigen 1 (PfAMA1), a candidate malaria vaccine, is polymorphic. This polymorphism is believed to be generated predominantly under immune selection pressure and, as a result, may compromise attempts at vaccination. Alignment of 355 PfAMA1 sequences shows that around 10% of the 622 amino acid residues can vary between alleles and that linkages between polymorphic residues occur. Using this analysis, we have designed three diversity-covering (DiCo) PfAMA1 sequences that take account of these linkages and, when taken together, on average incorporate 97% of amino acid variability observed. For each of the three DiCo sequences, a synthetic gene was constructed and used to transform the methylotrophic yeast Pichia pastoris, allowing recombinant expression. All three DiCo proteins were reactive with the reduction-sensitive monoclonal antibody 4G2, suggesting the DiCo sequences had conformations similar to those of naturally occurring PfAMA1. Rabbits were immunized with FVO strain PfAMA1 or with the DiCo proteins either individually or as a mixture. Antibody titers and the ability to inhibit parasite growth in vitro were determined. Animals immunized with the DiCo mix performed similarly to animals immunized with FVO AMA1 when measured against FCR3 strain parasites but outperformed animals immunized with FVO AMA1 when assessed against other strains. The levels of growth inhibition (∼70%) induced by the mix of three DiCo proteins were comparable for FVO, 3D7, and HB3, suggesting that a considerable degree of diversity in AMA1 is adequately covered. This suggests that vaccines based upon the DiCo mix approach provide a broader functional immunity than immunization with a single allele.

scholarly journals Allelic Diversity and Naturally Acquired Allele-Specific Antibody Responses to Plasmodium falciparum Apical Membrane Antigen 1 in Kenya

2010 ◽  
Vol 78 (11) ◽  
pp. 4625-4633 ◽  
Author(s):  
Faith H. A. Osier ◽  
Gareth D. Weedall ◽  
Federica Verra ◽  
Linda Murungi ◽  
Kevin K. A. Tetteh ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Allele Frequency ◽  
Apical Membrane ◽  
Balancing Selection ◽  
Allelic Diversity ◽  
Frequency Distributions ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen ◽  
Allele Specific ◽  
The Impact

ABSTRACT Although Plasmodium falciparum apical membrane antigen 1 (AMA1) is a leading malaria vaccine candidate, extensive allelic diversity may compromise its vaccine potential. We have previously shown that naturally acquired antibodies to AMA1 were associated with protection from clinical malaria in this Kenyan population. To assess the impact of allelic diversity on naturally acquired immunity, we first sequenced the ectodomain-encoding region of P. falciparum ama1 from subjects with asymptomatic, mild, and severe malaria and measured allele frequency distributions. We then measured antibodies to three allelic AMA1 proteins (AMA1_3D7, AMA1_FVO, and AMA1_HB3) and used competition enzyme-linked immunosorbent assays (ELISAs) to analyze allele-specific antibodies. Seventy-eight unique haplotypes were identified from 129 alleles sampled. No clustering of allelic haplotypes with disease severity or year of sampling was observed. Differences in nucleotide frequencies in clinical (severe plus mild malaria) versus asymptomatic infections were observed at 16 polymorphic positions. Allele frequency distributions were indicative of balancing selection, with the strongest signature being identified in domain III (Tajima's D = 2.51; P < 0.05). Antibody reactivities to each of the three allelic AMA1 proteins were highly correlated (P < 0.001 for all pairwise comparisons). Although antibodies to conserved epitopes were abundant, 48% of selected children with anti-AMA1 IgG (n = 106) had detectable reactivity to allele-specific epitopes as determined by a competition ELISA. Antibodies to both conserved and allele-specific epitopes in AMA1 may contribute to clinical protection.

scholarly journals In Immunization with Plasmodium falciparum Apical Membrane Antigen 1, the Specificity of Antibodies Depends on the Species Immunized

2007 ◽  
Vol 75 (12) ◽  
pp. 5827-5836 ◽  
Author(s):  
Kazutoyo Miura ◽  
Hong Zhou ◽  
Olga V. Muratova ◽  
Andrew C. Orcutt ◽  
Birgitte Giersing ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Growth Inhibition ◽  
Vaccine Development ◽  
Apical Membrane ◽  
Rabbit Model ◽  
Enzyme Linked Immunosorbent Assay ◽  
Allelic Polymorphism ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen

