Epidermal dendritic cells induce potent antigen-specific CTL-mediated immunity

Crystallinity of covalent organic frameworks controls immune responses

Biomaterials can act as pro- or anti-inflammatory agents. However, effects of biomaterials crystallinity on immune responses are poorly understood. We demonstrate that the adjuvant-like behaviour of covalent organic framework (COF) biomaterial is dependent on its crystallinity. COF crystallinity is inversely correlated with the activation of mouse and human dendritic cells (DC), but with antigen presentation by mouse DCs only. Amorphous COFs upregulates NFkB, TNF, and RIG-I signalling pathways, as well as the chemotaxis-associated gene Unc5c, when compared to crystalline COFs. Meanwhile, Unc5c inhibition disrupts the correlation between crystallinity and DC activation. Furthermore, COFs with the lowest crystallinity admixed with chicken ovalbumin (OVA) antigen prevent OVA-expressing B16F10 tumour growth in 60% of mice, with this protection associated with the induction of antigen-specific, pro-inflammatory T cell. The lowest crystalline COFs admixed with TRP2 antigen can also prevent non-immunogenic YUMM1.1 tumour growth in 50% of mice. These findings demonstrate that the crystallinity of biomaterials is an important aspect to consider when designing immunotherapy for pro- or anti-inflammatory applications.

Use of Iontophoresis Technology for Transdermal Delivery of a Minimal mRNA Vaccine as a Potential Melanoma Therapeutic

mRNA vaccines have attracted considerable attention as a result of the 2019 coronavirus pandemic; however, challenges remain regarding use of mRNA vaccines, including insufficient delivery owing to the high molecular weights and high negative charges associated with mRNA. These characteristics of mRNA vaccines impair intracellular uptake and subsequent protein translation. In the current study, we prepared a minimal mRNA vaccine encoding a tumor associated antigen human gp100_25-33 peptide (KVPRNQDWL), as a potential treatment for melanoma. Minimal mRNA vaccines have recently shown promise at improving the translational process, and can be prepared via a simple production method. Moreover, we previously reported the successful use of iontophoresis (IP) technology in the delivery of hydrophilic macromolecules into skin layers, as well as intracellular delivery of small interfering RNA (siRNA). We hypothesized that combining IP technology with a newly synthesized minimal mRNA vaccine can improve both transdermal and intracellular delivery of mRNA. Following IP-induced delivery of a mRNA vaccine, an immune response is elicited resulting in activation of skin resident immune cells. As expected, combining both technologies led to potent stimulation of the immune system, which was observed via potent tumor inhibition in mice bearing melanoma. Additionally, there was an elevation in mRNA expression levels of various cytokines, mainly interferon (IFN)-γ, as well as infiltration of cytotoxic CD8⁺ T cells in the tumor tissue, which are responsible for tumor clearance. This is the first report demonstrating the application of IP for delivery of a minimal mRNA vaccine as a potential melanoma therapeutic.

Immunogenicity Challenges Associated with Subcutaneous Delivery of Therapeutic Proteins

The subcutaneous route of administration has provided convenient and non-inferior delivery of therapeutic proteins compared to intravenous infusion, but there is potential for enhanced immunogenicity toward subcutaneously administered proteins in a subset of patients. Unwanted anti-drug antibody response toward proteins or monoclonal antibodies upon repeated administration is shown to impact the pharmacokinetics and efficacy of multiple biologics. Unique immunogenicity challenges of the subcutaneous route have been realized through various preclinical and clinical examples, although subcutaneous delivery has often demonstrated comparable immunogenicity to intravenous administration. Beyond route of administration as a treatment-related factor of immunogenicity, certain product-related risk factors are particularly relevant to subcutaneously administered proteins. This review attempts to provide an overview of the mechanism of immune response toward proteins administered subcutaneously (subcutaneous proteins) and comments on product-related risk factors related to protein structure and stability, dosage form, and aggregation. A two-wave mechanism of antigen presentation in the immune response toward subcutaneous proteins is described, and interaction with dynamic antigen-presenting cells possessing high antigen processing efficiency and migratory activity may drive immunogenicity. Mitigation strategies for immunogenicity are discussed, including those in general use clinically and those currently in development. Mechanistic insights along with consideration of risk factors involved inspire theoretical strategies to provide antigen-specific, long-lasting effects for maintaining the safety and efficacy of therapeutic proteins.

Allergen immunotherapy: routes, safety, efficacy, and mode of action

Allergic rhinitis, allergic conjunctivitis, and allergic asthma have been steadily increasing in prevalence in recent years. These allergic diseases have a major impact on quality of life and are a major economic burden in the US. Although allergen avoidance and pharmacotherapy are currently the mainstays of therapy, they are not always successful in treating patients' symptoms effectively. If a patient fails allergen avoidance and medical therapy, immunotherapy may be indicated. Furthermore, immunotherapy is the only therapy that may change the course of the disease and induce long-term remission. Though subcutaneous administration has been the standard route for immunotherapy for many decades, there are several other routes of administration that have been and are currently being studied. The goal of utilizing alternative routes of immunotherapy is to improve safety without decreasing the efficacy of treatment. This paper will review the novel routes of immunotherapy, including sublingual, oral, local nasal, epicutaneous, and intralymphatic.

Novel immune-modulator identified by a rapid, functional screen of the parapoxvirus ovis (Orf virus) genome

Background

The success of new sequencing technologies and informatic methods for identifying genes has made establishing gene product function a critical rate limiting step in progressing the molecular sciences. We present a method to functionally mine genomes for useful activities in vivo, using an unusual property of a member of the poxvirus family to demonstrate this screening approach.

