Recombinant NY‐ESO‐1 Cancer Antigen: Production and Purification under cGMP Conditions

Lung cancer immunotherapy: progress, pitfalls, and promises

Lung cancer is the primary cause of mortality in the United States and around the globe. Therapeutic options for lung cancer treatment include surgery, radiation therapy, chemotherapy, and targeted drug therapy. Medical management is often associated with the development of treatment resistance leading to relapse. Immunotherapy is profoundly altering the approach to cancer treatment owing to its tolerable safety profile, sustained therapeutic response due to immunological memory generation, and effectiveness across a broad patient population. Different tumor-specific vaccination strategies are gaining ground in the treatment of lung cancer. Recent advances in adoptive cell therapy (CAR T, TCR, TIL), the associated clinical trials on lung cancer, and associated hurdles are discussed in this review. Recent trials on lung cancer patients (without a targetable oncogenic driver alteration) reveal significant and sustained responses when treated with programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) checkpoint blockade immunotherapies. Accumulating evidence indicates that a loss of effective anti-tumor immunity is associated with lung tumor evolution. Therapeutic cancer vaccines combined with immune checkpoint inhibitors (ICI) can achieve better therapeutic effects. To this end, the present article encompasses a detailed overview of the recent developments in the immunotherapeutic landscape in targeting small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Additionally, the review also explores the implication of nanomedicine in lung cancer immunotherapy as well as the combinatorial application of traditional therapy along with immunotherapy regimens. Finally, ongoing clinical trials, significant obstacles, and the future outlook of this treatment strategy are also highlighted to boost further research in the field.

Immunotherapy for lung cancer: Focusing on chimeric antigen receptor (CAR)-T cell therapy

Besides traditional treatment strategies, including surgery, radiotherapy, and chemotherapy for lung cancer as the leading cause of cancer incidence and death, immunotherapy has also emerged as a new treatment strategy. The goal of immunotherapy is to stimulate the immune system responses against cancer, using various approaches such as therapeutic vaccines, monoclonal antibodies, immune checkpoint inhibitors, and T-cell therapy. Chimeric antigen receptor (CAR)-T cells, one of the most popular cancer immunotherapy approaches in the last decade, are genetically engineered T-cells to redirect patients' immune responses to recognize and eliminate tumor-associated antigens (TAA)-expressing tumor cells. CAR-T cell therapy provides promising benefits in lung tumors. In this review, we summarize different immunotherapy approaches for lung cancer, the structure of CAR-T cells, currently undergoing CARs in clinical trials, and various TAAs are being investigated as potential targets in designing CAR-T cells for lung cancer.

Results of a randomized, double-blind phase II clinical trial of NY-ESO-1 vaccine with ISCOMATRIX adjuvant versus ISCOMATRIX alone in participants with high-risk resected melanoma

BACKGROUND

To compare the clinical efficacy of New York Esophageal squamous cell carcinoma-1 (NY-ESO-1) vaccine with ISCOMATRIX adjuvant versus ISCOMATRIX alone in a randomized, double-blind phase II study in participants with fully resected melanoma at high risk of recurrence.

METHODS

Participants with resected stage IIc, IIIb, IIIc and IV melanoma expressing NY-ESO-1 were randomized to treatment with three doses of NY-ESO-1/ISCOMATRIX or ISCOMATRIX adjuvant administered intramuscularly at 4-week intervals, followed by a further dose at 6 months. Primary endpoint was the proportion free of relapse at 18 months in the intention-to-treat (ITT) population and two per-protocol populations. Secondary endpoints included relapse-free survival (RFS) and overall survival (OS), safety and NY-ESO-1 immunity.

RESULTS

The ITT population comprised 110 participants, with 56 randomized to NY-ESO-1/ISCOMATRIX and 54 to ISCOMATRIX alone. No significant toxicities were observed. There were no differences between the study arms in relapses at 18 months or for median time to relapse; 139 vs 176 days (p=0.296), or relapse rate, 27 (48.2%) vs 26 (48.1%) (HR 0.913; 95% CI 0.402 to 2.231), respectively. RFS and OS were similar between the study arms. Vaccine recipients developed strong positive antibody responses to NY-ESO-1 (p≤0.0001) and NY-ESO-1-specific CD4+ and CD8+ responses. Biopsies following relapse did not demonstrate differences in NY-ESO-1 expression between the study populations although an exploratory study demonstrated reduced (NY-ESO-1)+/Human Leukocyte Antigen (HLA) class I+ double-positive cells in biopsies from vaccine recipients performed on relapse in 19 participants.

CONCLUSIONS

The vaccine was well tolerated, however, despite inducing antigen-specific immunity, it did not affect survival endpoints. Immune escape through the downregulation of NY-ESO-1 and/or HLA class I molecules on tumor may have contributed to relapse.

