Exacerbation of Autoimmune Thyroiditis by CTLA-4 Blockade: A Role for IFNγ-Induced Indoleamine 2, 3-Dioxygenase

Research progress in the construction of animal models of autoimmune thyroiditis

Autoimmune thyroiditis (AIT), also known as Hashimoto's thyroiditis (HT), is an autoimmune disease that is characterised by elevated thyroid-specific antibody titres. The incidence of AIT is increasing year over year, making it urgent to establish a suitable animal model for this condition, in order to better explore its pathogenesis and potential pharmaceutical mechanisms for treatment. Owing to a lack of basic research on this disease, problems such as disparate modelling methods with unclear and varying success rates make it difficult for researchers to obtain effective information on AIT in the short term. This report summarises and analyzes the current literature on AIT and combines actual operability to explain the selection and specific implementation processes behind the uses of different modelling approaches, to provide a better overall understanding of autoimmune thyroid diseases.

Current understanding of CTLA-4: from mechanism to autoimmune diseases

Autoimmune diseases (ADs) are characterized by the production of autoreactive lymphocytes, immune responses to self-antigens, and inflammation in related tissues and organs. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is majorly expressed in activated T cells and works as a critical regulator in the inflammatory response. In this review, we first describe the structure, expression, and how the signaling pathways of CTLA-4 participate in reducing effector T-cell activity and enhancing the immunomodulatory ability of regulatory T (Treg) cells to reduce immune response, maintain immune homeostasis, and maintain autoimmune silence. We then focused on the correlation between CTLA-4 and different ADs and how this molecule regulates the immune activity of the diseases and inhibits the onset, progression, and pathology of various ADs. Finally, we summarized the current progress of CTLA-4 as a therapeutic target for various ADs.

Clonally expanded, thyrotoxic effector CD8+ T cells driven by IL-21 contribute to checkpoint inhibitor thyroiditis

Autoimmune toxicity occurs in up to 60% of patients treated with immune checkpoint inhibitor (ICI) therapy for cancer and represents an increasing clinical challenge for expanding the use of these treatments. To date, human immunopathogenic studies of immune-related adverse events (IRAEs) have relied on sampling of circulating peripheral blood cells rather than affected tissues. Here, we directly obtained thyroid specimens from individuals with ICI-thyroiditis, one of the most common IRAEs, and compared immune infiltrates with those from individuals with spontaneous autoimmune Hashimoto's thyroiditis (HT) or no thyroid disease. Single-cell RNA sequencing revealed a dominant, clonally expanded population of thyroid-infiltrating cytotoxic CXCR6+ CD8+ T cells (effector CD8+ T cells) present in ICI-thyroiditis but not HT or healthy controls. Furthermore, we identified a crucial role for interleukin-21 (IL-21), a cytokine secreted by intrathyroidal T follicular (TFH) and T peripheral helper (TPH) cells, as a driver of these thyrotoxic effector CD8+ T cells. In the presence of IL-21, human CD8+ T cells acquired the activated effector phenotype with up-regulation of the cytotoxic molecules interferon-γ (IFN-γ) and granzyme B, increased expression of the chemokine receptor CXCR6, and thyrotoxic capacity. We validated these findings in vivo using a mouse model of IRAEs and further demonstrated that genetic deletion of IL-21 signaling protected ICI-treated mice from thyroid immune infiltration. Together, these studies reveal mechanisms and candidate therapeutic targets for individuals who develop IRAEs.

Inhibition of IL-17A Protects against Thyroid Immune-Related Adverse Events while Preserving Checkpoint Inhibitor Antitumor Efficacy

Immune checkpoint inhibitor (ICI) immunotherapy leverages the body's own immune system to attack cancer cells but leads to unwanted autoimmune side effects in up to 60% of patients. Such immune-related adverse events (IrAEs) may lead to treatment interruption, permanent organ dysfunction, hospitalization, and premature death. Thyroiditis is one of the most common IrAEs, but the cause of thyroid IrAEs remains unknown. In this study, we use a new, physiologically relevant mouse model of ICI-associated autoimmunity to identify a key role for type 3 immune cells in the development of thyroid IrAEs. Multiple lineages of IL-17A-producing T cells expand in thyroid tissue with ICI treatment. Intrathyroidal IL-17A-producing innate-like γδT17 cells were increased in tumor-free mice, whereas adaptive Th17 cells were also prominent in tumor-bearing mice, following ICI treatment. Furthermore, Ab-based inhibition of IL-17A, a clinically available therapy, significantly reduced thyroid IrAE development in ICI-treated mice with and without tumor challenge. Finally, combination of IL-17A neutralization with ICI treatment in multiple tumor models did not reduce ICI antitumor efficacy. These studies suggest that targeting Th17 and γδT17 cell function via the IL-17A axis may reduce IrAEs without impairing ICI antitumor efficacy and may be a generalizable strategy to address type 3 immune-mediated IrAEs.

