Immunological monitoring of cancer vaccine therapy

Evaluating Anti-tumor Immune Responses of Protein Nanoparticle-Based Cancer Vaccines

Cancer vaccines displaying tumor-associated antigens (TAAs) train the immune system for enhanced tumor recognition and elimination. Nanoparticle-based cancer vaccines are ingested and processed by dendritic cells, which subsequently activate antigen-specific cytotoxic T cells, allowing them to identify and eliminate tumor cells displaying these TAAs. Here, we describe the procedures to conjugate TAA and adjuvant to a model protein nanoparticle platform (E2), followed by assessment of vaccine performance. Utilizing a syngeneic tumor model, the efficacy of in vivo immunization was determined by cytotoxic T lymphocyte assays and IFN-γ ELISpot ex vivo assays to measure tumor cell lysis and TAA-specific activation, respectively. In vivo tumor challenge directly allows evaluation of anti-tumor response and survival over time.

Predictive biomarkers and effectiveness of MUC1-targeted dendritic-cell-based vaccine in patients with refractory non-small cell lung cancer

BACKGROUND

The dendritic cell (DC)-based vaccine targeting the highly immunogenic tumor antigen, MUC1, has been promising for a cancer immunotherapy; however, predictive biomarkers for beneficial clinical responses of the vaccine remain to be determined.

METHODS

DCs loaded with MUC1-derived peptide were subcutaneously administered to patients with MUC1-positive non-small cell lung cancer (NSCLC) that was refractory to standard anticancer therapies, every 2 weeks. The effectiveness and tolerability of the vaccine were evaluated, and predictive biomarkers of clinical responses were explored.

RESULTS

Between August 2005 and May 2015, 40 patients received the vaccines. The median survival time (MST) after the initial vaccination was 7.4 months, and the 1-year survival rate was 25.0%. The MST for patients who received more than six vaccinations was 9.5 months, and the 1-year survival rate was 39.3%. In this cohort, patients who experienced immune-related adverse events, including skin reactions at the vaccination site and fever, had significantly longer survival times compared with patients without those immune-related adverse events (12.6 versus 6.7 months, p = 0.042). Longer survival times were also observed in patients whose peripheral white blood cells contained >20.0% lymphocytes (12.6 versus 4.5 months; p = 0.014). MUC1-specific cytotoxic immune responses were achieved in all of seven patients analyzed who received six vaccinations.

CONCLUSION

The MUC1-targeted DC-based vaccine induced an antitumor immune response that promoted prolonged survival of patients with refractory NSCLC. The occurrence of immune-related adverse events and having a higher percentage of peripheral lymphocytes were predictive biomarkers of a beneficial clinical response during cancer immunotherapy for NSCLC.

Tools and methods for identification and analysis of rare antigen-specific T lymphocytes

T lymphocytes are essential as effector and memory cells for immune defense against infections and as regulatory T cells in the establishment and maintenance of immune tolerance. However, they are also involved in immune pathology being effectors in autoimmune and allergic diseases or suppressors of immunity in cancer, and they often cause problems in transplantation. Therefore, strategies are being developed that allow the in vivo amplification or isolation, in vitro expansion and genetic manipulation of beneficial T cells for adoptive cell therapies or for the tolerization, or elimination of pathogenic T cells. The major goal is to make use of the exquisite antigen specificity of T cells to develop targeted strategies and to develop techniques that allow for the identification and depletion or enrichment of very often rare antigen-specific naïve as well as effector and memory T cells. Such techniques are very useful for immune monitoring of T cell responses in diagnostics and vaccination and for the development of T cell-based assays for the replacement of animal testing in immunotoxicology to identify contact allergens and drugs that cause adverse reactions.

A harmonized approach to intracellular cytokine staining gating: Results from an international multiconsortia proficiency panel conducted by the Cancer Immunotherapy Consortium (CIC/CRI)

Previous results from two proficiency panels of intracellular cytokine staining (ICS) from the Cancer Immunotherapy Consortium and panels from the National Institute of Allergy and Infectious Disease and the Association for Cancer Immunotherapy highlight the variability across laboratories in reported % CD8+ or % CD4+ cytokine-positive cells. One of the main causes of interassay variability in flow cytometry-based assays is due to differences in gating strategies between laboratories, which may prohibit the generation of robust results within single centers and across institutions. To study how gating strategies affect the variation in reported results, a gating panel was organized where all participants analyzed the same set of Flow Cytometry Standard (FCS) files from a four-color ICS assay using their own gating protocol (Phase I) and a gating protocol drafted by consensus from the organizers of the panel (Phase II). Focusing on analysis removed donor, assay, and instrument variation, enabling us to quantify the variability caused by gating alone. One hundred ten participating laboratories applied 110 different gating approaches. This led to high variability in the reported percentage of cytokine-positive cells and consequently in response detection in Phase I. However, variability was dramatically reduced when all laboratories used the same gating strategy (Phase II). Proximity of the cytokine gate to the negative population most impacted true-positive and false-positive response detection. Recommendations are provided for the (1) placement of the cytokine-positive gate, (2) identification of CD4+ CD8+ double-positive T cells, (3) placement of lymphocyte gate, (4) inclusion of dim cells, (5) gate uniformity, and 6) proper adjustment of the biexponential scaling.

