HSV alkaline nuclease as a target for antiviral therapy

About This Grant

ABSTRACT Genital herpes, a lifelong sexually transmitted infection caused by either Herpes Simplex Virus 1 or 2 (HSV1/2), is one of the most common STDs in the US with (846 million people infected worldwide). HSV1/2 can cause oral and genital lesions and establish lifelong latent infections which can undergo periodic reactivation. Reactivation can cause painful ulcers and blisters; however, many reactivations are asymptomatic, causing an increased risk of partner transmission. HSV reactivation is particularly problematic in immunocompromised patients and can lead to disseminated life-threatening infections. HSV can also be transmitted to newborns either during or after birth, potentially leading to serious neurological disorders. The severity of this public health epidemic is intensified by the lack of protective vaccines and the inability to cure infections with existing antiviral therapies. Furthermore, it is now recognized that HSV infection can increase the risk of HIV infection. Existing therapies have focused on the HSV DNA polymerase as a target, and most HSV polymerase inhibitors are nucleoside/tides, which are often associated with drug resistance, narrow spectrum and dose-limiting toxicities. New agents with different modes of action are needed not only for the treatment of resistant viruses but also for use in combination therapy to reduce dose-limiting toxicities. New therapies used prophylactically would prevent pathological sequelae of reactivation, as well as viral shedding and transmission to new hosts. We have identified the HSV alkaline nuclease (AN) as a promising and novel HSV target for anti-herpesvirus drug discovery efforts. HSV1 and HSV2 AN are encoded by the UL12 gene, which is highly conserved between HSV1 and 2. We have had a long- standing interest in understanding the role of AN in viral replication primarily relying on genetic methods. A null mutant in AN and a point mutation in the nuclease active site (D340E) are unable to produce infectious virus in cell culture. AN is a member of a large class of two-metal ion-dependent (TMID) enzymes, whose active sites coordinate divalent cations essential for catalysis. Many viruses utilize TMID enzymes for processing and manipulation of viral nucleic acids. The successful development of selective and safe inhibitors of two viral TMID enzymes (HIV integrase and influenza endonuclease, PA) shows that it is possible to block TMID nuclease activity by metal-coordinating enzyme inhibitors. We have shown that the HSV alkaline nuclease is essential for productive HSV infection as nuclease dead HSV mutants are defective in viral spread and virus production. Furthermore, we have identified several lead compounds that block AN activity and produce strong antiviral responses in cell culture and animal models. In this proposal we will continue our efforts to develop antiviral agents that inhibit HSV1/2 alkaline nuclease, UL12.