Fluorescent octahydrophenazines as novel inhibitors against herpes simplex viruses

A new series of racemic fluorescent octahydrophenazines (rac-PZ1-11) have been designed and synthesized via the efficient nucleophilic aromatic substitution (SNAr) of tetrafluorobenzenedinitriles (1a-c) and racemic cyclohexane-1,2-diamines (rac-2a and b). The bioactivities of these racemic rac-PZs (20 μM) against herpes simplex virus type-1 (HSV-1) were evaluated by the relative cell viability of Vero cells infected with HSV-1. It was found that rac-PZ3 shows much higher anti-HSV-1 activity than others, with EC50 = 9.2 ± 1.4 μM. Further investigation into the anti-HSV activities of rac-PZ3 and its enantiomers RR- and SS-PZ3 indicates that rac-PZ3 can also efficiently inhibit HSV-2 and even ACV-resistant HSV-2 (EC50 = 11.0 ± 2.3 and 14.9 ± 2.8 μM, respectively), SS-PZ3 has better activities against HSV-1, HSV-2 and ACV-resistant HSV-2 (EC50 = 4.1 ± 1.1, 5.8 ± 1.0 and 7.9 ± 1.2 μM, respectively), but RR-PZ3 has almost no antiviral activities. The primary mechanism study indicates that rac-PZ3 efficiently reverses the HSV-1/2-induced cytopathic effect and suppresses the expression of viral mRNA and proteins. In addition, rac-, RR- and SS-PZ3 possess excellent fluorescence properties with almost the same emission wavelength and high fluorescence quantum yields (ΦF = 90.3-92.3 % in cyclohexane solutions and 54.4-57.3 % in solids) and can target endoplasmic reticulum and cell membrane. The efficient anti-HSV bioactivities and excellent fluorescence of PZ3 prove its potential applications in antiviral therapy and biological imaging.

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.

Oncolytic varicella-zoster virus engineered with ORF8 deletion and armed with drug-controllable interleukin-12

BACKGROUND

The varicella-zoster virus (VZV), belonging to the group of human α-herpesviruses, has yet to be developed as a platform for oncolytic virotherapy, despite indications from clinical case reports suggesting a potential association between VZV infection and cancer remission.

METHODS

Here, we constructed oncolytic VZV candidates based on the vaccine strain vOka and the laboratory strain Ellen. These newly engineered viruses were subsequently assessed for their oncolytic properties in the human MeWo melanoma xenograft model and the mouse B16-F10-nectin1 melanoma syngeneic model.

RESULTS

In the MeWo xenograft model, both vOka and Ellen exhibited potent antitumor efficacy. However, it was observed that introducing a hyperfusogenic mutation into glycoprotein B led to a reduction in VZV's effectiveness. Notably, the deletion of ORF8 (encodes viral deoxyuridine triphosphatase) attenuated the replication of VZV both in vitro and in vivo, but it did not compromise VZV's oncolytic potency. We further armed the VZV Ellen-ΔORF8 vector with a tet-off controlled mouse single-chain IL12 (scIL12) gene cassette. This augmented virus was validated for its oncolytic activity and triggered systemic antitumor immune responses in the immunocompetent B16-F10-nectin1 model.

CONCLUSIONS

These findings highlight the potential of using Ellen-ΔORF8-tet-off-scIL12 as a novel VZV-based oncolytic virotherapy.

Virucidal effect of mouthwash on acyclovir-resistant herpes simplex virus

OBJECTIVES

The symptoms of herpes simplex viruses type 1 (HSV-1) infections might be severe and persistent in immunocompromised patients in whom they reactivate at a high frequency. The development of Acyclovir (ACV) resistant strains due to long-term treatment with antiviral agents in those patients is not uncommon. The aim of the present study was to assess the virucidal effect of commercially available mouthwashes against ACV-resistant HSV-1 strains.

MATERIALS AND METHODS

Two acyclovir-resistant HSV-1 strains were exposed for 30 s to essential oil-based (Listerine Fresh Burst® and Listerine Zero®), chlorhexidine gluconate 0.2% (Hexidyl®) and povidone-iodine 7.5% (Betadine Gargle®) mouthwashes. Loss of virus infectivity was determined by means of plaque reduction assays in a cell culture system.

RESULTS

All 4 of the tested solutions significantly reduced virus infectivity, with the essential oil-based and povidone-iodine mouthwashes being slightly more efficacious, compared to chlorhexidine.

CONCLUSION

The findings of this analysis revealed that the tested oral rinses demonstrated in-vitro antiviral activity against ACV-resistant HSV. Comparative clinical trials are required to establish the clinical effectiveness of daily use of oral rinses in reducing the appearance of oral HSV lesions in immunocompromised patients.

Variant Analysis of the Thymidine Kinase and DNA Polymerase Genes of Herpes Simplex Virus in Korea: Frequency of Acyclovir Resistance Mutations

The thymidine kinase (TK) and DNA polymerase (pol) genes of the herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2) are two important genes involved in antiviral resistance. We investigated the genetic polymorphisms of the HSV-TK and pol genes in clinical isolates from Korean HSV-infected patients using next-generation sequencing (NGS) for the first time in Korea. A total of 81 HSV-1 and 47 HSV-2 isolates were examined. NGS was used to amplify and sequence the TK and pol genes. Among the 81 HSV-1 isolates, 12 and 17 natural polymorphisms and 9 and 23 polymorphisms of unknown significance in TK and pol were found, respectively. Two HSV-1 isolates (2.5%) exhibited the E257K amino acid substitution in TK, associated with antiviral resistance. Out of 47 HSV-2 isolates, 8 natural polymorphisms were identified in TK, and 9 in pol, with 13 polymorphisms of unknown significance in TK and 10 in pol. No known resistance-related mutations were observed in HSV-2. These findings contribute to our understanding of the genetic variants associated with antiviral resistance in HSV-1 and HSV-2 in Korea, with frequencies of known antiviral resistance-related mutations of 2.5% and 0% in HSV-1 and HSV-2, respectively.

Salvage Treatment of Refractory HSV Oral Lesions with Pritelivir in Allogeneic Hematopoietic Cell Transplant Recipients

We present two allogeneic hematopoietic cell transplantation recipients (HCTr) treated with pritelivir for acyclovir-resistant/refractory (r/r) HSV infection based on the expanded access program of the pritelivir manufacturer. Outpatient treatment with pritelivir was administered, with partial response by week 1 of treatment and complete response by week 4 of treatment in both patients. No adverse events were noted. Pritelivir appears to be an effective and safe option for the management of acyclovir-r/r HSV infections in highly immunocompromised patients in an outpatient setting.

