Animal models of herpes simplex virus immunity and pathogenesis

Safety of non-replicative and oncolytic replication-selective HSV vectors

Herpes simplex virus type 1 (HSV-1) is a DNA virus and human pathogen used to construct promising therapeutic vectors. HSV-1 vectors fall into two classes: replication-selective oncolytic vectors for cancer therapy and defective non-replicative vectors for gene therapy. Vectors from each class can accommodate ≥30 kb of inserts, have been approved clinically, and demonstrate a relatively benign safety profile. Despite oncolytic HSV (oHSV) replication in tumors and elicited immune responses, the virus is well tolerated in cancer patients. Current non-replicative vectors elicit only limited immune responses. Seropositivity and immune responses against HSV-1 do not eliminate either the vector or infected cells, and the vectors can therefore be re-administered. In this review we highlight vectors that have been translated to the clinic and host-virus immune interactions that impact on the safety and efficacy of HSVs.

Gene editing for latent herpes simplex virus infection reduces viral load and shedding in vivo

Anti-HSV therapies are only suppressive because they do not eliminate latent HSV present in ganglionic neurons, the source of recurrent disease. We have developed a potentially curative approach against HSV infection, based on gene editing using HSV-specific meganucleases delivered by adeno-associated virus (AAV) vectors. Gene editing performed with two anti-HSV-1 meganucleases delivered by a combination of AAV9, AAV-Dj/8, and AAV-Rh10 can eliminate 90% or more of latent HSV DNA in mouse models of orofacial infection, and up to 97% of latent HSV DNA in mouse models of genital infection. Using a pharmacological approach to reactivate latent HSV-1, we demonstrate that ganglionic viral load reduction leads to a significant decrease of viral shedding in treated female mice. While therapy is well tolerated, in some instances, we observe hepatotoxicity at high doses and subtle histological evidence of neuronal injury without observable neurological signs or deficits. Simplification of the regimen through use of a single serotype (AAV9) delivering single meganuclease targeting a duplicated region of the HSV genome, dose reduction, and use of a neuron-specific promoter each results in improved tolerability while retaining efficacy. These results reinforce the curative potential of gene editing for HSV disease.

Models of Herpes Simplex Virus Latency

Our current understanding of HSV latency is based on a variety of clinical observations, and in vivo, ex vivo, and in vitro model systems, each with unique advantages and drawbacks. The criteria for authentically modeling HSV latency include the ability to easily manipulate host genetics and biological pathways, as well as mimicking the immune response and viral pathogenesis in human infections. Although realistically modeling HSV latency is necessary when choosing a model, the cost, time requirement, ethical constraints, and reagent availability are also equally important. Presently, there remains a pressing need for in vivo models that more closely recapitulate human HSV infection. While the current in vivo, ex vivo, and in vitro models used to study HSV latency have limitations, they provide further insights that add to our understanding of latency. In vivo models have shed light on natural infection routes and the interplay between the host immune response and the virus during latency, while in vitro models have been invaluable in elucidating molecular pathways involved in latency. Below, we review the relative advantages and disadvantages of current HSV models and highlight insights gained through each.

Interferon lambda restricts herpes simplex virus skin disease by suppressing neutrophil-mediated pathology

Type III interferons (IFN-λ) are antiviral and immunomodulatory cytokines that have been best characterized in respiratory and gastrointestinal infections, but the effects of IFN-λ against skin infections have not been extensively investigated. We sought to define the skin-specific effects of IFN-λ against the highly prevalent human pathogen, herpes simplex virus (HSV). We infected mice lacking the IFN-λ receptor (Ifnlr1-/-), both the IFN-λ and the IFN-α/β receptors (Ifnar1-/-Ifnlr1-/-), or IFN-λ cytokines (Ifnl2/3-/-) and found that IFN-λ restricts the severity of HSV-1 and HSV-2 skin lesions without affecting viral loads. We used RNAseq to define IFN-λ- and IFN-β-induced transcriptional responses in primary mouse keratinocytes. Using conditional knockout mice, we found that IFN-λ signaling in both keratinocytes and neutrophils was necessary to control HSV-1 skin lesion severity and that IFN-λ signaling in keratinocytes suppressed CXCL9-mediated neutrophil recruitment to the skin. Furthermore, depleting neutrophils or blocking CXCL9 protected against severe HSV-1 skin lesions in Ifnlr1-/- mice. Altogether, our results suggest that IFN-λ plays an immunomodulatory role in the skin that restricts neutrophil-mediated pathology during HSV infection and suggests potential applications for IFN-λ in treating viral skin infections.IMPORTANCEType III interferons (IFN-λ) have been shown to have antiviral and immunomodulatory effects at epithelial barriers such as the respiratory and gastrointestinal tracts, but their effects on the skin have not been extensively investigated. We used mice lacking IFN-λ signaling to investigate the skin-specific effects of IFN-λ against the herpes simplex virus (HSV), which targets epithelial tissues to cause cold sores and genital herpes. We found that IFN-λ limited the severity of HSV skin lesions without affecting viral load and that this protective effect required IFN-λ signaling in both keratinocytes and neutrophils. We found that IFN-λ signaling in keratinocytes suppressed neutrophil recruitment to the skin and that depleting neutrophils protected against severe HSV skin lesions in the absence of IFN-λ. Altogether, our results suggest that IFN-λ plays an immunomodulatory role in the skin that restricts neutrophil-mediated pathology during HSV infection and suggests potential applications for IFN-λ in treating viral skin infections.

Application of the zebrafish model in human viral research

Viruses are a leading cause of infectious diseases. Well-developed animal models are valuable for understanding the immune responses to viral infections and the pathogenesis of viral diseases. Zebrafish is a commonly used small vertebrate model organism with strong reproductive ability, a short life cycle, and rapid embryonic development. Moreover, zebrafish and human genomes are highly similar; they have approximately 70 % homology in protein-coding genes, and 84 % of genes associated with human diseases have zebrafish counterparts. Recent years, different groups have developed zebrafish models for human viral infections and diseases, offering new insights into the molecular mechanisms of human viral pathogenesis as well as the development of antiviral strategies. The zebrafish model has become a simple and effective model system for understanding host-virus interaction. This review provides a comprehensive summary of the use of zebrafish models in human viral research, particularly in SARS-CoV-2.

Herpes simplex virus infection induces necroptosis of neurons and astrocytes in human fetal organotypic brain slice cultures

BACKGROUND

Herpes simplex virus (HSV) encephalitis (HSE) is a serious and potentially life-threatening disease, affecting both adults and newborns. Progress in understanding the virus and host factors involved in neonatal HSE has been hampered by the limitations of current brain models that do not fully recapitulate the tissue structure and cell composition of the developing human brain in health and disease. Here, we developed a human fetal organotypic brain slice culture (hfOBSC) model and determined its value in mimicking the HSE neuropathology in vitro.

METHODS

Cell viability and tissues integrity were determined by lactate dehydrogenase release in supernatant and immunohistological (IHC) analyses. Brain slices were infected with green fluorescent protein (GFP-) expressing HSV-1 and HSV-2. Virus replication and spread were determined by confocal microscopy, PCR and virus culture. Expression of pro-inflammatory cytokines and chemokines were detected by PCR. Cell tropism and HSV-induced neuropathology were determined by IHC analysis. Finally, the in situ data of HSV-infected hfOBSC were compared to the neuropathology detected in human HSE brain sections.

RESULTS

Slicing and serum-free culture conditions were optimized to maintain the viability and tissue architecture of ex vivo human fetal brain slices for at least 14 days at 37 °C in a CO2 incubator. The hfOBSC supported productive HSV-1 and HSV-2 infection, involving predominantly infection of neurons and astrocytes, leading to expression of pro-inflammatory cytokines and chemokines. Both viruses induced programmed cell death-especially necroptosis-in infected brain slices at later time points after infection. The virus spread, cell tropism and role of programmed cell death in HSV-induced cell death resembled the neuropathology of HSE.

CONCLUSIONS

We developed a novel human brain culture model in which the viability of the major brain-resident cells-including neurons, microglia, astrocytes and oligodendrocytes-and the tissue architecture is maintained for at least 2 weeks in vitro under serum-free culture conditions. The close resemblance of cell tropism, spread and neurovirulence of HSV-1 and HSV-2 in the hfOBSC model with the neuropathological features of human HSE cases underscores its potential to detail the pathophysiology of other neurotropic viruses and as preclinical model to test novel therapeutic interventions.

