Efficacy of pritelivir and acyclovir in the treatment of herpes simplex virus infections in a mouse model of herpes simplex encephalitis

The opportunities and challenges of epigenetic approaches to manage herpes simplex infections

INTRODUCTION

Despite the existence of antivirals that potently and efficiently inhibit the replication of herpes simplex virus 1 and 2 (HSV-1, -2), their ability to establish and maintain, and reactivate from, latency has precluded the development of curative therapies. Several groups are exploring the opportunities of targeting epigenetic regulation to permanently silence latent HSV genomes or induce their simultaneous reactivation in the presence of antivirals to flush the latent reservoirs, as has been explored for HIV.

AREAS COVERED

This review covers the basic principles of epigenetic regulation with an emphasis on those mechanisms relevant to the regulation of herpes simplex viruses, as well as the current knowledge on the regulation of lytic infections and the establishment and maintenance of, and reactivation from, latency, with an emphasis on epigenetic regulation. The differences with the epigenetic regulation of viral and cellular gene expression are highlighted as are the effects of known epigenetic regulators on herpes simplex viruses. The major limitations of current models to the development of novel antiviral strategies targeting latency are highlighted.

EXPERT OPINION

We provide an update on the epigenetic regulation during lytic and latent HSV-1 infection, highlighting the commonalities and differences with cellular gene expression and the potential of epigenetic drugs as antivirals, including the opportunities, challenges, and potential future directions.

Discovery of a small-molecule inhibitor of KSHV lytic replication from the MMV pandemic response box

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent for primary effusion lymphoma (PEL), multicentric Castleman's disease (MCD) and Kaposi's sarcoma (KS). KSHV is one of the oncoviruses that contribute to 1.5 million new infection-related cancer cases annually. Currently, there are no targeted therapies for KSHV-associated diseases. Through the development of a medium-throughput phenotype-based ELISA screening platform based on KSHV ORF57 protein detection, we screened the Medicines for Malaria Venture (MMV) Pandemic Response Box for non-cytotoxic inhibitors of KSHV lytic replication. MMV1645152 was identified as a promising inhibitor of KSHV lytic replication, suppressing KSHV immediate-early and late lytic gene expression and blocking the production of infectious KSHV virion particles at non-cytotoxic concentrations in cell line models of KSHV infection with or without EBV coinfection. MMV1645152 is a promising hit compound for the development of future therapeutic agents against KSHV-associated malignancies.

Development and validation of HPLC-ultraviolet method for quantitative determination of pritelivir in human placental perfusion medium

A simple and reliable HPLC-ultraviolet (HPLC-UV) method was developed and validated for the quantification of pritelivir in the samples of medium from the experiments utilizing the ex vivo technique of dual perfusion of the human placental lobule. Phenacetin was used as an internal standard (IS) in our HPLC-UV method. Chromatographic separation of pritelivir and phenacetin was achieved on a Waters Symmetry C18 HPLC column (100 × 2.1 mm, 3.5 μm) at ambient temperature (22-25°C). The mobile phase was composed of 50% methanol in deionized water (v/v), the flow rate for isocratic elution was established at 0.25 mL/min, and the detection wavelength for pritelivir and IS was set at 254 nm. Pritelivir and IS were extracted with the protein precipitation method using methanol as a solvent. The calibration curve for pritelivir exhibited linearity (r2 > 0.99) within the concentration range from 0.155 to 6.62 μg/mL. Within- and between-day accuracy ranged from 97% to 110% with relative standard deviation (RSD) values not exceeding 10%. The extraction recovery of pritelivir and IS ranged from 89% to 91% with RSD not exceeding 7%. Pritelivir was stable under the storage and sample handling conditions. This validated HPLC-UV method was utilized to quantify pritelivir in the placental perfusion medium samples, and the resulting concentrations were authenticated with incurred sample reanalysis to confirm the reliability of the method.

Advances and prospect in herpesviruses infections after haematopoietic cell transplantation: closer to the finish line?

BACKGROUND

Herpesviruses represent common and significant infectious complications after allogeneic haematopoietic cell transplantation (HCT). In the last decade, major advances in the prevention and treatment of these infections were accomplished.

OBJECTIVES

The aim of this paper is to review the recent advances in the prophylaxis and treatment of herpesvirus infections after allogeneic HCT, to assess the persisting challenges, and to offer future directions for the prevention and management of these infections.

