Acyclovir, cidofovir, and amenamevir have additive antiviral effects on herpes simplex virus TYPE 1

Computational analysis of antiviral drugs using topological descriptors

Many health challenges are attributed to viral infections, which represent significant concerns in public health. Among these infections, diseases such as herpes simplex virus (HSV), cytomegalovirus (CMV), and varicella-zoster virus (VZV) infections have garnered attention due to their prevalence and impact on human health. There are specific antiviral medications available for the treatment of these viral infections. Drugs like Cidofovir, Valacyclovir, and Acyclovir are commonly prescribed. These antiviral drugs are known for their efficacy against herpesviruses and related viral infections, leveraging their ability to inhibit viral DNA polymerase. A molecular descriptor is a numerical value that correlates with specific physicochemical properties of a molecular graph. This article explores the calculation of distance-based topological descriptors, including the Trinajstic, Mostar, Szeged, and PI descriptors for the aforementioned antiviral drugs. These descriptors provide insights into these drugs' structural and physicochemical characteristics, aiding in understanding their mechanism of action and the development of new therapeutic agents.

Combination of ganciclovir and trifluridine prevents drug-resistance emergence in HSV-1

Ocular herpes simplex virus 1 (HSV-1) infections can lead to visual impairment. Long-term acyclovir (ACV) prophylaxis reduces the frequency of recurrences but is associated with drug resistance. Novel therapies are needed to treat drug-resistant HSV-1 infections. Here, we describe the effects of trifluridine (TFT) in combination with ACV or ganciclovir (GCV) on HSV-1 replication and drug-resistance emergence. Wild-type HSV-1 was grown under increasing doses of one antiviral (ACV, GCV, or TFT) or combinations thereof (ACV + TFT or GCV + TFT). Virus cultures were analyzed by Sanger sequencing and deep sequencing of the UL23 [thymidine kinase (TK)] and UL30 [DNA polymerase (DP)] genes. The phenotypes of novel mutations were determined by cytopathic effect reduction assays. TFT showed overall additive anti-HSV-1 activity with ACV and GCV. Five passages under ACV, GCV, or TFT drug pressure gave rise to resistance mutations, primarily in the TK. ACV + TFT and GCV + TFT combinatory pressure induced mutations in the TK and DP. The DP mutations were mainly located in terminal regions, outside segments that typically carry resistance mutations. TK mutations (R163H, A167T, and M231I) conferring resistance to all three nucleoside analogs (ACV, TFT, and GCV) emerged under ACV, TFT, ACV + TFT pressure and under GCV + TFT pressure initiated from suboptimal drug concentrations. However, higher doses of GCV and TFT prevented drug resistance in the resistance selection experiments. In summary, we identified novel mutations conferring resistance to nucleoside analogs, including TFT, and proposed that GCV + TFT combination therapy may be an effective strategy to prevent the development of drug resistance.

Efficacy and Safety of Amenamevir, a Helicase-Primase Inhibitor for the Treatment of Acyclovir-Resistant Herpes Simplex Virus 1 Keratitis

PURPOSE

The purpose of this study was to describe the efficacy and tolerance of amenamevir (AMNV), an inhibitor of the viral helicase-primase, for the treatment of recalcitrant herpes simplex keratitis (HSK) caused by acyclovir-resistant (ACVR) herpes simplex virus 1 strains.

METHODS

In this retrospective case series, 6 consecutive patients with HSK caused by an ACVR herpes simplex virus 1 strain with a failure of conventional antiviral therapy were included after having been treated with AMNV (there was no control group of comparable patients for whom previous treatment would have been continued despite its inefficacy). Medical files were assessed for clinical data including reason(s) for AMNV introduction (frequent recurrences despite appropriate preventive antiviral treatment and/or clinical resistance to suppressive antiviral treatment of an ongoing clinical relapse), genotypical resistance to herpes simplex virus 1 documentation, immune status, clinical types and number of HSK episodes before and during AMNV treatment, adverse effects observed during AMNV treatment, and best corrected visual acuity.

RESULTS

Of 6 patients, 4 (66%) did not experience a single recurrence during AMNV therapy while 2 others had recurrences (1 over 24 months of treatment and 2 over 23 months, ie two-fold less frequently than with conventional preventive treatment). On the overall history of these 6 patients, AMNV appeared to be associated with a reduction in HSK recurrences, with a mean of only 0.02 ± 0.04 episodes/month during follow-up under AMNV as compared to 0.14 ± 0.04 episodes/month in the year preceding AMNV introduction (P = 0.03). Improvement in vision acuity was also observed (mean best corrected visual acuity 0.17 ± 0.12 logarithm of the minimum angle of resolution at the end of follow-up vs. 0.30 ± 0.35 before AMNV onset), albeit nonsignificant probably due to the limited number of patients (P = 0.38). Neither clinical nor biological adverse effects were observed while under AMNV during the follow-up (16.5 ± 5.8 months).