Results

The genome of Parapoxvirus ovis (Orf virus) was sequenced, annotated, and then used to PCR-amplify its open-reading-frames. Employing a cloning-independent protocol, a viral expression-library was rapidly built and arrayed into sub-library pools. These were directly delivered into mice as expressible cassettes and assayed for an immune-modulating activity associated with parapoxvirus infection. The product of the B2L gene, a homolog of vaccinia F13L, was identified as the factor eliciting immune cell accumulation at sites of skin inoculation. Administration of purified B2 protein also elicited immune cell accumulation activity, and additionally was found to serve as an adjuvant for antigen-specific responses. Co-delivery of the B2L gene with an influenza gene-vaccine significantly improved protection in mice. Furthermore, delivery of the B2L expression construct, without antigen, non-specifically reduced tumor growth in murine models of cancer.

Conclusion

A streamlined, functional approach to genome-wide screening of a biological activity in vivo is presented. Its application to screening in mice for an immune activity elicited by the pathogen genome of Parapoxvirus ovis yielded a novel immunomodulator. In this inverted discovery method, it was possible to identify the adjuvant responsible for a function of interest prior to a mechanistic study of the adjuvant. The non-specific immune activity of this modulator, B2, is similar to that associated with administration of inactivated particles to a host or to a live viral infection. Administration of B2 may provide the opportunity to significantly impact host immunity while being itself only weakly recognized. The functional genomics method used to pinpoint B2 within an ORFeome may be more broadly applicable to screening for other biological activities in an animal.

Sunitinib facilitates the activation and recruitment of therapeutic anti-tumor immunity in concert with specific vaccination

The multikinase inhibitor sunitinib malate (SUT) has been reported to reduce levels of myeloid suppressor cells and Treg cells in cancer patients, hypothetically diminishing intrinsic impediments for active immunization against tumor-associated antigens in such individuals. The goal of this study was to identify longitudinal immune molecular and cellular changes associated with tumor regression and disease-free status after the treatment of established day 7 s.c. MO5 (B16.OVA) melanomas with SUT alone (1 mg/day via oral gavage for 7 days), vaccination using ovalbumin (OVA) peptide-pulsed dendritic cell [vaccine (VAC)] alone, or the combination of SUT and VAC (SUT/VAC). We observed superior anti-tumor efficacy for SUT/VAC combination approaches, particularly when SUT was applied at the time of the initial vaccination or the VAC boost. Treatment effectiveness was associated with the acute loss of (and/or failure to recruit) cells bearing myeloid-derived suppressor cells or Treg phenotypes within the tumor microenvironment (TME) and the corollary, prolonged enhancement of Type-1 anti-OVA CD8(+) T cell responses in the tumor-draining lymph node and the TME. Enhanced Type-1 T cell infiltration of tumors was associated with treatment-induced expression of vascular cell adhesion molecule-1 (VCAM-1) and CXCR3 ligand chemokines in vascular/peri-vascular cells within the TME, with SUT/VAC therapy benefits conditionally negated upon adminsitration of CXCR3 or VCAM-1 blocking antibodies. These data support the ability of a short 7 day course of SUT to (re)condition the TME to become more receptive to the recruitment and prolonged therapeutic action of (VAC-induced) anti-tumor Tc1 cells.

Epicutaneous/transcutaneous allergen-specific immunotherapy: rationale and clinical trials

PURPOSE OF REVIEW

IgE-mediated allergies, such as allergic rhinoconjunctivitis and asthma, have become highly prevalent, today affecting up to 35% of the population in industrialized countries. Allergen immunotherapy (also called hyposensitization therapy, desensitization or allergen-specific immunotherapy), the administration of gradually increasing amounts of an allergen, either subcutaneously or via the sublingual or oral route is effective. However, only few allergy patients (<5%) choose immunotherapy, as treatment duration is over years and because allergen administrations are associated with local and in some cases even systemic allergic side effects due to allergen accidentally reaching the circulation. Therefore, ideally the allergen should be administered to a site that contains high numbers of potent antigen-presenting cells in order to enhance efficacy and shorten treatment duration, and ideally that site should also be nonvascularized in order to prevent both systemic distribution of the allergen and systemic allergic side effects. The epidermis, a nonvascularized multilayer epithelium that contains high numbers of potent antigen-presenting Langerhans cells, could therefore be an interesting administration route.

RECENT FINDINGS

We have recently reintroduced transcutaneous or epicutaneous allergen-specific immunotherapy (EPIT) as treatment option for IgE-mediated allergies. This method was found efficacious and safe. Few applications of allergens using skin patches with a treatment duration of a few weeks were sufficient to achieve lasting relief.

SUMMARY

This review gives an overview on the history, the rationale, and the mechanisms of transcutaneous/epicutaneous immunotherapy.

Recent developments in cancer vaccines

The adoptive transfer of cancer Ag-specific effector T cells in patients can result in tumor rejection, thereby illustrating the immune system potential for cancer therapy. Ideally, one would like to directly induce efficient tumor-specific effector and memory T cells through vaccination. Therapeutic vaccines have two objectives: priming Ag-specific T cells and reprogramming memory T cells (i.e., a transformation from one type of immunity to another, for example, regulatory to cytotoxic). Recent successful phase III clinical trials showing benefit to the patients revived cancer vaccines. Dendritic cells (DCs) are essential in generation of immune responses, and as such represent targets and vectors for vaccination. We have learned that different DC subsets elicit different T cells. Similarly, different activation methods result in DCs able to elicit distinct T cells. We contend that a careful manipulation of activated DCs will allow cancer immunotherapists to produce the next generation of highly efficient cancer vaccines.

