of the virus per se and cellular NF-κB activity; and (ii) to study the underling mechanisms. We found that tylophorine-based compounds target the TGEV viral RNA and effectively inhibit TGEV replication. NF-κB inhibition also leads to anti-TGEV replication. NF-κB activation induced by TGEV infection was found to be associated with two convergent pathways, IKK-2_IκBα/p65 and JAK2 mediated p65 phosphorylation, in swine testicular cells. JAK2 inhibition either by CYT387 (a JAK family inhibitor) or by silencing JAK2-expression revealed a dominant JAK2 mediated p65 phosphorylation pathway for NF-κB activation and resulted in NF-κB inhibition, which overrode the IκBα regulation via the IKK-2. Finally, tylophorine-based compounds work cooperatively with CYT387 to impart comprehensive anti-TGEV activities. The combination treatment, wherein a tylophorine compound targets TGEV and a JAK2 inhibitor blocks the alternative dominant NF-κB activation mediated by JAK2, is more effective and comprehensive than either one alone and constitutes a feasible approach for the treatment of SARS-CoV or MERS-CoV. Coronaviruses are animal viruses containing an enveloped, positive-sense, single-stranded RNA genome; and include the common cold human coronavirus (CoV)-229E & CoV-OC43, severe acute respiratory syndrome (SARS) CoV, Middle East respiratory syndrome (MERS) CoV, porcine transmissible gastroenteritis virus (TGEV), and murine hepatitis virus (MHV) etc 1-3 . Since the 2003 SARS outbreak (which had a mortality rate of ~10%), novel anti-SARS-CoV treatments have been vigorously pursued. No new cases of SARS have been reported since the 2003 outbreak, but another novel coronavirus (MERS-CoV), this time with a mortality rate of ~35%, came to light in 2012 4 . To date, neither a commercially available vaccine for human coronaviruses nor a specific treatment for SARS-CoV or MERS-CoV is available. Coronaviruses primarily infect the upper respiratory and gastrointestinal tract and induce host inflammation 5 . Nuclear factor κB (NF-κB) activation by coronaviruses is usually responsible for mediating the production of pro-inflammatory cytokines and chemokines and thus plays an important role in the pathogenesis of disease caused by coronaviruses 6, 7 . Inhibition of NF-κB-mediated inflammation induced by coronavirus in mice was reported to increase the survival rate 6 . Thus, NF-κB inhibitors constitute a promising class of antivirals in infections caused by pathogenic coronaviruses. However, targeting NF-κB is limited by intrinsic pathway complexity, cross talk with other pathways, and drug resistance 8 . In addition, many small chemical molecules targeting either viral entry or the intracellular viral life cycle were reported to impart anti-coronavirus activity 2, 9, 10 . Despite these advances, however, SARS-CoV and MERS-CoV remain untreatable diseases for which novel therapies are sought. Published: xx xx xxxx OPEN www.nature.com/scientificreports/ 2 Scientific RepoRts | 7: 4105 | Tylophorine based compounds, whether isolated from plants, e.g. Asclepiadaceae and Moraceae or chemically synthesized, exert potent anti-coronaviral activities against a variety of coronaviruses including SARS-CoV, MHV, and TGEV 11, 12 , but both the underlying mechanism(s) of this inhibitory effect and the target are unknown. NF-κB is significantly activated after infection by coronaviruses, e.g. TGEV, and MHV etc 6, 7, [13] [14] [15] . Otherwise, coronaviral nucleocapsid (N) protein plays a vital role in the regulation of viral genome replication and host gene transcription 16 . Therefore, the combination treatment for the inhibition of coronavirus per se, e.g. viral genome replication, and blocking cellular NF-κB activation by coronaviruses, is a promising approach for the development of anti-coronavirals. TGEV infected swine testicular (ST) cells constitute a surrogate system for the search and study of potential anti-coronavirus agents 11, 12, 17 . Herein, we report: (1) tylophorine-based compounds exert potent anti-TGEV replication by directly targeting the viral RNA/ribonucleoprotein (RNP) complex for viral replication/synthesis; (2) NF-κB inhibition also leads to anti-TGEV replication; (3) A combination treatment consisting of both a tylophorine compound and an NF-κB inhibitor acts additively or synergically to more effectively and comprehensively inhibit TGEV replication than either (1) or (2) alone.
Output: Targeting Coronaviral Replication and Cellular JAK2 Mediated Dominant NF-κB Activation for Comprehensive and Ultimate Inhibition of Coronaviral Activity OPEN