Identification and characterization of a HER-2/neu epitope as a potential target for cancer immunotherapy

Our aim is to develop peptide vaccines that stimulate tumor antigen-specific T-lymphocyte responses against frequently detected cancers. We describe herein a novel HLA-A*0201-restricted epitope, encompassing amino acids 828–836 (residues QIAKGMSYL), which is naturally presented by various HER-2/neu ⁺ tumor cell lines. HER-2/neu(828-836), [HER-2(9₈₂₈)], possesses two anchor residues and stabilized HLA-A*0201 on T2 cells in a concentration-dependent Class I binding assay. This peptide was stable for 3.5 h in an off-kinetic assay. HER-2(9₈₂₈) was found to be immunogenic in HLA-A*0201 transgenic (HHD) mice inducing peptide-specific and functionally potent CTL and long-lasting anti-tumor immunity. Most important, using HLA-A*0201 pentamer analysis we could detect increased ex vivo frequencies of CD8⁺ T-lymphocytes specifically recognizing HER-2(9₈₂₈) in 8 out of 20 HLA-A*0201⁺ HER-2/neu ⁺ breast cancer patients. Moreover, HER-2(9₈₂₈)-specific human CTL recognized the tumor cell line SKOV3.A2 as well as the primary RS.A2.1.DR1 tumor cell line both expressing HER-2/neu and HLA-A*0201. Finally, therapeutic vaccination with HER-2(9₈₂₈) in HHD mice was proven effective against established transplantable ALC.A2.1.HER tumors, inducing complete tumor regression in 50% of mice. Our data encourage further exploitation of HER-2(9₈₂₈) as a promising candidate for peptide-based cancer vaccines.     

Generation of human tumor-specific CTLs in HLA-A2.1–transgenic mice using unfractionated peptides from eluates of human primary breast and ovarian tumors

HER-2/neu oncoprotein is overexpressed in a variety of human tumors and is associated with malignant transformation and aggressive disease. Due to its overexpression in tumor cells and because it has been shown to be immunogenic, this protein represents an excellent target for T-cell immunotherapy. Peptide extracts derived from primary HLA-A*0201-positive (+) HER-2/neu⁺ human tumors by acid elution (acid cell extracts (ACEs)) were tested for their capacity to elicit in HLA-A*0201 transgenic mice, cytotoxic T lymphocytes (CTLs) lysing HLA-A*0201⁺ HER-2/neu⁺ tumor cells. Injections of ACE in transgenic mice induced CTLs capable of specifically lysing HER-2/neu⁺ tumor cell lines (also including the original HER-2/neu⁺ primary tumor cells from which the ACEs were derived) in an HLA-A*0201–restricted fashion. Adoptive transfer of ACE-induced CTLs was sufficient to significantly prolong survival of SCID mice inoculated with HLA-A*0201⁺ HER-2/neu⁺ human tumor cell lines. Cytotoxicity of such ACE-induced CTL lines was directed, at least as detected herein, also against the HER-2/neu peptides HER-2 (9₃₆₉) and HER-2 (9₄₃₅) demonstrating the immunodominance of these epitopes. HER-2 peptide–specific CTLs generated in the HLA-A*0201–transgenic mice, upon peptide immunization, lysed in vitro HER-2/neu⁺ human tumor cell lines in an HLA-A*0201–restricted manner and, when adoptively transferred, conferred sufficient protection in SCID mice inoculated with the same human tumor cell lines as above. However, CTLs induced by ACEs displayed enhanced efficacy in the therapy of xenografted SCID mice compared with the HER-2 peptide–specific CTLs (i.e., HER-2 [9₃₆₉] or HER-2 [9₄₃₅]). Even by administering mixtures of CTLs specific for each of these peptides, the prolongation of survival achieved was still inferior compared with that obtained with ACE-induced CTLs. This suggested that additional epitopes may contribute to the immunogenicity of such tumor-derived ACEs. Thus, immunization with ACEs from HER-2/neu⁺ primary tumor cells appears to be an effective approach to generate multiple and potent CTL-mediated immune responses against HER-2/neu⁺ tumors expressing the appropriate HLA allele(s). By screening ACE-induced CTL lines with synthetic peptides encompassing the HER-2/neu sequence, it is feasible to identify immunodominant epitopes which may be used in mixtures as vaccines with enhanced efficacy in both the prevention and therapy of HER-2/neu⁺ malignancies.This work was supported by grants from the Regional Operational Program Attika (No. 20, MIS code 59605GR) to M.P., and from the GSRT Program (No. PENED 01ED55) to C.N.B.     

