[Application of HLA-A*0201/WT1 pentamer combined with intracellular IFNgamma+ staining in detecting circulating WT1 specific T cells in leukemia]

This study was purposed to investigate the value of combination of pentamer and intracellular IFNgamma staining in the qualitative and quantitative detection of circulating antigen-specific T cells. WT1 expressions in 14 HLA-A*0201+ patients and their matched donors were detected by RT-PCR, and circulating WT1 specific T cells were assayed by HLA-A*0201/WT1 pentamer combined with intracellular IFNgamma+ staining. The results showed that the low level of WT1 expression was found only in 2 cases out of 14 donors, but different levels of WT1 expression could be observed in all leukemic patients. The WT1+CD8+ CTL and WT1+IFNgamma+ cells did not detected in all 14 donors, but WT1+CD8+ CTL cells in 2 patients and WT1+IFNgamma+ cells in 3 patients could be detected before transplantation respectively, there was no significant difference between them, while the WT1+CD8+ CTL cells and WT1+IFNgamma+ cells both could be detected in all 14 patients after transplantation, the positive detection rate after transplantation was obviously higher than that before transplantation. The WT1+CD8+ and WT1+ IFNgamma+ cells could be detected within 30 days after transplantation, but the positive detection rate of WT1+IFNgamma+ cells was higher than that of WT1+CD8+ CTL cells (p=0.014). The median peak value of WT1+CD8+ CTL cells was 0.18% in 14 patients, and the median peak value of WT1+IFNgamma+ cells was 0.83% in 14 patients, the later was significantly higher than former. The median peak time of WT1+CD8+ CTL cells was 75 days after transplantation, while the WT1+IFNgamma+ cells was 105 days after transplantation, there was no significant difference between them. It is concluded that pentamer and intracellular IFNgamma staining may effectively detect circulating WT1 specific T cells in leukemic patients, and the combination of these two methods profit to the exact qualitation and quantitation of circulating antigen-specific T cells.

WT1 peptide vaccination in a CML patient: induction of effective cytotoxic T lymphocytes and significance of peptide administration interval

Although antigen-specific immune responses including cytotoxic T cells (CTLs) against antigen peptide could be enhanced after tumor antigen peptide vaccinations, the immune responses do not necessarily result in a decrease or eradication of tumor cells in the vaccination trials. We focused on whether antigen-specific CTLs could be damaged by the repeated stimulation of antigenic peptide and whether regulatory T (Treg) cells would be increased by the administration of WT1 peptide. We administered WT1 peptide 22 times over 18 months in a CML patient who was being treated with imatinib. Although WT1 peptide administration every 2 weeks did not show any beneficial effects on the minimal residual disease (copies of bcr-abl transcripts), the transcripts remarkably decreased to the level of major molecular response after changing the administration interval of WT1 peptide from 2 to 4 weeks. An ex vivo study demonstrated that re-stimulation with WT1 peptide made WT1-specific T cells less reactive to WT1 tetramers and the impaired reactivity of CTLs lasted at least for 1 week. In addition, the cytotoxicity of the T cells was hampered by re-stimulation. Treg cells increased up to more than fivefold at the end of the WT1 administration period. The present findings suggested that the administration of the peptide every 4 weeks is superior to every 2 weeks. In addition, the findings that Treg cells increased gradually in accordance with the duration of WT1 peptide administration revealed the significance of manipulating Treg cells for establishing an efficient tumor antigen peptide vaccination.

Wilms' tumor 1 (WT1) peptide immunotherapy for gynecological malignancy

BACKGROUND

The object of this study was to investigate the safety and clinical response of immunotherapy targeting the WT1 (Wilms' tumor 1) gene product in patients with gynecological cancer.

PATIENTS AND METHODS

Twelve patients with WT1/human leukocyte antigen (HLA)-A*2402-positive gynecological cancer were included in a Phase II clinical trial of WT1 vaccine therapy. In all the patients, the tumors were resistant to standard therapy. The patients received intradermal injections of a HLA-A*2402-restricted, modified 9-mer WT1 peptide every week for 12 weeks. Tumor size, which was measured by computed tomography (CT), was determined every 4 weeks. The responses were analyzed according to Response Evaluation Criteria in Solid Tumors (RECIST).

