Ii-Key/HER-2/neu(776-790) hybrid peptides induce more effective immunological responses over the native peptide in lymphocyte cultures from patients with HER-2/neu+ tumors

HER2/neu-based vaccination with li-Key hybrid, GM-CSF immunoadjuvant and trastuzumab as a potent triple-negative breast cancer treatment

PURPOSE

Constituting 15 to 20% of breast cancer cases, the triple-negative subtype lacks effective treatments as being less responsive to hormone-associated therapies. Alternatively, a more powerful immunotherapeutic vaccination can trigger immune recognition and destruction against breast cancer by incorporating oncological antigens such as human epidermal growth factor receptor 2 (HER2/neu). Currently, HER2/neu-based vaccines have finished three phases with breast cancer patients, in conjunction with granulocyte-macrophage colony-stimulating factor (GM-CSF) that was proven to be a promising vaccine adjuvant in other cancer trials previously.

METHODS

Completed HER2/neu-based vaccine trials with GM-CSF immunoadjuvants for breast cancer were summarised, and additionally, the article discussed prominent findings of vaccine effectiveness in triple-negative breast cancer, regarding li-Key hybrid in vaccine design and co-administration of anti-HER2/neu trastuzumab.

RESULTS

Nine clinical trials of three HER2/neu epitopes, one with li-Key hybrid, were analysed with or without the presence of trastuzumab. Immunological responses and minimal toxicities were observed in these epitopes, and disease-free survival was especially improved in the triple-negative population.

CONCLUSION

HER2/neu-based peptide vaccine is a safe and effective approach against breast cancer, and its benefits can be potentially furthered by combining the li-Key hybrid vaccine with targeted drugs and adjuvants selected to enhance cross-presentation for exogenous vaccine antigens. Graphical abstract was created with Biorender.com (license number: HA24UHRBV4 and FP24UHRGDD).

Frequencies of an Immunogenic HER-2/neu Epitope of CD8+ T Lymphocytes Predict Favorable Clinical Outcomes in Prostate Cancer

HER-2/neu is the human epidermal growth factor receptor 2, which is associated with the progression of prostate cancer (PCa). HER-2/neu-specific T cell immunity has been shown to predict immunologic and clinical responses in PCa patients treated with HER-2/neu peptide vaccines. However, its prognostic role in PCa patients receiving conventional treatment is unknown, and this was addressed in this study. The densities of CD8+ T cells specific for the HER-2/neu_(780-788) peptide in the peripheral blood of PCa patients under standard treatments were correlated with TGF-β/IL-8 levels and clinical outcomes. We demonstrated that PCa patients with high frequencies of HER-2/neu_(780-788)-specific CD8+ T lymphocytes had better progression-free survival (PFS) as compared with PCa patients with low frequencies. Increased frequencies of HER-2/neu_(780-788)-specific CD8+ T lymphocytes were also associated with lower levels of TGF-β and IL-8. Our data provide the first evidence of the predictive role of HER-2/neu-specific T cell immunity in PCa.

Cancer Vaccines for Triple-Negative Breast Cancer: A Systematic Review

Triple-negative breast cancer (TNBC) is the subtype of breast cancer with the poorest outcomes, and is associated with a high risk of relapse and metastasis. The treatment choices for this malignancy have been confined to conventional chemotherapeutic agents, due to a lack of expression of the canonical molecular targets. Immunotherapy has been recently changing the treatment paradigm for many types of tumors, and the approach of evoking active immune responses in the milieu of breast tumors through cancer vaccines has been introduced as one of the most novel immunotherapeutic approaches. Accordingly, a number of vaccines for the treatment or prevention of recurrence have been developed and are currently being studied in TNBC patients, while none have yet received any approvals. To elucidate the efficacy and safety of these vaccines, we performed a systematic review of the available literature on the topic. After searching the PubMed, Scopus, Web of Science, Embase, Cochrane CENTRAL, and Google Scholar databases, a total of 5701 results were obtained, from which 42 clinical studies were eventually included based on the predefined criteria. The overall quality of the included studies was acceptable. However, due to a lack of reporting outcomes of survival or progression in some studies (which were presented as conference abstracts) as well as the heterogeneity of the reported outcomes and study designs, we were not able to carry out a meta-analysis. A total of 32 different vaccines have so far been evaluated in TNBC patients, with the majority belonging to the peptide-based vaccine type. The other vaccines were in the cell or nucleic acid (RNA/DNA)-based categories. Most vaccines proved to be safe with low-grade, local adverse events and could efficiently evoke cellular immune responses; however, most trials were not able to demonstrate significant improvements in clinical indices of efficacy. This is in part due to the limited number of randomized studies, as well as the limited TNBC population of each trial. However, due to the encouraging results of the currently published trials, we anticipate that this strategy could show its potential through larger, phase III randomized studies in the near future.

Prostate Cancer Biomarkers: From diagnosis to prognosis and precision-guided therapeutics

Prostate cancer (PCa) is one of the most commonly diagnosed malignancies and among the leading causes of cancer-related death worldwide. It is a highly heterogeneous disease, ranging from remarkably slow progression or inertia to highly aggressive and fatal disease. As therapeutic decision-making, clinical trial design and outcome highly depend on the appropriate stratification of patients to risk groups, it is imperative to differentiate between benign versus more aggressive states. The incorporation of clinically valuable prognostic and predictive biomarkers is also potentially amenable in this process, in the timely prevention of metastatic disease and in the decision for therapy selection. This review summarizes the progress that has so far been made in the identification of the genomic events that can be used for the classification, prediction and prognostication of PCa, and as major targets for clinical intervention. We include an extensive list of emerging biomarkers for which there is enough preclinical evidence to suggest that they may constitute crucial targets for achieving significant advances in the management of the disease. Finally, we highlight the main challenges that are associated with the identification of clinically significant PCa biomarkers and recommend possible ways to overcome such limitations.

