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John H Adams - One of the best experts on this subject based on the ideXlab platform.
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strain transcending inhibitory antibodies against homologous and heterologous strains of duffy binding protein Region Ii
PLOS ONE, 2016Co-Authors: Sudarat Wongkidakarn, Jetsumon Sattabongkot, Amy M Mchenry, John H Adams, Patchanee ChootongAbstract:Duffy binding protein Region Ii (DBPIi) is a promising vaccine candidate against vivax malaria. However, polymorphisms of DBPIi are the major obstacle to designing a successful vaccine. Here, we examined whether anti-DBPIi antibodies from individual P. vivax exposures provide strain-transcending immunity and whether their presence is associated with DBPIi haplotypes found in patients with acute P. vivax. The ability of antibodies to inhibit DBL-TH-erythrocyte binding was tested by COS7 erythrocyte binding inhibition assay. Seven samples of high responders (HR) were identified from screening anti-DBPIi levels. HR no.3 and HR no.6 highly inhibited all DBL-TH binding to erythrocytes, by >80%. Antibodies from these two patients’ plasma had the potential to be broadly inhibitory against DBL-TH1, -TH2, -TH6, -TH7, -TH8 and -TH9 haplotypes when plasma was serially diluted from 1:500 to 1:2000. To further examine the association of DBPIi haplotypes and the ability of antibodies to broadly inhibit DBL-TH variants, the individual samples underwent sequencing analysis and the inhibitory function of the anti-DBPIi antibodies was tested. The patterns of DBPIi polymorphisms in acute patients were classified into two groups, DBPIi Sal I (55%) and DBL-TH variants (45%). Plasma from Sal I and DBPIi-TH patients who had the highest inhibition against Sal I or DBL-TH4 and -TH5 was serially diluted from 1:500 to 1:2000 and their inhibitory capacity was tested against a panel of DBL-TH haplotypes. Results provided evidence of both strain-transcending inhibition as well as strain-specific inhibition by antibodies that blocked erythrocyte binding against some DBL-TH variants and against homologous alleles. This study demonstrated broad inhibition by anti-DBPIi antibodies against DBL-TH haplotypes in natural P. vivax exposed individuals. The identification of conserved epitopes among DBL-TH may have implications for vaccine development of a DBPIi-based vaccine against diverse P. vivax infections.
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the association of duffy binding protein Region Ii polymorphisms and its antigenicity in plasmodium vivax isolates from thailand
Parasitology International, 2014Co-Authors: Patchanee Chootong, Francis B. Ntumngia, Amy M Mchenry, Jetsumon Sattabongkot, John H AdamsAbstract:Plasmodium vivax Duffy binding protein Ii (DBPIi) plays an important role in reticulocyte invasion and is a potential vaccine candidate against vivax malaria. However, polymorphisms in DBPIi are a challenge for the successful design of a broadly protective vaccine. In this study, the genetic diversity of DBPIi among Thai isolates was analyzed from Plasmodium vivax-infected blood samples and polymorphism characters were defined with the MEGA4 program. Sequence analysis identified 12 variant residues that are common among Thai DBPIi haplotypes with variant residues L333F, L424I, W437R and I503K having the highest frequency. Variant residue D384K occurs in combination with either E385K or K386N/Q. Additionally, variant residue L424I occurs in conjunction with W437R in most Thai DBPIi alleles and these variants frequently occur in combination with the I503K variant. The polymorphic patterns of Thai isolates were defined into 9 haplotypes (Thai DBL-1, -2, -3, etc.…). Thai DBL-2, -5, -6 haplotypes are the most common DBPIi variants in Thai residents. To study the association of these Thai DBPIi polymorphisms with antigenic character, the functional inhibition of anti-DBPIi monoclonal antibodies against a panel of Thai DBL variants was characterized by an in vitro erythrocyte binding inhibition assay. The functional inhibition of anti-DBPIi monoclonal antibodies 3C9, 2D10 and 2C6 against Thai variants was significantly different, suggesting that polymorphisms of Thai DBPIi variants alter the antigenic character of the target epitopes. In contrast, anti-DBPIi monoclonal antibody 2H2 inhibited all Thai DBPIi variants equally well. Our results suggest that the immune efficacy of a DBPIi vaccine will depend on the specificity of the anti-DBPIi antibodies induced and that it is preferable to optimize responses to conserved epitopes for broadly neutralizing protection against P. vivax.