Distinct Cytokine Signatures in Thyroiditis Induced by PD-1 or CTLA-4 Blockade: Insights from a New Mouse Model

Background: The pathogenesis of thyroiditis caused by immune-checkpoint inhibitors (ICIs) such as antiprogrammed death receptor-1 (PD-1) and anticytotoxic T lymphocyte antigen-4 (CTLA-4) is incompletely understood. To gain mechanistic insights, we developed a mouse model of ICI-related thyroiditis and assessed the clinical, hormonal, and cytokine profiles. Methods: Forty NOD-H2h4 mice, 112 days old at the start of the experiments, were divided into two sequential cohorts. In the first one (No. = 21), mice were injected with both anti-PD-1 and anti-CTLA-4 checkpoint inhibitors while drinking either regular water or iodine-supplemented water. In the second cohort (No. = 19), mice were injected with either anti-PD-1 or anti-CTLA-4 while drinking iodine-supplemented water. Mice were sacrificed two months after the initial injection to collect thyroid gland for histopathology (to assess thyroiditis severity) and flow cytometry (to identify immune cell subsets and tissue-resident memory T cell markers). Mice were also studied before sacrifice to determine thyroid area and structure (by ultrasound), thyroid function (serum total thyroxine, thyrotropin, thyroid antibodies), and cytokine profile (by bead-based Luminex technology). Results: Thyroiditis was more severe upon PD-1 than CTLA-4 blockade (p = 0.01) and significantly correlated with the number of CD45+ cells infiltrating the thyroid (cumulative odds ratio [OR] 1.2 [95% confidence interval, CI 1.1-1.3], p < 0.001, that is 20% greater odds of a higher severity score for every 170-unit increase in CD45 infiltrating cells). Thyroiditis was instead more prevalent (100% vs. 63%, p < 0.01) in the anti-CTLA-4 mice, which also showed a larger thyroid area (17 ± 8.2 mm) than those treated with anti-PD-1 (11 ± 4.2 mm) and controls (p < 0.01). Serum IL-6 was markedly increased upon PD-1 blockade (40 pg/mL at baseline, 198 pg/mL on day 172), an increase not seen in the anti-CTLA-4 group (p = 0.01). IL-6 mirrored thyroiditis severity, with highest serum values found in greatest histopathology scores (cumulative OR 1.1 [CI 1.02-1.15], p = 0.009). GM-CSF and MIP1β increased more in the anti-CTLA-4 group (p < 0.001 for both), whereas the other cytokines did not differ among the treatment groups. Conclusions: The study reports a mouse model of thyroiditis induced by PD-1 blockade and, comparing it to the anti-CTLA-4 model, uncovers distinctive histopathological, sonographic, hormonal, and immunological features, offering biomarkers, such as serum IL-6, that could be used in the clinical setting.

Hypothalamic-Pituitary Autoimmunity in Patients Treated with Anti-PD-1 and Anti-PD-L1 Antibodies

Simple Summary

The aim of this study is to search for APA and AHA and related pituitary dysfunction in patients treated with immunotherapy. APA and AHA could represent markers for early detection of patients at risk of developing pituitary deficiencies related to immune checkpoint inhibitors and undergoing closer follow-up. Furthermore, this study aims to evaluate the correlation between the presence of AHA and APA and the clinical response to checkpoint inhibitor therapy. However, further prospective studies will be needed to confirm our results.