Noninvasive and efficient transdermal delivery of CpG-oligodeoxynucleotide for cancer immunotherapy

Oligodeoxynucleotides containing unmethylated cytosine-phosphate-guanosine motifs (CpG-ODN) possess immunostimulatory effects and potential antitumor activity. Since the skin is an easily available site of administration of CpG-ODN due to its accessibility and the presence of abundant antigen presenting cells, it is expected that the application of CpG-ODN to the skin would induce systemic immune response and antitumor activity. However, it is difficult to deliver hydrophilic macromolecules including CpG-ODN through the skin. We have previously demonstrated that small interfering RNA (siRNA) was efficiently delivered into rat epidermis by iontophoresis. In this report, we investigate the effect of transdermal iontophoretic delivery of CpG-ODN on the induction of immune responses and antitumor activity against B16F1 melanoma in mice. Iontophoresis promoted CpG-ODN delivery into the epidermis and dermis. Furthermore, iontophoretic delivery of CpG-ODN to the skin induced the expression of proinflammatory and Th1-type cytokines in the skin and draining lymph node. Finally, transdermal iontophoretic delivery of CpG-ODN led to antitumor activity against B16F1 melanoma. Interestingly, the CpG-ODN administration site is not restricted to the tumor area. In conclusion, CpG-ODN delivered transdermally induced potent antitumor activity, and our system is expected to serve as a simple and noninvasive approach for cancer immunotherapy.

Designing vaccines based on biology of human dendritic cell subsets

The effective vaccines developed against a variety of infectious agents, including polio, measles, and hepatitis B, represent major achievements in medicine. These vaccines, usually composed of microbial antigens, are often associated with an adjuvant that activates dendritic cells (DCs). Many infectious diseases are still in need of an effective vaccine including HIV, malaria, hepatitis C, and tuberculosis. In some cases, the induction of cellular rather than humoral responses may be more important because the goal is to control and eliminate the existing infection rather than to prevent it. Our increased understanding of the mechanisms of antigen presentation, particularly with the description of DC subsets with distinct functions, as well as their plasticity in responding to extrinsic signals, represent opportunities to develop novel vaccines. In addition, we foresee that this increased knowledge will permit us to design vaccines that will reprogram the immune system to intervene therapeutically in cancer, allergy, and autoimmunity.

Formulation and coating of microneedles with inactivated influenza virus to improve vaccine stability and immunogenicity

Microneedle patches coated with solid-state influenza vaccine have been developed to improve vaccine efficacy and patient coverage. However, dip coating microneedles with influenza vaccine can reduce antigen activity. In this study, we sought to determine the experimental factors and mechanistic pathways by which inactivated influenza vaccine can lose activity, as well as develop and assess improved microneedle coating formulations that protect the antigen from activity loss. After coating microneedles using a standard vaccine formulation, the stability of influenza vaccine was reduced to just 2%, as measured by hemagglutination activity. The presence of carboxymethylcellulose, which was added to increase viscosity of the coating formulation, was shown to contribute to vaccine activity loss. After screening a panel of candidate stabilizers, the addition of trehalose to the coating formulation was found to protect the antigen and retain 48-82% antigen activity for all three major strains of seasonal influenza: H1N1, H3N2 and B. Influenza vaccine coated in this way also exhibited thermal stability, such that activity loss was independent of temperature over the range of 4-37 degrees C for 24h. Dynamic light scattering measurements showed that antigen activity loss was associated with virus particle aggregation, and that stabilization using trehalose largely blocked this aggregation. Finally, microneedles using an optimized vaccine coating formulation were applied to the skin to vaccinate mice. Microneedle vaccination induced robust systemic and functional antibodies and provided complete protection against lethal challenge infection similar to conventional intramuscular injection. Overall, these results show that antigen activity loss during microneedle coating can be largely prevented through optimized formulation and that stabilized microneedle patches can be used for effective vaccination.

Harnessing human dendritic cell subsets to design novel vaccines

Dendritic cells (DCs) orchestrate a repertoire of immune responses that endow resistance to infection and tolerance to self. DC plasticity and subsets are prominent determinants of the quality of elicited immune responses. Different DC subsets display different receptors and surface molecules and express different sets of cytokines/chemokines, all of which lead to distinct immunological outcomes. Recent findings on human DC subsets and their functional specialization have provided insights for the design of novel human vaccines.

Epicutaneous allergen administration as a novel method of allergen-specific immunotherapy

BACKGROUND

Subcutaneous allergen-specific immunotherapy is an effective treatment of IgE-mediated allergies, but it requires repeated allergen injections with a risk of systemic allergic reactions. Transcutaneous immunotherapy may improve patient compliance and safety.

OBJECTIVE

To assess the safety and efficacy of epicutaneous allergen immunotherapy.

METHODS

This monocentric, placebo-controlled, double-blind trial was conducted from March 2006 to December 2007 at the University Hospital Zurich. Thirty-seven adult patients with positive skin prick and nasal provocation tests to grass pollen were randomized to receive patches containing either allergen (n = 21) or placebo (n = 16). Treatment took place before and during the pollen season 2006, and follow-up visits took place before (n = 26) and after the pollen season 2007 (n = 30). The primary outcome measures were nasal provocation tests.

RESULTS

Allergen-treated patients showed significantly decreased scores in nasal provocation tests in the first (P < .001) and second year (P = .003) after treatment. In contrast, placebo-treated patients had decreased scores in the first treatment year, 2006 (P = .03), but the effect diminished in the second year (P = .53). Although improvement of nasal provocation test scores was not significantly better in the verum versus placebo group, the overall treatment success was rated significantly higher by the allergen-treated group than by the placebo group (2006, P = .02; 2007, P = .005). No severe adverse events were observed. Occurrence of eczema after allergen patch applications proved stimulation of specific T-cell responses, but was noted as an adverse effect of the treatment.

CONCLUSION

Epicutaneous allergen immunotherapy is a promising strategy to treat allergies and merits further investigation.

Understanding human myeloid dendritic cell subsets for the rational design of novel vaccines

Dendritic cells (DCs) orchestrate a repertoire of immune responses that endows resistance to infection and tolerance to self. Understanding the principles by which DCs control immunity and tolerance has provided a rich basis for studying and improving clinical outcome of human disease treatment. Several features contribute to the complexity of the DC system. Among these, plasticity and existence of subsets are prominent determinants to the quality of the elicited immune responses. Indeed, different DC subsets are distributed in peripheral tissues and the blood and display different microbial receptors, surface molecules and cytokine expression, all of which influence the immunologic outcome. The biologic raison d'être for separate DC subsets has been the focus of many studies including our own and is being reviewed with an emphasis on human skin DCs.

