Bacillus Calmette-Guérin (BCG) is an attenuated vaccine widely used for tuberculosis prevention. While BCG has long been perceived as an intracellular candidate vector for delivering antigens against infectious diseases and cancers, challenges persist in inducing durable immune responses, particularly high-titer neutralizing antibodies (Nabs). Here we show that displaying antigens in the surface of BCG is a promising strategy to induce long-lasting Nabs production and T-cell responses. We constructed a recombinant BCG expressing the SARS-CoV-2 receptor-binding domain (RBD) antigen on its cell wall, termed CW-rBCG::RBD, which achieved an antigen yield approaching 850 nanograms per 107 colony-forming unit. Compared with both the parental BCG and the RBD protein subunit vaccine (RBDAS01), intravenous administration of CW-rBCG::RBD followed by a booster dose significantly enhanced Nab production and increased the frequencies of RBD-specific central memory T cells (Tcm) and T follicular helper (Tfh) cells in the spleen. In mice primed with a single dose of CW-rBCG::RBD and boosted with RBDAS01, we also observed elevated Nab titers and detectable levels of RBD-specific IgG2a antibodies at 8 weeks post-priming, responses that were not observed in the BCG-primed or RBDAS01-only groups. Furthermore, subcutaneous co-administration of CW-rBCG::RBD and RBDAS01 sustained Nab production for up to 31 weeks and maintained higher Tfh and Tcm cell frequencies compared to both BCG co-administration with RBDAS01 and RBDAS01 alone. These findings highlight an effective strategy for optimizing BCG-based vaccination and immunotherapy platforms. Subject terms: recombinant BCG; immune response; vaccines; cell wall; SARS-CoV-2 RBD.
© 2025. The Author(s).

The transgenic 116C-NOD mouse strain exhibits a prevalent Th17 phenotype, and reduced type 1 diabetes (T1D) compared to non-obese diabetic (NOD) mice. A cohousing experiment between both models revealed lower T1D incidence in NOD mice cohoused with 116C-NOD, associated with gut microbiota changes, reduced intestinal permeability, shifts in T and B cell subsets, and a transition from Th1 to Th17 responses. Distinct gut bacterial signatures were linked to T1D in each group. Using a RAG-2-/- genetic background, we found that T cell alterations promoted segmented filamentous bacteria proliferation in young NOD and 116C-NOD, as well as in immunodeficient NOD.RAG-2-/- and 116C-NOD.RAG-2-/- mice across all ages. Bifidobacterium colonization depended on lymphocytes and thrived in a non-diabetogenic environment. Additionally, 116C-NOD B cells in 116C-NOD.RAG-2-/- mice enriched the gut microbiota in Adlercreutzia and reduced intestinal permeability. Collectively, these results indicate reciprocal modulation between gut microbiota and the immune system in rodent T1D models.
© 2023. The Author(s).

The hepatitis B virus core antigen (HBcAg) tolerates insertion of foreign epitopes and maintains its ability to self-assemble into virus-like particles (VLPs). We constructed a ∆HBcAg-based VLP vaccine expressing three predicted severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B and T cell epitopes and determined its immunogenicity and protective efficacy. The recombinant ∆HBcAg-SARS-CoV-2 protein was expressed in Escherichia coli, purified, and shown to form VLPs. K18-hACE2 transgenic C57BL/6 mice were immunized intramuscularly with ∆HBcAg VLP control (n = 15) or ∆HBcAg-SARS-CoV-2 VLP vaccine (n = 15). One week after the 2nd booster and before virus challenge, five ∆HBcAg-SARS-CoV-2 vaccinated mice were euthanized to evaluate epitope-specific immune responses. There is a statistically significant increase in epitope-specific Immunoglobulin G (IgG) response, and statistically higher interleukin 6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) expression levels in ∆HBcAg-SARS-CoV-2 VLP-vaccinated mice compared to ∆HBcAg VLP controls. While not statistically significant, the ∆HBcAg-SARS-CoV-2 VLP mice had numerically more memory CD8+ T-cells, and 3/5 mice also had numerically higher levels of interferon gamma (IFN-γ) and tumor necrosis factor (TNF). After challenge with SARS-CoV-2, ∆HBcAg-SARS-CoV-2 immunized mice had numerically lower viral RNA loads in the lung, and slightly higher survival, but the differences are not statistically significant. These results indicate that the ∆HBcAg-SARS-CoV-2 VLP vaccine elicits epitope-specific humoral and cell-mediated immune responses but they were insufficient against SARS-CoV-2 infection.
© 2023 Wiley Periodicals LLC.

Specific antigen recognition by T cell receptor (TCR) activates TCR signaling pathway, leading to T cell proliferation and differentiation into effector and memory cells. Herein, we describe protocols for TCR stimulation assays, including procedures for the isolation and enrichment of mouse splenic T cells for ex vivo TCR stimulation with anti-CD3/CD28 antibodies, and the use of ovalbumin-OT-II mouse model for in vivo TCR stimulation. We applied this protocol to show that MYC protein is essential for T cell proliferation and differentiation. For complete details on the use and execution of this protocol, please refer to Nozais et al. (2021).
© 2021 The Author(s).

In the thymus, T cell progenitors differentiate in order to generate naive T lymphocytes which migrate in the periphery where they will fulfill their function in the adaptive immune response. During thymopoiesis, genomic alterations in thymocytes can promote leukemia development. Among recurrent alteration is PTEN inactivation, which is associated to MYC overexpression. Herein, we used conditional Pten and Myc knockout mouse models and single-cell RNA-sequencing approach, to investigate the impact of MYC loss on physio-pathological development of PTEN-proficient or PTEN-deficient T lymphocytes. First, our results confirm that MYC is mandatory for PTEN loss-mediated leukemogenesis, while it is not required for terminal steps of thymopoiesis. In contrast, we uncovered that Myc ablation in CD4+CD8+ thymocytes disrupts T lymphocytes homeostasis in the spleen, notably by drastically reducing the number of MYC-deficient effector/memory T cells. Collectively, our data show that besides naive T cells proliferation, MYC is essential for effector/memory differentiation.
© 2021 The Authors.