Antiviral activity of amide-appended α-hydroxytropolones against herpes simplex virus-1 and -2

α-Hydroxytropolones (αHTs) have potent antiviral activity against herpes simplex virus-1 and -2 (HSV-1 and HSV-2) in cell culture, including against acyclovir-resistant mutants, and as a result have the potential to be developed as antiviral drugs targeting these viruses. We recently described a convenient final-step amidation strategy to their synthesis, and this was used to generate 57 amide-substituted αHTs that were tested against hepatitis B virus. The following manuscript describes the evaluation of this library against HSV-1, as well as a subset against HSV-2. The structure-function analysis obtained from these studies demonstrates the importance of lipophilicity and rigidity to αHT-based anti-HSV potency, consistent with our prior work on smaller libraries. We used this information to synthesize and test a targeted library of 4 additional amide-appended αHTs. The most potent of this new series had a 50% effective concentration (EC₅₀) for viral inhibition of 72 nM, on par with the most potent αHT antivirals we have found to date. Given the ease of synthesis of amide-appended αHTs, this new class of antiviral compounds and the chemistry to make them should be highly valuable in future anti-HSV drug development.

[Scientific legacy of Professor A.A. Kasparov. Inductor of endogenous interferon Poludan in the treatment of ocular herpes and other corneal diseases]

This article presents a retrospective analysis of the research findings by professor A.A. Kasparov, who developed and implemented a novel approach to treating ocular herpes. The treatment system is fundamentally different from the conventional chemotherapeutic approach and revolves around non-specific immunotherapy using an endogenous interferon inducer - a biosynthetic complex of polyriboadenylic and polyribouridylic acids, known as Poludan. This approach also incorporates personalized cell therapy based on Poludan, along with herpes vaccine aimed at preventing recurrence. The regenerative and antiviral properties of this approach have proven successful in treating other corneal conditions such as adenovirus infections, early postoperative bullous keratopathy, as well as in stimulation of epithelialization after refractive surgeries (photorefractive keratectomy, phototherapeutic keratectomy).

[Resistance to antiviral drugs in human viruses from the subfamily Betaherpesvirinae]

The review provides information on the mechanisms of the emergence of resistance to antiviral drugs in human viruses from the subfamily Betaherpesvirinae. Data on the principles of action of antiviral drugs and their characteristics are given. The occurrence rates of viral resistance in various groups of patients is described and information about the possible consequences of the emergence of resistance to antiviral drugs is given. Information is provided regarding the virus genes in which mutations occur that lead to viral resistance, and a list of such mutations that have described so far is given. The significance of the study of mutations leading to the resistance of the virus to antiviral drugs for medical practice is discussed.

Decentralized systems for the treatment of antimicrobial compounds released from hospital aquatic wastes

In many developing countries, untreated hospital effluents are discharged and treated simultaneously with municipal wastewater. However, if the hospital effluents are not treated separately, they pose concerning health risks due to the possible transport of the antimicrobial genes and microbes in the environment. Such effluent is considered as a point source for a number of potentially infectious microorganisms, waste antimicrobial compounds and other contaminants that could promote antimicrobial resistance development. The removal of these contaminants prior to discharge reduces the exposure of antimicrobials to the environment and this should lower the risk of superbug development. At an effluent discharge site, suitable pre-treatment of wastewater containing antimicrobials could maximise the ecological impact with potentially reduced risk to human health. In addressing these points, this paper reviews the applications of decentralized treatment systems toward reducing the concentration of antimicrobials in wastewater. The most commonly used techniques in decentralized wastewater treatment systems for onsite removal of antimicrobials were discussed and evidence suggests that hybrid techniques should be more useful for the efficient removal of antimicrobials. It is concluded that alongside the cooperation of administration departments, health industries, water treatment authorities and general public, decentralized treatment technology can efficiently enhance the removal of antimicrobial compounds, thereby decreasing the concentration of contaminants released to the environment that could pose risks to human and ecological health due to development of antimicrobial resistance in microbes.

Ion channels and ions as therapeutic targets and strategies for herpes simplex virus infection

Herpes simplex virus (HSV) is a highly contagious virus that cannot be completely cured currently. Existing treatment methods are mainly nucleoside antiviral drugs, and the emergence of drug-resistant strains severely limits their use. There is an urgent need to discover antiviral drugs that act on new targets. Ion channels, a class of cellular proteins with a wide range of functions, have become critical host factors for a wide variety of viral infections. Ion channel blockers have been shown to have antiviral activity. In this study, we discuss the role of ion channels and ions in the HSV life cycle, and the potential of targeting ion channels as a novel, pharmacologically safe and wide-range antiviral treatment option.

Disrupting autorepression circuitry generates "open-loop lethality" to yield escape-resistant antiviral agents

Across biological scales, gene-regulatory networks employ autorepression (negative feedback) to maintain homeostasis and minimize failure from aberrant expression. Here, we present a proof of concept that disrupting transcriptional negative feedback dysregulates viral gene expression to therapeutically inhibit replication and confers a high evolutionary barrier to resistance. We find that nucleic-acid decoys mimicking cis-regulatory sites act as "feedback disruptors," break homeostasis, and increase viral transcription factors to cytotoxic levels (termed "open-loop lethality"). Feedback disruptors against herpesviruses reduced viral replication >2-logs without activating innate immunity, showed sub-nM IC50, synergized with standard-of-care antivirals, and inhibited virus replication in mice. In contrast to approved antivirals where resistance rapidly emerged, no feedback-disruptor escape mutants evolved in long-term cultures. For SARS-CoV-2, disruption of a putative feedback circuit also generated open-loop lethality, reducing viral titers by >1-log. These results demonstrate that generating open-loop lethality, via negative-feedback disruption, may yield a class of antimicrobials with a high genetic barrier to resistance.

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.

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.

DNA polymerases of herpesviruses and their inhibitors

Human herpesviruses are large double-stranded DNA viruses belonging to the Herpesviridae family. The main characteristics of these viruses are their ability to establish a lifelong latency into the host with a potential to reactivate periodically. Primary infections and reactivations with herpesviruses are responsible for a large spectrum of diseases and may result in severe complications in immunocompromised patients. The viral DNA polymerase is a key enzyme in the replicative cycle of herpesviruses, and the target of most antiviral agents (i.e., nucleoside, nucleotide and pyrophosphate analogs). However, long-term prophylaxis and treatment with these antivirals may lead to the emergence of drug-resistant isolates harboring mutations in genes encoding viral enzymes that phosphorylate drugs (nucleoside analogs) and/or DNA polymerases, with potential cross-resistance between the different analogs. Drug resistance mutations mainly arise in conserved regions of the polymerase and exonuclease functional domains of these enzymes. In the polymerase domain, mutations associated with resistance to nucleoside/nucleotide analogs may directly or indirectly affect drug binding or incorporation into the primer strand, or increase the rate of extension of DNA to overcome chain termination. In the exonuclease domain, mutations conferring resistance to nucleoside/nucleotide analogs may reduce the rate of excision of incorporated drug, or continue DNA elongation after drug incorporation without excision. Mutations associated with resistance to pyrophosphate analogs may alter drug binding or the conformational changes of the polymerase domain required for an efficient activity of the enzyme. Novel herpesvirus inhibitors with a potent antiviral activity against drug-resistant isolates are thus needed urgently.