RESULTS

The protocol was well tolerated; only local erythema occurred at the WT1 vaccine injection site. The clinical responses were as follows: stable disease (SD) in 3 patients and progressive disease (PD) in 9 patients. No patients had a complete (CR) or partial response (PR). The disease control rate was 25.0%.

CONCLUSION

Although a small, uncontrolled, nonrandomized trial, this study showed that WT1 vaccine therapy for patients with gynecological cancer was safe and produced a clinical response.

[Immunotherapy and cell therapy for myeloid leukemia]

To develop effective cellular immunotherapy for hematopoietic malignancies, the tumor-associated antigens that are recognized by cytotoxic T lymphocytes (CTL) must be identified. Recently, various leukaemia-associated antigens that are recognized by CTL in the context of HLA class I molecules have been identified. These include fusion gene products such as BCR-ABL and ETV6-AML1, proteinase 3, WT1, human telomerase reverse transcriptase, cyclophilin B, and PRAME. In addition, various target antigens associated with other hematopoietic malignancies have been also identified. On the basis of these findings, various clinical trials of immunotherapy for hematological malignancies, including peptide vaccination, dendritic cell therapy, adoptive transfer of CTL, T-cell receptor gene therapy have been ongoing. Here, the current status and future feasibility of cellular immunotherapy for leukemia are discussed.

[Human cytotoxic T lymphocyte responses specific to the DNA vaccine of Wilms' tumor gene product]

OBJECTIVE

To construct the eukaryotic expression vector harboring Wilms' tumor gene (WT1y) and assess the cytotoxic T lymphocyte (CTL) response specific to the DNA vaccine of WT1y product in Balb/c mice and in vitro cultured cells.

METHODS

Synthesized WT1y gene (321 bp including HLA-A*2402 anchoring residue) was cloned into the eukaryotic vector to construct the plasmid pCDNA3.1(+)/WT1y. WT1-specific antibody was detected in mouse serum by ELISA, and T lymphocyte proliferation was detected by flow cytometry. The CTL response was detected by co-culture of the murine spleen cells with the tumor cells.

RESULTS

The recombinant plasmid was confirmed using DNA sequencing. WT1-specific antibodies were detected in the serum of immunized mice, which showed significantly greater T lymphocyte proliferation than the control group (Plt;0.01). The CTLs resulted in specific lysis of WT1-expressing murine tumor cells.

CONCLUSION

Using HBVC as the vector for WT1y gene, wenave obtained the virus-like particles that induce high cellular immune response, which shed light on a new approach for treatment of Wilms' tumor.

[Immunotherapy targeting the Wilms' tumor 1 gene product for patients with malignant brain tumors]

In this paper, we review the current status of immunotherapy targeting Wilms' tumor 1 (WT1) peptide in malignant brain tumors as well as in other hematological and solid malignancies. WT1 is expressed in various kinds of malignancies, and is involved in oncogenesis. The titers of antibodies against WT1 and the frequency of WT1-specific cytotoxic T lymphocytes (CTLs) were higher in cancer patients than in healthy donors, indicating that WT1 protein has immunogenic function. These findings provided us with a rationale for developing cancer immunotherapy that targets the WT1 peptide. Clinical trials of the WT1 peptide vaccination were initiated, and definite immunological and clinical responses were observed. The disease control rate of 57.1% was obtained especially in the case of recurrent glioblastomas, with a median progression-free survival period of 20.0 weeks and progression-free survival rate at 6 months of 33.3%. The trial showed that WT1 vaccination for malignant gliomas, which is generally believed to be an intractable disease, was safe and elicited a favorable clinical response. Further clinical studies of WT1 vaccination in patients with malignant gliomas as well as other cancers are warranted. An enhancement of the efficacy of WT1 vaccination can be expected with a combined treatment using the WT1-specific helper peptide or anti-cancer chemotherapeutic agents. Administration of WT1 vaccination along with other therapeutic modalities during initial treatment or in the case showing minimal residual disease may prolong the survival time of the cancer patients.