Ontak reduces the immunosuppressive tumor environment and enhances successful therapeutic vaccination in HER-2/<Emphasis Type="Italic">neu</Emphasis>-tolerant mice

Disrupting tumor-mediated mechanisms suppressing host immunity represents a novel approach to tumor immunotherapy. Depletion of regulatory T cells (Tregs) increases endogenous anti-tumor immunity and the efficacy of active immunotherapy in experimental tumor models. HLA-A2.1/HLA-DR1 (A2.1/DR1) × BALB- neuT ⁺ (neuT ⁺) triple transgenic mice represent an improvement over neuT ⁺ mice for evaluating vaccination regimens to overcome tolerance against HER-2/neu. We questioned whether depletion of Tregs with Denileukin diftitox (Ontak) enhances the efficacy of a therapeutic vaccine consisting of HER-2(85–94) (p85) CTL and HER-2(776–790) (p776) Th peptides against the growth of TUBO.A2 transplantable tumor in male A2.1/DR1 × neuT ⁺ Tg mice. While the therapeutic vaccine primed the tumor-reactive CD8⁺ CTLs and CD4⁺ effector T lymphocytes (Teffs) compartment, inducing activation, tumor infiltration, and tumor rejection or delay in tumor growth, treatment with Ontak 1 day prior to vaccination resulted in enhanced CD4⁺ and CD8⁺ T-cell-mediated vaccine-specific immune responses in the periphery. This was closely associated with greater infiltration and a striking change in the intratumor balance of Tregs and vaccine-specific CTLs/Teffs that directly correlated with markedly enhanced antitumor activity. The data suggest that Tregs control both CD4⁺ and CD8⁺ T-cell activity within the tumor, emphasize the importance of the intratumor ratio of vaccine-specific lymphocytes to Tregs, and demonstrate significant inversion of this ratio and correlation with tumor rejection during Ontak/vaccine immunotherapy.     

Substitution analog peptide derived from HER-2 can efficiently induce HER-2-specific, HLA-A24 restricted CTLs

In order to broaden the possibility for anti-HER-2/neu (HER-2) immune targeting, it is important to identify HLA-A24 restricted peptide epitopes derived from HER-2, since HLA-A24 is one of the most common alleles in Japanese and Asian people. In the present study, we have screened HER-2-derived, HLA-A24 binding peptides for cytotoxic T lymphocyte (CTL) epitopes. A panel of HER-2-derived peptides with HLA-A24 binding motifs and the corresponding analogs designed to enhance HLA-A24 binding affinity were selected. Identification of HER-2-reactive and HLA-A24 restricted CTL epitopes were performed by a reverse immunology approach. To induce HER-2-reactive and HLA-A24 restricted CTLs, PBMCs from healthy donors were repeatedly stimulated with monocytes-derived, mature DCs pulsed with HER-2 peptide. Subsequent peptide-induced T cells were tested for the specificity by enzyme linked immunospot, cytotoxicity and tetramer assays. CTL clones were then obtained from the CTL lines by limiting dilution. Of the peptides containing HLA-A24 binding motifs, 16 peptides (nine mers) including wild type peptides (IC₅₀<1,000 nM) and substituted analog peptides (IC₅₀<50 nM) were selected for the present study. Our studies show that an analog peptide, HER-2(905AA), derived from HER-2(905) could efficiently induce HER-2-reactive and HLA-A24 restricted CTLs. The reactivity of the HER-2(905AA)-induced CTL (CTL905AA) was confirmed by different CTL assays. The CTL905AA clones also were able to lyse HER-2(+), HLA-A24(+) tumor cells and cytotoxicity could be significantly reduced in cold target inhibition assays using cold targets pulsed with the HER-2(905) wild type peptide as well as the inducing HER-2(905AA) analog peptide. A newly identified HER-2(905) peptide epitope is naturally processed and presented as a CTL epitope on HER-2 overexpressing tumor cells, and an MHC anchor-substituted analog, HER-2(905AA), can efficiently induce HER-2-specific, HLA-A24 restricted CTLs.     