Vaccine and immune cell therapy in non-small cell lung cancer

Despite new advances in therapeutics, lung cancer remains the first cause of mortality among different types of malignancies. To improve survival, different strategies have been developed such as chemotherapy combinations, targeted therapies and more recently immunotherapy. Immunotherapy is based on the capability of the immune system to differentiate cancer cells from normal cells to fight against the tumor. The two main checkpoint inhibitors that have been widely studied in non-small cell lung cancer (NSCLC) are PD-1/PD-L1 and CTLA-4. However, interactions between tumor and immune system are much more complex with several different elements that take part and probably many new interactions to be discovered and studied for a better comprehension of those pathways. Vaccines are part of the prophylaxis and of the treatment for different infectious diseases. For that reason, they have allowed us to improve global survival worldwide. This same idea can be used for cancer treatment. First reports in clinical trials that used therapeutic vaccines in NSCLC were discouraging, but currently vaccines have a new chance in cancer therapy with the identification of new targetable antigens, adjuvant treatments and most interestingly, the combination of vaccines with anti-PD-1/PD-L1 and anti-CTLA-4 drugs. The aim of this article is to describe the scientific evidence that has been reported for the different types of vaccines and their mechanisms of action in the fight against NSCLC tumors to improve disease control.

PEGylation and its impact on the design of new protein-based medicines

PEGylation is the covalent conjugation of PEG to therapeutic molecules. Protein PEGylation is a clinically proven approach for extending the circulation half-life and reducing the immunogenicity of protein therapeutics. Most clinically used PEGylated proteins are heterogeneous mixtures of PEG positional isomers conjugated to different residues on the protein main chain. Current research is focused to reduce product heterogeneity and to preserve bioactivity. Recent advances and possible future directions in PEGylation are described in this review. So far protein PEGylation has yielded more than 10 marketed products and in view of the lack of equally successful alternatives to extend the circulation half-life of proteins, PEGylation will still play a major role in drug delivery for many years to come.

Low-dose cyclophosphamide enhances antigen-specific CD4(+) T cell responses to NY-ESO-1/ISCOMATRIX™ vaccine in patients with advanced melanoma

Clinical outcomes from cancer vaccine trials in patients with advanced melanoma have so far been disappointing. This appears at least partially due to a state of immunosuppression in these patients induced by an expansion of regulatory cell populations including regulatory T cells (Tregs). We have previously demonstrated potent immunogenicity of the NY-ESO-1/ISCOMATRIX™ vaccine in patients with resected melanoma (study LUD99-08); however, the same vaccine induced only a few vaccine antigen-specific immune responses in patients with advanced disease (study LUD2002-013). Pre-clinical models suggest that the alkylating agent cyclophosphamide can enhance immune responses by depleting Tregs. Therefore, we have enrolled a second cohort of patients with advanced melanoma in the clinical trial LUD2002-013 to investigate whether pre-treatment with cyclophosphamide could improve the immunogenicity of the NY-ESO-1/ISCOMATRIX™ vaccine. The combination treatment led to a significant increase in vaccine-induced NY-ESO-1-specific CD4(+) T cell responses compared with the first trial cohort treated with vaccine alone. We could not detect a significant decline in regulatory T cells in peripheral blood of patients 14 days after cyclophosphamide administration, although a decline at an earlier time point cannot be excluded. Our observations support the inclusion of cyclophosphamide in combination trials with vaccines and other immune-modulatory agents.

NY-ESO-1 specific antibody and cellular responses in melanoma patients primed with NY-ESO-1 protein in ISCOMATRIX and boosted with recombinant NY-ESO-1 fowlpox virus

Vaccination strategies based on repeated injections of NY-ESO-1 protein formulated in ISCOMATRIX particles (NY-ESO-1 ISCOMATRIX) have shown to elicit combined NY-ESO-1 specific antibody and T cell responses. However, it remains unclear whether heterologous prime-boost strategies based on the combination with NY-ESO-1 ISCOMATRIX with different NY-ESO-1 boosting reagents could be used to increase NY-ESO-1 CD8(+) or CD4(+) T cell responses. To address this question, we carried out a randomized clinical trial in 39 high-risk, resected melanoma patients vaccinated with NY-ESO-1 ISCOMATRIX, and then boosted with repeated injections of either recombinant fowlpox virus encoding full length NY-ESO-1 (rF-NY-ESO-1) (Arm A) or NY-ESO-1 ISCOMATRIX alone (Arm B). We have comprehensively analyzed NY-ESO-1 specific T cells and B cells response in all patients before and after vaccination for a total of seven time points per patient. NY-ESO-1 ISCOMATRIX alone elicited a strong NY-ESO-1 specific CD4(+) T cell and antibody response, which was maintained by both regiments at similar levels. However, CD8(+) T cell responses were significantly boosted in 3 out of 18 patients in Arm A after the first rF-NY-ESO-1 injection and such responses were maintained until the end of the trial, while no patients in Arm B showed similar CD8(+) T cell responses. In addition, our results clearly identified immunodominant regions in the NY-ESO-1 protein: NY-ESO-179-102 and NY-ESO-1115-138 for CD4+ T cells and NY-ESO-185-108 for CD8+ T cells in a large proportion of vaccinated patients. These regions of NY-ESO-1 protein should be considered in future clinical trials as immunodominant epitopes.

