Filter set 00

Expression of eGFP was visualized using an Axiovert 25 IF microscope (Zeiss, Sliedrecht, the Netherlands) followed by quantitative analysis using FACS. For iRFP, infected cells were visualized using a LSM-700 confocal microscope with filter set 32 (Zeiss) and quantitative analysis was done by FACS using the APC-Cy7 channel. Expression of fRFP was visualized using fluorescent microscopy with filter set 00 (Zeiss) and by FACS using the PerCP-Cy5-5-A channel.
The reporter activity of the gLUC virus was determined using a Gaussia luciferase flash assay kit (Pierce, Etten-Leur, the Netherlands) according to the manufacturer’s instructions. The Luciferase assay system (Promega, Leiden, the Netherlands) was used for fLUC, according to the manufacturer’s instructions. Luminescence was measured on an Infinite F200 reader (Tecan, Giessen, the Netherlands) in flat 96-black well plates (Corning, Amsterdam, the Netherlands).

Samples were imaged using an upright microscope (Axio Imager A.2; Carl Zeiss, Oberkochen, Germany), with a 40× /1.3 and 100× /1.3 oil-immersion objective lens (EC Plan-Neofluar; Carl Zeiss), with transmitted light and reflected fluorescence observation using cooled charge-coupled device cameras (Axiocam 503 color and Axiocam 503 monochrome; Carl Zeiss). Cameras were equipped with sensors having a physical pixel length of 4.54 µm, yielding image pixel sizes of 113.5 nm/pixel (40× objective) or 45.4 nm/pixel (100× objective). Fluorescence was excited using a broadband light-emitting diode source (X-Cite 120 LED; Excelitas Technologies Corp., Waltham, MA), and a mercury lamp for brightfield illumination. Green fluorescence labelled samples were imaged using a GFP filter (Filter Set 09; Carl Zeiss) and red fluorescence labelled samples were imaged using a TxRed filter (Filter Set 00; Carl Zeiss). Images were acquired using a Zeiss software (ZEN 2Blue, Carl Zeiss, Carl Zeiss, https://www.zeiss.com).