Clonal diversity of the T-cell population responding to a dominant HLA-A2 epitope of HER-2/neu after active immunization in an ovarian cancer patient

Multiple vaccinations: friend or foe

Few immunotherapists would accept the concept of a single vaccination inducing a therapeutic anticancer immune response in a patient with advanced cancer. But what is the evidence to support the "more-is-better" approach of multiple vaccinations? Because we are unaware of trials comparing the effect of a single vaccine versus multiple vaccinations on patient outcome, we considered that an anticancer immune response might provide a surrogate measure of the effectiveness of vaccination strategies. Because few large trials include immunologic monitoring, the majority of information is gleaned from smaller trials in which an evaluation of immune responses to vaccine or tumor, before and at 1 or more times following the first vaccine, was performed. In some studies, there is convincing evidence that repeated administration of a specific vaccine can augment the immune response to antigens contained in the vaccine. In other settings, multiple vaccinations can significantly reduce the immune response to 1 or more targets. Results from 3 large adjuvant vaccine studies support the potential detrimental effect of multiple vaccinations as clinical outcomes in the control arms were significantly better than that for treatment groups. Recent research has provided insights into mechanisms that are likely responsible for the reduced responses in the studies noted above, but supporting evidence from clinical specimens is generally lacking. Interpretation of these results is further complicated by the possibility that the dominant immune response may evolve to recognize epitopes not present in the vaccine. Nonetheless, the Food and Drug Administration approval of the first therapeutic cancer vaccine and recent developments from preclinical models and clinical trials provide a substantial basis for optimism and a critical evaluation of cancer vaccine strategies.

The impact of T-cell immunity on ovarian cancer outcomes

Ovarian cancer remains a challenging disease for which improved treatments are urgently needed. Most patients present with advanced disease that is highly responsive to surgery combined with platinum- and taxane-based chemotherapy, with a state of minimal residual disease being achieved in many cases. However, chemotherapy-resistant recurrent tumors typically appear within 1-5 years and are ultimately fatal. Recently, several groups have shown that ovarian tumors are often infiltrated by activated T cells at the time of diagnosis, and patients with dense infiltrates of CD3+CD8+ T cells experience unexpectedly favorable progression-free and overall survival. Other cell types in the immune infiltrate oppose anti-tumor immunity, including CD4+CD25+FoxP3+ regulatory T cells, CD8+ regulatory T cells, macrophages, and dendritic cells. The composition of immune infiltrates is shaped by the expression of cytokines, chemokines, antigens, major histocompatibility complex molecules, and costimulatory molecules. The relationship between these various immunological factors is reviewed here with a strong emphasis on outcomes data so as to create a knowledge base that is well grounded in clinical reality. With improved understanding of the functional properties of natural CD8+ T-cell responses to ovarian cancer, there is great potential to improve clinical outcomes by amplifying host immunity.

VRP immunotherapy targeting neu: treatment efficacy and evidence for immunoediting in a stringent rat mammary tumor model

The ability to overcome intrinsic tolerance to a strict "self" tumor-associated antigen (TAA) and successfully treat pre-existing tumor is the most stringent test for anti-tumor immunotherapeutic strategies. Although this capacity has been demonstrated in various models using complicated strategies that may not be readily translated into the clinical arena, straightforward antigen-specific immunotherapeutic strategies in the most stringent models of common epithelial cancers have largely failed to meet this standard. We employed an immunotherapeutic strategy using an alphavirus-based, virus-like replicon particle (VRP), which has in vivo tropism for dendritic cells, to elicit immune responses to the non-mutated TAA rat neu in an aggressive rat mammary tumor model. Using this VRP-based immunotherapeutic strategy targeting a single TAA, we generated effective anti-tumor immunity in the setting of pre-existing tumor resulting in the cure of 36% of rats over multiple experiments, P = 0.002. We also observed down-regulation of rat neu expression in tumors that showed initial responses followed by tumor escape with resumption of rapid tumor growth. These responses were accompanied by significant anti-tumor proliferative responses and CD8+ cellular tumor infiltrates, all of which were restricted to animals receiving the anti-neu immunotherapy. Together these data, obtained in a stringent "self" TAA model, indicate that the VRP-based antigen-specific immunotherapy elicits sufficiently potent immune responses to exert immunologic pressure, selection, and editing of the growing tumors, thus supporting the activity of this straightforward immunotherapy and suggesting that it is a promising platform upon which to build even more potent strategies.