Induction of Wilms' tumor protein (WT1)-specific antitumor immunity using a truncated WT1-expressing adenovirus vaccine

PURPOSE

Wilms' tumor protein (WT1) is overexpressed in most leukemias and many solid tumors and is a promising target for tumor immunotherapy. WT1 peptide-based cancer vaccines have been reported but have limited application due to HLA restriction of the peptides. We sought to vaccinate using adenoviral (Ad) vectors encoding tumor-associated antigens such as WT1 that can stimulate tumor-associated antigen-specific immunity across a broad array of HLA types and multiple class I and class II epitopes.

EXPERIMENTAL DESIGN

We developed a novel Ad vector encoding a truncated version of WT1 (Ad-tWT1) lacking the highly conserved COOH terminus zinc finger domains and tested its ability to stimulate WT1-specific immune responses and antitumor immunity in two murine models of WT1-expressing tumors.

RESULTS

Despite encoding a transcription factor, we found that Ad-tWT1-transduced murine and human dendritic cells showed cytoplasmic expression of the truncated WT1 protein. In addition, vaccination of C57BL/6 mice with Ad-tWT1 generated WT1-specific cell-mediated and humoral immune responses and conferred protection against challenge with the leukemia cell line, mWT1-C1498. Moreover, in a tumor therapy model, Ad-tWT1 vaccination of TRAMP-C2 tumor-bearing mice significantly suppressed tumor growth.

CONCLUSIONS

This is the first report of a WT1-encoding Ad vector that is capable of inducing effective immunity against WT1-expressing malignancies. Based on these findings, Ad-tWT1 warrants investigation in human clinical trials to evaluate its applications as a vaccine for patients with WT1-expressing cancers.

Characterizing and optimizing immune responses to leukaemia antigens after allogeneic stem cell transplantation

Allogeneic stem cell transplantation remains a curative treatment for haematological malignancies resistant to other treatment approaches through the unique graft-versus-leukaemia effect (GvL). However, the lack of specificity of this response results in the targeting of normal tissue, and the morbidity and mortality associated with graft-versus-host disease (GvHD). Further improvements in exploiting the GvL effect to prevent relapse in high-risk leukaemias while minimizing toxicity have focused on the use of targeted anti-leukaemic immunotherapy. These strategies include the use of vaccines against minor histocompatibility antigens (HA-1, HA-2 and H-Y) and leukaemia-specific antigens (proteinase 3, Wilms' tumour 1 and BCR-ABL), and the adoptive transfer of leukaemia-specific T cells. The unique post-transplant milieu, which is characterized by lymphopenia, regulatory T-cell depletion and the release of growth factors, offers the opportunity to promote the expansion of engrafted T cells and enhance the specific GvL response. Techniques to reduce regulatory T-cell control over T-cell responses to leukaemia antigens could further enhance GvL reactivity. Finally, these approaches to increase GvL effects would be facilitated by transplant approaches to deplete GvHD alloresponses selectively while preserving GvL reactivity.

Potential of dendritic-cell immunotherapy for relapse after allogeneic hematopoietic stem cell transplantation, shown by WT1 peptide- and keyhole-limpet-hemocyanin-pulsed, donor-derived dendritic-cell vaccine for acute myeloid leukemia

Induction of leukemia-specific immune responses is a promising treatment for acute myeloid leukemia. A 58-year-old woman received Wilms' tumor 1 (WT1) peptide- and keyhole limpet hemocyanin (KLH)-pulsed, donor-derived dendritic cell (DC) vaccination for AML relapse after allogeneic stem cell transplantation. The vaccination induced immune responses to the naive antigen KLH, whereas definitive immune responses to WT1 were not detected. Leukemia gradually progressed despite of vaccination. This study indicates that DC vaccination can induce an antigen-specific immune response in a patient after allogeneic stem cell transplantation, thus representing a viable strategy to induce antigen-specific immune responses in such patients.

