Vitiligo: advances in pathophysiology research and treatment development

The autoimmune condition vitiligo, characterized by skin depigmentation, presents challenges for effective treatment design, with Janus kinase (JAK) inhibitors and other repurposed drugs offering a promising strategy for symptom management. This review explores advantages and shortcomings of current therapies, while presenting the urgent need for further innovative approaches. We emphasize the growing understanding of autoimmune involvement in vitiligo, highlighting several novel treatment avenues including relieving melanocyte stress, preventing dendritic cell activation, halting T cell migration, and suppressing inflammation and autoimmunity. Integrating psychodrama therapy to remediate stress alongside medical interventions marks a holistic approach to enhance patient well-being. The molecular underpinnings of vitiligo care are covered, emphasizing exciting advances revolutionizing vitiligo treatment and improving the quality of life for affected individuals.

Topical antibiotics limit depigmentation in a mouse model of vitiligo

Oral neomycin administration impacts the gut microbiome and delays vitiligo development in mice, and topical antibiotics may likewise allow the microbiome to preserve skin health and delay depigmentation. Here, we examined the effects of 6-week topical antibiotic treatment on vitiligo-prone pmel-1 mice. Bacitracin, Neosporin, or Vaseline were applied to one denuded flank, while the contralateral flank was treated with Vaseline in all mice. Ventral depigmentation was quantified weekly. We found that topical Neosporin treatment significantly reduced depigmentation and exhibited effects beyond the treated area, while Bacitracin ointment had no effect. Stool samples collected from four representative mice/group during treatment revealed that Neosporin treatment aligned with reduced abundance of the Alistipes genus in the gut, while relevant changes to the skin microbiome at end point were less apparent. Either antibiotic treatment led to reduced expression of MR1, potentially limiting mucosal-associated invariant T-cell activation, while Neosporin-treated skin selectively revealed significantly reduced CD8+ T-cell abundance. The latter finding aligned with reduced expression of multiple inflammatory markers and markedly increased regulatory T-cell density. Our studies on favorable skin and oral antibiotic treatment share the neomycin compound, and in either case, microbial changes were most apparent in stool samples. Taken together, neomycin-containing antibiotic applications can mediate skin Treg infiltration to limit vitiligo development. Our study highlights the therapeutic potential of short-term antibiotic applications to limit depigmentation vitiligo.

Immune Assessment Today: Optimizing and Standardizing Efforts to Monitor Immune Responses in Cancer and Beyond

As part of a symposium, current and former directors of Immune Monitoring cores and investigative oncologists presented insights into the past, present and future of immune assessment. Dr. Gnjatic presented a classification of immune monitoring technologies ranging from universally applicable to experimental protocols, while emphasizing the need for assay harmonization. Dr. Obeng discussed physiologic differences among CD8 T cells that align with anti-tumor responses. Dr. Lyerly presented the Soldano Ferrone lecture, commemorating the passionate tumor immunologist who inspired many, and covered a timeline of monitoring technology development and its importance to immuno-oncology. Dr. Sonabend presented recent achievements in glioblastoma treatment, accentuating the range of monitoring techniques that allowed him to refine patient selection for clinical trials. Dr. Guevara-Patiño focused on hypoxia within the tumor environment and stressed that T cell viability is not to be confused with functionality. Dr. Butterfield accentuated monitoring of dendritic cell metabolic (dys)function as a determinant for tumor vaccine success. Lectures were interspersed with select abstract presentations. To summarize the concepts, Dr. Maecker from Stanford led an informative forum discussion, pointing towards the future of immune monitoring. Immune monitoring continues to be a guiding light towards effective immunotherapeutic strategies.

Skin Infiltrate Composition as a Telling Measure of Responses to Checkpoint Inhibitors

Checkpoint inhibitors treat a variety of tumor types with significant benefits. Unfortunately, these therapies come with diverse adverse events. Skin rash is observed early into treatment and might serve as an indicator of downstream responses to therapy. We studied the cellular composition of cutaneous eruptions and whether their contribution varies with the treatment applied. Skin samples from 18 patients with cancer and 11 controls were evaluated by mono- and multiplex imaging, quantification, and statistical analysis. T cells were the prime contributors to skin rash, with T cells and macrophages interacting and proliferating on site. Among T cell subsets examined, type 1 and 17 T cells were relatively increased among inflammatory skin infiltrates. A combination of increased cytotoxic T cell content and decreased macrophage abundance was associated with dual checkpoint inhibition over PD1 inhibition alone. Importantly, responders significantly separated from nonresponders by greater CD68+ macrophage and either CD11c+ antigen-presenting cell or CD4+ T cell abundance in skin rash. The microenvironment promoted epidermal proliferation and thickening as well. The combination of checkpoint inhibitors used affects the development and composition of skin infiltrates, whereas the combined abundance of two cell types in cutaneous eruptions aligns with responses to checkpoint inhibitor therapy.

Increased Otoferlin Expression in B Cells Is Associated with Muscle Weakness in Untreated Juvenile Dermatomyositis: A Pilot Study

Otoferlin mRNA expression is increased in JDM patients' PBMCs and muscle compared to healthy controls. This study aims to evaluate the role of otoferlin in JDM disease pathophysiology and its association with disease activity in untreated children with JDM. A total of 26 untreated JDM (88.5% female, 92.3% white, non-Hispanic) and 15 healthy controls were included in this study. Otoferlin mRNA expression was determined by qRT-PCR before and a few months after therapy. Detailed flow cytometry of various cell surface markers and cytoplasmic otoferlin was performed to identify cells expressing otoferlin. In addition, muscle otoferlin expression was evaluated in situ in six untreated JDM patients and three healthy controls. There was a significant increase in otoferlin expression in JDM children compared to controls (Median 67.5 vs. 2.1; p = 0.001). There was a positive correlation between mRNA otoferlin expression and the following disease activity markers: disease activity scores (DAS)-total (rs = 0.62, p < 0.001); childhood myositis assessment scale (CMAS) (rs = -0.61, p = 0.002); neopterin (rs = 0.57, p = 0.004) and von Willebrand factor antigen (vWF: Ag) (rs = 0.60, p = 0.004). Most of the otoferlin-positive cells were unswitched B cells (63-99.4%), with 65-75% of them expressing plasmablast markers (CD19+, IgM+, CD38hi, CD24-). The findings of this pilot study suggest that otoferlin expression is associated with muscle weakness, making it a possible biomarker of disease activity. Additionally, B cells and plasmablasts were the primary cells expressing otoferlin.

Melanocyte-keratinocyte cross-talk in vitiligo

Vitiligo is a common acquired pigmentary disorder that presents as progressive loss of melanocytes from the skin. Epidermal melanocytes and keratinocytes are in close proximity to each other, forming a functional and structural unit where keratinocytes play a pivotal role in supporting melanocyte homeostasis and melanogenesis. This intimate relationship suggests that keratinocytes might contribute to ongoing melanocyte loss and subsequent depigmentation. In fact, keratinocyte dysfunction is a documented phenomenon in vitiligo. Keratinocyte apoptosis can deprive melanocytes from growth factors including stem cell factor (SCF) and other melanogenic stimulating factors which are essential for melanocyte function. Additionally, keratinocytes control the mobility/stability phases of melanocytes via matrix metalloproteinases and basement membrane remodeling. Hence keratinocyte dysfunction may be implicated in detachment of melanocytes from the basement membrane and subsequent loss from the epidermis, also potentially interfering with repigmentation in patients with stable disease. Furthermore, keratinocytes contribute to the autoimmune insult in vitiligo. Keratinocytes express MHC II in perilesional skin and may present melanosomal antigens in the context of MHC class II after the pigmented organelles have been transferred from melanocytes. Moreover, keratinocytes secrete cytokines and chemokines including CXCL-9, CXCL-10, and IL-15 that amplify the inflammatory circuit within vitiligo skin and recruit melanocyte-specific, skin-resident memory T cells. In summary, keratinocytes can influence vitiligo development by a combination of failing to produce survival factors, limiting melanocyte adhesion in lesional skin, presenting melanocyte antigens and enhancing the recruitment of pathogenic T cells.

