Dendritic cell-derived extracellular blebs for cell-based, cell-free vaccination

Introduction & Objectives:

In modulating complex biological responses, cell therapies have been popularly emerged in medicine. However, cell therapeutics render their intrinsic challenges such as engineering and maintaining their viability and functions, stability and storage/distribution, and endured biological activities upon administration. Alternatively, extracellular vesicles (EVs) have been harnessed to overcome such shortcomings. However, EVs are very difficult to produce, quantify, and characterize at a desired quality. this study produced extracellular blebs (EBs) in a very efficient, rapid, and scalable manner and employed them for dendritic cell (DC)-mimicking vaccines against cancer and COVIOD-19.

Method/Description:

DCs were prepared by differentiating the bone marrow cells in the presence of GM-CSF and further matured by incubation with LPS. The resulting mature (m) and immature (i) DCs were further blebbed to prepare iDC-EBs and mDC-EBs. iDC- and mDC-EBs were characterized for size, morphology, surface molecules, and RNA contents for their physical and biological characterizations. They were further loaded with a model antigenic peptide against tumor and their protection of vaccinated mice was investigated. In addition, a DC cell line was transduced to express SARS-CoV-2 spike protein, followed by blebbing before vaccinating mice to produce neutralizing antibodies.

Results:

DC-EBs 1-5 µm in diameter were found to be exclusively made of the membrane of the parent DCs without intracellular organelles but all DC markers and co-stimulatory molecules at the level of the parent cells. sc-RNAseq also confirmed that DC-EBs were much more homogenous than the parent cells and DC-derived EVs. Then vaccinated with mDC-EBs loaded with a tumor antigenic peptide, mice demonstrated efficient protection for the tumor via the activation of cytotoxic T lymphocytes (CTLSs). When mice were vaccinated with DC-EBs expressing the SARS-CoV-2 spike protein, the production of neutralizing antibodies against SARS-CoV-2 was about 700 times more efficient than vaccinating an equivalent amount of the protein alone.

Take Home

Message/Conclusions:

EBs are cell-derived vesicles that closely mimic the functions of the parent cells. They are easy to produce in a rapid, efficient, and scalable manner. EBs can be produced from any kinds of cells and are capable of conducting the broad range of cellular activities. As a proof-of-concept (POC) study, DCs were blebbed with tumor antigenic peptides on the surface or to express and present the spike protein of SARS-CoV-2. Resulting DC-EBs demonstrated efficient vaccination of mice against the tumor or the generation of neutralizing antibodies against the virus. The innovative EBs are highly versatile platform that can be easily employed in cell-free cell therapy, vaccination, and regenerative medicine.