A fur plucking model to study herpes simplex virus reactivation and recurrent disease

Herpes simplex viruses (HSV-1 and HSV-2) most commonly cause ulcerative epithelial lesions (cold sores, genital herpes). Importantly, HSV establishes life-long persistent (latent) infection in sensory neurons. Reactivation from latency produces recurrent epithelial lesions, which constitute the greatest burden of HSV disease in people. The mechanisms that regulate latency and reactivation remain poorly understood, in part due to limitations in the animal models available for studying HSV reactivation. We have developed a simple and tractable model to induce HSV-1 and HSV-2 reactivation from latently infected sensory ganglia. We infected C57BL/6 mice with 1 × 106 FFU of HSV-1 (strain NS) or 500 FFU of HSV-2 (strain 333) on flank skin depilated by manual plucking. 35 days post-infection (dpi) we re-plucked the fur from the infected flank and observed recurrent lesions in the same dermatome as the primary infection. We detected HSV DNA in dermatome skin through 4 days post-re-plucking. We found that shaving the ipsilateral flank or plucking the contralateral flank did not induce recurrent skin lesions, suggesting that fur plucking is a specific stimulus that induces HSV reactivation. Further, we were able to induce multiple rounds of plucking induced recurrent disease, providing a model to investigate the lifelong nature of HSV infection. This new model provides a tractable system for studying pathogenic mechanisms of and therapeutic interventions against HSV reactivation and recurrent disease.

Animal Models in Eye Research: Focus on Corneal Pathologies

The eye is a complex sensory organ that enables visual perception of the world. The dysfunction of any of these tissues can impair vision. Conduction studies on laboratory animals are essential to ensure the safety of therapeutic products directly applied or injected into the eye to treat ocular diseases before eventually proceeding to clinical trials. Among these tissues, the cornea has unique homeostatic and regenerative mechanisms for maintaining transparency and refraction of external light, which are essential for vision. However, being the outermost tissue of the eye and directly exposed to the external environment, the cornea is particularly susceptible to injury and diseases. This review highlights the evidence for selecting appropriate animals to better understand and treat corneal diseases, which rank as the fifth leading cause of blindness worldwide. The development of reliable and human-relevant animal models is, therefore, a valuable research tool for understanding and translating fundamental mechanistic findings, as well as for assessing therapeutic potential in humans. First, this review emphasizes the unique characteristics of animal models used in ocular research. Subsequently, it discusses current animal models associated with human corneal pathologies, their utility in understanding ocular disease mechanisms, and their role as translational models for patients.

Unique Attributes of Guinea Pigs as New Models to Study Ocular Herpes Pathophysiology and Recurrence

Purpose

The objective of this study was to explore the ocular and systemic outcomes of herpes simplex virus type 1 (HSV-1) infection in guinea pigs, to monitor the spontaneous reactivation of the virus, and to assess the effectiveness of various treatments, drawing comparisons to conventional rabbit models.

Methods

Guinea pigs and rabbits were infected in the right corneas with differing doses and strains of HSV-1. Observations were made over a 71-day period, focusing on comparing ocular lesions, viral shedding patterns, and weight loss between the two animal models. Postinfection, the effectiveness of trifluridine ophthalmic drops, oral acyclovir, and valacyclovir was evaluated. The confirmation of viral infection was done through virus titer assay, fluorescein staining, and corneal imaging.

Results

Guinea pigs and rabbits manifested symptoms akin to human herpes stromal keratitis (HSK) when exposed to varying titers of viral suspension. Regardless of the initial viral load, all guinea pig groups demonstrated comparable ocular pathology, witnessing conditions like blepharitis and conjunctivitis within 3 days, progressing to severe conditions, including total corneal opacification and necrotizing keratitis. Tear film collection revealed nonsignificant differences in viral plaques between all groups. Notably, guinea pigs in the low-infection group experienced the most weight loss, although without significant differences. The replication of the same experiment on rabbits yielded consistent results in disease pathology across different groups, with occurrences of blepharitis and conjunctivitis. Interestingly, after initial resolution, guinea pigs presented a more frequent and broadly observed increase in disease score and corneal opacity, a phenomenon rarely seen in rabbits within the same timeframe. The effectiveness of 1% trifluridine was observed in mitigating ocular HSV-1 disease in both species, whereas oral acyclovir and valacyclovir were found to be detrimental and ineffective in guinea pigs but not in rabbits.

Conclusions

This study demonstrates the potential suitability of guinea pigs as new models for ocular HSV-1 investigations, filling a critical preclinical void of models capable of showcasing spontaneous HSV reactivation in the eye. The observed similarities and differences in the reactions of guinea pigs and rabbits to HSV-1 infection and treatments provide crucial insights, laying the foundation for future studies on ocular HSV pathogenesis, latency, and improved treatment options.

The Interplay of Genital Herpes with Cellular Processes: A Pathogenesis and Therapeutic Perspective

Genital herpes, primarily caused by herpes simplex virus-2 (HSV-2), remains a pressing global health concern. Its remarkable ability to intertwine with cellular processes, from harnessing host machinery for replication to subverting antiviral defenses like autophagy and programmed cell death, exemplifies the intricate interplay at the heart of its pathogenesis. While the biomedical community has extensively researched antiviral interventions, the efficiency of these strategies in managing HSV-2 remains suboptimal. Recognizing this, attention has shifted toward leveraging host cellular components to regulate HSV-2 replication and influence the cell cycle. Furthermore, innovative interventional strategies-including drug repurposing, microbivacs, connecting the host microbiome, and exploiting natural secondary metabolites-are emerging as potential game changers. This review summarizes the key steps in HSV-2 pathogenesis and newly discovered cellular interactions, presenting the latest developments in the field, highlighting existing challenges, and offering a fresh perspective on HSV-2's pathogenesis and the potential avenues for its treatment by targeting cellular proteins and pathways.

Interferon lambda restricts herpes simplex virus skin disease by suppressing neutrophil-mediated pathology

Type III interferons (IFN-λ) are antiviral and immunomodulatory cytokines that have been best characterized in respiratory and gastrointestinal infections, but the effects of IFN-λ against skin infections have not been extensively investigated. We sought to define the skin-specific effects of IFN-λ against the highly prevalent human pathogen herpes simplex virus (HSV). We infected mice lacking the IFN-λ receptor (Ifnlr1-/-), both the IFN-λ and the IFN-αβ receptor (Ifnar1-/- Ifnlr1-/-), or IFN-λ cytokines (Ifnl2/3-/-) and found that IFN-λ restricts the severity of HSV-1 and HSV-2 skin lesions, independent of a direct effect on viral load. Using conditional knockout mice, we found that IFN-λ signaling in both keratinocytes and neutrophils was necessary to control HSV-1 skin lesion severity, and that IFN-λ signaling in keratinocytes suppressed CXCL9-mediated neutrophil recruitment to the skin. Furthermore, depleting neutrophils or blocking CXCL9 protected against severe HSV-1 skin lesions in Ifnlr1-/- mice. Altogether, our results suggest that IFN-λ plays an immunomodulatory role in the skin that restricts neutrophil-mediated pathology during HSV infection, and suggest potential applications for IFN-λ in treating viral skin infections.

Mouse Models for Human Herpesviruses

More than one hundred herpesviruses have been isolated from different species so far, with nine infecting humans. Infections with herpesviruses are characterized by life-long latency and represent a significant challenge for human health. To investigate the consequences of infections and identify novel treatment options, in vivo models are of particular relevance. The mouse has emerged as an economical small animal model to investigate herpesvirus infections. However, except for herpes simplex viruses (HSV-1, HSV-2), human herpesviruses cannot infect mice. Three natural herpesviruses have been identified in mice: mouse-derived cytomegalovirus (MCMV), mouse herpesvirus 68 (MHV-68), and mouse roseolovirus (MRV). These orthologues are broadly used to investigate herpesvirus infections within the natural host. In the last few decades, immunocompromised mouse models have been developed, allowing the functional engraftment of various human cells and tissues. These xenograft mice represent valuable model systems to investigate human-restricted viruses, making them particularly relevant for herpesvirus research. In this review, we describe the various mouse models used to study human herpesviruses, thereby highlighting their potential and limitations. Emphasis is laid on xenograft mouse models, covering the development and refinement of immune-compromised mice and their application in herpesvirus research.

Inhibition Effects and Mechanisms of Marine Polysaccharide PSSD against Herpes Simplex Virus Type 2

Genital herpes is a common sexually transmitted disease mainly caused by herpes simplex virus type 2 (HSV-2), which can increase the risk of HIV transmission and is a major health problem in the world. Thus, it is of great significance to develop new anti-HSV-2 drugs with high efficiency and low toxicity. In this study, the anti-HSV-2 activities of PSSD, a marine sulfated polysaccharide, was deeply explored both in vitro and in vivo. The results showed that PSSD had marked anti-HSV-2 activities in vitro with low cytotoxicity. PSSD can directly interact with virus particles to inhibit the adsorption of virus to the cell surface. PSSD may also interact with virus surface glycoproteins to block virus-induced membrane fusion. Importantly, PSSD can significantly attenuate the symptoms of genital herpes and weight loss in mice after gel smear treatment, as well as reducing the titer of virus shedding in the reproductive tract of mice, superior to the effect of acyclovir. In summary, the marine polysaccharide PSSD possesses anti-HSV-2 effects both in vitro and in vivo, and has potential to be developed into a novel anti-genital herpes agent in the future.