Interferon-gamma renders tumors that express low levels of Her-2/neu sensitive to cytotoxic T cells

Her-2/neu is a tumor-associated antigen that has been targeted with both antibodies and cytotoxic T lymphocytes (CTL). Despite the isolation of Her-2/neu-reactive CTL in vaccinated patients, their therapeutic use has been limited by the observation that they often do not robustly recognize Her-2/neu(+) tumors. We sought to determine the mechanism for this escape using Ag201P and Ag201M cells, which are murine osteosarcoma tumor lines that express a functional HLA-A2/K(b) molecule. We now demonstrate that Ag201P and Ag201M express low levels of murine Her-2/neu, and that Ag201M was modestly and inconsistently recognized by an HLA-A2-restricted, Her-2/neu-reactive human CTL clone. In order to determine whether inefficient antigen processing might account for the weak recognition, COS-A2 cells were transfected with a short Her-2/neu minigene coding for the immunodominant Her-2/neu:369 epitope that did not require antigen processing or a long Her-2/neu minigene that did require antigen processing. Her-2/neu-reactive CTL clones only recognized COS-A2 cells transfected with the short minigene, indicating that lack of proper antigen processing could be responsible for the poor recognition of target cells. To confirm these results, it was demonstrated that following treatment with interferon-gamma, both Ag201P and Ag201M robustly and consistently stimulated the CTL clones. Furthermore, CTL clone recognition was enhanced following interferon-gamma treatment using another murine tumor line that expressed low levels of Her-2/neu (B16-A2/K(b)). The enhanced recognition of Ag201P and Ag201M in the presence of interferon-gamma was not due to an upregulation of Her-2/neu protein expression. Collectively, these results suggest that inefficient antigen processing of Her-2/neu can contribute to the lack of tumor recognition by CTL. These results also suggest that even tissues that express low levels of Her-2/neu might become CTL targets under conditions in which antigen processing is enhanced.

Identification of HLA-DQα and -DRβ Residues Associated With Susceptibility and Protection to Epithelial Ovarian Cancer

Substantial evidence has been accumulated suggesting that T cells in patients with epithelial ovarian carcinoma (EOC) exhibit an antigen-driven immune response directed against the tumor cells. In the context of human leukocyte antigen (HLA), this suggests its possible involvement in the disease. Therefore, we examined the distribution of the HLA-DRB1*, -DQA1*, and -DQB1* alleles in 47 patients with EOC and 67 healthy Caucasian women. The frequency of D(70) and E(71) polymorphic residues of the DRB1 alleles was significantly reduced in EOC patients versus controls (pD(70)E(71) = 0.009), suggesting a protective role against the disease. The DQalpha residues R(52) and Y(11)R(55) were increased in the patients (p = 0.008 and 0.012, respectively). Because residues 11 and 55 participate in the formation of pocket 1, they may be functionally important amino acid positions that influence disease susceptibility. The frequency of the DQalpha susceptibility epitope (R(52)Y(11)R(55)) among the DRbetaD(70)E(71)-positive EOC patients was increased when compared with DRbetaD(70)E(71)-positive controls (EOC, 100%; control, 52%; p = 0.028). Among individuals without the DQalpha susceptibility epitope, the distribution of DRbetaD(70)E(71)-positive cases was significantly different between EOC patients and controls (EOC, 0%; control, 60%; p = 0.039). Therefore, it appears that the presence of DQalpha susceptibility elements overrides the protective effect of the DRbetaD(70)E(71) epitope and suggests an interactive relationship between DRbeta and DQalpha epitopes that may be of importance for disease susceptibility. Because positions DRbeta 70,71 and DQalpha 52 have been implicated in immunologic diseases, it is likely that besides being critical for T-cell recognition, they may also play a role in T-cell development and acquisition of the T-cell repertoire.