Targeting ULK1 Decreases IFNγ-Mediated Resistance to Immune Checkpoint Inhibitors

Immune checkpoint inhibitors (ICI) have transformed the treatment of melanoma. However, the majority of patients have primary or acquired resistance to ICIs, limiting durable responses and patient survival. IFNγ signaling and the expression of IFNγ-stimulated genes correlate with either response or resistance to ICIs, in a context-dependent manner. While IFNγ-inducible immunostimulatory genes are required for response to ICIs, chronic IFNγ signaling induces the expression of immunosuppressive genes, promoting resistance to these therapies. Here, we show that high levels of Unc-51 like kinase 1 (ULK1) correlate with poor survival in patients with melanoma and overexpression of ULK1 in melanoma cells enhances IFNγ-induced expression of immunosuppressive genes, with minimal effects on the expression of immunostimulatory genes. In contrast, genetic or pharmacologic inhibition of ULK1 reduces expression of IFNγ-induced immunosuppressive genes. ULK1 binds IRF1 in the nuclear compartment of melanoma cells, controlling its binding to the programmed death-ligand 1 promoter region. In addition, pharmacologic inhibition of ULK1 in combination with anti-programmed cell death protein 1 therapy further reduces melanoma tumor growth in vivo. Our data suggest that targeting ULK1 represses IFNγ-dependent immunosuppression. These findings support the combination of ULK1 drug-targeted inhibition with ICIs for the treatment of patients with melanoma to improve response rates and patient outcomes.

IMPLICATIONS

This study identifies ULK1, activated downstream of IFNγ signaling, as a druggable target to overcome resistance mechanisms to ICI therapy in metastatic melanoma.

Acceleration of melanocyte senescence by the proinflammatory cytokines IFNγ and TNFα impairs the repigmentation response of vitiligo patients to narrowband ultraviolet B (NBUVB) phototherapy

Vitiligo is a chronic autoimmune disease characterized by the T helper 1 (Th1) cytokine-driven immune destruction of melanocytes (MCs). Although narrowband ultraviolet B (NBUVB) phototherapy has been proven to be an effective therapeutic option, the repigmentation response to that phototherapy varies greatly in different vitiligo patients. Here, we demonstrate that there is an increase of NBUVB-induced cellular senescence in vitiligo MCs exposed to Th1 cytokine interferon γ (IFNγ) and/or tumor necrosis factor α (TNFα) in lesional vitiligo skin from poor responders who had undergone NBUVB phototherapy. Supplementation with exogenous recombinant human stem cell factor (rhSCF) in the culture medium as well as the lentiviral vector-mediated overexpression of cKIT could prevent the MCs from the IFNγ/TNFα-accelerated cellular senescence. Mechanistic studies indicated that the reduced ratio of membrane-bound KIT (mKIT) to the soluble form of KIT (sKIT) is directly related to the cellular senescence of vitiligo MCs following exposure to IFNγ and TNFα. Furthermore, the matrix metalloprotease 9 (MMP9) inhibitor GM6001 attenuates the production of sKIT via the suppression of cKIT ectodomain shedding. Altogether, our study indicates that the presence of Th1 cytokines IFNγ and/or TNFα in the epidermal milieu might impair the repigmentation response of vitiligo patients to NBUVB phototherapy.

SARA suppresses myofibroblast precursor transdifferentiation in fibrogenesis in a mouse model of scleroderma

We previously reported that Smad anchor for receptor activation (SARA) plays a critical role in maintaining epithelial cell phenotype. Here, we show that SARA suppressed myofibroblast precursor transdifferentiation in a mouse model of scleroderma. Mice overexpressing SARA specifically in PDGFR-β+ pericytes and pan-leukocytes (SARATg) developed significantly less skin fibrosis in response to bleomycin injection compared with wild-type littermates (SARAWT). Single-cell RNA-Seq analysis of skin PDGFR-β+ cells implicated pericyte subsets assuming myofibroblast characteristics under fibrotic stimuli, and SARA overexpression blocked the transition. In addition, a cluster that expresses molecules associated with Th2 cells and macrophage activation was enriched in SARAWT mice, but not in SARATg mice, after bleomycin treatment. Th2-specific Il-31 expression was increased in skin of the bleomycin-treated SARAWT mice and patients with scleroderma (or systemic sclerosis, SSc). Receptor-ligand analyses indicated that lymphocytes mediated pericyte transdifferentiation in SARAWT mice, while with SARA overexpression the myofibroblast activity of pericytes was suppressed. Together, these data suggest a potentially novel crosstalk between myofibroblast precursors and immune cells in the pathogenesis of SSc, in which SARA plays a critical role.

Benign tumors in TSC are amenable to treatment by GD3 CAR T cells in mice

Mutations underlying disease in tuberous sclerosis complex (TSC) give rise to tumors with biallelic mutations in TSC1 or TSC2 and hyperactive mammalian target of rapamycin complex 1 (mTORC1). Benign tumors might exhibit de novo expression of immunogens, targetable by immunotherapy. As tumors may rely on ganglioside D3 (GD3) expression for mTORC1 activation and growth, we compared GD3 expression in tissues from patients with TSC and controls. GD3 was overexpressed in affected tissues from patients with TSC and also in aging Tsc2+/^– mice. As GD3 overexpression was not accompanied by marked natural immune responses to the target molecule, we performed preclinical studies with GD3 chimeric antigen receptor (CAR) T cells. Polyfunctional CAR T cells were cytotoxic toward GD3-overexpressing targets. In mice challenged with Tsc2^–/– tumor cells, CAR T cells substantially and durably reduced the tumor burden, correlating with increased T cell infiltration. We also treated aged Tsc2+/^– heterozygous (>60 weeks) mice that carry spontaneous Tsc2^–/– tumors with GD3 CAR or untransduced T cells and evaluated them at endpoint. Following CAR T cell treatment, the majority of mice were tumor free while all control animals carried tumors. The outcomes demonstrate a strong treatment effect and suggest that targeting GD3 can be successful in TSC.

HSP70iQ435A to subdue autoimmunity and support anti-tumor responses

Developing immunosuppressive therapies for autoimmune diseases comes with a caveat that immunosuppression may promote the risk of developing other conditions or diseases. We have previously shown that biolistic delivery of an expression construct encoding inducible HSP70 (HSP70i) with one amino acid modification in the dendritic cell (DC) activating moiety 435-445 (HSP70iQ435A) to mouse skin resulted in significant immunosuppressive activity of autoimmune vitiligo, associated with fewer tissue infiltrating T cells. To prepare HSP70iQ435A as a potential therapeutic for autoimmune vitiligo, in this study we evaluated whether and how biolistic delivery of HSP70iQ435A in mice affects anti-tumor responses. We found that HSP70iQ435A in fact supports anti-tumor responses in melanoma-challenged C57BL/6 mice. Biolistic delivery of the HSP70iQ435A-encoding construct to mice elicited significant anti-HSP70 titers, and anti-HSP70 IgG and IgM antibodies recognize surface-expressed and cytoplasmic HSP70i in human and mouse melanoma cells. A peptide scan revealed that the anti-HSP70 antibodies recognize a specific C-terminal motif within the HSP70i protein. The antibodies elicited surface CD107A expression among mouse NK cells, representative of antibody-mediated cellular cytotoxicity (ADCC), supporting the concept, that HSP70iQ435A-encoding DNA elicits a humoral response to the stress protein expressed selectively on the surface of melanoma cells. Thus, besides limiting autoimmunity and inflammation, HSP70iQ435A elicits humoral responses that limit tumor growth and may be used in conjunction with immune checkpoint inhibitors to not only control tumor but to also limit adverse events following tumor immunotherapy.