SOURCES

We searched PubMed for relevant literature regarding specific herpesviruses complicating allogeneic HCT through March 2024.

CONTENT

The largest advances in this past decade were witnessed for cytomegalovirus (CMV) with the advent of letermovir for primary prophylaxis and the development of maribavir as an option for refractory and/or resistant CMV infections in transplant recipients. For varicella zoster virus, prevention of reactivation with the recombinant zoster vaccine offers an additional prophylactic intervention. Pritelivir is being explored for the treatment of drug-resistant or refractory Herpes simplex virus infections. Although rituximab is now an established option for preemptive therapy for Epstein-Barr virus, Human Herpesvirus-6 remains the most elusive virus of the herpesvirus family, with a lack of evidence supporting the benefit of any agent for prophylaxis or for optimal preemptive therapy.

IMPLICATIONS

Although considerable advances have been achieved for the treatment and prevention of herpes virus infections, most notably with CMV, the coming years should hold additional opportunities to tame the beast in these herpesviruses postallogeneic HCT, with the advent of new antivirals, cell-mediated immunity testing, and cytotoxic T lymphocytes infusions.

ACV with/without IVM: a new talk on intestinal CDX2 and muscular CD34 and Cyclin D1 during Trichinella spiralis infection

The current study assessed the efficacy of Acyclovir (ACV) and Ivermectin (IVM) as monotherapies and combined treatments for intestinal and muscular stages of Trichinella spiralis infection. One-hundred Swiss albino mice received orally 250 ± 50 infectious larvae and were divided into infected-untreated (Group-1), IVM-treated (Group-2), ACV-treated (Group-3), combined IVM+ACV (Group-4), and healthy controls (Group-5). Each group was subdivided into subgroup-A-enteric phase (10 mice, sacrificed day-7 p.i.) and subgroup-B-muscular phase (10 mice, sacrificed day-35 p.i.). Survival rate and body weight were recorded. Parasite burden and intestinal histopathology were assessed. In addition, immunohistochemical expression of epithelial CDX2 in the intestinal phase and CyclinD1 as well as CD34 in the muscular phase were evaluated. Compared, IVM and ACV monotherapies showed insignificant differences in the amelioration of enteric histopathology, except for lymphocytic counts. In the muscle phase, monotherapies showed variable disruptions in the encapsulated larvae. Compared with monotherapies, the combined treatment performed relatively better improvement of intestinal inflammation and reduction in the enteric and muscular parasite burden. CDX2 and CyclinD1 positively correlated with intestinal inflammation and parasite burden, while CD34 showed a negative correlation. CDX2 positively correlated with CyclinD1. CD34 negatively correlated with CDX2 and CyclinD1. IVM +ACV significantly ameliorated CDX2, CyclinD1, and CD34 expressions compared with monotherapies. Conclusion. T. spiralis infection-associated inflammation induced CDX2 and CyclinD1 expressions, whereas CD34 was reduced. The molecular tumorigenic effect of the nematode remains questionable. Nevertheless, IVM +ACV appeared to be a promising anthelminthic anti-inflammatory combination that, in parallel, rectified CDX2, CyclinD1, and CD34 expressions.

Large Subunit of the Human Herpes Simplex Virus Terminase as a Promising Target in Design of Anti-Herpesvirus Agents

Herpes simplex virus type 1 (HSV-1) is an extremely widespread pathogen characterized by recurrent infections. HSV-1 most commonly causes painful blisters or sores around the mouth or on the genitals, but it can also cause keratitis or, rarely, encephalitis. First-line and second-line antiviral drugs used to treat HSV infections, acyclovir and related compounds, as well as foscarnet and cidofovir, selectively inhibit herpesvirus DNA polymerase (DNA-pol). It has been previously found that (S)-4-[6-(purin-6-yl)aminohexanoyl]-7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine (compound 1) exhibits selective anti-herpesvirus activity against HSV-1 in cell culture, including acyclovir-resistant mutants, so we consider it as a lead compound. In this work, the selection of HSV-1 clones resistant to the lead compound was carried out. High-throughput sequencing of resistant clones and reference HSV-1/L2 parent strain was performed to identify the genetic determinants of the virus's resistance to the lead compound. We identified a candidate mutation presumably associated with resistance to the virus, namely the T321I mutation in the UL15 gene encoding the large terminase subunit. Molecular modeling was used to evaluate the affinity and dynamics of the lead compound binding to the putative terminase binding site. The results obtained suggest that the lead compound, by binding to pUL15, affects the terminase complex. pUL15, which is directly involved in the processing and packaging of viral DNA, is one of the crucial components of the HSV terminase complex. The loss of its functional activity leads to disruption of the formation of mature virions, so it represents a promising drug target. The discovery of anti-herpesvirus agents that affect biotargets other than DNA polymerase will expand our possibilities of targeting HSV infections, including those resistant to baseline drugs.