Functional specializations of human epidermal Langerhans cells and CD14+ dermal dendritic cells

Little is known about the functional differences between the human skin myeloid dendritic cell (DC) subsets, epidermal CD207(+) Langerhans cells (LCs) and dermal CD14(+) DCs. We showed that CD14(+) DCs primed CD4(+) T cells into cells that induce naive B cells to switch isotype and become plasma cells. In contrast, LCs preferentially induced the differentiation of CD4(+) T cells secreting T helper 2 (Th2) cell cytokines and were efficient at priming and crosspriming naive CD8(+) T cells. A third DC population, CD14(-)CD207(-)CD1a(+) DC, which resides in the dermis, could activate CD8(+) T cells better than CD14(+) DCs but less efficiently than LCs. Thus, the human skin displays three DC subsets, two of which, i.e., CD14(+) DCs and LCs, display functional specializations, the preferential activation of humoral and cellular immunity, respectively.

Skin-derived dendritic cells induce potent CD8(+) T cell immunity in recombinant lentivector-mediated genetic immunization

The skin contains readily accessible dendritic cells (DCs) with potent antigen presentation function and functional plasticity enabling the integration of antigen specificity with environmentally responsive immune control. Recent studies challenge the established paradigm of cutaneous immune function by suggesting that lymph node-resident DCs, rather than skin-derived DCs (sDCs), are responsible for eliciting T cell immunity against cutaneous pathogens including viral vectors. We show that cutaneous delivery of lentivirus results in direct transfection of sDCs and potent and prolonged antigen presentation. Further, sDCs are the predominant antigen-presenting cells for the induction of potent and durable CD8(+) T cell immunity. These results support the classical paradigm of cutaneous immune function and suggest that antigen presentation by sDCs contributes to the high potency of lentivector-mediated genetic immunization.

Gene therapy for type 1 diabetes

The most intensively studied autoimmune disorder, type 1 diabetes mellitus (DM1), has attracted perhaps the greatest interest for gene-based therapeutic and prophylactic interventions. The final clinical manifestation of this immunologically and genetically complex disease, the absence of insulin, is the major starting point for almost all the gene therapy modalities attempted to date. Insulin replacement by transplantation of islets of Langerhans or surrogate beta cells is the obvious choice, but the allogeneic nature of the transplants activates potent antidonor immunoreactivity necessitating gene and cell-based immunosuppressive strategies as an alternative to the toxic pharmacologic immunosuppressives indicated for classic solid organ transplants. Accumulating knowledge of the cellular mechanisms involved in onset, however, have yielded promising tolerance induction prophylactic approaches using genes and cells. Despite the early successes in a number of animal models, the true test of efficacy in humans remains to be demonstrated.

Professional antigen-presenting cells of the skin

The skin functions as an important pro-inflammatory and immune organ. Accordingly, the epidermis and dermis are highly populated by dendritic cells (DC), which are potent antigen-presenting cells (APC) with important immunostimulatory and migratory activities. Whereas the biological characteristics and immunological functions of epidermal DC known as Langernahs cells (LC) have been the focus of intense research in the past, less is known regarding their dermal counterparts named dermal dendritic cells (DDC). Although it has been widely accepted that LC are the more relevant skin-resident APC, recent experimental evidence challenges this concept and proposes a different role for these important cell populations. In this article we compile recent scientific advances regarding the function of different skin-resident DC and we try to reconcile the new observations with the previously established paradigm.

Beneficial therapeutic effects with different particulate structures of murine polyomavirus VP1-coat protein carrying self or non-self CD8 T cell epitopes against murine melanoma

Polyomavirus-like-particles (PLPs) are empty, non-replicative, non-infectious particles that represent a potent antigen-delivery system against malignant disease. Protective anti-tumour immunity can be induced under therapy conditions by subcutaneous (s.c.) treatment with particulate antigenic structures like chimerical polyomavirus-pentamers (PPs). These PPs displaying an immunodominant H-2Kb-restricted ovalbumin (OVA)257-264 epitope evoked nearly complete tumour remission in MO5 (B16-OVA) melanoma-bearing C57BL/6 mice by two s.c. applications in a weekly interval. The immunotherapeutic intervention started at day 4 after melanoma implant. Furthermore, 40% of melanoma-bearing mice vaccinated with heterologous PPs carrying a H-2Kb-restricted cytotoxic T lymphocyte (CTL) epitope derived from of tyrosinase-related protein 2 (TRP2) survived similar treatment conditions. However, a late immunotherapeutic onset at day 10 post melanoma inoculation revealed no significant differences between the therapeutic values (40-60% survival) of VP1-OVA252-270 and VP1-TRP2180-192 PPs, respectively. These experiments underlined the capacity of PPs to break T cell tolerance against a differentially expressed self-antigen. As a correlate for preventive and therapeutic immunity against MO5 melanoma the number of OVA257-264- or TRP2180-188-specific CD8 T cells were significantly increased within the splenocyte population of treated mice as measured by H-2Kb-OVA257-264-PE tetramer staining or appropriate ELISPOT assays, respectively. These results reveal that heterologous PLPs and even chimerical PPs represent highly efficient antigen carriers for inducing CTL responses underlining their potential as immunotherapeutics against cancer.

