Adenovirus-Mediated MUC1 gene transduction into human blood-derived dendritic cells

Cancer immunotherapy using virally transduced dendritic cells: animal studies and human clinical trials

The immune system uses a process known as 'immunosurveillance' to help prevent the outgrowth of tumors. In cancer immunotherapy, a major goal is for immunity against tumor-associated antigens to be generated or strengthened in patients. To achieve this goal, several approaches have been tested, including the use of highly potent antigen-presenting cells called dendritic cells (DCs), which can activate T cells efficiently. Presentation of peptides derived from tumor antigens on the surface of DCs can stimulate strong antitumor immunity. Using recombinant viral vectors encoding tumor-associated antigens, DCs can be engineered efficiently to express sustained levels of tumor-antigen peptides. This review discusses the effectiveness of virally transduced DCs in treating tumors and generating antigen-specific T-cell responses. It covers mouse and nonhuman primate studies, preclinical in vitro human cell experiments and clinical trials.

MUC1-based recombinant Bacillus Calmette-Guerin vaccines as candidates for breast cancer immunotherapy

IMPORTANCE OF THE FIELD

The challenge in breast cancer vaccine development is to find the best combination of antigen, adjuvant and delivery system to produce a strong and long-lasting immune response. Mucin 1 (MUC1) is a potential candidate target for breast cancer immunotherapy. Bacillus Calmette-Guerin (BCG) is used widely in human vaccines. Furthermore, it can potentially offer unique advantages for developing a safe and effective multi-vaccine vehicle. Due to these properties, the development of MUC1 based recombinant BCG (rBCG) vaccines for breast cancer immunotherapy has gained great momentum in recent years.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss the recent progress in MUC1-based breast cancer immunotherapy and to highlight the advantages of MUC1-based rBCG vaccines as the new breast cancer vaccines.

WHAT THE READER WILL GAIN

Several promising MUC1-based rBCG vaccines have been shown to induce MUC1-specific antitumor immune responses in pre-clinical studies. This review updates and evaluates this very important and rapidly developing field, and provides a critical perspective and information source for its potential clinical applications.

TAKE HOME MESSAGE

MUC1-based rBCG vaccines have been shown to elicit an effective anti-tumor immune response in vivo demonstrating its potential utility in breast cancer treatment.

Adenovirus type 5 with modified hexons induces robust transgene-specific immune responses in mice with pre-existing immunity against adenovirus type 5

BACKGROUND

Adenovirus type 5 (Ad5) is widely used as a vehicle for vaccine delivery in the treatment of infectious disease and cancer. However, the efficacy of Ad5 vectors has been limited in humans because exposure to Ad5 infections results in most adults having neutralizing antibodies against Ad5. To overcome this limitation, the hexon epitope present in the fifth hypervariable region of Ad5 was modified.

METHODS

To evaluate the ability of Ad5 vectors encoding the HIV env protein to induce Ag-specific immune responses in the face of pre-existing anti-Ad5 immunity, mice were administrated intramuscularly with the Ad-Luc vector, and then vaccinated with parental or hexon-modified Ad5 vectors (Ad-HisHIV, Ad-END/AAAHIV or Ad-HIV) at week 8. HIV-specific cell-mediated immune responses were detected through a combination of tetramer assays and intracellular cytokine staining from weeks 8-23.

RESULTS

The hexon-modified Ad vector was able to escape from anti-Ad5 neutralizing antibody, and mice with the modified vector generated significantly lower individual neutralizing antibody than those immunized with the parental vector. Furthermore, mice with pre-existing anti-Ad immunity immunized with the modified vector generated significantly stronger cell-mediated anti-env responses than those immunized with the parental vector.

CONCLUSIONS

These data demonstrate that Ad5 vector with hexon modification reduce their sensitivity to pre-existing anti-Ad immunity and improve their clinical utility.

MUC1 as a target antigen for cancer immunotherapy

The cancer-associated antigen MUC1 is overexpressed and modified by tumor cells in over half of all cancer cases. Despite various complexities associated with this antigen, it is well worth pursuing as a vaccine for the immunotherapy of cancer. In this review, the authors describe the discovery of MUC1 and its association with cancer, recent observations showing that the immunology of MUC1 is complicated, animal data showing that it can be a target for immune-mediated tumor rejection, and finally, preliminary clinical results to show that vaccine-based immunotherapy with MUC1 does have an impact on the therapy of cancer.

Transduction with a fiber-modified adenoviral vector is superior to non-viral nucleofection for expressing tumor-associated Ag mucin-1 in human DC

BACKGROUND

DC-presenting tumor Ag are currently being developed to be used as a vaccine in human cancer immunotherapy. To increase the chances for successful therapy it is important to deliver full-length tumor Ag instead of loading single peptides. Methodologically, several recombinant DNA delivery techniques have been used.