Immunotherapy as a Precision Medicine Tool for the Treatment of Prostate Cancer

Prostate cancer (PCa) is the most frequently diagnosed type of cancer among Caucasian males over the age of 60 and is characterized by remarkable heterogeneity and clinical behavior, ranging from decades of indolence to highly lethal disease. Despite the significant progress in PCa systemic therapy, therapeutic response is usually transient, and invasive disease is associated with high mortality rates. Immunotherapy has emerged as an efficacious and non-toxic treatment alternative that perfectly fits the rationale of precision medicine, as it aims to treat patients on the basis of patient-specific, immune-targeted molecular traits, so as to achieve the maximum clinical benefit. Antibodies acting as immune checkpoint inhibitors and vaccines entailing tumor-specific antigens seem to be the most promising immunotherapeutic strategies in offering a significant survival advantage. Even though patients with localized disease and favorable prognostic characteristics seem to be the ones that markedly benefit from such interventions, there is substantial evidence to suggest that the survival benefit may also be extended to patients with more advanced disease. The identification of biomarkers that can be immunologically targeted in patients with disease progression is potentially amenable in this process and in achieving significant advances in the decision for precision treatment of PCa.

AE37: a HER2-targeted vaccine for the prevention of breast cancer recurrence

INTRODUCTION

HER2 is a prevalent growth factor in a variety of malignancies, most prominently breast cancer. Over-expression has been correlated with the poorest overall survival and has been the target of successful therapies such as trastuzumab. AE37 is a novel, HER2-directed vaccine based on the AE36 hybrid peptide (aa776-790), which is derived from the intracellular portion of the HER2 protein, and the core portion of the MHC Class II invariant chain (the Ii-Key peptide). This hybrid peptide is given with GM-CSF immunoadjuvant as the AE37 vaccine.

AREAS COVERED

This article describes in detail the preclinical science leading to the creation of the AE37 vaccine and examines use of this agent in multiple clinical trials for breast and prostate cancer. The safety profile of AE37 is discussed and opinions on the potential of the vaccine in breast and prostate cancer patient subsets along with other malignancies, are offered.

EXPERT OPINION

Future trials utilizing the AE37 vaccine to treat other HER2-expressing malignancies are likely to see similar success, and this will be enhanced by combination immunotherapy. Ii-Key modification of other peptides of interest across oncology and virology could yield impressive results over the longer term.

Prospective, randomized, single-blinded, multi-center phase II trial of two HER2 peptide vaccines, GP2 and AE37, in breast cancer patients to prevent recurrence

Purpose

AE37 and GP2 are HER2 derived peptide vaccines. AE37 primarily elicits a CD4+ response while GP2 elicits a CD8+ response against the HER2 antigen. These peptides were tested in a large randomized trial to assess their ability to prevent recurrence in HER2 expressing breast cancer patients. The primary analyses found no difference in 5-year overall disease-free survival (DFS) but possible benefit in subgroups. Here, we present the final landmark analysis.

Methods

In this 4-arm, prospective, randomized, single-blinded, multi-center phase II trial, disease-free node positive and high-risk node negative breast cancer patients enrolled after standard of care therapy. Six monthly inoculations of vaccine (VG) vs. control (CG) were given as the primary vaccine series with 4 boosters at 6-month intervals. Demographic, safety, immunologic, and DFS data were evaluated.

Results

456 patients were enrolled; 154 patients in the VG and 147 in CG for AE37, 89 patients in the VG and 91 in CG for GP2. The AE37 arm had no difference in DFS as compared to CG, but pre-specified exploratory subgroup analyses showed a trend towards benefit in advanced stage (p = 0.132, HR 0.573 CI 0.275–1.193), HER2 under-expression (p = 0.181, HR 0.756 CI 0.499–1.145), and triple-negative breast cancer (p = 0.266, HR 0.443 CI 0.114–1.717). In patients with both HER2 under-expression and advanced stage, there was significant benefit in the VG (p = 0.039, HR 0.375 CI 0.142–0.988) as compared to CG. The GP2 arm had no significant difference in DFS as compared to CG, but on subgroup analysis, HER2 positive patients had no recurrences with a trend toward improved DFS (p = 0.052) in VG as compared to CG.

Conclusions

This phase II trial reveals that AE37 and GP2 are safe and possibly associated with improved clinical outcomes of DFS in certain subgroups of breast cancer patients. With these findings, further evaluations are warranted of AE37 and GP2 vaccines given in combination and/or separately for specific subsets of breast cancer patients based on their disease biology.

The balance between breast cancer and the immune system: Challenges for prognosis and clinical benefit from immunotherapies

Cancer evolution is a complex process influenced by genetic factors and extracellular stimuli that trigger signaling pathways to coordinate the continuous and dynamic interaction between tumor cells and the elements of the immune system. For over 20 years now, the immune mechanisms controlling cancer progression have been the focus of intensive research. It is well established that the immune system conveys protective antitumor immunity by destroying immunogenic tumor variants, but also facilitates tumor progression by shaping tumor immunogenicity in a process called "immunoediting". It is also clear that immune-guided tumor editing is associated with tumor evasion from immune surveillance and therefore reinforcing the endogenous antitumor immunity is a desired goal in the context of cancer therapies. The tumor microenvironment (TME) is a complex network which consists of various cell types and factors having important roles regarding tumor development and progression. Tumor infiltrating lymphocytes (TILs) and other tumor infiltrating immune cells (TIICs) are key to our understanding of tumor immune surveillance based on tumor immunogenicity, whereby the densities and location of TILs and TIICs in the tumor regions, as well as their functional programs (comprising the "immunoscore") have a prominent role for prognosis and prediction for several cancers. The presence of tertiary lymphoid structures (TLS) in the TME or in peritumoral areas has an influence on the locally produced antitumor immune response, and therefore also has a significant prognostic impact. The cross-talk between elements of the immune system with tumor cells in the TME is greatly influenced by hypoxia, the gut and/or the local microbiota, and several metabolic elements, which, in a dynamic interplay, have a crucial role for tumor cell heterogeneity and reprogramming of immune cells along their activation and differentiation pathways. Taking into consideration the recent clinical success with the application immunotherapies for the treatment of several cancer types, increasing endeavors have been made to gain better insights into the mechanisms underlying phenotypic and metabolic profiles in the context of tumor progression and immunotherapy. In this review we will address (i) the role of TILs, TIICs and TLS in breast cancer (BCa); (ii) the different metabolic-based pathways used by immune and breast cancer cells; and (iii) implications for immunotherapy-based strategies in BCa.

