Laser-assisted intradermal delivery of adjuvant-free vaccines targeting XCR1+ dendritic cells induces potent antitumoral responses

The anti-influenza M2e antibody response is promoted by XCR1 targeting in pig skin

XCR1 is selectively expressed on a conventional dendritic cell subset, the cDC1 subset, through phylogenetically distant species. The outcome of antigen-targeting to XCR1 may therefore be similar across species, permitting the translation of results from experimental models to human and veterinary applications. Here we evaluated in pigs the immunogenicity of bivalent protein structures made of XCL1 fused to the external portion of the influenza virus M2 proton pump, which is conserved through strains and a candidate for universal influenza vaccines. Pigs represent a relevant target of such universal vaccines as pigs can be infected by swine, human and avian strains. We found that cDC1 were the only cell type labeled by XCR1-targeted mCherry upon intradermal injection in pig skin. XCR1-targeted M2e induced higher IgG responses in seronegative and seropositive pigs as compared to non-targeted M2e. The IgG response was less significantly enhanced by CpG than by XCR1 targeting, and CpG did not further increase the response elicited by XCR1 targeting. Monophosphoryl lipid A with neutral liposomes did not have significant effect. Thus altogether M2e-targeting to XCR1 shows promises for a trans-species universal influenza vaccine strategy, possibly avoiding the use of classical adjuvants.

Dendritic Cell Strategies for Eliciting Mutation-Derived Tumor Antigen Responses in Patients

Dendritic cells (DCs) are equipped for sensing danger signals and capturing, processing, and presenting antigens to naive or effector cells and are critical in inducing humoral and adaptive immunity. Successful vaccinations are those that activate DCs to elicit both cellular and humoral responses, as well as long-lasting memory response against the target of interest. Recently, it has become apparent that tumor cells can provide new sources of antigens through nonsynonymous mutations or frame-shift mutations, leading to potentially hundreds of mutation-derived tumor antigens (MTAs) or neoantigens. T cells recognizing MTA have been detected in cancer patients and can even lead to tumor regression. Designing MTA-specific vaccination strategies will have to take into account the adjuvant activity of DC subsets and the best formulation to elicit an effective immune response. We discuss the potential of human DCs to prime MTA-specific responses.

Allergen-loaded strontium-doped hydroxyapatite spheres improve allergen-specific immunotherapy in mice

BACKGROUND

Immunomodulatory interventions play a key role in the treatment of infections and cancer as well as allergic diseases. Adjuvants such as micro- and nanoparticles are often added to immunomodulatory therapies to enhance the triggered immune response. Here, we report the immunological assessment of novel and economically manufactured microparticle adjuvants, namely strontium-doped hydroxyapatite porous spheres (SHAS), which we suggest for the use as adjuvant and carrier in allergen-specific immunotherapy (ASIT).

METHODS AND RESULTS

Scanning electron microscopy revealed that the synthesis procedure developed for the production of SHAS results in a highly homogeneous population of spheres. Strontium-doped hydroxyapatite porous spheres bound and released proteins such as ovalbumin (OVA) or the major cat allergen Fel d 1. SHAS-OVA were taken up by human monocyte-derived dendritic cells (mdDCs) and murine DCs and did not have any necrotic or apoptotic effects even at high densities. In a murine model of ASIT for allergic asthmatic inflammation, we found that OVA released from subcutaneously injected SHAS-OVA led to a sustained stimulation of both CD4⁺ and CD8⁺ T cells. Allergen-specific immunotherapy with SHAS-OVA as compared to soluble OVA resulted in similar humoral responses but in a higher efficacy as assessed by symptom scoring.

CONCLUSION

We conclude that SHAS may constitute a suitable carrier and adjuvant for ASIT with great potential due to its unique protein-binding properties.