Persistent inflammation and neuronal loss in the mouse brain induced by a modified form of attenuated herpes simplex virus type I

Herpes simplex virus-1 (HSV-1) is a widespread neurotropic virus that can reach the brain and cause a rare but acute herpes simplex encephalitis (HSE) with a high mortality rate. Most patients present with changes in neurological and behavioral status, and survivors suffer long-term neurological sequelae. To date, the pathogenesis leading to brain damage is still not well understood. HSV-1 induced encephalitis in the central nervous system (CNS) in animals are usually very diffuse and progressing rapidly, and mostly fatal, making the analysis difficult. Here, we established a mouse model of HSE via intracerebral inoculation of modified version of neural-attenuated strains of HSV-1 (deletion of ICP34.5 and inserting a strong promoter into the latency-associated transcript region), in which the LMR-αΔpA strain initiated moderate productive infection, leading to strong host immune and inflammatory response characterized by persistent microglia activation. This viral replication activity and prolonged inflammatory response activated signaling pathways in neuronal damage, amyloidosis, Alzheimer's disease, and neurodegeneration, eventually leading to neuronal loss and behavioral changes characterized by hypokinesia. Our study reveals detailed pathogenic processes and persistent inflammatory responses in the CNS and provides a controlled, mild and non-lethal HSE model for studying long-term neuronal injury and increased risk of neurodegenerative diseases due to HSV-1 infection.

Rodent models of postherpetic neuralgia: How far have we reached?

Background

Induced by varicella zoster virus (VZV), postherpetic neuralgia (PHN) is one of the common complications of herpes zoster (HZ) with refractory pain. Animal models play pivotal roles in disclosing the pain mechanisms and developing effective treatments. However, only a few rodent models focus on the VZV-associated pain and PHN.

Objective

To summarize the establishment and characteristics of popular PHN rodent models, thus offer bases for the selection and improvement of PHN models.

Design

In this review, we retrospect two promising PHN rodent models, VZV-induced PHN model and HSV1-induced PHN model in terms of pain-related evaluations, their contributions to PHN pathogenesis and pharmacology.

Results

Significant difference of two PHN models is the probability of virus proliferation; 2) Most commonly used pain evaluation of PHN model is mechanical allodynia, but pain-induced anxiety and other behaviours are worth noting; 3) From current PHN models, pain mechanisms involve changes in virus gene and host gene expression, neuroimmune-glia interactions and ion channels; 4) antiviral drugs and classical analgesics serve more on the acute stage of herpetic pain.

Conclusions

Different PHN models assessed by various pain evaluations combine to fulfil more comprehensive understanding of PHN.

A Guide to Preclinical Models of Zoster-Associated Pain and Postherpetic Neuralgia

Reactivation of latent varicella-zoster virus (VZV) causes herpes zoster (HZ), which is commonly accompanied by acute pain and pruritus over the time course of a zosteriform rash. Although the rash and associated pain are self-limiting, a considerable fraction of HZ cases will subsequently develop debilitating chronic pain states termed postherpetic neuralgia (PHN). How VZV causes acute pain and the mechanisms underlying the transition to PHN are far from clear. The human-specific nature of VZV has made in vivo modeling of pain following reactivation difficult to study because no single animal can reproduce reactivated VZV disease as observed in the clinic. Investigations of VZV pathogenesis following primary infection have benefited greatly from human tissues harbored in immune-deficient mice, but modeling of acute and chronic pain requires an intact nervous system with the capability of transmitting ascending and descending sensory signals. Several groups have found that subcutaneous VZV inoculation of the rat induces prolonged and measurable changes in nociceptive behavior, indicating sensitivity that partially mimics the development of mechanical allodynia and thermal hyperalgesia seen in HZ and PHN patients. Although it is not a model of reactivation, the rat is beginning to inform how VZV infection can evoke a pain response and induce long-lasting alterations to nociception. In this review, we will summarize the rat pain models from a practical perspective and discuss avenues that have opened for testing of novel treatments for both zoster-associated pain and chronic PHN conditions, which remain in critical need of effective therapies.

Aβ plaques do not protect against HSV-1 infection in a mouse model of familial Alzheimer's disease, and HSV-1 does not induce Aβ pathology in a model of late onset Alzheimer's disease

The possibility that the etiology of late onset Alzheimer's disease is linked to viral infections of the CNS has been actively debated in recent years. According to the antiviral protection hypothesis, viral pathogens trigger aggregation of Aβ peptides that are produced as a defense mechanism in response to infection to entrap and neutralize pathogens. To test the causative relationship between viral infection and Aβ aggregation, the current study examined whether Aβ plaques protect the mouse brain against Herpes Simplex Virus 1 (HSV-1) infection introduced via a physiological route and whether HSV-1 infection triggers formation of Aβ plaques in a mouse model of late-onset AD that does not develop Aβ pathology spontaneously. In aged 5XFAD mice infected via eye scarification, high density of Aβ aggregates did not improve survival time or rate when compared with wild type controls. In 5XFADs, viral replication sites were found in brain areas with a high density of extracellular Aβ deposits, however, no association between HSV-1 and Aβ aggregates could be found. To test whether HSV-1 triggers Aβ aggregation in a mouse model that lacks spontaneous Aβ pathology, 13-month-old hAβ/APOE4/Trem2*R47H mice were infected with HSV-1 via eye scarification with the McKrae HSV-1 strain, intracranial inoculation with McKrae, intracranial inoculation after priming with LPS for 6 weeks, or intracranial inoculation with high doses of McKrae or 17syn + strains that represent different degrees of neurovirulence. No signs of Aβ aggregation were found in any of the experimental groups. Instead, extensive infiltration of peripheral leukocytes was observed during the acute stage of HSV-1 infection, and phagocytic activity of myeloid cells was identified as the primary defense mechanism against HSV-1. The current results argue against a direct causative relationship between HSV-1 infection and Aβ pathology.

Understanding global changes of the mouse brain proteome after vaginal infection with HSV-2 using a label-free shotgun approach

Herpes simplex virus type 2 (HSV-2) is a common human pathogen that establishes lifelong latency in neurons of the nervous system. The number of severe central nervous system infections caused by the virus has increased recently. However, the pathogenesis of HSV-2 infection in the nervous system is not fully understood. Here, we demonstrated global proteomic changes in the brain tissue in BALB/c mice vaginally infected with HSV-2. Data are available via ProteomeXchange with identifier PXD034186. A total of 249 differentially expressed proteins were identified in infected brain tissue. The GO and KEGG enrichment analysis of these proteins indicated that they were mainly involved in the regulation of synapse formation and synaptic excitability. In addition, genes affecting autophagy, the development of other neurodegenerative diseases, and signaling pathways relevant to other neurologic diseases were identified. Additional experiments, comparing the brain tissue of asymptomatic and symptomatic mice showed a differential expression of proteins involved in synapse formation and synaptic transmission. Others were involved in autophagy, addiction, and signaling pathways of other neurologic diseases. These results suggest that changes in synaptic structure and function, as well as autophagy, may be related to the development of neurologic abnormalities that follow HSV-2 infection. We also identified a protein GluN2A encoded by Grin2a was continuously expressed at high levels after infection. We propose that GluN2A may be a key molecule in the pathogenesis of HSV-2-induced neurologic diseases.

The Inhibition of DNA Viruses by the Amphibian Antimicrobial Peptide Temporin G: A Virological Study Addressing HSV-1 and JPCyV

Herpes simplex virus type-1 (HSV-1) and John Cunningham polyomavirus (JCPyV) are widely distributed DNA viruses causing mainly asymptomatic infection, but also mild to very severe diseases, especially when these viruses reach the brain. Some drugs have been developed to inhibit HSV-1 replication in host cells, but their prolonged use may induce resistance phenomena. In contrast, to date, there is no cure for JCPyV. The search for alternative drugs that can reduce viral infections without undermining the host cell is moving toward antimicrobial peptides (AMPs) of natural occurrence. These include amphibian AMPs belonging to the temporin family. Herein, we focus on temporin G (TG), showing that it strongly affects HSV-1 replication by acting either during the earliest stages of its life cycle or directly on the virion. Computational studies have revealed the ability of TG to interact with HSV-1 glycoprotein B. We also found that TG reduced JCPyV infection, probably affecting both the earliest phases of its life cycle and the viral particle, likely through an interaction with the viral capsid protein VP1. Overall, our results are promising for the development of short naturally occurring peptides as antiviral agents used to counteract diseases related to HSV-1 and JCPyV.