HER2-Based Immunotherapy for Breast Cancer

Resistance to therapies and disease recurrences after surgery or treatment are common challenges in breast cancer management in clinic. Active immunotherapy using human epidermal growth factor receptor 2 (HER2)-targeted vaccines represents an attractive option in combating breast cancer. Different HER2-derived vaccines have been developed over the years. Many clinical trials have been carried out in evaluating HER2-based vaccines. The authors reviewed current literature on HER2-based vaccines in clinical trials. The trials covered in this mini-review represent some of the major trials published in the past 20 years regarding the clinical use and test of HER2 vaccines. Their focus is on trials using HER2 peptide vaccines as the majority of clinical trials initiated or published used HER2 peptide-based vaccines. Findings from combination therapy trials of HER2 peptide vaccines with other treatment modalities are also presented.

Immunogenicity and antitumor activity of the superlytic λF7 phage nanoparticles displaying a HER2/neu-derived peptide AE37 in a tumor model of BALB/c mice

Phage display technique has been increasingly researched for vaccine design and delivery strategies in recent years. In this study, the AE37 (Ii-Key/HER-2/neu 776-790) peptide derived from HER2 (human epidermal growth factor receptor protein) was used as a fused peptide to the lambda phage (λF7) coat protein gpD, and the phage nanoparticles were used to induce antitumor immunogenicity in a TUBO model of breast cancer in mice. Mice were immunized with the AE37 peptide displaying phage, λF7 (gpD::AE37) every 2-week intervals over 6-weeks, then the generated immune responses were evaluated. An induction of CTL immune response by the λF7 (gpD::AE37) construct compared to the control λF7 and buffer groups was observed in vitro. Moreover, in the in vivo studies, the vaccine candidate showed promising prophylactic and therapeutic effects against the HER2 overexpressing cancer in BALB/c mice.

Immunotherapy for breast cancer: past, present, and future

Immunotherapy has shown promise in many solid tumors including melanoma and non-small cell lung cancer with an evolving role in breast cancer. Immunotherapy encompasses a wide range of therapies including immune checkpoint inhibition, monoclonal antibodies, bispecific antibodies, vaccinations, antibody-drug conjugates, and identifying other emerging interventions targeting the tumor microenvironment. Increasing efficacy of these treatments in breast cancer patients requires identification of better biomarkers to guide patient selection; recognizing when to initiate these therapies in multi-modality treatment plans; establishing novel assays to monitor immune-mediated responses; and creating combined systemic therapy options incorporating conventional treatments such as chemotherapy and endocrine therapy. This review will focus on the current role and future directions of many of these immunotherapies in breast cancer, as well as highlighting clinical trials that are investigating several of these active issues.

Unraveling the role of preexisting immunity in prostate cancer patients vaccinated with a HER-2/neu hybrid peptide

Background

Cancer vaccines aim at eliciting not only an immune response against specific tumor antigens, but also at enhancing a preexisting immunity against the tumor. In this context, we recently reported on the levels of preexisting immunity in prostate cancer patients vaccinated with the HER-2 hybrid peptide (AE37), during a phase I clinical trial. The purpose of the current study was to correlate between preexisting immunity to the native HER-2 peptide, AE36, and expression of HLA-A2 and -A24 molecules with the clinical outcome. Additionally, we investigated the ability of the AE37 vaccine to induce an antitumor immune response against other tumor associated antigens, not integrated in the vaccine formulation, with respect to the clinical response.

Methods

We analyzed prostate cancer patients who were vaccinated with the AE37 vaccine [Ii-Key-HER-2/neu_(776–790) hybrid peptide vaccine (AE37), which is a MHC class II long peptide vaccine encompassing MHC class I epitopes, during a phase I clinical trial. Preexisting immunity to the native HER-2/neu_(776–790) (AE36) peptide was assessed by IFNγ response or dermal reaction at the inoculation site. Antigen specificity against other tumor antigens was defined using multimer analysis. Progression free survival (PFS) was considered as the patients’ clinical outcome. Two-tailed Wilcoxon signed rank test at 95 % confidence interval was used for statistical evaluation at different time points and Kaplan–Meier curves with log-rank (Mantel-Cox) test were used for the evaluation of PFS.

Results

Preexisting immunity to AE36, irrespectively of HLA expression, was correlated with longer PFS. Specific CD8⁺ T cell immunity against E75 and PSA_146–151 (HLA-A2 restricted), as well as, PSA_153–161 (HLA-A24 restricted) was detected at relatively high frequencies which were further enhanced during vaccinations. Specific immunity against PSA_153–161 correlated with longer PFS in HLA-A24⁺ patients. However, HLA-A2⁺ patients with high preexisting or vaccine-induced immunity to E75, showed a trend for shorter PFS.

Conclusions

Our data cast doubt on whether preexisting immunity or epitope spreading specific for HLA-class I-restricted peptides can actually predict a favorable clinical outcome. They also impose that preexisting immunity to long vaccine peptides, encompassing both HLA class II and I epitopes should be considered as an important prerequisite for the improvement of future immunotherapeutic protocols.

Protocol ID Code: Generex-06-07

National Organization for Medicines (EOF) ID Code: IS-107-01-06

NEC Study Code: EED107/1/06

EudraCT Number: 2006-003299-37

Date of registration: 07/06/2006

Date of enrolment of the first participant to the trial: Nov 1st, 2007

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-016-0183-4) contains supplementary material, which is available to authorized users.

