Patrice N. Marche

1. Influenza remains a major global health burden, causing approximately 500,000 deaths annually and substantial socioeconomic costs worldwide, particularly among older adults, pregnant women and y...

Influenza vaccines targeting hemagglutinin require annual updates due to viral variability, limiting protection against pandemic strains. The conserved matrix protein 2 ectodomain (M2e) peptide offers cross‐strain immunity but suffers from low immunogenicity. Here, M2e peptides are conjugated onto nanostructured lipid carriers (NLCs) using bioorthogonal click chemistry, preserving key epitopes and enhancing antigen presentation. Immunization in mice demonstrates that NLC‐M2e induces focused and robust anti‐M2e antibody responses, which are significantly amplified by incorporating a pan‐DR epitope helper T cell epitope, achieving antibody levels compatible with protection. The formulation elicits balanced IgG subclasses and T‐helper 1 cell‐type cellular responses, supporting effective immune mechanisms. These findings suggest that NLC‐based delivery of M2e peptides, especially with helper epitopes, represents a promising universal influenza vaccine strategy warranting further preclinical and clinical investigation.

Influenza vaccines are considered the most effective measure for preventing influenza. The key antigen of commercial vaccines is hemagglutinin (HA), the main protein on the surface of influenza viruses. This protein is genetically variable, necessitating the annual redefinition of the vaccine formulation. Furthermore, these vaccines do not offer protection against pandemic viral strains. The M2e peptide, a small surface protein conserved among influenza type A strains, could enable cross-immunity when used as an antigen. Nevertheless, its limited immunogenicity has restricted its application in universal influenza vaccines. To enhance the immune responses to M2e, we associated it with Nanostructured Lipid Carriers (NLCs). These NLCs are stable over time and their small diameter (<100 nm) enhances interactions with antigen-presenting cells and improve lymphatic drainage, facilitating their uptake by the immune system. The M2e specific antibody response in mice was enhanced by using 'click' chemistry to conjugate the M2e peptide to the NLC surface. Also, the incorporation of PADRE-specific CD4+ T cells stimulating peptide between M2e peptide and its linking region greatly enhanced the specific antibody response to M2e and generated immune response levels that could be compatible with influenza protection. This promising M2e formulation vectorized by NLC represents a potential universal influenza vaccine candidate warranting further preclinical investigations and clinical evaluation.

Background: Hepatitis B is a liver infection caused by HBV. Infected individuals who fail to control the viral infection develop chronic hepatitis B and are at risk of developing life-threatening liver diseases, such as cirrhosis or liver cancer. Dendritic cells (DCs) play important roles in the immune response against HBV but are functionally impaired in patients with chronic hepatitis B. The underlying mechanisms involved in HBV-induced DC dysfunctions remain to be elucidated. Methods: We explored DC modulations by HBV and HBsAg by exposing blood-derived cDC1s, cDC2s, and plasmacytoid DCs from healthy donors to HBV or HBsAg and stimulating them with toll-like receptor ligand. Their phenotypic and functional features, as well as their metabolic profile, were analyzed through multiparametric flow cytometry and multiplex assays and further explored on patients’ samples. Results: We found that HBV deeply reshaped the DC secretome in response to toll-like receptor ligand. Strikingly, we observed that HBV-exposed DCs secrete high levels of CX3CL1 (fractalkine), a chemokine responsible for attracting antiviral effectors to the site of infection. HBsAg exposure favored DC activation while drastically altering TRAIL expression in response to toll-like receptor ligand and increasing the secretion of cytokines/chemokines involved in immune tolerance. HBsAg further dampened the metabolism of DC subsets while driving metabolic switches. Notably, the relevance of the CX3CL1/CX3CR1 axis, TGF-β, and metabolic disturbances was demonstrated within intrahepatic DC subsets in patients according to disease stage. Conclusions: Our work brings new insights into the immunomodulation induced by HBV on DCs, which contribute to impaired antiviral responses and progression toward chronicity.

The delivery of mRNA-based cancer vaccines has demonstrated significant promise in triggering antitumor immune responses. With the aim of using them in combination with other immunotherapies already used in the clinical appropriately, the modifications of the intratumoral immune microenvironment needs to be deeply characterized. We have shown that the second generation of lipid nanoparticles (LNPs), nanostructured lipid carriers (so-called Lipidots ^® ), are able to vector protein antigens and nucleic acids. Here, we test Lipidots ^® for the delivery of mRNA encoding OVA antigen and eliciting a specific antitumor immune response. We demonstrate in vitro that our LNPs deliver mRNA into dendritic cells (DCs), when complexed with mRNA, activate DCs through the TLR4/8 and ROS signaling pathways and induce specific CD4 ⁺ and CD8 ⁺ T cell activation. Our vaccinal strategy exhibits significant antitumor efficacy both in the context of tumor prevention and as a therapeutic vaccine in B16OVA and E.G7-OVA cold tumors. The LNP-Ova mRNA vaccine induces a profound intratumoral remodeling of the innate and adaptive immunity associated with an increase in the gene expression of chemokines ( Cxcl10, Cxcl11, Cxcl9 ) involved in CD8 ⁺ T cell attraction. Additionally, the vaccine induces the establishment of an escape mechanism mediated by PD-1/PDL-1 axis, making it an adjuvant therapy for optimized responses to the blocking of this signaling pathway. Finally, the combination of vaccine and anti-PD-1 therapy achieves a much higher rate of complete responses and memory immune responses compared to monotherapies. Our work demonstrates the capability of Lipidots ^® as an effective platform for the development of preventive and therapeutic vaccines against cancer based on mRNA delivery and that combination with other immunotherapies such as immune checkpoint blockers could counter tumor resistance and promote long-term antitumor immunity.

In hepatitis B virus (HBV) infection, the interplay between the virus and the host immune system is crucial in determining the pathogenesis of the disease. Patients who fail to mount a sufficient and sustained anti-viral immune response develop chronic hepatitis B (CHB). T cells and natural killer (NK) cells play decisive role in viral clearance, but they are defective in chronic HBV infection. The activation of immune cells is tightly controlled by a combination of activating and inhibitory receptors, called immune checkpoints (ICs), allowing the maintenance of immune homeostasis. Chronic exposure to viral antigens and the subsequent dysregulation of ICs actively contribute to the exhaustion of effector cells and viral persistence. The present review aims to summarize the function of various ICs and their expression in T lymphocytes and NK cells in the course of HBV infection as well as the use of immunotherapeutic strategies targeting ICs in chronic HBV infection.

The magnetically localized and wash-free fluorescence immunoassay (MLFIA) is a no-wash assay for directly measuring biomolecule (antigen and antibody) concentration, without mixing nor washing steps, from a body fluid (serum and plasma).