ABSTRACT At least a million people, mainly African children under 5 years old, still die yearly from malaria, and the burden of disease and death has increased. Plasmodium falciparum apical membrane antigen 1 (PfAMA1) is one of the most promising blood-stage malarial vaccine candidates. However, the allelic polymorphism observed in this protein is a potential stumbling block for vaccine development. To overcome the polymorphism- and strain-specific growth inhibition in vitro, we previously showed in a rabbit model that vaccination with a mixture of two allelic forms of PfAMA1 induced parasite growth-inhibitory antisera against both strains of P. falciparum parasites in vitro. In the present study, we have established that, in contrast to a single-allele protein, the antigen mixture elicits primarily antibodies recognizing antigenic determinants common to the two antigens, as judged by an antigen reversal growth inhibition assay (GIA). We also show that a similar reactivity pattern occurs after immunization of mice. By contrast, sera from rhesus monkeys do not distinguish the two alleles when tested by an enzyme-linked immunosorbent assay or by GIA, regardless of whether the immunogen is a single AMA1 protein or the mixture. This is the first report that a malarial vaccine candidate induced different specificities of functional antibodies depending on the animal species immunized. These observations, as well as data available on human immune responses in areas of endemicity, suggest that polymorphism in the AMA1 protein may not be as formidable a problem for vaccine development as anticipated from studies with rabbits and mice.

scholarly journals Structure of Rhoptry Neck Protein 2 is essential for the interaction in vitro with Apical Membrane Antigen 1 in Plasmodium vivax

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Perla Salgado-Mejias ◽  
Flavio L. Alves ◽  
Kátia S. Françoso ◽  
Karin A. Riske ◽  
Emerson R. Silva ◽  
...  
Keyword(s):  
Plasmodium Vivax ◽  
Apical Membrane ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen ◽  
Rhoptry Neck Protein

Molecular cloning, characterization and antigenicity ofBabesiasp. BQ1 (Lintan) (Babesiacf.motasi) apical membrane antigen-1 (AMA-1)

Parasitology ◽  
2016 ◽  
Vol 144 (5) ◽  
pp. 641-649 ◽  
Author(s):  
QINGLI NIU ◽  
ZHIJIE LIU ◽  
JIFEI YANG ◽  
GUIQUAN GUAN ◽  
YUPING PAN ◽  
...  
Keyword(s):  
Amino Acid ◽  
Apical Membrane ◽  
Amino Acid Sequences ◽  
Amino Acid Residues ◽  
Gene Characterization ◽  
Reading Frame ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen ◽  
Potential Vaccine

SUMMARYApical membrane antigen-1 (AMA-1) has been described as a potential vaccine candidate in apicomplexan parasites. Here we characterize theama-1gene. The full-lengthama-1gene ofBabesiasp. BQ1 (Lintan) (BLTAMA-1) is 1785 bp, which contains an open reading frame (ORF) encoding a 65-kDa protein of 594 amino acid residues; by definition, the 5′ UTR precedes the first methionine of the ORF. Phylogenetic analysis based on AMA-1 amino acid sequences clearly separated Piroplasmida from other Apicomplexa parasites. TheBabesiasp. BQ1 (Lintan) AMA-1 sequence is most closely associated with that ofB. ovataandB. bigemina, with high bootstrap value. A recombinant protein encoding a conserved region and containing ectodomains I and II of BLTAMA-1 was constructed. BLTrAMA-1-DI/DII proteins were tested for reactivity with sera from sheep infected byBabesiasp. BQ1 (Lintan). In Western-blot analysis, nativeBabesiasp. BQ1 (Lintan) AMA-1 proteins were recognized by antibodies raised in rabbits against BLTrAMA-1in vitro. The results of this study are discussed in terms of gene characterization, taxonomy and antigenicity.

scholarly journals Eimeria tenella Eimeria-specific protein that interacts with apical membrane antigen 1 (EtAMA1) is involved in host cell invasion

2019 ◽  
Author(s):  
Cong Li ◽  
Qiping Zhao ◽  
Shunhai Zhu ◽  
Qingjie Wang ◽  
Haixia Wang ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Invasion ◽  
Apical Membrane ◽  
Specific Protein ◽  
Host Cells ◽  
Bimolecular Fluorescence Complementation ◽  
Host Cell Invasion ◽  
Apical Membrane Antigen 1 ◽  
Apical Membrane Antigen

Abstract Apical membrane antigen 1 (AMA1), which is released from micronemes and is conserved across all apicomplexans, plays a central role in the host cell invasion. In this study, we characterized one putative Et AMA1-interacting protein, E. tenella Eimeria -specific protein ( Et Esp). The interaction between Et AMA1 and Et Esp was confirmed with bimolecular fluorescence complementation (BiFC) in vivo and by glutathione S-transferase (GST) fusion protein pull-down (GST pull-down) in vitro . We showed that Et Esp is differentially expressed during distinct phases of the parasite life cycle by using qPCR and western blotting. Immunofluorescence analysis showed that the Et Esp protein is mainly distributed on the parasite surface, and that the expression of this protein increases during the development of the parasite in the host cells. Using staurosporine, we showed that Et Esp is a micronemal protein secreted by sporozoites. In inhibition tests, a polyclonal anti-r Et Esp antibody attenuated the capacity of E. tenella to invade host cells in vitro . These data have implications for the use of Et AMA1 or Et AMA1-interacting proteins as targets in intervention strategies against avian coccidiosis.

Sign in / Sign up

Export Citation Format

Share Document