Abstract

Background: Autoimmune hypophysitis is a frequent immune-related adverse event (irAE) in cancer patients treated with immunecheckpoint inhibitors. Studies seeking anti-pituitary (APA) and anti-hypothalamus (AHA) antibodies in patients treated with anti-PD-1 and anti-PD-L1 are scarce. The aim of this study is to search for APA and AHA and related pituitary dysfunction in patients treated with these agents. Methods:Cross-sectional and preliminary longitudinal studies were conducted at the Medical Oncology Unit and Endocrinology and Metabolic Diseases Unit of the University of Campania “Luigi Vanvitelli”. Fifty-four cancer patients on treatments with anti-PD-1 or anti-PD-L1 (Group 1) and 50 healthy controls were enrolled for a cross-sectional study; 13 cancer patients (Group 2) were enrolled for our preliminary longitudinal study. APA/AHA titers and changes in biochemical and hormonal profile were evaluated in Group 1; in Group 2, they were evaluated before and after nine weeks from the start of immunotherapy. Results: Patients of Group 1 showed a higher prevalence of APA and AHA than controls: 21 of them had APA, 16 had AHA, and 11 had both autoantibodies. In total, 7 of 13 patients in Group 2 became APA-positive and 3 became AHA-positive after nine weeks of immunotherapy, showing an increase in prolactin and a decrease in ACTH and IGF-1 levels compared with basal values. Conclusions:Anti-pituitary and anti-hypothalamus antibodies seem to play a pivotal role in hypothalamic–pituitary autoimmunity and secondary endocrine-related alterations evoked by anti-PD-1 and PD-L1 antibodies.

Yanghe Decoction Suppresses the Experimental Autoimmune Thyroiditis in Rats by Improving NLRP3 Inflammasome and Immune Dysregulation

Inflammation is an important contributor to autoimmune thyroiditis. Yanghe decoction (YH) is a traditional Chinese herbal formulation which has various anti-inflammatory effects. It has been used for the treatment of autoimmune diseases such as ankylosing spondylitis In this study we aimed to investigate the effects of YH on autoimmune thyroiditis in a rat model and elucidate the underlying mechanisms. The experimental autoimmune thyroiditis (EAT) model was established by thyroglobulin (pTG) injections and excessive iodine intake. Thyroid lesions were observed using hematoxylin and eosin (H and E) staining and serum TgAb, TPOAb, TSH, T3, and T4 levels were measured by enzyme-linked immunosorbent assay IL-35 levels were evaluated using real-time polymerase chain reaction (RT-PCR) and Th17/Treg balance in peripheral blood mononuclear cells (PBMCs) was determined by flow cytometry and RT-PCR. Changes in Wnt/β-catenin signaling were evaluated using Western blot. Immunofluorescence staining and western blot were employed to examine NLRP3 inflammasome activation in the thyroid. YH minimized thyroid follicle injury and decreased concentrations of serum TgAb, TPOAb, TSH, T3, and T4 in EAT model. The mRNA of IL-35 was increased after YH treatment. YH also increased the percentage of Treg cells, and decreased Th17 proportion as well as Th17/Treg ratio in PBMCs. Meanwhile, the mRNA levels of Th17 related cytokines (RORγt, IL-17A, IL-21, and IL-22) were suppressed and Treg related cytokines (FoxP3, TGF-β, and IL-10) were promoted in PBMCs. Additionally, the protein expressions of Wnt-1 and β-catenin were unregulated after YH treatment. NLRP3 immunostaining signal and protein levels of IL-17, p-NF-κB, NLRP3, ASC, cleaved-Caspase-1, cleaved-IL-1β, and IL-18 were downregulated in the thyroid after YH intervention. Overall, the present study demonstrated that YH alleviated autoimmune thyroiditis in rats by improving NLRP3 inflammasome and immune dysregulation.

The Efficacy and Safety of Immune Checkpoint Inhibitors in Patients With Cancer and Preexisting Autoimmune Disease

Immune checkpoint inhibitor (ICI) is a revolutionary breakthrough in the field of cancer treatment. Because of dysregulated activation of the immune system, patients with autoimmune disease (AID) are usually excluded from ICI clinical trials. Due to a large number of cancer patients with preexisting AID, the safety and efficacy of ICIs in these patients deserve more attention. This review summarizes and analyzes the data regarding ICI therapy in cancer patients with preexisting AID from 17 published studies. Available data suggests that the efficacy of ICIs in AID patients is comparable to that in the general population, and the incidence of immune-related adverse events (irAEs) is higher but still manageable. It is recommended to administer ICIs with close monitoring of irAEs in patients with a possibly high benefit-risk ratio after a multidisciplinary discussion based on the patient's AID category and severity, the patient's tumor type and prognosis, alternative treatment options, and the patient's intention. Besides, the prevention and management of irAEs in AID patients have been discussed.