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immunogenicity of a synthetic vaccine based on plasmodium vivax duffy binding protein Region Ii
Clinical and Vaccine Immunology, 2014Co-Authors: Francis B. Ntumngia, Miriam T. George, Jesse Schloegel, Samantha J. Barnes, Amy M Mchenry, John H AdamsAbstract:Molecules that play a role in Plasmodium merozoite invasion of host red blood cells represent attractive targets for blood-stage vaccine development against malaria. In Plasmodium vivax, merozoite invasion of reticulocytes is mediated by the Duffy binding protein (DBP), which interacts with its cognate receptor, the Duffy antigen receptor for chemokines, on the surface of reticulocytes. The DBP ligand domain, known as Region Ii (DBPIi), contains the critical residues for receptor recognition, making it a prime target for vaccine development against blood-stage vivax malaria. In natural infections, DBP is weakly immunogenic and DBPIi allelic variation is associated with strain-specific immunity, which may compromise vaccine efficacy. In a previous study, a synthetic vaccine termed DEKnull that lacked an immunodominant variant epitope in DBPIi induced functional antibodies to shared neutralizing epitopes on the native Sal1 allele. Anti-DEKnull antibody titers were lower than anti-Sal1 titers but produced more consistent, strain-transcending anti-DBPIi inhibitory responses. In this study, we further characterized the immunogenicity of DEKnull, finding that immunization with recombinant DEKnull produced an immune response comparable to that obtained with native recombinant DBP alleles. Further investigation of DEKnull is necessary to enhance its immunogenicity and broaden its specificity.
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immunogenicity of single versus mixed allele vaccines of plasmodium vivax duffy binding protein Region Ii
Vaccine, 2013Co-Authors: Francis B. Ntumngia, Miriam T. George, Jesse Schloegel, Samantha J. Barnes, Amy M Mchenry, Sandra Kennedy, John H AdamsAbstract:The Duffy binding protein (DBP) of Plasmodium vivax is vital for host erythrocyte invasion. DBP Region Ii (DBPIi) contains critical residues for receptor recognition and anti-DBPIi antibodies have been shown to inhibit erythrocyte binding and invasion, thereby making the molecule an attractive vaccine candidate against P. vivax blood stages. Similar to other blood-stage antigens, allelic variation within the DBPIi and associated strain-specific immunity is a major challenge for development of a broadly effective vaccine against P. vivax malaria. We hypothesized that immunization with a vaccine composed of multiple DBP alleles or a modified epitope DBP (DEKnull) will be more effective in producing a broadly reactive and inhibitory antibody response to diverse DBPIi alleles than a single allele vaccine. In this study, we compared single, naturally occurring DBPIi allele immunizations (Sal1, 7.18, P) and DEKnull with a combination of (Sal1, 7.18, P) alleles. Quantitative analysis by ELISA demonstrated that the multiple allele vaccine tend to be more immunogenic than any of the single allele vaccines when tested for reactivity against a panel of DBPIi allelic variants whereas DEKnull was less immunogenic than the mixed-allele vaccine but similar in reactivity to the single allele vaccines. Further analysis for functional efficacy by in vitro erythrocyte-binding inhibition assays demonstrated that the multiple allele immunization produced a stronger strain-neutralizing response than the other vaccination strategies even though inhibition remained biased toward some alleles. Overall, there was no correlation between antibody titer and functional inhibition. These data suggest that a multiple allele vaccine may enhance immunogenicity of a DBPIi vaccine but further investigation is required to optimize this vaccine strategy to achieve broader coverage against global P. vivax strains.
