VISTA (PD-1H) Is a Crucial Immune Regulator to Limit Pulmonary Fibrosis

VISTA as a context-dependent immune checkpoint: Implications for tumor immunity and autoimmune pathogenesis

V-domain Ig suppressor of T cell activation (VISTA) is a recently characterized as immune checkpoint regulator with critical roles in modulating immune responses across pathological contexts. In cancer, VISTA contributes to immune evasion by sustaining an immunosuppressive tumor microenvironment, emerging as a promising target for immunotherapeutic intervention. In contrast, in autoimmune diseases, VISTA preserves peripheral immune tolerance and suppresses aberrant immune activation, thereby preventing tissue destruction. This functional dichotomy reflects the complexity of VISTA-mediated signaling, which is modulated by cellular context, microenvironmental cues, and disease stage. Recent studies have elucidated key aspects of VISTA biology, including its structural features, ligand interactions, and context-dependent expression patterns. VISTA operates as a co-inhibitory molecule in cancer, while exerting co-stimulatory or regulatory effects in autoimmunity. This review provides a comprehensive overview of VISTA's discovery, molecular mechanisms, and dual roles in cancer and autoimmune pathogenesis. Furthermore, the current status of VISTA-targeted therapeutic strategies is critically examined, highlighting the translational challenges posed by discrepancies between preclinical models and clinical trial outcomes. Finally, the potential of targeting VISTA within the broader paradigm of immune checkpoint plasticity is discussed, with emphasis on overcoming compensatory immune resistance to enhance therapeutic efficacy. A deeper mechanistic understanding of VISTA is essential for the rational design of future immunomodulatory therapies tailored to specific disease contexts.

Immune inhibitory receptor agonist therapeutics

The immune system maintains the health of an organism through complex sensing and communication mechanisms. Receptors on the surface of immune cells respond to stimuli resulting in activity described at its most basic as inhibitory or stimulatory. Significant progress in therapeutic intervention has occurred by modulating these pathways, yet much remains to be accomplished. Therapeutics that antagonize, or block, immune inhibitory receptor (IIR) pathways, such as checkpoint inhibitors in cancer are a key example. Antagonism of immune stimulatory receptors (ISRs) for dysregulated inflammation and autoimmunity have received significant attention. An alternative strategy is to agonize, or induce signaling, in immune pathways to treat disease. Agonism of ISRs has been employed with some success in disease settings, but agonist therapeutics of IIRs have great, untapped potential. This review discusses and highlights recent advances in pre-clinical and clinical therapeutics designed to agonize IIR pathways to treat diseases. In addition, an understanding of IIR agonists based on activity at a cellular level as either agonist suppression of stimulatory cells (SuSt), or a new concept, agonist suppression of suppressive cells (SuSu) is proposed.

VISTA Deficiency Exacerbates the Development of Pulmonary Fibrosis by Promoting Th17 Differentiation

Background

Interstitial lung disease (ILD), characterized by pulmonary fibrosis (PF), represents the end-stage of various ILDs. The immune system plays an important role in the pathogenesis of PF. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is an immune checkpoint with immune suppressive functions. However, its specific role in the development of PF and the underlying mechanisms remain to be elucidated.

Methods

We assessed the expression of VISTA in CD4 T cells from patients with connective tissue disease-related interstitial lung disease (CTD-ILD). Spleen cells from wild-type (WT) or Vsir -/- mice were isolated and induced for cell differentiation in vitro. Additionally, primary lung fibroblasts were isolated and treated with interleukin-17A (IL-17A). Mice were challenged with bleomycin (BLM) following VISTA blockade or Vsir knockout. Moreover, WT or Vsir -/- CD4 T cells were transferred into Rag1 -/- mice, which were then challenged with BLM.

Results

VISTA expression was decreased in CD4 T cells from patients with CTD-ILD. Vsir deficiency augmented T-helper 17 (Th17) cell differentiation in vitro. Furthermore, IL-17A enhanced the production of inflammatory cytokines, as well as the differentiation and migration of lung fibroblasts. Both VISTA blockade and knockout of Vsir increased the percentage of IL-17A-producing Th17 cells and promoted BLM-induced PF. In addition, mice receiving Vsir -/- CD4 T cells exhibited a higher percentage of Th17 cells and more severe PF compared to those receiving WT CD4 T cells.

