Induction of CAMEL/NY-ESO-ORF2-specific CD8+ T cells upon stimulation with dendritic cells infected with a modified Ad5 vector expressing a chimeric Ad5/35 fiber

Therapeutic Cancer Vaccines—Antigen Discovery and Adjuvant Delivery Platforms

For decades, vaccines have played a significant role in protecting public and personal health against infectious diseases and proved their great potential in battling cancers as well. This review focused on the current progress of therapeutic subunit vaccines for cancer immunotherapy. Antigens and adjuvants are key components of vaccine formulations. We summarized several classes of tumor antigens and bioinformatic approaches of identification of tumor neoantigens. Pattern recognition receptor (PRR)-targeting adjuvants and their targeted delivery platforms have been extensively discussed. In addition, we emphasized the interplay between multiple adjuvants and their combined delivery for cancer immunotherapy.

Cellular immune responses against cancer-germline genes in cancers

BACKGROUND

Cancer-germline genes are a class of genes that are normally expressed in testis, trophoblast and few somatic tissues but abnormally expressed in tumor tissues. Their expression signature indicates that they can induce cellular immune responses, thus being applied as targets in cancer immunotherapy.

OBJECTIVES

To obtain the data of cellular immune responses against cancer-germline genes in cancer.

METHODS

We searched PubMed/Medline with the key words cancer-germline antigen, cancer-testis antigen, CD4+ T cell, CD8+ T cell and cancer.

RESULTS

About 40 cancer-germline genes have been shown to induce T cell specific responses in cancer patients. Melanoma, lung and breast cancer are among the mostly assessed cancer types. Several epitopes have been identified which can be used in immunotherapy of cancer.

CONCLUSION

Cellular immune responses against cancer-germline genes are indicative of appropriateness of these genes as therapeutic targets.

Myeloid and plasmacytoid dendritic cells are susceptible to recombinant adenovirus vectors and stimulate polyfunctional memory T cell responses

Although replication-incompetent recombinant adenovirus (rAd) type 5 is a potent vaccine vector for stimulating T and B cell responses, high seroprevalence of adenovirus type 5 (Ad5) within human populations may limit its clinical utility. Therefore, alternative adenovirus serotypes have been studied as vaccine vectors. In this study, we characterized the ability of rAd5 and rAd35 to infect and induce maturation of human CD11c(+) myeloid dendritic cells (MDCs) and CD123(+) plasmacytoid dendritic cells (PDCs), and their ability to stimulate Ag-specific T cells. Both MDCs and PDCs were found to express the primary receptor for Ad35 (CD46) but not Ad5 (coxsackie-adenovirus receptor; CAR). Both dendritic cell (DC) subsets were also more susceptible to rAd35 than to rAd5. MDCs were more susceptible to both rAd35 and rAd5 than were PDCs. Whereas rAd35 used CD46 for entry into DCs, entry of rAd5 may be through a CAR-independent pathway. Exposure to rAd35 but not rAd5 induced high levels of IFN-alpha in PDCs and phenotypic differentiation in both DC subsets. MDCs and PDCs exposed to either rAd5 or rAd35 encoding for CMV pp65 were able to present pp65 and activate CMV-specific memory CD8(+) and CD4(+) T cells in a dose-dependent manner, but MDCs stimulated the highest frequencies of pp65-specific T cells. Responding T cells expressed multiple functions including degranulation (CD107a surface mobilization) and production of IFN-gamma, IL-2, TNF-alpha, and MIP-1beta. Thus, the ability of rAd35 to naturally target important DC subsets, induce their maturation, and appropriately present Ag to T cells may herald greater in vivo immunogenicity than has been observed with rAd5.