CONCLUSIONS

Although there was no control group, AMNV may be a valuable option to reduce ACVR HSK recurrences.

Recent Developments in Semiconductor-Based Photocatalytic Degradation of Antiviral Drug Pollutants

The prevalence of antiviral drugs (ATVs) has seen a substantial increase in response to the COVID-19 pandemic, leading to heightened concentrations of these pharmaceuticals in wastewater systems. The hydrophilic nature of ATVs has been identified as a significant factor contributing to the low degradation efficiency observed in wastewater treatment plants. This characteristic often necessitates the implementation of additional treatment steps to achieve the complete degradation of ATVs. Semiconductor-based photocatalysis has garnered considerable attention due to its promising potential in achieving efficient degradation rates and subsequent mineralization of pollutants, leveraging the inexhaustible energy of sunlight. However, in recent years, there have been few comprehensive reports that have thoroughly summarized and analyzed the application of photocatalysis for the removal of ATVs. This review commences by summarizing the types and occurrence of ATVs. Furthermore, it places a significant emphasis on delivering a comprehensive summary and analysis of the characteristics pertaining to the photocatalytic elimination of ATVs, utilizing semiconductor photocatalysts such as metal oxides, doped metal oxides, and heterojunctions. Ultimately, the review sheds light on the identified research gaps and key concerns, offering invaluable insights to steer future investigations in this field.

Global expression and functional analysis of human piRNAs during HSV-1 infection

Piwi-interacting RNAs (piRNAs) are a class of non-coding RNAs that play a key role in spermatogenesis. However, little is known about their expression characterization and role in somatic cells infected with herpes simplex virus type 1 (HSV-1). In this study, we systematically investigated the cellular piRNA expression profiles of HSV-1-infected human lung fibroblasts. Compared with the control group, 69 differentially expressed piRNAs were identified in the infection group, among which 52 were up-regulated and 17 were down-regulated. The changes in the expression of 8 piRNAs were further verified by RT-qPCR with a similar expression trend. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the target genes of piRNAs were mainly involved in antiviral immunity and various human disease-related signaling pathways. Furthermore, we tested the effects of four up-regulated piRNAs on viral replication by transfecting piRNA mimics. The results showed that the virus titers of the group transfected with piRNA-hsa-28,382 (alias piR-36,233) mimic decreased significantly, and that of the group transfected piRNA-hsa-28,190 (alias piR-36,041) mimic significantly increased. Overall, our results revealed the expression characteristics of piRNAs in HSV-1-infected cells. We also screened two piRNAs that potentially regulate HSV-1 replication. These results may promote a better understanding of the regulatory mechanism of pathophysiological changes induced by HSV-1 infection.

A Systematic Review of Second-Line Treatments in Antiviral Resistant Strains of HSV-1, HSV-2, and VZV

Drug-resistant variants of herpes simplex viruses (HSV) have been reported that are not effectively treated with first-line antiviral agents. The objective of this study was to evaluate available literature on the possible efficacy of second-line treatments in HSV and the use of second-line treatments in HSV strains that are resistant to first-line treatments. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a final search was conducted in six databases on November 5, 2021 for all relevant literature using terms related to antiviral resistance, herpes, and HSV. Eligible manuscripts were required to report the presence of an existing or proposed second-line treatment for HSV-1, HSV-2, or varicella zoster virus (VZV); have full-text English-language access; and potentially reduce the rate of antiviral resistance. Following screening, 137 articles were included in qualitative synthesis. Of the included studies, articles that examined the relationship between viral resistance to first-line treatments and potential second-line treatments in HSV were included. The Cochrane risk-of-bias tool for randomized trials was used to assess risk of bias. Due to the heterogeneity of study designs, a meta-analysis of the studies was not performed. The dates in which accepted studies were published spanned from 2015-2021. In terms of sample characteristics, the majority (72.26%) of studies used Vero cells. When looking at the viruses on which the interventions were tested, the majority (84.67%) used HSV-1, with (34.31%) of these studies reporting testing on resistant HSV strains. Regarding the effectiveness of the proposed interventions, 91.97% were effective as potential managements for resistant strains of HSV. Of the papers reviewed, nectin in 2.19% of the reviews had efficacy as a second-line treatments in HSV, amenamevir in 2.19%, methanol extract in 2.19%, monoclonal antibodies in 1.46%, arbidol in 1.46%, siRNA swarms in 1.46%, Cucumis melo sulfated pectin in 1.46%, and components from Olea europeae in 1.46%. In addition to this griffithsin in 1.46% was effective, Morus alba L. in 1.46%, using nucleosides in 1.46%, botryosphaeran in 1.46%, monoterpenes in 1.46%, almond skin extracts in 1.46%, bortezomib in 1.46%, flavonoid compounds in 1.46%, andessential oils were effective in 1.46%, but not effective in 0.73%. The available literature reviewed consistently supports the existence and potentiality of second-line treatments for HSV strains that are resistant to first-line treatments. Immunocompromised patients have been noted to be the population most often affected by drug-resistant variants of HSV. Subsequently, we found that HSV infections in this patient population are challenging to manage clinically effectively. The goal of this systematic review is to provide additional information to patients on the potentiality of second-line treatment in HSV strains resistant to first-line treatments, especially those who are immunocompromised. All patients, whether they are immunocompromised or not, deserve to have their infections clinically managed in a manner supported by comprehensive research. This review provides necessary information about treatment options for patients with resistant HSV infections and their providers.

