Portable flanking sequences modulate CTL epitope processing

Abstract

Peptide presentation is critical for immune recognition of pathogen-infected cells by CD8 + T lymphocytes.Although a limited number of immunodominant peptide epitopes are consistently observed in diseases such as HIV-1 infection, the relationship between immunodominance and antigen processing in humans is largely unknown. Here, we have demonstrated that endogenous processing and presentation of a human immunodominant HIV-1 epitope is more efficient than that of a subdominant epitope. Furthermore, we have shown that the regions flanking the immunodominant epitope constitute a portable motif that increases the production and antigenicity of otherwise subdominant epitopes. We used a novel in vitro degradation assay involving cytosolic extracts as well as endogenous intracellular processing assays to examine 2 well-characterized HIV-1 Gag overlapping epitopes presented by the same HLA class I allele, one of which is consistently immunodominant and the other subdominant in infected persons. The kinetics and products of degradation of HIV-1 Gag favored the production of peptides encompassing the immunodominant epitope and destruction of the subdominant one. Notably, cytosolic digestion experiments revealed flanking residues proximal to the immunodominant epitope that increased the production and antigenicity of otherwise subdominant epitopes. Furthermore, specific point mutations in these portable flanking sequences modulated the production and antigenicity of epitopes. Such portable epitope processing determinants provide what we believe is a novel approach to optimizing CTL responses elicited by vaccine vectors.

CTL recognition of HIV‐1‐infected cells via cross‐recognition of multiple overlapping peptides from a single 11‐mer Pol sequence

“…42: 2621Immunol. -2631 processed peptides eluted from HIV-1 Nef-expressing cells [17]; and cells pulsed with proteasomal digests of HIV-1 protein derived fragments [16,17]. However, these studies did not demonstrate the ability of CD8 + T cells to recognize overlapping peptides presented by HLA class I molecules in HIV-1-infected cells.…”

“…HIV-1-specific CD8 + T cells recognize peptides derived from HIV-1 proteins presented by HLA class I molecules on HIV-1-infected cells, and effectively although not completely control the replication of HIV-1 [1,5,11,12]. Although any given HLA class I allele presents 8-mer to 11-mer peptides derived from different parts of HIV-1, it is also known that overlapping HIV-1 epitope Correspondence: Prof. Masafumi Takiguchi e-mail: masafumi@kumamoto-u.ac.jp peptides of different lengths from 8-mer to 11-mer from a given region can be presented by the same HLA class I molecule [13][14][15][16][17][18][19][20][21]. However, the role of the presentation of these overlapping peptides of different lengths in HIV-1-specific CD8 + T-cell recognition remains unclear.…”

“…The ability of CD8 + T cells to recognize overlapping peptides was shown by previous studies using the following target cells: cells pulsed with synthetic peptide [13-17, 19, 20]; cells expressing HIV-1-derived proteins [16,17]; cells pulsed with naturally * These authors contributed equally to the work. Eur.…”

“…HIV-1-specific CD8 + T cells recognize peptides derived from HIV-1 proteins presented by HLA class I molecules on HIV-1-infected cells, and effectively although not completely control the replication of HIV-1 [1, 5,11,12]. Although any given HLA class I allele presents 8-mer to 11-mer peptides derived from different parts of HIV-1, it is also known that overlapping HIV-1 epitope processed peptides eluted from HIV-1 Nef-expressing cells [17]; and cells pulsed with proteasomal digests of HIV-1 protein derived fragments [16,17]. However, these studies did not demonstrate the ability of CD8 + T cells to recognize overlapping peptides presented by HLA class I molecules in HIV-1-infected cells.…”

“…Although any given HLA class I allele presents 8-mer to 11-mer peptides derived from different parts of HIV-1, it is also known that overlapping HIV-1 epitope Correspondence: Prof. Masafumi Takiguchi e-mail: masafumi@kumamoto-u.ac.jp peptides of different lengths from 8-mer to 11-mer from a given region can be presented by the same HLA class I molecule [13][14][15][16][17][18][19][20][21]. However, the role of the presentation of these overlapping peptides of different lengths in HIV-1-specific CD8 + T-cell recognition remains unclear.The ability of CD8 + T cells to recognize overlapping peptides was shown by previous studies using the following target cells: cells pulsed with synthetic peptide [13-17, 19, 20]; cells expressing HIV-1-derived proteins [16,17]; cells pulsed with naturally * These authors contributed equally to the work. Eur.…”