STEAP, a prostate tumor antigen, is a target of human CD8+ T cells

STEAP is a recently identified protein shown to be particularly overexpressed in prostate cancer and also present in numerous human cancer cell lines from prostate, pancreas, colon, breast, testicular, cervical, bladder and ovarian carcinoma, acute lymphocytic leukemia and Ewing sarcoma. This expression profile renders STEAP an appealing candidate for broad cancer immunotherapy. In order to investigate if STEAP is a tumor antigen that can be targeted by specific CD8⁺ T cells, we identified two high affinity HLA-A*0201 restricted peptides (STEAP_86–94 and STEAP_262–270). These peptides were immunogenic in vivo in HLA-A*0201 transgenic HHD mice. Peptide specific murine CD8 T cells recognized COS-7 cells co-transfected with HHD (HLA-A*0201) and STEAP cDNA constructs and also HLA-A*0201⁺ STEAP⁺ human tumor cells. Furthermore, STEAP_86–94 and STEAP_262–270 stimulated specific CD8⁺ T cells from HLA-A*0201⁺ healthy donors, and these peptide specific CD8⁺ T cells recognized STEAP positive human tumor cells in an HLA-A*0201-restricted manner. Importantly, STEAP_86–94-specific T cells were detected and reactive in the peripheral blood mononuclear cells in NSCLC and prostate cancer patients ex vivo. These results show that STEAP can be a target of anti-tumor CD8⁺ T cells and that STEAP peptides can be used for a broad-spectrum-tumor immunotherapy.     

HER-2/neu peptide specificity in the recognition of HLA-A2 by natural killer cells

Although natural killer (NK) cells have been described as non-MHC-restricted, new evidence suggests that NK activity can be either up- or down-regulated after interaction with the peptide–MHC-class-I complex expressed on target cells. However, the epitope(s) recognized by NK cells have remained ill-defined. We investigated NK cell recognition of synthetic peptides representing a portion of a self-protein encoded by the HER-2/neu (HER-2) proto-oncogene and presented by HLA-A2. HER-2 nonapeptides C85, E89, and E75 were found partially to protect T2 targets from lysis by freshly isolated and interleukin-2(IL-2)-activated NK cells (either HLA-A2⁺ or A2⁻). This inhibition was not solely due to changes in the level of HLA-A2 expression or conformation of serological HLA-A2 epitopes. Using single-amino-acid variants at position 1 (P1) of two HER-2 peptides, we observed that protection of targets was dependent on the sequence and the side-chain. These results suggest similarities in the mechanism of target recognition by NK and T cells. This information may be important for understanding the mechanisms of tumor escape from immunosurveillance and could help explain the aggressiveness of HER-2-overexpressing tumor cells. Received: 16 March 1999 / Accepted: 3 June 1999     

Promoting effect of Antrodia camphorata as an immunomodulating adjuvant on the antitumor efficacy of HER-2/neu DNA vaccine

It is well known that DNA vaccines induce protective humoral and cell-mediated immune responses in several animal models. Antrodia camphorata (AC) is a unique basidiomycete fungus of the Polyporaceae family that only grows on the aromatic tree Cinnamomum kanehirai Hayata (Lauraceae) endemic to Taiwan. Importantly, AC has been shown to be highly beneficial in the treatment and prevention of cancer. The goal of this study was to investigate whether AC is able to augment the antitumor immune properties of a HER-2/neu DNA vaccine in a mouse model in which p185neu is overexpressed in MBT-2 tumor cells. Compared with the mice that received the HER-2/neu DNA vaccine alone, co-treatment with AC suppressed tumor growth and extended the survival rate. This increase in the antitumor efficacy was attributed to the enhancement of the Th1-like cellular immune response by the HER-2/neu DNA vaccine–AC combination. Evidence for this came from the marked increase in the IFN-γ mRNA expression in CD4⁺ T cells in the draining inguinal lymph nodes, an increase in the number of functional HER-2/neu-specific CTLs, and the increased tumor infiltration of both CD4⁺ and CD8⁺ T cells, depletion of which abolishes the antitumor effect of the HER-2/neu DNA vaccine–AC therapy. Our results further indicate that the treatment of mice with AC enhanced DC activation and production of Th1-activating cytokines (e.g. IL-12, and IFN-α) in the draining lymph nodes, which were sufficient to directly stimulate T cell proliferation and higher IFN-γ production in response to ErbB2. Overall, these results clearly demonstrate that AC represents a promising immunomodulatory adjuvant that could enhance the therapeutic potency of HER-2/neu DNA vaccines in cancer therapy.     

Identification of SART3-derived peptides having the potential to induce cancer-reactive cytotoxic T lymphocytes from prostate cancer patients with HLA-A3 supertype alleles