6-Thioguanine Inhibits Herpes Simplex Virus 1 Infection of Eyes

Herpes simplex virus 1 (HSV-1) infects eye corneal tissues leading to herpetic stromal keratitis (HSK), which is one of the leading causes of blindness. Here in our study, we found that 6-thioguanine (6-TG), a once clinically approved medication for child acute myelogenous leukemia, inhibited multiple strains of HSV-1 infection in vitro and in vivo. 6-TG is more potent than acyclovir (ACV) and ganciclovir (GCV), with the 50% inhibitory concentration (IC₅₀) of 6-TG at 0.104 μM with high stimulation index (SI) (SI = 6,475.48) compared to the IC₅₀ of ACV at 1.253 μM and the IC₅₀ of GCV at 1.257 μM. In addition, 6-TG at 500 μM topically applied to the eyes with HSV-1 infection significantly inhibits HSV-1 replication, alleviates virus-induced HSK pathogenesis, and improves eye conditions. More importantly, 6-TG is effective against ACV-resistant HSV-1 strains, including HSV-1/153 and HSV-1/blue. Knockdown of Rac1 with small interfering RNA (siRNA) negatively affected HSV-1 replication, suggesting that Rac1 facilitated HSV-1 replication. Following HSV-1 infection of human corneal epithelial cells (HCECs), endogenous Rac1 activity was upregulated by glutathione S-transferase (GST) pulldown assay. We further found that Rac1 was highly expressed in the corneal tissue of HSK patients compared to normal individuals. Mechanistic study showed that 6-TG inhibited HSV-1 replication by targeting Rac1 activity in HSV-1 infected cells, and the Rac1 is critical in the pathogenesis of HSK. Our results indicated that 6-TG is a promising therapeutic molecule for the treatment of HSK.

IMPORTANCE We reported the discovery of 6-TG inhibition of HSV-1 infection and its inhibitory roles in HSK both in vitro and in vivo. 6-TG was shown to possess at least 10× more potent inhibitory activity against HSV-1 than ACV and GCV and, more importantly, inhibit ACV/GCV-resistant mutant viruses. Animal model studies showed that gel-formulated 6-TG topically applied to eyes locally infected with HSV-1 could significantly inhibit HSV-1 replication, alleviate virus-induced HSK pathogenesis, and improve eye conditions. Further study showed that HSV-1 infection upregulated Rac1 expression, and knockdown of Rac1 using siRNA markedly restricted HSV-1 replication, suggesting that Rac1 is required for HSV-1 replication. In addition, we also documented that Rac1 is highly expressed in corneal tissues from HSK patients, indicating that Rac1 is associated with HSK pathogenesis. In view of the high potency of 6-TG, low cytotoxicity, targeting a distinct therapeutic target, we suggest that 6-TG is a potential candidate for development as a therapeutic agent for HSK therapy.

Antiviral Effect of Nonfunctionalized Gold Nanoparticles against Herpes Simplex Virus Type-1 (HSV-1) and Possible Contribution of Near-Field Interaction Mechanism

The antiviral activity of nonfunctionalized gold nanoparticles (AuNPs) against herpes simplex virus type-1 (HSV-1) in vitro was revealed in this study. We found that AuNPs are capable of reducing the cytopathic effect (CPE) of HSV-1 in Vero cells in a dose- and time-dependent manner when used in pretreatment mode. The demonstrated antiviral activity was within the nontoxic concentration range of AuNPs. Interestingly, we noted that nanoparticles with smaller sizes reduced the CPE of HSV-1 more effectively than larger ones. The observed phenomenon can be tentatively explained by the near-field action of nanoparticles at the virus envelope. These results show that AuNPs can be considered as potential candidates for the treatment of HSV-1 infections.

Harringtonine Inhibits Herpes Simplex Virus Type 1 Infection by Reducing Herpes Virus Entry Mediator Expression

Herpes simplex virus type 1 (HSV-1) infection induces various clinical disorders, such as herpes simplex encephalitis (HSE), herpes simplex keratitis (HSK), and genital herpes. In clinical intervention, acyclovir (ACV) is the major therapeutic drug used to suppress HSV-1; however, ACV-resistant strains have gradually increased. In the present study, harringtonine (HT) significantly inhibited infection of HSV-1 as well as two ACV-resistant strains, including HSV-1 blue and HSV-1 153. Time-of-drug addition assay further revealed that HT mainly reduced the early stage of HSV-1 infection. We also demonstrated that HT mainly affected herpes virus entry mediator (HVEM) expression as shown by qPCR, Western Blot, and Immunofluorescence. Collectively, HT showed antiviral activity against HSV-1 and ACV-resistant strains by targeting HVEM and could be a promising therapeutic candidate for mitigating HSV-1-induced-pathogenesis.

Characterisation of Antiviral Activity of Cathelicidins from Naked Mole Rat and Python bivittatus on Human Herpes Simplex Virus 1

Hg-CATH and Pb-CATH4 are cathelicidins from Heterocephalus glaber and Python bivittatus that have been previously identified as potent antibacterial peptides. However, their antiviral properties were not previously investigated. In this study, their activity against the herpes simplex virus (HSV)-1 was evaluated during primary human keratinocyte infection. Both of them significantly reduced HSV-1 DNA replication and production of infectious viral particles in keratinocytes at noncytotoxic concentrations, with the stronger activity of Pb-CATH4. These peptides did not show direct virucidal activity and did not exhibit significant immunomodulatory properties, except for Pb-CATH4, which exerted a moderate proinflammatory action. All in all, our results suggest that Hg-CATH and Pb-CATH4 could be potent candidates for the development of new therapies against HSV-1.

Prophylactic treatment with BX795 blocks activation of AKT and its downstream targets to protect vaginal keratinocytes and vaginal epithelium from HSV-2 infection

Genital herpes infections in humans are usually caused by herpes simplex virus type-2 (HSV-2), which result in recurrent lesions in the anogenital region. Past studies have shown that a viral protein translation inhibitor, BX795 is capable of mitigating HSV-2 infection both in vitro and in vivo when dosed therapeutically. However, any preventative benefits of this compound against HSV-2 infection remain poorly understood. In this study, we show that BX795 when added prophylactically to human vaginal keratinocytes generates strong preventative effects against a future HSV-2 infection. As a possible mechanism for this action, we found that BX795 efficiently reduces phosphorylation of AKT and its downstream targets p70S6K and 4EBP1. Our in-silico protein docking studies support our immunoblotting results and provide further credence to the proposed mechanism. Using a murine model of vaginal infection, we show that prior treatment with BX795 is also protective in vivo and leads to lower viral replication in the vaginal tissue.

