A tyrosinase peptide presented by HLA-B35 is recognized on a human melanoma by autologous cytotoxic T lymphocytes

Therapeutic Cancer Vaccines—Antigen Discovery and Adjuvant Delivery Platforms

For decades, vaccines have played a significant role in protecting public and personal health against infectious diseases and proved their great potential in battling cancers as well. This review focused on the current progress of therapeutic subunit vaccines for cancer immunotherapy. Antigens and adjuvants are key components of vaccine formulations. We summarized several classes of tumor antigens and bioinformatic approaches of identification of tumor neoantigens. Pattern recognition receptor (PRR)-targeting adjuvants and their targeted delivery platforms have been extensively discussed. In addition, we emphasized the interplay between multiple adjuvants and their combined delivery for cancer immunotherapy.

Both CD4 and CD8 T cells mediate equally effective in vivo tumor treatment when engineered with a highly avid TCR targeting tyrosinase

Tyrosinase, an enzyme involved in melanin synthesis, is expressed in nearly all primary and metastatic melanoma lesions and thus is an attractive target for TCR-based gene therapy using adoptive cell transfer. The TCR alpha- and beta-chain genes from a tumor-infiltrating lymphocyte, which recognized the tyrosinase 368-376 peptide in the context of HLA-A2, were cloned into a gamma-retroviral vector. Following transduction of PBL, specific reactivity was confirmed by cytokine production following coculture with tumor targets. Experiments using Ab blockade and CD4/CD8 sorting of the transduced PBLs demonstrated that this antityrosinase TCR was CD4/CD8 independent. The introduction of a second disulfide bond between the TCR constant regions and/or creation of a chimeric protein in which the human constant regions were replaced by murine homologs resulted in enhanced TCR expression as demonstrated by tetramer staining and improved tumor reactivity that was comparable to PBL transduced with either anti-melanoma Ag recognized by T cells-1 or anti-gp100 TCR vectors currently used in clinical trials. The chimeric TCR also allowed us to test antitumor function of in HLA-A2/K(b)-transgenic mice. Transfer of the antityrosinase TCR into mouse splenocytes conferred CD4/CD8-independent, HLA-A2-restricted Ag reactivity against B16/A2K(b) murine melanoma in vitro. Furthermore, adoptive transfer of transduced splenocytes mediated B16/A2K(b) melanoma tumor regression in lymphodepleted mice, and, surprisingly, both CD8 and CD4 T cells were equally effective in mediating tumor regression. These results suggest that this highly active tyrosinase-specific TCR could be of value in adoptive cell transfer for melanoma.

Assembly and intracellular trafficking of HLA-B*3501 and HLA-B*3503

Residue 116 of major histocompatibility complex (MHC) class I heavy chains is an important determinant of assembly, that can influence rates of ER-Golgi trafficking, binding to the transporter associated with antigen processing (TAP), tapasin dependence of assembly, and the efficiency and specificity of peptide binding. Here, we investigated assembly and peptide-binding differences between HLA-B*3501(S116) and HLA-B*3503(F116), two alleles differing only at position 116 of the MHC class I heavy chain, that are associated respectively with normal or rapid AIDS progression. A reduced intracellular maturation rate was observed for HLA-B*3503 in HIV-infected and uninfected cells, which correlated with enhanced binding of HLA-B*3503 to TAP. No significant differences in the intrinsic efficiency of in vitro peptide binding by HLA-B*3501 and HLA-B*3503 were measurable with several common peptides or peptide libraries, and both allotypes were relatively tapasin-independent for their assembly. However, thermostability differences between the two allotypes were measurable in a CD4(+) T cell line. These findings suggest that compared to HLA-B*3501, a reduced intracellular peptide repertoire for HLA-B*3503 could contribute to its slower intracellular trafficking and stronger association with rapid AIDS progression.