SART3-derived peptides applicable to prostate cancer patients with HLA-A3 supertype alleles were identified in order to expand the possibility of an anti-cancer vaccine, because the peptide vaccine candidates receiving the most attention thus far have been the HLA-A2 and HLA-A24 alleles. Twenty-nine SART3-derived peptides that were prepared based on the binding motif to the HLA-A3 supertype alleles (HLA-A11, -A31, and -A33) were first screened for their recognizability by immunoglobulin G (IgG) of prostate cancer patients and subsequently for the potential to induce peptide-specific cytotoxic T lymphocytes (CTLs) from HLA-A3 supertype⁺ prostate cancer patients. As a result, five SART3 peptides were frequently recognized by IgG, and two of them—SART3 _511–519 and SART3 _734–742—efficiently induced peptide-specific and cancer-reactive CTLs. Their cytotoxicity toward prostate cancer cells was ascribed to peptide-specific and CD8⁺ T cells. These results indicate that these two SART3 peptides could be promising candidates for peptide-based immunotherapy for HLA-A3 supertype⁺ prostate cancer patients. Grant sponsor This study was supported in part by KAKENHI (Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan) (no. 12213134 to K. Itoh, and no. 18591449 to M. Harada), Research Center of Innovative Cancer Therapy of 21st Century COE Program for Medical Science to K. Itoh, and the Ministry of Health, Labor and Welfare, Japan (15–17 to M. Harada).     

Specific CD8+ T cell responses to HLA-A2 restricted MAGE-A3 p271–279 peptide in hepatocellular carcinoma patients without vaccination

The MAGE-A3 protein, one of the promising tumor antigens for immunotherapy, is highly expressed in human hepatocellular carcinoma (HCC). In this study, we estimated the specific CD8⁺ T cell immune response to MAGE-A3 p271–279 peptide (M3₂₇₁) in the peripheral blood of HCC patients without antigen vaccination in order to evaluate its immunotherapeutic potential in these patients. After expansion in vitro, the functional IFN-γ producing M3₂₇₁ specific CD8⁺ T cells were detected in 30.8% (8/26) of HLA-A2⁺MAGE-A3⁺ HCC patients. The effector CD8⁺ T cells could release cytotoxic molecules of granzyme B and perforin after restimulation with natural HLA-A2⁺MAGE-A3⁺ HCC cell lines in the samples tested. The functional supertype of HLA-A2 in the presentation of HLA-A*0201 restricted M3₂₇₁ peptide has been identified in the Chinese HCC patients of Han ethnicity, that widely expanded the applicability of this tumor peptide vaccine in Chinese HCC patients. Thus, the functionally detectable pre-existence of M3₂₇₁-specific CD8⁺ T cells in HCC patients makes M3₂₇₁ a potential target for immunotherapy in these patients. The responsive CD8⁺ T cells to both NY-ESO-1 and MAGE-A3 antigens provide a rationale for the application of a bivalent vaccine in HCC patients with tumors expressing both antigens. H-G Zhang, H-S Chen, and J-R Peng are contributed equally to this paper.     

A CD80-transfected human breast cancer cell variant induces HER-2/neu–specific T cells in HLA-A*02–matched situations in vitro as well as in vivo

Adjuvant treatment is still only working in a small percentage of breast cancer patients. Therefore, new strategies need to be developed. Immunotherapies are a very promising approach because they could successfully attack tumor cells in the stage of dormancy. To assess the feasibility of using an allogeneic approach for vaccination of breast cancer patients, we selected a CD80-transfected breast cancer cell line based on its immunogenic properties. Using CD80⁺ KS breast cancer cells and human leukocyte antigen (HLA)-A*02–matched peripheral blood mononuclear cells (PBMCs) of breast cancer patients in allogeneic mixed lymphocyte–tumor cell cultures (MLTCs), it was possible to isolate HLA-A*02–restricted cytotoxic T cells (CTLs). Furthermore, a genetically modified KS variant expressing influenza A matrix protein serving as a surrogate tumor-associated antigen (TAA) was able to stimulate flu peptide-specific T cells alongside the induction of alloresponses in MLTCs. KS breast cancer cells were demonstrated to express already known TAAs such as CEA, MUC-1, MAGE-1, MAGE-2, and MAGE-3. To further improve antigenicity, HER-2/neu was added to this panel as a marker antigen known to elicit HLA-A*02–restricted CTLs in patients with breast cancer. Thus, the antigen-processing and antigen-presentation capacity of KS cells was further demonstrated by the stimulation of HER-2/neu–specific CD8⁺ T cells in PBMCs of breast cancer patients in vitro. These results gave a good rationale for a phase I/II trial, where the CD80⁺ HER-2/neu–overexpressing KS variant is actually used as a cellular vaccine in patients with metastatic breast cancer. As a proof of principle, we present data from two patients where a significant increase of interferon- (IFN-) release was detected when postvaccination PBMCs were stimulated by allogeneic vaccine cells as well as by HLA-A*02–restricted HER-2/neu epitopes. In whole cell vaccine trials, monitoring is particularly challenging because of strong alloresponses and limited knowledge of TAAs. In this study, a panel of HER-2/neu epitopes, together with the quantitative real time (qRT)-PCR method to analyze vaccine-induced cytokines secreted by T cells, proved to be highly sensitive and feasible to perform an immunological staging following vaccination.     