First-in-Human, Single- and Multiple-Ascending-Dose, Food-Effect, and Absolute Bioavailability Trials to Assess the Pharmacokinetics, Safety, and Tolerability of Pritelivir, a Nonnucleoside Helicase-Primase Inhibitor Against Herpes Simplex Virus in Healthy Subjects

The pharmacokinetics and safety of the novel herpes simplex virus helicase-primase inhibitor pritelivir were evaluated in 5 phase 1 trials: a single-ascending-dose trial, 2 multiple-ascending-dose trials, a food-effect trial, and an absolute bioavailability trial in healthy male subjects. One cohort of healthy female subjects was included in the single-ascending-dose trial. Pritelivir pharmacokinetics were linear up to 480 mg following single and up to 400 mg following multiple once-daily doses. The half-life ranged from 52 to 83 hours, and steady state was reached between 8 and 13 days. Maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last quantifiable concentration were 1.5- and 1.1-fold higher in female compared to male subjects. Absolute bioavailability was 72% under fasted conditions. Following a fatty diet, pritelivir time to maximum concentration was 1.5 hour delayed and maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last quantifiable concentration were 33% and 16% higher, respectively. Pritelivir was safe and well tolerated up to 600 mg following single and up to 200 mg following multiple once-daily doses. Considering a therapeutic dose of 100 mg once-daily, pritelivir demonstrated a favorable safety and tolerability and pharmacokinetic profile in healthy subjects to support further development.

Analysis of Metagenomic Next-Generation Sequencing (mNGS) in the Diagnosis of Herpes Simplex Virus (HSV) Encephalitis with Normal Cerebrospinal Fluid (CSF)

Background

Metagenomic next-generation sequencing (mNGS) is becoming increasingly extensive in diagnosing herpes simplex encephalitis (HSE). However, many HSE patients with normal cerebrospinal fluid (CSF) diagnosed by mNGS have been found during the clinical application. This study aimed to summarize and analyze the clinical characteristics, supplementary examinations, and prognosis of patients with HSE whose cerebrospinal fluid was confirmed to be normal by mNGS.

Methods

This retrospective study evaluated the clinical characteristics, auxiliary examinations, and patient prognosis of patients with HSE that were diagnosed by mNGS but had normal CSF. Clinical data collected included baseline information, signs and symptoms upon admission, and risk factors for infection. Auxiliary examinations included indirect immunofluorescence assay (IIF), cell-based assay (CBA), and CSF testing. Prognosis was evaluated based on hospital stay and patient survival.

Results

Seven of the nine patients (77.8%) experienced headaches, and four (44.4%) had a fever of 38°C or higher. The average leukocyte count in the CSF was 2.6 ± 2.3/L. According to the mNGS, the median sequence count of HSV was 2 (1, 16). Magnetic resonance imaging (MRI) revealed one bilateral temporal lobe lesion (11.1%), two isolated bilateral frontal lobe lesions (22.2%), and one bilateral cingulate gyrus lesion (11.1%). One patient (11.1%) was admitted to the intensive care unit and passed away in the hospital. The remaining patients (88.9%) had a positive prognosis upon discharge.

Conclusion

Patients with HSE who had normal CSF were typically middle-aged women with normal immune function. They showed typical HSE clinical features, such as fever, headache and epilepsy, that did not differ from those of other HSE patients. A normal CSF result is generally associated with a low viral load and the body's ability to mount an effective immune response. Most of these patients have a favorable prognosis.

