Specific inhibitors of herpes simplex virus thymidine kinase diminish reactivation of latent virus from explanted murine ganglia

Abstract

Two specific inhibitors of herpes simplex virus thymidine kinase, N2-phenyl-2'-deoxyguanosine and N2-(m-trifluoromethylphenyl)guanine, were tested for their ability to inhibit the reactivation of virus from explant cultures of latently infected murine trigeminal ganglia. Both compounds significantly diminished the frequency of reactivation compared with that of untreated controls. We and others have recently shown that although thymidine kinase (TK)-negative HSV mutants fail to reactivate after explant culture, they do express the latency-associated transcripts in sensory neuronal nuclei (2, 11, 18) and can be reactivated by superinfection-rescue with complementing virus (2, 4). These data demonstrate that TK is not required for establishment of latency and suggest that TK is required for reactivation.The apparent requirement for TK in animal models of latency and pathogenesis has led to efforts to develop anti-HSV drugs that inhibit HSV TK specifically (reviewed in reference 15). Two such drugs are N2-phenyl-2'-deoxyguanosine (PhdG) and N2-(m-trifluoromethylphenyl)guanine (m-CF3PhG) (6,7,15). These compounds are N2-substituted guanines, a family of compounds that can inhibit TK by competition with the enzyme substrates thymidine and deoxycytidine (15). Both PhdG and m-CF3PhG have demonstrated potent and selective inhibition of HSV TK in vitro (6, 7), and PhdG has been shown to inhibit HSV TK in HeLa cells and exhibit minimal cytotoxicity (6). m-CF3PhG also appears to be minimally cytotoxic; at 133 ,uM it had no detectable effect on the growth or morphology of HeLa cells, and neither it nor PhdG affected the morphology of Vero cells at concentrations up to 300 ,uM (unpublished results).In this study we used PhdG and m-CF3PhG in an animal model of HSV latency to test whether the selective inhibition of TK observed in vitro could translate to a selective inhibition of reactivation from explant cultures of latently infected murine trigeminal ganglia. These experiments allowed us to assess further the role of TK in the reactivation * Corresponding author.

Uracil in Oris of herpes simplex 1 alters its specific recognition by origin binding protein (OBP): does virus induced uracil-DNA glycosylase play a key role in viral reactivation and replication?

“…Some of these :functions are essential in adult neurons because of the absence of the cellular enzymatic counterparts. For instance, viral thymidine kinase, dispensable in peripheral replication of the virus, seems to be important for viral reactivation in nerve cells (Leib et al, 1990), where the cellular enzyme is not espressed. Recently we have demonstrated that uracil-DNA glycosylase, the enzyme which excises uracil residues from DNA, is also enzymatically undetectable in adult neurons Verri et al, 1992).…”

Comparison of Herpes Simplex Virus Reactivation in Ganglia In Vivo and in Explants Demonstrates Quantitative and Qualitative Differences

“…At the indicated times postexplant, ganglia were homogenized and plated exactly as for reactivation in vivo. Additional medium and serum conditions were tested in conjunction with the morphological and immunohistochemical studies including the conditions employed by several different groups (11,32,35), as well as the addition of nerve growth factor (44).…”

Stereoelectronic properties of five anti-HSV-1 2′-deoxynucleosides analogues with heterocyclic substituents in the 5-position: A comparison with BVDU

“…The modified nucleosides have a much higher affinity for HSV-1 thymidine kinase than for the cellular thymidine kinase, so that preferential phosphorylation in virus-infected cells occur. HSV-1 thymidine kinase could be a target for drugs which might prevent reactivation of HSV-1 when used prophylactically (Leib et al, 1990). …”