Figure 2. Multi-core membrane-enclosed structures do not arise through fusion or sample processing.

(a) A tomographic slice of a multi-core structure from the Env^neg strain. Scale bar, 50 nm. (b) 3D rendering of the structure in a depicting an immature Gag assembly (1) and two mature cores (2, 3). Core 2 is detached from the membrane. Core 3 has an aberrant, incomplete sheet structure. (c–e) Multi-core structure found in a cell culture sample. (c) TEM shows regular virions and a structure with two cores, which are not in contact with the membrane at the wide end. Scale bar, 500 nm. (d) A slice through a multi-core structure and regular virions near a cell obtained by FIB-SEM. Scale bar, 500 nm. (e) 3D visualization shows three cores inside the structure from d.