ET of reovirus egress zones. HBMECs were adsorbed with reovirus T1L M1-P208S at an MOI of 1 PFU/cell and processed at 18 hpi by high-pressure freezing, freeze-substitution, semithick sectioning, and TEM. (A and B) Double-tilt tomography. (A) Computational tomographic slices showing an MC close to the plasma membrane (pm) with membranous channels (white arrowheads) and virions. (B) An MC contacting the plasma membrane in which virions are attached to filaments (white arrows). Viral particles associate with membranous channels (black arrowheads) in the MC–plasma membrane interface. Virions released to the extracellular medium are labeled with black arrows. (C) 3D reconstructions of reovirus egress zones. Left: An MC (gold) with membranous channels (beige) and virions (blue). The plasma membrane is colored in green. Right: An MC loaded with virions (blue) is observed to contact and fuse with the plasma membrane (green). Virions inside the MC are bound to filaments (pink). The dashed red box marks the fusion between the MC channels and the plasma membrane. The inset is an enlarged image of the fusion zone between the MC and the plasma membrane. Asterisks mark the membranous channels contacting the plasma membrane. Scale bars, 200 nm. A tomogram movie is presented in Video 1.