Identification of a new HLA-A*0201-restricted cytotoxic T lymphocyte epitope from CML28

Identification of cytotoxic T lymphocyte (CTL) epitopes from additional tumor antigens is essential for the development of specific immunotherapy of malignant tumors. CML28, a recently discovered cancer-testis (CT) antigen from chronic myelogenous leukemia, is considered to be a promising target of tumor-specific immunotherapy. Because HLA-A*0201 is one of the most common histocompatibility molecule in Chinese, we aim at identifying CML28 peptides presented by HLA-A*0201. A panel of CML28-derived antigenic peptides was predicted using a computer-based program. Four peptides with highest predicted score were synthesized and tested for their binding affinities to HLA-A*0201 molecule. Then these peptides were assessed for their immunogenicity to elicit specific immune responses mediated by CTLs both in vitro, from PBMCs sourced from four healthy HLA-A*0201⁺ donors, and in vivo, in HLA-A*0201 transgenic mice. One of the tested peptides, CML28_(173–181), induced peptide-specific CTLs in vitro as well as in vivo, which could specifically secrete IFN-γ and lyse major histocompatibility complex (MHC)-matched tumor cell lines endogenously expressing CML28 antigen and CML28_(173–181) pulsed Jurkat-A2/Kb cells, respectively. These results demonstrate that CML28_(173–181) is a naturally processed and presented CTL epitope with HLA-A*0201 motif and has a promising immunogenicity both in vitro and in vivo. As CML28 is expressed in a large variety of histological tumors besides chronic myelogenous leukemia, we propose that the newly identified epitope, CML28_(173–181), would be of potential use in peptide-based, cancer-specific immunotherapy against a broad spectrum of tumors.     

A new epitope peptide derived from hepatitis C virus 1b possessing the capacity to induce cytotoxic T-lymphocytes in HCV1b-infected patients with HLA-A11, -A31, and -A33

Background Hepatitis C virus (HCV) frequently causes chronic hepatitis, cirrhosis, and hepatocellular carcinoma after long-term persistent infection. Among various genotypes of HCV, HCV1b is resistant to standard interferon therapy, and thus the development of new treatment modality is needed. Results To provide a scientific basis for specific immunotherapy for HCV1b, we investigated HCV1b-derived epitope peptides recognized by human leukocyte antigen (HLA)-A11, -A31, or -A33-restricted cytotoxic T-lymphocytes (CTLs), and report here three novel vaccine candidate peptides selected by both antibody screening and CTL-inducing capacity from among 46 peptides of conserved regions of HCV1b sequences with binding motifs to HLA-A11, -A31, and -A33. Significant levels of IgG reactive to each of the three peptides were detected in the plasma of more than 50% of the HCV1b⁺ patients. One peptide at positions 30–39 of the core protein induced peptide-specific CTLs from peripheral blood mononuclear cells (PBMCs) of HLA-A11⁺, -A31⁺, and -A33⁺ patients. The other two peptides at positions 35–43 of the core protein and at positions 918–926 of the non-structural protein 2 also induced peptide-specific CTLs from the PBMCs of HLA-A11⁺ and -A33⁺ patients. Conclusion Therefore, the peptide at positions 30–39 of the core protein could be an appropriate target molecule of specific immunotherapy for all HLA-A11⁺, -A31⁺, and -A33⁺ patients with HCV1b-related diseases.     

Peptide-specific, allogeneic T cell response in vitro induced by a self-peptide binding to HLA-A2

