Fig. 1.

Morphological and viral characterization of 3867K cells, a new MDCC line induced by vRB-1B EGFP47 MDV. (a) Examination by light microscopy after MGG staining. (b) UL47EGFP was spontaneously expressed in a small proportion of 3867K cells, which were selectable by cell sorting on the basis of EGFP fluorescence, with a yield of 88 %. SS, side scatter. (c) RT-PCR performed on EGFP-positive and -negative sorted cells indicates that EGFP-positive cells expressed various RNAs encoding MDV lytic proteins, such as UL13, US3 and ICP4. (d) EGFP-positive cells, without sorting or after cell sorting, expressed various MDV lytic antigens (red) detected by fluorescence microscopy. Nuclei were counterstained with Hoechst 33342 (blue) and EGFP was observed directly (co-staining with anti-VP22 or -VP5). (e) F-actin staining with Alexa Fluor 594–phalloidin. Two-dimensional (2D) projections of a 40z stack (left) and three-dimensional (3D) reconstruction (right) showed that filopodia were reduced or absent from EGFP-positive cells but were numerous on most EGFP-negative cells. No EGFP signal was present at the cell surface, indicative of the absence of extracellular virions.