A new tyrosinase epitope recognized in the HLA-B*4002 context by CTL from melanoma patients

Melanoma reactive CTL were obtained by stimulating PBL from a melanoma patient in remission since 1994 following adjuvant TIL immunotherapy, with the autologous melanoma cell line. They were cloned by limiting dilution. One CTL clone recognized melanoma cell lines expressing tyrosinase and the B*4002 molecule, either spontaneously or upon transfection. We demonstrated that this clone recognizes the tyrosinase-derived nonapeptide 316-324 (ADVEFCLSL) and the overlapping decapeptide 315-324 (SADVEFCLSL). We derived two distinct additional specific CTL clones from this same patient that were also reactive against B*4002 melanoma cell lines, suggesting a relative diversity of this specific repertoire in this patient. Stimulating PBMC derived from four additional B*4002 melanoma patients with the tyrosinase 316-324 nonapeptide induced the growth of specific cells for two of the patients, demonstrating the immunogenicity of this new epitope. Our data show that this nonapeptide is a new tool that could be used to generate melanoma-specific T cells for adoptive immunotherapy or serve as a peptide vaccine for HLA-B*4002 melanoma patients.

Pores formation on cell membranes by hederacolchiside A1 leads to a rapid release of proteins for cytosolic subproteome analysis

Hederacolchiside A1 was used to progressively permeabilize the membrane of human melanoma MEL-5 cells. Holes formation was followed by Scanning Electron Microscopy and interaction of the saponin with cholesterol and phospholipids by TOF-SIMS. 2D-LC-MS/MS and 2D-SDS-PAGE show that the release of soluble proteins into serum-free culture media increases with time. This can lead to a new rapid and efficient strategy to analyze the cytosolic subproteome and it opens the door to get information from the cytosolic compartment for clinical proteomic studies.

Direct peptide-regulatable interactions between MHC class I molecules and tapasin

Tapasin (Tpn) has been implicated in multiple steps of the MHC class I assembly pathway, but the mechanisms of function remain incompletely understood. Using purified proteins, we could demonstrate direct binding of Tpn to peptide-deficient forms of MHC class I molecules at physiological temperatures. Tpn also bound to M10.5, a pheromone receptor-associated MHC molecule that has an open and empty groove and that shares significant sequence identity with class I sequences. Two types of MHC class I-Tpn complexes were detectable in vitro depending on the input proteins; those depleted in beta(2)m, and those containing beta(2)m. Both were competent for subsequent assembly with peptides, but the latter complexes assembled more rapidly. Thus, the assembly rate of Tpn-associated class I was determined by the conditions under which Tpn-MHC class I complexes were induced. Peptide loading of class I inhibited Tpn-class I-binding interactions, and peptide-depletion enhanced binding. In combination with beta(2)m, certain peptides induced efficient dissociation of preformed Tpn-class I complexes. Together, these studies demonstrate direct Tpn-MHC class I interactions and preferential binding of empty MHC class I by Tpn, and that the Tpn-class I interaction is regulated by both beta(2)m and peptide. In cells, Tpn is likely to be a direct mediator of peptide-regulated binding and release of MHC class I from the TAP complex.

Evaluation of prime/boost regimens using recombinant poxvirus/tyrosinase vaccines for the treatment of patients with metastatic melanoma

PURPOSE

Two clinical trials were conducted to evaluate the clinical efficacy and immunologic impact of vaccination against the tyrosinase protein plus systemic interleukin 2 (IL-2) administration in patients with advanced metastatic melanoma.

EXPERIMENTAL DESIGN

Full-length tyrosinase was employed as an immunogen to induce diverse immunologic responses against a commonly expressed melanoma antigen. Heterologous prime/boost vaccination with recombinant vaccinia and fowlpox vectors encoding tyrosinase was first explored in a randomized three-arm phase II trial, in which vaccines were administered alone or concurrently with low-dose or high-dose IL-2. In a subsequent single cohort phase II trial, all patients received the same vaccines and high-dose IL-2 sequentially rather than concurrently.

RESULTS

Among a total of 64 patients treated on these trials, 8 objective partial responses (12.5%) were observed, all in patients receiving high-dose IL-2. Additional patients showed evidence of lesional regression (mixed tumor response) or overall regression that did not achieve partial response status (minor response). In vitro evidence of enhanced immunity against tyrosinase following protocol treatments was documented in 3 of 49 (6%) patients tested serologically, 3 of 23 (13%) patients tested for T-cell recognition of individual tyrosinase peptides, and 4 of 16 (25%) patients tested for T-cell recognition of full-length tyrosinase protein with real-time reverse transcription-PCR techniques.

