The herpes group of viruses

Herpesviruses include

• herpes simplex virus (types 1 and 2)
• cytomegalovirus
• varicella zoster virus

All herpesviruses replicate in the nucleus of the cell. An accumulation of viral proteins results in the formation of characteristic eosinophilic intranuclear inclusions.
Minor differences in CPE allow distinction between the different types of herpesvirus.

1. Prominent foci, or plaques, of rounded cells typifies infection with HSV-1.
   
2. The nuclei become distorted and contain eosinophilic inclusions.
   
3. Other manifestations of CPE include the formation of "giant cells", and also multi-nucleate syncytia (most common with HSV type 2).

Human cytomegalovirus replicates only in fibroblast cells (not in epithelial cells).
The virus is slow-growing and thus foci are small and discrete. Characteristic eosinophilic "owl-eye" inclusions are evident in the nuclei of infected cells.

Varicella zoster virus

Varicella zoster virus will replicate in either epithelial cells (as shown here) or fibroblasts.
CPE takes much longer to become apparent than with HSV.

Nuclei of infected cells become enlarged and display prominent eosinophilic intra-nuclear inclusions.
Rounding of cells and strong affinity for eosin, is characteristic at late stages of infection.

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