A novel HLA-B18 restricted CD8+ T cell epitope is efficiently cross-presented by dendritic cells from soluble tumor antigen

NY-ESO-1 has been a major target of many immunotherapy trials because it is expressed by various cancers and is highly immunogenic. In this study, we have identified a novel HLA-B*1801-restricted CD8⁺ T cell epitope, NY-ESO-1_88–96 (LEFYLAMPF) and compared its direct- and cross-presentation to that of the reported NY-ESO-1_157–165 epitope restricted to HLA-A*0201. Although both epitopes were readily cross-presented by DCs exposed to various forms of full-length NY-ESO-1 antigen, remarkably NY-ESO-1_88–96 is much more efficiently cross-presented from the soluble form, than NY-ESO-1_157–165. On the other hand, NY-ESO-1_157–165 is efficiently presented by NY-ESO-1-expressing tumor cells and its presentation was not enhanced by IFN-γ treatment, which induced immunoproteasome as demonstrated by Western blots and functionally a decreased presentation of Melan A_26–35; whereas NY-ESO-1_88–96 was very inefficiently presented by the same tumor cell lines, except for one that expressed high level of immunoproteasome. It was only presented when the tumor cells were first IFN-γ treated, followed by infection with recombinant vaccinia virus encoding NY-ESO-1, which dramatically increased NY-ESO-1 expression. These data indicate that the presentation of NY-ESO-1_88–96 is immunoproteasome dependent. Furthermore, a survey was conducted on multiple samples collected from HLA-B18⁺ melanoma patients. Surprisingly, all the detectable responses to NY-ESO-1_88–96 from patients, including those who received NY-ESO-1 ISCOMATRIX™ vaccine were induced spontaneously. Taken together, these results imply that some epitopes can be inefficiently presented by tumor cells although the corresponding CD8⁺ T cell responses are efficiently primed in vivo by DCs cross-presenting these epitopes. The potential implications for cancer vaccine strategies are further discussed.

Site-specific PEGylation at histidine tags

The efficacy of protein-based medicines can be compromised by their rapid clearance from the blood circulatory system. Achieving optimal pharmacokinetics is a key requirement for the successful development of safe protein-based medicines. Protein PEGylation is a clinically proven strategy to increase the circulation half-life of protein-based medicines. One limitation of PEGylation is that there are few strategies that achieve site-specific conjugation of PEG to the protein. Here, we describe the covalent conjugation of PEG site-specifically to a polyhistidine tag (His-tag) on a protein. His-tag site-specific PEGylation was achieved with a domain antibody (dAb) that had a 6-histidine His-tag on the C-terminus (dAb-His(6)) and interferon α-2a (IFN) that had an 8-histidine His-tag on the N-terminus (His(8)-IFN). The site of PEGylation at the His-tag for both dAb-His(6)-PEG and PEG-His(8)-IFN was confirmed by digestion, chromatographic, and mass-spectral studies. A methionine was also inserted directly after the N-terminal His-tag in IFN to give His(8)Met-IFN. Cyanogen bromide digestion studies of PEG-His(8)Met-IFN were also consistent with PEGylation at the His-tag. By using increased stoichiometries of the PEGylation reagent, it was possible to conjugate two separate PEG molecules to the His-tag of both the dAb and IFN proteins. Stability studies followed by in vitro evaluation confirmed that these PEGylated proteins retained their biological activity. In vivo PK studies showed that all of the His-tag PEGylated samples displayed extended circulation half-lives. Together, our results indicate that site-specific, covalent PEG conjugation at a His-tag can be achieved and biological activity maintained with therapeutically relevant proteins.

Immunoediting and persistence of antigen-specific immunity in patients who have previously been vaccinated with NY-ESO-1 protein formulated in ISCOMATRIX™

BACKGROUND

NY-ESO-1 protein formulated in ISCOMATRIX™ results in CD4+, CD8+ T cell and antibody-mediated immunity. We evaluated persistence of immunity, relapse-free survival and tumour antigen expression upon relapse in patients vaccinated in an earlier trial.

METHODS

Immunity was measured in 28 patients with resected NY-ESO-1-expressing tumours (melanoma 25, breast 3) 252-1,155 days (median = 681) after vaccination. In the earlier vaccination, trial patients received NY-ESO-1 with ISCOMATRIX™ adjuvant at three protein doses 10 μg, 30 μg or 100 μg (n = 14); 100 μg NY-ESO-1 protein (n = 8) or placebo (n = 6), together with 1 μg of intradermal (ID) NY-ESO-1 protein twice for DTH skin testing. Immune responses assessed in the current study included antibody titres, circulating NY-ESO-1-specific T cells and DTH reactivity 2 days after DTH skin testing with NY-ESO-1 protein (1 μg) or peptides (10 μg). Relapse-free survival was determined for 42 melanoma patients. On relapse NY-ESO-1 and HLA, class I was assessed by immunohistochemistry in 17.