Molecular and immunological evaluation of the expression of cancer/testis gene products in human colorectal cancer

Tumor-specific gene products, such as cancer/testis (CT) antigens, constitute promising targets for the development of T cell vaccines. Whereas CT antigens are frequently expressed in melanoma, their expression in colorectal cancers (CRC) remains poorly characterized. Here, we have studied the expression of the CT antigens MAGE-A3, MAGE-A4, MAGE-A10, NY-ESO-1 and SSX2 in CRC because of the presence of well-described HLA-A2-restricted epitopes in their sequences. Our analyses of 41 primary CRC and 14 metastatic liver lesions confirmed the low frequency of expression of these CT antigens. No increased expression frequencies were observed in metastatic tumors compared to primary tumors. Histological analyses of CRC samples revealed heterogeneous expression of individual CT antigens. Finally, evidence of a naturally acquired CT antigen-specific CD8(+) T cell response could be demonstrated. These results show that the expression of CT antigens in a subset of CRC patients induces readily detectable T cell responses.

Intradermal Delivery of Adenoviral Type-35 Vectors Leads to High Efficiency Transduction of Mature, CD8+T Cell-Stimulating Skin-Emigrated Dendritic Cells

Recombinant adenovirus (Ad) type 35 (rAd35) shows great promise as vaccine carrier with the advantage of low pre-existing immunity in human populations, in contrast to the more commonly used rAd5 vector. The rAd35 vector uses CD46 as a high-affinity receptor, which, unlike the rAd5 receptor, is expressed on human dendritic cells (DC), the most powerful APCs identified to date. In this study, we show that in contrast to rAd5, rAd35 infects migrated and mature CD83+ cutaneous DC with high efficiency (up to 80%), when delivered intradermally in an established human skin explant model. The high transduction efficiency is in line with high expression levels of CD46 detected on migratory cutaneous DC, which proved to be further increased upon intradermal administration of GM-CSF and IL-4. As compared with Ad5, these Ad35 infection characteristics translate into higher absolute numbers of skin-emigrated DC per explant that both express the transgene and are phenotypically mature. Finally, we demonstrate that upon intracutaneous delivery of a rAd35 vaccine encoding the circumsporozoite (CS) protein of Plasmodium falciparum, emigrated DC functionally express and process CS-derived epitopes and are capable of activating specific CD8+ effector T cells, as evidenced by activation of an HLA-A2-restricted CS-specific CD8+ T cell clone. Collectively, these data demonstrate the utility of rAd35 vectors for efficient in vivo human DC transduction.

Directions in the immune targeting of cancer: lessons learned from the cancer-testis Ag NY-ESO-1

Since the early 1990s, numerous cancer Ag have been defined and for a handful of these there is now some clinical experience, which has made it possible to assess their value as targets for cancer immunotherapy. The cancer-testis Ag have been particularly attractive because their expression is limited to cancer and virtually no non-malignant cells apart from germ cells and trophoblast. Among these, NY-ESO-1 has been the focus of our attention. The exceptional immunogenicity of this Ag coupled with its widespread distribution among many cancer types make it a very good vaccine candidate, with the potential to be used in vaccines against many types of malignancies. This article reviews emerging knowledge about the biology of NY-ESO-1 and experience with the early clinical development of vaccines directed against NY-ESO-1. These early studies have yielded a wealth of information about the immunology of NY-ESO-1 and set the scene for future clinical strategies for immune targeting of cancer.

Human T cell responses against melanoma

Many antigens recognized by autologous T lymphocytes have been identified on human melanoma. Melanoma patients usually mount a spontaneous T cell response against their tumor. But at some point, the responder T cells become ineffective, probably because of a local immunosuppressive process occurring at the tumor sites. Therapeutic vaccination of metastatic melanoma patients with these antigens is followed by tumor regressions only in a small minority of the patients. The T cell responses to the vaccines show correlation with the tumor regressions. The local immunosuppression may be the cause of the lack of vaccination effectiveness that is observed in most patients. In patients who do respond to the vaccine, the antivaccine T cells probably succeed in reversing focally this immunosuppression and trigger a broad activation of other antitumor T cells, which proceed to destroy the tumor.

