Rapid NETosis Is an Effector Mechanism to Combat Ocular Herpes Infection.

Purpose: Neutrophils are known mediators of innate immunity, yet their effector function in herpesvirus infections remains poorly understood. Here, we elucidate the mechanistic action and pivotal role of neutrophil extracellular traps (NETs) during herpes simplex virus type 1 (HSV-1) ocular infection. Methods: Neutrophils were collected from mice for HSV-1 infection, fluorescence imaging, and immunoblotting assay. Tear samples from healthy subjects and patients with HSV-1 and mice were collected at L. V. Prasad Eye Institute, India, and at the University of Illinois, USA, respectively. For the in vivo study, C57BL/6 mice as well as diversity outbred mice were infected with HSV-1 (McKrae strain) followed by tear fluid collection at various time points (0-10 days). Samples were used for Flow cytometry, ELISA, and immunofluorescence assay. Human transcriptomic profile of keratitis dataset was used evaluate NETosis signaling pathways. We also performed neutrophil depletion studies. Results: Our data revealed a discernible temporal NET formation (NETosis) predominantly in the infected eye, across normal and diversity outbred murine models and human cases of HSV-1 infection. HSV-1 instigates swift NETosis governed by caspase-1 activation and myeloperoxidase secretion. Distinct accumulations of neutrophils, remaining unengaged in NET release in the contralateral eye post-infection, hinting at a proactive defensive posture in the uninfected eye. Moreover, neutrophil depletion accentuated ocular pathology, augmented viral load, and escalated disease scores, substantiating the protective effects of NETs in curtailing viral replication. Conclusions: Our report uncovers a previously unexplored mechanism of NETosis through pro-inflammatory cell death in response to ocular HSV-1 infection, and HPSE up-regulation, identifying new avenues for future studies.

The Topical Novel Formulations of Interferon α-2в Effectively Inhibit HSV-1 Keratitis in the Rabbit Eye Model and HSV-2 Genital Herpes in Mice.

Herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2) are widespread human pathogens that establish chronic latent infections leading to recurrent episodes. Current treatments are limited, necessitating the development of novel antiviral strategies. This study aimed to assess the antiviral efficacy of novel topical formulations containing interferon alpha-2b (IFN α-2b) against HSV-1 and HSV-2. The formulations, Oftalmoferon® forte (eye drops) and Interferon Vaginal Tablets, demonstrated potent antiviral effects against HSV-1 and HSV-2 in Vero cells, respectively, with concentration-dependent inhibition of viral replication. Subsequently, their efficacy was tested in animal models: HSV-1 keratitis in the rabbit eye model and HSV-2 genital herpes in mice. Oftalmoferon® forte effectively treated HSV-1 keratitis, reducing clinical symptoms and ulcerations compared to virus control. Interferon Vaginal Tablets showed promising results in controlling HSV-2 genital herpes in mice, improving survival rates, reducing clinical signs, weight loss and viral replication. The novel IFN α-2b formulations exhibited significant antiviral activity against HSV infections in cell culture and animal models. These findings suggest the potential of these formulations as alternative treatments for HSV infections, particularly in cases resistant to current therapies. Further studies are warranted to optimize treatment regimens and assess clinical efficacy in humans.

Overexpression of NLRP12 enhances antiviral immunity and alleviates herpes simplex keratitis via pyroptosis/IL-18/IFN-γ signaling.

Herpes simplex keratitis (HSK) is a blinding disease caused by herpes simplex virus type 1 (HSV-1) infection, and rapid eradication of the virus from the affected cornea is imperative. Nod-like receptors (NLRs) are intracellular innate immune sensors closely associated with cell death, inflammation and immune responses. In this study, we investigated the role of NLRP12 in the antiviral immunology in HSK and the underlying mechanisms. We found that NLRP12 expression was significantly decreased in HSV-1-infected human corneal epithelial cells (HCE-Ts) and HSK mouse corneas. Overexpression of NLRP12 significantly reduced viral replication in infected HCE-Ts and functioned through inflammasome-mediated pyroptosis and downstream IL-18-IFN-γ axis. In HSK mouse models, overexpression of NLRP12 reduced viral replication in the cornea and alleviated HSK symptoms. This resulted from enhanced antiviral immune responses including the activation of specific immune cells in both the cornea and the draining lymph nodes. Specifically, the NLRP12-IL-18-IFN-γ axis regulated the interaction between infected corneal epithelial cells and macrophages. In conclusion, our study identified a role of NLRP12 in mediating pyroptosis and regulating antiviral immune responses. This novel finding opens the possibilities of NLRP12 as a viable target in the therapeutic strategies for HSV-1 infection.

Harmol used for the treatment of herpes simplex virus induced keratitis.

Herpes simplex virus type 1 (HSV-1) infection of the eyes results in herpes simplex keratitis (HSK), which has led to vision loss and even blindness in patients. However, the rate of drug resistance in HSV is on the rise; therefore, new antiviral agents with sufficient safety profiles must be developed. At present, we assessed the anti-HSV-1 activity of 502 natural compounds and their ability to reduce the HSV-1-induced cytopathic effect. We chose harmol for further studies because it exhibited the highest antiviral activity. We found that harmol inhibited both HSV-1 F and HSV-1/153 (a clinical drug-resistant strain) replication, with an EC50 of 9.34 µM and 5.84 µM, respectively. Moreover, harmol reduced HSV-1 replication in corneal tissues and viral progeny production in tears, and also alleviated early corneal surface lesions related to HSK. For example, harmol treatment preserved corneal thickness and nerve density in HSK mice. Interestingly, harmol also showed a promising antiviral effect on HSV-1/153 induced HSK in mouse model. Furthermore, harmol combined with acyclovir (ACV) treatment showed a greater antiviral effect than either one alone in vitro. Therefore, harmol may be a promising therapeutic agent for managing HSK.