RESULTS

Persisting anti-NY-ESO-1 immunity was detected in 10/14 recipients who had previously received vaccine with ISCOMATRIX™ adjuvant. In contrast, immunity only persisted in 3/14 who received 100 μg un-adjuvanted NY-ESO-1 protein (3/8) or 2 μg DTH protein (0/6) P = 0.02. Hence, persisting NY-ESO-1 immunity was associated with prior adjuvant. Tumour NY-ESO-1 or HLA class I was downregulated in participants who relapsed suggesting immunoediting had occurred.

CONCLUSION

Immunoediting suggests that a signal of anti-tumour activity was observed in high-risk resected melanoma patients vaccinated with NY-ESO-1/ISCOMATRIX™. This was associated with measurable persisting immunity in the majority of vaccinated subjects tested. A prospective randomised trial has been undertaken to confirm these results.

Detection and expression analysis of recombinant proteins in plant-derived complex mixtures using nanoUPLC-MS(E)

The use of mass spectrometry to identify recombinant proteins that are expressed in total soluble proteins (TSPs) from plant extracts is necessary to accelerate further processing steps. For example, the method consists of TSP sample preparation and trypsin digestion prior to the preliminary characterization using nanoUPLC-MS(E) analysis of the recombinant proteins that are expressed in TSP samples of transgenic soybean seeds. A TSP sample as small as 50 μg can be effectively analyzed. In this study, transgenic soybean seeds that expressed recombinant cancer testis antigen (CTAG) were used. The procedure covered 30% of the protein sequence and was quantified at 0.26 ng, which corresponded to 0.1% of the TSP sample. A comparative proteomic profile was generated by the comparison of a negative control and sample that showed a unique expression pattern of CTAG in a transgenic line. The experimental data from the TSP extraction, sample preparation and data analysis are discussed herein.

Three novel NY-ESO-1 epitopes bound to DRB1*0803, DQB1*0401 and DRB1*0901 recognized by CD4 T cells from CHP-NY-ESO-1-vaccinated patients

Three novel NY-ESO-1 CD4 T cell epitopes were identified using PBMC obtained from patients who were vaccinated with a complex of cholesterol-bearing hydrophobized pullulan (CHP) and NY-ESO-1 protein (CHP-NY-ESO-1). The restriction molecules were determined by antibody blocking and using various EBV-B cells with different HLA alleles as APC to present peptides to CD4 T cells. The minimal epitope peptides were determined using various N- and C-termini truncated peptides deduced from 18-mer overlapping peptides originally identified for recognition. Those epitopes were DRB1*0901-restricted NY-ESO-1 87-100, DQB1*0401-restricted NY-ESO-1 95-107 and DRB1*0803-restricted NY-ESO-1 124-134. CD4 T cells used to determine those epitope peptides recognized EBV-B cells or DC that were treated with recombinant NY-ESO-1 protein or NY-ESO-1-expressing tumor cell lysate, suggesting that the epitope peptides are naturally processed. These CD4 T cells showed a cytokine profile with Th1 characteristics. Furthermore, NY-ESO-1 87-100 peptide/HLA-DRB1*0901 tetramer staining was observed. Multiple Th1-type CD4 T cell responses are beneficial for inducing effective anti-tumor responses after NY-ESO-1 protein vaccination.

Toward the total chemical synthesis of the cancer protein NY-ESO-1

During the course of developing a synthetic route for the cancer protein NY-ESO-1 using native chemical ligation, a number of the required thioester polypeptide fragments were unable to be synthesized effectively using Boc solid phase peptide synthesis. Modification of the SPPS protocols to include an arginine tag at the C terminus linked via the thioester resulted in a better purity profile and enhanced solubility, facilitating purification by HPLC. During preparation of another reactive partner for ligation that contained an internal Cys(Acm) residue by Fmoc SPPS, extensive loss of the Acm group occurred during cleavage from the resin while substitution with Cys(tBu) resulted in no loss of protecting group. It was shown that native chemical ligation of N-terminal cysteine peptide 155-180 containing the Cys(tBu) residue with thioester 140-154 was slow, incomplete and led to extensive HPLC column fouling. Subsequent incorporation of a C-terminal arginine tag into the N-terminal NY-ESO-1 155-180 fragment joined by a base labile 4-hydroxymethylbenzoic acid (HMBA) linker facilitated rapid quantitative ligation. The HMBA linker was demonstrated to be stable to the conditions required for native chemical ligation, subsequent transformations and final purification. Importantly it was effectively removed at pH=10.