Potent CTL induction by a whole cell pertussis vaccine in anti-tumor peptide immunotherapy

Promising yet limited clinical responses have been reported for peptide based immunotherapy against tumors. In order to induce more potent cytolytic CD8 T cell responses, we investigated the use of Bordetella pertussis vaccine as an adjuvant for peptide immunization. A whole cell (Wc) vaccine has been known to induce a Th1 biased immune response while an acellular (Ac) vaccine tends to induce that of the Th2 type. Natural infection by B. pertussis helps to maintain a robust Th1 memory in the host population. To examine the adjuvant activity of the pertussis vaccine, we immunized mice with an ovalbumin peptide as a model tumor antigen, and monitored the development of anti-tumor activities. The addition of either the Ac or the Wc vaccine helped expand the specific CD8 T cells. However, there was a marked difference in the induced cytolytic activity where the Wc vaccine was superior to the Ac. The Wc vaccine was also more effective in inducing in vivo tumor rejection. The adjuvant activity was not only effective against ovalbumin, but was also evident when an endogenous tumor antigen, Wilms' tumor 1 gene product, was targeted. These results indicate that, although the Wc vaccine does not share the same antigen specificity with tumor cells, it can aid in the development of highly cytolytic CD8 T cells as an adjuvant at the site of peptide immunization.

Leukemia-associated antigen-specific T-cell responses following combined PR1 and WT1 peptide vaccination in patients with myeloid malignancies

We describe the safety and immunogenicity of a combined vaccine of 2 leukemia-associated antigenic peptides, PR1 and WT1. Eight patients with myeloid malignancies received one subcutaneous dose each of PR1 and WT1 vaccines in Montanide adjuvant, with granulocyte-macrophage colony-stimulating factor. Patients were reviewed weekly for 4 weeks to monitor toxicity and immunologic responses. Toxicity was limited to grades 1 to 2. Using peptide/HLA-A 0201 tetramers and intracellular interferon-gamma staining, CD8(+) T cells against PR1 or WT1 were detected in 8 of 8 patients after a single vaccination. To monitor the kinetics of vaccine-induced CD8(+) T-cell responses and disease regression after vaccination, absolute PR1 and WT1(+)CD8(+) T-cell numbers and WT1 expression were studied weekly after vaccination. Responses occurred as early as 1 week after vaccination. After vaccination, the emergence of PR1 or WT1(+)CD8(+) T cells was associated with a decrease in WT1 mRNA expression as a marker of minimal residual disease, suggesting a vaccine-driven antileukemia effect. Conversely, loss of response was associated with reappearance of WT1 transcripts (P < .01). This is the first demonstration that a combined PR1 and WT1 vaccine is immunogenic. These results support further studies of combination immunization strategies in leukemia patients.

WT1-specific T cell receptor gene therapy: improving TCR function in transduced T cells

Adoptive transfer of antigen-specific T lymphocytes is an attractive form of immunotherapy for haematological malignancies and cancer. The difficulty of isolating antigen-specific T lymphocytes for individual patients limits the more widespread use of adoptive T cell therapy. The demonstration that cloned T cell receptor (TCR) genes can be used to produce T lymphocyte populations of desired specificity offers new opportunities for antigen-specific T cell therapy. The first trial in humans demonstrated that TCR gene-modified T cells persisted for an extended time period and reduced tumor burden in some patients. The WT1 protein is an attractive target for immunotherapy of leukemia and solid cancer since elevated expression has been demonstrated in AML, CML, MDS and in breast, colon and ovarian cancer. In the past, we have isolated high avidity CTL specific for a WT1-derived peptide presented by HLA-A2 and cloned the TCR alpha and beta genes of a WT1-specific CTL line. The genes were inserted into retroviral vectors for transduction of human peripheral blood T lymphocytes of leukemia patients and normal donors. The treatment of leukemia-bearing NOD/SCID mice with T cells transduced with the WT1-specific TCR eliminated leukemia cells in the bone marrow of most mice, while treatment with T cells transduced with a TCR of irrelevant specificity did not diminish the leukemia burden. In order to improve the safety and efficacy of TCR gene therapy, we have developed lentiviral TCR gene transfer. In addition, we employed strategies to enhance TCR expression while avoiding TCR mis-pairing. It may be possible to generate dominant TCR constructs that can suppress the expression of the endogenous TCR on the surface of transduced T cells. The development of new TCR gene constructs holds great promise for the safe and effective delivery of TCR gene therapy for the treatment of malignancies.