Dendritic cell-tumor fusion vaccines for renal cell carcinoma

Renal cell carcinoma is a malignant disease that demonstrates resistance to standard chemotherapeutic agents. A promising area of investigation is the use of cancer vaccines to educate host immunity to specifically target and eliminate malignant cells. Dendritic cells (DCs) are potent antigen-presenting cells that are uniquely effective in generating primary immune responses. DCs that are manipulated to present tumor antigens induce antitumor immunity in animal models and preclinical human studies. A myriad of strategies have been developed to effectively load tumor antigen onto DCs, including the introduction of individual peptides, proteins, or tumor-specific genes, as well as the use of whole tumor cells as a source of antigen. A promising approach for the design of cancer vaccines involves the fusion of whole tumor cells with DCs. The DC-tumor fusion presents a spectrum of tumor-associated antigens to helper and cytotoxic T-cell populations in the context of DC-mediated costimulatory signals. In animal models, vaccination with DC-tumor fusions resulted in protection from tumor challenge and regression of established metastatic disease. We have conducted phase 1 dose escalation studies in which patients with metastatic breast and renal cancer underwent vaccination with DC-tumor fusions. Twenty-three patients underwent vaccination with autologous DC-tumor fusions. Vaccination was well tolerated without substantial treatment-related toxic effects. Immunologic responses and disease regression were observed in a subset of patients. Future studies will explore the effect of DC maturation and cytokine adjuvants on vaccine potency.

Epicutaneous application of CpG oligodeoxynucleotides with peptide or protein antigen promotes the generation of CTL

Immunostimulatory oligodeoxynucleotides (ODN) are effective adjuvants in the induction of humoral and cellular immune responses when administered parenterally with antigen. The skin has recently become a target organ for the design of non-invasive vaccine technologies. Using ovalbumin (OVA) as a model antigen, we demonstrate that the application of ODN sequences to tape-stripped skin promotes the induction of potent cytotoxic T lymphocyte (CTL) responses to co-administered peptide. Induction of peptide-specific CTL required the presence of CpG motifs within the ODN. CTL afforded tumor protection against a tumor expressing an immunodominant OVA CTL epitope. CTL could also be induced to whole protein administered onto the skin. Differential CpG sequence activity was noted with respect to the induction of CTL to epicutaneous protein with an ODN sequence containing a poly-G motif having an optimal effect. Peptide-specific CTL could be detected in the peripheral blood as early as 6 d after a single immunization. These results highlight the potential of the bare skin as a route for vaccine development and indicate an important role for immunostimulatory ODN as adjuvants to generate functional CTL with the help of the skin immune system.

Antennapedia transduction sequence promotes anti tumour immunity to epicutaneously administered CTL epitopes

The identification of tumor antigens has spurred the development of efficient adjuvants and novel delivery systems for cancer immunotherapy. To this end, a peptide-based vaccine consisting of the Antennapedia transduction sequence (ANTP) attached to an antigenic peptide was designed to enhance per-cutaneous delivery into cells of the epidermis and dermis. Here we show that the topical application of OVA(257-264) linked to ANTP in mice onto tape-stripped skin resulted in enhanced delivery of the antigen through the skin whereas OVA(257-264) alone remained distributed uniformly on the skin surface. This delivery correlated with an increase in the CTL response against OVA. When mixed with CpG oligodinucleotides (ODN), the recombinant antigen protected mice from tumor challenge. These data provide the first indication that in vivo use of a translocation sequence can enhance delivery of therapeutic peptides and increase anti-tumor immunity through a simple and safe mechanism involving enhanced penetration of the skin barrier.

CTL-Dependent and -Independent Antitumor Immunity Is Determined by the Tumor Not the Vaccine

Previously, we compared the efficiency of direct injection with an adenovirus (Ad) expressing human gp100 (hgp100) to immunization with dendritic cells (DC) loaded with the same vector ex vivo. The DC vaccine provided the greatest protection against challenge with B16F10 melanoma, and antitumor immunity was found to be CD8(+) T cell-independent. In the current study, we sought to determine whether lack of CD8(+) T cell-mediated antitumor immunity was a function of the vaccine platform or the tumor line. Both Ad and DC/Ad vaccines elicited CD8(+) CTL reactive against hgp100 and provided protection against B16F10 engineered to express hgp100 demonstrating that both vaccination platforms can effectively generate protective CD8(+) T cell-mediated immunity. The hgp100-induced CTL cross-reacted with murine gp100 (mgp100) and lysed B16F10 cells pulsed with mgp100 peptide indicating that the resistance of B16F10 cells to CTL elicited by hgp100 vaccination may be due to a defect in processing of the endogenous mgp100. Indeed, introduction of the TAP-1 cDNA into B16F10 rendered the cells sensitive to lysis by gp100-specific CTL. Furthermore, gp100-immunized mice were protected from challenge with B16F10-TAP1 cells through a mechanism dependent upon CD8(+) T cells. These results demonstrate that tumor phenotype, not the vaccination platform, ultimately determines CD8(+) or CD4(+) T cell-mediated tumor clearance.

Optimization of epicutaneous immunization for the induction of CTL

The immune system of the skin has recently been exploited for the development of non-invasive vaccine technologies. However, one of the limitations of current vaccine protocols is the inefficient priming of cytotoxic T lymphocytes (CTL). In this study, we report that the application of either an immunodominant class I MHC restricted ovalbumin peptide or whole ovalbumin protein, to tape-stripped skin together with the co-application of the bacterial enterotoxin cholera toxin (CT) induces antigen-specific CTL. Tape-stripping (TS) was found to enhance the magnitude of antibody responses to co-administered protein and to promote the generation of antigen-specific IgG(2a) responses. As well, both cholera toxin and tape-stripping enhanced epidermal dendritic cell (DC) immigration into draining lymph nodes. The adjuvant effect of co-administered cholera toxin and tape-stripping in promoting CTL priming was not dependent on IL-12. Epicutaneous immunization has previously been shown to induce robust antibody responses to administered protein antigen. We now demonstrate the induction of robust and persistent CTL responses to epicutaneously administered protein antigen. Epicutaneous immunization is cheap, simple and effective. These findings suggest the potential use of the skin for the generation of protective immune responses to both viral and tumor challenge.