Evaluation of cellular immune responses in cancer vaccine recipients: lessons from NY-ESO-1

The rigorous evaluation of cancer vaccination requires evidence of benefit to patients with cancer or those at risk of relapse from the disease. Clinical trials are expensive and require considerable human and clinical resources in order to demonstrate this benefit. In the era of defined cancer antigens, it is possible to evaluate immunogenic targets, and assess the quality and magnitude of immune responses against these antigens following vaccination. Analyzing these surrogate end points complements clinical assessment and provides a depth of understanding to better inform trial evaluation and design. We have used the immunogenic cancer testis antigen NY-ESO-1 as a model antigen. This article summarizes our experience in monitoring immunity against NY-ESO-1.

Processing and cross-presentation of individual HLA-A, -B, or -C epitopes from NY-ESO-1 or an HLA-A epitope for Melan-A differ according to the mode of antigen delivery

The ability of dendritic cells (DCs) to cross-present protein tumor antigens to cytotoxic T lymphocytes (CTLs) underpins the success of therapeutic cancer vaccines. We studied cross-presentation of the cancer/testis antigen, NY-ESO-1, and the melanoma differentiation antigen, Melan-A by human DC subsets. Monocyte-derived DCs (MoDCs) efficiently cross-presented human leukocyte associated (HLA)-A2-restricted epitopes from either a formulated NY-ESO-1/ISCOMATRIX vaccine or when either antigen was mixed with ISCOMATRIX adjuvant. HLA-A2 epitope generation required endosomal acidification and was proteasome-independent for NY-ESO-1 and proteasome-dependent for Melan-A. Both MoDCs and CD1c(+) blood DCs cross-presented NY-ESO-1-specific HLA-A2(157-165)-, HLA-B7(60-72)-, and HLA-Cw3(92-100)-restricted epitopes when formulated as an NY-ESO-1/ISCOMATRIX vaccine, but this was limited when NY-ESO-1 and ISCOMATRIX adjuvant were added separately to the DC cultures. Finally, cross-presentation of NY-ESO-1(157-165)/HLA-A2, NY-ESO-1(60-72)/HLA-B7, and NY-ESO-1(92-100)/HLA-Cw3 epitopes was proteasome-dependent when formulated as immune complexes (ICs) but only proteasome-dependent for NY-ESO-1(60-72)/HLA-B7-restricted cross-presentation facilitated by ISCOMATRIX adjuvant. We demonstrate, for the first time, proteasome-dependent and independent cross-presentation of HLA-A-, B-, and C-restricted epitopes within the same full-length tumor antigen by human DCs. Our findings identify important differences in the capacities of human DC subsets to cross-present clinically relevant, full-length tumor antigens and how vaccine formulation impacts CTL responses in vivo.

Recombinant immunotherapeutics: current state and perspectives regarding the feasibility and market

Recombinant immunotherapeutics are important biologics for the treatment and prevention of various diseases. Immunotherapy can be divided into two categories, passive and active. For passive immunotherapy, the successes of antibody and cytokine therapeutics represent a promising future and opportunities for improvements. Efforts, such as cell engineering, antibody engineering, human-like glycosylation in yeast, and Fab fragment development, have led the way to improve antibody efficacy while decreasing its high manufacturing costs. Both new cytokines and currently used cytokines have demonstrated therapeutic effects for different indications. As for active immunotherapy, recently approved HPV vaccines have encouraged the development of preventative vaccines for other infectious diseases. Immunogenic antigens of pathogenic bacteria can now be identified by genomic means (reverse vaccinology). Due to the recent outbreaks of pandemic H1N1 influenza virus, recombinant influenza vaccines using virus-like particles and other antigens have also been engineered in several different recombinant systems. However, limitations are found in existing immunotherapeutics for cancer treatment, and recent development of therapeutic cancer vaccines such as MAGE-A3 and NY-ESO-1 may provide alternative therapeutic strategy.

Inducing efficient cross-priming using antigen-coated yeast particles

Saccharomyces cerevisiae stimulates dendritic cells (DCs) and represents a promising candidate for cancer vaccine development. Effective cross-presentation of antigen delivered to DCs is necessary for successful induction of cellular immunity. Here, we present a yeast-based vaccine approach that is independent of yeast's ability to express the chosen antigen, which is instead produced separately and conjugated to the yeast cell wall. The conjugation method is site-specific (based on the SNAP-tag) and designed to facilitate antigen release in the DC phagosome and subsequent translocation for cross-presentation. We demonstrate that nonsite-specific chemical conjugation of the same protein hinders cross-presentation. Phagosomal antigen release was further expedited through the insertion of the invariant chain ectodomain as a linker, which is rapidly cleaved by Cathepsin S. The dose of delivered antigen was increased in several ways: by using yeast strains with higher surface amine densities, by using yeast hulls (cell wall fragments) instead of whole cells, and by conjugating multiple layers of antigen. The novel multilayer conjugation scheme takes advantage of Sfp phosphopantetheinyl transferase and remains site-specific; it enables the antigen dose to grow linearly with the number of layers. We show that whole yeast cells coated with 1 layer of the cancer-testis antigen NY-ESO-1 and yeast hulls bearing 3 layers were able to cross-prime naive CD8 T cells in vitro, with the latter resulting in higher frequencies of antigen-specific cells after 10 days. This cross-presentation-efficient antigen conjugation scheme is not limited to yeast and can readily be applied toward the development of other particulate vaccines.