In Vitro Evaluation of Antiviral Activity Effect of Selenium, Bacillus clausii Supernatant, and Their Combination on the Replication of Herpes Simplex Virus 1

Background: About 70% of individuals worldwide suffer from herpes simplex virus 1 (HSV-1). Several studies have reported that selenium and supernatant of probiotic bacteria are antiviral; nevertheless, their effect alone or synergistically on HSV-1 is unknown. Objectives: The present study aimed to evaluate the antiviral effects of Bacillus clausii supernatant, selenium (Se), and their combination on HSV-1. Methods: After determining cytotoxicity by the MTT assay, selenium and B. clausii supernatants were added to HeLa cells 24 hours before (pre-infection treatment) and after (post-infection treatment) HSV-1 inoculation. After 47 hours of incubation at 37°C, the viral titer and expression levels of the unique long 47 (UL47) gene were determined by the 50% tissue culture infectious dose (TCID50) and real-time polymerase chain reaction methods, respectively. Results: The bacterial supernatant in dilutions of 1:4 and 1:8, selenium in concentrations of 0.5 and 1 μM, and a combination of them had a cytotoxicity level lower than 80% in HeLa cells. The HSV-1 titers in pre-infection and post-infection assays with a dilution of 1:4 supernatant decreased by about 2.16 and 1 log10 TCID50/mL, respectively. Moreover, 1 μM Se could reduce the virus titer by 2.33 log10 TCID50/mL. The virus titer showed a greater decrease when Se and the bacterial supernatants were combined than when only one of the two was used. The highest selectivity index (SI) was obtained when selenium and bacterial supernatant were combined (SI = 29.2). The combined use of 1 μM Se and a 1:4 dilution of B. clausii supernatant caused the greatest drop in virus titer (3.3 log10 TCID50/mL) in comparison to other treatment conditions. The UL47 gene expression was reduced by Se at concentrations of 0.5 and 1 μM by about 1.6- and 2-fold, respectively. The UL47 expression showed a higher decline when selenium and bacterial supernatant were combined than when only one of the two was employed, which is similar to viral titer data. Conclusions: Selenium and the supernatant of B. clausii have potent antiviral activity against HSV-1. The combination of selenium and the bacterial supernatant has a synergistic effect in reducing HSV-1 replication. However, further research is required to fully understand how they inhibit viruses.

Heterogeneity and viral replication fitness of HSV-1 clinical isolates with mutations in the thymidine kinase and DNA polymerase

BACKGROUND

Prolonged antiviral therapy in immunocompromised individuals can result in the emergence of (multi)drug-resistant herpes simplex virus 1 (HSV-1) infections, forming a therapeutic challenge.

OBJECTIVES

To evaluate spatial and temporal differences in drug resistance of HSV-1 samples from a HSCT recipient and to determine the effect of resistance mutations on viral replication fitness.

PATIENTS AND METHODS

Five HSV-1 isolates were recovered from a HSCT recipient who suffered from persistent HSV-1 lesions, consecutively treated with aciclovir, foscarnet, cidofovir and a combination of ganciclovir and cidofovir. Spatial and temporal differences in HSV-1 drug resistance were evaluated genotypically [Sanger sequencing and next-generation sequencing (NGS) of the viral thymidine kinase (TK) and DNA polymerase (DP)] and phenotypically (plaque reduction assay). Viral replication fitness was determined by dual infection competition assays.

RESULTS

Rapid evolution to aciclovir and foscarnet resistance was observed due to acquisition of TK (A189V and R222H) and DP (L778M and L802F) mutations. Virus isolates showed heterogeneous populations, spatial virus compartmentalization and minor viral variants in three out of five isolates (detectable by NGS but not by Sanger sequencing). Mutations in the TK and DP genes did not alter replication fitness without drug pressure. TK and/or DP mutants influenced replication fitness under antiviral pressure and showed increased fitness under pressure of the drug they showed resistance to.