Gene and cell therapies for diabetes mellitus: strategies and clinical potential

The last 5 years have witnessed an explosion in the use of genes and cells as biomedicines. While primarily aimed at cancer, gene engineering and cell therapy strategies have additionally been used for Mendelian, neurodegenerative and metabolic disorders. The main focus of gene and cell therapy strategies in metabolism has been diabetes mellitus. This disease is a disorder of glucose homeostasis, either due to the immune-mediated eradication of pancreatic beta cells in the islets of Langerhans (type 1 diabetes) or resulting from insulin resistance and obesity syndromes where the insulin-producing capability of the beta cell is ultimately exhausted in the face of insensitivity to the effects of insulin in the peripheral glucose-utilising tissues (type 2 diabetes). A significant number of animal studies have demonstrated the potential in restoring normoglycaemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of type 1 diabetes or rodent recipients of allogeneic/xenogeneic islet transplants. The achievements of gene and cell therapy in type 2 diabetes are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease. Here we present an overview of the current status of gene and cell therapy for type 1 and 2 diabetes and we propose potential therapeutic options that could be clinically useful. For type 1 diabetes, transplantation of islets engineered to evade or suppress the recipient immune response is the most readily-available technology today. A number of gene delivery vectors encoding proteins that impair a variety of immune cells have already been examined and proven versatile. More challenging but, nonetheless, just over the horizon are attempts to promote tolerance to islet allografts. Type 2 diabetes will likely require a better understanding of the processes that determine insulin sensitivity in the periphery. Targeting tissues such as muscle and fat with vectors encoding genes whose products promote insulin sensitivity and glucose uptake is an approach that does not carry with it the side-effects often associated with pharmacologic agents currently in use. In the end, progress in vector design, elucidation of antigen-specific immunity and insulin sensitivity will provide the framework for gene drug use in the treatment of type 1 and type 2 diabetes.

Effects of lipofectin-antigen complexes on major histocompatibility complex class I-restricted antigen presentation pathway in murine dendritic cells and on dendritic cell maturation

We previously reported that exogenous antigens complexed with the cationic liposome lipofectin (LF) were efficiently presented via major histocompatibility complex (MHC) class I molecules on pulsed dendritic cells (DCs) in vitro. In the present study, we demonstrated that MHC class I-restricted antigen presentation on DC2.4 cells, a murine immature DC line, treated with LF-antigen complexes was remarkably suppressed through the inhibition of endocytosis, proteasome catalysis, and Golgi transport. We also found that LF did not influence expression of interleukin-12 p40 mRNA, MHC molecules, or co-stimulatory molecules in DC2.4 cells. These findings suggest that an antigen-loading procedure using LF could enhance delivery of exogenous antigens to the classical MHC class I pathway in DCs, but it does not initiate DC maturation.

Protective immunity to UV radiation-induced skin tumours induced by skin grafts and epidermal cells

There is little evidence that cutaneous dendritic cells (DC), including epidermal Langerhans cells (LC), can induce immunity to UV radiation (UVR)-induced skin tumours. Here, it is shown that cells within skin can induce protective antitumour immunity against a UVR-induced fibrosarcoma. Transplantation of the skin overlying subcutaneous tumours onto naïve recipients could induce protective antitumour immunity, probably because the grafting stimulated the tumour Ag-loaded DC to migrate to local lymph nodes. This suggests that cutaneous APC can present tumour Ag to induce protective antitumour immunity. Previously, it has been shown that immunization of mice with MHC class II+ epidermal cells (EC) pulsed with tumour extracts could induce delayed-type hypersensitivity against tumour cells. Here, this same immunization protocol could induce protective immunity against a minimum tumorigenic dose of UVR-induced fibrosarcoma cells, but not higher doses. Epidermal cells obtained from semiallogeneic donors and pulsed with tumour extract could also induce protective immunity. However, presentation of BSA Ag from the culture medium was found to contribute to this result using semiallogeneic EC. The results suggest that LC overlying skin tumours may be able to induce protective immunity to UVR-induced tumours if stimulated to migrate from the skin.

Cutaneous vaccination: the skin as an immunologically active tissue and the challenge of antigen delivery

Vaccination is one of the major achievements of modern medicine. As a result of vaccination, diseases such as polio and measles have been controlled and small pox has been eradicated. However, despite these successes there are still many microbial diseases that cause tremendous suffering because there is no vaccine or the vaccines available are inadequate. In addition, even if vaccines were available for all infectious diseases there is no guarantee that people would use them routinely. One of the major impediments to ensuring vaccine efficacy and compliance is that of delivery. Presently most vaccines are given by intramuscular administration. Unfortunately this is often traumatic, especially in infants. Thus, if it was possible to replace intramuscular immunization by mucosal (oral/intranasal) or transdermal delivery it may be possible to both enhance mucosal immunity as well as improve overall compliance rates. The transdermal route has been used by the pharmaceutical industry for the delivery of various low molecular weight drugs. Some of the approaches used for smaller compounds may also have potential for delivery of either protein or polynucleotide vaccines. However, there is a greater challenge to delivering large molecular weight molecules through the skin due to size, charge and other physicochemical properties. This review will describe the recent advances that have been made in dermal and topical delivery as related to vaccines.