Guinea Pig and Mouse Models for Genital Herpes Infection

This article describes procedures for two preclinical animal models for genital herpes infection. The guinea pig model shares many features of genital herpes in humans, including a natural route of inoculation, self-limiting primary vulvovaginitis, spontaneous recurrences, symptomatic and subclinical shedding of HSV-2, and latent infection of the associated sensory ganglia (lumbosacral dorsal root ganglia, DRG). Many humoral and cytokine responses to HSV-2 infection in the guinea pig have been characterized; however, due to the limited availability of immunological reagents, assessments of cellular immune responses are lacking. In contrast, the mouse model has been important in assessing cellular immune responses to herpes infection. Both the mouse and guinea pig models have been extremely useful for evaluating preventative and immunotherapeutic approaches for controlling HSV infection and recurrent disease. In this article, we describe procedures for infecting guinea pigs and mice with HSV-2, scoring subsequent genital disease, and measuring replicating virus to confirm infection. We also provide detailed protocols for dissecting and isolating DRG (the site of HSV-2 latency), quantifying HSV-2 genomic copies in DRG, and assessing symptomatic and subclinical shedding of HSV-2 in the vagina. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Primary and recurrent genital herpes infection in the guinea pig model Support Protocol 1: Blood collection via lateral saphenous vein or by cardiac puncture after euthanasia Support Protocol 2: Dissection and isolation of dorsal root ganglia from guinea pigs Support Protocol 3: PCR amplification and quantification of HSV-2 genomic DNA from samples Basic Protocol 2: Primary genital herpes infection in the mouse model Alternate Protocol: Flank infection with HSV-2 in the mouse model Support Protocol 4: Dissection and isolation of mouse dorsal root ganglia.

MAMDC2, a gene highly expressed in microglia in experimental models of Alzheimers Disease, positively regulates the innate antiviral response during neurotropic virus infection

Microglia, as central nervous system (CNS)-resident macrophages, are the first line of defense against neurotropic virus infection, the immune response of which is implicated in numerous CNS diseases, including Alzheimer's disease (AD). Indeed, the infectious hypothesis for AD has long been recognized, of note herpes simplex virus type 1 (HSV-1), the most common human neurotropic virus. However, the mechanism linking HSV-1 and AD remains obscure. In this study, we analyzed the transcriptome data of microglia in AD mice. We found that MAM domain containing 2 (MAMDC2) is significantly upregulated in microglia isolated from both a series of AD mice established by numerous genetic strategies and mice with HSV-1 infection. Mamdc2-deficient (Mamdc2^-/-) mice are susceptible to HSV-1 infection and show an impaired type I interferon (I-IFN)-based innate antiviral response upon neurotropic HSV-1 infection. The in vitro experiments suggest a similar result. Moreover, lentivirus-mediated overexpression of Mamdc2 in mouse brains enhances the innate antiviral response in microglia and ameliorates herpes simplex encephalitis (HSE) symptoms. Mechanistically, MAMDC2 interacts with STING via its first MAM domain within and enhances the polymerization of STING, activating downstream TBK1-IRF3 signaling to facilitate the expression of I-IFNs. The sulfated glycosaminoglycan-mediated polymerization of STING also largely depends on MAMDC2. Our study uncovers the function of MAMDC2 in the innate antiviral response in microglia, revealing a potential mechanism linking HSV-1 and AD, especially the contribution of Mamdc2 overexpression to the upregulation of I-IFN in the AD brain.

Clinical, neuropathological, and immunological short- and long-term feature of a mouse model mimicking human herpes virus encephalitis

Herpes simplex encephalitis (HSE) is one of the most serious diseases of the nervous system in humans. However, its pathogenesis is still only poorly understood. Although several mouse models of predominantly herpes simplex virus 1 (HSV-1) infections mimic different crucial aspects of HSE, central questions remain unanswered. They comprise the specific temporofrontal tropism, viral spread within the central nervous system (CNS), as well as potential molecular and immunological barriers that drive virus into latency while only rarely resulting in severe HSE. We have recently proposed an alternative mouse model by using a pseudorabies virus (PrV) mutant that more faithfully represents the striking features of human HSE: temporofrontal meningoencephalitis with few severely, but generally only moderately to subclinically affected mice as well as characteristic behavioral abnormalities. Here, we characterized this animal model using 6- to 8-week-old female CD-1 mice in more detail. Long-term investigation over 6 months consistently revealed a biphasic course of infection accompanied by recurring clinical signs including behavioral alterations and mainly mild meningoencephalitis restricted to the temporal and frontal lobes. By histopathological and immunological analyses, we followed the kinetics and spatial distribution of inflammatory lesions as well as the underlying cytokine expression in the CNS over 21 days within the acute phase of infection. Affecting the temporal lobes, the inflammatory infiltrate was composed of lymphocytes and macrophages showing a predominantly lymphocytic shift 15 days after infection. A strong increase was observed in cytokines CXCL10, CCL2, CCL5, and CXCL1 recruiting inflammatory cells to the CNS. Unlike the majority of infected mice, strongly affected animals demonstrated extensive temporal lobe edema, which is typically present in severe human HSE cases. In summary, these results support the validity of our animal model for in-depth investigation of HSE pathogenesis.

The Chinese Herbal Prescription JieZe-1 Inhibits Membrane Fusion and the Toll-like Receptor Signaling Pathway in a Genital Herpes Mouse Model

Chinese herbal prescription JieZe-1 is effective for genital herpes with no visible adverse effects clinically. It showed an excellent anti-HSV-2 effect in vitro. However, its mechanism of anti-HSV-2 effect in vivo remains unclear. This study was designed to evaluate the anti-HSV-2 effect of JieZe-1 and berberine in a genital herpes mouse model and explore the underlying mechanism. The fingerprint of JieZe-1 was determined by high-performance liquid chromatography. First, we optimized a mouse model of genital herpes. Next, the weight, symptom score, morphological changes, viral load, membrane fusion proteins, critical proteins of the Toll-like receptor signaling pathway, cytokines, and immune cells of vaginal tissue in mice at different time points were measured. Finally, we treated the genital herpes mouse model with JieZe-1 gel (2.5, 1.5, and 0.5 g/ml) and tested the above experimental indexes at 12 h and on the 9th day after modeling. JieZe-1 improved the symptoms, weight, and histopathological damage of genital herpes mice, promoted the keratin repair of tissues, and protected organelles to maintain the typical morphology of cells. It downregulated the expression of membrane fusion proteins, critical proteins of the Toll-like receptor signaling pathway, cytokines, and immune cells. The vaginal, vulvar, and spinal cord viral load and vaginal virus shedding were also significantly reduced. In summary, JieZe-1 shows significant anti-HSV-2 efficacy in vivo. The mechanism is related to the inhibition of membrane fusion, the Toll-like receptor signaling pathway, inflammatory cytokines, and cellular immunity. However, berberine, the main component of JieZe-1 monarch medicine, showed no efficacy at a concentration of 891.8 μM (0.3 mg/ml).

A truncated glycoprotein G vaccine formulated with Advax-CpG adjuvant provides protection of mice against genital herpes simplex virus 2 infection

Herpes simplex virus type 2 (HSV-2) is a common sexually transmitted disease that affects approximately 500 million individuals globally. There is currently no approved vaccine to prevent HSV-2 infection. EXCT4 is a truncated form of the mature glycoprotein G-2 (mgG-2) that unlike full mature form is secreted by expressing cells enabling it to be rapidly scaled up for production. The current study examined whether EXCT4 immunity in mice could be further enhanced through use of adjuvants. EXCT4 formulated with Advax-CpG adjuvant induced a strong Th1-type immune response characterized by interferon gamma (IFN-γ) and protected animals against a lethal genital challenge with HSV-2. This response was associated with reduced viral load in vaginal washes, spinal cord, and dorsal root ganglia. Together the results provide proof of concept that EXCT4 formulated with Advax-CpG adjuvant is a promising HSV-2 vaccine candidate warranting further investigation.