METHODS

In this study we compared nucleofection, an optimized form of electroporation, and adenoviral transduction regarding their efficiency to transduce human monocyte-derived (Mo-) DC in vitro. Expression of the tumor-associated Ag mucin-1 (MUC1) after adenoviral transduction (rAd5Fib35-MUC1) was determined using two MAb.

RESULTS

We showed that the viability of cells and percentage of green fluorescent protein (GFP)-positive cells after transduction with a fiber-modified adenoviral vector (rAd5F35-GFP) was much higher than after nucleofection. Furthermore, phenotype and function of DC were not impaired by infection with adenovirus particles. Cells matured normally; up-regulation of CD40, CD80, CD83, CD86 and HLA-DR was not affected by adenoviral transduction. The capacity to stimulate naive T-cell proliferation was preserved and no change in IL-10 production was observed. Production of IL-12 increased up to 500-fold upon adenoviral transduction, considered to contribute positively to an anti-tumor immune response. Non-transduced mature DC expressed low levels of endogenous MUC1. After transduction with the rAd5F35-MUC1 adenoviral vector, a 100-fold increase in MUC1 expression by DC was observed.

DISCUSSION

The use of the fiber-modified adenoviral vector presented here may therefore be favorable compared with non-viral gene delivery systems for DC that will be used in cancer immunotherapy.

Combinational adenovirus-mediated gene therapy and dendritic cell vaccine in combating well-established tumors

Recent developments in tumor immunology and biotechnology have made cancer gene therapy and immunotherapy feasible. The current efforts for cancer gene therapy mainly focus on using immunogenes, chemogenes and tumor suppressor genes. Central to all these therapies is the development of efficient vectors for gene therapy. By far, adenovirus (AdV)-mediated gene therapy is one of the most promising approaches, as has confirmed by studies relating to animal tumor models and clinical trials. Dendritic cells (DCs) are highly efficient, specialized antigen-presenting cells, and DC-based tumor vaccines are regarded as having much potential in cancer immunotherapy. Vaccination with DCs pulsed with tumor peptides, lysates, or RNA, or loaded with apoptotic/necrotic tumor cells, or engineered to express certain cytokines or chemokines could induce significant antitumor cytotoxic T lymphocyte (CTL) responses and antitumor immunity. Although both AdV-mediated gene therapy and DC vaccine can both stimulate antitumor immune responses, their therapeutic efficiency has been limited to generation of prophylactic antitumor immunity against re-challenge with the parental tumor cells or to growth inhibition of small tumors. However, this approach has been unsuccessful in combating well-established tumors in animal models. Therefore, a major strategic goal of current cancer immunotherapy has become the development of novel therapeutic strategies that can combat well-established tumors, thus resembling real clinical practice since a good proportion of cancer patients generally present with significant disease. In this paper, we review the recent progress in AdV-mediated cancer gene therapy and DC-based cancer vaccines, and discuss combined immunotherapy including gene therapy and DC vaccines. We underscore the fact that combined therapy may have some advantages in combating well-established tumors vis-a-vis either modality administered as a monotherapy.

Allogeneic gastric cancer cell-dendritic cell hybrids induce tumor antigen (carcinoembryonic antigen) specific CD8(+) T cells

The development of protocols for the ex vivo generation of dendritic cells (DCs) has led to intensive research of their potential use in immunotherapy. Accumulating results show the efficacy of this treatment on melanomas which are highly immunogenic. However, its efficacy remains unclear in other tumors. In this study, allogeneic gastric cancer cell-DC hybrids were used to determine the efficacy of this type of immunotherapy in gastric cancer. Fusion cells of DC and allogeneic gastric cancer cells were generated by polyethylene glycol (PEG) and electrofusion. These hybrids were used to induce tumor associated antigen (TAA) specific cytotoxic T lymphocytes (CTLs). The DCs were successfully fused with the allogeneic gastric cancer cells resulting in hybrid cells. These hybrid cells were functional as antigen-presenting cell because they induced allogeneic CD4(+) T cells proliferation. CD8(+) T cells stimulated by the MKN-45-DC hybrid cells were able to kill MKN-45 when used for immunization. The CTLs killed another gastric cancer cell line, MKN-1, as well as a melanoma cell line, 888mel, suggesting the recognition of a shared tumor antigen. MKN-45 specific CTLs can recognize carcinoembryonic antigen (CEA), indicating that the killing is due to tumor antigens as well as alloantigens. This approach suggests the possible use of allogeneic gastric cancer cell-DC hybrids in DC based immunotherapy for gastric cancer treatment.