Peri-tumor administration of controlled release anti-CTLA-4 synergizes with systemic anti-PD-1 to induce systemic antitumor immunity while sparing autoimmune toxicity

Combination immunotherapy targeting the PD-1 and CTLA-4 checkpoint inhibitor pathways provides substantial clinical benefit in patients with advanced-stage cancer but at the risk of dose-limiting inflammatory and autoimmune toxicity. The delicate balance that exists between unleashing tumor killing and promoting systemic autoimmune toxicity represents a major clinical challenge. We hypothesized that targeting anti-CTLA-4 so that it perfuses tumor-draining lymph nodes would provide a significant therapeutic advantage and developed an injectable hydrogel with controlled antibody release characteristics for this purpose. Injection of hydrogel-encapsulated anti-CTLA-4 at a peri-tumor location (MC-38 tumor model) produced dose-dependent antitumor responses and survival that exceeded those by anti-CTLA-4 alone (p < 0.05). Responses to 100 µg of targeted anti-CTLA-4 also equaled or exceeded those observed with a series of systemic injections delivering 600 µg (p < 0.05). While preserving antitumor activity, this approach resulted in serum anti-CTLA-4 exposure (area under the curve) that averaged only 1/16th of that measured with systemic therapy. Consistent with the marked differences in systemic exposure, systemic anti-CTLA-4 stimulated the onset of autoimmune thyroiditis in iodide-exposed NOD.H-2h4 mice, as measured by anti-thyroglobulin antibody titer, while hydrogel-encapsulated anti-CTLA-4 had a minimal effect (p ≤ 0.01). At the same time, this targeted low-dose anti-CTLA-4 approach synergized well with systemic anti-PD-1 to control tumor growth and resulted in a high frequency of complete responders that were immune to tumor re-challenge at a distant site. We conclude that targeted and controlled delivery of low-dose anti-CTLA-4 has the potential to improve the benefit-risk ratio associated with combination checkpoint inhibitor therapy.

Endocrine Toxicity of Cancer Immunotherapy Targeting Immune Checkpoints

Immune checkpoints are small molecules expressed by immune cells that play critical roles in maintaining immune homeostasis. Targeting the immune checkpoints cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD-1) with inhibitory antibodies has demonstrated effective and durable antitumor activity in subgroups of patients with cancer. The US Food and Drug Administration has approved several immune checkpoint inhibitors (ICPis) for the treatment of a broad spectrum of malignancies. Endocrinopathies have emerged as one of the most common immune-related adverse events (irAEs) of ICPi therapy. Hypophysitis, thyroid dysfunction, insulin-deficient diabetes mellitus, and primary adrenal insufficiency have been reported as irAEs due to ICPi therapy. Hypophysitis is particularly associated with anti-CTLA-4 therapy, whereas thyroid dysfunction is particularly associated with anti-PD-1 therapy. Diabetes mellitus and primary adrenal insufficiency are rare endocrine toxicities associated with ICPi therapy but can be life-threatening if not promptly recognized and treated. Notably, combination anti-CTLA-4 and anti-PD-1 therapy is associated with the highest incidence of ICPi-related endocrinopathies. The precise mechanisms underlying these endocrine irAEs remain to be elucidated. Most ICPi-related endocrinopathies occur within 12 weeks after the initiation of ICPi therapy, but several have been reported to develop several months to years after ICPi initiation. Some ICPi-related endocrinopathies may resolve spontaneously, but others, such as central adrenal insufficiency and primary hypothyroidism, appear to be persistent in most cases. The mainstay of management of ICPi-related endocrinopathies is hormone replacement and symptom control. Further studies are needed to determine (i) whether high-dose corticosteroids in the treatment of ICPi-related endocrinopathies preserves endocrine function (especially in hypophysitis), and (ii) whether the development of ICPi-related endocrinopathies correlates with tumor response to ICPi therapy.

To reflect human autoimmune thyroiditis, thyroid peroxidase (not thyroglobulin) antibodies should be measured in female (not sex-independent) NOD.H2h4 mice