Conclusion

These findings demonstrate the significant role of VISTA in modulating the development of PF by controlling Th17 cell differentiation. These insights suggest that targeting VISTA could be a promising therapeutic strategy for PF.

Expression and function of VISTA on myeloid cells

V-domain containing Ig Suppressor of T cell Activation (VISTA) is predominantly expressed on myeloid cells and functions as a ligand/receptor/soluble molecule. In inflammatory responses and immune responses, VISTA regulates multiple functions of myeloid cells, such as chemotaxis, phagocytosis, T cell activation. Since inflammation and immune responses are critical in many diseases, VISTA is a promising therapeutic target. In this review, we will describe the expression and function of VISTA on different myeloid cells, including neutrophils, monocytes, macrophages, dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs). In addition, we will discuss whether the functions of VISTA on these cells impact the disease processing.

Macrophage Implication in IPF: Updates on Immune, Epigenetic, and Metabolic Pathways

Idiopathic pulmonary fibrosis (IPF) is a lethal interstitial lung disease of unknown etiology with a poor prognosis. It is a chronic and progressive disease that has a distinct radiological and pathological pattern from common interstitial pneumonia. The use of immunosuppressive medication was shown to be completely ineffective in clinical trials, resulting in years of neglect of the immune component. However, recent developments in fundamental and translational science demonstrate that immune cells play a significant regulatory role in IPF, and macrophages appear to be among the most crucial. These highly plastic cells generate multiple growth factors and mediators that highly affect the initiation and progression of IPF. In this review, we will provide an update on the role of macrophages in IPF through a systemic discussion of various regulatory mechanisms involving immune receptors, cytokines, metabolism, and epigenetics.

Caveolin-1-Related Intervention for Fibrotic Lung Diseases

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease (ILD) for which there are no effective treatments. Lung transplantation is the only viable option for patients with end-stage PF but is only available to a minority of patients. Lung lesions in ILDs, including IPF, are characterized by alveolar epithelial cell (AEC) senescence and apoptosis and accumulation of activated myofibroblasts and/or fibrotic lung (fL) fibroblasts (fLfs). These composite populations of fLfs show a high rate of basal proliferation, resist apoptosis and senescence, and have increased migration and invasiveness. They also more readily deposit ECM proteins. These features eventuate in progressive destruction of alveolar architecture and loss of lung function in patients with PF. The identification of new, safer, and more effective therapy is therefore mandatory for patients with IPF or related ILDs. We found that increased caveolin-1 and tumor suppressor protein, p53 expression, and apoptosis in AECs occur prior to and then with the proliferation of fLfs in fibrotic lungs. AECs with elevated p53 typically undergo apoptosis. fLfs alternatively demonstrate strikingly low basal levels of caveolin-1 and p53, while mouse double minute 2 homolog (mdm2) levels and mdm2-mediated degradation of p53 protein are markedly increased. The disparities in the expression of p53 in injured AECs and fLfs appear to be due to increased basal expression of caveolin-1 in apoptotic AECs with a relative paucity of caveolin-1 and increased mdm2 in fLfs. Therefore, targeting caveolin-1 using a caveolin 1 scaffolding domain peptide, CSP7, represents a new and promising approach for patients with IPF, perhaps other forms of progressive ILD or even other forms of organ injury characterized by fibrotic repair. The mechanisms of action differ in the injured AECs and in fLfs, in which differential signaling enables the preservation of AEC viability with concurrent limitation of fLf expansion and collagen secretion. The findings in three models of PF indicate that lung scarring can be nearly abrogated by airway delivery of the peptide. Phase 1 clinical trial testing of this approach in healthy volunteers has been successfully completed; Phase 1b in IPF patients is soon to be initiated and, if successful, will be followed by phase 2 testing in short order. Apart from the treatment of IPF, this intervention may be applicable to other forms of tissue injury characterized by fibrotic repair.