Human interleukin-2 (IL-2) stimulates the differentiation and expansion of diverse immune cells dose-dependently. As an immunotherapy agent to treat metastatic cancers, IL-2 has been used in clinical practice and has demonstrated clear antitumor effects; however, its short half-life, the risk of capillary leak syndrome, and the unintended activation of immunosuppressive Treg cells hinder its clinical application. To address these challenges, a novel PEGylated interleukin-2 analogue, SHR-1916, was designed. Its cellular selectivity, efficacy, and improved pharmacokinetic profiles were investigated.
The binding affinities were characterized by surface plasmon resonance (SPR) in vitro. Subsequently, the stimulatory properties were investigated in a murine cell line (CTLL-2), a human cell line (M07e), and human peripheral blood mononuclear cells (PBMCs). To assess the anti-tumor efficacy, a CT-26 colon carcinoma syngeneic model in BALB/c mice and a A375 human melanoma xenograft model using PBMC humanized NCG mice were used in vivo. Moreover, the pharmacokinetic behavior following a single intravenous or subcutaneous dose was evaluated in Sprague-Dawley rats.
SHR-1916 abolished binding to its receptor IL-2Rα, as evidenced by SPR assays, and exerted its activity mainly through binding to IL-2Rβγ, as confirmed by CTLL-2 and M07e cell proliferation assays. In contrast to IL-2, SHR-1916 exhibited a more biased activation of CD8+ T and NK cells compared to Treg cells and stimulated an increase in IFNγ secretion in PBMCs dose-dependently without triggering the release of other potential side effect-associated cytokines. In CT26 colon carcinoma and A375 melanoma models, SHR-1916 significantly reduced the tumor burden. Pharmacokinetic results showed that SHR-1916 had a significantly prolonged half-life in rats.
SHR-1916 exhibited excellent cellular selectivity, anti-tumor efficacies, and improved pharmacokinetics. It has the potential to serve as a novel immunotherapeutic agent designed to enhance IL-2's immune-stimulating activities and promote its tolerability while reducing the immunoregulatory function of Treg cells.
© 2025 Kong et al.

Mucosal antigen-specific T cells are pivotal for pathogen clearance and immune modulation in respiratory infections. Dysregulated T cell responses exacerbate coronavirus disease 2019 severity, marked by cytokine storms and respiratory failure. Despite extensive description in peripheral blood, the characteristics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cells in the lungs remain elusive. Here we conducted integrated single-cell profiling of SARS-CoV-2-specific T cells in 122 bronchoalveolar lavage fluid (BALF) and 280 blood samples from 159 patients, including 27 paired BALF and blood samples from 24 patients. SARS-CoV-2-specific T cells were robustly elicited in BALF irrespective of prior vaccination, correlating with diminished viral loads, lessened systemic inflammation and improved respiratory function. SARS-CoV-2-specific T cells in BALF exhibited profound activation, along with proliferative and multi-cytokine-producing capabilities and a glycolysis-driven metabolic signature, which were distinct from those observed in peripheral blood mononuclear cells. After viral clearance, these specific T cells maintained a polyfunctional tissue-resident memory phenotype, highlighting their critical roles in infection control and long-term protection.
© 2025. The Author(s).

Bacille Calmette-Guérin (BCG) vaccination has off-target effects on disease risk for unrelated infections and immune responses to vaccines. This study aimed to determine the immunomodulatory effects of BCG vaccination on immune responses to vaccines against SARS-CoV-2.
Blood samples, from a subset of 275 SARS-CoV-2-naïve healthcare workers randomised to BCG vaccination (BCG group) or no BCG vaccination (Control group) in the BRACE trial, were collected before and 28 days after the primary course (two doses) of ChAdOx1-S (Oxford-AstraZeneca) or BNT162b2 (Pfizer-BioNTech) vaccination. SARS-CoV-2-specific antibodies were measured using ELISA and multiplex bead array, whole blood cytokine responses to γ-irradiated SARS-CoV-2 (iSARS) stimulation were measured by multiplex bead array, and SARS-CoV-2-specific T-cell responses were measured by activation-induced marker and intracellular cytokine staining assays.
After randomisation (mean 11 months) but prior to COVID-19 vaccination, the BCG group had lower cytokine responses to iSARS stimulation than the Control group. After two doses of ChAdOx1-S, differences in iSARS-induced cytokine responses between the BCG group and Control group were found for three cytokines (CTACK, TRAIL and VEGF). No differences were found between the groups after BNT162b2 vaccination. There were also no differences between the BCG and Control groups in COVID-19 vaccine-induced antigen-specific antibody responses, T-cell activation or T-cell cytokine production.
BCG vaccination induced a broad and persistent reduction in ex vivo cytokine responses to SARS-CoV-2. Following COVID-19 vaccination, this effect was abrogated, and BCG vaccination did not influence adaptive immune responses to COVID-19 vaccine antigens.
© 2025 The Author(s). Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.

Autoantibodies generated in germinal centers (GCs) contribute to the pathogenesis of autoimmune diseases. GCs are controlled by specialized FoxP3+ T-follicular regulatory cells (Tfr), but their role in established autoimmunity is unclear. We generated autoimmune bone marrow chimeras in which Tfr could be specifically ablated by diphtheria toxin. Furthermore, we tracked the clonal persistence and evolution of Tfr populations using Confetti reporters. Ablation of Tfr caused increased early plasma cell output, but longer-term ablation did not increase plasma cell levels beyond those of Tfr-sufficient controls, suggesting that Tfr fail to contain chronic autoreactive GC responses. In agreement, Tfr were robustly induced in early autoreactive GCs but then waned. Moreover, we observed polyclonal Tfr expansion when ablating part of the Tfr subset. Hence, under homeostatic conditions, a polyclonal population of Tfr operates to control autoreactivity by limiting the output of plasma cells from GCs, but in chronic autoimmunity, this mechanism fails.
© 2024 The Author(s).

The vastly spreading COVID-19 pneumonia is caused by SARS-CoV-2. Lymphopenia and cytokine levels are tightly associated with disease severity. However, virus-induced immune dysregulation at cellular and molecular levels remains largely undefined. Here, the leukocytes in the pleural effusion, sputum, and peripheral blood biopsies from severe and mild patients were analyzed at single-cell resolution. Drastic T cell hyperactivation accompanying elevated T cell exhaustion was observed, predominantly in pleural effusion. The mechanistic investigation identified a group of CD14+ monocytes and macrophages highly expressing CD163 and MRC1 in the biopsies from severe patients, suggesting M2 macrophage polarization. These M2-like cells exhibited up-regulated IL10, CCL18, APOE, CSF1 (M-CSF), and CCL2 signaling pathways. Further, cell type specific dysregulation of transposable elements was observed in Severe COVID-19 patients. Together, our results suggest that severe SARS-CoV-2 infection causes immune dysregulation by inducing M2 polarization and subsequent T cell exhaustion. This study improves our understanding of COVID-19 pathogenesis.
© 2024 The Authors. Published by Elsevier Ltd.