Fig. 1.

Different viral forms. The images show thawed cryo-sections of HeLa cells prepared at 12 h post infection with VACV and immunolabelled with anti-A14, a major membrane protein of VACV.

A. The immature forms; crescents (cr) that can appear as small arcs or as incomplete circles, immature virions (IVs) that appear as circles and immature virions with nucleoid (IVN, star indicates the DNA). Note that the crescents are often in close proximity to labelled membranes with which they sometimes seem to be continuous (thin arrows). The thick arrows point to the spike-like appearing scaffold on the convex side of the crescent.

B. Different views of mature virus (MV); although the MV is homogenous in size and shape the particle is asymmetric (brick-shaped) leading to different appearances by thin section EM. Scale bars-200 nm.