Broad-spectrum antiviral that interferes with de novo pyrimidine biosynthesis

Abstract

Compound A3 was identified in a high-throughput screen for inhibitors of influenza virus replication. It displays broad-spectrum antiviral activity, and at noncytotoxic concentrations it is shown to inhibit the replication of negative-sense RNA viruses (influenza viruses A and B, Newcastle disease virus, and vesicular stomatitis virus), positive-sense RNA viruses (Sindbis virus, hepatitis C virus, West Nile virus, and dengue virus), DNA viruses (vaccinia virus and human adenovirus), and retroviruses (HIV). In contrast to mammalian cells, inhibition of viral replication by A3 is absent in chicken cells, which suggests species-specific activity of A3. Correspondingly, the antiviral activity of A3 can be linked to a cellular protein, dihydroorotate dehydrogenase (DHODH), which is an enzyme in the de novo pyrimidine biosynthesis pathway. Viral replication of both RNA and DNA viruses can be restored in the presence of excess uracil, which promotes pyrimidine salvage, or excess orotic acid, which is the product of DHODH in the de novo pyrimidine biosynthesis pathway. Based on these findings, it is proposed that A3 acts by depleting pyrimidine pools, which are crucial for efficient virus replication.

Broad-spectrum inhibition of common respiratory RNA viruses by a pyrimidine synthesis inhibitor with involvement of the host antiviral response

“…Our study into the mechanism of action of this compound indicates that FA-613 interferes with the cellular de novo pyrimidine biosynthesis pathway. Broad-spectrum antiviral activity of pyrimidine synthesis inhibitors has been identified previously and their antiviral effect has been mainly attributed to the depletion of the nucleosides necessary for replication of the viral genome [18][19][20]. Surprisingly, however, we found a connection between the antiviral activity of FA-613 and the use of cells that lack a functional interferon pathway.…”

“…The interaction between the host de novo pyrimidine synthesis pathway and host innate immunity is still unclear at present. A3, a compound with a distinct molecular structure from FA-613, was previously reported to similarly target the pyrimidine biosynthesis pathway through targeting of DHODH [19]. In contrast to FA-613, A3 did not show cell-type dependency and was able to inhibit infection in Vero cell lines effectively.…”

“…In contrast to FA-613, A3 did not show cell-type dependency and was able to inhibit infection in Vero cell lines effectively. The authors further mentioned that no induction of IFNB1 and other antiviral genes was found upon treatment of infected cells with A3 [19]. Another recent report describes a pyrimidine synthesis inhibitor that maintains its activity in Vero cells, and elicits an interferon-independent antiviral state [24].…”

“…FA-613 interferes with pyrimidine metabolism Several broad-spectrum antivirals were reported to be pyrimidine synthesis inhibitors through inhibition of dihydroorotate dehydrogenase (DHODH) [18][19][20], the fourth enzyme of the de novo pyrimidine biosynthesis pathway (Fig. 3a), and it has been speculated that the inhibition activity of these compounds is a direct consequence of the deprivation of the nucleosides necessary for virus replication.…”

High-throughput Screening for Broad-spectrum Chemical Inhibitors of RNA Viruses

“…Optional: supplement culture medium with uridine at 20 μg/ml. Note: When screening chemical libraries for viral replication inhibitors, it seems that compounds targeting early steps of pyrimidine biosynthesis pathway are frequently isolated 13,16,27,28 . The addition of uridine to culture medium is used to filter out such antiviral molecules.…”