Clinical and immunologic responses to very low-dose vaccination with WT1 peptide (5 microg/body) in a patient with chronic myelomonocytic leukemia

The wild-type Wilms tumor gene, WT1, is overexpressed in myelodysplastic syndrome (MDS) as well as acute myeloid leukemia. In a phase I clinical trial of biweekly vaccination with HLA-A*2402-restricted WT1 peptide for these malignancies, 2 patients with MDS developed severe leukocytopenia in association with a reduction in leukemic blast cells and levels of WT1 messenger RNA (mRNA) after only a single vaccination with 0.3 mg of WT1 peptide. These results indicated that the WT1-specific cytotoxic T-lymphocytes (CTLs) elicited by WT1 vaccination eradicated the WT1-expressing transformed stem or progenitor cells and that MDS patients with little normal hematopoiesis required a new strategy of WT1 vaccination to avoid severe leukocytopenia. We describe the first trial for a 57-year-old male patient with chronic myelomonocytic leukemia who was vaccinated biweekly with a small quantity (5 microg/body) of WT1 peptide. After the start of vaccination, the leukocyte and monocyte counts (13,780/microL and 1930/microL, respectively) gradually decreased to within the normal range in association with a reduction in the WT1 mRNA level. Simultaneously, the percentage of WT1-specific CTLs as measured by the HLA-WT1 tetramer assay increased. This case demonstrates for the first time that vaccination with as little as 5 microg of WT1 peptide can induce WT1-specific immune responses and resultant clinical responses.

Peptide Epitopes from the Wilms' Tumor 1 Oncoprotein Stimulate CD4+and CD8+T Cells That Recognize and Kill Human Malignant Mesothelioma Tumor Cells

PURPOSE

Wilms' tumor 1 protein (WT1), a transcription factor overexpressed in malignant mesothelioma, leukemias, and other solid tumors, is an ideal target for immunotherapy. WT1 class I peptide epitopes that were identified and shown to stimulate CD8(+) T cells are being tested as vaccine candidates in several clinical trials. The induction and maintenance of a robust memory CD8(+) cytotoxic T-cell response requires CD4(+) T-cell help.

EXPERIMENTAL DESIGN

Three HLA class II peptide epitopes of WT1 with high predictive affinities to multiple HLA-DRB1 molecules were identified using the SYFPEITHI algorithm. Due to the highly polymorphic nature of the HLA class II alleles, such reactivity is critical in the development of a broadly useful therapeutic. One of the WT1 CD4(+) peptide epitopes, 122-140, comprises a previously identified CD8(+) peptide epitope (126-134). By mutating residue 126 from an arginine to a tyrosine, we embedded a synthetic immunogenic analogue CD8(+) epitope (126-134) inside the longer peptide (122-140). This analogue was previously designed to improve immunogenicity and induce a potent CD8(+) response.

RESULTS

WT1 peptides 328-349 and 423-441 are able to stimulate a peptide-specific CD4(+) response that can recognize WT1(+) tumor cells in multiple HLA-DRB1 settings as determined by IFN-gamma enzyme-linked immunospot assays. The mutated WT1 peptide epitope 122-140 is able to induce CD4(+) and cytotoxic CD8(+) WT1-specific T-cell responses that can recognize the native WT1 epitopes on the surface of human WT1(+) cancer cells. Cross-priming experiments showed that antigen-presenting cells pulsed with either mesothelioma or leukemia tumor lysates can process and present each of the CD4(+) peptides identified.

CONCLUSIONS

These studies provide the rationale for using the WT1 CD4(+) peptides in conjunction with CD8(+) peptide epitopes to vaccinate patients with WT1-expressing cancers.

