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Identification of an Immunogenic Mimic of a Conserved Epitope on the Plasmodium falciparum Blood Stage Antigen AMA1 Using Virus-Like Particle (VLP) Peptide Display.

Crossey E, Frietze K, Narum DL, Peabody DS, Chackerian B - PLoS ONE (2015)

Bottom Line: Most of the selected VLPs failed to reliably elicit AMA1 specific antibodies.However, one VLP consistently induced antibodies that cross-reacted with AMA1.Taken together, these data demonstrate that VLP-peptide display can identify immunogenic mimics of a complex conformational epitope and illustrate the promise and challenges of this approach.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM 87131, United States of America.

ABSTRACT
We have developed a peptide display platform based on VLPs of the RNA bacteriophage MS2 that combines the high immunogenicity of VLP display with affinity selection capabilities. Random peptides can be displayed on the VLP surface by genetically inserting sequences into a surface-exposed loop of the viral coat protein. VLP-displayed peptides can then be isolated by selection using antibodies, and the VLP selectants can then be used directly as immunogens. Here, we investigated the ability of this platform to identify mimotopes of a highly conserved conformational epitope present on the Plasmodium falciparum blood-stage protein AMA1. Using 4G2, a monoclonal antibody that binds to this epitope and is a potent inhibitor of erythrocyte invasion, we screened three different VLP-peptide libraries and identified specific VLPs that bound strongly to the selecting mAb. We then tested the ability of a handful of selected VLPs to elicit anti-AMA1 antibody responses in mice. Most of the selected VLPs failed to reliably elicit AMA1 specific antibodies. However, one VLP consistently induced antibodies that cross-reacted with AMA1. Surprisingly, this VLP bound to 4G2 more weakly than the other selectants we identified. Taken together, these data demonstrate that VLP-peptide display can identify immunogenic mimics of a complex conformational epitope and illustrate the promise and challenges of this approach.

No MeSH data available.


Related in: MedlinePlus

Peptide families identified after 4G2 selection of a mixed VLP library.After 3 rounds of selection VLPs were deep sequenced. The top 1,450 unique peptide selectants were sorted into families using the online Immune Epitope Database analysis resource [32]. This analysis identified 10 peptide families with at least 10 members. This chart shows the consensus sequences and relative frequencies of each of these families.
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pone.0132560.g004: Peptide families identified after 4G2 selection of a mixed VLP library.After 3 rounds of selection VLPs were deep sequenced. The top 1,450 unique peptide selectants were sorted into families using the online Immune Epitope Database analysis resource [32]. This analysis identified 10 peptide families with at least 10 members. This chart shows the consensus sequences and relative frequencies of each of these families.

Mentions: To address our second concern, that 4G2 mimotopes may be better identified from a more length-diverse library of recombinant VLPs, we performed 3 rounds of affinity selection with a mixed library of VLPs displaying 6-10mer peptides. We performed one round of selection at high valency, and two rounds at low-valency. The enrichment of 4G2 binding in selectant populations is shown in Fig 3. By round 2 the VLP selectant population bound to 4G2 above background levels, and binding activity was enriched after a third round of selection. Deep sequencing of the round 3 selectant population identified ~1,450 unique selectant sequences (summarized in S3 and S4 Tables), and using the Immune Epitope Database analysis resource [32] we identified nine sequence families of more than 10 members each; Fig 4).


Identification of an Immunogenic Mimic of a Conserved Epitope on the Plasmodium falciparum Blood Stage Antigen AMA1 Using Virus-Like Particle (VLP) Peptide Display.

Crossey E, Frietze K, Narum DL, Peabody DS, Chackerian B - PLoS ONE (2015)

Peptide families identified after 4G2 selection of a mixed VLP library.After 3 rounds of selection VLPs were deep sequenced. The top 1,450 unique peptide selectants were sorted into families using the online Immune Epitope Database analysis resource [32]. This analysis identified 10 peptide families with at least 10 members. This chart shows the consensus sequences and relative frequencies of each of these families.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493041&req=5

pone.0132560.g004: Peptide families identified after 4G2 selection of a mixed VLP library.After 3 rounds of selection VLPs were deep sequenced. The top 1,450 unique peptide selectants were sorted into families using the online Immune Epitope Database analysis resource [32]. This analysis identified 10 peptide families with at least 10 members. This chart shows the consensus sequences and relative frequencies of each of these families.
Mentions: To address our second concern, that 4G2 mimotopes may be better identified from a more length-diverse library of recombinant VLPs, we performed 3 rounds of affinity selection with a mixed library of VLPs displaying 6-10mer peptides. We performed one round of selection at high valency, and two rounds at low-valency. The enrichment of 4G2 binding in selectant populations is shown in Fig 3. By round 2 the VLP selectant population bound to 4G2 above background levels, and binding activity was enriched after a third round of selection. Deep sequencing of the round 3 selectant population identified ~1,450 unique selectant sequences (summarized in S3 and S4 Tables), and using the Immune Epitope Database analysis resource [32] we identified nine sequence families of more than 10 members each; Fig 4).

Bottom Line: Most of the selected VLPs failed to reliably elicit AMA1 specific antibodies.However, one VLP consistently induced antibodies that cross-reacted with AMA1.Taken together, these data demonstrate that VLP-peptide display can identify immunogenic mimics of a complex conformational epitope and illustrate the promise and challenges of this approach.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM 87131, United States of America.

ABSTRACT
We have developed a peptide display platform based on VLPs of the RNA bacteriophage MS2 that combines the high immunogenicity of VLP display with affinity selection capabilities. Random peptides can be displayed on the VLP surface by genetically inserting sequences into a surface-exposed loop of the viral coat protein. VLP-displayed peptides can then be isolated by selection using antibodies, and the VLP selectants can then be used directly as immunogens. Here, we investigated the ability of this platform to identify mimotopes of a highly conserved conformational epitope present on the Plasmodium falciparum blood-stage protein AMA1. Using 4G2, a monoclonal antibody that binds to this epitope and is a potent inhibitor of erythrocyte invasion, we screened three different VLP-peptide libraries and identified specific VLPs that bound strongly to the selecting mAb. We then tested the ability of a handful of selected VLPs to elicit anti-AMA1 antibody responses in mice. Most of the selected VLPs failed to reliably elicit AMA1 specific antibodies. However, one VLP consistently induced antibodies that cross-reacted with AMA1. Surprisingly, this VLP bound to 4G2 more weakly than the other selectants we identified. Taken together, these data demonstrate that VLP-peptide display can identify immunogenic mimics of a complex conformational epitope and illustrate the promise and challenges of this approach.

No MeSH data available.


Related in: MedlinePlus