HIV remains a major public health issue in spite of antiretroviral therapy (ART). An innovative vaccine that can induce long-lasting and effective immunity is required to curb the persistently high numbers of new infections worldwide.
A novel DNA vaccine was generated using a Simian-Human Immunodeficiency Virus (SHIV) backbone with a Zambian T/F clade C envelope and under the control of the caprine arthritis encephalitis virus long terminal repeats (LTRs) for constitutive expression. Due to the deleted integrase, this DNA vaccine "CSH-DIN-T/F Z331" performs only a single replication cycle. To increase immunogenicity, the co-expression of apoptotic genes (BAX, BAK, or caspase 8) incorporated at the end of Pol was tested to promote the release of apoptotic bodies taken up by dendritic cells leading to cross-presentation of antigen. The three vaccines (CSH-DIN-T/F Z331-BAX, CSH-DIN-T/F Z331-BAK, and CSH-DIN-T/F Z331-Cas8) were tested in vitro for expression and in vivo in BALB/cJ mice for immunogenicity.
Transduced HEK293 cells co-cultured with CEMx174 confirmed the single replication cycle of the DNA vaccine and the induction of apoptosis by CSH-DIN-T/F Z331-Cas8 based on Annexin V expression. BALB/cJ mice were immunized with a combined intramuscular + intradermal/electroporation approach. Intracellular cytokine staining (ICS) from splenocytes collected 12 weeks post-prime/6 weeks post-boost demonstrated a clear superiority of caspase 8 expressing construct over the others, with higher proportions of IFN-γ-, IL-2-, and IL-21-producing CD8 T cells specific to Env, Gag, and Nef. The kinetics of immune response after various immunization schedules were also investigated.
This novel single-cycle DNA vaccine with apoptotic genes demonstrated an enhanced immunogenicity primarily for antigen-specific CD8+ T-cell responses.
Copyright © 2025 Bose, Rogers, Shirreff, Chebloune and Villinger.

The immune evasion of emerging SARS-CoV-2 variants significantly undermines current vaccination efforts, calling for an updated vaccine composition. To identify optimal booster candidates against circulating JN.1, a panel of variant spikes were characterized. The omicron spikes exhibited reduced plasma membrane expression, accompanied by lower cell-cell fusion but increased viral entry. Regimens with DNA prime-DNA boost or DNA prime-adenoviral vectored vaccine boost by intramuscular immunization elicited neutralizing antibody (NAbs) and T cell responses against all variants except BA.2.86 and JN.1. Intranasal immunization induced high IgA and NAb titers in bronchoalveolar lavage against all variants except BA.2.86 and JN.1. T cell responses were generally comparable for all immunogens tested. JN.1 completely escaped NAbs in one immunized cohort, and breakthrough infections marginally boosted antibody titers. Overall, this study indicates intrinsic difficulty in eliciting NAbs against the JN.1 strain, whereas vaccines based on XBB and EG.5.1 are relatively superior in generating cross-reactive NAbs.
© 2024 The Authors.

Siglec-H is a receptor specifically expressed in mouse plasmacytoid dendritic cells (pDCs), which functions as a negative regulator of interferon-α production and plays a critical role in pDC maturation to become antigen-presenting cells. The function of pDCs in autoimmune and inflammatory diseases has been reported. However, the effect of Siglec-H expression in pDCs in liver inflammation and diseases remains unclear.
Using the model of concanavalin A-induced acute liver injury (ALI), we investigated the Siglec-H/pDCs axis during ALI in BDCA2 transgenic mice and Siglec-H-/- mice. Anti-BDCA2 antibody, anti-interleukin (IL)-21R antibody, and Stat3 inhibitor were used to specifically deplete pDCs, block IL21 receptor, and inhibit Stat3 signaling, respectively. Splenocytes and purified naive CD4 T cells and bone marrow FLT3L-derived pDCs were cocultured and stimulated with phorbol myristate acetate/ionomycin and CD3/CD28 beads, respectively.
Data showed that specific depletion of pDCs aggravated concanavalin A-induced ALI. Remarkably, alanine aminotransferase, hyaluronic acid, and proinflammatory cytokines IL6 and tumor necrosis factor-α levels were lower in the blood and liver of Siglec-H knockout mice. This was associated with attenuation of both interferon-γ/Th1 response and Stat1 signaling in the liver of Siglec-H knockout mice while intrahepatic IL21 and Stat3 signaling pathways were upregulated. Blocking IL21R or Stat3 signaling in Siglec-H knockout mice restored concanavalin A-induced ALI. Finally, we observed that the Siglec-H-null pDCs exhibited immature and immunosuppressive phenotypes (CCR9LowCD40Low), resulting in reduction of CD4 T-cell activation and promotion of IL21+CD4 T cells in the liver.
During T-cell-mediated ALI, Siglec-H-null pDCs enhance immune tolerance and promote IL21+CD4 T cells in the liver. Targeting Siglec-H/pDC axis may provide a novel approach to modulate liver inflammation and disease.
Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