Primary analysis of a prospective, randomized, single-blinded phase II trial evaluating the HER2 peptide AE37 vaccine in breast cancer patients to prevent recurrence

BACKGROUND

AE37 is the Ii-Key hybrid of the MHC class II peptide, AE36 (HER2 aa:776-790). Phase I studies showed AE37 administered with granulocyte macrophage colony-stimulating factor (GM-CSF) to be safe and highly immunogenic. A prospective, randomized, multicenter phase II adjuvant trial was conducted to evaluate the vaccine's efficacy.

METHODS

Clinically disease-free node-positive and high-risk node-negative breast cancer patients with tumors expressing any degree of HER2 [immunohistochemistry (IHC) 1-3+] were enrolled. Patients were randomized to AE37 + GM-CSF versus GM-CSF alone. Toxicity was monitored. Clinical recurrences were documented and disease-free survival (DFS) analyzed.

RESULTS

The trial enrolled 298 patients; 153 received AE37 + GM-CSF and 145 received GM-CSF alone. The groups were well matched for clinicopathologic characteristics. Toxicities have been minimal. At the time of the primary analysis, the recurrence rate in the vaccinated group was 12.4% versus 13.8% in the control group [relative risk reduction 12%, HR 0.885, 95% confidence interval (CI) 0.472-1.659, P = 0.70]. The Kaplan-Meier estimated 5-year DFS rate was 80.8% in vaccinated versus 79.5% in control patients. In planned subset analyses of patients with IHC 1+/2+ HER2-expressing tumors, 5-year DFS was 77.2% in vaccinated patients (n = 76) versus 65.7% in control patients (n = 78) (P = 0.21). In patients with triple-negative breast cancer (HER2 IHC 1+/2+ and hormone receptor negative) DFS was 77.7% in vaccinated patients (n = 25) versus 49.0% in control patients (n = 25) (P = 0.12).

CONCLUSION

The overall intention-to-treat analysis demonstrates no benefit to vaccination. However, the results confirm that the vaccine is safe and suggest that vaccination may have clinical benefit in patients with low HER2-expressing tumors, specifically TNBC. Further evaluation in a randomized trial enrolling TNBC patients is warranted.

Peptide-Based Cancer Vaccine Strategies and Clinical Results

Active cancer immunotherapy is an exciting and developing field in oncology research. Peptide vaccines, the use of isolated immunogenic tumor-associated antigen (TAA) epitopes to generate an anticancer immune response, are an attractive option as they are easily produced and administered with minimal toxicity. Multiple TAA-derived peptides have been identified and evaluated with various vaccine strategies currently in clinical testing. Research suggests that utilizing vaccines in patients with minimal-residual disease may be a more effective strategy compared to targeting patients with widely metastatic disease as it avoids the immune suppression and tolerance associated with higher volumes of more established disease. Clinical trials also suggest that vaccines may need to be tailored and administered to specific cancer subtypes to achieve maximum efficacy. Additionally, numerous immunomodulators now in research and development show potential synergy with peptide vaccines. Our group has focused on a simpler, single-peptide strategy largely from the HER2/neu protein. We will discuss our experience thus far as well as review other peptide vaccine strategies that have shown clinical efficacy.

Adjuvant HER2/neu peptide cancer vaccines in breast cancer

Active cancer immunotherapy remains an exciting and rapidly advancing field in oncology. Peptide cancer vaccines are an attractive therapeutic option as they are safe and easily produced and administered. Peptide cancer vaccines may be most effective in patients with a lower disease burden, when cancer tolerance is minimized. Our experience with three peptide cancer vaccines, E75, GP2 and AE37, in clinically disease-free breast cancer patients provides encouraging results that this method may be effective. Furthermore, the combined results of the initial trials suggest that the vaccine administered may need to be tailored to the specific subtype of cancer and tumor antigen expression level to achieve maximum effectiveness. The results also suggest that combining peptide vaccines with other immunotherapy may lead to a synergistic effect.

Improving Multi-Epitope Long Peptide Vaccine Potency by Using a Strategy that Enhances CD4+ T Help in BALB/c Mice

Peptide-based vaccines are attractive approaches for cancer immunotherapy; but the success of these vaccines in clinical trials have been limited. Our goal is to improve immune responses and anti-tumor effects against a synthetic, multi-epitope, long peptide from rat Her2/neu (rHer2/neu) using the help of CD4+ T cells and appropriate adjuvant in a mouse tumor model. Female BALB/c mice were vaccinated with P₅₊₄₃₅ multi-epitope long peptide that presents epitopes for cytotoxic T lymphocytes (CTL) in combination with a universal Pan DR epitope (PADRE) or CpG-oligodeoxynucleotides (CpG-ODNs) as a Toll-like receptor agonist adjuvant. The results show that vaccination with the multi-epitope long peptide in combination with the PADRE peptide and CpG-ODN induced expansion of subpopulations of CD4+ and CD8+ cells producing IFN-γ, the average tumor size in the vaccinated mice was less than that of the other groups, and tumor growth was inhibited in 40% of the mice in the vaccinated group. The mean survival time was 82.6 ± 1.25 days in mice vaccinated with P₅₊₄₃₅ + CpG+ PADRE. Our results demonstrate that inclusion of PADRE and CpG with the peptide vaccine enhanced significant tumor specific-immune responses in vaccinated mice.

A pilot study in prostate cancer patients treated with the AE37 Ii-key-HER-2/neu polypeptide vaccine suggests that HLA-A*24 and HLA-DRB1*11 alleles may be prognostic and predictive biomarkers for clinical benefit

Recently, several types of immunotherapies have been shown to induce encouraging clinical results, though in a restricted number of patients. Consequently, there is a need to identify immune biomarkers to select patients who will benefit from such therapies. Such predictive biomarkers may be also used as surrogates for overall survival (OS). We have recently found correlations between immunologic parameters and clinical outcome in prostate cancer patients who had been vaccinated with a HER-2/neu hybrid polypeptide vaccine (AE37) and received one booster 6 months post-primary vaccinations. Herein, we aimed to expand these retrospective analyses by studying the predictive impact of HLA-A*24 and HLA-DRB1*11 alleles, which are expressed at high frequencies among responders in our vaccinated patients, for clinical and immunological responses to AE37 vaccination. Our data show an increased OS of patients expressing the HLA-DRB1*11 or HLA-A*24 alleles, or both. Vaccine-induced immunological responses, measured as interferon γ (IFN-γ) responses in vitro or delayed-type hypersensitivity reactions in vivo, were also higher in these patients and inversely correlated with suppressor elements. Preexisting (i.e., before vaccinations with AE37) levels of vaccine-specific IFN-γ immunity and plasma TGF-β, among the HLA-A*24 and/or HLA-DRB1*11 positive patients, were strong indicators for immunological responses to AE37 treatment. These data suggest that HLA-DRB1*11 and HLA-A*24 are likely to be predictive factors for immunological and clinical responses to vaccination with AE37, though prospective validation in larger cohorts is needed.