ISCOMATRIX adjuvant induces efficient cross-presentation of tumor antigen by dendritic cells via rapid cytosolic antigen delivery and processing via tripeptidyl peptidase II

Cancer vaccines aim to induce antitumor CTL responses, which require cross-presentation of tumor Ag to CTLs by dendritic cells (DCs). Adjuvants that facilitate cross-presentation of vaccine Ag are therefore key for inducing antitumor immunity. We previously reported that human DCs could not efficiently cross-present the full-length cancer/testis Ag NY-ESO-1 to CTL unless formulated as either an immune complex (NY-ESO-1/IC) or with ISCOMATRIX adjuvant. We now demonstrate that NY-ESO-1/ICs induce cross-presentation of HLA-A2- and HLA-Cw3-restricted epitopes via a proteasome-dependent pathway. In contrast, cross-presentation of NY-ESO-1/ISCOMATRIX vaccine was proteasome independent and required the cytosolic protease tripeptidyl peptidase II. Trafficking studies revealed that uptake of ICs and ISCOMATRIX vaccine by DCs occurred via endocytosis with delivery to lysosomes. Interestingly, ICs were retained in lysosomes, whereas ISCOMATRIX adjuvant induced rapid Ag translocation into the cytosol. Ag translocation was dependent on endosomal acidification and IL-4-driven differentiation of monocytes into DCs. This study demonstrates that Ag formulation determines Ag processing and supports a role for tripeptidyl peptidase II in cross-presentation of CTL epitopes restricted to diverse HLA alleles.

Regulatory T-cell-mediated attenuation of T-cell responses to the NY-ESO-1 ISCOMATRIX vaccine in patients with advanced malignant melanoma

PURPOSE

NY-ESO-1 is a highly immunogenic antigen expressed in a variety of malignancies, making it an excellent target for cancer vaccination. We recently developed a vaccine consisting of full-length recombinant NY-ESO-1 protein formulated with ISCOMATRIX adjuvant, which generated strong humoral and T-cell-mediated immune responses and seemed to reduce the risk of disease relapse in patients with fully resected melanoma. This study examines the clinical and immunologic efficacy of the same vaccine in patients with advanced metastatic melanoma.

EXPERIMENTAL DESIGN

Delayed-type hypersensitivity responses, circulating NY-ESO-1-specific CD4(+) and CD8(+) T cells, and proportions of regulatory T cells (Treg) were assessed in patients.

RESULTS

In contrast to patients with minimal residual disease, advanced melanoma patients showed no clinical responses to vaccination. Although strong antibody responses were mounted, the generation of delayed-type hypersensitivity responses was significantly impaired. The proportion of patients with circulating NY-ESO-1-specific CD4(+) T cells was also reduced, and although many patients had CD8(+) T cells specific to a broad range of NY-ESO-1 epitopes, the majority of these responses were preexisting. Tregs were enumerated in the blood by flow cytometric detection of cells with a CD4(+)CD25(+)FoxP3(+) and CD4(+)CD25(+)CD127(-) phenotype. Patients with advanced melanoma had a significantly higher proportion of circulating Treg compared with those with minimal residual disease.

CONCLUSIONS

Our results point to a tumor-induced systemic immune suppression, showing a clear association between the stage of melanoma progression, the number of Treg in the blood, and the clinical and immunologic efficacy of the NY-ESO-1 ISCOMATRIX cancer vaccine.

Production, safety and antitumor efficacy of recombinant Oncofetal Antigen/immature laminin receptor protein

We describe here for the first time an efficient high yield production method for clinical grade recombinant human Oncofetal Antigen/immature laminin receptor protein (OFA/iLRP). We also demonstrate significant antitumor activity for this protein when administered in liposomal delivery form in a murine model of syngeneic fibrosarcoma. OFA/iLRP is a therapeutically very promising universal tumor antigen that is expressed in all mammalian solid tumors tested so far. We have cloned the human OFA/iLRP cDNA in a bacterial expression plasmid which incorporates a 6x HIS-tag. Large scale cultures of the plasmid transformed Escherichia coli were performed and the crude HIS-tagged OFA/iLRP was isolated as inclusion bodies and solubilized in guanidine chloride. The protein was then purified by successive passage through three column chromatography steps of immobilized metal affinity, anion exchange, and gel filtration. The resulting protein was 94% pure and practically devoid of endotoxin and host cell protein. The purified OFA/iLRP was tested in mice for safety and efficacy in tumor rejection with satisfactory results. This protein will be used for loading onto autologous dendritic cells in an FDA approved phase I/II human cancer vaccine trial in OFA/iLRP-positive breast cancer patients.