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measurement of antibody levels against Region Ii of the erythrocyte binding antigen 175 of plasmodium falciparum in an area of malaria holoendemicity in western kenya
Infection and Immunity, 2004Co-Authors: Eunita A Ohas, John H Adams, John N Waitumbi, Alloys S S Orago, Arnoldo Barbosa, David E Lanar, Jose A StouteAbstract:Region Ii of the 175-kDa erythrocyte-binding antigen (EBA-175RIi) of Plasmodium falciparum is functionally important in sialic acid-dependent erythrocyte invasion and is considered a prime target for an invasion-blocking vaccine. The objectives of this study were to (i) determine the prevalence of anti-EBA-175RIi antibodies in a naturally exposed population, (Ii) determine whether naturally acquired antibodies have a functional role by inhibiting binding of EBA-175RIi to erythrocytes, and (Iii) determine whether antibodies against EBA-175RIi correlate with immunity to clinical malaria. We treated 301 lifelong residents of an area of malaria holoendemicity in western Kenya for malaria, monitored them during a high-transmission season, and identified 33 individuals who were asymptomatic despite parasitemia (clinically immune). We also identified 50 clinically susceptible individuals to serve as controls. These 83 individuals were treated and monitored again during the subsequent low-transmission season. Anti-EBA-175RIi antibodies were present in 98.7% of the individuals studied. The antibody levels were relatively stable between the beginning and end of the high-transmission season and correlated with the plasma EBA-175RIi erythrocyte-binding-inhibitory activity. There was no difference in anti-EBA-175RIi levels or plasma EBA-175RIi erythrocyte-binding-inhibitory activity between clinically immune and clinically susceptible groups. However, these parameters were higher in nonparasitemic than in parasitemic individuals at enrollment. These results suggest that although antibodies against EBA-175RIi may be effective in suppressing some of the wild parasite strains, EBA-175RIi is unlikely to be effective as a monovalent vaccine against malaria, perhaps due to allelic heterogeneity and/or presence of sialic acid-independent strains.
Kathleen J Moch - One of the best experts on this subject based on the ideXlab platform.
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Delineation of Stage Specific Expression of Plasmodium falciparum EBA-175 by Biologically Functional Region Ii Monoclonal Antibodies
2016Co-Authors: B. Kim, David L Narum, Rana Chattopadhyay, Adriana Ahumada, David J Haynes, Steven R Fuhrmann, Jennifer N Wingard, Hong Liang, Lee Sim, Kathleen J MochAbstract:Background: The malaria parasite Plasmodium falciparum EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding Region (RIi) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains. Methods and Findings: Five mAbs specific for F1 or F2 were generated. Three mAbs specific for F2 potently blocked binding of EBA-175 to erythrocytes, and merozoite invasion of erythrocytes (IC50 10 to 100 mg/ml IgG in growth inhibition assays). A mAb specific for F1 blocked EBA-175 binding and merozoite invasion less effectively. The difference observed between the IC50 of F1 and F2 mAbs was not due to differing association and disassociation rates as determined by surface plasmon resonance. Four of the mAbs recognized conformation-dependent epitopes within F1 or F2. Used in combination, F1 and F2 mAbs blocked the binding of native EBA-175 to erythrocytes and inhibited parasite invasion synergistically in vitro. MAb R217, the most potent, did not recognize sporozoites, 3-day hepatocyte stage parasites, nor rings, trophozoites, gametocytes, retorts, ookinetes, and oocysts but recognized 6-day hepatocyte stage parasites, and schizonts. Even thoug
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delineation of stage specific expression of plasmodium falciparum eba 175 by biologically functional Region Ii monoclonal antibodies
PLOS ONE, 2011Co-Authors: David L Narum, Rana Chattopadhyay, Adriana Ahumada, David J Haynes, Steven R Fuhrmann, Jennifer N Wingard, Hong Liang, Kathleen J MochAbstract:Background The malaria parasite Plasmodium falciparum EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding Region (RIi) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains. Methods and Findings Five mAbs specific for F1 or F2 were generated. Three mAbs specific for F2 potently blocked binding of EBA-175 to erythrocytes, and merozoite invasion of erythrocytes (IC50 10 to 100 µg/ml IgG in growth inhibition assays). A mAb specific for F1 blocked EBA-175 binding and merozoite invasion less effectively. The difference observed between the IC50 of F1 and F2 mAbs was not due to differing association and disassociation rates as determined by surface plasmon resonance. Four of the mAbs recognized conformation-dependent epitopes within F1 or F2. Used in combination, F1 and F2 mAbs blocked the binding of native EBA-175 to erythrocytes and inhibited parasite invasion synergistically in vitro. MAb R217, the most potent, did not recognize sporozoites, 3-day hepatocyte stage parasites, nor rings, trophozoites, gametocytes, retorts, ookinetes, and oocysts but recognized 6-day hepatocyte stage parasites, and schizonts. Even though efficient at blocking binding to erythrocytes and inhibiting invasion into erythrocytes, MAb R217 did not inhibit sporozoite invasion and development in hepatocytes in vitro. Conclusions The role of the F1 and F2 domains in erythrocyte invasion and binding was elucidated with mAbs. These mAbs interfere with native EBA-175 binding to erythrocyte in a synergistic fashion. The stage specific expression of EBA-175 showed that the primary focus of activity was the merozoite stage. A recombinant RIi protein vaccine consisting of both F1 and F2 domains that could induce synergistic activity should be optimal for induction of antibody responses that interfere with merozoite invasion of erythrocytes.