Impact of Amino Acid Substitutions in Region II and Helix K of Herpes Simplex Virus 1 and Human Cytomegalovirus DNA Polymerases on Resistance to Foscarnet

Amino acid substitutions conferring resistance of herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV) to foscarnet (PFA) are located in the genes UL30 and UL54, respectively, encoding the DNA polymerase (pol). In this study, we analyzed the impact of substitutions located in helix K and region II that are involved in the conformational changes of the DNA pol. Theoretical substitutions were identified by sequences alignment of the helix K and region II of human herpesviruses (susceptible to PFA) and bacteriophages (resistant to PFA) and introduced in viral genomes by recombinant phenotyping. We characterized the susceptibility of HSV-1 and HCMV mutants to PFA. In UL30, the substitutions I619K (helix K), V715S, and A719T (both in region II) increased mean PFA 50% effective concentrations (EC₅₀s) by 2.5-, 5.6-, and 2.0-fold, respectively, compared to the wild type (WT). In UL54, the substitution Q579I (helix K) conferred hypersusceptibility to PFA (0.17-fold change), whereas the substitutions Q697P, V715S, and A719T (all in region II) increased mean PFA EC₅₀s by 3.8-, 2.8- and 2.5-fold, respectively, compared to the WT. These results were confirmed by enzymatic assays using recombinant DNA pol harboring these substitutions. Three-dimensional modeling suggests that substitutions conferring resistance/hypersusceptibility to PFA located in helix K and region II of UL30 and UL54 DNA pol favor an open/closed conformation of these enzymes, resulting in a lower/higher drug affinity for the proteins. Thus, this study shows that both regions of UL30 and UL54 DNA pol are involved in the conformational changes of these proteins and can influence the susceptibility of both viruses to PFA.

Sumoylation of the Carboxy-Terminal of Human Cytomegalovirus DNA Polymerase Processivity Factor UL44 Attenuates Viral DNA Replication

Controlled regulation of genomic DNA synthesis is a universally conserved process for all herpesviruses, including human cytomegalovirus (HCMV), and plays a key role in viral pathogenesis, such as persistent infections. HCMV DNA polymerase processivity factor UL44 plays an essential role in viral DNA replication. To better understand the biology of UL44, we performed a yeast two-hybrid screen for host proteins that could interact with UL44. The most frequently isolated result was the SUMO-conjugating enzyme UBC9, a protein involved in the sumoylation pathway. The UBC9-UL44 interaction was confirmed by in vitro His-tag pull-down and in vivo co-immunoprecipitation assays. Using deletion mutants of UL44, we mapped two small regions of UL44, aa 11–16, and 260–269, which might be critical for the interaction with UBC9. We then demonstrated that UL44 was a target for sumoylation by in vitro and in vivo sumoylation assays, as well as in HCMV-infected cells. We further confirmed that ⁴¹⁰lysine located within a ψKxE consensus motif on UL44 carboxy-terminal was the major sumoylation site of UL44. Interestingly, although ⁴¹⁰lysine had no effects on subcellular localization or protein stability of UL44, the removal of ⁴¹⁰lysine sumoylation site enhanced both viral DNA synthesis in transfection-replication assays and viral progeny production in infected cells for HCMV, suggesting sumoylation can attenuate HCMV replication through targeting UL44. Our results suggest that sumoylation plays a key role in regulating UL44 functions and viral replication, and reveal the crucial role of the carboxy-terminal of UL44, for which little function has been known before.

Advances and Perspectives in the Management of Varicella-Zoster Virus Infections

Varicella-zoster virus (VZV), a common and ubiquitous human-restricted pathogen, causes a primary infection (varicella or chickenpox) followed by establishment of latency in sensory ganglia. The virus can reactivate, causing herpes zoster (HZ, shingles) and leading to significant morbidity but rarely mortality, although in immunocompromised hosts, VZV can cause severe disseminated and occasionally fatal disease. We discuss VZV diseases and the decrease in their incidence due to the introduction of live-attenuated vaccines to prevent varicella or HZ. We also focus on acyclovir, valacyclovir, and famciclovir (FDA approved drugs to treat VZV infections), brivudine (used in some European countries) and amenamevir (a helicase-primase inhibitor, approved in Japan) that augur the beginning of a new era of anti-VZV therapy. Valnivudine hydrochloride (FV-100) and valomaciclovir stearate (in advanced stage of development) and several new molecules potentially good as anti-VZV candidates described during the last year are examined. We reflect on the role of antiviral agents in the treatment of VZV-associated diseases, as a large percentage of the at-risk population is not immunized, and on the limitations of currently FDA-approved anti-VZV drugs. Their low efficacy in controlling HZ pain and post-herpetic neuralgia development, and the need of multiple dosing regimens requiring daily dose adaptation for patients with renal failure urges the development of novel anti-VZV drugs.

Differential impact of various substitutions at codon 715 in region II of HSV-1 and HCMV DNA polymerases

This study aimed at understanding the impact of different substitutions at codon 715 localized in the region II of the palm domain of herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV) DNA polymerases (pol). Here, we report a new theoretical mutation V715S that confers resistance of HSV-1 to foscarnet/acyclovir (5.6- and 9.2-fold increases EC₅₀ values compared to wild type, respectively) and of HCMV to foscarnet/ganciclovir (2.8- and 2.9-fold increases in EC₅₀ values compared to wild type, respectively). To further analyze the importance of this amino acid, we investigated the impact of the already known mutations V715M and V715G on the replicative capacities and drug susceptibilities of both viruses as well as on the activity and drug inhibition of the DNA pol. The V715G recombinant HSV-1 mutant was resistant to foscarnet and acyclovir (3.4- and 4.6-fold EC₅₀ increase, respectively) whereas the V715M mutant was susceptible to foscarnet and resistant to acyclovir (3.4-fold EC₅₀ increase). The V715G recombinant HCMV mutant did not grow and the V715M mutant was resistant to foscarnet (3.7-fold EC₅₀ increase) and susceptible to ganciclovir. Finally, we showed by three-dimensional modeling that the differential impact of these mutations on the viral replicative capacity and drug resistance profile was related to different hydrophobic local environments for V715 in the DNA pol of the two viruses. Furthermore, we hypothesize that the DNA pol of HSV-1 is more tolerant to changes at this residue compared to that of HCMV because of a more hydrophobic environment stabilizing the region.

Efficient establishment of reactivatable latency by an acyclovir-resistant herpes simplex virus 1 thymidine kinase substitution mutant with reduced neuronal replication

Herpes simplex virus 1 causes recurrent diseases by reactivating from latency, which requires the viral thymidine kinase (TK) gene. An acyclovir-resistant mutation in TK, V204G, was previously repeatedly identified in a patient with recurrent herpetic keratitis. We found that compared with its parental strain KOS, a laboratory-derived V204G mutant virus was impaired in replication in cultured neurons despite little defect in non-neuronal cells. After corneal inoculation of mice, V204G exhibited defects in ocular replication that were modest over the first three days but severe afterward. Acute replication of V204G in trigeminal ganglia was significantly impaired. However, V204G established latency with viral loads as high as KOS and reactivated with high frequency albeit reduced kinetics. Acyclovir treatment that drastically decreased ocular and ganglionic replication of KOS had little effect on V204G. Thus, despite reduced neuronal replication due to impaired TK activity, this clinically relevant drug-resistant mutant can efficiently establish reactivatable latency.