Identification of CD19 and CD20 Peptides for Induction of Antigen-Specific CTLs against B-Cell Malignancies

The purpose of these studies was to develop immunogenic peptides derived from the CD19 and CD20 self-antigens for the induction of antigen-specific CTLs against B-cell malignancies. A total of seven peptides were designed and examined for their HLA-A2.1 affinity and immunogenicity. Of these peptides, we identified two highly immunogenic HLA-A2.1-specific peptides, CD19(150-158) (KLMSPKLYV) and CD20(188-196) (SLFLGILSV), which were capable of inducing peptide-specific CTLs. The CTLs displayed HLA-A2.1-restricted and antigen-specific cytotoxicity against Burkitt's lymphoma, chronic B cell leukemia, and multiple myeloma cell lines. The CD19 or CD20 peptide-specific CTL cytotoxicity was confirmed using HLA-A2.1(+) T2 cells presenting the appropriate peptide. No cytotoxic activity was observed against T2 cells presenting the irrelevant MAGE-3 peptide or T2 cells alone. In addition, the CTLs displayed a significant (P < 0.05) increase in cell proliferation and IFN-gamma secretion (>830 ng/mL) following restimulation with HLA-A2.1(+)/CD19(+)/CD20(+) tumor cells. The CTLs also displayed a distinct phenotype consisting of a high percentage of CD69(+)/CD45RO(+) and a low percentage of CD45RA(+)/CCR7(+) CD4(+) or CD8(+) T cells characteristic of effector memory cell population. Cyclic guanosine 3',5'-monophosphate culture conditions using serum-free AIM-V medium containing human AB serum, recombinant human interleukin 2 (Proleukin) and CD3/CD28 Dynabeads were developed resulting in a 35-fold expansion of CD20 peptide-specific CTLs. The expanded CD20-CTLs retained their cytotoxic activity (28-49%) against the Burkitt's lymphoma cell line. In conclusion, we report here on the identification of novel immunogenic CD19(150-158) (KLMSPKLYV) and CD20(188-196) (SLFLGILSV) peptides that have immunotherapeutic potentials as peptide vaccines or targeted T-cell therapies for treating B-cell malignancies.

Vaccination with Ep-CAM protein or anti-idiotypic antibody induces Th1-biased response against MHC class I- and II-restricted Ep-CAM epitopes in colorectal carcinoma patients

PURPOSE

The tumor-associated antigen Ep-CAM (epithelial cell adhesion molecule) is overexpressed in colorectal carcinoma (CRC). The aim of the present study was to evaluate and compare the safety and immunogenicity of a recombinant Ep-CAM protein and a human anti-idiotypic antibody (anti-Id) mimicking Ep-CAM.

EXPERIMENTAL DESIGN

Patients with resected American Joint Committee on Cancer stages II-IV CRC without remaining macroscopic disease received intradermal/subcutaneous injections of Ep-CAM (400 microg/dose; n = 7) or anti-Id (500 microg/dose; n = 6) at weeks 0, 2, and 6 in combination with granulocyte macrophage colony-stimulating factor (75 microg/day, for 4 consecutive days).

RESULTS

Adverse reactions were mild (grade I-II). All patients immunized with the Ep-CAM protein produced Ep-CAM-specific IgG antibodies, predominantly IgG1 and IgG3 subclasses, whereas no humoral response was induced by the anti-Id vaccine. All patients, with one exception in each group, mounted an Ep-CAM-specific proliferative T-cell response. The immune response was more rapid, potent, and protracted after Ep-CAM in comparison with anti-Id vaccination. Interferon-gamma-secreting cells (ELISPOT) were detected in both immunization groups against the Ep-CAM protein as well as various Ep-CAM-derived MHC class I- and II-restricted peptides. Flow cytometry analysis showed that Ep-CAM-specific interferon-gamma- and perforin-producing cells predominantly resided within CD8(+)CD56- and CD8(dim)CD56+ T cells.