Analysis of peripheral and local anti-tumor immune response in esophageal cancer patients after NY-ESO-1 protein vaccination

NY-ESO-1 antigen is a prototype of a class of cancer/testis antigens. We carried out a clinical trial using NY-ESO-1 whole protein as a cancer vaccine for 13 advanced cancer patients. We have recently reported that vaccine elicited humoral and cellular immune responses in 9 cancer patients including 4 esophageal cancer patients, and clinical responses were also observed in 4 of 5 evaluable patients. In this study, we analyzed the responses in 8 esophageal cancer patients including 4 newly enrolled patients. Patients were injected subcutaneously at biweekly intervals with NY-ESO-1 recombinant protein formulated with cholesterol-bearing hydrophobized pullulan. Induction of antibody, and CD4 and CD8 T-cell responses were observed in 7, 7 and 6 patients, respectively, out of 8 patients. 1 PR, 2 SD and 2 mixed clinical responses were observed in 6 evaluable patients. No significant adverse events were observed. Furthermore, we analyzed NY-ESO-1 and MHC class I expression and the infiltration of immune cells into tumor samples obtained before and after vaccination from 4 patients by immunohistochemistry. The results showed 2 patients with disappearance of CD4 and CD8 T-cell infiltration, 1 patient with increase in the number of CD68(+) macrophages and 1 patient with tumor antigen loss in the progressive tumors following vaccinations. The induction of NY-ESO-1 immunity and some preferable clinical outcomes were observed in esophageal cancer patients by vaccination with NY-ESO-1. However, the tumors grew eventually by various mechanisms after vaccination.

Induction of immune response against NY-ESO-1 by CHP-NY-ESO-1 vaccination and immune regulation in a melanoma patient

BACKGROUND

NY-ESO-1 is a cancer/testis antigen highly immunogenic in cancer patients. Cholesterol-bearing hydrophobized pullulan (CHP) is a nanoparticle-forming antigen-delivery vehicle and CHP complexed with NY-ESO-1 protein (CHP-NY-ESO-1) efficiently activates CD4 and CD8 T cells in vitro.

AIM

In this study we report on a 50-year-old male melanoma patient with multiple skin and organ metastases (T4N3M1c) who was vaccinated with CHP-NY-ESO-1 at biweekly intervals and who had an unusual disease course. We characterized in this patient humoral and cellular immune responses, immune regulatory cells, and cytokine profiles in the peripheral blood and at local tumor sites.

RESULTS

Ten days after the second CHP-NY-ESO-1 vaccination (day 25), blisters appeared on the skin at the metastatic lesions associated with inflammatory changes. A skin biopsy showed the presence of many NY-ESO-1-expressing apoptotic melanoma cells as determined by a terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) test. However, the tumors continued to grow, and the patient died of pulmonary failure due to multiple metastases on day 48. Serum antibody responses were detected after the second CHP-NY-ESO-1 vaccination and antibody titer increased with subsequent vaccinations. Th1 dependent IgG1 was the predominant immunoglobulin subtype. Both, NY-ESO-1-specific CD4 and CD8 T cell responses were detected in PBMC by IFN-gamma secretion assays. After CHP-NY-ESO-1 vaccination a slight decrease in CD4(+)CD25(+)Foxp3(+) Tregs was observed in PBMC but significantly increased numbers of CD4(+)CD25(+)Foxp3(+) Tregs and CD68(+) immunoregulatory macrophages were detected at the local tumor sites. CD4(+)CD25(+)Foxp3(+) Tregs were also increased in the blister fluid. Cytokines in the serum suggested a polarization towards a Th1 pattern in the PBMC and those in the blister fluid suggested a Th2-type response at the tumor site.

CONCLUSIONS

Our observations indicate induction of specific humoral and cellular immune responses against NY-ESO-1 after CHP-NY-ESO-1 vaccination in a melanoma patient. The concomitant appearance of regulatory T cells and of immune regulatory macrophages and cytokines at the local tumor sites in this patient may explain immune escape.