Activation-induced expression of CD137 permits detection, isolation, and expansion of the full repertoire of CD8+ T cells responding to antigen without requiring knowledge of epitope specificities

CD137 is a member of the TNFR-family with costimulatory function. Here we show that it also has many favorable characteristics as a surrogate marker for antigen-specific activation of human CD8(+) T cells. Although undetectable on unstimulated CD8(+) T cells, it is uniformly up-regulated 24 hours after stimulation on virtually all responding cells regardless of differentiation stage or profile of cytokine secretion, which circumvents limitations of current surrogate markers for defining the repertoire of responding cells based on only individual functions. Antibody-labeled responding CD137(+) cells can be easily and efficiently isolated by flow sorting or magnetic beads to substantially enrich antigen-specific T cells. To test this approach for epitope discovery, we examined in vitro priming of naive T cells from healthy donors to Wilms tumor antigen 1 (WT1), a protein overexpressed in various malignancies. Two overlapping pentadecamers were identified as immunogenic, and further analysis defined WT1((286-293)) as the minimal amino acid sequence and HLA-Cw07 as the HLA restriction element. In conclusion, this approach appears to be an efficient and sensitive in vitro technique to rapidly identify and isolate antigen-specific CD8(+) T cells present at low frequencies and displaying heterogeneous functional profiles, and does not require prior knowledge of the specific epitopes recognized or the HLA-restricting elements.

WT1 peptide cancer vaccine for patients with hematopoietic malignancies and solid cancers

Wild-type Wilms' tumor gene WT1 is expressed at a high level in hematopoietic malignancies including acute leukemia, chronic myelogenous leukemia, and myelodysplastic syndromes, as well as in various kinds of solid cancers. Human cytotoxic T lymphocytes (CTLs), which could specifically lyse WT1-expressing tumor cells with HLA class I restriction, were generated in vitro. It was also demonstrated that mice immunized with the WT1 peptide rejected challenges by WT1-expressing cancer cells and survived with no signs of autoaggression to normal organs that physiologically expressed WT1. Furthermore, we and others detected IgM and IgG WT1 antibodies in patients with hematopoietic malignancies, indicating that the WT1 protein was highly immunogenic, and that immunoglobulin class-switch-inducing, WT1-specific, cellular immune responses were elicited in these patients. CD8⁺ WT1-specific CTLs were also detected in peripheral blood or tumor-draining lymph nodes of cancer patients. These results provided us with the rationale for elicitation of CTL responses targeting the WT1 product for cancer immunotherapy. On the basis of these findings, we performed a phase I clinical trial of a WT1 peptide cancer vaccine for the patients with malignant neoplasms. These results strongly suggested that the WT1 peptide cancer vaccine had efficacy in the clinical setting because clinical responses, including reduction of leukemic blast cells or regression of tumor masses, were observed after the WT1 vaccination in patients with hematopoietic malignancies or solid cancers. The power of a tumor-associated-antigen (TAA)-derived cancer vaccine may be enhanced in combination with stronger adjuvants, helper peptide, molecular-target-based drugs, or some chemotherapy drugs, such as gemcitabine, which has been revealed to suppress regulartory T-cell function. In contrast, reduction of WT1 peptide dose may be needed for the treatment of patients with hematological stem cell diseases, because rapid and strong destruction of malignant cell-sustained hematopoiesis before recovery of normal hematopoiesis may lead to pancytopenia in these patients.

The role of the Wilms tumour gene (WT1) in normal and malignant haematopoiesis

In addition to its loss playing a pivotal role in the development of a childhood kidney malignancy, the Wilms tumour 1 gene (WT1) has emerged as an important factor in normal and malignant haematopoiesis. Preferentially expressed in CD34+ haematopoietic progenitors and down-regulated in more-differentiated cells, the WT1 transcription factor has been implicated in regulation of apoptosis, proliferation and differentiation. Putative target genes, such as BCL2, MYC, A1 and cyclin E, may cooperate with WT1 to modulate cell growth. However, the effects of WT1 on target gene expression appear to be isoform-specific. Certain WT1 isoforms are over-represented in leukaemia, but the exact mechanisms underlying the role of WT1 in transformation remain unclear. The ubiquity of WT1 in haematological malignancies has led to efforts to exploit it as a marker for minimal residual disease and as a prognostic factor, with conflicting results. In vitro killing of tumour cells by WT1-specific CD8+ cytotoxic T lymphocytes facilitated design of Phase I vaccine trials that showed clinical regression of WT1-positive tumours. Alternative methods employing WT1-specific immunotherapy are being investigated and might ultimately be used to optimise multimodal therapy of haematological malignancies.

