Synergistic inhibition of human cytomegalovirus replication by interferon-alpha/beta and interferon-gamma.
BACKGROUND
Recent studies have shown that gamma interferon (IFN-gamma) synergizes with the innate IFNs (IFN-alpha and IFN-beta) to inhibit herpes simplex virus type 1 (HSV-1) replication in vitro. To determine whether this phenomenon is shared by other herpesviruses, we investigated the effects of IFNs on human cytomegalovirus (HCMV) replication.


RESULTS
We have found that as with HSV-1, IFN-gamma synergizes with the innate IFNs (IFN-alpha/beta) to potently inhibit HCMV replication in vitro. While pre-treatment of human foreskin fibroblasts (HFFs) with IFN-alpha, IFN-beta or IFN-gamma alone inhibited HCMV plaque formation by approximately 30 to 40-fold, treatment with IFN-alpha and IFN-gamma or IFN-beta and IFN-gamma inhibited HCMV plaque formation by 163- and 662-fold, respectively. The generation of isobole plots verified that the observed inhibition of HCMV plaque formation and replication in HFFs by IFN-alpha/beta and IFN-gamma was a synergistic interaction. Additionally, real-time PCR analyses of the HCMV immediate early (IE) genes (IE1 and IE2) revealed that IE mRNA expression was profoundly decreased in cells stimulated with IFN-alpha/beta and IFN-gamma (approximately 5-11-fold) as compared to vehicle-treated cells. Furthermore, decreased IE mRNA expression was accompanied by a decrease in IE protein expression, as demonstrated by western blotting and immunofluorescence.


CONCLUSIONS
These findings suggest that IFN-alpha/beta and IFN-gamma synergistically inhibit HCMV replication through a mechanism that may involve the regulation of IE gene expression. We hypothesize that IFN-gamma produced by activated cells of the adaptive immune response may potentially synergize with endogenous type I IFNs to inhibit HCMV dissemination in vivo.
Sainz
Bruno
B
Department of Microbiology and Immunology, Program in Molecular Pathogenesis and Immunity, Tulane University Health Sciences Center, 1430 Tulane Avenue, SL-38, New Orleans, LA 70112, USA. bsainz@scripps.edu
LaMarca
Heather L
HL
Garry
Robert F
RF
Morris
Cindy A
CA
D000998:Antiviral Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000187:drug effects* / Q000276:immunology / Q000502:physiology*; D004357:Drug Synergism; D005347:Fibroblasts / Q000648:ultrastructure / Q000821:virology; D015967:Gene Expression Regulation, Viral; D006801:Humans; D016898:Interferon-alpha / Q000276:immunology / Q000494:pharmacology*; D016899:Interferon-beta / Q000276:immunology / Q000494:pharmacology*; D007371:Interferon-gamma / Q000276:immunology / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D010948:Viral Plaque Assay; D014779:Virus Replication / Q000187:drug effects*
D000998:Antiviral Agents; D016898:Interferon-alpha; D012333:RNA, Messenger; D016899:Interferon-beta; D007371:Interferon-gamma
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