Progress in research on C-chemokine XCL1

XCL1, also known as lymphotactin, is the only known member of the C-type-chemokine family, which is produced mainly by CD8⁺ T cells and natural killer cells. XCL1 has a unique amino acid sequence feature and two interchangeable conformations, which makes XCL1 different from other chemokines in structure and function. The XCL1-specific receptor, XCR1, is a member of the G-protein-coupled receptor family and plays an important role in the negative selection of T cells in the thymus and in the initiation of cross-antigen presentation and mediation of cytotoxic immune responses. XCL1 can regulate the balance of the immune system and maintain intestinal immune homeostasis, and it is involved in a variety of diseases such as autoimmune diseases, nephritis, tuberculosis and human immunodeficiency virus infection. In recent years, the selective expression of XCR1 on CD8⁺ DCs with strong cross antigen-presention ability has been proved, which has led to studies using XCL1 for mucosal immunization, antitumor immunotherapy and targeted vaccine development.

The Identification and Distribution of Cattle XCR1 and XCL1 among Peripheral Blood Cells: New Insights into the Design of Dendritic Cells Targeted Veterinary Vaccine

The chemokine (C motif) receptor 1 (XCR1) and its ligandXCL1 have been intensively studied in the mouse and human immune systems. Here, we determined the molecular characteristics of cattle XCR1 and XCL1 and their distribution among peripheral blood cells. Cattle XCR1 mRNA expression was mainly restricted to CD26+CADM1+CD205+MHCII+CD11b- cells in blood that were otherwise lineage marker negative (lin-); these represented a subset of classic dendritic cells (DCs), not plasmacytoid DCs. Some of these DCs expressed CD11a, CD44, CD80 and CD86, but they did not express CD4, CD8, CD163 or CD172a. Cattle XCL1 was expressed in quiescent NK cells and in activated CD8+ T cells. Cattle XCR1+ DCs migrated chemotactically in response to mouse, but not to human, XCL1. The distribution characters of cattle XCR1 and XCL1 suggested a vital role in regulation of acquired immune responses and indicated a potential for a DC targeted veterinary vaccine in cattle using XCL1 fused antigens.

Skin vaccination via fractional infrared laser ablation - Optimization of laser-parameters and adjuvantation

BACKGROUND

Methods to deliver an antigen into the skin in a painless, defined, and reproducible manner are essential for transcutaneous immunization (TCI). Here, we employed an ablative fractional infrared laser (P.L.E.A.S.E. Professional) to introduce clinically relevant vaccines into the skin. To elicit the highest possible antibody titers with this system, we optimized different laser parameters, such as fluence and pore number per area, and tested various adjuvants.

METHODS

BALB/c mice were immunized with Hepatitis B surface antigen (HBsAg) by laser-microporation. Adjuvants used were alum, CRM₁₉₇, monophosphoryl lipid A, heat-labile enterotoxin subunit B of E. coli (LT-B), and CpG ODN1826. The influence of different fluences (2.1 to 16.8J/cm²) and pore densities (5-15%) was investigated. Furthermore, immunogenicity of HBsAg and the commercially available conjugate vaccines ActHIB® and Menveo® applied via TCI was compared to standard i.m. injection. Antigen-specific antibody titers were assessed by luminometric ELISA.

RESULTS

Antibody titers against HBsAg were dependent on pore depth and peaked at a fluence of 8.4J/cm². Immunogenicity was independent of pore density. Adjuvantation with alum significantly reduced antibody titers after TCI, whereas other adjuvants only induced marginal changes in total IgG titers. LT-B and CpG shifted the polarization of the immune response as indicated by decreased IgG1/IgG2a ratios. HBsAg/LT-B applied via TCI induced similar antibody titers compared to i.m. injection of HBsAg/alum. In contrast to i.m. injection, we observed a dose response from 5 to 20μg after TCI. Both, ActHIB® and Menveo® induced high antibody titers after TCI, which were comparable to i.m. injection.

CONCLUSIONS

Alum, the most commonly used adjuvant, is contraindicated for transcutaneous vaccination via laser-generated micropores. TCI with optimized laser parameters induces high antibody titers, which cannot be significantly increased by the tested adjuvants. Commercially available vaccines formulated without alum have the potential for successful TCI via laser-generated micropores, without the need for reformulation.