A Palette of Cytokines to Measure Anti-Tumor Efficacy of T Cell-Based Therapeutics

Cytokines are key molecules within the tumor microenvironment (TME) that can be used as biomarkers to predict the magnitude of anti-tumor immune responses. During immune monitoring, it has been customary to predict outcomes based on the abundance of a single cytokine, in particular IFN-γ or TGF-β, as a readout of ongoing anti-cancer immunity. However, individual cytokines within the TME can exhibit dual opposing roles. For example, both IFN-γ and TGF-β have been associated with pro- and anti-tumor functions. Moreover, cytokines originating from different cellular sources influence the crosstalk between CD4+ and CD8+ T cells, while the array of cytokines expressed by T cells is also instrumental in defining the mechanisms of action and efficacy of treatments. Thus, it becomes increasingly clear that a reliable readout of ongoing immunity within the TME will have to include more than the measurement of a single cytokine. This review focuses on defining a panel of cytokines that could help to reliably predict and analyze the outcomes of T cell-based anti-tumor therapies.

Myron Gordon Award paper: Microbes, T-cell diversity and pigmentation

Melanocytes are static, minimally proliferative cells. This leaves them vulnerable in vitiligo. Yet upon malignant transformation, they form vicious tumors. This profound switch in physiology is accompanied by genetic change and is driven by environmental factors. If UV exposure in younger years supports malignant transformation and melanoma formation, it can likewise impart mutations on melanocytes that reduce their viability, to initiate vitiligo. A wide variety of microbes can influence these diametrically opposed outcomes before either disease takes hold. These microbes are vehicles of change that we are only beginning to study. Once a genetic modification occurs, there is a wide variety of immune cells ready to respond. Though it does not act alone, the T cell is among the most decisive responders in this process. The same biochemical process that offered the skin protection by producing melanin can become an Achilles heel for the cell when the T cells target melanosomal enzymes or, on occasion, neoantigens. T cells are precise, determined, and consequential when they strike. Here, we probe the relationship between the microbiome and its metabolites, epithelial integrity, and the activation of T cells that target benign and malignant melanocytes in vitiligo and melanoma.

Engineered antigen-specific regulatory T cells for autoimmune skin conditions

Regulatory T cells (Tregs) are a subset of T cells responsible for the regulation of immune responses, thereby maintaining immune homeostasis and providing immune tolerance to both self and non-self-antigens. An increasing number of studies revealed Treg numbers and functions in a variety of autoimmune diseases. Treg deficiency can cause the development of several autoimmune skin diseases including vitiligo, alopecia areata, pemphigoid and pemphigus, psoriasis, and systemic sclerosis. Many clinical trials have been performed for autoimmune conditions using polyclonal Tregs, but efficiency can be significantly improved using antigen-specific Tregs engineered using T cell receptor (TCR) or chimeric antigen receptor (CAR) constructs. In this review, we systematically reviewed altered frequencies, impaired functions, and phenotypic features of Tregs in autoimmune skin conditions. We also summarized new advances in TCR and CAR based antigen-specific Tregs tested both in animal models and in clinics. The advantages and limitations of each approach were carefully discussed emphasizing possible clinical relevance to patients with autoimmune skin diseases. Moreover, we have reviewed potential approaches for engineering antigen-specific Tregs, and strategies for overcoming possible hurdles in clinical applications. Thereby, antigen-specific Tregs can be infused using autologous adoptive cell transfer to restore Treg numbers and to provide local immune tolerance for autoimmune skin disorders.

Antigen Specificity Enhances Disease Control by Tregs in Vitiligo

Vitiligo is an autoimmune skin disease characterized by melanocyte destruction. Regulatory T cells (Tregs) are greatly reduced in vitiligo skin, and replenishing peripheral skin Tregs can provide protection against depigmentation. Ganglioside D3 (GD3) is overexpressed by perilesional epidermal cells, including melanocytes, which prompted us to generate GD3-reactive chimeric antigen receptor (CAR) Tregs to treat vitiligo. Mice received either untransduced Tregs or GD3-specific Tregs to test the hypothesis that antigen specificity contributes to reduced autoimmune reactivity in vitro and in vivo. CAR Tregs displayed increased IL-10 secretion in response to antigen, provided superior control of cytotoxicity towards melanocytes, and supported a significant delay in depigmentation compared to untransduced Tregs and vehicle control recipients in a TCR transgenic mouse model of spontaneous vitiligo. The latter findings were associated with a greater abundance of Tregs and melanocytes in treated mice versus both control groups. Our data support the concept that antigen-specific Tregs can be prepared, used, and stored for long-term control of progressive depigmentation.

Adoptive T-Cell Transfer to Treat Lymphangioleiomyomatosis

Patients with lymphangioleiomyomatosis (LAM) develop pulmonary cysts associated with neoplastic, smooth muscle-like cells that feature neuroendocrine cell markers. The disease preferentially affects premenopausal women. Existing therapeutics do not cure LAM. As gp100 is a diagnostic marker expressed by LAM lesions, we proposed to target this immunogenic glycoprotein using TCR transgenic T cells. To reproduce the genetic mutations underlying LAM, we cultured Tsc2^-/- kidney tumor cells from aged Tsc2 heterozygous mice and generated a stable gp100-expressing cell line by lentiviral transduction. T cells were isolated from major histocompatibility complex-matched TCR transgenic pmel-1 mice to measure cytotoxicity in vitro, and 80% cytotoxicity was observed within 48 hours. Antigen-specific cytotoxicity was likewise observed using pmel-1 TCR-transduced mouse T cells, suggesting that transgenic T cells may likewise be useful to treat LAM in vivo. On intravenous injection, slow-growing gp100⁺ LAM-like cells formed lung nodules that were readily detectable in severe combined immunodeficient/beige mice. Adoptive transfer of gp100-reactive but not wild-type T cells into mice significantly shrunk established lung tumors, even in the absence of anti-PD-1 therapy. These results demonstrate the treatment potential of adoptively transferred T cells to eliminate pulmonary lesions in LAM.

A Rapid Method for Multispectral Fluorescence Imaging of Frozen Tissue Sections

Multispectral fluorescence imaging on formalin-fixed paraffin-embedded (FFPE) tissues enables the detection of multiple markers in a single tissue sample that can provide information about antigen coexpression and spatial distribution of the markers. However, a lack of suitable antibodies for formalin-fixed tissues may restrict the nature of markers that can be detected. In addition, the staining method is time-consuming. Here we describe a rapid method to perform multispectral fluorescence imaging on frozen tissues. The method includes the fluorophore combinations used, detailed steps for the staining of mouse and human frozen tissues, and the scanning, acquisition, and analysis procedures. For staining analysis, a commercially available semiautomated multispectral fluorescence imaging system is used. Through this method, up to six different markers were stained and detected in a single frozen tissue section. The machine learning analysis software can phenotype cells that can be used for quantitative analysis. The method described here for frozen tissues is useful for the detection of markers that cannot be detected in FFPE tissues or for which antibodies are not available for FFPE tissues.

