Analyzing how Dendritic Cells Interact with Synthetic Virus-Like Particle Vaccines
Drs. Kenneth C. McCullough and Rajni Sharma, Institute of Virology and Immunoprophylaxis; Dr. Arin Ghasparian and Professor John A. Robinson, University of Zürich
Researchers from the Institute of Virology and Immunoprophylaxis and the University of Zürich, both in Switzerland, are using Imaris software to better understand interactions between dendritic cells and nanoparticulate vaccines. The nanoparticulate vaccines under study are based on synthetic virus-like particles and can efficiently induce adaptive immunity without the adjuvant usually required to enhance the recipient’s immune response. Dendritic cells are crucial for initiating and directing immune responses; understanding how synthetic virus-like particles interact with dendritic cells in vitro would provide important information that could be used to develop an efficacious vaccine in vivo.
The researchers are investigating how dendritic cells detect nanoparticulate vaccines, together with the roles played by particular cell receptors and the variety of endocytic processes associated with dendritic cells. In this study, they examined a nanoparticulate vaccine derived from synthetic lipopeptides that self-assemble into synthetic virus-like particles. The lipopeptides carry antigenic determinants that are reactive with B- and T- lymphocytes, and the vaccine can also be constructed to carry pathogen-associated molecular patterns that activate the dendritic cells.
The researchers imaged the interaction of dendritic cells with synthetic virus-like particles using a confocal scanning microscope and then analysed these images using Imaris. The Imaris software permitted a defined analysis and visual description of how dendritic cells endocytosed synthetic virus-like particles. “The Imaris software allowed accuracy of co-localisation through application of the co-localisation module, which gave both mathematical readouts and visual identification of co-localised voxels within the cellular structures,” Dr. McCullough says. “High definition of the visual description obtained for dendritic cell endocytosis of synthetic virus-like particles, and the associated cellular structures, was made possible through the powerful Filament Tracer module and by 3D visualization using Surface and Spots rendering
The image analysis revealed details about the endocytic processes. They observed rapid interaction of the synthetic virus-like particles with the cell surface and slow internalisation involving GM-1 ganglioside-containing lipid rafts, polarizing to the leading edge of the cells. Structures containing the synthetic virus-like particles remained in peripheral intracellular locations for long periods, while slowing interacting with early endosomes and then macropinosomes. “Such characteristics of slow processing and retention in macropinosomes are important for the efficient processing of antigen for presentation to the adaptive immune system and stimulation of efficacious adaptive immune responses, relating to our current knowledge on how dendritic cells operate,” Dr. McCullough says. “This was reflected in the capacity of the synthetic virus-like particles to induce both humoral and cell-mediated immune responses in vivo, in murine and porcine models.”
Research Paper: Sharma R, Ghasparian A, Robinson JA, McCullough KC (2012) Synthetic Virus-Like Particles Target Dendritic Cell Lipid Rafts for Rapid Endocytosis Primarily but Not Exclusively by Macropinocytosis. PLoS ONE 7(8): e43248. doi:10.1371/journal.pone.004324.