Minimal epitopes expressed in a recombinant polyepitope protein are processed and presented to CD8+ cytotoxic T cells: implications for vaccine design.

Abstract

The epitopes recognized by CD8+ cytotoxic T lymphocytes (CTL) are generated from cytosolic proteins by proteolytic processing. CD8+ a3 cytotoxic T lymphocytes (CTL) recognize short peptides (epitopes) associated with specific alleles of the class I major histocompatibility complex (1). The peptide epitopes are mainly generated from cytosolic proteins by proteolysis, a process believed to involve the multicatalytic proteosome complex (2-8). The influence of sequences flanking CTL epitopes on the proteolytic processing and presentation of these epitopes remains controversial (9-14). Moving CTL epitopes into new positions within a protein in some cases prevents (9) and in other cases has no effect on (10, 11) presentation of the epitope. A profound effect on presentation was observed when an epitope was expressed with different truncations of the natural flanking sequences (12). However, only one of a series of substitutions made to the amino acid residues flanking a CTL epitope was shown to effect presentation (13,14). The subdominance of a CTL epitope has been attributed to the inability of proteosomes to generate the peptide from the parent protein (15), although recently the subdominance of this epitope has been attributed to low affinity of the peptide for its restriction element (16). Although some of these data may illustrate that certain flanking sequences prevent proteolytic generation of an epitope, it is not clear whether the presence of any specific natural flanking sequences is needed to direct the activity of proteolytic processing enzymes.To determine whether any natural sequences outside CTL epitopes are a requirement for class I processing, a recombinant vaccinia virus (VV) was constructed that coded for a single artificial polyepitope protein containing nine class I-restricted CD8+ CTL epitopes in sequence (see Fig.

Human lymphoblast and erythrocyte multicatalytic proteases: differential peptidase activities and responses to the 11S regulator

“…It can be argued that MCA-peptides are artificial substrates and therefore have no bearing on the intracellular production of peptides for immune presentation. The same arguments can be used to evaluate other studies where longer, non-fluorogenic peptides have been employed [32][33][34]. The nature of endogenous precursors to presented peptides remains unclear (e.g.…”

A γ-herpesvirus sneaks through a CD8+T cell response primed to a lytic-phase epitope

“…The problem of EBV reactivation in pediatric bone marrow transplant patients can be controlled by transferring a mixture of in vitro-expanded virus-specific CD4 ϩ and CD8 ϩ T cell lines (14), but this expensive and technically demanding procedure will always be of limited application. Efforts are also being made to develop a peptide-based vaccine for EBV, the idea being that a primed CD8 ϩ T cell response will help to limit the initial phase of the infectious process and allow the rapid emergence of immune CD4 ϩ T cells and antibody (15,16). Even if such a vaccine does not provide sterilizing immunity, it might serve to boost CD8 ϩ T cell memory before transplant (5,15,16) and to prevent the debilitating infectious mononucleosis (IM) syndrome (17,18) seen characteristically when EBV is first encountered during adolescence.…”

“…Efforts are also being made to develop a peptide-based vaccine for EBV, the idea being that a primed CD8 ϩ T cell response will help to limit the initial phase of the infectious process and allow the rapid emergence of immune CD4 ϩ T cells and antibody (15,16). Even if such a vaccine does not provide sterilizing immunity, it might serve to boost CD8 ϩ T cell memory before transplant (5,15,16) and to prevent the debilitating infectious mononucleosis (IM) syndrome (17,18) seen characteristically when EBV is first encountered during adolescence. This immunization strategy is tested here with the ␥HV-68 model (19,20).…”

Influence of flanking sequences on presentation efficiency of a CD8+ cytotoxic T-cell epitope delivered by parvovirus-like particles

“…In various systems, either replicative such as vaccinia or non-replicative such as VLPs produced in yeast (Ty VLPs) (Gilbert et al, 1997) or bacterial toxins reaching the cytosol of APCs (Fayolle et al, 2001), the use of polyepitope chains containing multiple CD8 + T-cell epitopes has been reported for vaccine design (Thomson et al, 1995;Woodberry et al, 1999). In these studies, no influence of the flanking sequences was observed, since the epitopes were linked together and all seemed to be correctly processed.…”

“…Although it was initially established that some flanking sequences could prevent the proteolytic generation of the epitope (Del Val et al, 1991), it is not clear whether the presence of natural flanking sequences is necessary for the correct cleavage of the epitope. In fact, several studies have demonstrated the efficient presentation of CTL epitopes regardless of their context (Gilbert et al, 1997;Thomson et al, 1995).…”