Enhanced Antiviral Activity against Foot-and-Mouth Disease Virus by a Combination of Type 1 and 2 Porcine Interfereons

Authors: Moraes, Mauro; De Los Santos, Teresa; Koster, Marla; Turecek, Traci; WANG, HE - USDA, APHIS, FADDL, PIADC; ANDREYEV, VLADIMIR - ARRIAH, VLADIMIR, RUSSIA; Grubman, Marvin

Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2007
Publication Date: 7/1/2007
Citation: Moraes, M., De Los Santos, T., Koster, M.J., Turecek, T.E., Wang, H., Andreyev, V.G., Grubman, M.J. 2007. Enhanced Antiviral Activity against Foot-and-Mouth Disease Virus by a Combination of Type 1 and 2 Porcine Interfereons. Journal of Virology. Vol 81. No.13: P7124-7135

Interpretive Summary: Foot-and-mouth disease virus (FMDV) causes an economically devastating disease of cloven-hoofed animals including swine and cattle. Vaccines produced by chemical inactivation of virus as well as adenovirus vectored (Ad5) empty capsid vaccines are available, but neither induces protection prior to about 7 days post-vaccination. In the event of an FMD outbreak in a disease-free country such as the US, it is necessary to induce immediate protection. We have shown that in cell culture FMDV is inhibited by type I interferon (IFN) and we have developed recombinant Ad5s containing the genes for IFN alpha and beta. Swine administered one dose of Ad5 (10[9]pfu) containing porcine IFN alpha and then challenged with virulent FMDV one day post-inoculation were completely protected from clinical signs of disease and challenge virus replication. However, when we attempted to extend these studies to cattle, the animals were only partially protected from disease. Since this approach has not been completely effective we have attempted to develop new strategies to induce rapid protection in susceptible animals. Type II IFN (IFN gamma) has also been shown to have antiviral activity against a number of viruses. We constructed an Ad5 virus containing the gene for porcine IFN gamma and demonstrated that the expressed IFN gamma can block FMDV replication. We then inoculated swine with Ad5 viruses containing either IFN alpha (10[8]pfu) or interferon gamma (10[9] or 10[10] pfu) alone or in combination and the animals were challenged with FMDV one day later. Groups that received Ad5-IFNalpha or the low dose of Ad5-IFNgamma alone developed clinical disease and viremia. However, the group that received the combination of Ad5-IFNalpha and the low dose of Ad5-IFNgamma were completely protected from clinical disease and had no serological indication of challenge virus replication. In this manuscript we discuss the possible mechanisms of protection induced by this treatment.

Technical Abstract: Previously, we showed that type I interferon (IFN alpha/beta) can inhibit foot-and-mouth disease virus (FMDV) replication in cell culture and swine inoculated with 109 pfu human adenovirus type 5 expressing porcine IFN-alpha (Ad5-pIFN alpha) were protected when challenged one day later. In this study we found that type 2 porcine IFN (pIFN-gamma) also has antiviral activity against FMDV in cell culture and in combination with pIFN-alpha 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, 10^8 pfu Ad5-pIFN alpha, low or high dose Ad5-pIFN gamma, or the combinations and challenged all groups with FMDV one day later. The control group and the groups inoculated with either Ad5-pIFN alpha or a low dose of Ad5-pIFN gamma developed clinical disease and viremia. However, the group that received the combination of both Ad5-IFNs at the above doses was completely protected from challenge and had no viremia. Similarly the groups inoculated with both Ad5s at the higher dose of Ad5-pIFN gamma and with only high dose Ad5-pIFN gamma were also 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 1 and 2 IFNs act synergistically to inhibit FMDV replication in vitro and in vivo.