The role of the bound peptide in alloreactive T-cell recognition is controversial, ranging from pep-tide-independent to peptide-specific recognition of alloreactive T-cells. The aim of this study is to find the evidence that there exist peptide/MHC complex (pMHC)-specific CTLs among alloreactive T cells generated with long-term mixed lymphocytes culture (LTMLC). A single pMHC was manipulated by loading the TAP-defective, HLA-A2 expressing T2 cells with a viral peptide (LMP2A426-434) or a self-peptide (Tyr369-377). The PBLs samples from 4 HLA-A2 positive (HLA-A2 ve) and 4 HLA-A2 negative (HLA-A2-ve) donors were included in this study. The HLA-A2 ve PBL co-cultured with the LMP2A426-434 pulsed T2 (T2/LMP) stands for the nominal T-cell response to a viral antigen, and the HLA-A2-ve PBLs co-cultured with the Tyr369-377 pulsed T2 (T2/Tyr) for alloreactive T-cell response to an allogeneic antigen. The specificity of the expanded CTLs after the LTMLC was detected by their specific cytotoxicity and binding ability to specific pMHC-tetramer. An HLA-A2 restricted, HIV peptide (Gag77-85)was included for control. The cultural bulk of HLA-A2 ve PBLs with the T2/LMP showed an elevated specific cytotoxicity against the T2/LMP compared to that against the T2/HIV (26.52%±3.72% vs 7.01%±0.87%, P<0.001), and an increased frequency of binding to LMP-tetramer compared to that binding to HIV-tetramer (0.98%±0.33% vs 0.05%±0.01%, P=0.0014). The cultural bulk of HLA-A2-ve PBLs with the T2/Tyr showed a more active cytotoxicity against the T2/Tyr than that against T2/HIV (28.07%±2.58% vs 6.87%±0.01 %, P<0.001), and a higher frequency of binding to the Tyr-tetramer than that binding to the HIV-tetramer (0.88%±0.3% vs 0.06%±0.03%, P=0.0018). Our results indicate that the LTMLC is able to expand the viral antigen-specific CTLs as well as allogeneic antigen-specific CTLs. A relatively large proportion of alloreactive CTLs should be pMHC-specific, i.e., the specificity of the alloreactive lines depends on both the bound peptide and the allotype of MHC. Our observations support the hypothesis that the cumulative effect of T cells specific to each peptide epitope could account for the strength and diversity of the alloresponse. The method using manipulated pMHC and the LTMLC to generate pMHC-specific, alloreactive CTLs is of potential importance for adoptive T-cell immunotherapy.     

Cancer immunotherapy by antisense suppression of Ii protein in MHC-class-II-positive tumor cells

This study was aimed at creating a more effective tumor cell vaccine by suppressing Ii protein in the presence of MHC class II molecules within a cancer cell. Absence of the Ii protein, which normally blocks the antigenic-peptide-binding site of MHC class II molecules at synthesis in the endoplasmic reticulum, presumably increases the range of cancer-related epitopes presented to CD4⁺ helper T cells. Effective suppression of Ii protein was achieved with an antisense, phosphorothioate oligonucleotide, which was selected on the basis of (1) the RNase H activation assay, (2) an assay for Ii protein suppression, and (3) a test for potency with respect to the extent of base sequence (“sequence walking”). The SaI murine sarcoma, which is MHC-class-I⁺ and MHC-class-II⁻, Ii-protein⁻, upon transfection with genes for either interferon γ or the MHC class II transactivator, came to express MHC class II molecules and Ii protein. In each line of transfected tumor cells, the antisense oligonucleotide profoundly suppressed Ii protein in 35%–55% cells, without affecting expression of MHC class II molecules. Inoculation of mice with such Ii-protein-suppressed tumor vaccine cells, after either formaldehyde fixation or X-irradiation, led to much greater protection against challenge with the parental SaI sarcoma than did inoculation with untreated cells. This approach to cancer cell vaccination can be applied in a wide range of human tumors. Received: 22 June 1999 / Accepted: 28 July 1999     

Spontaneous T cell responses to melanoma differentiation antigens from melanoma patients and healthy subjects

The spontaneous cytotoxic T cell responses to melanoma differentiation antigens and influenza matrix peptide were compared in 20 HLA-A2⁺ melanoma patients and 17 healthy A2⁺ individuals. Cytotoxic T lymphocyte (CTL) responses were determined by mixed lymphocyte peptide culture (MLPC) involving two stimulations of unfractionated peripheral blood lymphocytes (PBLs) with peptide in vitro. CTL responses to Melan-A 9-mer (amino acids 27–35, AAGIGILTV) peptide were detected in 4 out of 16 normal individuals, but in none of the melanoma patients. CTL specific for influenza matrix peptide were frequently found in both normal individuals and melanoma patients, suggesting that generalized immuno-suppression was not responsible for this difference. No significant responses were observed in either normal individuals or melanoma patients to Melan-A 10-mer (26–35, EAAGIGILTV), two gp100 epitopes (280–288, YLEPGPVTA; 457–466, LLDGTATLRL) and two tyrosinase epitopes (1–9, MLLAVLYCL; 368–376, YMDGMSQV). Melan-A (27–35)-specific CTL cells generated by normal individuals and melanoma patients recognized both synthetic peptide-pulsed T2 cells and two HLA-A2⁺, Melan-A⁺ melanoma cell lines (ME272, LAR1) in an antigen-specific, MHC class I restricted manner. T cells generated against Melan-A 9-mer were also able to recognize Melan-A 10-mer-pulsed target cells. Spontaneous CTL responses to Melan-A 9-mer from three known responder normal individuals were further evaluated over a prolonged time course (6–11 months). All 3 subjects demonstrated specific Melan-A 9-mer responses throughout the study period, although lytic activity fluctuated over time for a given individual. We found the MLPC assay to be reliable and easy to perform for monitoring T cell responses, although it may still not be sufficiently sensitive to detect low numbers of precursor T cells. Received: 21 May 1998 / Accepted: 23 July 1998     