Human tumour and dendritic cell hybrids generated by electrofusion: potential for cancer vaccines

Hybrid cells created by fusion of antigen presenting and tumour cells have been shown to induce potent protective and curative anti-tumour immunity in rodent cancer models. The application of hybrid cell vaccines for human tumour therapy and the timely intervention in disease control are limited by the requirement to derive sufficient autologous cells to preserve homologous tumour antigen presentation. In this study, the efficiency of various methods of electrofusion in generating hybrid human cells have been investigated with a variety of human haemopoietic, breast and prostate cell lines. Cell fusion using an electrical pulse is enhanced by a variety of stimuli to align cells electrically or bring cells into contact. Centrifugation of cells after an exponential pulse from a Gene Pulser electroporation apparatus provided the highest yield of mixed cell hybrids by FACS analysis. An extensive fusogenic condition generated in human cells after an electrical pulse contradicts the presumption that prior cell contact is necessary for cell fusion. Alignment of cells in a concurrent direct current charge and osmotic expansion of cells in polyethylene glycol also generated high levels of cell fusion. Waxing of one electrode of the electroporation cuvette served to polarize the fusion chamber and increase cell fusion 5-fold. Optimisation of a direct current charge in combination with a fusogenic pulse in which fusion of a range of human cells approached or exceeded 30% of the total pulsed cells. The yield of hybrid prostate and breast cancer cells with dendritic cells was similar to the homologous cell fusion efficiencies indicating that dendritic cells were highly amenable to fusion with human tumour cells under similar electrical parameters. Elimination of unfused cells by density gradient and culture is possible to further increase the quantity of hybrid cells. The generation and purification of quantities of hybrid cells sufficient for human vaccination raises the possibility of rapid, autologous tumour antigen presenting vaccines for trial with common human tumours.

Percutaneous peptide immunization via corneum barrier-disrupted murine skin for experimental tumor immunoprophylaxis

H-2K(b)-restricted tumor epitope peptides, including tyrosinase-related protein 2 residues 181-188 (TRP-2) and connexin 37 residues 52-59 (MUT1), were applied to permeability barrier-disrupted C57BL/6 (B6) mouse skin from which the stratum corneum of the epidermis had been removed by tape-stripping. This procedure primed tumor-specific cytotoxic T lymphocytes (CTLs) in the lymph nodes and spleen, protected mice against subsequent challenge with corresponding tumor cells, and suppressed the growth of established tumors. Preventive and therapeutic effectiveness was correlated with the frequency of tumor-specific CTL precursors. MHC class II Ia(b+) cells separated from tape-stripped skin, compared with those from intact skin, exhibited a strong antigen-presenting capacity for CTL, suggesting that CTL expansion after peptide application is primarily mediated by epidermal Langerhans cells. Thus, percutaneous peptide immunization via barrier-disrupted skin provides a simple and noninvasive means of inducing potent anti-tumor immunity which may be exploited for cancer immunotherapy.

Dendritic cells: development, function and potential use for cancer immunotherapy

Dendritic cells (DC) are potent antigen presenting cells that are essential for the initiation of primary immune responses. They richly express MHC, costimulatory and adhesion molecules necessary for the stimulation of naive T cell populations. Dendritic cells are located at sites of antigen capture where they demonstrate phagocytic capacity and subsequently migrate to lymphatic areas for antigen presentation. Their phenotypic and functional characteristics are intimately linked to their stage of maturation. The hematopoietic development of dendritic cells is distinct and may follow several precursor pathways some closely linked to monocytes. Generation of large numbers of cells for potential clinical use has recently been accomplished through the in vitro culturing of progenitors with cytokines. The use of dendritic cell vaccines for cancer immunotherapy has emerged as an exciting new focus of investigation. Various strategies have been adopted to introduce tumor antigens into dendritic cells so that they may be more effectively presented to T cells in the context of costimulation. Animal models demonstrate that dendritic cell tumor vaccines reverse T-cell anergy and result in subsequent tumor rejection. Incorporating the expanding knowledge of dendritic cell biology into vaccine design is essential for the generation of effective immunotherapy for cancer patients.

Cytotoxic T Cell Responses to DNA Vaccination: Dependence on Antigen Presentation via Class II MHC

This study was designed to test whether cytotoxic T cell (CTL) responses to DNA vaccination are dependent upon MHC class II-restricted priming of CD4+ T cells. Because DNA vaccination may directly transfect dendritic cells, and dendritic cells may be capable of directly stimulating CD8+ T cell responses, such priming might be unnecessary. To test this hypothesis, C57BL/6 mice were immunized intramuscularly or intradermally with DNA encoding either whole OVA, a class I (Kb)-restricted peptide epitope of OVA (amino acids 257–264, SIINFEKL), or this class I-restricted epitope plus the adjacent class II (I-Ab)-restricted epitope of OVA (amino acids 265–280, TEWTSSNVMEERKIKV). Very low to negligible CTL responses were observed in mice vaccinated with the SIINFEKL construct, whereas mice vaccinated with the SIINFEKLTEWTSSNVMEERKIKV or with the complete OVA construct made equally robust CTL responses. These responses were sensitive to blocking by anti-CD8 mAb and were shown to be SIINFEKL-specific by using SIINFEKL peptide-pulsed EL-4 cells as targets. To ensure that the generation of these CTL responses was indeed dependent upon CD4+ T cell help, mice were depleted of either CD4+ or CD8+ cells before immunization. Depletion of CD4+ cells completely abrogated the CTL response to OVA DNA, as did depletion of CD8+ cells. Thus, we conclude that the CTL response to both intramuscular and intradermal DNA vaccination is highly dependent upon the generation of CD4+ T cell help via a class II MHC-dependent pathway. These results will be relevant for the construction of minimal-epitope vaccines for DNA immunization.