CONCLUSIONS

Ep-CAM protein in combination with granulocyte macrophage colony-stimulating factor induced a long-lasting, Th1-biased humoral and cellular immune response compared with anti-Id. Ep-CAM-specific T cells and natural killer-like T cells responding in a MHC class I- and II-restricted manner were also induced. Vaccination with Ep-CAM protein may warrant further investigation as a novel therapeutic approach to CRC.

Identification of novel CD33 antigen-specific peptides for the generation of cytotoxic T lymphocytes against acute myeloid leukemia

Identification of immunogenic peptides for the generation of cytotoxic T lymphocytes (CTLs) may lead to the development of novel cellular therapies to treat disease relapse in acute myeloid leukemia (AML) patients. The objective of these studies was to evaluate the ability of unique HLA-A2.1-specific nonameric peptides derived from CD33 antigen to generate AML-specific CTLs ex vivo. We present data here on the identification of an immunogeneic HLA-A2.1-specific CD33(65-73) peptide (AIISGDSPV) that was capable of inducing CTLs targeted to AML cells. The CD33-CTLs displayed HLA-A2.1-restricted cytotoxicity against both mononuclear cells from AML patients and the AML cell line. The peptide- as well as AML cell-specificity of CD33-CTLs was demonstrated and the secretion of IFN-gamma by the CTLs was detected in response to CD33(65-73) peptide stimulation. The cultures contained a distinct CD33(65-73) peptide-tetramer(+)/CD8(+) population. Alteration of the native CD33(65-73) peptide at the first amino acid residue from alanine (A) to tyrosine (Y) enhanced the HLA-A2.1 affinity/stability of the modified CD33 peptide (YIISGDSPV) and induced CTLs with increased cytotoxicity against AML cells. These data therefore demonstrate the potential of using immunogenic HLA-A2.1-specific CD33 peptides in developing a cellular immunotherapy for the treatment of AML patients.

IL-12 enhances the generation of tumour antigen-specific Th1 CD4 T cells during ex vivo expansion

CD4+ T cells are essential for the immune response against cancer. Vaccination against cancer will likely only be effective at preventing growth of micrometastatic disease while adoptive T cell therapy will be better suited for eradication of bulky pre-existing disease (Knutson et al. Expert Opin Biol Ther 2002; 2:55-66). Problems with the use of adoptive T cell therapy include lack of CD4+ T cell help, low frequency of antigen-specific T cells, and lack of effective ex vivo expansion techniques. In this study, we focused on improving ex vivo expansion of CD4+ T helper cells. The effects of IL-12, along with IL-2, on the ex vivo generation of HER-2/neu antigen-specific T cells were examined. Patients were immunized with a peptide-based vaccine that contained a helper epitope, p776-790, derived from the intracellular domain of HER-2/neu. While T cell immunity to p776-790, assessed by proliferation assays, could be readily measured in short-term cultures, cell line generation by multiple in vitro stimulation with peptide and IL-2 as the only added cytokine resulted in loss of antigen-specific proliferation. The inclusion of IL-12, along with IL-2, restored antigen-specific proliferation in a dose-dependent fashion. The resulting p776-790-specific T cells responded readily to antigen by proliferating and producing type I cytokines (IFN-gamma and TNF-alpha). The increased proliferative response of the cultures was due in part to an increase in the number of HER-2/neu-specific T cells. These results suggest that IL-12 is an important cytokine for ex vivo recovery and maintenance of antigen-specific CD4+ T lymphocytes that would otherwise be lost by using IL-2 alone in combination with antigen. Furthermore, these results have important implications for ex vivo expansion of CD4+ T cell for use in anti-tumour adoptive immunotherapy.

Immunological treatment of ovarian cancer

PURPOSE OF REVIEW

Development of immunological treatments for ovarian cancer has not been a conspicuous success story over the past few years. Only a handful of clinical trials have reported immunological responses, and correlation with clinical benefit has been elusive. Several recent studies presented in this review, however, point to a revival of optimism for the development of novel immunotherapeutic strategies.

