Phage display of peptide epitopes from HIV-1 elicits strong cytolytic responses

Abstract

Although much effort has been expended on evaluating recombinant proteins and synthetic peptides as immunogens, they have generally proved incapable of inducing an efficient cytotoxic T-cell (CTL) response. Filamentous bacteriophage fd can display multiple copies of foreign peptides in the N-terminal region of its major coat protein pVIII, 2,700 copies of which make up the virus capsid. Here we show that fd virions displaying peptide RT2 (ILKEPVHGV), corresponding to residues 309-317 of the reverse transcriptase (RTase) of HIV-1, are able to prime a CTL response specific for this HIV-1 epitope in human cell lines. Successful priming also requires a T-helper epitope, pep23 (KDSWTVNDIQKLVGK), corresponding to residues 249-263 of HIV-1 RTase. Supplying this by displaying it on either the same or a separate bacteriophage virion led to activation of antigen-specific CD4+ T cells. Likewise, HLA-A2 transgenic mice immunized with bacteriophage virions displaying peptide RT2 were shown to mount an effective, specific anti-HIV-RT2 CTL response. This unexpected ability to elicit a designated cytolytic T-cell response, in addition to a B-cell response, has important implications for access to the class I major histocompatibility complex (MHC) loading compartment and the development of recombinant vaccines.

Cross-presentation of phage particle antigen in MHC class II and endoplasmic reticulum marker-positive compartments

“…It has been shown that filamentous phage particles can prime MHC class I-restricted cytotoxic T lymphocyte (CTL) responses in vivo [16][17][18]. Using MHC class I-peptide complex-specific antibodies, our data directly indicate that MHC class Ipeptide complexes are generated in MHC class IIpositive endocytic compartments.…”

“…Filamentous phage particle is a recently proposed alternative antigen delivery strategy for eliciting specific CTL responses in vivo [16][17][18]. It is an asymmetric particle about 6 nm in diameter and 800-2,000 nm long, comprising a sheath of about 2,700 copies of the major coat protein gpVIII [22].…”

Vaccination with filamentous bacteriophages targeting DEC‐205 induces DC maturation and potent anti‐tumor T‐cell responses in the absence of adjuvants

“…fdOVA, fdOVA/sc-control and fdOVA/sc-aDEC bacteriophage fd vectors were constructed by ligating a SacII-StyI oligonucleotide insert encoding the OVA 257-264 peptide SIINFEKL into SacIIStyI-digested fdAMPLAY388, fdsc-control or fdsc-aDEC phage genome as previously described [2].…”

“…In this context we previously demonstrated that fd phage particles have access to both MHC class I and class II compartments [1] and that the antigenic determinants displayed by fd virions on the major pVIII coat protein trigger specific CTL responses [2,3]. However, the full potential of the fd bacteriophage system for vaccine formulation is still ameliorable by exploiting simultaneous display on different phage coat proteins.…”

Mimotope vaccines

“…Some of these issues may be resolved by synthesising many copies of the oligopeptide as multiple antigenic peptides (MAPs). Alternatively, recently developed molecular biology tools have allowed the MAPs principle to be extended by genetically fusing and expressing c. 270 peptide mimotopes to the coliphage major coat protein pVIII on the surface of the ®lamentous coliphage fd [22].…”