Sequence 104–117 of myelin proteolipid protein is a cryptic encephalitogenic T cell determinant for SJL/J mice

Immunization of animals with myelin proteolipid protein (PLP) causes experimental autoimmune encephalomyelitis (EAE), a disease model that shares many features with human multiple sclerosis (MS). The SJL/J (H-2⁵) mouse is widely used in EAE studies because of its high disease susceptibility. Previous studies have shown that sequences 139–151 HCLGKWLGHPDKF and 178–191 NTWTTCQSIAFPSK represent distinct co-immunodominant encephalitogenic determinants of PLP for SJL/J mice. In the present study, we identify a third distinct PLP encephalitogenic peptide for SJL/J mice. Following immunization with PLP 104–117 KTTICGKGLSATVT, 10/14 SJL/J mice developed clinical and histological EAE with a mean time of onset of 38 days (18–65 days). T cell lines generated from SJL/J mice immunized with p104–117 were predominantly (> 90%) CD3⁺, CD4⁺, αβTCR⁺, CD8^dim, γδTCR^dim T cells and responded in an Ag-specific, I-As-restricted manner to p104–117. Upon adoptive transfer of 16−40 × 10⁶ T line cells, EAE was produced in naive SJL/J recipients 20–34 days after transfer. The delayed onset of both active and passive disease may be related to the non-immunodominant, cryptic nature of p104–117 in SJL/J mice. Lymph node cells from SJL/J mice immunized with either whole PLP or with pooled encephalitogenic PLP peptides responded to challenge with the immunodominant PLP determinants p139–151 and p178–191 but did not respond to p104–117. The existence of three distinct PLP encephalitogenic T cell determinants for SJL/J mice suggests that susceptibility to EAE and perhaps MS may be related to promiscuous T cell recognition of multiple myelin protein determinants.     

Identification of cytotoxic T-lymphocyte epitope(s) and its agonist epitope(s) of a novel target for vaccine therapy (PAGE4)

PAGE4 is an X chromosome-linked cancer testis antigen and is a potential new tumor-associated antigen that is overexpressed in prostate and uterine cancers. The purpose of this study was to identify a human CTL epitope and a corresponding agonist epitope of PAGE4 to determine if PAGE4 is a potential target for vaccine-mediated immunotherapy against PAGE4-expressing tumors. A class I PAGE4 epitope was identified with a high level of binding to HLA-A2. PAGE4 peptide-pulsed dendritic cells were then used to generate human PAGE4-specific T-cell lines. Further studies demonstrated the generation of an enhancer agonist epitope. Compared with the native peptide, the agonist (i) bound to HLA-A2 molecules at lower peptide concentrations, (ii) demonstrated a higher stability of the peptide HLA-A2 complex, (iii) induced higher levels of production of IFN-gamma, Granzyme B, TNF-alpha, IL-2 and lymphotactin by PAGE4-specific T-cell lines and (iv) T-cell lines generated against the agonist peptide were more efficient to lyse HLA-A2 human tumor cells expressing native PAGE4. The studies reported here are the first to describe a PAGE4 CTL epitope and its agonist epitope, and thus identify PAGE4 as a potentially useful target for vaccine-mediated therapy of prostate cancer.     

Mapping and ranking of potential cytotoxic T epitopes in the p53 protein: effect of mutations and polymorphism on peptide binding to purified and refolded HLA molecules

In many cancer cells, the p53 gene displays point mutations that result in stabilization and accumulation of the p53 protein. Therefore, p53 peptides could be presented to the immune system by tumor cells; thus, p53 might be a suitable target antigen for developing an immunotherapy against tumors using cytotoxic T lymphocytes (CTL). To map candidate CTL epitopes, we synthesized 150 peptides of 8–11 residues that contained putative anchor motifs required for binding to common HLA class I molecules. They were tested for their capacity to promote the assembly of purified and refolded HLA-A1, A2, B7 and B8 molecules. The following wild-type p53 peptides were found to be reactive with the HLA molecules tested: 196–205 and 226–234 bound moderately to HLA-A1; 25–35, 65–73, 129–137, 187–197, 263–272 and 264–272 bound strongly, and 187–195 and 256–264 moderately to HLA-A2; 26–35, 63–73, 189–197, 249–257 and 321–330 bound strongly to HLA-B7; and 135–143, 210–218 and 375–383 bound weakly to HLA-B8. We also analyzed the effects of p53 mutations occurring naturally in tumors on peptide/HLA assembly. We found substitutions that enhanced, diminished or had no effect on the peptide binding to HLA molecules. Polymorphism at position 72 mainly affected peptide/HLA-B7 binding, the proline allele P72 giving a less-reactive peptide (63–73) than the arginine allele R72. We have ranked potential p53 epitopes according to their reactivity for purified HLA molecules, allowing the selection of appropriate peptides and HLA molecules to attempt CTL induction in vitro.