CONCLUSIONS

The use of NGS and dual infection competition assays revealed rapid evolution of HSV-1 drug resistance in a HSCT recipient with spatial and temporal compartmentalization of viral variants that had altered replication fitness under antiviral pressure.

Acyclovir-Resistant Herpes Simplex Virus 1 Keratitis: A Concerning and Emerging Clinical Challenge

PURPOSE

To describe the clinical and virological profiles of patients with herpes simplex keratitis (HSK) caused by acyclovir-resistant (ACV^R) strains of herpes simplex virus 1 (HSV-1).

DESIGN

Multicenter retrospective case series.

METHODS

HSV-1 resistance to ACV was confirmed using sequencing of genes encoding HSV-1 thymidine kinase (TK) and DNA polymerase (DNA pol). Data were collected on the number of HSK episodes before and after the diagnosis of resistance, ocular findings including the type of HSK, immune status of patients, antiviral treatments, and HSV-1 genotypic resistance profiles.

RESULTS

This study evaluated 18 HSK patients (13 male and 5 female, aged 66.8 ± 4.7 years) with ACV^R HSV-1-positive ocular samples. Genotypic resistance testing was performed because of frequent recurrences despite adequate antiviral prophylaxis (AVP) (n = 13, 72%), or poor response to suppressive antiviral therapy (n = 5, 28%). Resistance mutations were found in the TK (n = 15, 83%) or in the DNA pol gene (n = 3, 17%). Prior to the diagnosis of resistance, the duration of disease was 29.8 ± 20.4 years, with more than 10 HSK recurrences in 15 patients (83%). The number of recurrences between the first episode and the diagnosis of resistance was significantly lower in immunocompromised patients (n = 6, 33%) than in immunocompetent patients (n = 12; 67%) (11.5 ± 4.9 vs 16.4 ± 1.9, P = .05).

CONCLUSION

HSV-1 resistance to ACV must be suspected in HSK patients with recurrences despite AVP and/or in cases that respond poorly to a suppressive antiviral regimen. Immunocompromised patients and/or those with longstanding disease may be particularly at risk for developing resistance.

Characteristics of Helicase-primase Inhibitor Amenamevir-resistant Herpes Simplex Virus

The antiherpetic drug amenamevir (AMNV) inhibits the helicase-primase complex of herpes simplex virus type 1 (HSV-1), HSV-2 and varicella-zoster virus directly as well as inhibiting the replication of these viruses. Although several mutated HSV viruses resistant to helicase-primase inhibitors have been reported, the mutations contributing to the resistance remain unclear as recombinant viruses containing a single mutation have not been analyzed. We obtained AMNV-resistant viruses with amino acid substitutions by several passages under AMNV-treatment. Twenty HSV-1 and 19 HSV-2 mutants with mutation(s) in UL5 helicase and/or UL52 primase, but not in co-factor UL8, were isolated. The mutations in UL5 were located downstream of motif IV, with UL5 K356N in HSV-1 and K355N in HSV-2, in particular, identified as having the highest frequency: 9/20 and 9/19, respectively. We generated recombinant AMNV-resistant HSV-1 with a single amino acid substitution using BAC mutagenesis. As a result, G352C in UL5 helicase and F360C/V and N902T in UL52 primase were identified as novel mutations. The virus with K356N in UL5 showed 10-fold higher AMNV resistance than did other mutants, and showed equivalent viral growth in vitro and virulence in vivo as the parent HSV-1, although other mutants showed attenuated virulence. All recombinant viruses were susceptible to the other antiherpetic drugs, acyclovir and foscarnet. In conclusion, based on BAC mutagenesis, this study identified for the first time mutations in UL5 and UL52 that contributed to AMNV resistance, and found that a mutant with the most frequent K356N mutation in HSV-1 maintained viral growth and virulence equivalent to the parent virus.

Antiviral Drugs Against Herpesviruses

The discovery of the nucleoside analogue, acyclovir, represented a milestone in the management of infections caused by herpes simplex virus and varicella-zoster virus. Ganciclovir, another nucleoside analogue, was then used for the management of systemic and organ-specific human cytomegalovirus diseases. The pyrophosphate analogue, foscarnet, and the nucleotide analogue, cidofovir, have been approved subsequently and constitute the second-line antiviral drugs. However, the viral DNA polymerase is the ultimate target of all these antiviral agents with a possible emergence of cross-resistance between these drugs. Recently, letermovir that targets the viral terminase complex was approved for the prophylaxis of human cytomegalovirus infections in hematopoietic stem cell transplant recipients. Other viral targets such as the protein kinase and the helicase-primase complex are also evaluated for the development of novel potent inhibitors against herpesviruses.