Eczema Herpeticum: Clinical and Pathophysiological Aspects

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease in the world. AD is a complex pathology mainly characterized by an impaired skin barrier, immune response dysfunction, and unbalanced skin microbiota. Moreover, AD patients exhibit an increased risk of developing bacterial and viral infections. One of the most current, and potentially life-threatening, viral infection is caused by herpes simplex virus (HSV), which occurs in about 3% of AD patients under the name of eczema herpeticum (EH). Following a first part dedicated to the clinical features, virological diagnosis, and current treatments of EH, this review will focus on the description of the pathophysiology and, more particularly, the presently known predisposing factors to herpetic complications in AD patients. These factors include those related to impairment of the skin barrier such as deficit in filaggrin and anomalies in tight and adherens junctions. In addition, low production of the antimicrobial peptides cathelicidin LL-37 and human β-defensins; overexpression of cytokines such as interleukin (IL)-4, IL-13, IL-25, IL-33, and thymic stromal lymphopoietin (TSLP); or downregulation of type I to III interferons as well as defect in functions of immune cells such as dendritic, natural killer, and regulatory T cells have been involved. Otherwise, genetic polymorphisms and AD topical calcineurin inhibitor treatments have been associated with an increased risk of EH. Finally, dysbiosis of skin microbiota characterized in AD patients by Staphylococcus aureus colonization and toxin secretion, such as α-toxin, has been described as promoting HSV replication and could therefore contribute to EH.

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.

Herpes Simplex Virus-Related Conjunctivitis Resistant to Aciclovir: A Case Report and Review of the Literature

PURPOSE

To report a rare case of herpes virus type 2-related conjunctivitis, resistant to aciclovir (ACV).

METHODS

Case report and review of literature.

RESULTS

A 28-year-old human immunodeficiency virus-positive man presented with chronic, recurrent follicular conjunctivitis. Multiplex reverse transcription polymerase chain reaction assay testing was positive for herpes simplex virus (HSV); subsequent typing with HSV assay revealed the presence of HSV type 2. Oral ACV failed to control the disease, and the patient continued to worsen clinically until resistance testing was performed. This revealed an M183stop within thymidine kinase, thus confirming the suspected resistance. The patient improved after 14 days of high-dose continuous intravenous infusion of ACV.

CONCLUSIONS

This is a rare case of isolated conjunctivitis due to herpes virus type 2, in an human immunodeficiency virus-positive patient, which was found to be resistant to ACV. Drug-resistant HSV is likely to emerge as an important clinical entity in the future, increasing the need for new drugs with novel mechanisms of action.

Antiviral mechanism of carvacrol on HSV-2 infectivity through inhibition of RIP3-mediated programmed cell necrosis pathway and ubiquitin-proteasome system in BSC-1 cells

BACKGROUND

Carvacrol, as the major components of aromatic plants used for treating human skin diseases including origanum, Satureja, thymus, and coridothymus species, presented a kind of antiviral activity. To explore the mechanisms of carvacrol against herpes simplex virus (HSV) in vitro.

METHOD

The BSC-1 cells model of HSV infection was established, and from the two aspects of viral replication level and cell death pathway, the antiviral effects of carvacrol on HSV infected cells were also evaluated by plaque assay under the three modes including prevention, treatment, and direct inactivation.

RESULTS

In the three ways, the half-maximal effective concentration (EC50) of 2% true carvacrol solution on HSV-2 infected cells were severally 0.43, 0.19 and 0.51 mmol/L, and the corresponding therapeutic index (TI) were 4.02, 9.11 and 3.39, respectively. It's the opposite of the increased levels caused by HSV-2 infection, that both the expressions at the transcription genes and protein levels of virus own replication key factors (including ICP4, ICP27, VP16, gB, and UL30) and cytokines (including RIP3, TNF-α, and MLKL) of infected cells treated with carvacrol were dose-dependently inhibited. Besides, HSV-2 infection can cause the decrease of intracellular protein ubiquitination level, and carvacrol can reverse the ubiquitination decrease level caused by HSV-2 infection.

CONCLUSION

Carvacrol exhibits significant antiviral activity by inhibiting the HSV-2 proliferation process and HSV-2-induced TNF-α increasing levels, decreasing RIP3 and MLKL protein expressions through the intracellular RIP3-mediated programmed cell necrosis pathway. In addition, carvacrol also may exhibit anti-HSV-2 activity by reversing the ubiquitination decrease level caused by HSV-2 infection on the ubiquitin-proteasome system, which provides insights into the molecular mechanism.

Retrospective case analysis of antiviral therapies for HHV-6 encephalitis after hematopoietic stem cell transplantation

Human herpesvirus 6 (HHV-6) is one of the most common causes of encephalitis in allogeneic hematopoietic stem cell transplant (HCT) recipients and is associated with significant morbidity and mortality. There are no FDA-approved treatments specifically for HHV-6 encephalitis; HHV-6 disease is typically treated with CMV antivirals. A review of antiviral medications used to treat HHV-6 encephalitis was conducted by aggregating data from case reports found on PubMed. Articles were included if they examined at least one HCT patient diagnosed with HHV-6 encephalitis and described their treatment course and outcome. Key data were abstracted from 123 cases described in 52 studies. The proportion of patients with encephalitis who died or developed sequelae was 63.6% among ganciclovir monotherapy recipients (n = 44), 55.3% among foscarnet monotherapy recipients (n = 47), and 37.5% among recipients of combination therapy with foscarnet and ganciclovir (n = 32). Logistic regression revealed that recipients of foscarnet (OR 4.286, 95% CI 1.235-14.877, P = .022) and ganciclovir (OR 5.625, 95% CI 1.584-19.975, P = .008) monotherapies were more likely to develop sequelae compared to recipients of combination therapy, respectively. In multivariate analyses, non-cord blood transplant was identified as an independent risk factor for developing sequelae after receiving ganciclovir monotherapy (OR 5.999, 95% CI 1.274-28.254, P = .023). There was no difference in mortality between patients who received combination therapy and those who received monotherapy. In conclusion, combination therapy with foscarnet and ganciclovir may reduce sequelae, but not mortality, secondary to HHV-6 encephalitis.

Antiviral drugs in aquatic environment and wastewater treatment plants: A review on occurrence, fate, removal and ecotoxicity

The environmental release of antiviral drugs is of considerable concern due to potential ecosystem alterations and the development of antiviral resistance. As a result, interest on their occurrence and fate in natural and engineered systems has grown substantially in recent years. The main scope of this review is to fill the void of information on the knowledge on the worldwide occurrence of antiviral drugs in wastewaters and natural waters and correlate their levels with their environmental fate. According to the conducted literature survey, few monitoring data exists for several European countries, such as Germany, France, and the UK. Lesser data are available for Asia, where approximately 80% of the studies focus on Japan. Several articles study the occurrence of mostly antiretroantivirals in sub-Saharan African countries, while there is a lack of data for other developing regions of the world, including the rest of Africa, South America, and the biggest part of Asia. An importantly smaller number of studies exists for North America, while no studies exist for Oceania. The against innfluenza drug oseltamivir along with its active carboxy metabolite is found to be the most studied antiviral drug. The distribution of antiviral drugs across all geographic regions varies from low ng L^-1 to high μg L^-1 levels, in some cases, even in surface waters. This overarching review reveals that monitoring of antiviral drugs is necessary, and some of those compounds may require toxicological attention, in the light of either spatial and temporal high concentration or potential antiviral resistance. Based on the information provided herein, the need for a better understanding of the water quality hazards posed by antiviral drugs existence in wastewater outputs and freshwater ecosystems is demosntrated. Finally, the future challenges concerning the occurrence, fate, and potential ecotoxicological risk to organisms posed by antiviral drug residues are discussed.

