Herpesvirus-Induced Cell Fusion (Polykaryocytosis)

Infection of a monolayer of LLC-RK1 cells with equine herpesvirus strain LK (EHV-2) results in cytopathic effects (CPE), characterized by syncytium formation, or polykaryocytosis, i.e., fusion of adjacent cells to form a multinucleate cell (see Fig. 1 to 3). CPE are used in presumptive diagnosis of viral infections and these imagaes can be used to help students visualize CPE.

Figure 1 shows an uninfected LLC-RK1 cell monolayer exhibiting polygonal cells and well-defined intercellular spaces. The image is magnified x128 using phase-contrast microscopy.

Figure 2 shows a presyncytial EHV-2-infected monolayer at 44 h postinfection, displaying extensive vacuolation, cytoplasmic bridges across intercellular spaces, and loss of cellular architecture. The image is magnified x128 using phase-contrast microscopy.

Figure 3 shows a large polykaryocyte in an EHV-2-infected monolayer of LLC-RK1 cells displaying many nuclei within a common cytoplasm at 45 h postinfection. The image is magnified x128 using phase-contrast microscopy.