2'-5' Oligoadenylate synthetase plays a critical role in interferon-gamma inhibition of respiratory syncytial virus infection of human epithelial cells.
Respiratory syncytial virus (RSV), associated with bronchiolitis and asthma, is resistant to the antiviral effects of type-I interferons (IFN), but not IFN-gamma. However, the antiviral mechanism of IFN-gamma action against RSV infection is unknown. The molecular mechanism of IFN-gamma-induced antiviral activity was examined in this study using human epithelial cell lines HEp-2 and A549. Exposure of these cells to 100-1000 units/ml of IFN-gamma, either before or after RSV infection, results in a significant decrease in RSV infection. After 1 h of exposure, IFN-gamma induces protein expression of IFN regulatory factor-1 (IRF-1) but not IRF-2, double-stranded RNA-activated protein kinase, and inducible nitric-oxide synthase in these cells. The mRNA for IRF-1, p40, and p69 isoforms of 2'-5' oligoadenylate synthetase (2-5 AS) are detectable, respectively, at 1 and 4 h of IFN-gamma exposure. Studies using cycloheximide and antisense oligonucleotides to IRF-1 indicate a direct role of IRF-1 in activating 2-5 AS. Cells transfected with 2-5 AS antisense oligonucleotides inhibit the antiviral effect of IFN-gamma. A stable cell line of HEp-2 overexpressing RNase L inhibitor, RLI-14, which exhibits an IFN-gamma-induced gene expression pattern similar to that of the parent cell line, shows a significant reduction in RNase L activity and IFN-gamma-mediated antiviral effect, compared with HEp-2 cells. These results provide direct evidence of the involvement of 2-5 AS in IFN-gamma-mediated antiviral activity in these cells.
Behera
Aruna K
AK
Division of Allergy and Immunology, Joy McCann Culverhouse Airway Disease Center, University of South Florida College of Medicine and James A. Haley Veterans Affairs Hospital, Tampa 33612, USA.
Kumar
Mukesh
M
Lockey
Richard F
RF
Mohapatra
Shyam S
SS
D015088:2',5'-Oligoadenylate Synthetase / Q000378:metabolism*; D000998:Antiviral Agents / Q000502:physiology*; D001483:Base Sequence; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004722:Endoribonucleases / Q000378:metabolism; D004847:Epithelial Cells / Q000821:virology; D006801:Humans; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D018357:Respiratory Syncytial Virus Infections / Q000201:enzymology* / Q000378:metabolism; D018113:Respiratory Syncytial Virus, Human / Q000302:isolation & purification*; D015854:Up-Regulation
D000998:Antiviral Agents; D017931:DNA Primers; D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D016376:Oligonucleotides, Antisense; D010750:Phosphoproteins; D007371:Interferon-gamma; D003513:Cycloheximide; D015088:2',5'-Oligoadenylate Synthetase; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease