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Abstract: γδ T cells represent key players in immune surveillance after T-cell receptor α/β (αβ)/CD19-depleted HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Although encouraging data are available on the impact of Vδ2-targeting therapy in improving HSCT clinical outcomes, their role in providing antimicrobial immunity is largely unexplored. This study aimed to investigate the antiviral protective profile of Vδ2 T cells in pediatric patients given haplo-HSCT. The characterization of γδ T cells was performed in pediatric recipients (n = 26) in the donor graft and at 30, 60, and 120 days after haplo-HSCT. The antiviral activity of Vδ2 T cells and the cytomegalovirus (CMV)-specific αβ T-cell immunity was analyzed. Early after HSCT, Vδ2 T cells was significantly higher in patients who did not experience viral reactivation (No-VR) than in patients with CMV reactivation. Interestingly, this difference was already present in the grafts. Clustering analysis identified a protective subset of Vδ2 T cells in patients with No-VR, expressing CD16, NKG2D, and CD107a, and producing Th1 cytokines. This subset directly correlated with interleukin-15 and inversely with the CMV DNA level. Stimulated Vδ2 T cells inhibit CMV replication, acquired CD86/HLA-DR molecules, induced HLA-DR on monocytes, and improved the αβ CMV-specific T-cell response. Altogether, these results identify an antiviral protective profile displayed by Vδ2 T cells early after HSCT, and define their ability to inhibit CMV replication, to induce antigen-presenting cell maturation and to improve αβ virus-specific T-cell response, opening a new application of Vδ2-targeting immunotherapy after HSCT, adding the antiviral to the antitumor potential., (© 2025 American Society of Hematology. Published by Elsevier Inc. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Ex-vivo depletion of donor CD45RA+ naïve T-cells can reduce graft-versus-host-disease (GVHD) in haploidentical hematopoietic stem cell transplantation (HSCT) while providing memory T-cells to reduce infections. CD62L is another marker of naïve T-cells. Depletion of CD62L+ cells may offer advantages of removing central memory T-cells which may also cause mild GVHD, and retain CD45RA+ effector memory T-cells (TEMRA). We aimed to evaluate the depletion efficiency, safety and immunoreconstitution after novel CD62L depleted donor lymphocyte infusion (DLI) with T-cell receptor (TCR)-αβ depleted haploidentical HSCT. Children with malignant or non-malignant diseases who underwent the first TCRαβ depleted haploidentical HSCT were recruited to receive CD62L depleted DLI on day 0 at a dose of 1 × 10 6 /kg or 5 × 10 6 /kg CD3+CD62L- cells using the CliniMACS device. Six children aged 0.3-15 years received 4.6-10 × 10 6 /kg CD34+ cells. CD62L depletion resulted in undetectable CD3+CD62L+ cells in 4 patients and 3.39-3.52 log reduction in 2 patients. Infusion was well-tolerated. All patients had neutrophil and platelet engrafted early (medians 10 and 9.5 days respectively) with 100 % donor chimerism. Only one patient had grade 1 acute GVHD. None had chronic GVHD. Post-transplant recovery of CD3+ cells reached a median of 117/uL at 1 month and as high as 352/uL at 3 months. TEMRA cells were present at 1 month (median 2 cells/uL) and increased 3 months post-transplant (median 21 cells/uL). In conclusion, CD62L depletion is highly efficient and appears safe and does not affect engraftment. It provides TEMRA and effector memory T-cells to protect the recipient against infections. Risk of GVHD is low., (Copyright © 2025. Published by Elsevier B.V.)

Objectives: Deauville scores (DS) from PET/CT imaging are increasingly being used to direct response-adjusted treatment strategies in lymphoma, including large B cell lymphomas (LBCL). We aimed to investigate the outcome of allogeneic haematopoietic stem cell transplantation (alloHSCT) in LBCL and the role played by pre-transplant disease status, as determined by DS., Methods: We performed a retrospective, observational study of adults treated with a T-cell depleted alloHSCT for de novo DLBCL or high-grade transformation., Results: Sixty-four patients received an alloHSCT. Forty-four had acute GvHD (38 had Grade 1-2). Overall non-relapse mortality (NRM) at 1 year was 20.31%. Patients ≥ 55 years had a higher cumulative incidence of NRM (66.67%) than those who were < 55 years (25.08%) (p = 0.00660). A 4-year relapse risk was 22.5%. Fourteen patients had disease relapse. The 4-year overall survival (OS) was 49.80%; median OS was 3.7 years (1.4-7.1). Patients with a pre-alloHSCT DS of 1-2 had a higher OS than a DS of 3-5 (61.97% vs. 34.23%; p = 0.0167); this was confirmed on multivariate analysis. Younger patients (< 55 years) had a higher OS than those ≥ 55 years (60.91% vs. 18.75%; p = 0.0246)., Conclusions: The pre-transplant Deauville score was predictive of the clinical outcome and patients with an absence of metabolically active disease pre-transplant had superior outcomes., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