Novel inhibitors of HSV-1 protease effective in vitro and in vivo

Herpes simplex virus type 1 (HSV-1) is a widespread human pathogen known to cause infections of diverse severity, ranging from mild ulceration of mucosal and dermal tissues to life-threatening viral encephalitis. In most cases, standard treatment with acyclovir is sufficient to manage the disease progression. However, the emergence of ACV-resistant strains drives the need for new therapeutics and molecular targets. HSV-1 VP24 is a protease indispensable for the assembly of mature virions and, as such, constitutes an interesting target for the therapy. In this study, we present novel compounds, KI207M and EWDI/39/55BF, that block the activity of VP24 protease and consequently inhibit HSV-1 infection in vitro and in vivo. The inhibitors were shown to prevent the egress of viral capsids from the cell nucleus and suppress the cell-to-cell spread of the infection. They were also proven effective against ACV-resistant HSV-1 strains. Considering their low toxicity and high antiviral potency, the novel VP24 inhibitors could provide an alternative for treating ACV-resistant infections or a drug to be used in combined, highly effective therapy.

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.

Optimizing Antiviral Dosing for HSV and CMV Treatment in Immunocompromised Patients

Herpes simplex virus (HSV) and cytomegalovirus (CMV) are DNA viruses that are common among humans. Severely immunocompromised patients are at increased risk of developing HSV or CMV disease due to a weakened immune system. Antiviral therapy can be challenging because these drugs have a narrow therapeutic window and show significant pharmacokinetic variability. Above that, immunocompromised patients have various comorbidities like impaired renal function and are exposed to polypharmacy. This scoping review discusses the current pharmacokinetic (PK) and pharmacodynamic (PD) knowledge of antiviral drugs for HSV and CMV treatment in immunocompromised patients. HSV and CMV treatment guidelines are discussed, and multiple treatment interventions are proposed: early detection of drug resistance; optimization of dose to target concentration by therapeutic drug monitoring (TDM) of nucleoside analogs; the introduction of new antiviral drugs; alternation between compounds with different toxicity profiles; and combinations of synergistic antiviral drugs. This research will also serve as guidance for future research, which should focus on prospective evaluation of the benefit of each of these interventions in randomized controlled trials.

Discovery, Chemistry, and Preclinical Development of Pritelivir, a Novel Treatment Option for Acyclovir-Resistant Herpes Simplex Virus Infections

When the nucleoside analogue acyclovir was introduced in the early 1980s, it presented a game-changing treatment modality for herpes simplex virus infections. Since then, work has been ongoing to improve the weaknesses that have now been identified: a narrow time window for therapeutic success, resistance in immunocompromised patients, little influence on frequency of recurrences, relatively fast elimination, and poor bioavailability. The present Drug Annotation focuses on the helicase–primase inhibitor pritelivir currently in development for the treatment of acyclovir-resistant HSV infections and describes how a change of the molecular target (from viral DNA polymerase to the HSV helicase–primase complex) afforded improvement of the shortcomings of nucleoside analogs. Details are presented for the discovery process leading to the final drug candidate, the pivotal preclinical studies on mechanism of action and efficacy, and on how ongoing clinical research has been able to translate preclinical promises into clinical use.

Herpesvirus-Associated Encephalitis: an Update

Purpose of Review

Recent Findings

Summary

Evaluating the therapeutic efficacy of triptolide and (S)-10-hydroxycamptothecin on cutaneous and ocular Herpes Simplex Virus type-1 infections in mice

Objective

The emergence of Acyclovir-Resistant Herpes Simplex Virus type-1, which is the result of clinical over usage calls for the urgent need of a novel anti-HSV agent. Hence, the activity of Triptolide (TP) and (S)-10-Hydroxycamptothecin (10-HCPT) were investigated as natural products in two infection models of HSV-1.

Methods

The antiviral efficacy of TP and 10-HCPT was evaluated in mice ocular and cutaneous infection models of HSV. Groups of 10 mice were infected with HSV-1. Both compounds were administered topically on corneal and skin. The disease severity, viral titer (plaque reduction assay), and histopathology were evaluated in the ocular and cutaneous models of HSV-1 infection on days 3, 5, 7, 9, and 12 post infection, as well as genome loads on days 3 and 12.

