%0 Journal Article %A Bell, John C. %A Campione-Piccardo, Jose %A Craig, Jane %A Reuhl, Kenneth R. %A McBurney, Michael W. %T Restricted Replication of Herpes Simplex Virus Type 1 in Murine Embryonal Carcinoma Cells %D 1987 %J Journal of General Virology, %V 68 %N 2 %P 555-568 %@ 1465-2099 %R https://doi.org/10.1099/0022-1317-68-2-555 %K restricted/EC cells %K HSV-I/replication %I Microbiology Society, %X SUMMARY Herpes simplex virus type 1 (HSV-1) has a broad host range but the KOS strain of HSV-1 did not replicate efficiently in murine embryonal carcinoma (EC) cells. The yield of infectious HSV-1 from EC cells was 100- to 1000-fold lower than that from fibroblast cell lines of mouse, monkey or human origin. The thymidine kinase (TK) gene of HSV-1 is expressed early during the infectious cycle. The levels of TK mRNA and of TK activity in infected EC cells were only two- to threefold lower than levels from infected fibroblast cells. Infected EC cells supported replication of about half as much HSV-1 DNA as did fibroblast cells. The reduced yield of infectious virus was consistent with a paucity of virions in infected EC cells examined by electron microscopy, suggesting a major block late during the HSV-1 infectious cycle. We isolated a variant strain of HSV-1, called KOSEC, which replicated as efficiently in EC cells as in mouse fibroblasts. KOSEC infected EC and fibroblast cells, synthesized more TK mRNA, more TK enzyme, and more HSV-1 DNA than did the same cells infected with the KOS stain. Both HSV-1 strains induced similar levels of synthesis of gD, an early viral glycoprotein. By co-infection of EC cells with the KOS and KOSEC virus, both the elevated virus yield and the elevated TK synthesis seen in KOSEC-infected cells appeared to be recessive. Apparently a viral mutation that affects expression of some early viral functions can also overcome the EC cell restriction to HSV-1 replication. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-68-2-555