Antibiotics Drive Microbial Imbalance and Vitiligo Development in Mice

Vitiligo is impacted by environmental triggers. We studied the contribution of the microbiome in FH mice, in which depigmentation is mediated by tyrosinase-reactive T cells. The mice received oral antibiotics and were monitored for depigmentation. The microbiome was studied in fecal and skin samples using 16S rRNA analysis. The resulting T-cell distributions were evaluated. In untreated mice, pigment loss did not expand to the pelage, whereas mice in the ampicillin group were approximately 1/3 depigmented at 30 weeks. In contrast to models of autoimmunity that are less dependent on IFN-γ, ampicillin but not neomycin treatment correlated with accelerated disease and reduced bacteria in the fecal pellets. Modified cytokine patterns in the tissue and serum suggest a response that transcends the gut. Ampicillin-induced depigmentation was accompanied by gut but not skin dysbiosis, and reduced T cell numbers in both sites. Neomycin induced a redistribution of gut T cells and an accumulation of skin regulatory T cells. This treatment spurred a Bacteroides-dominated population of fecal bacteria. Reduced diversity is prominent particularly after ampicillin treatment, when the gut is dominated by Pseudomonas species. In line with current concepts relating the microbiome and the immune system, we predict that dietary measures might promote skin health and delay vitiligo onset.

Transgenerational transfer of gene-modified T cells

Tumor immunotherapy using gene-modified T cells has already met with considerable success in the treatment of metastatic melanoma and B cell lymphoma. With improving patient prognoses, new questions arise. In particular, the long-term consequences of treatment among individuals of childbearing age could now be considered. Former patients can carry a cohort of transgenic memory T cells long after treatment has ceased and the effector T cell population has contracted. When patients become parents well after treatment is completed, expectant mothers may still pass transgenic T cells to their unborn children. Consequences should be more measurable if the mother also breastfeeds the baby. Maternal T cells may shape immune responses in the child, can tolerize the child to maternal antigens, and might cause either beneficial or adverse effects in the offspring. The hypothesis put forth is that transgenic T cells transferred from mother to child during and after pregnancy might have consequences that have not been adequately considered to date. Depending on the targeted antigen and the MHC eventually required to present it, such transfer may be beneficial, uneventful or even damaging. Such potential consequences are addressed in this paper. The transgenic T cells might form a pocket of memory T cells in secondary lymphoid organs of the child, expand upon antigen stimulation, and react. However, simple measures might be devised to avoid any reason for concern. These considerations provide ample incentive to probe transgenerational transfer of transgenic T cells.

Molecular properties of gp100-reactive T-cell receptors drive the cytokine profile and antitumor efficacy of transgenic host T cells

To study the contribution of T-cell receptors (TCR) to resulting T-cell responses, we studied three different human αβ TCRs, reactive to the same gp100-derived peptide presented in the context of HLA-A*0201. When expressed in primary CD8 T cells, all receptors elicited classic antigen-induced IFN-γ responses, which correlated with TCR affinity for peptide-MHC in the order T4H2 > R6C12 > SILv44. However, SILv44 elicited superior IL-17A release. Importantly, in vivo, SILv44-transgenic T cells mediated superior antitumor responses to 888-A2 + human melanoma tumor cells upon adoptive transfer into tumor-challenged mice while maintaining IL-17 expression. Modeling of the TCR ternary complexes suggested architectural differences between SILv44 and the other complexes, providing a potential structural basis for the observed differences. Overall, the data reveal a more prominent role for the T-cell receptor in defining host T-cell physiology than traditionally assumed, while parameters beyond IFN-γ secretion and TCR affinity ultimately determine the reactivity of tumor-reactive T cells.

HSP70iQ435A-Encoding DNA Repigments Vitiligo Lesions in Sinclair Swine

Human HSP70i_Q435A carries a single amino-acid modification within the dendritic cell activating region and tolerizes dendritic cells in vitro. The underlying DNA was used to prevent and treat disease in vitiligo mouse models through reduced dendritic cell activation and diminished skin T-cell infiltration, suggesting the same may be useful for patients. Physiologic differences between mouse and human skin then called for studies in large animals with human-like skin. We established the efficiency of DNA jet injection into swine skin before subcloning HSP70i_Q435A into clinically suitable vector pUMVC3. Vitiligo lesions in Sinclair swine were treated with plasmid DNA to measure changes in depigmentation, T-cell infiltration, expression of HSP70i in skin, serum HSP70i, and anti-HSP70i serum titers. Remarkable repigmentation following HSP70i_Q435A-encoding DNA treatment persisted throughout the 6-month follow-up period. Repigmentation was accompanied by an initial influx of T cells accompanied by increased CD4/CD8 ratios, waning by week 15. Melanocytes spanned the border of repigmenting skin, suggesting that melanocyte repopulation precedes skin melanization. Serum titer fluctuations were not treatment-associated. Importantly, treatment did not interfere with melanoma immunosurveillance. These data encourage clinical testing of HSP70i_Q435A.

The convergence theory for vitiligo: A reappraisal

Vitiligo is characterized by progressive loss of skin pigmentation. The search for aetiologic factors has led to the biochemical, the neurologic and the autoimmune theory. The convergence theory was then proposed several years ago to incorporate existing theories of vitiligo development into a single overview of vitiligo aetiology. The viewpoint that vitiligo is not caused only by predisposing mutations, or only by melanocytes responding to chemical/radiation exposure, or only by hyperreactive T cells, but rather results from a combination of aetiologic factors that impact melanocyte viability, has certainly stood the test of time. New findings have since informed the description of progressive depigmentation. Understanding the relative importance of such aetiologic factors combined with a careful selection of the most targetable pathways will continue to drive the next phase in vitiligo research: the development of effective therapeutics. In that arena, it is likewise important to acknowledge that pathways affected in some patients may not be altered in others. Taken together, the convergence theory continues to provide a comprehensive viewpoint of vitiligo aetiology. The theory serves to intertwine aetiologic pathways and will help to define pathways amenable to disease intervention in individual patients.

Replenishing Regulatory T Cells to Halt Depigmentation in Vitiligo

Vitiligo is a cutaneous autoimmune disease, especially devastating to patients with darker skin tones because of the contrast between unaffected and lesional skin. We studied immune cells infiltrating vitiligo skin and found very few regulatory T cells (Tregs). Vitiligo was not associated with a reduced frequency or function of circulating Tregs. To manipulate Treg function, we used mouse models expressing melanocyte-reactive TCRs, following changes in pelage color. We also isolated splenocytes to measure Treg function and evaluated cutaneous Treg abundance. Even small numbers of Tregs transferred into depigmenting mice could effectively interfere with depigmentation. The same holds true for treatment with rapamycin, readily translatable for use in human patients; such treatment may be well tolerated. Because vitiligo skin is relatively devoid of cells that produce the chemokine CCL22, whereas circulating Tregs express normal levels of its receptor CCR4, we overexpressed Ccl22 in the skin of vitiligo-prone mice to assess the resulting levels of depigmentation. Markedly reduced depigmentation was accompanied by Treg infiltration to the skin. With several options available to support a healthy balance between Tregs and effector T cells, the next challenge will be to render such treatment antigen specific and avoid general immunosuppression.

Clinical and immunologic evaluation of three metastatic melanoma patients treated with autologous melanoma-reactive TCR-transduced T cells

Malignant melanoma incidence has been increasing for over 30 years, and despite promising new therapies, metastatic disease remains difficult to treat. We describe preliminary results from a Phase I clinical trial (NCT01586403) of adoptive cell therapy in which three patients received autologous CD4⁺ and CD8⁺ T cells transduced with a lentivirus carrying a tyrosinase-specific TCR and a marker protein, truncated CD34 (CD34t). This unusual MHC Class I-restricted TCR produces functional responses in both CD4⁺ and CD8⁺ T cells. Parameters monitored on transduced T cells included activation (CD25, CD69), inhibitory (PD-1, TIM-3, CTLA-4), costimulatory (OX40), and memory (CCR7) markers. For the clinical trial, T cells were activated, transduced, selected for CD34t⁺ cells, then re-activated, and expanded in IL-2 and IL-15. After lymphodepleting chemotherapy, patients were given transduced T cells and IL-2, and were followed for clinical and biological responses. Transduced T cells were detected in the circulation of three treated patients for the duration of observation (42, 523, and 255 days). Patient 1 tolerated the infusion well but died from progressive disease after 6 weeks. Patient 2 had a partial response by RECIST criteria then progressed. After progressing, Patient 2 was given high-dose IL-2 and subsequently achieved complete remission, coinciding with the development of vitiligo. Patient 3 had a mixed response that did not meet RECIST criteria for a clinical response and developed vitiligo. In two of these three patients, adoptive transfer of tyrosinase-reactive TCR-transduced T cells into metastatic melanoma patients had clinical and/or biological activity without serious adverse events.