Analysis of HLA-A24-restricted CMVpp65 peptide-specific CTL with HLA-A*2402-CMVpp65 tetramer

Developing precise and efficient methods of monitoring immune responses against cytomegalovirus (CMV) infection in immunocompromised transplantation patients is important. With the aim of optimizing the monitoring strategy, an HLA-A24-CMVpp65 tetramer-based analysis of CMVpp65 peptide-specific CTL lines was performed. Previously, the HLA-A24-restricted CTL epitope of CMVpp65 matrix protein was identified (QYDPVAALF aa 341-349). In the present study, CMVpp65 (aa 341-349) peptide-specific CTL lines were obtained from PBLs of 12 HLA-A24+ healthy donors by two stimulations with peptide-pulsed dendritic cells (DC). Among 12 CTL lines, 9 showed HLA-A*2402-CMVpp65 tetramer staining, which was found to be strongly co-related to the amount of IFN-gamma produced by CMVpp65 peptide-restimulated CTL lines (r=0.943, P<0.001). These results suggested that HLA-A*2402-CMVpp65 tetramer staining was an efficient way to monitor immune responses against CMV infection in HLA-A24+ immunocompromised hosts.

Antitumor effect induced by dendritic cell (DC)-based immunotherapy against peritoneal dissemination of the hamster pancreatic cancer

Establishing a method to control peritoneal dissemination is one of the most pressing issues in the postsurgical treatment of pancreatic cancer. In the present study, we investigated the effect of dendritic cell (DC)-based immunotherapy on peritoneal disseminations of hamster pancreatic cancer cells, PGHAM-1. After the orthotopically inoculation of 2 x 10(6) PGHAM-1 cells, DC pulsed with PGHAM-1-derived tumor lysates, DC alone or PBS as a vehicle was injected intraperitoneally (i.p.) three times at weekly intervals. The group treated with DC or DC+lysate was found to have smaller disseminated tumors than the vehicle-treated. In addition, mean survival time in the DC+lysate groups was significantly longer than the PBS group. These findings suggested that DC-based immunotherapy might be efficient for the treatment of peritoneal disseminations of the pancreatic cancer.

Chemokine gene modification of human dendritic cell-based tumor vaccines using a recombinant adenoviral vector

Previous animal studies conducted in our laboratory have shown that tumor antigen-pulsed dendritic cells (TP-DC) can mediate antitumor effects in vivo. However, durable and complete regression of established tumors has been difficult to achieve through the administration of TP-DC alone. To better augment immune priming to tumors in vivo, we have hypothesized that it is necessary to achieve an increased number of host-derived, naïve T cells at the site of TP-DC vaccine injections. To accomplish this goal, we have embarked on a series of studies that utilize defined chemokines. One of these molecules, secondary lymphoid tissue chemokine (SLC), has been shown to be uniquely chemoattractant for naïve T cells and dendritic cells. We propose that gene modification of DC-based tumor vaccines to produce human SLC will enhance T-cell recruitment and immune priming to tumor-associated antigens, and thereby translate into improved antitumor vaccine efficacy in vivo. Utilizing an E1-, E3-deleted adenoviral vector containing the gene for human SLC, we have been able to transduce human DC to produce biologically active human SLC that chemoattracts human T cells in vitro. SLC production by transduced DC was markedly enhanced upon DC maturation. Additionally, these SLC-secreting DC were found to be viable to a large extent despite the cytopathic effect inherent in adenoviral gene transfer and, most importantly, functional as determined by their ability to prime autologous T cells to a known melanoma-associated antigen, MART-1. Based on these encouraging results, we plan to initiate Phase I clinical studies utilizing DC-SLC to treat patients with advanced solid tumors.

Adenoviral Transgene Ubiquitination Enhances Mouse Immunization and Class I Presentation by Human Dendritic Cells

Therapeutic vaccination aims at a strong stimulation of antigen-specific CD8(+) T-cells, so that they differentiate into effectors active in vivo against antigenic targets. Two adenovirus vectors (Ad) encoding two HLA-A*0201-restricted HIV epitope sequences (pol 476 and pol 589) were constructed. The Ad differ by the presence or absence of a ubiquitin monomer sequence (AdUb(+) and AdUb(-)). The effect of transgene product ubiquitination was analyzed on (1) in vivo, the immunization of Ad vaccinated HLA-A*0201 humanized HHD mice and (2) in vitro, the presentation of the transgene encoded peptides by transduced human dendritic cells (DC). In vivo, we found that immunization of humanized HHD mice with AdUb(+) elicited a transgene product-specific interferon (INF)-gamma CD8(+) T-cell response detectable by enzyme-linked immunospot (ELISPOT), whereas the AdUb(-) construction did not. Antigen-specific cytotoxic T lymphocytes (CTL) were also generated in HHD mice immunized with AdUb(+) and not with AdUb(-). In vitro, using human AdUb(+)-transduced DC, a sizeable expansion of pol 476 and pol 589 tetramer positive CD8(+) T cells as well as CD8(+) CTL were obtained in healthy donors. Compared to AdUb(-)-transduced DC, AdUb(+)-transduced DC triggered a higher number of pol 476-specific IFN-gamma-secreting CD8(+) T cells. In agreement, AdUb(+) transduced DC, used as target in a (51)Cr-release assay, were more efficiently lysed by peptide-specific CTL than AdUb(-)-transduced DC. In conclusion, the addition of an ubiquitin sequence to the adenoviral transgene, used as an antigen source, resulted in both in vivo enhanced CD8(+) T-cell immunogenicity in HHD mice and in vitro increased HLA class I-restricted presentation of encoded peptides by human DC.