Murine Langerhans Cells Cultured Under Serum-Free Conditions Mature into Potent Stimulators of Primary Immune Responses In Vitro and In Vivo

The ability of Ag-pulsed dendritic cells (DC) to induce primary immune responses has led them to be used for vaccination purposes. However, irrelevant Ags (e.g., FCS) can also be taken up by DC during their isolation and culture and then presented in vivo. To circumvent this, we have established a serum-free (SF) culture system. Murine epidermal cell (EC) suspensions were prepared with and without FCS and cultured for 3 days either in SF or FCS-containing medium. In spite of the lower Langerhans cell (LC) yields under SF conditions, both SF- and FCS-cultured LC (SF-cLC, FCS-cLC) underwent a similar maturation process, as evidenced by a similar increase in the cell surface expression of MHC class II and of costimulatory molecules. The further observation that SF-EC cultures elaborated comparable amounts of granulocyte-macrophage (GM)-CSF as FCS-cultured EC, but were relatively impaired in their IL-1α and TNF-α production, supports the role of GM-CSF in LC maturation and, less so, in LC survival. Functionally, freshly isolated SF-LC compared with FCS-LC in their Ag-processing capacity. Three-day-cultured SF-LC were as potent stimulators of polyclonal T cell responses and of the primary allogeneic MLR as FCS-cLC, but were relatively poor activators of naive, syngeneic CD4+ T cells. In vivo, hapten-modified SF-cLC induced a contact hypersensitivity response similar in magnitude and kinetics to that evoked by FCS-cLC. Our data show that, in the absence of serum and exogenous cytokines, LC mature into potent activators of T cell responses and could thus be a valuable cellular source for DC-based immunotherapy.

CD8+ cytolytic T lymphocytes and the skin

T lymphocytes show a special affinity for the skin. Although the roles played by the CD4+ population of T lymphocytes in immunodermatology were so far actively investigated, much less is known about the roles played in the skin by CD8+ cytolytic T lymphocytes (CTL). The activity of CD8+ CTL in the immunodermatological context, however, is likely to be most important; the immuno-biology itself of CD8+ CTL, moreover, although far from being fully understood, shows intriguing characteristics. Immunophenotype, function and cytokine profile of CD8+ CTL are overviewed in the first section of this review. Phenotypically, not only CD8+ CTL can be subdivided into CD8+ CD28+ CD11b- and CD8+ CD28- CD11b+ subsets, but also an up-to-now undetected CD8+ CD28- CD11b- subset does exist. Functionally, not only "cytotoxic" but even "suppressor" subpopulations have been shown to exert cytolytic capabilities indeed, and "suppression" itself may be due to such a lytic capacity. According to cytokine synthesis, CD8+ CTL can be split into Tc1 and Tc2 subsets, each able to influence specific patterns of immune responses. The impact of CD8+ CTL in immunodermatology, overviewed in the second section of the current review, is crucial. The pathophysiology of inflammatory dermatoses is deeply influenced by the activity of CD8+ CTL: e.g., CD8+ CTL within psoriatic epidermis are possibly associated to the persistence of psoriatic lesions not undergoing resolution; on the other hand, in late lesions of lichen planus CD8+ CTL predominate, thus explaining presumably both the cytolytic attack against keratinocytes and the modulation of the inflammatory reaction up to the final resolution of the lesions, Tc1 cells are decreased in atopic dermatitis, and such a decrease can account both for IgE overproduction and for development of infections. Finally, CD8+ CTL can sustain against cutaneous viruses/tumors cytolytic immune responses not only of secondary but even of primary type, i.e. induced by Langerhans cells/dendritic cells either transfected or pulsed with skin virus/tumor-associated antigens, thus allowing the production of vaccines against cutaneous viral/neoplastic diseases.

Specific autologous anti-melanoma T cell response in vitro using monocyte-derived dendritic cells

Dendritic cells (DC) are antigen-presenting cells initiating primary and secondary immune responses. Since malignant tumors are able to escape immunologic control, DC might be prime candidates to activate the immune system against tumor cells. In an autologous system, a dynamic interaction among monocyte-derived DC (MoDC), T lymphocytes, and tumor cells obtained from melanoma patients could be noted. MoDC were generated from blood monocytes in the presence of GM-CSF, IL-4, and IFN-gamma. T cells were isolated either from peripheral blood or from lymph nodes. Melanoma cells were harvested from surgically removed tumor metastases. They were then gamma-irradiated and co-cultured with autologous MoDC and T lymphocytes. After 5 days, the lymphocytes showed a high proliferative activity and the majority of them were CD8-positive. In five cases tested, they revealed a high cytotoxic activity resulting in apoptosis of tumor cells. These findings suggest that MoDC are capable of initiating an effective specific anti-tumor response in a strictly autologous mixed lymphocyte tumor culture (MLTC), even though tumor-specific antigens had not been individually defined. Therefore (I) whole melanoma cells can serve as a source of antigen, (II) monocyte-derived dendritic cells may process and present melanoma-specific antigens resulting in a strong lymphocyte proliferation, (III) the majority of responding T lymphocytes are CD8-positive, and (IV) an acquired cytotoxic response eventually leads to apoptosis of the melanoma cells. The reaction demonstrated here permits to in vitro and quantitatively monitoring the effect of T cell directed immunotherapies such as the adoptive immunotherapy of tumors.

Anthrax toxin-mediated delivery in vivo and in vitro of a cytotoxic T-lymphocyte epitope from ovalbumin

We reported earlier that a nontoxic form of anthrax toxin was capable of delivering a cytotoxic T-lymphocyte (CTL) epitope in vivo, such that a specific CTL response was primed against the epitope. The epitope, of bacterial origin, was fused to an N-terminal fragment (LFn) from the lethal-factor component of the toxin, and the fusion protein was injected, together with the protective antigen (PA) component, into BALB/c mice. Here we report that PA plus LFn is capable of delivering a different epitope--OVA(257-264) from ovalbumin. Delivery was accomplished in a different mouse haplotype, H-2Kb and occurred in vitro as well as in vivo. An OVA(257-264)-specific CTL clone, GA-4, recognized EL-4 cells treated in vitro with PA plus as little as 30 fmol of the LFn-OVA(257-264) fusion protein. PA mutants attenuated in toxin self-assembly or translocation were inactive, implying that the role of PA in epitope delivery is the same as that in toxin action. Also, we showed that OVA(257-264)-specific CTL could be induced to proliferate by incubation with splenocytes treated with PA plus LFn-OVA(257-264). These findings imply that PA-LFn may serve as a general delivery vehicle for CTL epitopes in vivo and as a safe, efficient tool for the ex vivo expansion of patient-derived CTL for use in adoptive immunotherapy.