Hapten-Specific T Cell-Mediated Skin Inflammation: Flow Cytometry Analysis of Mouse Skin Inflammatory Infiltrate

Hapten-specific T cell-mediated skin inflammation also known as contact hypersensitivity (CHS) is characterized by a strong influx of CD8⁺ cytotoxic T cells within the skin upon reexposure of sensitized individuals to the same hapten. As many other leukocytes are also recruited during this elicitation phase, we attempted to revisit the skin infiltrate and characterize the inflammatory pattern. Recent improvement in the isolation in conventional as well as inflammatory dendritic cell and macrophage subsets from tissues and in the use of appropriate surface markers unraveling their heterogeneity should allow to determinate their specific functions in the CHS model. Here, we describe procedures to extract those cells from the skin and to analyze them by flow cytometry using a combination of appropriate surface markers allowing further transcriptomic analysis and functional assays.

Dendritic cell-based immunotherapy

Immunotherapy using dendritic cell (DC)-based vaccination is an approved approach for harnessing the potential of a patient's own immune system to eliminate tumor cells in metastatic hormone-refractory cancer. Overall, although many DC vaccines have been tested in the clinic and proven to be immunogenic, and in some cases associated with clinical outcome, there remains no consensus on how to manufacture DC vaccines. In this review we will discuss what has been learned thus far about human DC biology from clinical studies, and how current approaches to apply DC vaccines in the clinic could be improved to enhance anti-tumor immunity.

Expanding the tools for identifying mononuclear phagocyte subsets in swine: Reagents to porcine CD11c and XCR1

Pig is a domestic species of major importance in the agro-economy and in biomedical research. Mononuclear phagocytes (MNP) are organized in subsets with specialized roles in the orchestration of the immune response and new tools are awaited to improve MNP subset identification in the pig. We cloned pig CD11c cDNA and generated a monoclonal antibody to pig CD11c which showed a pattern of expression by blood and skin MNP subsets similar to humans. We also developed a porcine XCL1-mCherry dimer which specifically reacted with the XCR1-expressing dendritic cell subset of the type 1 lineage in blood and skin. These original reagents will allow the efficient identification of pig MNP subsets to study their role in physiological and pathological processes and also to target these cells in novel intervention and vaccine strategies for veterinary applications and preclinical evaluations.

Laser Therapy Inhibits Tumor Growth in Mice by Promoting Immune Surveillance and Vessel Normalization

Laser therapy, recently renamed as photobiomodulation, stands as a promising supportive treatment for oral mucositis induced by oncological therapies. However, its mechanisms of action and, more importantly, its safety in cancer patients, are still unclear. Here we explored the anti-cancer effect of 3 laser protocols, set at the most commonly used wavelengths, in B16F10 melanoma and oral carcinogenesis mouse models. While laser light increased cell metabolism in cultured cells, the in vivo outcome was reduced tumor progression. This striking, unexpected result, was paralleled by the recruitment of immune cells, in particular T lymphocytes and dendritic cells, which secreted type I interferons. Laser light also reduced the number of highly angiogenic macrophages within the tumor mass and promoted vessel normalization, an emerging strategy to control tumor progression. Collectively, these results set photobiomodulation as a safety procedure in oncological patients and open the way to its innovative use for cancer therapy.

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Laser light reduces tumor progression while increasing metabolism of cultured cells

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Laser-treated tumors contain mature vessels and less pro-angiogenic macrophages

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Tumors treated by photobiomodulation are surrounded by lymphocytes and dendritic cells

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Laser light promotes secretion of type I interferons in vitro and in vivo

Laser therapy, also named photobiomodulation, is recommended to heal mucositis induced by oncological treatments, raising concerns on its safe use in cancer patients. Ottaviani et al. showed that laser light inhibits tumor progression, induces tumor vessel normalization and stimulates the immune system to produce type I interferons, proving the safety and extending the use of laser-based therapies to cancer.

Classification of Laser Vaccine Adjuvants

An immunologic adjuvant, which enhances the magnitude and quality of immune responses to vaccine antigens, has become an essential part of modern vaccine practice. Chemicals and biologicals have been typically used for this purpose, but there are an increasing number of studies that are being conducted on the vaccine adjuvant effect of laser light on the skin. Currently, four different types or classes of laser devices have been shown to systemically enhance immune responses to intradermal vaccination: ultra-short pulsed lasers, non-pulsed lasers, non-ablative fractional lasers and ablative fractional lasers. Aside from involving the application of laser light to the skin in a manner that minimizes discomfort and damage, each type of laser vaccine adjuvant involves emission parameters, modes of action and immunologic adjuvant effects that are quite distinct from each other. This review provides a summary of the four major classes of “laser vaccine adjuvant” and clarifies and resolves their characteristics as immunologic adjuvants. These aspects of each adjuvant’s properties will ultimately help define which laser would be most efficacious in delivering a specific clinical benefit with a specific vaccine.