AE37 peptide vaccination in prostate cancer: identification of biomarkers in the context of prognosis and prediction

A fundamental challenge in administering immunotherapies for cancer is the establishment of biomarkers that can predict patients' responsiveness to treatment. In this study, our aim was to predict the immunologic and clinical responses of vaccination therapy with an Ii-key-modified HER-2/neu peptide (Ii-key/HER-2(776-790) or AE37), applied in our recent phase I study in patients with prostate cancer. To this end, we retrospectively analyzed our data derived from immunologic determinations before, during and after primary series of vaccinations with AE37, as well as after one AE37 booster injection. Using the obtained data, we then observed the relationship between the immunologic parameters and clinical outcome of patients. We found that preexisting levels of transforming growth factor beta (TGF-β) had an inverse correlation with in vivo and in vitro immunologic responses to the AE37 vaccine which were measured as delayed-type hypersensitivity (DTH) and interferon gamma (IFN-γ) production in response to the native HER-2(776-790) (or AE36) peptide, respectively. Patients with preexistent IFN-γ immunity to AE36 developed positive DTH reactions after primary vaccinations and booster. Moreover, we could detect a direct correlation between IFN-γ production and DTH reactions in response to AE36 challenge in our vaccinated patients. DTH reactions were a stronger indicator for patients' overall survival (OS) than preexistent or vaccine-induced IFN-γ immunity. In contrast, we found that preexisting TGF-β levels were correlated with shorter patients' OS. These retrospective analyses suggest that the above biomarkers at the time-points measured offer promise for evaluating immunologic and clinical responses to AE37-based vaccinations.

Immune biomarkers: how well do they serve prognosis in human cancers?

In order to be optimally efficacious, therapeutic cancer vaccines must induce robust tumor-specific CD8(+) cytotoxic T cells, which are responsible for tumor cell lysis. Unlike cytotoxic drugs, which act directly on the tumor, cancer vaccines demonstrate new kinetics involving the generation of specific cellular immune responses, which need to be translated into antitumor responses to delay tumor progression and improve survival. These delayed kinetics of action establish a new concept of benefit in the long term, which implies a slow down in tumor growth rates, than a marked reduction in tumor size. Therefore, there is a significant need to identify intermediate biomarkers so that clinical responses can be evaluated in a timely manner. Therapeutic vaccination as a modality for cancer treatment has received significant attention with multiple clinical trials demonstrating improvements in overall survival. Significant challenges to this modality remain, including increasing vaccine potency and minimizing treatment-related toxicities and identifying prognostic and predictive biomarkers of clinical benefit that may guide to select and optimize the therapeutic strategies for patients most likely to gain benefit.

Therapeutic cancer vaccines: a long and winding road to success

Harnessing the immune system to achieve therapeutic efficacy in cancer has been a milestone in immuno-oncology. Tumor-induced suppression works as an obstacle for the effectiveness of immunotherapies. Advances in our understanding of the interrelationship between cancer immunoediting and immunotherapy led to successful manipulation of anticancer immunity; this provided the platform for combining cancer vaccines with chemotherapies counteracting, to some extent, tumor-induced suppressive entities and demonstrating clinical efficacy. Targeting co-inhibitory and co-stimulatory receptors with immunostimulatory antibodies has also shown clinical promise and its combined use with vaccines is a promising new approach of immunotherapy for cancer. Recent evidence supporting vaccine administration in patients with early and less aggressive disease should be additionally placed to select the appropriate patient population and to identify earlier markers of clinical benefit and immunological parameters that correlate with survival. This review focuses on promising vaccination platforms and essential perspectives in the treatment of cancer.

Immunologic biomarkers in prostate cancer: the AE37 paradigm

One major achievement in cancer therapy is to select patients who will most likely benefit from a specific treatment. Predictive biomarkers play an important role in this respect being already useful in management of breast cancer and melanoma. For example, HER-2/neu (HER-2) overexpression selects for breast cancer patients to be treated with trastuzumab, and BRAFV600E mutations select for melanoma patients to be treated with vemurafenib. Identification of factors associated with T cell responsiveness to vaccination remains critical. Pre-existent immunity and circulating suppressor cells may regulate the levels of vaccine-specific T cell immunity after vaccination. The identification of immunologic endpoints to immunotherapy would thus considerably help guide the development of immunotherapy-based clinical trials. This commentary is based on a retrospective analysis we performed of data from prostate cancer patients vaccinated and boosted with the AE37 vaccine. The aim of these exploratory analyses was to identify factors useful in predicting which patients are more likely to respond to the treatment under study. The issue we are addressing here is to which extent common variables used pre- and/or following vaccinations with AE37 to assess the immune response status of the prostate cancer patients, may predict overall survival.

Invariant chain-peptide fusion vaccine using HER-2/neu

A novel method for amplifying the activity of major histocompatibility complex (MHC) class II helper epitopes entails linking a 4-amino-acid moiety (LRMK) from the invariant chain (Ii) of MHC (referred to as Ii-Key) to the N-terminal end of the epitope peptide either directly or using a simple polymethylene spacer (-ava-). Ii-Key catalyzes binding of the linked epitope to the MHC class II molecule, thereby enhancing the overall potency of presentation. HER-2(776-790) (or AE36), which is derived from the intracellular domain of HER-2/neu, has been intensively used as an Ii-key/HER-2(776-790) (or AE37) fusion (hybrid) vaccine in clinical trials. This chapter describes procedures for the synthesis, reconstitution, sterility testing, and storage of both AE36 and AE37 for their use in clinical trials. Also provided is a detailed information about their in vivo administration and analysis of in-depth protocols for monitoring of immune activation upon vaccination with AE37.

