β-Thalassemia is a genetic disorder arising from mutations in the β-globin gene, leading to ineffective erythropoiesis and iron overload. Ineffective erythropoiesis, a hallmark of β-thalassemia, is an important driver of iron overload, which contributes to liver fibrosis, diabetes, and cardiac disease. Iron homeostasis is regulated by the hormone hepcidin; BMP6/hemojuvelin-mediated (BMP6/HJV-mediated) signaling induces hepatic hepcidin expression via SMAD1/5, with transmembrane serine protease 6 (TMPRSS6) being a negative regulator of HJV. Individuals with loss-of-function mutations in the TMPRSS6 gene show increased circulating hepcidin and iron-refractory iron-deficiency anemia, suggesting that blocking TMPRSS6 may be a viable strategy to elevate hepcidin levels in β-thalassemia. We generated a human mAb (REGN7999) that inhibits TMPRSS6. In an Hbbth3/+ mouse model of β-thalassemia, REGN7999 treatment led to significant reductions in liver iron, reduced ineffective erythropoiesis, and showed improvements in RBC health, running distance during forced exercise, and bone density. In a phase I, doubleblind, randomized, placebo-controlled study in healthy human volunteers (NCT05481333), REGN7999 increased serum hepcidin and reduced serum iron with an acceptable tolerability profile. Our results suggest that, by both reducing iron and improving RBC function, inhibition of TMPRSS6 by REGN7999 may offer a therapy for iron overload and impaired erythropoiesis in β-thalassemia.

Immune memory is influenced by the frequency and type of antigenic challenges. Here, we performed a cross-sectional comparison of immune parameters following a BA.1 breakthrough infection in individuals with prior hybrid immunity (conferred by infection and vaccination) versus those solely vaccinated in a cohort of health care workers in Lyon, France. The results showed higher levels of serum anti-receptor binding domain (RBD) antibodies and neutralizing antibodies against BA.1 post-infection in the vaccine-only group. Individuals in this group also showed a decrease in memory B cells against the ancestral strain but an increase in those specific and cross-reactive to BA.1, suggesting a more limited immune imprinting. Conversely, hybrid immunity prevents the decrease in antibody dependent cellular cytotoxicity (ADCC) response, possibly by limiting IgG4 class-switching and enhanced anti-N responses post-infection. This highlights that BA.1 breakthrough infection induces different immune responses depending on prior history of vaccination and infection, which should be considered for further vaccination guidelines.
© 2025 The Authors.

ABSTRACT Short-lived, clade-specific immune responses with limited mucosal priming are limitations faced by current COVID-19 mRNA vaccines against sarbecoviruses. We have developed a nasal booster vaccine candidate that induced robust and sustained, cross-clade, systemic and mucosal protective immunity. Two recombinant Clec9A-specific monoclonal antibodies fused to the Receptor Binding Domain (RBD) from Omicron XBB.1.5 and SARS-CoV-1, respectively were generated. In Comirnaty mRNA-vaccinated mice, boosting with each individual Clec9A-RBD construct induced immune responses that either were limited in breadth or waned over time; while boosting with both constructs combined (Clec9A OMNI ) elicited robust cross-clade neutralizing antibodies (nAb) and T cell responses that were significantly more sustained compared to Bivalent Comirnaty (BC) mRNA vaccine booster. The persistence of RBD-specific follicular helper CD4 + T cells, germinal centre B cells, and long-lived plasma cells that facilitated affinity maturation in Clec9A OMNI -boosted mice, correlated with the detection of triple cross-reactive B cells that bind to ancestral SARS-CoV-2 ancestral, SARS-CoV-2 XBB.1.5 and SARS-CoV-1 RBD. Remarkably, intranasal boosting with Clec9A OMNI generated robust and sustained mucosal immune responses in the upper and lower respiratory compartments, including RBD-specific IgA, cross-clade nAb and cellular immunity together with functional tissue-resident memory T cells, without compromising the systemic immune responses. Correspondingly, Clec9A OMNI booster conferred superior protection against Omicron BA.1 compared to BC booster when challenge was performed at six months post-boost. Hence, Clec9A OMNI is a promising nasal booster vaccine candidate that has the potential to mitigate pandemic threats from emerging sarbecoviruses. One Sentence Summary Nasal booster immunization with dendritic cell-targeting vaccine candidate in mRNA-vaccinated mice induced cross-clade, sustained, systemic and mucosal protective immunity.

Chimeric antigen receptor (CAR)-induced suppression of the transcription factor B cell CLL/lymphoma 11B (BCL11B) propagates CAR-induced killer (CARiK) cell development from lymphoid progenitors. Here, we show that CRISPR-Cas9-mediated Bcl11b knockout in human and murine early lymphoid progenitors distinctively modulates this process either alone or in combination with a CAR. Upon adoptive transfer into hematopoietic stem cell recipients, Bcl11b-edited progenitors mediated innate-like antigen-independent anti-leukemic immune responses. With CAR expression allowing for additional antigen-specific responses, the progeny of double-edited lymphoid progenitors acquired prolonged anti-leukemic activity in vivo. These findings give important insights into how Bcl11b targeting can be used to tailor anti-leukemia functionality of CAR-engineered lymphoid progenitor cells.
Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.

Outbreaks of respiratory virus infections and arbovirus infections both pose a substantial threat to global public health. Clinically, both types of infection range from mild to severe and coinfections may occur more commonly than supposed. Our previous experimental coinfection study in mice demonstrated that prior infection with the arbovirus Semliki Forest virus (SFV) negatively impacted immune responses to influenza A virus (IAV). Here, we investigate whether simultaneous coinfection impacts the outcome of immune responses or disease. Simultaneous SFV and IAV infection did not lead to exacerbated or attenuated disease compared with the single virus infection control groups. SFV brain virus titers and brain pathology, including inflammation and immune responses, were comparable in the coinfection and single infection groups. By contrast, there was enhanced IAV replication, but no exacerbated lung pathology in coinfected mice. The magnitude of IAV-specific CD8+ T-cell responses in the lungs was lower compared with IAV-only infection. Considered along with our previous study, this study provides evidence that the timing of viral coinfection is pivotal in determining effects on immune responses, pathological changes and disease outcome.
© 2025 The Author(s). Immunology & Cell Biology published by John Wiley & Sons Australia, Ltd on behalf of the Australian and New Zealand Society for Immunology, Inc.