Antibody response against NY-ESO-1 in CHP-NY-ESO-1 vaccinated patients

NY-ESO-1 specific humoral responses are frequently observed in patients with various types of NY-ESO-1 antigen expressing tumors. In a large proportion of NY-ESO-1 antibody-positive patients of NY-ESO-1-specific CD8 T-cells can also be detected suggesting that monitoring of the NY-ESO-1 specific humoral immune response may be a relevant and more practical surrogate for estimating the overall immune response against NY-ESO-1 in clinical vaccine studies. We have immunized 9 cancer patients with full length NY-ESO-1 protein formulated with cholesterol-bearing hydrophobized pullulan (CHP-NY-ESO-1) and investigated the humoral immune responses against NY-ESO-1. Seven patients were NY-ESO-1 antibody-negative and 2 patients were positive prior to vaccination. Vaccination with CHP-NY-ESO-1 resulted in the induction or increase of NY-ESO-1 antibody responses in all 9 patients immunized. Epitope analysis revealed 5 regions in the NY-ESO-1 protein molecule that were recognized by antibodies induced after vaccination. The 5 regions were also recognized by antibodies present in nonvaccinated, NY-ESO-1 antibody-positive cancer patients. A peptide spanning amino acids 91-108 was recognized in 6 out of 9 vaccinated patients and in 8 out of 9 nonvaccinated, sero-positive patients, being the most dominant antigenic epitope in NY-ESO-1 for antibody recognition in cancer patients. In conclusion, we showed that CHP-NY-ESO-1 protein vaccination had a potent activity for inducing humoral immune responses against NY-ESO-1 antigen in cancer patients. The antigenic epitopes recognized by antibodies in the vaccinated patients were similar to those recognized in cancer patients with spontaneous humoral immunity against NY-ESO-1.

NY-ESO-1 immunotherapy for multiple myeloma

Most patients with poor-prognosis myeloma (abnormal metaphase cytogenetics) achieve excellent responses with tandem transplants, but the remissions are not durable. Novel interventions such as immunotherapy may eradicate the residual chemotherapy-resistant disease. Immunotherapy targeting weak antigens such as myeloma idiotype or tumor lysate has failed to produce clinically meaningful responses. We previously reported that the NY-ESO-1 antigen is expressed in >60% of poor-prognosis myeloma at diagnosis. Since NY-ESO-1 is highly immunogenic and is not expressed in most normal tissues, it is an ideal target for anti-myeloma immunotherapy. NY-ESO-1 based therapies are already being tested in clinical trials for a multitude of tumors. This review discusses the potential of NY-ESO-1 immunotherapy to improve outcome for myeloma.

NY-ESO-1: review of an immunogenic tumor antigen

In the 9 years since its discovery, cancer-testis antigen NY-ESO-1 has made one of the fastest transitions from molecular, cellular, and immunological description to vaccine and immunotherapy candidate, already tested in various formulations in more than 30 clinical trials worldwide. Its main characteristic resides in its capacity to elicit spontaneous antibody and T-cell responses in a proportion of cancer patients. An overview of immunological findings and immunotherapeutic approaches with NY-ESO-1, as well the role of regulation in NY-ESO-1 immunogenicity, is presented here.

Directed evolution for improved secretion of cancer–testis antigen NY-ESO-1 from yeast

NY-ESO-1 is a highly immunogenic tumor antigen and a promising vaccine candidate in cancer immunotherapy. Access to purified protein both for vaccine formulations and for monitoring antigen-specific immune responses is vital to vaccine development. Currently available recombinant Escherichia coli-derived NY-ESO-1 is isolated from inclusion bodies as a complex protein mixture and efforts to improve the purity of this antigen are required, especially for later-stage clinical trials. Using yeast cell surface display and fluorescence activated cell sorting techniques, we have engineered an NY-ESO-1 variant (NY-ESO-L5; C(75)A C(76)A C(78)A L(153)H) with a 100x improved display level on yeast compared to the wild-type protein. This mutant can be effectively produced as an Aga2p-fusion and purified in soluble form directly from the yeast cell wall. In the process, we have identified the epitope recognized by anti-NY-ESO-1 mAb E978 (79-87, GARGPESRL). The availability of an alternative expression host for this important antigen will help avoid artifactual false positive tests of patient immune response due to reaction against expression-host-specific contaminants.

Genetic selection for protein solubility enabled by the folding quality control feature of the twin-arginine translocation pathway

One of the most vexing problems facing structural genomics efforts and the biotechnology enterprise in general is the inability to efficiently produce functional proteins due to poor folding and insolubility. Additionally, protein misfolding and aggregation has been linked to a number of human diseases, such as Alzheimer's. Thus, a robust cellular assay that allows for direct monitoring, manipulation, and improvement of protein folding could have a profound impact. We report the development and characterization of a genetic selection for protein folding and solubility in living bacterial cells. The basis for this assay is the observation that protein transport through the bacterial twin-arginine translocation (Tat) pathway depends on correct folding of the protein prior to transport. In this system, a test protein is expressed as a tripartite fusion between an N-terminal Tat signal peptide and a C-terminal TEM1 beta-lactamase reporter protein. We demonstrate that survival of Escherichia coli cells on selective medium expressing a Tat-targeted test protein/beta-lactamase fusion correlates with the solubility of the test protein. Using this assay, we isolated solubility-enhanced variants of the Alzheimer's Abeta42 peptide from a large combinatorial library of Abeta42 sequences, thereby confirming that our assay is a highly effective selection tool for soluble proteins. By allowing the bacterial Tat pathway to exert folding quality control on expressed target protein sequences, we have generated a powerful tool for monitoring protein folding and solubility in living cells, for molecular engineering of solubility-enhanced proteins or for the isolation of factors and/or cellular conditions that stabilize aggregation-prone proteins.