Current and Emerging Therapies for Ocular Herpes Simplex Virus Type-1 Infections

Herpes simplex virus type-1 (HSV-1) is a neurotropic, double-stranded DNA virus that can cause a wide variety of diseases, including many ocular pathologies. It is one of the leading causes of infectious blindness in the United States. Because of its ubiquitous nature and its potential to cause serious ocular maladies, there is a significant need for more effective antiviral therapies against ocular HSV-1. In this review, we discuss the lifecycle of HSV-1 as it pertains to corneal infections and the clinically approved as well as emerging treatments to combat HSV-1 infections. We also highlight some newly identified host targets for the antiviral drug development.

Guidelines from the 2017 European Conference on Infections in Leukaemia for management of HHV-6 infection in patients with hematologic malignancies and after hematopoietic stem cell transplantation

Of the two human herpesvirus 6 (HHV-6) species, human herpesvirus 6B (HHV-6B) encephalitis is an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplant. Guidelines for the management of HHV-6 infections in patients with hematologic malignancies or post-transplant were prepared a decade ago but there have been no other guidelines since then despite significant advances in the understanding of HHV-6 encephalitis, its therapy, and other aspects of HHV-6 disease in this patient population. Revised guidelines prepared at the 2017 European Conference on Infections in Leukaemia covering diagnosis, preventative strategies and management of HHV-6 disease are now presented.

Added value of ultra-deep sequencing (UDS) approach for detection of genotypic antiviral resistance of herpes simplex virus (HSV)

Classically, Sanger sequencing is considered the gold standard for detection of HSV drug resistance mutations (DRMs). As a complementary method, ultra-deep sequencing (UDS) has an improved ability to detect minor variants and mixed populations. The aim of this work was to apply UDS performed on MiSeq^® Illumina platform to the detection of HSV DRMs and to the evaluation of the subpopulation diversity in clinical samples in comparison with Sanger sequencing. A total of 59 HSV-positive clinical samples (31 HSV-1 and 28 HSV-2) recovered from 50 patients mainly immunocompromised (70%) were retrospectively analyzed. Remarkably, UDS analysis revealed significant differences of relative abundance according to the type of DRMs within TK and Pol: natural polymorphisms and amino acid changes associated with resistance to antivirals were identified as high-abundant mutations (>96%), whereas TK frameshifts conferring resistance to ACV were systematically detected at lower abundance (≈80%). This work also revealed that UDS can detect low-frequency DRMs and provides extensive information on viral population composition.

Herpes simplex virus resistant to acyclovir: A single-centre experience from the Czech Republic

INTRODUCTION AND AIM

Infections caused by herpes simplex viruses (HSV) are frequent in the human population. Because of the widespread use of long-term treatment or prophylaxis by anti-herpetic antivirals in various specific medical contexts (immunosuppression, recurrent infections), the level of antiviral resistance is increasing. According to previous studies, there is a low resistance level in immunocompetent populations but a relatively high level in populations with immunodeficiency. However, there has been no study from the Czech Republic. This study presents results of a single-centre retrospective study from the Czech Republic.

MATERIALS AND METHODS

Deep frozen DNA from patients with suspected clinical antiviral failure over a long time period (2009-2016) - a total of 15 isolates of HSV1 and seven of HSV2 - were examined for the presence of mutations associated with antiviral resistance. Sequence analysis was performed using an ABI PRISM 3500xL Genetic Analyzer (Applied Biosystems®).

RESULTS

There were no mutations associated with resistance to antivirals inside the UL23 gene in HSV1 isolates. However, resistant mutation D672N (nucleotide change G2014A) was found inside the UL30 gene in seven of the isolates. One mutation associated with resistance to acyclovir (M183stop) was found inside the UL23 gene in one HSV2 isolate. Resistant mutation E678G (nucleotide change A2033G) was identified inside the UL30 gene in six of the HSV2 isolates.

CONCLUSIONS

This study confirmed the presence of resistance mutations within the Czech population, but it will be necessary to examine a higher number of isolates for further conclusions.

Early Steps in Herpes Simplex Virus Infection Blocked by a Proteasome Inhibitor

Viruses commandeer host cell 26S proteasome activity to promote viral entry, gene expression, replication, assembly, and egress. Proteasomal degradation activity is critical for herpes simplex virus (HSV) infection. The proteasome inhibitor bortezomib (also known as Velcade and PS-341) is a clinically effective antineoplastic drug that is FDA approved for treatment of hematologic malignancies such as multiple myeloma and mantle cell lymphoma. Low nanomolar concentrations of bortezomib inhibited infection by HSV-1, HSV-2, and acyclovir-resistant strains. Inhibition coincided with minimal cytotoxicity. Bortezomib did not affect attachment of HSV to cells or inactivate the virus directly. Bortezomib acted early in HSV infection by perturbing two distinct proteasome-dependent steps that occur within the initial hours of infection: the transport of incoming viral nucleocapsids to the nucleus and the virus-induced disruption of host nuclear domain 10 (ND10) structures. The combination of bortezomib with acyclovir demonstrated synergistic inhibitory effects on HSV infection. Thus, bortezomib is a novel potential therapeutic for HSV with a defined mechanism of action.IMPORTANCE Viruses usurp host cell functions to advance their replicative agenda. HSV relies on cellular proteasome activity for successful infection. Proteasome inhibitors, such as MG132, block HSV infection at multiple stages of the infectious cycle. Targeting host cell processes for antiviral intervention is an unconventional approach that might limit antiviral resistance. Here we demonstrated that the proteasome inhibitor bortezomib, which is a clinically effective cancer drug, has the in vitro features of a promising anti-HSV therapeutic. Bortezomib inhibited HSV infection during the first hours of infection at nanomolar concentrations that were minimally cytotoxic. The mechanism of bortezomib's inhibition of early HSV infection was to halt nucleocapsid transport to the nucleus and to stabilize the ND10 cellular defense complex. Bortezomib and acyclovir acted synergistically to inhibit HSV infection. Overall, we present evidence for the repurposing of bortezomib as a novel antiherpesviral agent and describe specific mechanisms of action.

Report of Resistant Varicella Zoster Infection Treated With Donor Lymphocyte Infusion in a Pediatric Oncology Patient

We report an 8-year-old boy with disseminated, life-threatening, drug treatment-resistant varicella zoster infection occurring during standard treatment for neuroblastoma in whom viral clearance and cure was effected by donor Lymphocyte infusion from his HLA (Human leukocyte antigen)-identical twin sibling.