mRNA electroporation as a tool for immunomonitoring

Monitoring the immune response is an essential aspect of numerous clinical vaccination trials in order to evaluate the efficacy. In these clinical vaccination trials, peripheral blood mononuclear cells (PBMC) are isolated at different time points from patient blood samples and subsequently cryopreserved to allow batch analysis at a later time point. Here, we present a newly developed short-time assay which allows direct ex vivo analysis of multi-epitope antigen-specific immune responses using mRNA electroporation of cryopreserved PBMC. This novel method is a rapid and elegant tool and will be convenient for monitoring the cellular immune status of patients in clinical vaccination settings.

Individual and Population Quantitative Analyses of Calcium Flux in T-Cells Activated on Functionalized Material Surfaces

We have developed a novel method for activating T-cells on material surfaces that enable individual and population-based analyses of intracellular calcium flux, as a quantitative measure of T-cell receptor engagement. Functionalized material surfaces were created using a plasma-polymerized foundation layer to immobilize stimulatory T-cell ligands, which could induce T-cell receptor-dependent calcium flux in naive T-cells. Real-time confocal microscopic detection and quantification of calcium flux using paired fluorescent ratiometric probes facilitated the tracking and analysis of response profiles of individual T-cells, as well as population analyses using a combination of individual T-cell events. This type of combined analysis cannot be achieved using traditional population-based flow cytometric approaches, and thus provides a logical step towards developing the capacity to assess the magnitude and quality of inherently heterogeneous effector T-cell responses to antigenic challenge.

Immunotherapy of lung adenocarcinoma patient with Peptide-pulsed dendritic cells: a case report

Immunotherapy with ex vivo generated dendritic cells (DCs) is reported to be of low toxicity and of diverse effectiveness in cancer treatment. The synthetic antigens are frequently used for immunotherapy especially for patients with stable disease after prior treatment. We described the effect of peptide-loaded DCs-based immunotherapy on patient with recurrent surgically resected adenocarcinoma with bronchoalveolar feature with co-existing of Takayasu arteritis and chronic hepatitis B. In January 2010, 61-year-old patient received subcutaneously four bi-weekly vaccinations of DCs loaded with MUC1 and MAGE-3 epitopes. Additionally, he received three bi-weekly booster vaccinations after 7 months from the first course of immunotherapy. Delayed-type hypersensitivity test was positive only for MAGE-3 antigen. The evidence expansion of MAGE-3-specific CD8(+) cells after first vaccination and after third vaccination during boosters injections was observed (from 0.08% before vaccination to 0.5% after first vaccination; from 0.05% before booster vaccination to 0.24% after third injection). Computed tomography scans performed after first course and after booster course of vaccination until April 2011 did not shown any presence of lung tumour or metastases. Based on clinical factors (no completed wedge-resection and recurrent character of cancer) as well as on the presence of the tumour-antigen-specific immunological response, we could speculated that immunotherapy prolonged disease free-survival in our patient. Over 16 months from first vaccination, the patient remains without symptoms of cancer.

Update on vaccine development for renal cell cancer

Renal cell carcinoma (RCC) remains a significant health concern that frequently presents as metastatic disease at the time of initial diagnosis. Current first-line therapeutics for the advanced-stage RCC include antiangiogenic drugs that have yielded high rates of objective clinical response; however, these tend to be transient in nature, with many patients becoming refractory to chronic treatment with these agents. Adjuvant immunotherapies remain viable candidates to sustain disease-free and overall patient survival. In particular, vaccines designed to optimize the activation, maintenance, and recruitment of specific immunity within or into the tumor site continue to evolve. Based on the integration of increasingly refined immunomonitoring systems in both translational models and clinical trials, allowing for the improved understanding of treatment mechanism(s) of action, further refined (combinational) vaccine protocols are currently being developed and evaluated. This review provides a brief history of RCC vaccine development, discusses the successes and limitations in such approaches, and provides a rationale for developing combinational vaccine approaches that may provide improved clinical benefits to patients with RCC.