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protection of aotus monkeys by plasmodium falciparum eba 175 Region Ii dna prime protein boost immunization regimen
The Journal of Infectious Diseases, 2001Co-Authors: Trevor R Jones, David L Narum, David J Haynes, Steven R Fuhrmann, Kathleen J Moch, Hong Liang, Alfonso S Gozalo, Joao C AguiarAbstract:: Aotus monkeys received 4 doses of Plasmodium falciparum EBA-175 Region Ii vaccine as plasmid DNA (Dv-Dv) or recombinant protein in adjuvant (Pv-Pv) or as 3 doses of DNA and 1 dose of protein (Dv-Pv). After 3 doses, antibody titers were approximately 10(4) in DNA-immunized monkeys and 10(6) in protein-immunized monkeys. A fourth dose did not significantly boost antibody responses in the Dv-Dv only or Pv-Pv only groups, but titers were boosted to approximately 10(6) in monkeys in the Dv-Pv group. Four weeks after the last immunization, the animals were challenged with 10(4) P. falciparum-parasitized erythrocytes. Peak levels of parasitemia were lower in the 16 monkeys that received Region Ii-containing plasmids or proteins than in the 16 controls (geometric mean: 194,178 and 410,110 parasites/microL, respectively; P=.013, Student's t test). Three of 4 monkeys in the Dv-Pv group did not require treatment. These data demonstrate that immunization with EBA-175 Region Ii induces a significant antiparasite effect in vivo.
Victor Nussenzweig - One of the best experts on this subject based on the ideXlab platform.
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structural and functional properties of Region Ii plus of the malaria circumsporozoite protein
Journal of Experimental Medicine, 1994Co-Authors: Photini Sinnis, Carla Cerami, Pedro Clavijo, David Fenyo, Brian T Chait, Victor NussenzweigAbstract:Stlmmary During feeding, infected mosquitos inject malaria sporozoites into the host circulation. Within minutes, the parasites are found in the liver where they initiate the first stage of malaria infection. All species of malaria sporozoites are uniformly covered by the circumsporozoite protein (CS), which contains a conserved COOH-terminal sequence called Region Ii-plus. We have previously shown that Region Ii-plus is the parasite's hepatocyte-binding ligand and that this ligand binds to heparan sulfate proteoglycans (HSPGs) on the hepatocyte membrane. Using a series of substituted Region Ii-plus peptides, we show here that the downstream basic amino acids as well as the interdispersed hydrophobic residues are required for binding of CS to hepatocyte HSPGs. We also show that this positively charged stretch of amino acids must be aggregated in order to bind to the receptor. On the basis of this information, we have synthesized a multiple antigen peptide that mimics the hepatocyte-binding ligand. This construct inhibits both CS binding to HepG2 cells in vitro as well as CS clearance in mice.