A novel bioluminescent herpes simplex virus 1 for in vivo monitoring of herpes simplex encephalitis

Herpes simplex virus 1 (HSV-1) is responsible for herpes simplex virus encephalitis (HSE), associated with a 70% mortality rate in the absence of treatment. Despite intravenous treatment with acyclovir, mortality remains significant, highlighting the need for new anti-herpetic agents. Herein, we describe a novel neurovirulent recombinant HSV-1 (rHSV-1), expressing the fluorescent tdTomato and Gaussia luciferase (Gluc) enzyme, generated by the Clustered regularly interspaced short palindromic repeats (CRISPR)—CRISPR-associated protein 9 (Cas9) (CRISPR-Cas9) system. The Gluc activity measured in the cell culture supernatant was correlated (P = 0.0001) with infectious particles, allowing in vitro monitoring of viral replication kinetics. A significant correlation was also found between brain viral titers and Gluc activity in plasma (R² = 0.8510, P < 0.0001) collected from BALB/c mice infected intranasally with rHSV-1. Furthermore, evaluation of valacyclovir (VACV) treatment of HSE could also be performed by analyzing Gluc activity in mouse plasma samples. Finally, it was also possible to study rHSV-1 dissemination and additionally to estimate brain viral titers by in vivo imaging system (IVIS). The new rHSV-1 with reporter proteins is not only as a powerful tool for in vitro and in vivo antiviral screening, but can also be used for studying different aspects of HSE pathogenesis.

Local Immune Control of Latent Herpes Simplex Virus Type 1 in Ganglia of Mice and Man

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen. HSV-1 genomes persist in trigeminal ganglia neuronal nuclei as chromatinized episomes, while epithelial cells are typically killed by lytic infection. Fluctuations in anti-viral responses, broadly defined, may underlay periodic reactivations. The ganglionic immune response to HSV-1 infection includes cell-intrinsic responses in neurons, innate sensing by several cell types, and the infiltration and persistence of antigen-specific T-cells. The mechanisms specifying the contrasting fates of HSV-1 in neurons and epithelial cells may include differential genome silencing and chromatinization, dictated by variation in access of immune modulating viral tegument proteins to the cell body, and protection of neurons by autophagy. Innate responses have the capacity of recruiting additional immune cells and paracrine activity on parenchymal cells, for example via chemokines and type I interferons. In both mice and humans, HSV-1-specific CD8 and CD4 T-cells are recruited to ganglia, with mechanistic studies suggesting active roles in immune surveillance and control of reactivation. In this review we focus mainly on HSV-1 and the TG, comparing and contrasting where possible observational, interventional, and in vitro studies between humans and animal hosts.

Embryo-Engineered Nonhuman Primate Models: Progress and Gap to Translational Medicine

Animal models of human diseases are vital in better understanding the mechanism of pathogenesis and essential for evaluating and validating potential therapeutic interventions. As close relatives of humans, nonhuman primates (NHPs) play an increasingly indispensable role in advancing translational medicine research. In this review, we summarized the progress of NHP models generated by embryo engineering, analyzed their unique advantages in mimicking clinical patients, and discussed the remaining gap between basic research of NHP models to translational medicine.

Revisiting Koch's postulate to determine the plausibility of viral transmission by human milk

As breastfeeding is of utmost importance for child development and survival, identifying whether breast milk is a route of transmission for human viruses is critical. Based on the principle of Koch's postulate, we propose an analytical framework to determine the plausibility of viral transmission by breast milk. This framework is based on five criteria: viral infection in children receiving breast milk from infected mothers; the presence of virus, viral antigen, or viral genome in the breast milk of infected mothers; the evidence for the virus in breast milk being infectious; the attempts to rule out other transmission modalities; and the reproduction of viral transmission by oral inoculation in an animal model. We searched for evidence in published reports to determine whether the 5 criteria are fulfilled for 16 human viruses that are suspected to be transmissible by breast milk. We considered breast milk transmission is proven if all 5 criteria are fulfilled, as probable if 4 of the 5 criteria are met, as possible if 3 of the 5 criteria are fulfilled, and as unlikely if less than 3 criteria are met. Only five viruses have proven transmission through breast milk: human T-cell lymphotropic virus 1, human immunodeficiency virus, human cytomegalovirus, dengue virus, and Zika virus. The other 11 viruses fulfilled some but not all criteria and were categorized accordingly. Our framework analysis is useful for guiding public health recommendations and for identifying knowledge gaps amenable to original experiments.

Combination of long- and short-read sequencing fully resolves complex repeats of herpes simplex virus 2 strain MS complete genome

Herpes simplex virus serotype 2 (HSV-2) is a ubiquitous human pathogen that causes recurrent genital infections and ulcerations. Many HSV-2 strains with different biological properties have been identified, but only the genomes of HSV-2 strains HG52, SD90e and 333 have been reported as complete and fully characterized sequences. We de novo assembled, annotated and manually curated the complete genome sequence of HSV-2 strain MS, a highly neurovirulent strain, originally isolated from a multiple sclerosis patient. We resolved both DNA ends, as well as the complex inverted repeats regions present in HSV genomes, usually undisclosed in previous published partial herpesvirus genomes, using long reads from Pacific Biosciences (PacBio) technology. Additionally, we identified isomeric genomes by determining the alternative relative orientation of unique fragments in the genome of the sequenced viral population. Illumina short-read sequencing was crucial to examine genetic variability, such as nucleotide polymorphisms, insertion/deletions and sequence determinants of strain-specific virulence factors. We used Illumina data to fix two disrupted open reading frames found in coding homopolymers after PacBio assembly. These results support the combination of long- and short-read sequencing technologies as a precise and effective approach for the accurate de novo assembly and curation of complex microbial genomes.

Alzheimer's disease-associated β-amyloid does not protect against herpes simplex virus 1 infection in the mouse brain

Alzheimer’s disease (AD) is a devastating fatal neurodegenerative disease. An alternative to the amyloid cascade hypothesis is that a viral infection is key to the etiology of late-onset AD, with β-amyloid (Aβ) peptides playing a protective role. In the current study, young 5XFAD mice that overexpress mutant human amyloid precursor protein with the Swedish, Florida, and London familial AD mutations were infected with one of two strains of herpes simplex virus 1 (HSV-1), 17syn+ and McKrae, at three different doses. Contrary to previous work, 5XFAD genotype failed to protect mice against HSV-1 infection. The region- and cell-specific tropisms of HSV-1 were not affected by the 5XFAD genotype, indicating that host–pathogen interactions were not altered. Seven- to ten-month-old 5XFAD animals in which extracellular Aβ aggregates were abundant showed slightly better survival rate relative to their wild-type (WT) littermates, although the difference was not statistically significant. In these 5XFAD mice, HSV-1 replication centers were partially excluded from the brain areas with high densities of Aβ aggregates. Aβ aggregates were free of HSV-1 viral particles, and the limited viral invasion to areas with a high density of Aβ aggregates was attributed to phagocytic activity of reactive microglia. In the oldest mice (12–15 months old), the survival rate did not differ between 5XFAD and WT littermates. While the current study questions the antiviral role of Aβ, it neither supports nor refutes the viral etiology hypothesis of late-onset AD.

The Potential Role of Herpes Simplex Virus Type 1 and Neuroinflammation in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease affecting ~50 million people worldwide. To date, there is no cure and current therapies have not been effective in delaying disease progression. Therefore, there is an urgent need for better understanding of the pathogenesis of AD and to rethink possible therapies. Herpes simplex virus type 1 (HSV1) has recently received growing attention for its potential role in sporadic AD. The virus is a ubiquitous human pathogen that infects mucosal epithelia and invades the peripheral nervous system (PNS) of its host to establish a reactivable, latent infection. Upon reactivation, HSV1 spreads back to the epithelium and initiates a new infection, causing epithelial lesions. Occasionally, the virus spreads from the PNS to the brain after reactivation. In this review, we discuss current work on the pathogenesis of AD and summarize research results that support a potential role for HSV1 in the infectious hypothesis of AD. We also highlight recent findings on the neuroinflammatory response, which has been proposed to be the main driving force of AD, starting early in the course of the disease. Relevant rodent models to study neuroinflammation in AD and novel therapeutic approaches are also discussed. Throughout this review, we focus on several aspects of HSV1 pathogenesis, including its primary role as an invader of the PNS, that should be considered in the etiology of AD. We also point out some of the contradictory data and remaining knowledge gaps that require further research to finally fully understand the cause of AD in humans.