Results

Topical treatment of corneal with TP, 10-HCPT, and ACV was effective in reducing stromal disease (after day 3, P = 0.001), plus TP and ACV on vascularization (after day 7, P = 0.001). The virus titer decreased significantly in the infected treated groups after day 3 (P < 0.05). Also, on day 12 post-infection, the virus genome volume in the TP and ACV groups was significantly reduced. With respect to virus titers and the DNA yield, significant difference was observed, merely in the ACV group in comparison to the control (P = 0.013). Immunohistochemistry analysis showed that corneal epithelium healing was partially visible in the 10-HCPT group, which gradually increased in TP, and was the highest in the ACV group. The skin epithelium healing was only observed in TP and ACV groups, and was superior in the ACV group.

Conclusions

This study revealed the virologic and clinical potential of TP in-vivo to treat ocular mouse model.

Comprehensive clinical and virological characterization of three cases of fulminant liver failure owing to HSV1 primary infection

Herpes simplex virus 1 (HSV-1) is a frequently unrecognized, yet deadly cause of acute liver failure (ALF). We, therefore, analysed three cases of fatal HSV-1-induced ALF. All patients shared clinical (extremely elevated transaminases, LDH and AST/LDH ratio < 1) and virological characteristics (ratio of viral load in plasma versus throat swabs: 60-700-fold, lack of anti-HSV-1-IgG antibodies or low IgG-avidity during primary infection), which may help to identify patients at risk. Additionally, in vitro chemosusceptibility assays revealed high efficacy of the helicase-primase inhibitors (HPI), pritelivir and drug-candidate IM-250 compared to acyclovir (ACV) using HSV-1-isolates from two patients; hence, ACV/HPI-combinations might offer new therapeutic options for HSV-induced ALF.

Helicase primase inhibitors (HPIs) are efficacious for therapy of human herpes simplex virus (HSV) disease in an infection mouse model

Although the seroprevalence of Herpes simplex virus type 1 (HSV-1) currently amounts to ∼ 67% worldwide, the annual incidence of a severe disease progression, particularly herpes encephalitis, is approximately 2-4 cases per 1,000,000 infections. Nucleoside analogues, such as acyclovir (ACV), valacyclovir (VACV) or famciclovir, are still the therapeutic treatment of choice for HSV infections. However, nucleoside drugs have limited efficacy against severe HSV disease and for treatment of nucleoside-resistant viral strains, alternative therapies such as helicase-primase inhibitors (HPIs) which are highly potent by inhibiting viral replication are under development. In preclinical studies we analyzed the antiviral efficacy of drug candidates of a novel compound class of HPIs for the treatment of HSV to identify the most active eutomer structure in an intranasal infection mouse lethal challenge model. HSV-1 infected BALB/c mice treated with vehicle control developed fatal disease according to humane endpoints after 5-7 days. In contrast, the animals dosed orally once daily with the HPI compounds at 10 or 4 mg/kg/day showed a significantly increased survival (70% and 100% for 10 mg/kg/day; 90% and 100% for 4 mg/kg/day, respectively) compared to the vehicle treatment (0-10%), when therapy was initiated 6 h post HSV-1 inoculation. We observed a significantly improved outcome in clinical parameters and survival over 21 days in the group receiving novel HPI candidates using even the lowest dose of 4 mg/kg/day. With VACV treatment of 75 mg/kg daily survival was also significantly increased (80%-90% for 75 mg/kg/day) but to lesser extent. Initial IM-250 therapy at 10 mg/kg/day could be delayed up to 72 h resulting in significantly increased survival compared to the vehicle control. Furthermore, we detected significantly fewer viral genome copies in the lungs and brains of HPI treated animals compared to vehicle (440-fold reduction for 4 mg/kg/day IM-250 in the brain) or VACV controls by quantitative PCR. In conclusion the preclinical studies of the novel HPI compounds showed superior efficacy in comparison to the current standard HSV treatment represented by VACV with respect to the survival according humane endpoints, the clinical score and virus load in lungs and brains. Thus, candidates of this new drug class are promising antivirals of HSV infections and further translation into clinical trials is warranted.