In acetylcholine receptor (AChR)-seropositive myasthenia gravis (MG), anti-AChR autoantibodies impair neuromuscular transmission and cause severe muscle weakness. MG therapies broadly suppress immune function, risking infections. We designed a chimeric autoantibody receptor (CAAR) expressing the 210-amino acid extracellular domain of the AChR α subunit (A210) linked to CD137-CD3ζ cytoplasmic domains to direct T cell cytotoxicity against anti-AChRα B cells. A210-CAART incorporating a CD8α transmembrane domain (TMD8α) showed functional but unstable surface expression, partially restored by inhibiting lysosomal degradation. A210-CAART with a CD28 TMD showed sustained surface expression, independent of TMD dimerization motifs. In a mouse xenograft model, A210.TMD8α-CAART demonstrated early control of anti-AChR B cell outgrowth but subsequent rebound and loss of surface CAAR expression, whereas A210.TMD28-CAART induced sustained surface CAAR expression and target cell elimination. This study demonstrates the importance of the CD28 TMD for CAAR stability and in vivo function, laying the groundwork for future development of precision cellular immunotherapy for AChR-MG.

HIV infection remains incurable as the virus persists within a latent reservoir of CD4 + T cells. Novel approaches to enhance immune responses against HIV are essential for effective control and potential cure of the infection. In this study, we designed a novel tetravalent bispecific antibody (Bi-Ab32/16) to simultaneously target the gp120 viral protein on infected cells, and the CD16a receptor on NK cells. In vitro, Bi-Ab32/16 triggered a potent, specific, and polyfunctional NK-dependent response against HIV-infected cells. Moreover, addition of the Bi-Ab32/16 significantly reduced the latent HIV reservoir after viral reactivation and mediated the clearance of cells harboring intact proviruses in samples from people with HIV (PWH). However, the in vivo preclinical evaluation of Bi-Ab32/16 in humanized mice expressing IL-15 (NSG-Hu-IL-15) revealed a significant decline of NK cells associated with poor virological control after ART interruption. Our study underscores the need to carefully evaluating strategies for sustained NK cell stimulation during ART withdrawal., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Immunotherapy targeting CD4 + FoxP3 + regulatory T cells (Tregs) through CD4 + lymphocyte depletion is being investigated as cancer treatment. This study examines the efficacy and limitations of CD4 depletion across various cancer models. We examined CD4 depletion in syngeneic mouse tumor models including B16 melanoma, Renca kidney cancer, and Hepa1-6 hepatocellular carcinoma. The study explored the relationship between MHC II expression and tumor growth, immune response, and survival. In mouse models, CD4 depletion suppressed B16 and Renca tumor growth but accelerated Hepa1-6 tumors. Hepa1-6 had high MHC II expression while the other two lines had low MHC II expression. Manipulation of MHC II expression in Hepa1-6 and Renca cell lines confirmed the mechanistic importance of MHC II in generating a CD4-based antitumor immune response. Analysis of the TCGA dataset supports the relevance of this mechanism in patients. In tumors with high MHC II and low MHC I expression, increased CD4 levels correlated with improved survival. CD4 depletion can suppress tumor growth or promote tumor growth, depending on tumor MHC expression status. MHC status may identify tumors where intratumor CD4 may be a better early-response marker than CD8., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