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malaria circumsporozoite protein binds to heparan sulfate proteoglycans associated with the surface membrane of hepatocytes
Journal of Experimental Medicine, 1993Co-Authors: Ute Frevert, Photini Sinnis, Bela Takacs, Carla Cerami, Wayne G. Shreffler, Victor NussenzweigAbstract:During feeding by infected mosquitoes, malaria sporozoites are injected into the host's bloodstream and enter hepatocytes within minutes. The remarkable target cell specificity of this parasite may be explained by the presence of receptors for the Region Ii-plus of the circumsporozoite protein (CS) on the basolateral domain of the plasma membrane of hepatocytes. We have now identified these receptors as heparan sulfate proteoglycans (HSPG). The binding of CS to the receptors is abolished by heparitinase treatment, indicating that the recognition of Region Ii-plus is via the glycosaminoglycan chains. We have purified and partially characterized the CS-binding HSPGs from HepG2 cells. They have a molecular weight of 400,000-700,000, are tightly associated with the plasma membrane, and are released from the cell surface by very mild trypsinization, a property which the CS receptors share with the syndecan family of proteoglycans.
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the basolateral domain of the hepatocyte plasma membrane bears receptors for the circumsporozoite protein of plasmodium falciparum sporozoites
Cell, 1992Co-Authors: Carla Cerami, Photini Sinnis, Bela Takacs, Ute Frevert, Pedro Clavijo, Manuel J Santos, Victor NussenzweigAbstract:Abstract Minutes after injection into the circulation, malaria sporozoites enter hepatocytes. The speed and specificity of the invasion process suggest that it is receptor mediated. We show here that recombinant Plasmodium falciparum circumsporozoite protein (CS) binds specifically to Regions of the plasma membrane of hepatocytes exposed to circulating blood in the Disse space. No binding has been detected in other organs, or even in other Regions of the hepatocyte membrane. The interaction of CS with hepatocytes, as well as sporozoite invasion of HepG2 cells, is inhibited by synthetic peptides representing the evolutionarily conserved Region Ii of CS. We conclude that Region Ii is a sporozoite ligand for hepatocyte receptors localized to the basolateral domain of the plasma membrane. Our findings provide a rational explanation for the target cell specificity of malaria sporozoites.
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binding of malarial circumsporozoite protein to sulfatides gal 3 so4 β1 cer and cholesterol 3 sulfate and its dependence on disulfide bond formation between cysteines in Region Ii
Molecular and Biochemical Parasitology, 1992Co-Authors: Carla Cerami, Frank Kwakyeberko, Victor NussenzweigAbstract:Region Ii of the malaria circumsporozoite (CS) protein is highly conserved between the CS proteins of different species of malaria. Amino acid sequences homologous to that of Region Ii are found in thrombospondin, properdin, von Willebrand factor and a few other proteins. We show here that the native CS protein from the rodent parasite Plasmodium berghei, and recombinant Plasmodium vivax and Plasmodium falciparum CS proteins containing Region Ii, but not recombinant proteins lacking Region Ii, specifically bind to sulfatides and cholesterol-3-sulfate. The binding is abolished following reduction and alkylation of the proteins. Region Ii contains 2 cysteines separated by only 3 amino acids, S(N), V, T, and these are the only cysteines present in our recombinant proteins. Therefore, our findings strongly suggest that the Region Ii cysteines are linked by a disulfide bond forming a small peptide loop. We also present evidence that the recognition of sulfatides, cholesterol-3-sulfate, or other cross-reactive sulfated macromolecules by Region Ii may be required during sporozoite invasion of liver cells. Antibodies to a peptide representing Region Ii react with live sporozoites and with sporozoites fixed with glutaraldehyde, indicating that this Region is exposed on the surface of the parasites. Furthermore, we have found that the sulfatide and cholesterol-3-sulfate recognition by the CS proteins, and the invasion of hepatocytes by P. berghei sporozoites, are specifically inhibited by dextran sulfate.
David J Haynes - One of the best experts on this subject based on the ideXlab platform.