RECENT FINDINGS

The cloning and sequencing of CA125, coupled with novel structural and functional insights, undoubtedly represent important steps forward. The possibility that CA125 could play a role in evasion of immunity by ovarian tumors may represent a new challenge, but does not detract from its potential as a therapeutic target. Of the recent clinical trial reports, the most intriguing results were seen from immunotherapy with a conventional mouse monoclonal antibody specific for CA125, in which human anti-mouse antibody responses correlated significantly with improved survival of patients with advanced stage ovarian cancer and clinical evidence of recurrent disease at the time of treatment.

SUMMARY

There is little doubt that CA125 will undergo a renaissance as an important target antigen for development of novel immunological treatments, particularly with regard to cellular therapies. Identification of other novel ovarian tumor antigens will also accelerate research focused on stimulation of T-cell immunity. Current research trends suggest a paradigm shift in emphasis from vaccines designed to elicit antibody responses to strategies such as dendritic cell vaccination that are designed to induce broader immunity, including ovarian tumor antigen-specific helper T-lymphocyte and cytotoxic T-lymphocyte responses.

HSP110-HER2/neu chaperone complex vaccine induces protective immunity against spontaneous mammary tumors in HER-2/neu transgenic mice

Heat shock proteins (HSPs) are shown to be strong immunoadjuvants, eliciting both innate and adaptive immune responses against cancers. HSP110 is related in sequence to HSP70 and is approximately 4-fold more efficient in binding to and stabilizing denatured protein substrates compared with HSP70. In the present study we evaluated the ability of a heat shock complex of HSP110 with the intracellular domain (ICD) of human HER-2/neu to elicit effective antitumor immune responses and to inhibit spontaneous mammary tumors in FVB-neu (FVBN202) transgenic mice. The HSP110-ICD complex was capable of breaking tolerance against the rat neu protein and inhibiting spontaneous mammary tumor development. This vaccine induced ICD-specific IFN-gamma and IL-4 production. Depletion studies revealed that CD8(+) T cells were involved in protection against challenge with mouse mammary tumors, whereas CD4(+) T cells revealed partial protection. Increased IgG2a Ab titer in the sera of tumor-free animals after vaccination and elevated CD4(+) CD25(+) regulatory T cells in the PBL of tumor-bearing animals suggested that IFN-gamma-producing Th1 cells may be responsible for partial protection of CD4(+) T cells against the mammary tumor challenge, whereas CD4(+)CD25(+) regulatory T cells (Th2 cells) may suppress the antitumor immune responses. Together, these results suggest that HSP110-ICD complex can elicit effective IFN-gamma-producing T cells against spontaneous mammary tumors and that up-regulation of CD4(+) CD25(+) regulatory T cells may prevent complete eradication of the tumor following immunotherapy.

Current research and treatment for epithelial ovarian cancer. A Position Paper from the Helene Harris Memorial Trust

In March 2003, an international mulltidisciplinary group of scientists and clinicians with a specific interest in ovarian cancer met for 4 days to discuss research into and treatment of this challenging disease. Under the headings of molecular genetics, molecular biology, the biology of ovarian cancer, old therapies, new targets and the early detection of the disease, this Position Paper summarises the presentations and discussion from the 9th Biennial Helene Harris Memorial Trust Forum on Ovarian Cancer. In particular, we highlight the potential of international collaborations in translating laboratory science into useful clinical interventions.

T-cell responses of vaccinated cancer patients

Following vaccination with defined tumor antigens that are recognized by T cells, a small proportion of cancer patients display tumor regressions. Several reports describe anti-vaccine T-cell responses, evaluated with a variety of methods, for example, by assessing T-cell function or expression of specific TCR. However, a correlation between these T-cell responses and the tumor regressions has not yet been established. It appears that some patients display tumor regression with an unexpectedly low frequency of anti-vaccine T cells.