CHMP5 and infection: To search for an ultrastructural correlate to the increased initial infection rate of Delta PVs, the structures of murine leukemia virus (MLV)-based PVs bearing several different SARS-CoV-2 spike variants were examined by negative stain transmission electron microscopy (TEM): D614G, Alpha, Delta, Delta sublineage AY.4.2 (Delta AY.4.2), and Omicron sublineage BA.1 (Omicron BA.1, lineage B.1.1.529), along with ‘Bald PVs’, that lacked a spike glycoprotein.