AE37 peptide vaccination in prostate cancer: a 4-year immunological assessment updates on a phase I trial

In our recent phase I trial, we demonstrated that the AE37 vaccine is safe and induces HER-2/neu-specific immunity in a heterogeneous population of HER-2/neu (+) prostate cancer patients. Herein, we tested whether one AE37 boost can induce long-lasting immunological memory in these patients. Twenty-three patients from the phase I study received one AE37 boost 6-month post-primary vaccinations. Local/systemic toxicities were evaluated following the booster injection. Immunological responses were monitored 1-month (long-term booster; LTB) and 3-year (long-term immunity; LTI) post-booster by delayed-type hypersensitivity, IFN-γ ELISPOT and proliferation assays. Regulatory T cell (Treg) frequencies, plasma transforming growth factor-β (TGF-β) and indoleamine 2,3-deoxygenase (IDO) activity levels were also determined at the same time points. The AE37 booster was safe and well tolerated. Immunological monitoring revealed vaccine-specific long-term immunity in most of the evaluated patients during both LTB and LTI, although individual levels of immunity during LTI were decreased compared with those measured 3 years earlier during LTB. This was paralleled with increased Tregs, TGF-β levels and IDO activity. One AE37 booster generated long-term immunological memory in HER-2/neu (+) prostate cancer patients, which was detectable 3 years later, albeit with a tendency to decline. Boosted patients had favorable clinical outcome in terms of overall and/or metastasis-free survival compared with historical groups with similar clinical characteristics at diagnosis. We suggest that more boosters and/or concomitant disarming of suppressor circuits may be necessary to sustain immunological memory, and therefore, further studies to optimize the AE37 booster schedule are warranted.

Cross-species association of quail invariant chain with chicken and mouse MHC II molecules

There are different degrees of similarity among vertebrate invariant chains (Ii). The aim of this study was to determine the relationship between quail and other vertebrate Ii MHC class II molecules. The two quail Ii isoforms (qIi-1, qIi-2) were cloned by RACE, and qRT-PCR analysis of different organs showed that their expression levels were positively correlated with MHC II gene (B-LB) transcription levels. Confocal microscopy indicated that quail full-length Ii co-localized with MHC II of quail, chicken or mouse in 293FT cells co-transfected with both genes. Immunoprecipitation and western blotting further indicated that these aggregates corresponded to polymers of Ii and MHC class II molecules. This cross-species molecular association of quail Ii with chicken and mouse MHC II suggests that Ii molecules have a high structural and functional similarity and may thereby be used as potential immune carriers across species.

Boosting immune response with the invariant chain segments via association with non-peptide binding region of major histocompatibility complex class II molecules

BACKGROUND

Based on binding of invariant chain (Ii) to major histocompatibility complex (MHC) class II molecules to form complexes, Ii-segment hybrids, Ii-key structure linking an epitope, or Ii class II-associated invariant chain peptide (CLIP) replaced with an epitope were used to increase immune response. It is currently unknown whether the Ii-segment cytosolic and transmembrane domains bind to the MHC non-peptide binding region (PBR) and consequently influence immune response. To investigate the potential role of Ii-segments in the immune response via MHC II/peptide complexes, a few hybrids containing Ii-segments and a multiepitope (F306) from Newcastle disease virus fusion protein (F) were constructed, and their binding effects on MHC II molecules and specific antibody production were compared using confocal microscopy, immunoprecipitation, western blotting and animal experiments.

RESULTS

One of the Ii-segment/F306 hybrids, containing ND (Asn-Asp) outside the F306 in the Ii-key structure (Ii-key/F306/ND), neither co-localized with MHC II molecules on plasma membrane nor bound to MHC II molecules to form complexes. However, stimulation of mice with the structure produced 4-fold higher antibody titers compared with F306 alone. The two other Ii-segment/F306 hybrids, in which the transmembrane and cytosolic domains of Ii were linked to this structure (Cyt/TM/Ii-key/F306/ND), partially co-localized on plasma membrane with MHC class II molecules and weakly bound MHC II molecules to form complexes. They induced mice to produce approximately 9-fold higher antibody titers compared with F306 alone. Furthermore, an Ii/F306 hybrid (F306 substituting CLIP) co-localized well with MHC II molecules on the membrane to form complexes, although it increased antibody titer about 3-fold relative to F306 alone.

CONCLUSIONS

These results suggest that Ii-segments improve specific immune response by binding to the non-PBR on MHC class II molecules and enabling membrane co-localization with MHC II molecules, resulting in the formation of relatively stable MHC II/peptide complexes on the plasma membrane, and signal transduction.

AE37: a novel T-cell-eliciting vaccine for breast cancer

INTRODUCTION

Immunotherapy, including vaccines targeting the human EGFR2 (HER-2/neu) protein, is an active area of investigation in combatting breast cancer. Several vaccines are currently undergoing clinical trials, most of which are CD8(+) T-cell-eliciting vaccines. AE37 is a promising primarily CD4(+) T-cell-eliciting HER-2/neu breast cancer vaccine currently in clinical trials.

AREAS COVERED

This article reviews preclinical investigations as well as findings from completed and ongoing Phase I and Phase II clinical trials of the AE37 vaccine.

EXPERT OPINION

Clinical trials have shown the AE37 vaccine to be safe and capable of generating peptide-specific, durable immune responses. This has been shown in patients with any level of HER-2/neu expression. Early clinical findings suggest there may be benefit to AE37 vaccination in preventing breast cancer recurrence.

