Visualizing the Internalization of Marburg Viruslike Particles into Living Cells.

Viral entry into cells is a pivotal stage of the infection process and, therefore, a prime target for the development of antiviral therapeutics. Here, we describe a system to monitor the internalization of lipophilic dye-labeled Marburg viruslike particles (VLPs) into living cells. Using cells stably expressing fluorescent protein-fused markers for specific cell organelles, the VLP entry process can be visualized. This procedure enables the characterization of the entry process by visualizing individual steps using specific bio-probes. Additionally, when combined with image analysis, this method allows for the quantification of the efficiencies of individual entry steps including particle adsorption, uptake by endocytosis, and membrane fusion. Finally, this method can be used for antiviral drug screening.