Improving Encapsulation of Hydrophilic Chloroquine Diphosphate into Biodegradable Nanoparticles: A Promising Approach against Herpes Virus Simplex-1 Infection

Chloroquine diphosphate (CQ) is a hydrophilic drug with low entrapment efficiency in hydrophobic nanoparticles (NP). Herpes simplex virus type 1 (HSV-1) is an enveloped double-stranded DNA virus worldwide known as a common human pathogen. This study aims to develop chloroquine-loaded poly(lactic acid) (PLA) nanoparticles (CQ-NP) to improve the chloroquine anti- HSV-1 efficacy. CQ-NP were successfully prepared using a modified emulsification-solvent evaporation method. Physicochemical properties of the NP were monitored using dynamic light scattering, atomic force microscopy, drug loading efficiency, and drug release studies. Spherical nanoparticles were produced with modal diameter of <300 nm, zeta potential of −20 mv and encapsulation efficiency of 64.1%. In vitro assays of CQ-NP performed in Vero E6 cells, using the MTT-assay, revealed different cytotoxicity levels. Blank nanoparticles (B-NP) were biocompatible. Finally, the antiviral activity tested by the plaque reduction assay revealed greater efficacy for CQ-NP compared to CQ at concentrations equal to or lower than 20 µg mL⁻¹ (p < 0.001). On the other hand, the B-NP had no antiviral activity. The CQ-NP has shown feasible properties and great potential to improve the antiviral activity of drugs.

Bowman‒Birk Inhibitor Suppresses Herpes Simplex Virus Type 2 Infection of Human Cervical Epithelial Cells

The Bowman‒Birk inhibitor (BBI), a protease inhibitor derived from soybeans, has been extensively studied in anti-tumor and anti-inflammation research. We recently reported that BBI has an anti-HIV-1 property in primary human macrophages. Because HSV-2 infection plays a role in facilitating HIV-1 sexual transmission, we thus examined whether BBI has the ability to inhibit HSV-2 infection. We demonstrated that BBI could potently inhibit HSV-2 replication in human cervical epithelial cells (End1/E6E7). This BBI-mediated HSV-2 inhibition was partially through blocking HSV-2-mediated activation of NF-κB and p38 MAPK pathways. In addition, BBI could activate the JAK/STAT pathway and enhance the expression of several antiviral interferon-stimulated genes (ISGs). Furthermore, BBI treatment of End1/E6E7 cells upregulated the expression of tight junction proteins and reduced HSV-2-mediated cellular ubiquitinated proteins’ degradation through suppressing the ubiquitin‒proteasome system. These observations indicate that BBI may have therapeutic potential for the prevention and treatment of HSV-2 infections.

Photodynamic Inactivation of Herpes Simplex Viruses

Herpes simplex virus (HSV) infections can be treated with direct acting antivirals like acyclovir and foscarnet, but long-term use can lead to drug resistance, which motivates research into broadly-acting antivirals that can provide a greater genetic barrier to resistance. Photodynamic inactivation (PDI) employs a photosensitizer, light, and oxygen to create a local burst of reactive oxygen species that inactivate microorganisms. The botanical plant extract Orthoquin^TM is a powerful photosensitizer with antimicrobial properties. Here we report that Orthoquin also has antiviral properties. Photoactivated Orthoquin inhibited herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) infection of target cells in a dose-dependent manner across a broad range of sub-cytotoxic concentrations. HSV inactivation required direct contact between Orthoquin and the inoculum, whereas pre-treatment of target cells had no effect. Orthoquin did not cause appreciable damage to viral capsids or premature release of viral genomes, as measured by qPCR for the HSV-1 genome. By contrast, immunoblotting for HSV-1 antigens in purified virion preparations suggested that higher doses of Orthoquin had a physical impact on certain HSV-1 proteins that altered protein mobility or antigen detection. Orthoquin PDI also inhibited the non-enveloped adenovirus (AdV) in a dose-dependent manner, whereas Orthoquin-mediated inhibition of the enveloped vesicular stomatitis virus (VSV) was light-independent. Together, these findings suggest that the broad antiviral effects of Orthoquin-mediated PDI may stem from damage to viral attachment proteins.

Antiviral Therapies for Herpesviruses: Current Agents and New Directions

PURPOSE

The objective of this review was to summarize the recent literature describing the current burden of disease due to herpesviruses in the antiviral and transplant era; describe mechanisms of action of antiviral agents and the development of resistance; summarize the literature of recent antiviral agents brought to market as well as agents under development; and to present literature on future strategies for herpesvirus therapeutics.

METHODS

An extensive search of the medical literature related to antiherpesviral therapy was conducted to compose this narrative review. Literature searches were performed via PubMed and ultimately 137 articles were included as most relevant to the scope of this article.

FINDINGS

Herpesviruses are a family of DNA viruses that are ubiquitous throughout human populations and share the feature of establishing lifelong infections in a latent phase with the potential of periodic reactivation. With the exception of herpes simplex virus, varicella zoster virus, and Epstein-Barr virus, which have a significant disease burden in individuals with normal immune function, the morbidity and mortality of the remaining viruses are primarily associated with the immunocompromised host. Over the last half-century, several agents have been tested in large randomized, placebo-controlled trials that have resulted in safe and effective antiviral agents for the treatment of many of these infections.

IMPLICATIONS

With increasing use of antiherpesviral agents for extended periods, particularly in immunocompromised hosts, the emergence of resistant viruses has necessitated the development of newer agents with novel targets and better side-effect profiles.

Herpes Zoster and Immunogenicity and Safety of Zoster Vaccines in Transplant Patients: A Narrative Review of the Literature

This narrative review focuses on the herpes zoster (HZ) and its prevention in transplant patients. Varicella zoster virus (VZV) is highly contagious and distributed worldwide in humans. Primary VZV infection usually causes varicella and then establishes a lifelong latency in dorsal root ganglia. Reactivation of VZV leads to HZ and related complications such as postherpetic neuralgia. Age and decreased immunity against VZV are important risk factors for developing HZ. Transplant patients are at increased risk for developing HZ and related complications due to their immunocompromised status and the need for lifetime immunosuppression. Diagnosis of HZ in transplant patients is often clinically difficult, and VZV-specific antibodies should be determined by serologic testing to document prior exposure to VZV during their pre-transplant evaluation process. Although antiviral agents are available, vaccination should be recommended for preventing HZ in transplant patients considering their complicated condition and weak organ function. Currently, there are two licensed HZ vaccines, of which one is a live-attenuated vaccine and the other is a HZ subunit vaccine. Both vaccines have shown promising safety and efficacy in transplants patients and especially the subunit vaccine could be administered post-transplant since this vaccine does not contain any live virus. Larger studies are needed about safety and immunogenicity of HZ vaccines in transplant populations, and extra efforts are needed to increase vaccine usage according to guidelines.

Titration of cell-associated varicella-zoster virus with the MV9G reporter cell line for antiviral studies

Titration of the cell-associated virus (CAV) of varicella-zoster virus (VZV) is essential for antiviral studies. A VZV reporter cell line, MV9G, generated in our previous study expresses firefly luciferase upon CAV infection in a dose-dependent manner, suggesting that use of the cell line for titration is feasible. In this study, MeWo cells infected with VZV vaccine Oka (vOka) strain or with clinical isolates obtained from patients with varicella or zoster were used as CAV. A co-culture of MV9G cells with the virus-infected MeWo cells were set up and optimized for titration of CAV. Luciferase activities of MV9G cells measured as relative light units (RLUs) of chemiluminescence correlated well (r > 0.9, p < 0.05) both with quantities of viral DNAs measured by TaqMan PCR and with numbers of viral foci detected by immunostaining with a monoclonal antibody against VZV IE62. In addition, the usefulness of MV9G for antiviral studies was exemplified by treatment of the VZV-infected cells with various concentrations of acyclovir. Thus, the reporter cell-based titration of CAV by measuring the induced RLUs may be a reliable way to estimate viral foci and viral DNAs.