A new LAGE-1 peptide recognized by cytolytic T lymphocytes on HLA-A68 tumors

Antigens encoded by genes of the LAGE family, including LAGE-1 and NY-ESO-1, are of interest for cancer immunotherapy because they are tumor-specific and shared by tumors of different histological types. Several clinical trials are in progress with NY-ESO-1 peptides, protein, recombinant poxviruses, and dendritic cells pulsed with peptides. In this study, CD8 T lymphocytes from an individual without cancer were stimulated with dendritic cells infected with a recombinant avian poxvirus encoding a complete LAGE-1 protein. A CTL clone was isolated that recognized a new LAGE-1 peptide, ELVRRILSR, which corresponds to position 103-111 of the protein sequence. It is presented by HLA-A6801 molecules. When tumor cells expressing LAGE-1 were transfected with HLA-A68, they were lysed by the CTL clone, indicating that the peptide is processed in tumor cells. These results indicate that the LAGE-1.A68 peptide can be used for antitumoral vaccination. We observed also that specific T cells could be detected in a blood sample with a high sensitivity by using an A68/LAGE-1 fluorescent multimer.

Expression of aberrantly glycosylated tumor mucin-1 on human DC after transduction with a fiber-modified adenoviral vector

BACKGROUND

DC-presenting tumor Ag are currently being developed to be used as a vaccine in human cancer immunotherapy. To increase chances for successful therapy it is important to deliver full-length tumor Ag instead of loading single peptides.

METHODS

In this study we used a fiber-modified adenoviral vector (rAd5F35) containing full-length tumor Ag cDNA to transduce human monocyte (Mo)-derived DC in vitro. Cells were efficiently transduced and survived for at least 3 days after adenoviral transduction. Phenotype and function after maturation of Mo-DC were not impaired by infection with adenovirus particles. Expression of the tumor-associated Ag mucin-1 (MUC1) was detected using MAb defining different MUC1 glycoforms.

RESULTS

Non-transduced mature Mo-DC express endogenous MUC1 with normal glycosylation. After transduction with the rAd5F35-MUC1 adenoviral vector, Mo-DC also expressed MUC1 with tumor-associated glycosylation (Tn and T glycoforms), although no changes in mRNA levels of relevant glycosyltransferases could be demonstrated.

DISCUSSION

The presence of aberrantly glycosylated MUC1 may influence Ag presentation of the tumor glycoforms of MUC1 to immune cells, affecting tumor cell killing. These findings could be highly relevant to developing strategies for cancer immunotherapy based on DC vaccines using MUC1 as tumor Ag.

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.

Centrifugation enhances integrin-mediated transduction of dendritic cells by conventional and RGD-modified adenoviral vectors

The level of antigen loading can impact on the capacity for dendritic cells (DC) to activate T cell responses. Several different approaches to adenoviral (Ad)-based transduction were therefore assessed for their effect on both transgene expression and T cell activation. While a conventional E1(-)/E3Delta Ad vector (Ad/GFP) produced a concentration-dependent expression of GFP, a modified vector expressing Arginine-Glycine-Aspartic Acid (RGD) sequence on its fiber knob (Ad-RGD/GFP) enhanced transgene expression by 9-20-fold at each MOI. The addition of centrifugal force (2000xg) during DC transduction with Ad/GFP also increased expression up to 20-fold. However, combining centrifugation with the Ad-RGD/GFP vector produced no effect on transduction rate and only a 1.5- to 2-fold increase in GFP expression, suggesting overlapping mechanisms of action. Consistent with this, exogenous RGD peptide blocked transduction regardless of the vector used, or the addition of centrifugal force, and transduction was primarily limited to DC expressing the CD51 integrin receptor. Ad vectors expressing ovalbumin (OVA) were used to assess transduced DC for their capacity to activate OVA-specific T cells. We observed a significant relationship between transgene expression and the capacity for T cell activation regardless of whether transgene expression was increased by using a higher MOI, an RGD-modified vector, or by employing centrifugal force. Furthermore, combining these approaches produced synergistic effects on T cell activation. We conclude that RGD-modified vectors and centrifugation both enhance DC transduction by increasing entry via integrin receptors and that the capacity for T cell activation can be optimized by combining approaches to achieve the highest possible level of transgene expression.