CONCLUSIONS

Whereas prime/boost immunization with recombinant vaccinia and fowlpox viruses enhanced antityrosinase immunity in some patients with metastatic melanoma, it was ineffective alone in mediating clinical benefit, and in combination with IL-2 did not mediate clinical benefit significantly different from that expected from treatment with IL-2 alone.

HLA-B8 association with late-stage melanoma--an immunological lesson?

BACKGROUND

Differences in HLA allele frequencies between the diseased and healthy populations may signify efficient immune responses, a notion that has been successfully tested for infectious diseases or for association with genetic elements involved in a distinct type of immunity. This retrospective study is intended to detect differences in MHC class I carrier frequencies of advanced melanoma patients compared to healthy bone marrow donors.

METHODS

The HLA-A and -B carrier frequencies of 748 stage IV melanoma patients retrieved from serotyping at 6 different centers in Germany were compared using a chi-square test to 13,386 fully HLA typed bone marrow donors registered in the German national bone marrow donor registry.

RESULTS

The comparison of HLA carrier frequencies in advanced cancer patients with healthy bone marrow donors revealed a significant decrease in HLA-B8 carrier frequencies, which was also apparent in patients with advanced disease compared to patients with loco-regional disease.

CONCLUSION

The data suggest that protective immune responses restricted to distinct MHC class I molecules may be operational in a subset of melanoma patients, which is the prerequisite for a large scale screen for the corresponding epitopes. Alternatively, the known association of the ancestral haplotype HLA-A1, -B8 and -DR3 with genetic elements such as distinct TNF-alpha alleles might have a protective effect on disease progression. In any case, identification of the cause of protection within this patient subset might lead to a significant improvement in the efficacy of current immunotherapeutic approaches.

A peptide derived from melanocytic protein gp100 and presented by HLA-B35 is recognized by autologous cytolytic T lymphocytes on melanoma cells

A panel of autologous cytolytic T lymphocyte (CTL) clones have been isolated from blood lymphocytes of a melanoma patient after in vitro stimulation with autologous tumor cells. We previously reported the molecular definition of three distinct antigens recognized by some of these CTL clones. We describe here, the identification of a fourth antigenic peptide expressed by this melanoma line and recognized by a CTL clone restricted by HLA-B*3503. The antigenic peptide, which is nine-amino acid long, has the sequence LPHSSSHWL and is derived from melanocyte differentiation antigen gp100. As HLA-B35 is one of the most frequent HLA-B alleles, being present in 20% of the Caucasian individuals, this peptide may be a good target for peptide-based immunotherapy of melanoma.

An antigenic peptide produced by peptide splicing in the proteasome

CD8 T lymphocytes recognize peptides of 8 to 10 amino acids presented by class I molecules of the major histocompatibility complex. Here, CD8 T lymphocytes were found to recognize a nonameric peptide on melanoma cells that comprises two noncontiguous segments of melanocytic glycoprotein gp100(PMEL17). The production of this peptide involves the excision of four amino acids and splicing of the fragments. This process was reproduced in vitro by incubating a precursor peptide of 13 amino acids with highly purified proteasomes. Splicing appears to occur by transpeptidation involving an acyl-enzyme intermediate. Our results reveal an unanticipated aspect of the proteasome function of producing antigenic peptides.

Identification of five new HLA-B*3501-restricted epitopes derived from common melanoma-associated antigens, spontaneously recognized by tumor-infiltrating lymphocytes

We previously described HLA-B35-restricted melanoma tumor-infiltrating lymphocyte responses to frequently expressed melanoma-associated Ags: tyrosinase, Melan-A/MART-1, gp100, MAGE-A3/MAGE-A6, and NY-ESO-1. Using clones derived from these TIL, we identified in this study the corresponding epitopes. We show that five of these epitopes are new and that melanoma cells naturally present all the six epitopes. Interestingly, five of these epitopes correspond to or encompass melanoma-associated Ag epitopes presented in other HLA contexts, such as A2, A1, B51, and Cw3. In particular, the HLA-B35-restricted Melan-A epitope is mimicked by the peptide 26-35, already known as the most immunodominant melanoma epitope in the HLA-A*0201 context. Because this peptide lacked adequate anchor amino acid residues for efficient binding to HLA-B35, modified peptides were designed. Two of these analogues were found to induce higher PBL- and tumor-infiltrating lymphocyte-specific responses than the parental peptide, suggesting that they could be more immunogenic in HLA-B*3501 melanoma patients. These data have important implications for the formulation of polypeptide-based vaccines as well as for the monitoring of melanoma-specific CTL response in HLA-B*3501 melanoma patients.

