Intracellular restriction of a productive noncytopathic coronavirus infection.
Virus infection in vitro can either result in a cytopathic effect (CPE) or proceed without visible changes in infected cells (noncytopathic infection). We are interested in understanding the mechanisms controlling the impact of coronavirus infection on host cells. To this end, we compared a productive, noncytopathic infection of murine hepatitis virus (MHV) strain A59 in the fibroblastlike cell line NIH 3T3 with cytopathic MHV infections. Infected NIH 3T3 cells could be cultured for up to 4 weeks without apparent CPE and yet produce virus at 10(7) to 10(8) PFU/ml. Using flow cytometry, we demonstrated that NIH 3T3 cells expressed as much MHV receptor CEACAM1 as other cell lines which die from MHV infection. In contrast, using quantitative reverse transcription-PCR and metabolic labeling of RNA, we found that the rate of viral RNA amplification in NIH 3T3 cells was lower than the rate in cells in which MHV induces a CPE. The rate of cellular RNA synthesis in contact-inhibited confluent NIH 3T3 cells was also lower than in cells permissive to cytopathic MHV infection. However, the induction of cellular RNA synthesis in growing NIH 3T3 cells did not result in an increase of either viral RNA amplification or CPE. Our results suggest that a specific, receptor CEACAM1-independent mechanism restricting coronaviral RNA synthesis and CPE is present in NIH 3T3 and, possibly, other cells with preserved contact inhibition.
Slobodskaya
Olga
O
Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, LUMC E4-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
Laarman
Alexander
A
Spaan
Willy J M
WJ
D000818:Animals; D002272:Carcinoembryonic Antigen / Q000032:analysis; D002462:Cell Membrane / Q000737:chemistry; D003588:Cytopathogenic Effect, Viral; D003600:Cytosol / Q000737:chemistry; D005434:Flow Cytometry; D051379:Mice; D006517:Murine hepatitis virus / Q000254:growth & development* / Q000502:physiology; D041681:NIH 3T3 Cells; D012367:RNA, Viral / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014779:Virus Replication
D002272:Carcinoembryonic Antigen; C486183:Ceacam1 protein, mouse; D012367:RNA, Viral