“TCR transgenic, gp100 reactive T cells to target lymphangioleiomyomatosis”

Lymphangioleiomyomatosis (LAM) is a rare lung disease presenting with benign tumors, affecting premenopausal women. LAM is diagnosed by HMB45 staining. We questioned whether gp100 expression by lesional cells lends opportunities to treat LAM by adoptive T cell transfer. As LAM tumors are sparsely infiltrated by T cells, we looked to melanoma and vitiligo as sources of gp100-reactive TCRs. The gp100-reactive TCRs T4H2, R6C12 and SILv44 were cloned into retro-and lentiviral vectors and introduced into primary human CD8+ T cells. Transgenic T cells were combined with melanoma cells, melanocytes and LAM cells and responses were measured by ELISA detecting IFN-γ, IL-17, TNF or IL-4 after 48 hrs. Cytotoxicity was measured by 51Cr release and CD107a expression, and in vivo using SCID/Beige mice challenged with 106 888A2 human melanoma cells and treated twice with 106 SILv44 transduced T cells. Transgenic T cells conferred specific reactivity to HLA-A2+, gp100+ cells, including human LAM10224 cells, in vitro. The SILv44 TCR mediated most IL-17a expression whereas INF-γ secretion was greatest in T4H2 transduced cells. Surprisingly, IL17a expression decreased with increasing peptide concentrations. IL17a+, SILv44+ T cells conferred most anti-tumor protection in mice. LAM10224 cells can form tumors in immunodeficient mice, and SILv44 transgenic T cells should likewise contain such tumors. Thus, SILv44 transgenic T cells may serve as a viable treatment for LAM.

Alpha-N-acetyl-neuraminide alpha-2,8-sialyltransferase 1 can support immune responses toward tumors overexpressing ganglioside D3 in mice

An immunotherapeutic strategy is discussed supporting anti-tumor activity toward malignancies overexpressing ganglioside D3. GD3 can be targeted by NKT cells when derived moieties are presented in the context of CD1d. NKT cells can support anti-tumor responses by secreting inflammatory cytokines and through cytotoxicity toward CD1d+GD3+ tumors. To overexpress GD3, we generated expression vector DNA and an adenoviral vector encoding the enzyme responsible for generating GD3 from its ubiquitous precursor GM3. We show that DNA encoding α-N-acetyl-neuraminide α-2,8-sialyltransferase 1 (SIAT8) introduced by gene gun vaccination in vivo leads to overexpression of GD3 and delays tumor growth. Delayed tumor growth is dependent on CD1d expression by host immune cells, as shown in experiments engaging CD1d knockout mice. A trend toward greater NKT cell populations among tumor-infiltrating lymphocytes is associated with SIAT8 vaccination. A single adenoviral vaccination introduces anti-tumor activity similarly to repeated vaccination with naked DNA. Here, greater NKT tumor infiltrates were accompanied by marked overexpression of IL-17 in the tumor, later switching to IL-4. Our results suggest that a single intramuscular adenoviral vaccination introduces overexpression of GD3 by antigen-presenting cells at the injection site, recruiting NKT cells that provide an inflammatory anti-tumor environment. We propose adenoviral SIAT8 (AdV-SIAT8) can slow the growth of GD3 expressing tumors in patients.

Ccl22 Diverts T Regulatory Cells and Controls the Growth of Melanoma

T regulatory cells (Treg) avert autoimmunity, but their increased levels in melanoma confer a poor prognosis. To explore the basis for Treg accumulation in melanoma, we evaluated chemokine expression in patients. A 5-fold increase was documented in the Treg chemoattractants CCL22 and CCL1 in melanoma-affected skin versus unaffected skin, as accompanied by infiltrating FoxP3⁺ T cells. In parallel, there was an approximately two-fold enhancement in expression of CCR4 in circulating Treg but not T effector cells. We hypothesized that redirecting Treg away from tumors might suppress autoimmune side effects caused by immune checkpoint therapeutics now used widely in the clinic. In assessing this hypothesis, we observed a marked increase in skin Treg in mice vaccinated with Ccl22, with repetitive vaccination sufficient to limit Treg accumulation and melanoma growth in the lungs of animals challenged by tumor cell injection, whether using a prevention or treatment protocol design. The observed change in Treg accumulation in this setting could not be explained by Treg conversion. Overall, our findings offered a preclinical proof of concept for the potential use of CCL22 delivered by local injection as a strategy to enhance the efficacious response to immune checkpoint therapy while suppressing its autoimmune side effects. Cancer Res; 76(21); 6230-40. ©2016 AACR.

Functional cloning of a gp100-reactive T-cell receptor from vitiligo patient skin

We isolated gp100-reactive T cells from perilesional skin of a patient with progressive vitiligo with superior reactivity toward melanoma cells compared with tumor-infiltrating lymphocytes 1520, a melanoma-derived T-cell line reactive with the same cognate peptide. After dimer enrichment and limited dilution cloning, amplified cells were subjected to reverse transcription and 5' RACE to identify the variable TCRα and TCRβ subunit sequences. The full-length sequence was cloned into a retroviral vector separating both subunits by a P2A slippage sequence and introduced into Jurkat cells and primary T cells. Cytokine secreted by transduced cells in response to cognate peptide and gp100-expressing targets signifies that we have successfully cloned a gp100-reactive T-cell receptor from actively depigmenting skin.

Vitiligo treatment demystified: a flowchart for stratified treatment approaches

The recent publication by Anbar et al. in the April issue of this journal, delineating and prioritizing treatment options for vitiligo, is both timely and significant. First and foremost, this work brings to the forefront the important message that vitiligo truly is a treatable disease. All too often, patients refrain from seeking treatment as public opinion dictates that vitiligo is not an important disease, there are no effective treatments available, and insurance will not cover attempts to treat. By providing clear guidelines of treatments to be considered, practicing physicians seeing an occasional vitiligo patient will be more readily inclined to explore the possibilities currently available for enhancing the quality of life of this patient group.

Targeting melanocyte and melanoma stem cells by 8-hydroxy-2-dipropylaminotetralin

Monobenzyl ether of hydroquinone (MBEH) is cytotoxic towards melanocytes. Its treatment efficacy is limited by an inability to eradicate stem cells. By contrast, 8-hydroxy-N,N-dipropyl-2-aminotetralin (8-DPAT) affects melanocyte stem cell survival. MBEH and 8-DPAT were added to melanocytes and melanoma cells to compare cytotoxicity. Stem cell content among viable cells was determined by fluorocytometry using markers CD34, Pax3, and CD271. Immunostaining was used to identify stem cells in skin explants treated with MBEH or 8-DPAT ex vivo. Mice were exposed to MBEH or 8-DPAT and scanned for depigmentation before harvesting skin. MBEH exposure prompted a relative increase in stem cells among cultured melanocytes and melanoma cells, as treatment preferentially eliminated differentiated cells and spared the stem cells. Viability of this remaining, enriched stem cell population was however rapidly reduced by exposure to 8-DPAT within melanocyte and melanoma cell cultures. In human skin explants, the abundance of melanocyte stem cells was also visibly reduced after 8-DPAT treatment, in contrast to tissue exposed to MBEH. Meanwhile, significant depigmentation of the mouse pelage and loss of differentiated melanocytes was observed in vivo in response to topical application of MBEH, but not 8-DPAT. Prolonged application of the latter agent instead appeared to effectively reduce the abundance of melanocyte stem cells in the dermis. This furthers the idea that MBEH and 8-DPAT target complementary cell populations. Results indicate that combination treatment may demonstrate superior therapeutic activity by eliminating both differentiated and tumor initiating populations.