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Delineation of Stage Specific Expression of Plasmodium falciparum EBA-175 by Biologically Functional Region Ii Monoclonal Antibodies
2016Co-Authors: B. Kim, David L Narum, Rana Chattopadhyay, Adriana Ahumada, David J Haynes, Steven R Fuhrmann, Jennifer N Wingard, Hong Liang, Lee Sim, Kathleen J MochAbstract:Background: The malaria parasite Plasmodium falciparum EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding Region (RIi) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains. Methods and Findings: Five mAbs specific for F1 or F2 were generated. Three mAbs specific for F2 potently blocked binding of EBA-175 to erythrocytes, and merozoite invasion of erythrocytes (IC50 10 to 100 mg/ml IgG in growth inhibition assays). A mAb specific for F1 blocked EBA-175 binding and merozoite invasion less effectively. The difference observed between the IC50 of F1 and F2 mAbs was not due to differing association and disassociation rates as determined by surface plasmon resonance. Four of the mAbs recognized conformation-dependent epitopes within F1 or F2. Used in combination, F1 and F2 mAbs blocked the binding of native EBA-175 to erythrocytes and inhibited parasite invasion synergistically in vitro. MAb R217, the most potent, did not recognize sporozoites, 3-day hepatocyte stage parasites, nor rings, trophozoites, gametocytes, retorts, ookinetes, and oocysts but recognized 6-day hepatocyte stage parasites, and schizonts. Even thoug
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delineation of stage specific expression of plasmodium falciparum eba 175 by biologically functional Region Ii monoclonal antibodies
PLOS ONE, 2011Co-Authors: David L Narum, Rana Chattopadhyay, Adriana Ahumada, David J Haynes, Steven R Fuhrmann, Jennifer N Wingard, Hong Liang, Kathleen J MochAbstract:Background The malaria parasite Plasmodium falciparum EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding Region (RIi) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains. Methods and Findings Five mAbs specific for F1 or F2 were generated. Three mAbs specific for F2 potently blocked binding of EBA-175 to erythrocytes, and merozoite invasion of erythrocytes (IC50 10 to 100 µg/ml IgG in growth inhibition assays). A mAb specific for F1 blocked EBA-175 binding and merozoite invasion less effectively. The difference observed between the IC50 of F1 and F2 mAbs was not due to differing association and disassociation rates as determined by surface plasmon resonance. Four of the mAbs recognized conformation-dependent epitopes within F1 or F2. Used in combination, F1 and F2 mAbs blocked the binding of native EBA-175 to erythrocytes and inhibited parasite invasion synergistically in vitro. MAb R217, the most potent, did not recognize sporozoites, 3-day hepatocyte stage parasites, nor rings, trophozoites, gametocytes, retorts, ookinetes, and oocysts but recognized 6-day hepatocyte stage parasites, and schizonts. Even though efficient at blocking binding to erythrocytes and inhibiting invasion into erythrocytes, MAb R217 did not inhibit sporozoite invasion and development in hepatocytes in vitro. Conclusions The role of the F1 and F2 domains in erythrocyte invasion and binding was elucidated with mAbs. These mAbs interfere with native EBA-175 binding to erythrocyte in a synergistic fashion. The stage specific expression of EBA-175 showed that the primary focus of activity was the merozoite stage. A recombinant RIi protein vaccine consisting of both F1 and F2 domains that could induce synergistic activity should be optimal for induction of antibody responses that interfere with merozoite invasion of erythrocytes.
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protection of aotus monkeys by plasmodium falciparum eba 175 Region Ii dna prime protein boost immunization regimen
The Journal of Infectious Diseases, 2001Co-Authors: Trevor R Jones, David L Narum, David J Haynes, Steven R Fuhrmann, Kathleen J Moch, Hong Liang, Alfonso S Gozalo, Joao C AguiarAbstract:: Aotus monkeys received 4 doses of Plasmodium falciparum EBA-175 Region Ii vaccine as plasmid DNA (Dv-Dv) or recombinant protein in adjuvant (Pv-Pv) or as 3 doses of DNA and 1 dose of protein (Dv-Pv). After 3 doses, antibody titers were approximately 10(4) in DNA-immunized monkeys and 10(6) in protein-immunized monkeys. A fourth dose did not significantly boost antibody responses in the Dv-Dv only or Pv-Pv only groups, but titers were boosted to approximately 10(6) in monkeys in the Dv-Pv group. Four weeks after the last immunization, the animals were challenged with 10(4) P. falciparum-parasitized erythrocytes. Peak levels of parasitemia were lower in the 16 monkeys that received Region Ii-containing plasmids or proteins than in the 16 controls (geometric mean: 194,178 and 410,110 parasites/microL, respectively; P=.013, Student's t test). Three of 4 monkeys in the Dv-Pv group did not require treatment. These data demonstrate that immunization with EBA-175 Region Ii induces a significant antiparasite effect in vivo.