Peptide-based cancer vaccines

The characterization of tumor antigens recognized by T lymphocytes has provided the opportunity to immunize cancer patients with well-defined peptides. Differentiation and tumor-specific antigens are expressed in a significant proportion of patients with cancer. Pilot studies have involved many patients with melanoma. No major toxicity has been reported after peptide vaccination. The clinical efficacy of peptide vaccines is limited to a minority of patients and the response rate is less than 20%. Some regressions have been complete and long-lasting. The development of this approach, and that of other methods to deliver tumor antigens, depends on clinical empirism to improve the therapeutic efficacy of the vaccine as well as the accurate understanding of the immune mechanisms involved in vivo.

Insights into antigen processing gained by direct analysis of the naturally processed class I MHC associated peptide repertoire

MHC class I molecules are responsible for the presentation of antigenic peptides to CD8+ T lymphocytes. Based on their relatively promiscuous binding of peptides, these molecules display information derived from a large fraction of proteins that are made inside the cell. This review describes our characterization of the peptides comprising this repertoire, with particular attention given to their complexity and quantities, their post-translational modification, and the pathways leading to their expression.

An alternative open reading frame of the human macrophage colony-stimulating factor gene is independently translated and codes for an antigenic peptide of 14 amino acids recognized by tumor-infiltrating CD8 T lymphocytes

We show that cytotoxic T lymphocytes (CTLs) infiltrating a kidney tumor recognize a peptide encoded by an alternative open reading frame (ORF) of the macrophage colony-stimulating factor (M-CSF) gene. Remarkably, this alternative ORF, which is translated in many tumors concurrently with the major ORF, is also translated in some tissues that do not produce M-CSF, such as liver and kidney. Such a dissociation of the translation of two overlapping ORFs from the same gene is unexpected. The antigenic peptide encoded by the alternative ORF is presented by human histocompatibility leukocyte antigen (HLA)-B*3501 and has a length of 14 residues. Peptide elution indicated that tumor cells naturally present this 14 mer, which is the longest peptide known to be recognized by CTLs. Binding studies of peptide analogues suggest that it binds by its two extremities and bulges out of the HLA groove to compensate for its length.

Differential processing of class-I-restricted epitopes by the standard proteasome and the immunoproteasome

Upon exposure to IFN-gamma, the standard proteasome is replaced by the immunoproteasome, which contains LMP2, LMP7 and MECL1, and is considered more efficient at producing antigenic peptides presented to CD8(+) T cells. This view has been challenged this year by reports showing that some epitopes, mainly of self origin, are not processed by the immunoproteasome and that mature dendritic cells constitutively express immunoproteasomes and therefore cannot efficiently present such epitopes.

A human CTL recognizes a caspase-8-derived peptide on autologous HLA-B*3503 molecules and two unrelated peptides on allogeneic HLA-B*3501 molecules

A CTL clone that recognizes autologous tumor cells was previously isolated from the blood of a head-and-neck cancer patient. The Ag was identified as peptide FPSDSWCYF presented by autologous HLA-B*3503 molecules. This peptide was encoded by a mutated CASP-8 gene, which is implicated in the triggering of apoptosis. Here, we show that this CTL clone, which expresses a single TCR, also recognizes two unrelated peptides on allogeneic HLA-B*3501 molecules. One peptide, HIPDVITY, is encoded by squalene synthase, and the other one, QFADVIVLF, is encoded by 2-hydroxyphytanoyl-CoA lyase. Both genes are expressed ubiquitously. These antigenic peptides are processed and presented by HLA-B*3501 cells. The two HLA-B35 alleles are closely related. Our results might reinforce the notion that the recognition of allogeneic HLA molecules depends on the presence in their groove of a limited number of peptides processed from ubiquitous proteins.