Immune responses in a mouse model of vitiligo with spontaneous epidermal de- and repigmentation

To generate a mouse model of spontaneous epidermal depigmentation, parental h3TA2 mice, expressing both a human-derived, tyrosinase-reactive T-cell receptor on T cells and the matching HLA-A2 transgene, were crossed to keratin 14-promoter driven, stem cell factor transgenic (K14-SCF) mice with intra-epidermal melanocytes. In resulting Vitesse mice, spontaneous skin depigmentation precedes symmetrical and sharply demarcated patches of graying hair. Whereas the SCF transgene alone dictates a greater retinoic acid receptor-related orphan receptor gamma (RORγt)(+) T-cell compartment, these cells displayed markedly increased IL-17 expression within Vitesse mice. Similar to patient skin, regulatory T cells were less abundant compared with K14-SCF mice, with the exception of gradually appearing patches of repigmenting skin. The subtle repigmentation observed likely reflects resilient melanocytes that coexist with skin-infiltrating, melanocyte-reactive T cells. Similar repigmenting lesions were found in a different TCR transgenic model of vitiligo developed on an SCF transgenic background, supporting a role for SCF in repigmentation.

Enhanced bleaching treatment: opportunities for immune-assisted melanocyte suicide in vitiligo

Depigmentation in vitiligo occurs by progressive loss of melanocytes from the basal layer of the skin, and can be psychologically devastating to patients. T cell-mediated autoimmunity explains the progressive nature of this disease. Rather than being confronted with periods of rapid depigmentation and bouts of repigmentation, patients with long-standing, treatment-resistant vitiligo can undergo depigmentation treatment. The objective is to remove residual pigmentation to achieve a cosmetically acceptable result--that of skin with a uniform appearance. In the United States, only the use of mono-benzyl ether of hydroquinone (MBEH) is approved for this purpose. However, satisfactory results can take time to appear, and there is a risk of repigmentation. MBEH induces necrotic melanocyte death followed by a cytotoxic T-cell response to remaining, distant melanocytes. As cytotoxic T-cell responses are instrumental to depigmentation, we propose that combining MBEH with immune adjuvant therapies will accelerate immune-mediated melanocyte destruction to achieve faster, more definitive depigmentation than with MBEH alone. As Toll-like Receptor (TLR) agonists--imiquimod, CpG, and Heat Shock Protein 70 (HSP 70)--all support powerful Th1 responses, we propose that using MBEH in combination with these agents can achieve superior depigmentation results for vitiligo patients.

Mutant HSP70 reverses autoimmune depigmentation in vitiligo

Vitiligo is an autoimmune disease characterized by destruction of melanocytes, leaving 0.5% of the population with progressive depigmentation. Current treatments offer limited efficacy. We report that modified inducible heat shock protein 70 (HSP70i) prevents T cell-mediated depigmentation. HSP70i is the molecular link between stress and the resultant immune response. We previously showed that HSP70i induces an inflammatory dendritic cell (DC) phenotype and is necessary for depigmentation in vitiligo mouse models. Here, we observed a similar DC inflammatory phenotype in vitiligo patients. In a mouse model of depigmentation, DNA vaccination with a melanocyte antigen and the carboxyl terminus of HSP70i was sufficient to drive autoimmunity. Mutational analysis of the HSP70i substrate-binding domain established the peptide QPGVLIQVYEG as invaluable for DC activation, and mutant HSP70i could not induce depigmentation. Moreover, mutant HSP70iQ435A bound human DCs and reduced their activation, as well as induced a shift from inflammatory to tolerogenic DCs in mice. HSP70iQ435A-encoding DNA applied months before spontaneous depigmentation prevented vitiligo in mice expressing a transgenic, melanocyte-reactive T cell receptor. Furthermore, use of HSP70iQ435A therapeutically in a different, rapidly depigmenting model after loss of differentiated melanocytes resulted in 76% recovery of pigmentation. Treatment also prevented relevant T cells from populating mouse skin. In addition, ex vivo treatment of human skin averted the disease-related shift from quiescent to effector T cell phenotype. Thus, HSP70iQ435A DNA delivery may offer potent treatment opportunities for vitiligo.

Preferential secretion of inducible HSP70 by vitiligo melanocytes under stress

Inducible HSP70 (HSP70i) chaperones peptides from stressed cells, protecting them from apoptosis. Upon extracellular release, HSP70i serves an adjuvant function, enhancing immune responses to bound peptides. We questioned whether HSP70i differentially protects control and vitiligo melanocytes from stress and subsequent immune responses. We compared expression of HSP70i in skin samples, evaluated the viability of primary vitiligo and control melanocytes exposed to bleaching phenols, and measured secreted HSP70i. We determined whether HSP70i traffics to melanosomes to contact immunogenic proteins by cell fractionation, western blotting, electron microscopy, and confocal microscopy. Viability of vitiligo and control melanocytes was equally affected under stress. However, vitiligo melanocytes secreted increased amounts of HSP70i in response to MBEH, corroborating with aberrant HSP70i expression in patient skin. Intracellular HSP70i colocalized with melanosomes, and more so in response to MBEH in vitiligo melanocytes. Thus, whereas either agent is cytotoxic to melanocytes, MBEH preferentially induces immune responses to melanocytes.

A quantitative increase in regulatory T cells controls development of vitiligo

T cell cytolytic activity targeting epidermal melanocyte is shown to cause progressive depigmentation and autoimmune vitiligo. Using the recently developed transgenic mice h3TA2 that carry T cell with a HLA-A2 restricted human tyrosinase reactive TCR and develop spontaneous vitiligo from an early age, we addressed the mechanism regulating autoimmune vitiligo. Depigmentation was significantly impaired only in IFN-γ knockout h3TA2 mice but not in TNF-α or perforin knockout h3TA2 mouse strains, confirming a central role for IFN-γ in vitiligo development. Additionally, the regulatory T cells (Treg) were relatively abundant in h3TA2-IFN-γ^−/− mice, and depletion of Treg employing anti-CD25 antibody fully restored the depigmentation phenotype in h3TA2-IFN-γ^−/− mice mediated in part through upregulation of pro-inflammatory cytokines as IL-17and IL-22. Further therapeutic potential of Treg abundance in preventing progressive depigmentation was evaluated by adoptively transferring purified Treg or using rapamycin. Both adoptive transfer of Treg and rapamycin induced lasting remission of vitiligo in mice treated at the onset of disease, or in mice with established disease. This leads us to conclude that reduced regulatory responses are pivotal to the development of vitiligo in disease-prone mice, and that a quantitative increase in the Treg population may be therapeutic for vitiligo patients with active disease.

A central role for inducible heat-shock protein 70 in autoimmune vitiligo

Inducible heat-shock protein 70 (HSP70i) is a protein regulated by stress that protects cells from undergoing apoptosis. Such proteins are marvellously well conserved throughout evolution, which has placed them in the spotlight for helping to understand the intriguing relationship between infection and immunity. In the presence of stress proteins, dendritic cells (DCs) will sense this alarm signal and respond by recruiting immune cells of different plumage to fit the occasion. In times of stress, melanocytes will secrete antigen-bound HSP70i to act as an alarm signal in activating DCs that comes equipped with an address of origin to drive the autoimmune response in vitiligo. Here we pose that if the autoimmune response is funnelled through HSP70i, then blocking the stress protein from activating DCs can lend new treatment opportunities for vitiligo.