Viral vectors for dendritic cell-based immunotherapy

Dendritic cells (DCs) constitute a specialised system of antigen-presenting cells with a high capacity to induce and to modulate the immune response against microbial, tumour and self-antigens. New techniques to generate large amounts of DCs together with the molecular identification of human tumour-associated antigens (TAA) have opened new ways for antigen-specific cancer immunotherapies. DCs loaded either with TAA-derived MHC class I-specific synthetic peptides or with whole tumour cell preparations have been used in numerous clinical trials evaluating the efficacy of DCs in patients with cancer. However, the disadvantages of DCs pulsed with synthetic peptides from TAA include the uncertainty regarding the longevity of antigen presentation, the restriction by the patient's haplotype and the relatively low number of known MHC class I and in particular of MHC class II helper cell-related epitopes. Whole tumour cell preparations are difficult to standardise, and they depend on the availability of tumour cells. Thus the utilisation of viral vectors genetically modified to express TAA for the ex vivo transduction of DCs is an attractive alternative to achieve a MHC I- and MHC II-restricted presentation of tumoural antigens. To induce protective anti-tumoural immune response an increasing number of modified viral vectors have been used to transduce DCs. Although high transduction efficacies were reported for several viruses, analysis of the interaction of viral vectors with DCs has revealed several viral mechanisms that interfere with main functions of DCs, dampening somewhat the initial optimism in the field of DC transduction. However, promising results with different vectors have been achieved. In this review we summarise available data and discuss advantages and drawbacks of currently available vectors.

Transfection of dendritic cells with RNA induces CD4- and CD8-mediated T cell immunity against breast carcinomas and reveals the immunodominance of presented T cell epitopes

Transfection of dendritic cells (DC) with tumor-derived RNA has recently been shown to elicit tumor-specific CTL capable of recognizing and lysing a variety of tumor cells. In our study we analyzed the induction of HLA class I- and II-restricted T cell responses against MCF-7 breast cancer cells. Using this approach we were able to elicit CD4- and CD8-mediated antitumor responses. The CTL specifically lysed MCF-7 cells and DC electroporated with MCF-7 RNA, but spared control cell lines. The specificity of the cytotoxic activity was confirmed in cold target inhibition assays and using mAbs blocking HLA class I molecules. Interestingly, these polyclonal cytotoxic T cells recognized selectively two epitopes derived from the MUC1 and Her-2/neu tumor Ags. The induced Th cells were found to be entirely HLA class II restricted and showed a significant cross-reactivity to a renal cell carcinoma cell line, similar to the results obtained with cytotoxic T cells.

Advances in dendritic cell-based vaccine of cancer

Dendritic cells (DCs) are potent antigen presenting cells that exist in virtually every tissue, and from which they capture antigens and migrate to secondary lymphoid organs where they activate naïve T cells. Although DCs are normally present in extremely small numbers in the circulation, recent advances in DC biology have allowed the development of methods to generate large numbers of these cells in vitro. Because of their immunoregulatory capacity, vaccination with tumor antigen-presenting DCs has been proposed as a treatment modality for cancer. In animal models, vaccination with DCs pulsed with tumor peptides, lysates, or RNA or loaded with apoptotic/necrotic tumor cells could induce significant antitumor CTL responses and antitumor immunity. However, the results from early clinical trails pointed to a need for additional improvement of DC-based vaccines before they could be considered as practical alternatives to the existing cancer treatment strategies. In this regard, subsequent studies have shown that DCs that express transgenes encoding tumor antigens are more potent primers of antitumor immunity both in vitro and in vivo than DCs simply pulsed with tumor peptides. Furthermore, DCs that have been engineered to express certain cytokines or chemokines can display a substantially improved maturation status, capacity to migrate to secondary lymphoid organs in vivo, and abilities to stimulate tumor-specific T cell responses and induce tumor immunity in vivo. In this review we also discuss a number of factors that are important considerations in designing DC vaccine strategies, including (i) the type and concentrations of tumor peptides used for pulsing DCs; (ii) the timing and intervals for DC vaccination/boostable data on DC vaccination portends bright prospects for this approach to tumor immune therapy, either alone or in conjunction with other therapies.