To interrogate the role of specific immune cells in infection, cancer, and autoimmunity, immunologists commonly use monoclonal depletion antibodies (depletion-mAbs) or genetically engineered mouse models (GEMMs). To generate a tool that combines specific advantages and avoids select drawbacks of the two methods, we engineered adeno-associated viral vectors expressing depletion mAbs (depletion-AAVs). Single-dose depletion-AAV administration durably eliminated lymphocyte subsets in mice and avoided accessory deficiencies of GEMMs, such as marginal zone defects in B cell-deficient animals. Depletion-AAVs can be used in animals of different genetic backgrounds, and multiple depletion-AAVs can readily be combined. Exploiting depletion-AAV technology, we showed that B cells were required for unimpaired CD4 + and CD8 + T cell responses to chronic lymphocytic choriomeningitis virus (LCMV) infection. Upon B cell depletion, CD8 + T cells failed to suppress viremia, and they only helped resolve chronic infection when antibodies dampened viral loads. Our study positions depletion-AAVs as a versatile tool for immunological research., Competing Interests: Declaration of interests D.D.P. is a founder, consultant, and shareholder of Hookipa Pharma Inc. commercializing arenavirus-based vector technology, and he as well as W.V.B. and D.M. are listed as inventors on corresponding patents., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: With recent advances in clinical practice, including the use of reduced-toxicity conditioning regimens and innovative approaches such as ex vivo TCRαβ/CD19 depletion of haploidentical donor stem cells or post-transplant cyclophosphamide (PTCY), hematopoietic stem cell transplantation (HSCT) has emerged as a curative treatment option for a growing population of patients with inborn errors of immunity (IEI). However, despite these promising developments, graft failure (GF) remains a significant concern associated with HSCT in these patients. Although a second HSCT is the only established salvage therapy for patients who experience GF, there are no uniform, standardized strategies for performing these second transplants. Furthermore, even less data is available regarding the outcomes and best practices for a third HSCT as a salvage measure when a second HSCT fails to achieve engraftment., Case Presentation: A 6-year-old boy with leukocyte adhesion deficiency type I (LAD-I) experienced GF after the first and second HSCT from a matched unrelated donor. As a salvage measure, the patient received a dual in vivo T-cell depleted haploidentical HSCT. The conditioning regimen for this third HSCT included anti-thymocyte globulin (ATG) and PTCY. Complete donor chimerism was assessed using the short tandem repeat (STR) PCR technique. By day +28 after the transplant, the expression of the leukocyte adhesion molecules CD18, CD11b, and CD11c on the patient's peripheral blood neutrophils had recovered to over 99%. It remained stable throughout the 18-month follow-up period., Conclusion: T-cell replete haploidentical HSCT with ATG and PTCY may be a viable salvage option for LAD patients who have rejected prior HSCT., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2025 Kiumarsi, Alaei, Nikbakht, Mohammadi, Ostad-Ali, Rasti and Rostami.)

Kidney transplantation is the treatment of choice for end-stage organ failure. To improve transplantation outcomes, particularly of "marginal" organs from extended criteria donors (ECD), attempts have been made to therapeutically modulate donor or graft pre-transplantation. Anti-thymocyte globulin (ATG) has a history as lymphocyte-depleting, immunosuppressive drug for treating rejection episodes post transplantation. In this study, however, we aimed to comprehensively analyze the effects of ATG donor pre-conditioning in a mouse model of kidney transplantation. ATG pre-treatment of potential donors led to a broad depletion of T- and NK cells in peripheral blood, non-lymphoid (including kidney) and lymphoid organs within 48 h, whereas myeloid cells were spared. ATG was also effectively depleting renal innate lymphoid type 1 and 2 cells. Importantly, transplantation of kidneys from ATG pre-treated donors into fully mismatched recipients showed only mild effects on leukocyte re-composition post transplantation. In line with this, serum creatinine and urea levels were similar in animals receiving kidneys from ATG treated donors or controls, demonstrating that donor treatment had no effect on allograft function in the early post-transplantation phase. In summary, our findings are suggestive of a more cell-type-specific depletion strategy in concert with an experimental model better reflecting aspects of clinical transplantation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2025 He, Yang, Kotsch and Sattler.)