Chromatin-mediated epigenetic regulation of HSV-1 transcription as a potential target in antiviral therapy

The ability to establish, and reactivate from, latent infections is central to the biology and pathogenesis of HSV-1. It also poses a strong challenge to antiviral therapy, as latent HSV-1 genomes do not replicate or express any protein to be targeted. Although the processes regulating the establishment and maintenance of, and reactivation from, latency are not fully elucidated, the current general consensus is that epigenetics play a major role. A unifying model postulates that whereas HSV-1 avoids or counteracts chromatin silencing in lytic infections, it becomes silenced during latency, silencing which is somewhat disrupted during reactivation. Many years of work by different groups using a variety of approaches have also shown that the lytic HSV-1 chromatin is distinct and has unique biophysical properties not shared with most cellular chromatin. Nonetheless, the lytic and latent viral chromatins are typically enriched in post translational modifications or histone variants characteristic of active or repressed transcription, respectively. Moreover, a variety of small molecule epigenetic modulators inhibit viral replication and reactivation from latency. Despite these successes in culture and animal models, it is not obvious how epigenetic modulation would be used in antiviral therapy if the same epigenetic mechanisms governed viral and cellular gene expression. Recent work has highlighted several important differences between the viral and cellular chromatins, which appear to be of consequence to their respective epigenetic regulations. In this review, we will discuss the distinctiveness of the viral chromatin, and explore whether it is regulated by mechanisms unique enough to be exploited in antiviral therapy.

Tandem mass spectrometry of small-molecule antiviral drugs: 3. antiviral agents against herpes, influenza and other viral infections

For the treatment of various viral infections, antiviral drugs may be used. Liquid chromatography-mass spectrometry (LC-MS) with tandem mass spectrometry (MS-MS) operated in selected-reaction monitoring (SRM) mode is the method of choice in quantitative bioanalysis of drugs, e.g., to establish bioavailability, to study pharmacokinetics, and later on possibly for therapeutic drug monitoring. In this study, the fragmentation in MS-MS of small-molecule antiviral drugs against herpes and influenza viruses is reviewed. In this way, insight is gained on the identity of the product ions used in SRM. Fragmentation schemes of antiviral agents are also relevant in the identification of drug metabolites or (forced) degradation products. As information of the fragmentation of antiviral drugs in MS-MS and the identity of the product ions is very much scattered in the scientific literature, it was decided to collect this information and to review it. In this third study, attention is paid to small-molecule antiviral agents used against herpes and influenza virus infections. In addition, some attention is paid to broad-spectrum antiviral agents, that are investigated with respect to their efficacy in challenging virus infections of this century, e.g., involving Ebola, Zika and corona viruses, like SARS-CoV-2, which is causing a world-wide pandemic at this very moment. The review provides fragmentation schemes of ca. 35 antiviral agents. The identity of the product ions used in SRM, i.e., elemental composition and exact-m/z, is tabulated, and more detailed fragmentation schemes are provided.

Formulation of acyclovir-loaded solid lipid nanoparticles: 2. Brain targeting and pharmacokinetic study

Acyclovir (ACV) is widely used in the treatment of herpes encephalitis. The present study was conducted to prepare chitosan-tween 80 coated solid lipid nanoparticles (SLNs) as a delivery system for brain targeting of ACV in rabbits. The SLNs were prepared and coated in one step by microemulsion method using a coating solution containing chitosan (0.1% w/v) and tween 80 (2% w/v) for loading sustained release ACV. In vitro characterization was performed for coated ACV-SLNs. Concerning in vivo experiments; a single intravenous bolus dose of coated ACV-SLNs was given versus free ACV solution to rabbits (62 mg/kg). Plasma pharmacokinetic parameters were calculated from the ACV concentration-time profiles in plasma using the two compartmental analysis. The values of AUC_0-∞ and MRT of coated ACV-SLNs were higher than free drug by about twofold, 233.36 ± 41.56 μg.h/mL and 1.81 ± 0.36 h, respectively. The noncompartmental analysis was conducted to estimate the brain pharmacokinetic parameters. The AUC_0-∞ brain/AUC_0-∞ plasma ratio for coated ACV-SLNs and free ACV was 0.22 and 0.12, respectively. These results indicated the effectiveness of using coated ACV-SLNs for brain targeting.

Roles of HSV-1 infection-induced microglial immune responses in CNS diseases: friends or foes?

