Fc-empowered exosomes with superior epithelial layer transmission and lung distribution ability for pulmonary vaccination.

Mucosal vaccines offer potential benefits over parenteral vaccines for they can trigger both systemic immune protection and immune responses at the predominant sites of pathogen infection. However, the defense function of mucosal barrier remains a challenge for vaccines to overcome. Here, we show that surface modification of exosomes with the fragment crystallizable (Fc) part from IgG can deliver the receptor-binding domain (RBD) of SARS-CoV-2 to cross mucosal epithelial layer and permeate into peripheral lung through neonatal Fc receptor (FcRn) mediated transcytosis. The exosomes F-L-R-Exo are generated by genetically engineered dendritic cells, in which a fusion protein Fc-Lamp2b-RBD is expressed and anchored on the membrane. After intratracheally administration, F-L-R-Exo is able to induce a high level of RBD-specific IgG and IgA antibodies in the animals' lungs. Furthermore, potent Th1 immune-biased T cell responses were also observed in both systemic and mucosal immune responses. F-L-R-Exo can protect the mice from SARS-CoV-2 pseudovirus infection after a challenge. These findings hold great promise for the development of a novel respiratory mucosal vaccine approach.

Polymyxin B-Modified Fosfomycin Liposomes Target Gram-Negative Bacteria and Exert Synergistic Antibacterial Effect.

Bacterial infection has always been one of the most serious threats faced by humans. Bacterial targeting is a promising strategy to enhance treatment efficacy and reduce the emergence of drug resistance. However, the traditional antibiotic targeting efficiency is poor, and it is challenging to achieve therapeutic concentrations of both drugs simultaneously in the same tissue due to differences in drug metabolism. This study aims to construct bacteria-targeted liposomes to enhance antibiotic delivery. In this study, anionic liposomes were constructed using the thin-film dispersion method, and the cationic antimicrobial peptide polymyxin B (PMB) was adsorbed onto the liposome surface through anionic-cationic electrostatic interaction as a carrier for fosfomycin (FOS), enabling bacteria-targeted drug delivery. The targeted effect of polymyxin B liposomes (PMB-Lipo) on Acinetobacter baumannii was evaluated in vitro and in vivo. The bactericidal activity of polymyxin B adsorbed fosfomycin liposomes (PMB-FOS-Lipo) in vitro and in vivo was compared with PMB and FOS mixture solution (PMB-FOS-Solution), and the anti-infection and anti-inflammatory effects were assessed. We also explored the issue of PMB nephrotoxicity using a series of biochemical indicators in mice. In vitro and in vivo experiments showed that PMB-Lipo effectively targeted Acinetobacter baumannii. PMB-FOS-Lipo exhibited better therapeutic efficacy compared to free PMB and FOS. Finally, adsorbing polymyxin B onto the liposome surface significantly reduced its severe nephrotoxicity. PMB-Lipo can effectively target Acinetobacter baumannii, and the encapsulated fosfomycin in liposomes synergizes with polymyxin B, enhancing antibacterial efficacy and reducing adverse drug reactions. We believe this antibacterial strategy can provide new insights into bacteria-targeted treatment.