Fractional Laser Ablation for the Cutaneous Delivery of Triamcinolone Acetonide from Cryomilled Polymeric Microparticles: Creating Intraepidermal Drug Depots

The efficacy of some dermatological therapies might be improved by the use of "high dose" intraepidermal drug reservoir systems that enable sustained and targeted local drug delivery, e.g., in the treatment of keloids and hypertrophic scars. Here, a fractionally ablative erbium:YAG laser was used to enable "needle-less" cutaneous deposition of polymeric microparticles containing triamcinolone acetonide (TA). The microparticles were prepared using a freeze-fracture technique employing cryomilling that resulted in drug loading efficiencies of ∼100%. They were characterized by several different techniques, including scanning electron microscopy, powder X-ray diffraction and differential scanning calorimetry. TA was quantified by validated HPLC-UV and UHPLC-MS/MS analytical methods. In vitro release studies demonstrated the effect of polymer properties on TA release kinetics. Confocal laser scanning microscopy enabled visualization of cryomilled microparticles containing fluorescein and Nile Red in the cutaneous micropores and the subsequent release of fluorescein into the micropores and its diffusion throughout the epidermis and upper dermis. The biodistribution of TA, i.e. the amount of drug as a function of depth in skin, following microparticle application was much more uniform than with a TA suspension and delivery was selective for deposition with less transdermal permeation. These findings suggest that this approach may provide an effective, targeted and minimally invasive alternative to painful intralesional injections for the treatment of keloid scars.

Functional Specialization of Skin Dendritic Cell Subsets in Regulating T Cell Responses

Dendritic cells (DC) are a heterogeneous family of professional antigen-presenting cells classically recognized as most potent inducers of adaptive immune responses. In this respect, Langerhans cells have long been considered to be prototypic immunogenic DC in the skin. More recently this view has considerably changed. The generation of in vivo cell ablation and lineage tracing models revealed the complexity of the skin DC network and, in particular, established the existence of a number of phenotypically distinct Langerin⁺ and negative DC populations in the dermis. Moreover, by now we appreciate that DC also exert important regulatory functions and are required for the maintenance of tolerance toward harmless foreign and self-antigens. This review summarizes our current understanding of the skin-resident DC system in the mouse and discusses emerging concepts on the functional specialization of the different skin DC subsets in regulating T cell responses. Special consideration is given to antigen cross-presentation as well as immune reactions toward contact sensitizers, cutaneous pathogens, and tumors. These studies form the basis for the manipulation of the human counterparts of the murine DC subsets to promote immunity or tolerance for the treatment of human disease.

Polarizing T and B Cell Responses by APC-Targeted Subunit Vaccines

Current influenza vaccines mostly aim at the induction of specific neutralizing antibodies. While antibodies are important for protection against a particular virus strain, T cells can recognize epitopes that will offer broader protection against influenza. We have previously developed a DNA vaccine format by which protein antigens can be targeted specifically to receptors on antigen presenting cells (APCs). The DNA-encoded vaccine proteins are homodimers, each chain consisting of a targeting unit, a dimerization unit, and an antigen. The strategy of targeting antigen to APCs greatly enhances immune responses as compared to non-targeted controls. Furthermore, targeting of antigen to different receptors on APCs can polarize the immune response to different arms of immunity. Here, we discuss how targeting of hemagglutinin to MHC class II molecules increases Th2 and IgG1 antibody responses, whereas targeting to chemokine receptors XCR1 or CCR1/3/5 increases Th1 and IgG2a responses, in addition to CD8(+) T cell responses. We also discuss these results in relation to work published by others on APC-targeting. Differential targeting of APC surface molecules may allow the induction of tailor-made phenotypes of adaptive immune responses that are optimal for protection against various infectious agents, including influenza virus.