Background: The neoantigen vaccine has remarkable potential in treating advanced cancer due to its tumor specificity and ability to bypass central tolerance mechanisms. However, numerous neoantigens show poor immunogenicity, and the immune inhibitory factors of present in both tumors and tumor-draining lymph nodes impair the efficacy of cancer neoantigen vaccine. Eliminating immunosuppressive cells will improve the priming and expansion of anti-tumor immune cells induced by the vaccine., Methods: In this study, a Treg-depleting regimen (consisting of CD25mAb and low-dose cyclophosphamide (LD-CTX)) was used in conjunction with a neoantigen vaccine for treating mice with solid tumors. We constructed two types of tumor models and investigated differences in therapy efficacy in the four groups (PBS, vaccine, CD25mAb+CTX and combination) at the genetic and protein levels. ELISPOT and TCR sequencing were applied to detect the expansion of neoantigen reactive T cells (NRT) and tumor antigen spreading., Results: In the combinational group, the ELISPOT results showed an obvious expansion of NRT cells induced by weak immunogenic peptides. The combinational group exhibited significant improvement in inhibiting the tumor growth extended the survival time of tumor-bearing mice, and promoted T cells infiltration into tumors. Besides, compared to the Vac group, more neoantigen-targeted and TAA-targeted T cells were detected in the combinational group by TCR sequencing. The results of transcriptomic sequencing and flow cytometry showed that the number of Tregs in the combinational group was lower, while the proportions of memory effector T cells and effector T cells were higher than those in the vaccine group. An increase in mature DCs was also observed in vaccinated mice after receiving this Treg-depleting strategy., Conclusion: Our research first revealed that inhibiting the normal function of Tregs transformed "weaker" neoantigens into "stronger" ones, while also contributing to the proliferation of NRT cells. This Treg-depleting strategy allowed neoantigens with poor immunogenicity to elicit a robust immune response, thereby augmenting the efficacy of the neoantigen vaccine in delaying tumor growth and prolonging the survival of the hosts., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

B-cell depleting therapy (BCDT) has revolutionised the treatment of B-cell malignancies and autoimmune diseases by targeting specific B-cell surface antigens, receptors, ligands, and signalling pathways. This narrative review explores the mechanisms, applications, and complications of BCDT, focusing on the therapeutic advancements since the introduction of rituximab in 1997. Various monoclonal antibodies and kinase inhibitors are examined for their roles in depleting B cells through antibody-dependent and independent mechanisms. The off-target effects, such as hypogammaglobulinemia, infections, and cytokine release syndrome, are discussed, emphasising the need for immunologists to identify and help manage these complications. The increasing prevalence of BCDT has necessitated the involvement of clinical immunologists in addressing treatment-associated immunological abnormalities, including persistent hypogammaglobulinemia and neutropenia. We highlight the importance of considering underlying inborn errors of immunity (IEI) in patients presenting with these complications. Furthermore, we discuss the impact of BCDT on other immune cell populations and the challenges in predicting and managing long-term immunological sequelae. The potential for novel BCDT agents targeting the BAFF/APRIL-TACI/BCMA axis and B-cell receptor signalling pathways to treat autoimmune disorders is also explored, underscoring the rapidly evolving landscape of B-cell targeted therapies., Competing Interests: Declarations. Funding: SS is supported in part by the National Institute for Health and Care Research (NIHR) Leeds Biomedical Research Centre (BRC) (NIHR203331). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. Conflict of interest: Not applicable. Ethics approval: Not applicable. Patient consent to participate/publish: Not applicable. Availability of data and material: Not applicable. Code availability: Not applicable. Author contributions: MK, AA, and SS contributed to the conceptualisation of the publication. MK conducted the literature review and drafted the initial manuscript. AA and SS reviewed the initial and subsequent drafts, offering critical revisions. All authors—MK, AA, and SS—collaboratively wrote, reviewed, and approved the final manuscript., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The increasing use of immune suppressive monoclonal antibodies in the treatment of organ transplant recipients and patients with oncologic, neurological, and autoimmune diseases can lead to serious morbidity and mortality from the reactivation of viral agents that persist in humans. The squirrel monkey polyomaviruses are naturally found in Bolivian squirrel monkeys (SQM) and may be a useful model for the study of polyomavirus-associated pathogenesis and experimental treatment and prevention strategies. Two diverse groups of squirrel monkeys were given, a single dose of an anti-B cell antibody (rituximab) resulting in complete depletion of B cells (CD20+), while an anti-CD8 monoclonal antibody (7 pt-3F9) resulted in a transient depletion of CD8+ lymphocytes compared with control animals (group with no infusion with either of the monoclonal antibodies). The animals remained clinically healthy, with no pathological symptoms suggesting that the intensity and/or duration of immune suppression were inadequate to trigger pathogenic reactivation of the latent polyoma and herpes viruses. We observed a transient reduction in circulating plasma cytokines, IL-2, IFN-γ, and IL-12 reduced JC and BK viral protein-specific proliferative responses in both the CD8 and CD20 depletion groups. This study clearly elucidates the consequences of the use of depletion monoclonal antibodies in immune suppression modalities in the treatment of human malignancies and during transplantation, and SQM acts as a good model in the selection of dosage at which activation of latent viruses is at a minimum, with no pathological consequences.