A COS-1 cell (RIGHT) generating murine lukemia virus (MLV) labeled with Gag-YFP (red) and expressing dynamin2-CFP (green) in contact with XC target cell (LEFT) expressing mCAT1-CFP (green). MLV is transferred from infected dynamin-expressing Cos cells (green, to the right) to receptor expressing uninfected target cells (green, to the left). Four stages of retroviral transmission can be identified: First, the establishment of contact between the infected and uninfected cell. Second, contact-induced virus assembly at the sites of cell-cell contact. Third, transmission of virus via filopodial bridges. Fourth, downregulation of the cell-cell contact. Repeated rounds of establishment of contact, contact-induced virus assembly, and virus transmission are observed. Images were collected with a volocity spinning disc confocal microscope equipped with an environmental chamber (LIVE CELL; Pathology Devices) and a Nikon Perfect Focus using a 60X 1.4NA objective. A z-stack of red and green images was taken every 134 s and merged into a single file to generate the Video. The image resolution is 0.166619 um/pixel. Celldance 2008, 3rd Place Video: Sequential Waves of Retroviral Transmission from Cell to Cell