Treatment of ovarian cancer cell lines with 5-aza-2′-deoxycytidine upregulates the expression of cancer-testis antigens and class I major histocompatibility complex-encoded molecules

Purpose  To test the hypothesis that decrease in DNA methylation will increase the expression of cancer-testis antigens (CTA) and class I major histocompatibility complex (MHC)-encoded molecules by ovarian cancer cells, and thus increase the ability of these cells to be recognized by antigen-reactive CD8⁺ T cells. Methods  Human ovarian cancer cell lines were cultured in the presence or absence of varying concentrations of the DNA demethylating agent 5-aza-2′-deoxycytidine (DAC) for 3–7 days. The expression levels of 12 CTA genes were measured using the polymerase chain reaction. The protein expression levels of class I MHC molecules and MAGE-A1 were measured by flow cytometry. T cell reactivity was determined using interferon-γ ELISpot analysis. Results  DAC treatment of ovarian cancer cell lines increased the expression of 11 of 12 CTA genes tested including MAGE-A1, MAGE-A3, MAGE-A4, MAGE-A6, MAGE-A10, MAGE-A12, NY-ESO-1, TAG-1, TAG-2a, TAG-2b, and TAG-2c. In contrast, DAC treatment decreased the already low expression of the MAGE-A2 gene by ovarian cancer cells, a finding not previously observed in cancers of any histological type. DAC treatment increases the expression of class I MHC molecules by the cells. These effects were time-dependent over a 7-day interval, and were dose-dependent up to 1–3 μM for CTA and up to 10 μM for class I MHC molecules. Each cell line tested had a unique pattern of gene upregulation after exposure to DAC. The enhanced expression levels increased the recognition of 2 of 3 antigens recognized by antigen-reactive CD8⁺ T cells. Conclusions  These results demonstrate the potential utility of combining DAC therapy with vaccine therapy in an attempt to induce the expression of antigens targeted by the vaccine, but they also demonstrate that care must be taken to target inducible antigens. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Relationship between CD8-dependent antigen recognition,T cell functional avidity,and tumor cell recognition

Effective immunotherapy using T cell receptor (TCR) gene-modified T cells requires an understanding of the relationship between TCR affinity and functional avidity of T cells. In this study, we evaluate the relative affinity of two TCRs isolated from HLA-A2-restricted, gp100-reactive T cell clones with extremely high functional avidity. Furthermore, one of these T cell clones, was CD4⁻CD8⁻ indicating that antigen recognition by this clone was CD8 independent. However, when these TCRs were expressed in CD8⁻ Jurkat cells, the resulting Jurkat cells recognized gp100:209–217 peptide loaded T2 cells and had high functional avidity, but could not recognize HLA-A2⁺ melanoma cells expressing gp100. Tumor cell recognition by Jurkat cells expressing these TCRs could not be induced by exogenously loading the tumor cells with the native gp100:209–217 peptide. These results indicate that functional avidity of a T cell does not necessarily correlate with TCR affinity and CD8-independent antigen recognition by a T cell does not always mean its TCR will transfer CD8-independence to other effector cells. The implications of these findings are that T cells can modulate their functional avidity independent of the affinity of their TCRs. Companion Paper: “Characterization of MHC class-I restricted TCRαβ⁺ CD4⁻ CD8⁻ double negative T cells recognizing the gp100 antigen from a melanoma patient after gp100 vaccination” by Simon Voelkl, Tamson V. Moore, Michael Rehli, Michael I. Nishimura, Andreas Mackensen, and Karin Fischer. doi:.     