Changes in cytokine and biomarker blood levels in patients with colorectal cancer during dendritic cell-based vaccination

INTRODUCTION. Immunotherapy based on dendritic cell vaccination has exciting perspectives for treatment of cancer. In order to clarify immunological mechanisms during vaccination it is essential with intensive monitoring of the responses. This may lead to optimization of treatment and prediction of responding patients. The aim of this study was to evaluate cytokine and biomarker responses in patients with colorectal cancer treated with a cancer vaccine based on dendritic cells pulsed with an allogeneic melanoma cell lysate. MATERIAL AND METHODS. Plasma and serum samples were collected prior to vaccination and continuously during treatment. GM-CSF, IL-2, IL-6, TNF-alpha, IFN-gamma, IL-4, IL-8, IL-1b, IL-5, IL-10, IL-12, MIP-1b, IP-10 and Eotaxin were analyzed in a multiplex assay with a Luminex 100 instrument. CEA and TIMP-1 were analysed on ELISA platforms. RESULTS. Patients achieving stable disease showed increasing levels of plasma GM-CSF, TNF-alpha, IFN-gamma, IL-2, and IL-5. Patients with progressive disease showed significant increase in CEA and TIMP-1 levels, while patients with stable disease showed relatively unaltered levels. CONCLUSION. The increased levels of key pro-inflammatory cytokines in serum of patients who achieved stable disease following vaccination suggest the occurrence of vaccine-induced Th1 responses. Since Th1 responses seem to be essential in cancer immunotherapy this may indicate a therapeutic potential of the vaccine.

Postoperative adjuvant dendritic cell-based immunotherapy in patients with relapsed glioblastoma multiforme

PURPOSE

To investigate the therapeutic role of adjuvant vaccination with autologous mature dendritic cells (DC) loaded with tumor lysates derived from autologous, resected glioblastoma multiforme (GBM) at time of relapse.

EXPERIMENTAL DESIGN

Fifty-six patients with relapsed GBM (WHO grade IV) were treated with at least three vaccinations. Children and adults were treated similarly in three consecutive cohorts, with progressively shorter vaccination intervals per cohort. Feasibility and toxicity were assessed as well as effect of age, extent of resection, Karnofsky Performance Score, and treatment cohort on the progression-free (PFS) and overall survival (OS) using univariable and multivariable analysis.

RESULTS

Since the prevaccine reoperation, the median PFS and OS of the total group was 3 and 9.6 months, respectively, with a 2-year OS of 14.8%. Total resection was a predictor for better PFS both in univariable analysis and after correction for the other covariates. For OS, younger age and total resection were predictors of a better outcome in univariable analysis but not in multivariable analysis. A trend to improved PFS was observed in favor of the faster DC vaccination schedule with tumor lysate boosting. Vaccine-related edema in one patient with gross residual disease before vaccination was the only serious adverse event.

CONCLUSION

Adjuvant DC-based immunotherapy for patients with relapsed GBM is safe and can induce long-term survival. A trend to PFS improvement was shown in the faster vaccination schedule. The importance of age and a minimal residual disease status at the start of the vaccination is underscored.

Results and harmonization guidelines from two large-scale international Elispot proficiency panels conducted by the Cancer Vaccine Consortium (CVC/SVI)

The Cancer Vaccine Consortium of the Sabin Vaccine Institute (CVC/SVI) is conducting an ongoing large-scale immune monitoring harmonization program through its members and affiliated associations. This effort was brought to life as an external validation program by conducting an international Elispot proficiency panel with 36 laboratories in 2005, and was followed by a second panel with 29 participating laboratories in 2006 allowing for application of learnings from the first panel. Critical protocol choices, as well as standardization and validation practices among laboratories were assessed through detailed surveys. Although panel participants had to follow general guidelines in order to allow comparison of results, each laboratory was able to use its own protocols, materials and reagents. The second panel recorded an overall significantly improved performance, as measured by the ability to detect all predefined responses correctly. Protocol choices and laboratory practices, which can have a dramatic effect on the overall assay outcome, were identified and lead to the following recommendations: (A) Establish a laboratory SOP for Elispot testing procedures including (A1) a counting method for apoptotic cells for determining adequate cell dilution for plating, and (A2) overnight rest of cells prior to plating and incubation, (B) Use only pre-tested serum optimized for low background: high signal ratio, (C) Establish a laboratory SOP for plate reading including (C1) human auditing during the reading process and (C2) adequate adjustments for technical artifacts, and (D) Only allow trained personnel, which is certified per laboratory SOPs to conduct assays. Recommendations described under (A) were found to make a statistically significant difference in assay performance, while the remaining recommendations are based on practical experiences confirmed by the panel results, which could not be statistically tested. These results provide initial harmonization guidelines to optimize Elispot assay performance to the immunotherapy community. Further optimization is in process with ongoing panels.