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antibodies against the plasmodium falciparum receptor binding domain of eba 175 block invasion pathways that do not involve sialic acids
Infection and Immunity, 2000Co-Authors: David L Narum, David J Haynes, Steven R Fuhrmann, Hong Liang, Kathy Moch, Stephen L Hoffman, Kim Lee B SimAbstract:The 175-kDa Plasmodium falciparum erythrocyte binding protein (EBA-175) binds to its receptor, sialic acids on glycophorin A. The binding Region within EBA-175 is a cysteine-rich Region identified as Region Ii. Antibodies against Region Ii block the binding of native EBA-175 to erythrocytes. We identified a P. falciparum strain, FVO, that could not invade erythrocytes devoid of sialic acids due to prior neuraminidase treatment, and in addition, we used a strain, 3D7, that could invade such sialic acid-depleted erythrocytes. We used these two strains to study the capacity of anti-Region Ii antibodies to inhibit FVO and 3D7 parasite development in vitro. Analysis of growth-inhibitory effects of purified FVO anti-Region Ii immunoglobulin G (IgG) with the FVO and 3D7 strains resulted in similar levels of growth inhibition. FVO and 3D7 strains were inhibited between 28 and 56% compared to control IgG. There appeared to be no intracellular growth retardation or killing of either isolate, suggesting that invasion was indeed inhibited. Incubation of recombinant Region Ii with anti-Region Ii IgG reversed the growth inhibition. These results suggest that antibodies against Region Ii can also interfere with merozoite invasion pathways that do not involve sialic acids. The fact that EBA-175 has such a universal and yet susceptible role in erythrocyte invasion clearly supports its inclusion in a multivalent malaria vaccine.
David L Narum - One of the best experts on this subject based on the ideXlab platform.
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Delineation of Stage Specific Expression of Plasmodium falciparum EBA-175 by Biologically Functional Region Ii Monoclonal Antibodies
2016Co-Authors: B. Kim, David L Narum, Rana Chattopadhyay, Adriana Ahumada, David J Haynes, Steven R Fuhrmann, Jennifer N Wingard, Hong Liang, Lee Sim, Kathleen J MochAbstract:Background: The malaria parasite Plasmodium falciparum EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding Region (RIi) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains. Methods and Findings: Five mAbs specific for F1 or F2 were generated. Three mAbs specific for F2 potently blocked binding of EBA-175 to erythrocytes, and merozoite invasion of erythrocytes (IC50 10 to 100 mg/ml IgG in growth inhibition assays). A mAb specific for F1 blocked EBA-175 binding and merozoite invasion less effectively. The difference observed between the IC50 of F1 and F2 mAbs was not due to differing association and disassociation rates as determined by surface plasmon resonance. Four of the mAbs recognized conformation-dependent epitopes within F1 or F2. Used in combination, F1 and F2 mAbs blocked the binding of native EBA-175 to erythrocytes and inhibited parasite invasion synergistically in vitro. MAb R217, the most potent, did not recognize sporozoites, 3-day hepatocyte stage parasites, nor rings, trophozoites, gametocytes, retorts, ookinetes, and oocysts but recognized 6-day hepatocyte stage parasites, and schizonts. Even thoug
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delineation of stage specific expression of plasmodium falciparum eba 175 by biologically functional Region Ii monoclonal antibodies
PLOS ONE, 2011Co-Authors: David L Narum, Rana Chattopadhyay, Adriana Ahumada, David J Haynes, Steven R Fuhrmann, Jennifer N Wingard, Hong Liang, Kathleen J MochAbstract:Background The malaria parasite Plasmodium falciparum EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding Region (RIi) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains. Methods and Findings Five mAbs specific for F1 or F2 were generated. Three mAbs specific for F2 potently blocked binding of EBA-175 to erythrocytes, and merozoite invasion of erythrocytes (IC50 10 to 100 µg/ml IgG in growth inhibition assays). A mAb specific for F1 blocked EBA-175 binding and merozoite invasion less effectively. The difference observed between the IC50 of F1 and F2 mAbs was not due to differing association and disassociation rates as determined by surface plasmon resonance. Four of the mAbs recognized conformation-dependent epitopes within F1 or F2. Used in combination, F1 and F2 mAbs blocked the binding of native EBA-175 to erythrocytes and inhibited parasite invasion synergistically in vitro. MAb R217, the most potent, did not recognize sporozoites, 3-day hepatocyte stage parasites, nor rings, trophozoites, gametocytes, retorts, ookinetes, and oocysts but recognized 6-day hepatocyte stage parasites, and schizonts. Even though efficient at blocking binding to erythrocytes and inhibiting invasion into erythrocytes, MAb R217 did not inhibit sporozoite invasion and development in hepatocytes in vitro. Conclusions The role of the F1 and F2 domains in erythrocyte invasion and binding was elucidated with mAbs. These mAbs interfere with native EBA-175 binding to erythrocyte in a synergistic fashion. The stage specific expression of EBA-175 showed that the primary focus of activity was the merozoite stage. A recombinant RIi protein vaccine consisting of both F1 and F2 domains that could induce synergistic activity should be optimal for induction of antibody responses that interfere with merozoite invasion of erythrocytes.