Polluted Air Exposure Compromises Corneal Immunity and Exacerbates Inflammation in Acute Herpes Simplex Keratitis

Air pollution is a serious environmental issue worldwide in developing countries’ megacities, affecting the population’s health, including the ocular surface, by predisposing or exacerbating other ocular diseases. Herpes simplex keratitis (HSK) is caused by the herpes simplex virus type 1 (HSV-1). The primary or recurring infection in the ocular site causes progressive corneal scarring that may result in visual impairment. The present study was designed to study the immunopathological changes of acute HSK under urban polluted air, using the acute HSK model combined with an experimental urban polluted air exposure from Buenos Aires City. We evaluated the corneal clinical outcomes, viral DNA and pro-inflammatory cytokines by RT-PCR and ELISA assays, respectively. Then, we determined the innate and adaptive immune responses in both cornea and local lymph nodes after HSV-1 corneal by immunofluorescence staining and flow cytometry. Our results showed that mice exposed to polluted air develop a severe form of HSK with increased corneal opacity, neovascularization, HSV-1 DNA and production of TNF-α, IL-1β, IFN-γ, and CCL2. A high number of corneal resident immune cells, including activated dendritic cells, was observed in mice exposed to polluted air; with a further significant influx of bone marrow-derived cells including GR1+ cells (neutrophils and inflammatory monocytes), CD11c+ cells (dendritic cells), and CD3+ (T cells) during acute corneal HSK. Moreover, mice exposed to polluted air showed a predominant Th1 type T cell response over Tregs in local lymph nodes during acute HSK with decreased corneal Tregs. These findings provide strong evidence that urban polluted air might trigger a local imbalance of innate and adaptive immune responses that exacerbate HSK severity. Taking this study into account, urban air pollution should be considered a key factor in developing ocular inflammatory diseases.

Herpes simplex virus-1 KOS-63 strain is virulent and causes titer-dependent corneal nerve damage and keratitis

To investigate the acute clinical, immunological, and corneal nerve changes following corneal HSV-1 KOS-63 strain inoculation. Corneas of C57BL/6 mice were inoculated with either low dose (Ld) or high dose (Hd) HSV-1 KOS-63 or culture medium. Clinical evaluation was conducted up to 7 days post inoculation (dpi). Viral titers were assessed by standard plaque assay. Excised corneas were stained for CD45 and beta-III tubulin. Corneal flow cytometry was performed to assess changes in leukocyte subpopulations. Corneal sensation was measured using a Cochet-Bonnet esthesiometer. Naïve, sham-infected (post scarification), and McKrae-infected C57BL/6 corneas served as two negative and positive controls, respectively. Compared to Ld infected mice, Hd HSV-1 KOS-63 demonstrated higher incidence of corneal opacity (1.5 ×) and neovascularization (2.6 × ; p < 0.05). At 7 dpi Hd infected mice showed more severe corneal opacity (2.23 vs. 0.87; p = 0.0003), neovascularization (6.00 vs. 0.75; p < 0.0001), and blepharitis (3.11 vs. 2.06; p = 0.001) compared to the Ld group. At 3 dpi epitheliopathy was significantly larger in the Hd group (23.59% vs. 3.44%; p = 0.001). Similarly, corneal opacity was significantly higher in Hd McKrae-infected corneas as compared with Ld McKrae-infected corneas at 3 and 5 dpi. No significant corneal opacity, neovascularization, blepharitis, and epitheliopathy were observed in naïve or sham-infected mice. Higher viral titers were detected in corneas (1 and 3 dpi) and trigeminal ganglia (TG) (3 and 5 dpi) in Hd versus Ld KOS-63 groups (p < 0.05). Leukocyte density showed a gradual increase over time from 1 to 7 dpi in both KOS-63 and McKrae-infected corneas. Corneal flow cytometric analysis (3 dpi) demonstrated a higher percentage of Gr-1 + (71.6 vs. 26.3) and CD11b + (90.6 vs. 41.1) cells in Hd versus Ld KOS-63 groups. Corneal nerve density significantly decreased in both Hd KOS-63 and Hd McKrae infected corneas in comparison with naïve and sham-infected corneas. At 3 dpi corneal nerve density was lower in the Hd versus Ld KOS-63 groups (16.79 vs. 57.41 mm/mm2; p = 0.004). Corneal sensation decreased accordingly at 5 and 7 dpi in both Ld and Hd KOS-63-infected mice. Corneal inoculation with HSV-1 KOS-63 strain shows acute keratitis and nerve degeneration in a dose-dependent fashion, demonstrating virulence of this strain.

Dot1l Aggravates Keratitis Induced by Herpes Simplex Virus Type 1 in Mice via p38 MAPK-Mediated Oxidative Stress

BACKGROUND

Disruptor of telomeric silencing 1-like (Dot1l) plays a vital role in biological processes as a well-known methyltransferase. However, its role in herpes simplex virus type 1- (HSV-1-) infected keratitis remains unclear.

METHODS

In vitro and in vivo models were assessed to investigate the role of Dot1l in HSV-1 induced keratitis. C57BL/6 mice corneas were infected with HSV-1 for different days, with or without Dot1l inhibitor, to demonstrate the regulation of Dot1l in herpes simplex keratitis (HSK). Human corneal epithelial (HCE) cells were cultured and infected with HSV-1 to identify the molecular mechanisms involved.

RESULTS

In this study, we found that Dot1l was positively related to HSK. Inhibition of Dot1l with EPZ004777 (EPZ) alleviated corneal injury, including oxidative stress and inflammation in vivo. Similarly, the inhibition of Dot1l with either EPZ or small interfering RNA (siRNA) showed an inhibitory effect on HSV-1-induced oxidative stress and inflammation in HCE cells. Moreover, our study revealed that the expression of p38 MAPK was elevated after HSV-1 infection in HCE cells, and the inhibition of Dot1l could reduce the increased expression of p38 MAPK induced by HSV-1 infection in vivo and in vitro.

CONCLUSION

Our results demonstrated that the inhibition of Dot1l alleviated corneal oxidative stress and inflammation by inhibiting ROS production through the p38 MAPK pathway in HSK. These findings indicated that Dot1l might be a valuable therapeutic target for HSK.

Group 1 innate lymphoid-cell-derived interferon-γ maintains anti-viral vigilance in the mucosal epithelium

The oropharyngeal mucosa serves as a perpetual pathogen entry point and a critical site for viral replication and spread. Here, we demonstrate that type 1 innate lymphoid cells (ILC1s) were the major immune force providing early protection during acute oral mucosal viral infection. Using intravital microscopy, we show that ILC1s populated and patrolled the uninfected labial mucosa. ILC1s produced interferon-γ (IFN-γ) in the absence of infection, leading to the upregulation of key antiviral genes, which were downregulated in uninfected animals upon genetic ablation of ILC1s or antibody-based neutralization of IFN-γ. Thus, tonic IFN-γ production generates increased oral mucosal viral resistance even before infection. Our results demonstrate barrier-tissue protection through tissue surveillance in the absence of rearranged-antigen receptors and the induction of an antiviral state during homeostasis. This aspect of ILC1 biology raises the possibility that these cells do not share true functional redundancy with other tissue-resident lymphocytes.

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.

The Role of VP16 in the Life Cycle of Alphaherpesviruses

The protein encoded by the UL48 gene of alphaherpesviruses is named VP16 or alpha-gene-transactivating factor (α-TIF). In the early stage of viral replication, VP16 is an important transactivator that can activate the transcription of viral immediate-early genes, and in the late stage of viral replication, VP16, as a tegument, is involved in viral assembly. This review will explain the mechanism of VP16 acting as α-TIF to activate the transcription of viral immediate-early genes, its role in the transition from viral latency to reactivation, and its effects on viral assembly and maturation. In addition, this review also provides new insights for further research on the life cycle of alphaherpesviruses and the role of VP16 in the viral life cycle.

Innate immunity and alpha/gammaherpesviruses: first impressions last a lifetime

Innate immune system is considered the first line of defense during viral invasion, with the wealth of the literature demonstrating innate immune control of diverse viruses during acute infection. What is far less clear is the role of innate immune system during chronic virus infections. This short review focuses on alphaherpesviruses and gammaherpesviruses, two highly prevalent herpesvirus subfamilies that, following a brief, once in a lifetime period of acute lytic infection, establish life-long latent infection that is characterized by sporadic reactivation in an immunocompetent host. In spite of many similarities, these two viral families are characterized by distinct cellular tropism and pathogenesis. Here we focus on the published in vivo studies to review known interactions of these two viral subfamilies with the innate immunity of the intact host, both during acute and, particularly, chronic virus infection.

Use of the Guinea pig model of genital herpes to evaluate vaccines and antivirals: Review

Herpes simplex virus (HSV) infections type 1 (HSV-1) and type 2 (HSV-2) are common throughout the world. Infections are lifelong and may produce both acute and recurrent vesiculoulcerative disease as well as more severe diseases. Despite disappointing results from recent HSV vaccine trials new vaccines and more potent antiviral therapies continue to be developed. These newer approaches require initial evaluations in animal models. In this review I have briefly described some of the models available and then more thoroughly describe the guinea pig model of acute and recurrent genital herpes infections. As discussed, the guinea pig model most closely mimics human disease and provides several important endpoints for evaluating vaccines and antivirals.

Vaccines against Genital Herpes: Where Are We?