A novel peptide-nucleotide dual vaccine of human telomerase reverse transcriptase induces a potent cytotoxic T-cell response in vivo

Human telomerase reverse transcriptase (hTERT) is highly expressed in over 85% of human cancers, which makes it a broadly applicable molecular target for cancer therapy. Several groups have demonstrated that hTERT can efficiently evoke specific cytotoxic T lymphocytes (CTL) responses for malignant tumors. In the present study, we developed a novel virus-like particulate peptide-nucleotide dual vaccine (PNDV) of hTERT, which was composed of a low-affinity epitope variant with encoding full-length gene in the same virus-size particulate. We verified the formation of PNDV by DNA retarding assay, DNase I protection assay and transmission electron microscopy, and confirmed its immunogenicity and transfection activities in mammalian cells. Furthermore, in vivo immunization of HLA-A2.1 transgenic mice generated efficient IFN-gamma secretion and hTERT-specific CTLs which are known to cause selective cell death of telomerase positive gastrointestinal cancer cells. To our knowledge, this represents the first report on collocating a low-affinity epitope variant with a full-length hTERT gene for anti-cancer vaccine design. This novel strategy for vaccine design not only enables enhanced immunity to a universal tumor antigen, but also has the potential to generate CTLs effective in telomerase-positive tumor cells of diverse tissue origins. Therefore, our findings bear significant implications for immunotherapy of human cancers.

A reproducible method for the enumeration of functional (cytokine producing) versus non-functional peptide-specific cytotoxic T lymphocytes in human peripheral blood

One of the most difficult laboratory challenges in the field of therapeutic cancer vaccines has been the development of uncomplicated/reproducible methods for the quantification of vaccine immunization efficacy in peripheral blood of cancer patients. Existing methods are limited by lack of functional information (tetramers), difficulties with standardization/reproducibility [enzyme-linked immunosorbent spot (ELISPOT)] and reliance on endogenous (sample-specific) antigen presentation (cytokine flow cytometry). Herein we present a reproducible method utilizing an artificial antigen-presenting cell platform for flow cytometry-based quantification of the frequency and activation status of peptide-specific cytotoxic T lymphocytes. The methodology [currently presented for cytomegalovirus human leucocyte antigen (HLA)-A2 cognant peptide antigens] allows simultaneous ex vivo quantification of activated (cytokine-producing) and inactive tetramer-positive T cells following HLA class I/peptide/CD28 stimulation independent of endogenous antigen presentation. The simplicity and reliability of the assay provide for high-throughput applications and automation. The utility and application of this method are discussed.

A comparison of standard immunogenicity assays for monitoring HIV type 1 gag-specific T cell responses in Ad5 HIV Type 1 gag vaccinated human subjects

Currently, there are numerous candidate HIV vaccines aimed at inducing T-cell mediated immune responses against HIV. To assess the immunogenicity of such vaccines, a reliable T cell assay must be utilized and typically one of the following assays is chosen for this purpose: bulk culture CTL, MHC I tetramer staining, IFN-gamma ELISPOT, or IFN-gamma intracellular cytokine staining. In this paper we report a comparison of the T cell responses detected by each assay in a large cohort of healthy normal volunteers vaccinated with adenovirus serotype 5 expressing HIV gag. Using stringently validated formats of each of these assays and pools of overlapping HIV gag peptides, we demonstrate that there is a high degree of correlation between all four of the common T cell assays, but inherent differences in the sensitivity of each assay to detect responders. In this study, the ELISPOT assay is shown to have the greatest sensitivity in detecting vaccine responses, while the ICS assay, although less sensitive, has the advantage of providing additional information on the phenotype of the responding cells.

HLA class I mono-specific APCs and target cells: A method to standardise in vitro CD8+ T cell expansion and functional assays

The introduction of in vitro T cell expansion and assay methods that are robust and easy to use would be welcome in cancer vaccine and infectious disease research. By coating HLA class I--ve B cells with recombinant HLA class I peptide complexes, we are able to produce antigen presenting cells and target cells expressing a single defined antigen in the context of costimulatory and adhesion molecules. HLA class I mono-specific cells promoted the in vitro expansion of CMV epitope specific CD8+ T cells from 0.03% to 30.6% in 2 weeks, which was comparable to using peptide-loaded dendritic cells. The HLA class I mono-specific cells were also shown to promote in vitro antigen specific T cell function in assays based on measuring cytokine production and cytolytic activity. HLA class I mono-specific cells are simple to prepare, can be used with any recombinant HLA class I allele/peptide combination and should provide a useful system for in vitro T cell expansion and functional analysis.

Adenovirus as vehicle for anticancer genetic immunotherapy

Adenoviruses (Ads) are in the forefront of genetic immunization methods being developed against cancer. Their ability to elicit an effective immune response against tumor-associated antigens has been demonstrated in many model systems. Several clinical trials, which use Ad as vehicle for immunization, are already in progress. Preclinical studies have also demonstrated the efficacy of combining Ad-mediated immunization with adjuvants such as chemotherapeutic agents and cytokines. Issues related to sero-prevalence and safety of Ads, however, continue to pose a challenge and need to be addressed.