Immunogenic Display of Diverse Peptides on Virus-like Particles of RNA Phage MS2

Abstract

SummaryThe high immunogenicity of peptides displayed in dense repetitive arrays on virus-like particles makes recombinant VLPs promising vaccine carriers. Here we describe a platform for vaccine development based on the VLPs of RNA bacteriophage MS2. It serves for the engineered display of specific peptide sequences, but will also allow the construction of random peptide libraries from which specific binding activities can be recovered by affinity selection. Peptides representing the V3 loop of HIV gp120 and the ECL2 loop of the HIV coreceptor, CCR5, were inserted into a surface loop of MS2 coat protein. Both insertions disrupted coat VLP assembly, apparently by interfering with protein folding, but these defects were efficiently suppressed by genetically fusing coat protein's two identical polypeptides into a single-chain dimer. The resulting VLPs displayed the V3 and ECL2 peptides on their surfaces where they showed the potent immunogenicity that is the hallmark of VLPdisplayed antigens. Experiments with random-sequence peptide libraries show the single-chain dimer to be highly tolerant of 6-, 8-and 10-amino acid insertions. Not only do MS2 VLPs support the display of a wide diversity of peptides in a highly immunogenic format, but they also encapsidate the mRNAs that direct their synthesis, thus establishing the genotype/phenotype linkage necessary for recovery of affinity selected sequences. The single-chain MS2 VLP therefore unites in a single structural platform the selective power of phage display with the high immunogenicity of VLPs.

Induction of HIV-Blocking Anti-CCR5 IgA in Peyers's Patches without Histopathological Alterations

“…Many attempts to elicit anti-CCR5 vaccines have failed, however, possibly because the tested CCR5 domains were not immunogenic enough or because the antigens were not presented in an adequate conformation (14). Indeed, the use of scaffold proteins able to present the CCR5 ECL2 domain in a constrained conformation, as occurred in virus-like particles (VLPs), succeeded in overcoming tolerance and induced the desired response (32). As for ECL2, immunogens presenting the CCR5 ECL1 domain in a linear conformation were previously shown to be unable to elicit immunoglobulins recognizing either the native receptor or the domain itself in a conformed, circular structure (3).…”

RETRACTED ARTICLE: Cell-specific delivery of messenger RNA and microRNA by recombinant MS2 virus-like particles carrying cell-penetrating peptide

“…Insertion of DNA oligonucleotides at this site allows the production of chimeric MS2 coat proteins, which have foreign peptide sequences in the central part of the hairpin (Mastico et al 1993). Most importantly, the displayed peptides are highly immunogenic (Peabody et al 2008), and the MS2 VLPs with inserted peptides are heat-resistant up to about 50°C (Caldeira and Peabody 2011). To date, MS2 VLPs have been used as peptide vaccine carriers for HIV (Peabody et al 2008), human papillomavirus (Tumban et al 2012), influenza virus (Mastico et al 1993), hypersensitivity (Mastico et al 1993), and malaria (Heal et al 1999).…”

The True Story and Advantages of RNA Phage Capsids as Nanotools

“…Following well-known peptide display systems based on filamentous phages, a novel peptide display platform on MS2 VLPs was developed and successfully tested, including the identification of conformational epitopes [159,160]. …”

“…The genetic fusions of two copies of the MS2 [159], PP7 [191], and GA or Qβ [I. Cielens and A. Strods, unpubl. data] CPs resulted in a self-assembly-competent single-chain dimer that not only increased thermodynamic stability but also considerably improved tolerance to foreign insertions in the AB-loop.…”