Genital herpes is a venereal disease caused by herpes simplex virus (HSV). Although HSV symptoms can be reduced with antiviral drugs, there is no cure. Moreover, because HSV infected individuals are often unaware of their infection, it is highly likely that they will transmit HSV to their sexual partner. Once infected, an individual has to live with HSV for their entire life, and HSV infection can lead to meningitis, encephalitis, and neonatal herpes as a result of vertical transmission. In addition, HSV infection increases the rates of human immunodeficiency virus (HIV) infection and transmission. Because of the high burden of genital herpes, HSV vaccines have been developed, but none have been very successful. In this review, we discuss the current status of genital herpes vaccine development.

The Mutation of the Genes Related to Neurovirulence in HSV-2 Produces an Attenuated Phenotype in Mice

HSV-2 (Herpes simplex virus type 2) is a critical viral agent that mainly causes genital herpes and life-long latent infection in the dorsal root ganglia. Gene modification via CRISPR/Cas9 Clustered regularly interspaced short palindromic repeat sequences/CRISPR associated 9) was used here to construct HSV-2 mutant strains through the deletion of fragments of the RL1 (Repeat Long element 1) and/or LAT (Latency-associated Transcript) genes. The HSV-2 mutant strains LAT-HSV-2 and RL1-LAT-HSV-2 present different biological properties. The proliferation of RL1-LAT-HSV-2 in nerve cells was decreased significantly, and the plaques induced by RL1-LAT-HSV-2 in Vero cells were smaller than those induced by LAT-HSV-2 mutant and wild-type strains. The observation of mice infected with these two mutants compared to mice infected with the wild-type strain indicated that the mutant RL1-LAT-HSV-2 has an attenuated phenotype with reduced pathogenicity during both acute and latent infections and induces a stronger specific immune response than the wild-type strain, whereas the attenuation effect was not found in mice infected with the LAT-HSV-2 mutant containing the LAT gene deletion. However, the simultaneous mutation of both the RL1 and LAT genes did not completely restrict viral proliferation in nerve cells, indicating that multiple HSV genes are involved in viral replication in the neural system. This work suggests that the HSV-2 genes RL1 and/or LAT might be involved in the virulence mechanisms in mouse infections.

The Role of Herpes Simplex Virus Type 1 Infection in Demyelination of the Central Nervous System

Herpes simplex type 1 (HSV-1) is a neurotropic virus that infects the peripheral and central nervous systems. After primary infection in epithelial cells, HSV-1 spreads retrogradely to the peripheral nervous system (PNS), where it establishes a latent infection in the trigeminal ganglia (TG). The virus can reactivate from the latent state, traveling anterogradely along the axon and replicating in the local surrounding tissue. Occasionally, HSV-1 may spread trans-synaptically from the TG to the brainstem, from where it may disseminate to higher areas of the central nervous system (CNS). It is not completely understood how HSV-1 reaches the CNS, although the most accepted idea is retrograde transport through the trigeminal or olfactory tracts. Once in the CNS, HSV-1 may induce demyelination, either as a direct trigger or as a risk factor, modulating processes such as remyelination, regulation of endogenous retroviruses, or molecular mimicry. In this review, we describe the current knowledge about the involvement of HSV-1 in demyelination, describing the pathways used by this herpesvirus to spread throughout the CNS and discussing the data that suggest its implication in demyelinating processes.

Vaccines to prevent genital herpes

Genital herpes increases the risk of acquiring and transmitting Human Immunodeficiency Virus (HIV), is a source of anxiety for many about transmitting infection to intimate partners, and is life-threatening to newborns. A vaccine that prevents genital herpes infection is a high public health priority. An ideal vaccine will prevent both genital lesions and asymptomatic subclinical infection to reduce the risk of inadvertent transmission to partners, will be effective against genital herpes caused by herpes simplex virus types 1 and 2 (HSV-1, HSV-2), and will protect against neonatal herpes. Three phase 3 human trials were performed over the past 20 years that used HSV-2 glycoproteins essential for virus entry as immunogens. None achieved its primary endpoint, although each was partially successful in either delaying onset of infection or protecting a subset of female subjects that were HSV-1 and HSV-2 uninfected against HSV-1 genital infection. The success of future vaccine candidates may depend on improving the predictive value of animal models by requiring vaccines to achieve near-perfect protection in these models and by using the models to better define immune correlates of protection. Many vaccine candidates are under development, including DNA, modified mRNA, protein subunit, killed virus, and attenuated live virus vaccines. Lessons learned from prior vaccine studies and select candidate vaccines are discussed, including a trivalent nucleoside-modified mRNA vaccine that our laboratory is pursuing. We are optimistic that an effective vaccine for prevention of genital herpes will emerge in this decade.

Intrinsically disordered regions are abundant in simplexvirus proteomes and display signatures of positive selection

Whereas the majority of herpesviruses co-speciated with their mammalian hosts, human herpes simplex virus 2 (HSV-2, genus Simplexvirus) most likely originated from the cross-species transmission of chimpanzee herpesvirus 1 to an ancestor of modern humans. We exploited the peculiar evolutionary history of HSV-2 to investigate the selective events that drove herpesvirus adaptation to a new host. We show that HSV-2 intrinsically disordered regions (IDRs)-that is, protein domains that do not adopt compact three-dimensional structures-are strongly enriched in positive selection signals. Analysis of viral proteomes indicated that a significantly higher portion of simplexvirus proteins is disordered compared with the proteins of other human herpesviruses. IDR abundance in simplexvirus proteomes was not a consequence of the base composition of their genomes (high G + C content). Conversely, protein function determines the IDR fraction, which is significantly higher in viral proteins that interact with human factors. We also found that the average extent of disorder in herpesvirus proteins tends to parallel that of their human interactors. These data suggest that viruses that interact with fast-evolving, disordered human proteins, in turn, evolve disordered viral interactors poised for innovation. We propose that the high IDR fraction present in simplexvirus proteomes contributes to their wider host range compared with other herpesviruses.

Model of vaccine efficacy against HSV-2 superinfection of HSV-1 seropositive mice demonstrates protection by antibodies mediating cellular cytotoxicity

A majority of the world’s population is infected with HSV-1, highlighting the need for vaccines that are effective in HSV-1-seropositive hosts. We established a superinfection model by infecting mice intranasally with a sublethal dose of HSV-1, which results in high rates of seropositive, latently infected mice susceptible to HSV-2 superinfection. Sublethal HSV-1 induced a predominantly neutralizing antibody response. Vaccination of HSV-1-seropositive mice with recombinant adjuvanted glycoprotein D (rgD-2) failed to significantly boost HSV total or neutralizing antibody responses and provided no significant increased protection against HSV-2 superinfection compared to control-vaccinated HSV-1-seropositive mice. In contrast, immunization with a single-cycle virus deleted in gD (ΔgD-2) significantly boosted total HSV-specific antibody titers and elicited new antibody-dependent cell-mediated cytotoxicity responses, providing complete protection from death following HSV-2 superinfection. This model recapitulates clinical responses to natural infection and the rgD-2 vaccine trial outcomes and suggests that ΔgD-2 may prove protective in HSV-1-seropositive hosts.

An improved animal model for herpesvirus encephalitis in humans

Herpesviral encephalitis caused by Herpes Simplex Virus 1 (HSV-1) is one of the most devastating diseases in humans. Patients present with fever, mental status changes or seizures and when untreated, sequelae can be fatal. Herpes Simplex Encephalitis (HSE) is characterized by mainly unilateral necrotizing inflammation effacing the frontal and mesiotemporal lobes with rare involvement of the brainstem. HSV-1 is hypothesized to invade the CNS via the trigeminal or olfactory nerve, but viral tropism and the exact route of infection remain unclear. Several mouse models for HSE have been developed, but they mimic natural infection only inadequately. The porcine alphaherpesvirus Pseudorabies virus (PrV) is closely related to HSV-1 and Varicella Zoster Virus (VZV). While pigs can control productive infection, it is lethal in other susceptible animals associated with severe pruritus leading to automutilation. Here, we describe the first mutant PrV establishing productive infection in mice that the animals are able to control. After intranasal inoculation with a PrV mutant lacking tegument protein pUL21 and pUS3 kinase activity (PrV-ΔUL21/US3Δkin), nearly all mice survived despite extensive infection of the central nervous system. Neuroinvasion mainly occurred along the trigeminal pathway. Whereas trigeminal first and second order neurons and autonomic ganglia were positive early after intranasal infection, PrV-specific antigen was mainly detectable in the frontal, mesiotemporal and parietal lobes at later times, accompanied by a long lasting lymphohistiocytic meningoencephalitis. Despite this extensive infection, mice showed only mild to moderate clinical signs, developed alopecic skin lesions, or remained asymptomatic. Interestingly, most mice exhibited abnormalities in behavior and activity levels including slow movements, akinesia and stargazing. In summary, clinical signs, distribution of viral antigen and inflammatory pattern show striking analogies to human encephalitis caused by HSV-1 or VZV not observed in other animal models of disease.