Intradermal DNA electroporation induces survivin-specific CTLs, suppresses angiogenesis and confers protection against mouse melanoma

Survivin is an intracellular tumor-associated antigen that is broadly expressed in a large variety of tumors and also in tumor associated endothelial cells but mostly absent in differentiated tissues. Naked DNA vaccines targeting survivin have been shown to induce T cell as well as humoral immune responses in mice. However, the lack of epitope-specific CD8+ T cell detection and modest tumor protection observed highlight the need for further improvements to develop effective survivin DNA vaccination approaches. Here, the efficacy of a human survivin DNA vaccine delivered by intradermal electroporation (EP) was tested. The CD8+ T cell epitope surv_20–28 restricted to H-2 Db was identified based on in-silico epitope prediction algorithms and binding to MHC class I molecules. Intradermal DNA EP of mice with a human survivin encoding plasmid generated CD8+ cytotoxic T lymphocyte (CTL) responses cross-reactive with the mouse epitope surv_20–28, as determined by intracellular IFN-γ staining, suggesting that self-tolerance has been broken. Survivin-specific CTLs displayed an activated effector phenotype as determined by CD44 and CD107 up-regulation. Vaccinated mice displayed specific cytotoxic activity against B16 and peptide-pulsed RMA-S cells in vitro as well as against surv_20–28 peptide-pulsed target cells in vivo. Importantly, intradermal EP with a survivin DNA vaccine suppressed angiogenesis in vivo and elicited protection against highly aggressive syngeneic B16 melanoma tumor challenge. We conclude that intradermal EP is an attractive method for delivering a survivin DNA vaccine that should be explored also in clinical studies.     

Identification of a novel immunogenic HLA-A*0201-binding epitope of HER-2/neu with potent antitumor properties

HER-2/neu oncoprotein is overexpressed in a variety of human tumors and is associated with aggressive disease. Immunogenic HER-2/neu CTL epitopes have been used as vaccines for the treatment of HER-2/neu positive malignancies with limited success. By applying prediction algorithms for MHC class I ligands and proteosomal cleavages, in this study, we describe the identification of HER-2/neu decamer LIAHNQVRQV spanning residues 85-94 (HER-2(10(85))). HER-2(10(85)) proved to bind with high affinity to HLA-A2.1 and was stable for 4 h in an off-kinetics assay. This peptide was immunogenic in HLA-A2.1 transgenic (HHD) mice inducing peptide-specific CTL, which responded to tumor cell lines of various origin coexpressing human HER-2/neu and HLA-A2.1. This demonstrates that HER-2(10(85)) is naturally processed from endogenous HER-2/neu. Five of sixteen HER-2/neu+ HLA-A2.1+ breast cancer patients analyzed had HER-2(10(85))-reactive T cells ranging from 0.35-0.70% of CD8+ T cells. Depletion of T regulatory cells from PBMC enabled the rapid expansion of HLA-A2.1/HER-2(10(85))pentamer+/CD8+ cells (PENT+/CD8+), whereas significantly lower numbers of CTL could be generated from unfractionated PBMC. HER-2(10(85))-specific human CTL recognized the HER-2/neu+ HLA-A2.1+ tumor cell line SKBR3.A2, as determined by IFN-gamma intracellular staining and in the high sensitivity CD107alpha degranulation assay. Finally, HER-2(10(85)) significantly prolonged the survival of HHD mice inoculated with the transplantable ALC.A2.1.HER tumor both in prophylactic and therapeutic settings. These data demonstrate that HER-2(10(85)) is an immunogenic peptide, capable of eliciting CD8-mediated responses in vitro and in vivo, providing the platform for further exploitation of HER-2(10(85)) as a possible target for anticancer immunotherapy.     

Improved immunogenicity of an immunodominant epitope of the HER-2/neu protooncogene by alterations of MHC contact residues

The HER-2/neu (HER-2) oncogene is expressed in normal epithelial surfaces at low levels and overexpressed in several types of tumors. The low immunogenicity against this self tumor Ag can be improved by developing epitopes with amino acid replacements in their sequences. In this study, three HER-2/neu.369 (HER-2.369) analogue peptides, produced by modifying both anchor positions by introducing L, V, or T at position 2 and V at the C terminus, were analyzed for their capacity to induce CTLs in vitro from human PBMC and in vivo in HLA-A2.1/Kb transgenic mice. One of the analogues (HER-2.369 V2V9) sensitized target cells for HER-2-specific recognition by human CTLs and induced specific CTLs in vitro at 100-fold lower concentrations than the HER-2.369 wild-type epitope. These CTLs were also able to recognize the wild-type epitope and HER-2-expressing tumors in an MHC-restricted manner. Furthermore, a 100-fold lower amount of the HER-2.369 V2V9 analogue compared with the wild-type epitope was required to induce CTLs in HLA-A2.1/Kb transgenic mice. However, the V2V9 analogue demonstrated only marginally better binding to the MHC class I A2 allele compared with wild type. To establish thermodynamic parameters, we developed radiolabeled F3*Y analogues from both the HER-2.369 epitope and the V2V9 analogue. Our results indicate that the high biological activity of the HER-2.369 V2V9 epitope is associated with a slower dissociation kinetic profile, resulting in an epitope with greater HLA-A2 stability.