Genetic polymorphism of thymidine kinase (TK) and DNA polymerase (pol) of clinical varicella-zoster virus (VZV) isolates collected over three decades

Identification of novel potential inhibitors of monkeypox virus thymidine kinase using molecular docking, molecular dynamics simulation and MM/PBSA methods

The monkeypox spread has been announced a public health emergency of international concern (PHEIC) by the World Health Organization (WHO). Both monkeypox and smallpox viruses are placed in the genus Orthopoxvirus. Despite recommendations for the administration of smallpox drugs versus monkeypox, no specific drug for monkeypox has yet been introduced. A reliable and effective method against this outbreak can be the use of natural products. This study aimed for identification of natural flavonoid derivatives as potential thymidine kinase inhibitors, the main drug target of monkeypox virus. Thymidine kinase protein structure was predicted by homology modeling and the quality of generated model was evaluated. Then, the interaction between natural flavonoids and the modeled thymidine kinase was explored by molecular docking. Based on docking results, more than half of the flavonoids with higher docking scores compared to reference drug (ganciclovir) were exhibited better binding affinities toward the protein. In addition, stability of the top flavonoids including eupatorin, fisetin, rhamnetin and scutellarein, was confirmed by MD simulations and binding free energy calculations using MM/PBSA analysis. These selected compounds were also shown acceptable results for drug likeness and ADMET analysis. Therefore, the results of the study showed that these flavonoids could be considered as potential thymidine kinase inhibitors for use against monkeypox virus.

Identification of novel potential inhibitors of varicella-zoster virus thymidine kinase from ethnopharmacologic relevant plants through an in-silico approach

Although Varicella or chickenpox infection which is caused by the varicella-zoster virus (VZV) has significantly been managed through vaccination, it remains an infection that poses threats to the nearest future due to therapeutic drawbacks. The focus of this research was geared towards in silico screening for the identification of novel compounds in plants of ethnopharmacological relevance in the treatment of chicken pox in West Africa. The work evaluated 65 compounds reported to be present in Achillea millefolium, Psidium guajava and Vitex doniana sweet to identify potential inhibitors of thymidine kinase, the primary drug target of varicella zoster virus. Out of the 65 compounds docked, 42 of these compounds were observed to possess binding energies lower than -7.0 kcal/mol, however only 20 were observed to form hydrogen bond interactions with the protein. These interactions were elucidated using LigPlot⁺ and MM-PBSA analysis with residue Ala134 predicted as critical for binding. Pharmacological profiling predicted three potential lead compounds comprising myricetin, apigenin- 4' -glucoside and Abyssinone V to possess good pharmacodynamics properties and negligibly toxic. The molecules were predicted as antivirals including anti-herpes and involved in mechanisms comprising inhibition of polymerase, ATPase and membrane integrity, which were corroborated previously in other viruses. These drug-like compounds are plausible biotherapeutic moieties for further biochemical and cell-based assaying to discover their potential for use against chickenpox. Communicated by Ramaswamy H. Sarma.

40 Years after the Registration of Acyclovir: Do We Need New Anti-Herpetic Drugs?

Herpes simplex virus types 1 and 2 HSV1 and 2, namely varicella-zoster VZV and cytomegalovirus CMV, are among the most common pathogens worldwide. They remain in the host body for life. The course of infection with these viruses is often asymptomatic or mild and self-limiting, but in immunocompromised patients, such as solid organ or bone marrow transplant recipients, the course can be very severe or even life-threatening. Unfortunately, in the latter group, the highest percentage of infections with strains resistant to routinely used drugs is observed. On the other hand, frequent recurrences of genital herpes can be a problem even in people with normal immunity. Genital herpes also increases the risk of acquiring sexually transmitted diseases, including HIV infection and, if present in pregnant women, poses a risk to the fetus and newborn. Even more frequently than herpes simplex, congenital infections can be caused by cytomegalovirus. We present the most important anti-herpesviral agents, the mechanisms of resistance to these drugs, and the associated mutations in the viral genome. Special emphasis was placed on newly introduced drugs such as maribavir and brincidofovir. We also briefly discuss the most promising substances in preclinical testing as well as immunotherapy options and vaccines currently in use and under investigation.

Thymidine kinase and protein kinase in drug-resistant herpesviruses: Heads of a Lernaean Hydra

Herpesviruses thymidine kinase (TK) and protein kinase (PK) allow the activation of nucleoside analogues used in anti-herpesvirus treatments. Mutations emerging in these two genes often lead to emergence of drug-resistant strains responsible for life-threatening diseases in immunocompromised populations. In this review, we analyze the binding of different nucleoside analogues to the TK active site of the three α-herpesviruses [Herpes Simplex Virus 1 and 2 (HSV-1 and HSV-2) and Varicella-Zoster Virus (VZV)] and present the impact of known mutations on the structure of the viral TKs. Furthermore, models of β-herpesviruses [Human cytomegalovirus (HCMV) and human herpesvirus-6 (HHV-6)] PKs allow to link amino acid changes with resistance to ganciclovir and/or maribavir, an investigational chemotherapeutic used in patients with multidrug-resistant HCMV. Finally, we set the basis for the understanding of drug-resistance in γ-herpesviruses [Epstein-Barr virus (EBV) and Kaposi's sarcoma associated herpesvirus (KSHV)] TK and PK through the use of animal surrogate models.