Enhanced presentation of MHC class Ia, Ib and class II-restricted peptides encapsulated in biodegradable nanoparticles: a promising strategy for tumor immunotherapy

BACKGROUND

Many peptide-based cancer vaccines have been tested in clinical trials with a limited success, mostly due to difficulties associated with peptide stability and delivery, resulting in inefficient antigen presentation. Therefore, the development of suitable and efficient vaccine carrier systems remains a major challenge.

METHODS

To address this issue, we have engineered polylactic-co-glycolic acid (PLGA) nanoparticles incorporating: (i) two MHC class I-restricted clinically-relevant peptides, (ii) a MHC class II-binding peptide, and (iii) a non-classical MHC class I-binding peptide. We formulated the nanoparticles utilizing a double emulsion-solvent evaporation technique and characterized their surface morphology, size, zeta potential and peptide content. We also loaded human and murine dendritic cells (DC) with the peptide-containing nanoparticles and determined their ability to present the encapsulated peptide antigens and to induce tumor-specific cytotoxic T lymphocytes (CTL) in vitro.

RESULTS

We confirmed that the nanoparticles are not toxic to either mouse or human dendritic cells, and do not have any effect on the DC maturation. We also demonstrated a significantly enhanced presentation of the encapsulated peptides upon internalization of the nanoparticles by DC, and confirmed that the improved peptide presentation is actually associated with more efficient generation of peptide-specific CTL and T helper cell responses.

CONCLUSION

Encapsulating antigens in PLGA nanoparticles offers unique advantages such as higher efficiency of antigen loading, prolonged presentation of the antigens, prevention of peptide degradation, specific targeting of antigens to antigen presenting cells, improved shelf life of the antigens, and easy scale up for pharmaceutical production. Therefore, these findings are highly significant to the development of synthetic vaccines, and the induction of CTL for adoptive immunotherapy.

HER-2/neu as a target for cancer vaccines

A novel modality toward the treatment of HER-2/neu-positive malignancies, mostly including breast and, more recently prostate carcinomas, has been the use of vaccines targeting HER-2/neu extracellular and intracellular domains. HER-2/neu-specific vaccines have been demonstrated to generate durable T-cell anti-HER-2/neu immunity when tested in Phase I and II clinical trials with no significant toxicity or autoimmunity directed against normal tissues. Targeting of HER-2/neu in active immunotherapy may involve peptide and DNA vaccines. Moreover, active anti-HER-2/neu immunization could facilitate the ex vivo expansion of HER-2/neu-specific T cells for use in adoptive immunotherapy for the treatment of established metastatic disease. In addition, early data from trials examining the potential use of HER-2/neu-based vaccines in the adjuvant setting to prevent the relapse of breast cancer in high-risk patients have shown promising results. Future approaches include multiepitope preventive vaccines and combinatorial treatments for generating the most efficient protective anti-tumor immunity.

TAA polyepitope DNA-based vaccines: a potential tool for cancer therapy

DNA-based cancer vaccines represent an attractive strategy for inducing immunity to tumor associated antigens (TAAs) in cancer patients. The demonstration that the delivery of a recombinant plasmid encoding epitopes can lead to epitope production, processing, and presentation to CD8+ T-lymphocytes, and the advantage of using a single DNA construct encoding multiple epitopes of one or more TAAs to elicit a broad spectrum of cytotoxic T-lymphocytes has encouraged the development of a variety of strategies aimed at increasing immunogenicity of TAA polyepitope DNA-based vaccines. The polyepitope DNA-based cancer vaccine approach can (a) circumvent the variability of peptide presentation by tumor cells, (b) allow the introduction in the plasmid construct of multiple immunogenic epitopes including heteroclitic epitope versions, and (c) permit to enroll patients with different major histocompatibility complex (MHC) haplotypes. This review will discuss the rationale for using the TAA polyepitope DNA-based vaccination strategy and recent results corroborating the usefulness of DNA encoding polyepitope vaccines as a potential tool for cancer therapy.

A new era in anticancer peptide vaccines

The use of synthetic peptides as vaccines aimed at the induction of therapeutic CD8-positive T-cell responses against tumor cells initially experienced great enthusiasm, mostly because of advances in vaccine technology, including design, synthesis, and delivery. However, despite impressive results in animal models, the application of such vaccines in humans has met with only limited success. The therapeutic activity of vaccine-stimulated, tumor-specific, CD8-positive T cells can be hampered through the physical burden of the tumor, tolerance mechanisms, and local factors within the tumor microenvironment. Recently, accumulating evidence has suggested that combining a peptide-based therapeutic vaccination with conventional chemotherapy can uncover the full potential of the antitumor immune response, increasing the success of immunotherapy. In addition, therapeutic vaccination in the preventive setting has been extremely effective in eliciting antitumor responses in preclinical tumor models and has demonstrated good promise clinically in patients with minimal residual disease. The rationale behind preventive vaccination is that patients with minimal tumor burden still have a fully competent immune system capable of developing robust antitumor responses. Finally, therapeutic CD8-positive T-cell peptide vaccines have been improved by coimmunization with T-helper epitopes expressed on long peptides.

Cancer immunotherapy

Recent scientific advances have expanded our understanding of the immune system and its response to malignant cells. The clinical goal of tumour immunotherapy is to provide either passive or active immunity against malignancies by harnessing the immune system to target tumours. Monoclonal antibodies, cytokines, cellular immunotherapy, and vaccines have increasingly become successful therapeutic agents for the treatment of solid and haematological cancers in preclinical models, clinical trials, and practice. In this article, we review recent advances in the immunotherapy of cancer, focusing on new strategies and future perspectives as well as on clinical trials attempting to enhance the efficacy of immunotherapeutic modalities and translate this knowledge into effective cancer therapies.

