RO 90-7501 Enhances TLR3 and RLR Agonist Induced Antiviral Response

Abstract

Recognition of virus infection by innate pattern recognition receptors (PRRs), including membrane-associated toll-like receptors (TLR) and cytoplasmic RIG-I-like receptors (RLR), activates cascades of signal transduction pathways leading to production of type I interferons (IFN) and proinflammatory cytokines that orchestrate the elimination of the viruses. Although it has been demonstrated that PRR-mediated innate immunity plays an essential role in defending virus from infection, it also occasionally results in overwhelming production of proinflammatory cytokines that cause severe inflammation, blood vessel leakage and tissue damage. In our efforts to identify small molecules that selectively enhance PRR-mediated antiviral, but not the detrimental inflammatory response, we discovered a compound, RO 90–7501 (‘2’-(4-Aminophenyl)-[2,5′-bi-1H-benzimidazol]-5-amine), that significantly promoted both TLR3 and RLR ligand-induced IFN-β gene expression and antiviral response, most likely via selective activation of p38 mitogen-activated protein kinase (MAPK) pathway. Our results thus imply that pharmacological modulation of PRR signal transduction pathways in favor of the induction of a beneficial antiviral response can be a novel therapeutic strategy.

Inhibition of Pyrimidine Biosynthesis Pathway Suppresses Viral Growth through Innate Immunity

“…Altogether, our results support the idea that the antiviral activity of pyrimidine synthesis inhibitors, including aforementioned compounds [33], [34], [35], [36], does not simply rely on depriving viral polymerases of nucleosides, but is mediated through amplification of innate immune response. Conversely, other research groups have isolated broad-spectrum antiviral molecules while searching for stimulators of innate antiviral genes much like we did, using cell-based assays with reporter genes [9], [21], [22], [23], [24], [25]. With our results in mind, it should be determined if the antiviral molecules they identified based on their capacity to stimulate interferon-inducible antiviral genes are in fact pyrimidine synthesis inhibitors, or if they stimulate innate immunity through alternative pathway.…”

“…They also tend to escape drugs that target viral proteins through mutations, thus calling for innovative therapeutic approaches. Among possible strategies, chemical modulators of host pathways [3], [4], [5], [6], and in particular stimulators of innate immune response that boost cellular defenses to eliminate viral pathogens are of growing interest [7], [8], [9], [10]. In principle, such molecules would be efficient against a large panel of viral pathogens since the host immune response relies on a multiplicity of antiviral effectors that block viruses at several steps of their replication, and cover the variety of replication strategies they use.…”

“…Molecules that engage TLRs or IFN-α/β receptors have been identified using various combinations of functional screens, in silico molecular docking and binding assays [18], [19]. Phenotypic screens have also been used to identify stimulators of the antiviral gene cluster [9], [20], [21], [22], [23], [24], [25]. Several groups have recently described similar assays based on cells transfected with a reporter gene under control of IFN-stimulated response elements (ISRE) [21], [22], [23].…”

An interferon-beta promoter reporter assay for high throughput identification of compounds against multiple RNA viruses

“…In order to quantitatively measure the TLR3 and RLR-mediated innate antiviral immune response, a TLR3-expressing HEK293 cell line stably expressing a firefly luciferase reporter gene under the control of a human IFN-β promoter (Li et al, 2005), designated 293TLR3/IFNβLuc, was established (Guo et al, 2012). Because the cell line has an intact intrinsic RLR pathway and a reconstituted TLR3 pathway (Guo et al, 2012; Yoneyama et al, 2005), the reporter gene should respond to infection by viruses that are able to activate one or both of the pathways. Indeed, as shown in Fig.1, infection of the cell line with DENV, YFV, TCRV, EMCV or SenV induced luciferase expression in an inoculum size (MOI)-or hemagglutination units (HAU)-dependent manner.…”

Gemcitabine, a broad-spectrum antiviral drug, suppresses enterovirus infections through innate immunity induced by the inhibition of pyrimidine biosynthesis and nucleotide depletion

“…This strategy would have a low potential of producing resistant viruses, but undesirable side effects could be accompanied. The other is activating innate immune response such as interferon (IFN) signaling so as to boost host antiviral defense system [6][7][8][9]. Actually, IFN itself or in combination with other antiviral drugs such as ribavirin has been primarily used for the treatment of various RNA virus infections.…”