Deciphering Treg accumulation in melanoma

e22170

Background: A high density of regulatory T-cells (Tregs) at melanoma tumor sites correlates with poor prognosis due to immunosuppressive effects on the host immune system. While the concentration of circulating Tregs in patients with melanoma is not significantly different from that of healthy controls, Tregs tend to accumulate at tumor sites. We hypothesized that the influx of Tregs observed in melanoma tumors may be explained by enhanced tumor homing. Methods: To quantify the relative expression of chemokine receptors CCL4 and CCL8, and skin homing receptor CLA, blood was drawn from five metastatic melanoma patients and five healthy controls. Lymphocytes were ficolled and negatively sorted for CD3 expression. T-cells were subjected to 7-color FACS staining where Tregs were defined as CD4+CD25+CD127lowFoxP3+ and were simultaneously assessed for expression of CCR4, CCR8, and CLA. To further understand chemokine-receptor signaling involved in Treg homing in melanoma we analyzed the number of CCL22 producing cells in four human metastatic melanoma tissues and four healthy skin tissues obtained during surgery. Dermal CCL22+ cells were detected by indirect immunohistochemistry and quantified to a depth of three times the thickness of the epidermis. Results: Lymphocytes of melanoma patients were found to exhibit enhanced expression of CCR4 (mean of 65.9 versus 51.2%, p<0.01) and CCR8 (3.0 versus 1.5%, p<0.05), but not CLA (21.9 versus 23.9%) as compared with healthy controls. The mean fluorescence intensities of CCR4 and CCR8 were likewise elevated by 63 and 49% over controls (p<0.05 and p<0.01), respectively. A markedly increased number of CCL22 secreting cells were found in tumor samples (mean of 1063.1 versus 207.4, p= 0.02) as compared with healthy controls. Conclusions: These data strongly suggest that enhanced homing of CCR4+ Tregs towards the ligand CCL22 is likely involved in accumulating Tregs at melanoma tumor sites, ultimately impeding effective anti-tumor immune responses. Targeting chemokine-receptor signaling may thus be an effective intervention strategy in melanoma.

Positioning ganglioside D3 as an immunotherapeutic target in lymphangioleiomyomatosis

Tumors that develop in lymphangioleiomyomatosis (LAM) as a consequence of biallelic loss of TSC1 or TSC2 gene function express melanoma differentiation antigens. However, the percentage of LAM cells expressing these melanosomal antigens is limited. Here, we report the overexpression of ganglioside D3 (GD3) in LAM. GD3 is a tumor-associated antigen otherwise found in melanoma and neuroendocrine tumors; normal expression is largely restricted to neuronal cells in the brain. We also observed markedly reduced serum antibody titers to GD3, which may allow for a population of GD3-expressing LAM cells to expand within patients. This is supported by the demonstrated sensitivity of cultured LAM cells to complement mediated cytotoxicity via GD3 antibodies. GD3 can serve as a natural killer T (NKT) cell antigen when presented on CD1d molecules expressed on professional antigen-presenting cells. Although CD1d-expressing monocyte derivatives were present in situ, enhanced NKT-cell recruitment to LAM lung was not observed. Cultured LAM cells retained surface expression of GD3 over several passages and also expressed CD1d, implying that infiltrating NKT cells can be directly cytotoxic toward LAM lung lesions. Immunization with antibodies to GD3 may thus be therapeutic in LAM, and enhancement of existing NKT-cell infiltration may be effective to further improve antitumor responses. Overall, we hereby establish GD3 as a suitable target for immunotherapy of LAM.

Accelerated vitiligo is associated with enhanced IL17 responses in mice (P5166)

Vitiligo is a pigmentary skin disease resulting from T cell mediated cytotoxicity towards melanocytes. To study the involvement of Th17 cells in vitiligo pathogenesis, we generated a spontaneous mouse model of epidermal depigmentation in vitiligo by crossing HLA-A2 transgenic mice expressing a human-derived, tyrosinase reactive T cell receptor transgene within T cells were crossed with a K14-SCF transgenic mouse that retains intra-epidermal melanocytes. In this triple (HLA-A2, h3T, K14-SCF) transgenic mouse, we observed that hair depigmentation was significantly accelerated as compared to the h3TA2 mice parental strain. The presence of the SCF transgene is associated with an increase of IL-17A+T cells among peripheral T cells. Triple transgenic display enhanced tyrosinase-specific Th17 responses and stronger spontaneous CTL responses. The increased Th17 responses are correlated to expansion of SCF responsive MM cell for megakaryocyte and/or bipotent megakaryocyte/erythroid progenitors (CD117+CD151+CD41+CD11c-CD11b-) that induce Th17 cells as previously shown to mediate lupus. In addition, SCF overexpression allows for spotted repigmentation of the epidermis to form ‘NeVi’. Repigmentation is accompanied by reduced Th17 and increased Treg infiltration to the skin. Taken together, accelerated vitiligo is associated with IL-17 responses in mice.

Mutant HSP70i prevents effector T cell responses in autoimmune vitiligo (P4352)

A single amino acid change (Q435A) within HSP70i renders an isoform with treatment potential for vitiligo, as demonstrated by ablated depigmentation in gene gun vaccinated, vitiligo-prone TCR transgenic mice. We hypothesized that HSP70iQ435A inhibits T cell mediated immune responses. We probed skin from gene gun vaccinated P-mel1 and h3TA2 mice for T cell infiltrates and analyzed splenocytes for T cell activation markers by FACS, comparing findings to those in tissues from vitiligo patients and among cells collected from human skin explants exposed to HSP70iQ435A. Decreased skin infiltration was observed for T cells responsible for melanocyte killing in both mouse strains. Eomes/T-bet ratios were significantly decreased by wild-type HSP70i driving an effector phenotype, whereas vaccination with HSP70iQ435A maintains a quiescent phenotype. This ratio was similarly decreased in circulating and skin-infiltrating T cells from vitiligo patients where we also observed an increase in CXCR3 expression, supportive of skin homing. In cells from skin explants exposed to wild-type or mutant HSP70i the Eomes/T-bet ratio is upregulated by HSP70iQ435A whereas upregulation of skin homing receptor CLA followed exposure to wildtype HSP70. In conclusion, the wild-type HSP70i-induced T cell effector phenotype accompanied by elevated CXCR3 and CLA expression observed in vitiligo is countered by HSP70iQ435A exposure, providing a mechanism for HSP70iQ435A induced inhibition of autoimmunity.

A coreceptor-independent transgenic human TCR mediates anti-tumor and anti-self immunity in mice

Recent advancements in T cell immunotherapy suggest that T cells engineered with high-affinity TCR can offer better tumor regression. However, whether a high-affinity TCR alone is sufficient to control tumor growth, or the T cell subset bearing the TCR is also important remains unclear. Using the human tyrosinase epitope-reactive, CD8-independent, high-affinity TCR isolated from MHC class I-restricted CD4(+) T cells obtained from tumor-infiltrating lymphocytes (TIL) of a metastatic melanoma patient, we developed a novel TCR transgenic mouse with a C57BL/6 background. This HLA-A2-restricted TCR was positively selected on both CD4(+) and CD8(+) single-positive cells. However, when the TCR transgenic mouse was developed with a HLA-A2 background, the transgenic TCR was primarily expressed by CD3(+)CD4(-)CD8(-) double-negative T cells. TIL 1383I TCR transgenic CD4(+), CD8(+), and CD4(-)CD8(-) T cells were functional and retained the ability to control tumor growth without the need for vaccination or cytokine support in vivo. Furthermore, the HLA-A2(+)/human tyrosinase TCR double-transgenic mice developed spontaneous hair depigmentation and had visual defects that progressed with age. Our data show that the expression of the high-affinity TIL 1383I TCR alone in CD3(+) T cells is sufficient to control the growth of murine and human melanoma, and the presence or absence of CD4 and CD8 coreceptors had little effect on its functional capacity.