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protection of aotus monkeys by plasmodium falciparum eba 175 Region Ii dna prime protein boost immunization regimen
The Journal of Infectious Diseases, 2001Co-Authors: Trevor R Jones, David L Narum, David J Haynes, Steven R Fuhrmann, Kathleen J Moch, Hong Liang, Alfonso S Gozalo, Joao C AguiarAbstract:: Aotus monkeys received 4 doses of Plasmodium falciparum EBA-175 Region Ii vaccine as plasmid DNA (Dv-Dv) or recombinant protein in adjuvant (Pv-Pv) or as 3 doses of DNA and 1 dose of protein (Dv-Pv). After 3 doses, antibody titers were approximately 10(4) in DNA-immunized monkeys and 10(6) in protein-immunized monkeys. A fourth dose did not significantly boost antibody responses in the Dv-Dv only or Pv-Pv only groups, but titers were boosted to approximately 10(6) in monkeys in the Dv-Pv group. Four weeks after the last immunization, the animals were challenged with 10(4) P. falciparum-parasitized erythrocytes. Peak levels of parasitemia were lower in the 16 monkeys that received Region Ii-containing plasmids or proteins than in the 16 controls (geometric mean: 194,178 and 410,110 parasites/microL, respectively; P=.013, Student's t test). Three of 4 monkeys in the Dv-Pv group did not require treatment. These data demonstrate that immunization with EBA-175 Region Ii induces a significant antiparasite effect in vivo.
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antibodies against the plasmodium falciparum receptor binding domain of eba 175 block invasion pathways that do not involve sialic acids
Infection and Immunity, 2000Co-Authors: David L Narum, David J Haynes, Steven R Fuhrmann, Hong Liang, Kathy Moch, Stephen L Hoffman, Kim Lee B SimAbstract:The 175-kDa Plasmodium falciparum erythrocyte binding protein (EBA-175) binds to its receptor, sialic acids on glycophorin A. The binding Region within EBA-175 is a cysteine-rich Region identified as Region Ii. Antibodies against Region Ii block the binding of native EBA-175 to erythrocytes. We identified a P. falciparum strain, FVO, that could not invade erythrocytes devoid of sialic acids due to prior neuraminidase treatment, and in addition, we used a strain, 3D7, that could invade such sialic acid-depleted erythrocytes. We used these two strains to study the capacity of anti-Region Ii antibodies to inhibit FVO and 3D7 parasite development in vitro. Analysis of growth-inhibitory effects of purified FVO anti-Region Ii immunoglobulin G (IgG) with the FVO and 3D7 strains resulted in similar levels of growth inhibition. FVO and 3D7 strains were inhibited between 28 and 56% compared to control IgG. There appeared to be no intracellular growth retardation or killing of either isolate, suggesting that invasion was indeed inhibited. Incubation of recombinant Region Ii with anti-Region Ii IgG reversed the growth inhibition. These results suggest that antibodies against Region Ii can also interfere with merozoite invasion pathways that do not involve sialic acids. The fact that EBA-175 has such a universal and yet susceptible role in erythrocyte invasion clearly supports its inclusion in a multivalent malaria vaccine.