Identification of HLA class II H5N1 hemagglutinin epitopes following subvirion influenza A (H5N1) vaccination

Prophylactic immunization against influenza infection requires CD4+ T-helper cell activity for optimal humoral and cellular immunity. Currently there is one FDA approved H5N1 subvirion vaccine available, although stockpiles of this vaccine are insufficient for broad population coverage and the vaccine has only demonstrated modest immunogenicity. Specific activation of CD4+ T-helper cells using class II H5N1 HA peptide vaccines may be a useful component in immunization strategy and design. Identification of HLA class II HA epitopes was undertaken in this report by obtaining PBMCs from volunteers previously immunized with an H5N1 inactivated subvirion vaccine, followed by direct ex vivo stimulation of CD4+ T cells against different sources of potential HA class II epitopes. In the 1st round of analysis, 35 donors were tested via IFN-gamma ELISPOT using pools of overlapping HA peptides derived from the H5N1 A/Thailand/4(SP-528)/2004 virus, recombinant H5N1 (rHA) and inactivated H5N1 subvirion vaccine. In addition, a series of algorithm-predicted epitopes coupled with the Ii-Key moiety of the MHC class II-associated invariant chain for enhanced MHC class II charging were also included. Specific responses were observed for all 20 peptide pools, with 6-26% of vaccinated individuals responding to any given pool (donor response frequency) and a magnitude of response ranging from 3- to >10-fold above background levels. Responses were similarly observed with the majority of algorithm-predicted epitopes, with a donor response frequency of up to 29% and a magnitude of response ranging from 3-10-fold (11/24 peptides) to >10-fold above background (7/24 peptides). PBMCs from vaccine recipients that had detectable responses to H5N1 rHA following 1st round analysis were used in a 2nd round of testing to confirm the identity of specific peptides based on the results of the 1st screening. Sixteen individual HA peptides identified from the library elicited CD4+ T cell responses between 3- and >10-fold above background, with two peptides being recognized in 21% of recipients tested. Eight of the putative MHC class II epitopes recognized were found in regions showing partial to significant sequence homology with New Caledonia H1N1 influenza HA, while eight were unique to H5N1 HA. This is the first study to identify H5N1 HA epitope-specific T cells in vaccine recipients and offers hope for the design of a synthetic peptide vaccine to prime CD4+ T-helper cells. Such a vaccine could be used to provide at least some minimal level of H5N1 protection on its own and/or prime for a subsequent dose of a more traditional but supply-limited vaccine.

Results of the first phase I clinical trial of the novel II-key hybrid preventive HER-2/neu peptide (AE37) vaccine

PURPOSE

HER-2/neu is overexpressed in breast cancer and is the source of immunogenic peptides. CD4(+) T-helper peptides for HER-2/neu are being evaluated in vaccine trials. The addition of Ii-Key, a four-amino-acid LRMK modification, increases vaccine potency when compared with unmodified class II epitopes. We present the results of the first human phase I trial of the Ii-Key hybrid HER-2/neu peptide (AE37) vaccine in disease-free, node-negative breast cancer patients.

PATIENTS AND METHODS

The dose escalation trial included five dose groups, to determine safety and optimal dose of the hybrid peptide (100 microg, 500 microg, 1,000 microg) and granulocyte-macrophage colony-stimulating factor (GM-CSF; range, 0 to 250 microg). In the event of significant local toxicity, GM-CSF (or peptide in absence of GM-CSF) was reduced by 50%. Immunologic response was monitored by delayed-type hypersensitivity and [(3)H]thymidine proliferative assays for both the hybrid AE37 (LRMK-positive HER-2/neu:776-790) and AE36 (unmodified HER-2/neu:776-790).

RESULTS

All 15 patients completed the trial with no grade 3 to 5 toxicities. Dose reductions occurred in 47% of patients. In the second group (peptide, 500 microg; GM-CSF, 250 microg), all patients required dose reductions, prompting peptide-only inoculations in the third group. The vaccine induced dose-dependent immunologic responses in vitro and in vivo to AE37, as well as AE36.

CONCLUSION

The hybrid AE37 vaccine seems safe and well tolerated with minimal toxicity if properly dosed. AE37 is capable of eliciting HER-2/neu-specific immune responses, even without the use of an adjuvant. This trial represents the first human experience with the Ii-Key modification, and to our knowledge, AE37 is the first peptide vaccine to show potency in the absence of an immunoadjuvant.

Induction of potent CD4+ T cell-mediated antitumor responses by a helper HER-2/neu peptide linked to the Ii-Key moiety of the invariant chain

The Ii-Key fragment from the MHC class II-associated invariant chain (or Ii protein) has been shown to facilitate direct charging of MHC class II epitopes to the peptide binding groove. The purpose of the present study was to test the potential of a series of Ii-Key/HER-2/neu776-790 hybrid peptides to generate increased frequencies of peptide-specific CD4+ T cells over the native peptide in mice transgenic (Tg) for a chimeric human mouse class II molecule (DR4-IE) (H-2b) as well as their antitumor potency. Following in vivo priming, such hybrid peptides induced increased proliferation and frequencies of IFN-gamma producing CD4+ T cells in response to either syngeneic dendritic cells pulsed with native peptide, or HLA-DR4+ human tumor cell lines expressing HER-2/neu. Hybrid peptides were more stable in an off-rate kinetics assay compared to the native peptide. In addition, antigen-specific CD4+ T cells from hybrid peptide immunized DR4-IE Tg mice synergized with HER-2/neu(435-443)-specific CD8+ T cells from HLA-A2.1 Tg HHD (H-2b) mice in producing antitumor immunity into SCID mice xenografted with the HER-2/neu+, HLA-A2.1+ and HLA-DR4+ FM3 human melanoma cell line. High proportions of these adoptively transferred HER-2/neu peptide-specific CD4+ and CD8+ T cells infiltrated FM3-induced tumors (tumor infiltrating lymphocytes; TIL) in SCID mice. CD8+ TIL exhibited long-lasting antitumor activity when cotransferred with CD4+ TIL, inducing regression of FM3 tumors in a group of untreated, tumor-bearing SCID mice, following adoptive transfer. Our data show that Ii-Key modified HER-2/neu776-790 hybrid peptides are sufficiently potent to provide antigen-specific CD4+ TH cells with therapeutic antitumor activity.