Induction of single and dual cytotoxic T‐lymphocyte responses to viral proteins in mice using recombinant hybrid Ty–virus‐like particles

Abstract

SUMMARYThe induction of cytotoxic T-lymphocyte (CTL) responses to viral proteins is thought to be an essential component of protective immunity against viral infections. Methods for generating such responses in a reproducible manner would be of great value in vaccine development. We demonstrate here that the recombinant antigen-presentation system based on the yeast transposon (Ty) particle-forming p1 protein is a potent means of inducing CTL responses to a variety of viral CTL epitopes, including influenza virus nucleoprotein (two epitopes), Sendai virus and vesicular stomatitis virus nucleoproteins, and the V3 loop of human immunodeficiency virus type-1 (HIV-1) gp120. CTL were primed by hybrid Ty-virus-like particles (VLP) carrying the minimal epitope or as much as 19 000 MW of protein. Ty-VLP carrying two different epitopes (dual-epitope Ty-VLP) were capable of priming CTL responses in two different strains of mice or against two epitopes in the same individual. Furthermore, coadministration of a mixture of two different Ty-VLP carrying single epitopes could induce responses to both epitopes in the same individual. Ty-VLP appear to represent a reproducible and flexible system for inducing CTL responses in mice, and warrant further evaluation in primates.

The p1 Protein of the Yeast Transposon Ty1 Can Be Used for the Construction of Bi-Functional Virus-Like Particles

“…This property of p1 is used in biotechnology for the construction of hybrid VLP. There are examples of effective expression of both small peptides [Layton et al, 1996] and large proteins up to 72 kD in hybrid VLPs [Pöggeler et al, 1996]. These recombinant particles have been shown to be immunogenic, eliciting antibodies, T-helper and CTL responses against the inserted antigens.…”

Characterization and Diagnostic Potential of Foreign Epitope-Presenting Ty1 Virus-Like Particles Expressed in <i>Escherichia coli</i> and <i>Pichia pastoris</i>

“…A remarkable feature of the p1 and p1-381 proteins is their capacity to accommodate additional material ranging from small-peptide-sized fragments [Layton et al, 1996] to protein domains of 10-20 kDa and large proteins of up to 72 kDa [Adams et al, 1994a;Burns et al, 1994;Garcia-Valcarcel et al, 1997;Gilbert et al, 1997;Pöggeler et al, 1996]. This reflects the unusually flexible p1 assembly process, which is particularly tolerant of C-terminal fusions.…”

“…Various cytotoxic T-lymphocyte (CTL) epitopes from e.g. influenza virus have also been expressed on Ty VLPs [Layton et al, 1996]. These successes have led to the evaluation of Ty VLPs as an antigen delivery system for vaccines [Adams et al, 1994a;Burns et al, 1994;Kingsman et al, 1995].…”

“…It is likely that the presentation of C-terminal peptides depends on the peptide's size and chemical nature, which differs in these two investigations. Likewise, a C-terminal fusion of the HIV 'envelope region V3' could not be found on Ty particles and consequently no humoral immune response was induced (unpublished data cited in Brookman et al [1995b]), whereas the C-terminal p1-381 fusion of a nonapeptide epitope of the Plasmodium berghei circumsporozoite protein as well as a 20-amino-acid HIV V3 tandem epitope (including a dipeptide linker) successfully generated a CTL response [Gilbert et al, 1997;Layton et al, 1996]. However, surface presentation of an epitope is unnecessary to trigger a CTL response since the VLPs are taken up through antigen-presenting cells and the epitope is presented on MHC class I molecules.…”

“…The fact that VLPs are not infectious is highly important, not only for their use as synthetic standards but also for future use as synthetic antigens for vaccination. Many reports describe the immunogenicity of recombinant Ty-VLPs presenting various epitopes and proteins such as HIV p17/p24, the V3 loop of HIV gp120, and malaria parasite T-cell epitopes [Gilbert et al, 1997;Layton et al, 1996;OliveiraFerreira et al, 2000;Weber et al, 1995]. Furthermore, these noninfectious VLPs successfully passed the required safety and toxicity tests [Weber et al, 1995].…”