Fig. 1

Localized RSV transmission occurs within the HEp2 cell monolayers. HEp2 cell monolayers were either mock-infected or RSV-infected using a multiplicity of infection (moi) of 0.0002. a At between 1 and 5 days post-infection (dpi) the monolayers in the tissue culture dish were fixed using 3 % glutaraldehyde and viewed using an inverted light microscope (objective x4 magnification). The virus-induced morphological changes in the monolayer are highlighted (black arrows). b In a parallel analysis the virus-infected cells were stained using anti-RSV and anti-mouse IgG conjugated to Alexa 488 at (i) 1 dpi, (ii) 2 dpi, (iii) 3 dpi and (iv) 4 dpi. The stained cells were then viewed using fluorescence microscopy (IF) and by bright-field (BF) microscopy (objective x20 magnification). The infected cell cluster (open white box), virus-induced morphological changes in the monolayer (open black box) and region of the monolayer cleared of cells (*) are highlighted. c and d Distribution of the F, G and SH virus glycoproteins in the infected cell clusters. HEp2 cell monolayers were infected with RSV using infection moi of 0.01 and 30 h post-infection the cells were fixed and stained using either (c) anti-G and anti-F or (d) anti-SH and anti-F. d(ii) is an enlarged image from (d) (i)). The stained cells were viewed using confocal microscopy at an optical plane that allowed imaging of the virus filaments. The virus filaments (white arrow) and the typical Golgi staining in the SH stained cells (*) are indicated