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Enhanced Antiviral Activity against Foot-and-Mouth Disease Virus by a Combination of Type I and II Porcine Interferons

Mauro Pires Moraes,¹ Teresa de los Santos,¹ Marla Koster,¹ Traci Turecek,¹ He Wang,² Vladimir G. Andreyev,^1, and Marvin J. Grubman^1*

Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York 11944,¹ Foreign Animal Disease Diagnostic Laboratory, Plum Island Animal Disease Center, Animal Plant and Health Inspection Service, U.S. Department of Agriculture, Greenport, New York 11944²

Received 15 December 2006/ Accepted 13 April 2007

Previously, we showed that type I interferon (alpha/beta interferon [IFN-/ß]) can inhibit foot-and-mouth disease virus (FMDV) replication in cell culture, and swine inoculated with 10⁹ PFU of human adenovirus type 5 expressing porcine IFN- (Ad5-pIFN-) were protected when challenged 1 day later. In this study, we found that type II pIFN (pIFN-) also has antiviral activity against FMDV in cell culture and that, in combination with pIFN-, it has a synergistic antiviral effect. We also observed that while each IFN alone induced a number of IFN-stimulated genes (ISGs), the combination resulted in a synergistic induction of some ISGs. To extend these studies to susceptible animals, we inoculated groups of swine with a control Ad5, 10⁸ PFU of Ad5-pIFN-, low- or high-dose Ad5-pIFN-, or a combination of Ad5-pIFN- and low- or high-dose Ad5-pIFN- and challenged all groups with FMDV 1 day later. The control group and the groups inoculated with either Ad5-pIFN- or a low dose of Ad5-pIFN- developed clinical disease and viremia. However, the group that received the combination of both Ad5-IFNs with the low dose of Ad5-pIFN- was completely protected from challenge and had no viremia. Similarly the groups inoculated with the combination of Ad5s with the higher dose of Ad5-pIFN- or with only high-dose Ad5-pIFN- were protected. The protected animals did not develop antibodies against viral nonstructural (NS) proteins, while all infected animals were NS protein seropositive. No antiviral activity or significant levels of IFNs were detected in the protected groups, but there was an induction of some ISGs. The results indicate that the combination of type I and II IFNs act synergistically to inhibit FMDV replication in vitro and in vivo.

Published ahead of print on 25 April 2007.

Present address: Laboratory of Gene Engineering, All-Russian Research Institute for Animal Health, Vladimir, Russia.