In developed countries, more than 50% of humans are seropositive for the neurotropic Herpes Simplex Virus 1 (HSV-1) and two to four million cases of Herpes simplex encephalitis (HSE) are reported per year worldwide. Primary infection with HSV-1 takes place via the skin or the oral mucosa followed by intraaxonal retrograde spread to sensory ganglia of the peripheral nervous system where HSV-1 usually establishes latency. Further spread to the central nervous system results in HSE, a necrotizing encephalitis effacing predominantly the temporal and frontal lobes of the brain. Mice infected with HSV-1 develop encephalitis, but do not show the typical lesions and exhibit high mortality rates. Here we demonstrate that mice infected with a mutant pseudorabies virus lacking the tegument protein pUL21 and an active viral kinase pUS3 were able to survive the productive infection but developed lymphohistiocytic encephalitis with viral antigen distribution, inflammation and associated behavioral changes comparable to HSE in humans. These striking analogies offer new perspectives to study herpesviral encephalitis in a suitable animal model.

Herpes Simplex Virus 1 Induces Brain Inflammation and Multifocal Demyelination in the Cotton Rat Sigmodon hispidus

Our work demonstrates for the first time a direct association between infection with herpes simplex virus 1, a ubiquitous human pathogen generally associated with facial cold sores, and multifocal brain demyelination in an otherwise normal host, the cotton rat Sigmodon hispidus. For a long time, demyelinating diseases were considered to be autoimmune in nature and were studied by indirect methods, such as immunizing animals with myelin components or feeding them toxic substances that induce demyelination. Treatment against demyelinating diseases has been elusive, partially because of their unknown etiology. This work provides the first experimental evidence for the role of HSV-1 as the etiologic agent of multifocal brain demyelination in a normal host and suggests that vaccination against HSV-1 can help to combat demyelinating disorders.

Demyelinating central nervous system (CNS) disorders like multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM) have been difficult to study and treat due to the lack of understanding of their etiology. Numerous cases point to the link between herpes simplex virus (HSV) infection and multifocal CNS demyelination in humans; however, convincing evidence from animal models has been missing. In this work, we found that HSV-1 infection of the cotton rat Sigmodon hispidus via a common route (lip abrasion) can cause multifocal CNS demyelination and inflammation. Remyelination occurred shortly after demyelination in HSV-1-infected cotton rats but could be incomplete, resulting in “scars,” further supporting an association between HSV-1 infection and multifocal demyelinating disorders. Virus was detected sequentially in the lip, trigeminal ganglia, and brain of infected animals. Brain pathology developed primarily on the ipsilateral side of the brain stem, in the cerebellum, and contralateral side of the forebrain/midbrain, suggesting that the changes may ascend along the trigeminal lemniscus pathway. Neurologic defects occasionally detected in infected animals (e.g., defective whisker touch and blink responses and compromised balance) could be representative of the brain stem/cerebellum dysfunction. Immunization of cotton rats with a split HSV-1 vaccine protected animals against viral replication and brain pathology, suggesting that vaccination against HSV-1 may protect against demyelinating disorders.

IMPORTANCE Our work demonstrates for the first time a direct association between infection with herpes simplex virus 1, a ubiquitous human pathogen generally associated with facial cold sores, and multifocal brain demyelination in an otherwise normal host, the cotton rat Sigmodon hispidus. For a long time, demyelinating diseases were considered to be autoimmune in nature and were studied by indirect methods, such as immunizing animals with myelin components or feeding them toxic substances that induce demyelination. Treatment against demyelinating diseases has been elusive, partially because of their unknown etiology. This work provides the first experimental evidence for the role of HSV-1 as the etiologic agent of multifocal brain demyelination in a normal host and suggests that vaccination against HSV-1 can help to combat demyelinating disorders.

Assessment of a new arbidol derivative against herpes simplex virus II in human cervical epithelial cells and in BALB/c mice

As one of the highly contagious forms, herpes simplex virus type 2 (HSV-2) commonly caused severe genital diseases and closely referred to the HIV infection. The lack of effective vaccines and drug-resistance proclaimed the preoccupation for alternative antiviral agents against HSV-2. Molecules bearing indole nucleus presented diverse biological properties involving antiviral and anti-inflammatory activities. In this study, one of the indole molecules, arbidol derivative (ARD) was designed and synthesized prior to the evaluation of its anti-HSV-2 activity. Our data showed that the ARD effectively suppressed HSV-2-induced cytopathic effects and the generation of progeny virus, with 50% effective concentrations of 3.386 and 1.717 μg/mL, respectively. The results of the time-course assay suggested that the ARD operated in a dual antiviral way by interfering virus entry and impairing the earlier period of viral cycle during viral DNA synthesis. The ARD-mediated HSV-2 inhibition was partially attained by blocking NF-κB pathways and down-regulating the expressions of several inflammatory cytokines. Furthermore, in vivo studies showed that oral administration of ARD protected BALB/c mice from intravaginal HSV-2 challenge by alleviating serious vulval lesions and histopathological changes in the target organs. Besides, the treatment with ARD also made the levels of viral protein, NF-κB protein and inflammatory cytokines lower, in consistent with the in-vitro studies. Collectively, ARD unveiled therapeutic potential for the prevention and treatment of HSV-2 infections.

Interleukin-36 in Infectious and Inflammatory Skin Diseases

Interleukin-36 (IL-36) comprises to a cytokine family consisting of four isoforms IL-36α, IL-36β, IL-36γ, and IL-36 receptor antagonist (IL-36 Ra). These IL-36 cytokines, in turn, belong to the IL-1 superfamily. The IL-36 receptor (IL-1R6) is functional as a heterodimer formed of IL-1R6 and IL-1 receptor accessory protein (IL-1RAcP). IL-36α, IL-36β, and IL-36γ are regarded as pro-inflammatory ligands and IL-36 Ra as well as IL-38 as anti-inflammatory ligands of IL-1R6. IL-36 cytokines are mainly expressed on the barrier sites of the body e.g., bronchial, intestinal, and dermal epithelium. One of their most important biological functions is the bridging of innate and adaptive immune responses. A disturbed balance between pro-inflammatory and anti-inflammatory branches easily leads to inflammation of the corresponding tissue. The most prominent example for an altered IL-36 expression is the spectrum of psoriasis. In addition to inflammatory dermatoses, IL-36 also seems to play a role in infectious dermatoses. Microbial triggers, especially Staphylococcus aureus infection, increase the production of pro-inflammatory IL-36 cytokines and initiate/promote the inflammation of skin lesions. Due to the discovery of IL-36 as an important immune mediator, it has already been possible to develop important diagnostic tools for dermatitis. Not only in the field of inflammatory skin diseases, but also in pulmonary and intestinal inflammation, there is evidence that IL-36 cytokines might have diagnostic and/or therapeutic relevance.

CCR2+ migratory macrophages with M1 status are the early-responders in the cornea of HSV-1 infected mice

Complex interactions between HSV-1 and infiltrating immune cells play important roles in establishing localized, acute virus replication as well as chronic latent infection. The extent and duration of initial virus replication are the key determinants of subsequent pathologic inflammatory responses and therefore, the accumulation of immune cell populations at this time point is a key target for prevention. Therefore, we evaluated the role of various immune cell infiltrates between 1 h and 28 days post-infection (PI) using mice infected with virulent HSV-1 strain McKrae without corneal scarification. The effect of corneal scarification on immune cell infiltrates was also determined. We first determined the activation status and origin of macrophage infiltrates as early as 1 h PI. We found a sharp increase in the total macrophage population after 12 h PI, that was primarily due to infiltration of CCR2⁺ migratory macrophages, mostly in M1 status (MHC II⁺). The number of CCR2^- resident macrophages, mostly unpolarized (M0), increased gradually over time and peaked at 48 h PI. Interestingly, some of the resident macrophages gained an M2-like phenotype (CD206^Low), which peaked at 12 h PI, concurrent with M1 macrophage infiltration. From 1–7 days PI, infiltration of various immune cells correlated strongly with HSV-1 replication, with neutrophils showing the biggest increase, and NKT cells the biggest decrease, after infection. The presence of geographical ulcer did not correlate with increased infiltration, while mice with corneal scarring had significantly more immune cell infiltration than those without corneal scarring. Overall, we showed time-dependent infiltration of various immune cells in the eye of HSV-1 infected mice. Initial infiltration of macrophages followed by infiltration of T cells at later times PI demonstrates the importance of targeting macrophages rather than other immune cells type, for therapeutic treatment of HSV-1.