A current viewpoint of lymphangioleiomyomatosis supporting immunotherapeutic treatment options

Lymphangioleiomyomatosis (LAM) leads to hyperproliferation of abnormal smooth muscle cells in the lungs, associated with diffuse pulmonary parenchymal cyst formation and progressive dyspnea on exertion. The disease targets women of child-bearing age. Complications include pneumothoraces and chylous pleural effusions. Ten-year survival is estimated at 70%, and lung transplantation remains the only validated treatment. It has been observed that LAM cells express markers associated with melanocytic differentiation, including gp100 and MART-1. Other melanocytic markers have also been observed. The same proteins are targeted by T cells infiltrating melanoma tumors as well as by T cells infiltrating autoimmune vitiligo skin, and these antigens are regarded as relatively immunogenic. Consequently, vaccines have been developed for melanoma targeting these and other immunogenic melanocyte differentiation proteins. Preliminary data showing susceptibility of LAM cells to melanoma derived T cells suggest that vaccines targeting melanosomal antigens can be successful in treating LAM.

HSP70i is a critical component of the immune response leading to vitiligo

HSP70i and other stress proteins have been used in anti-tumor vaccines. This begs the question whether HSP70i plays a unique role in immune activation. We vaccinated inducible HSP70i (Hsp70-1) knockout mice and wild-type animals with optimized TRP-1, a highly immunogenic melanosomal target molecule. We were unable to induce robust and lasting depigmentation in the Hsp70-1 knockout mice, and in vivo cytolytic assays revealed a lack of cytotoxic T-lymphocyte activity. Absence of T-cell infiltration to the skin and maintenance of hair follicle melanocytes were observed. By contrast, depigmentation proceeded without interruption in mice lacking a tissue-specific constitutive isoform of HSP70 (Hsp70-2) vaccinated with TRP-2. Next, we demonstrated that HSP70i was necessary and sufficient to accelerate depigmentation in vitiligo-prone Pmel-1 mice, accompanied by lasting phenotypic changes in dendritic cell subpopulations. In summary, these studies assign a unique function to HSP70i in vitiligo and identify HSP70i as a targetable entity for treatment.

Notch signaling regulates mouse and human Th17 differentiation

Th17 cells are known to play a critical role in adaptive immune responses to several important extracellular pathogens. Additionally, Th17 cells are implicated in the pathogenesis of several autoimmune and inflammatory disorders as well as in cancer. Therefore, it is essential to understand the mechanisms that regulate Th17 differentiation. Notch signaling is known to be important at several stages of T cell development and differentiation. In this study, we report that Notch1 is activated in both mouse and human in vitro-polarized Th17 cells and that blockade of Notch signaling significantly downregulates the production of Th17-associated cytokines, suggesting an intrinsic requirement for Notch during Th17 differentiation in both species. We also present evidence, using promoter reporter assays, knockdown studies, as well as chromatin immunoprecipitation, that IL-17 and retinoic acid-related orphan receptor γt are direct transcriptional targets of Notch signaling in Th17 cells. Finally, in vivo inhibition of Notch signaling reduced IL-17 production and Th17-mediated disease progression in experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. Thus, this study highlights the importance of Notch signaling in Th17 differentiation and indicates that selective targeted therapy against Notch may be an important tool to treat autoimmune disorders, including multiple sclerosis.

Heme oxygenase-1 expression protects melanocytes from stress-induced cell death: implications for vitiligo

To study protection of melanocytes from stress-induced cell death by heme oxygenases during depigmentation and repigmentation in vitiligo, expression of isoforms 1 and 2 was studied in cultured control and patient melanocytes and normal skin explants exposed to UV or bleaching agent 4-TBP. Similarly, expression of heme oxygenases was followed in skin from vitiligo patients before and after PUVA treatment. Single and double immunostainings were used in combination with light and confocal microscopic analysis and Western blotting. Melanocyte expression of heme oxygenase 1 is upregulated, whereas heme oxygenase 2 is reduced in response to UV and 4-TBP. Upregulation of inducible heme oxygenase 1 was also observed in UV-treated explant cultures, in skin of successfully PUVA-treated patients and in melanocytes cultured from vitiligo non-lesional skin. Heme oxygenase encoding genes were subsequently cloned to study consequences of either gene product on cell viability, demonstrating that HO-1 but not HO-2 overexpression offers protection from stress-induced cell death in MTT assays. HO-1 expression by melanocytes may contribute to beneficial effects of UV treatment for vitiligo patients.

Abstract B14: A phosphorylated β-catenin peptide that is presented by HLA-A2 MHC molecules generates strong phosphospecific T cell responses against melanoma

Dysregulated phosphorylation in cancer cells can lead to the generation of novel tumor antigens modified by phosphorylation, which can be targeted for immunotherapy. Using immobilized metal affinity chromatography and mass spectrometry, we have previously identified phosphorylated peptides presented by MHC molecules on cancer cells. Several of the phosphopeptides are presented by melanoma but not by cultured melanocytes. A significant number of the source proteins for these phosphopeptides are involved in cellular processes known to promote tumor growth and metastasis. These antigens are particularly appealing as immunotherapeutic targets because mutations in or downregulation of the source proteins as a means of immune escape may compromise malignancy. We have also shown that the presence of the phosphate creates new antigenic targets for T cell recognition by creating direct interactions with the T cell receptor leading to specific T cell recognition of the phosphate and peptide sequence. Additionally, the presence of the phosphate can improve HLA-A2 binding affinities of some of the phosphopeptides with suboptimal anchor residues. A phosphopeptide derived from β-catenin was of particular interest as an immunotherapeutic target because its source protein has been shown to cooperate with activated N-Ras in immortalizing melanocytes. β-catenin/LEF signaling can also induce cell growth, motility, and transendothelial migration in melanoma cells. Additionally, nuclear expression of phosphorylated β-catenin has been shown to be associated with poor outcomes in melanoma patients. When pulsed onto bone marrow-derived dendritic cells and used to immunize HLA-A2 transgenic mice, we found that βcatpS3330–39 was only weakly immunogenic. We modified βcatpS3330–39 by replacing a suboptimal Ala at the P10 anchor position with a Val (βcatpS33(V)30–39). This modification enhanced the HLA-A2 binding affinity by 10 fold and substantially enhanced immunogenicity. Intravenous immunization of HLA-A2 transgenic mice with βcatpS33(V)30–39 generated high avidity CD8+ T cells that were highly crossreactive to the natural βcatpS3330–39 phosphopeptide. These high avidity βcatpS33-specific T cells also recognized endogenously processed βcatpS3330–39 on several melanoma cells. However the magnitude of the response to βcatpS33(V)30–39 was considerably less than the response induced using another antigen with a comparable HLA-A2 binding affinity. A 10-fold increase in antigen dose resulted in a sizeable increase in the magnitude of the response and a modest decrease in the average avidity for βcatpS3330–39. The level of crossreactivity on βcatpS3330–39 was not adversely impacted by increasing antigen dose. Our results demonstrate that βcatpS33(V)30–39 is more efficient than βcatpS3330–39 at inducing a βcatpS3330–39–specific immune response. The use of βcatpS33(V)30–39 for peptide vaccination is therefore most likely to be more advantageous for the efficient control of tumors.

Citation Information: Clin Cancer Res 2010;16(7 Suppl):B14