Life cycle synchronization is a viral drug resistance mechanism

Viral infections are one of the major causes of death worldwide, with HIV infection alone resulting in over 1.2 million casualties per year. Antiviral drugs are now being administered for a variety of viral infections, including HIV, hepatitis B and C, and influenza. These therapies target a specific phase of the virus's life cycle, yet their ultimate success depends on a variety of factors, such as adherence to a prescribed regimen and the emergence of viral drug resistance. The epidemiology and evolution of drug resistance have been extensively characterized, and it is generally assumed that drug resistance arises from mutations that alter the virus's susceptibility to the direct action of the drug. In this paper, we consider the possibility that a virus population can evolve towards synchronizing its life cycle with the pattern of drug therapy. The periodicity of the drug treatment could then allow for a virus strain whose life cycle length is a multiple of the dosing interval to replicate only when the concentration of the drug is lowest. This process, referred to as "drug tolerance by synchronization", could allow the virus population to maximize its overall fitness without having to alter drug binding or complete its life cycle in the drug's presence. We use mathematical models and stochastic simulations to show that life cycle synchronization can indeed be a mechanism of viral drug tolerance. We show that this effect is more likely to occur when the variability in both viral life cycle and drug dose timing are low. More generally, we find that in the presence of periodic drug levels, time-averaged calculations of viral fitness do not accurately predict drug levels needed to eradicate infection, even if there is no synchronization. We derive an analytical expression for viral fitness that is sufficient to explain the drug-pattern-dependent survival of strains with any life cycle length. We discuss the implications of these findings for clinically relevant antiviral strategies.

Utility of ultra-deep sequencing for detection of varicella-zoster virus antiviral resistance mutations

We report the first application of ultra-deep sequencing (UDS) to varicella-zoster virus (VZV) genotypic antiviral testing in a case of acyclovir-resistant VZV infection initially detected by Sanger sequencing within a deeply immunocompromised heart transplant recipient. As added-value compared to Sanger analysis, UDS revealed complex dynamics of viral population under antiviral pressure. Varicella-zoster virus (VZV) is a ubiquitous human herpesvirus affecting populations worldwide. VZV is commonly acquired in youth whose primary infection usually manifests as benign varicella (chickenpox). After the initial infection, the virus establishes lifelong latency in sensory ganglia leading to a risk of subsequent reactivation. Reactivation usually results in the development of localized herpes zoster (HZ) lesions, a painful skin rash commonly known as shingles (Cohen, 2013). The incidence and severity of HZ increase with impaired specific cell-mediated immunity mainly as a result of increasing age, malignancy, immunodeficiency, organ transplantation, or immunosuppressive drug therapy (Cohen, 2013; Koo et al., 2014; Pavlopoulou et al., 2015). In particular, HZ remains a significant cause of morbidity among solid organ transplant (SOT) recipients, especially in patients undergoing heart transplantation (HT) compared with liver, kidney, or lung transplant recipients (Carby et al., 2007; Koo et al., 2014; Pavlopoulou et al., 2015). These particular individuals are at increased risk of primary infection, reactivation followed by dissemination with visceral involvement and associated with bacterial superinfection, and chronic recurrences (Cohen, 2013). VZV infections may also engender debilitating neuralgia among highly immunocompromised patients (Sampathkumar et al., 2009). HT is also associated with the risk of reactivation of other latent viruses belonging to the Herpesviridae family as herpes simplex virus (HSV). Currently licensed drugs to prevent or to cure HSV- or VZV-associated diseases target the viral DNA polymerase (Pol). Acyclovir (ACV) and its prodrug valacyclovir (VACV) are considered as the first-line therapy, whereas foscarnet (FOS) or cidofovir (CDV) constitute alternative options. After primophosphorylation by the viral thymidine kinase (TK), ACV targets the viral DNA polymerase and inhibits the viral genome replication by a chain termination mechanism. According to this mechanism of action, viral mutations conferring resistance to ACV have been mapped both in TK and Pol encoding genes. Viral mutations conferring resistance to FOS and CDV are only detected in Pol gene. VZV ACV-resistance is mostly mediated by TK alterations, consisting in either translational frameshifts, sometimes associated with premature stop codon, or amino acid substitutions. In the remaining cases, amino acid substitutions are detected within Pol (De et al., 2015; Piret and Boivin, 2014). Classically, Sanger sequencing has been recognized as the gold standard for the detection of drug resistance mutations (DRMs) within VZV TK and Pol genes (Perrier et al., 2016; Piret and Boivin, 2014). However, this approach cannot detect minor variants present at a frequency below 20%. Ultra-deep sequencing (UDS) has an enhanced sensitivity compared to Sanger method and allows quantitative evaluation of the viral mutants (Chin et al., 2013). We report here a case of VZV resistant infection in an HT recipient. Our retrospective study aimed at showing the utility of UDS for DRM detection as a complement of Sanger method.

Antiviral resistance in herpes simplex virus and varicella-zoster virus infections: diagnosis and management

PURPOSE OF REVIEW

Aciclovir (ACV) is the first-line drug for the management of herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections. Long-term administration of ACV for the treatment of severe infections in immunocompromised patients can lead to the development of drug resistance. Furthermore, the emergence of isolates resistant to ACV is increasingly recognized in immunocompetent individuals with herpetic keratitis. This review describes the mechanisms involved in drug resistance for HSV and VZV, the laboratory diagnosis and management of patients with infections refractory to ACV therapy.

RECENT FINDINGS

Genotypic testing is more frequently performed for the diagnosis of infections caused by drug-resistant HSV or VZV isolates. Molecular biology-based systems for the generation of recombinant viruses have been developed to link unknown mutations with their drug phenotypes. Fast and sensitive methods based on next-generation sequencing will improve the detection of heterogeneous viral populations of drug-resistant viruses and their temporal changes during antiviral therapy, which could allow better patient management. Novel promising compounds acting on targets that differ from the viral DNA polymerase are under clinical development.

SUMMARY

Antiviral drug resistance monitoring for HSV and VZV is required for a rational use of antiviral therapy in high-risk populations.

A Simple Platform for the Rapid Development of Antimicrobials

Recent infectious outbreaks highlight the need for platform technologies that can be quickly deployed to develop therapeutics needed to contain the outbreak. We present a simple concept for rapid development of new antimicrobials. The goal was to produce in as little as one week thousands of doses of an intervention for a new pathogen. We tested the feasibility of a system based on antimicrobial synbodies. The system involves creating an array of 100 peptides that have been selected for broad capability to bind and/or kill viruses and bacteria. The peptides are pre-screened for low cell toxicity prior to large scale synthesis. Any pathogen is then assayed on the chip to find peptides that bind or kill it. Peptides are combined in pairs as synbodies and further screened for activity and toxicity. The lead synbody can be quickly produced in large scale, with completion of the entire process in one week.