Immunotherapeutic strategies in chronic myeloid leukemia

Several clinical observations demonstrate that immunologic effects are important in chronic myeloid leukemia (CML). The characteristic BCR-ABL fusion protein is a leukemia-specific antigen, and it has therefore received much immunologic attention, especially regarding the amino acid sequences that span the e14a2 junction. Other attractive targets are the Wilms' tumor 1 antigen and the PR1 epitope from proteinase 3, a granule protein overexpressed in CML. Imatinib may modulate several components of the immune response, although the clinical relevance of this effect is uncertain. In clinical trials, peptide vaccination appears safe and undoubtedly produces clinical effects, but randomized trials are now required to see if these are distinct from the effects of other concurrent therapy. These trials will be difficult to orchestrate in the competitive environment of novel therapies for CML.

Identification and characterization of a WT1 (Wilms Tumor Gene) protein-derived HLA-DRB1*0405-restricted 16-mer helper peptide that promotes the induction and activation of WT1-specific cytotoxic T lymphocytes

Effective tumor vaccine may be required to induce both cytotoxic T lymphocyte (CTL) and CD4+ helper T-cell responses against tumor-associated antigens. CD4+ helper T cells that recognize HLA class II-restricted epitopes play a central role in the initiation and maintenance of antitumor immune responses. The Wilms tumor gene WT1 is overexpressed in both leukemias and solid tumors, and the WT1 protein was demonstrated to be an attractive target antigen for cancer immunotherapy. In this study, we identified a WT1 protein-derived 16-mer peptide, WT1(332)(KRYFKLSHLQMHSRKH), which was restricted with HLA-DRB1*0405, one of the most common HLA class II types in Japanese, as a helper epitope that could elicit WT1-specific CD4+ T-cell responses. We established a WT1(332)-specific CD4+ helper T-cell clone (E04.1), which could respond to both HLA-DRB1*0405-positive, WT1-expressing transformed hematopoietic cells and autologous dendritic cells pulsed with apoptosis-induced WT1-expressing cells, indicating that the WT1(332) was a naturally processed helper epitope. Stimulation of peripheral blood mononuclear cells with both the CTL epitope (WT1(235)) and the helper epitope (WT1(332)) in the presence of WT1(332)-specific TH1-type CD4+ T cell clone strikingly enhanced the induction and the functional activity of WT1(235)-specific CTLs compared with that of peripheral blood mononuclear cells with the WT1(235) alone. These results indicated that a helper epitope, WT1(332) should be useful for improvement of the efficacy of CTL epitope-based cancer vaccine targeting WT1 in the clinical setting.

Dendritic Cell Immunization Induces Nonprotective WT1-specific CTL Responses in Mouse

In the present article we describe the immunogenicity in the mouse of 2 epitopes from the tumor-associated antigen Wilms tumor 1 antigen (WT1). The newly described K-restricted pWT330 epitope stimulates high-avidity allo-major histocompatibility complex restricted cytotoxic T lymphocyte (CTL) capable of killing WT1-expressing tumor cell lines. The epitope pWT126 has been previously described as a D-restricted CTL epitope. Both epitopes are weakly immunogenic as immunization with incomplete Freund adjuvant induced poor CTL responses. In contrast, when coated onto dendritic cells (DCs) both peptides readily induced CTL responses. However, these peptide-specific CTL were of low avidity and unable to recognize WT1-expressing tumor cells in vitro and to protect against tumor challenge in vivo. In contrast, vaccination with DCs coated with peptides derived from the nonself antigen ovalbumin (OVA) induced CTL that recognized OVA-expressing tumor cells and protected against tumor growth in vivo. These data show that although DC vaccination readily stimulated CTL against WT1 peptides, these CTL did not display antitumor activity in vitro and in vivo. This suggests that tolerance to the 2 WT1 epitopes interferes with the generation of protective CTL immunity in mice.