NOD.H2^h4 mice are the most commonly used model for human autoimmune thyroiditis. Because thyroid autoimmunity develops slowly (over months), NOD.H2^h4 mice are usually exposed to excess dietary iodide to accelerate and amplify the process. However, unlike the female bias in human thyroid autoimmunity, autoantibodies to thyroglobulin (TgAb) are reported to be similar in male and female NOD.H2^h4 . We sought evidence for sexual dimorphism in other parameters in this strain maintained on regular or iodized water. Without iodide, TgAb levels are higher in males than in females, the reverse of human disease. In humans, autoantibodies to thyroid peroxidase (TPOAb) are a better marker of disease than TgAb. In NOD.H2^h4 mice TPOAb develop more slowly than TgAb, being detectable at 6 months of age versus 4 months for the latter. Remarkably, unlike TgAb, TPOAb levels are higher in female than male NOD.H2^h4 mice on both regular and iodized water. As previously observed, serum T4 levels are similar in both sexes. However, thyroid-stimulating hormone (TSH) levels are significantly higher in males than females with or without iodide exposure. TSH levels correlate with TgAb levels in male NOD.H2^h4 mice, suggesting a possible role for TSH in TgAb development. However, there is no correlation between TSH and TPOAb levels, the latter more important than TgAb in human disease. In conclusion, if the goal of an animal model is to closely reflect human disease, TPOAb rather than TgAb should be measured in older female NOD.H2^h4 mice, an approach requiring patience and the use of mouse TPO protein.

Therapeutic strategies for organ-confined and non-organ-confined bladder cancer after radical cystectomy

INTRODUCTION

In patients with muscle invasive or Bacillus Calmette-Guérin refractory urothelial carcinoma of the urinary bladder (UCUB) radical cystectomy represents the standard of care. However, a proportion of patients experience disease progression, local recurrence and/or metastatic disease. Areas covered: This review provides an overview of available therapeutic strategies after radical cystectomy and examines ongoing clinical trials including cytotoxic chemotherapy and immunotherapy. Expert commentary: Cytotoxic chemotherapy offers limited benefit in UCUB patients. However, the recent introduction of immunotherapy provides new hope for durable responses or possibly complete cures.

Immunomodulatory Factors Galectin-9 and Interferon-Gamma Synergize to Induce Expression of Rate-Limiting Enzymes of the Kynurenine Pathway in the Mouse Hippocampus

Elevated levels of circulating pro-inflammatory cytokines are associated with symptomology of several psychiatric disorders, notably major depressive disorder. Symptomology has been linked to inflammation/cytokine-dependent induction of the Kynurenine Pathway. Galectins, like pro-inflammatory cytokines, play a role in neuroinflammation and the pathogenesis of several neurological disorders but without a clearly defined mechanism of action. Their involvement in the Kynurenine Pathway has not been investigated. Thus, we searched for a link between galectins and the Kynurenine Pathway using in vivo and ex vivo models. Mice were administered LPS and pI:C to determine if galectins (Gal's) were upregulated in the brain following in vivo inflammatory challenges. We then used organotypic hippocampal slice cultures (OHSCs) to determine if Gal's, alone or with inflammatory mediators [interferon-gamma (IFNγ), tumor necrosis factor-alpha (TNFα), interleukin-1beta (IL-1β), polyinosine-polycytidylic acid (pI:C), and dexamethasone (Dex; synthetic glucocorticoid)], would increase expression of indoleamine/tryptophan-2,3-dioxygenases (DO's: Ido1, Ido2, and Tdo2; Kynurenine Pathway rate-limiting enzymes). In vivo, hippocampal expression of cytokines (IL-1β, TNFα, and IFNγ), Gal-3, and Gal-9 along with Ido1 and Ido2 were increased by LPS and pI:C (bacterial and viral mimetics). Of the cytokines induced in vivo, only IFNγ increased expression of two Ido1 transcripts (Ido1-FL and Ido1-v1) by OHSCs. Although ineffective alone, Gal-9 accentuated IFNγ-induced expression of only Ido1-FL. Similarly, IFNγ induced expression of several Ido2 transcripts (Ido2-v1, Ido2-v3, Ido2-v4, Ido2-v5, and Ido2-v6). Gal-9 accentuated IFNγ-induced expression of only Ido2-v1. Surprisingly, Gal-9 alone, slightly but significantly, induced expression of Tdo2 (Tdo2-v1 and Tdo2-v2, but not Tdo2-FL). These effects were specific to Gal-9 as Gal-1 and Gal-3 did not alter DO expression. These results are the first to show that brain Gal-9 is increased during LPS- and pI:C-induced neuroinflammation. Increased expression of Gal-9 may be critical for neuroinflammation-dependent induction of DO expression, either acting alone (Tdo2-v1 and Tdo2-v2) or to enhance IFNγ activity (Ido1-FL and Ido2-v1). Although these novel actions of Gal-9 are described for hippocampus, they have the potential to operate as DO-dependent immunomodulatory processes outside the brain. With the expanding implications of Kynurenine Pathway activation across multiple immune and psychiatric disorders, this synergy provides a new target for therapeutic development.