The combination of Programmed Cell Death 1 (PD-1) and Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) blockade has dramatically improved the overall survival rate for malignant melanoma. Immune checkpoint blockers (ICBs) limit the tumor's immune escape yet only for approximately a third of all tumors and, in most cases, for a limited amount of time. Several approaches to overcome resistance to ICBs are being investigated among which the addition of epigenetic drugs that are expected to act on both immune and tumor cells. Guadecitabine, a dinucleotide prodrug of a decitabine linked via phosphodiester bond to a guanosine, showed promising results in the phase-1 clinical trial, NIBIT-M4 (NCT02608437).
We used the syngeneic B16F10 murine melanoma model to study the effects of immune checkpoint blocking antibodies against CTLA-4 and PD-1 in combination, with and without the addition of Guadecitabine. We comprehensively characterized the tumor's and the host's responses under different treatments by flow cytometry, multiplex immunofluorescence and methylation analysis.
In combination with ICBs, Guadecitabine significantly reduced subcutaneous tumor growth as well as metastases formation compared to ICBs and Guadecitabine treatment. In particular, Guadecitabine greatly enhanced the efficacy of combined ICBs by increasing effector memory CD8+ T cells, inducing effector NK cells in the spleen and reducing tumor infiltrating regulatory T cells and myeloid derived suppressor cells (MDSC), in the tumor microenvironment (TME). Guadecitabine in association with ICBs increased serum levels of IFN-γ and IFN-γ-induced chemokines with anti-angiogenic activity. Guadecitabine led to a general DNA-demethylation, in particular of sites of intermediate methylation levels.
These results indicate Guadecitabine as a promising epigenetic drug to be added to ICBs therapy.
© 2023. The Author(s).

Background: The combination of Programmed Cell Death 1 (PD-1) and Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) blockade has dramatically improved the overall survival rate for malignant melanoma. Immune checkpoint blockers (ICBs) limit the tumor’s immune escape yet only for approximately a third of all tumors and, in most cases, for a limited amount of time. Several approaches to overcome resistance to ICBs are being investigated among which the addition of epigenetic drugs that are expected to act on both immune and tumor cells. Guadecitabine, a dinucleotide prodrug of a decitabine linked via phosphodiester bond to a guanosine, showed promising results in the phase-1 clinical trial, NIBIT-M4 (NCT02608437). Methods: We used the syngeneic B16F10 murine melanoma model to study the effects of immune checkpoint blocking antibodies against CTLA-4 and PD-1 in combination, with and without the addition of Guadecitabine. We comprehensively characterized the tumor’s and the host’s responses under different treatments by flow cytometry, multiplex immunofluorescence and methylation analysis. Results: In combination with ICBs, Guadecitabine significantly reduced subcutaneous tumor growth as well as metastases formation compared to ICBs and Guadecitabine treatment. In particular, Guadecitabine greatly enhanced the efficacy of combined ICBs by increasing effector memory CD8+ T cells, inducing effector NK cells in the spleen and reducing tumor infiltrating regulatory T cells and myeloid derived suppressor cells (MDSC), in the tumor microenvironment (TME). Guadecitabine in association with ICBs increased serum levels of IFN-γ and IFN-γ-induced chemokines with anti-angiogenic activity. Guadecitabine led to a general DNA-demethylation, in particular of sites of intermediate methylation levels. Conclusions: These results indicate Guadecitabine as a promising epigenetic drug to be added to ICBs therapy.