Microglia, as brain-resident macrophages, are the first line of defense against brain invading pathogens. Further, their dysfunction has been recognized to be closely associated with mounting CNS diseases. Of note, chronic HSV-1 infection leads to the persistent activation of microglia, which elicit a comprehensive response by generating certain factors with neurotoxic and neuroprotective effects. CNS infection with HSV-1 results in herpes simplex encephalitis and herpes simplex keratitis. Microglial immune response plays a crucial role in the development of these diseases. Moreover, HSV-1 infection is strongly associated with several CNS diseases, especially Alzheimer's disease and schizophrenia. These CNS diseases can be effectively ameliorated by eliciting an appropriate immune response, such as inhibition of microglial proliferation and activation. Therefore, it is crucial to reassess the positive and negative roles of microglia in HSV-1 CNS infection for a more comprehensive and detailed understanding of the relationship between microglia and CNS diseases. Hence, the present review focuses on the dual roles of microglia in mediating HSV-1 CNS infection, as well as on the strategy of targeting microglia to ameliorate CNS diseases. Further research in this field can help comprehensively elucidate the dual role of the microglial immune response in HSV-1 CNS infection, providing a theoretical basis for identifying therapeutic targets against overactive microglia in CNS diseases and HSV-1 infection.

The interplay between viruses and TRIM family proteins

Novel therapeutic options are urgently needed to improve the global treatment of viral infections. Tripartite motif (TRIM) family proteins are involved in various biological and cellular functions including differentiation, development, proliferation, oncogenesis, innate immunity, and viral autophagy. Various TRIM proteins show antiviral properties against different viral infections and are now transitioning from ubiquitin proteins to an efficient and emerging therapeutic class of proteins. TRIM proteins combat viruses by targeting them at pre/post transcription levels. This review summarizes the comprehensive roles of different TRIM proteins along with their expression systems and their applications towards antiviral therapeutics.

A Preclinical Model for Studying Herpes Simplex Virus Infection

Herpes simplex virus (HSV) infections can cause considerable morbidity. Currently, nucleoside analogues such as acyclovir are widely used for treatment. However, HSV infections resistant to these drugs are a clinical problem among immunocompromised patients. To provide more efficient therapy and to counteract resistance, a different class of antiviral compounds has been developed. Pritelivir, a helicase primase inhibitor, represents a promising candidate for improved therapy. Here, we established an HSV-1 infection model on microneedle-pretreated human skin ex vivo. We identified HSV-1–specific histological changes (e.g., cytopathic effects, multinucleated giant cells), down-regulation of nectin-1, nuclear translocation of NF-κB (p65), interferon regulatory factor 3 (IRF3), and signaling of the IFN-inducible protein MxA. Accordingly, this model was used to test the potency of pritelivir compared with the standard drug acyclovir. We discovered that both drugs had a comparable efficacy for inhibiting HSV-1 replication, suggesting that pritelivir could be an alternative therapeutic agent for patients infected with acyclovir-resistant strains. To our knowledge, we present a previously unreported ex vivo HSV-1 infection model with abdominal human skin to test antiviral drugs, thus bridging the gap between in vitro and in vivo drug screening and providing a valuable preclinical platform for HSV research.

Insights into the pathogenesis of herpes simplex encephalitis from mouse models

A majority of the world population is infected with herpes simplex viruses (HSV; human herpesvirus types 1 and 2). These viruses, perhaps best known for their manifestation in the genital or oral mucosa, can also cause herpes simplex encephalitis, a severe and often fatal disease of the central nervous system. Antiviral therapies for HSV are only partially effective since the virus can establish latent infections in neurons, and severe pathological sequelae in the brain are common. A better understanding of disease pathogenesis is required to develop new strategies against herpes simplex encephalitis, including the precise viral and host genetic determinants that promote virus invasion into the central nervous system and its associated immunopathology. Here we review the current understanding of herpes simplex encephalitis from the host genome perspective, which has been illuminated by groundbreaking work on rare herpes simplex encephalitis patients together with mechanistic insight from single-gene mouse models of disease. A complex picture has emerged, whereby innate type I interferon-mediated antiviral signaling is a central pathway to control viral replication, and the regulation of immunopathology and the balance between apoptosis and autophagy are critical to disease severity in the central nervous system. The lessons learned from mouse studies inform us on fundamental defense mechanisms at the interface of host–pathogen interactions within the central nervous system, as well as possible rationales for intervention against infections from severe neuropathogenic viruses.

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

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