Review of current knowledge on HPV vaccination: an appendix to the European Guidelines for Quality Assurance in Cervical Cancer Screening

The recognition of a strong etiological relationship between infection with high-risk human papillomavirusses and cervical cancer has prompted research to develop and evaluate prophylactic and therapeutic vaccines. One prophylactic quadrivalent vaccine using L1 virus-like particles (VLP) of HPV 6, 11, 16 and 18 is available on the European market since the end of 2006 and it is expected that a second bivalent vaccine containing VLPs of HPV16 and HPV18 will become available in 2007. Each year, HPV16 and HPV18 cause approximately 43,000 cases of cervical cancer in the European continent. Results from the phase-IIb and III trials published thus far indicate that the L1 VLP HPV vaccine is safe and well-tolerated. It offers HPV-naive women a very high level of protection against HPV persistent infection and cervical intra-epithelial lesions associated with the types included in the vaccine. HPV vaccination should be offered to girls before onset of sexual activity. While prophylactic vaccination is likely to provide important future health gains, cervical screening will need to be continued for the whole generation of women that is already infected with the HPV types included in the vaccine. Phase IV studies are needed to demonstrate protection against cervical cancer and to verify duration of protection, occurrence of replacement by non-vaccine types and to define future policies for screening of vaccinated cohorts. The European Guidelines on Quality Assurance for Cervical Cancer Screening provides guidance for secondary prevention by detection and management of precursors lesions of the cervix. The purpose of the appendix on vaccination is to present current knowledge. Developing guidelines for future use of HPV vaccines in Europe, is the object of a new grant offered by the European Commission.

WT1, monoclonal CEA, TTF1, and CA125 antibodies in the differential diagnosis of lung, breast, and ovarian adenocarcinomas in serous effusions

The distinction between metastatic adenocarcinomas of lung (LAC), breast (BAC), and ovary (OAC) in serous effusions can be very difficult since they all can present as tight cell clusters. This is particularly challenging when the malignant effusion is the patient's initial presentation or when the patient has a history of more than one primary. The aim of this study is to evaluate the usefulness of WT1, monoclonal CEA (mCEA), TTF1, and CA125 antibodies in the differential diagnosis of metastatic adenocarcinoma from the lung, breast and ovary in serous effusions. Forty-six samples of serous effusions with their corresponding cell blocks were retrieved from our hospital computer system, including 13 BACs, 13 LACs, and 20 OACs. The diagnoses were confirmed by the surgical resection. Formalin-fixed and paraffin-embedded cell block sections were immunostained for WT1, mCEA, TTF1, and CA125. Two observers blindly reviewed the immunostained slides without knowledge of the previous clinical or histologic diagnoses. The staining intensity was graded semiquantitatively as negative, 0; weak, 1+; moderate, 2+; and strong, 3+. The percentage of positively staining cells was estimated. The distribution patterns of reactivity for WT1 and TTF1 were recorded as nuclear, and mCEA and CA125 as membranous stain. Metastatic OACs showed positive immunoreactivity to WT1 in 19/20 (95%) cases, CA125 in 20/20 (100%), and all showed negative reaction for both mCEA (0/20, 0%) and TTF1 (0/20, 0%). BAC showed positive reaction in 6/13 (46%) cases to CA125 and mCEA. Staining pattern was diffuse for CA125 and focal for mCEA. Only 2/13 (15%) were positive for WT1, while all of 13 BAC cases (0/13, 0%) were negative for TTF1. LAC showed positive immunoreactivity for TTF1 in 9/13 (69%) with a characteristic nuclear staining pattern, but only 3/13 (23%) were focally stained for WT1. In addition, 8/13 (62%) of LAC cases were positive for both CA125 and mCEA. Our results demonstrate that the WT1 stain is specific for metastatic carcinoma of ovarian primary, showing a high sensitivity. In addition, CA125 stain is very sensitive for OACs, but could be positive in about a half of LAC and BAC cases. An immunostaining pattern of positive mCEA as well as negative WT1 rules out OACs, raising the possibility of LACs and BACs. A positive TTF1 staining supports the diagnosis of metastatic carcinoma originating from lung rather than breast, while a negative TTF1 favors the diagnosis of a breast primary. Immunohistochemical studies with WT1, TTF1, and mCEA antibodies are useful in the differential diagnosis of metastatic adenocarcinomas of lung, breast, and ovary.