Commercial human 3D corneal epithelial equivalents for modeling epithelial infection in herpes keratitis.

Herpes stromal keratitis is the leading cause of infectious blindness in the western world. Infection by HSV1 is most common, but VZV and hCMV also infect the cornea. Multiple models of HSV1 corneal infection exist, but none for VZV and hCMV because of their host specificity. Here, we used commercially available 3D human corneal epithelial equivalents (HCEE) to study infection by these herpesviruses. HCEE was infected by HSV-1 and hCMV without requiring scarification and resulted in spreading infections. Spread of HSV-1 infection was rapid, while that of hCMV was slow. In contrast, infections with VZV required damage to the HCEE and did not spread. Acyclovir dramatically reduced replication of HSV-1 in this model. We conclude that highly quality-controlled, readily available HCEE is a useful model to study human-restricted herpesvirus infection of the human corneal epithelium and for screening of antiviral drugs for treating HSK in an 3D model system.

Emerging drugs for the treatment of herpetic keratitis.

INTRODUCTION: Herpes simplex keratitis stands as a prominent factor contributing to infectious blindness among developed nations. On a global scale, over 60% of the population tests positive for herpes simplex virus type-1 (HSV-1). Despite these statistics, there is currently no vaccine available for the virus. Moreover, the conventional nucleoside drugs prescribed to patients are proving ineffective in addressing issues related to drug resistance, recurrence, latency, and the escalating risk of vision loss. Hence, it is imperative to continually explore all potential avenues to restrict the virus. This review article centers on the present treatment methods for HSV-1 keratitis (HSK), highlighting the ongoing clinical trials. It delves into the emerging drugs, their mode-of-action and future therapeutics. AREAS COVERED: The review focuses on the significance of a variety of small molecules targeting HSV-1 lifecycle at multiple steps. Peer-reviewed articles and abstracts were searched in MEDLINE, PubMed, Embase, and clinical trial websites. EXPERT OPINION: The exploration of small molecules that target specific pathways within the herpes lifecycle holds the potential for substantial impact on the antiviral pharmaceutical market. Simultaneously, the pursuit of disease-specific biomarkers has the capacity to usher in a transformative era in diagnostics within the field.

Viral Keratitis, Surgical Intervention in Viral Keratitis, Challenges in Diagnosis and Treatment of Viral Keratitis, HSV, HZV.

Viral keratitis is a significant cause of ocular morbidity and visual impairment worldwide. In recent years, there has been a growing understanding of the pathogenesis, clinical manifestations, and diagnostic modalities for viral keratitis. The most common viral pathogens associated with this condition are adenovirus, herpes simplex (HSV), and varicella-zoster virus (VZV). However, emerging viruses such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), and Vaccinia virus can also cause keratitis. Non-surgical interventions are the mainstay of treatment for viral keratitis. Antiviral agents such as Acyclovir, Ganciclovir, and trifluridine have effectively reduced viral replication and improved clinical outcomes. Additionally, adjunctive measures such as lubrication, corticosteroids, and immunomodulatory agents have alleviated symptoms by reducing inflammation and facilitating tissue repair. Despite these conservative approaches, some cases of viral keratitis may progress to severe forms, leading to corneal scarring, thinning, or perforation. In such instances, surgical intervention becomes necessary to restore corneal integrity and visual function. This review article aims to provide an overview of the current perspectives and surgical interventions in managing viral keratitis. The choice of surgical technique depends on the extent and severity of corneal involvement. As highlighted in this article, on-going research and advancements in surgical interventions hold promise for further improving outcomes in patients with viral keratitis.

Sensory Nerve Retraction and Sympathetic Nerve Innervation Contribute to Immunopathology of Murine Recurrent Herpes Stromal Keratitis.

Purpose: Herpes stromal keratitis (HSK) represents a spectrum of pathologies which is caused by herpes simplex virus type 1 (HSV-1) infection and is considered a leading cause of infectious blindness. HSV-1 infects corneal sensory nerves and establishes latency in the trigeminal ganglion (TG). Recently, retraction of sensory nerves and replacement with "unsensing" sympathetic nerves was identified as a critical contributor of HSK in a mouse model where corneal pathology is caused by primary infection. This resulted in the loss of blink reflex, corneal desiccation, and exacerbation of inflammation leading to corneal opacity. Despite this, it was unclear whether inflammation associated with viral reactivation was sufficient to initiate this cascade of events. Methods: We examined viral reactivation and corneal pathology in a mouse model with recurrent HSK by infecting the cornea with HSV-1 (McKrae) and transferring (intravenous [IV]) human sera to establish primary infection without discernible disease and then exposed the cornea to UV-B light to induce viral reactivation. Results: UV-B light induced viral reactivation from latency in 100% of mice as measured by HSV-1 antigen deposition in the cornea. Further, unlike conventional HSK models, viral reactivation resulted in focal retraction of sensory nerves and corneal opacity. Dependent on CD4+ T cells, inflammation foci were innervated by sympathetic nerves. Conclusions: Collectively, our data reveal that sectoral corneal sensory nerve retraction and replacement of sympathetic nerves were involved in the progressive pathology that is dependent on CD4+ T cells after viral reactivation from HSV-1 latency in the UV-B induced recurrent HSK mouse model.

Absence of signal peptide peptidase in peripheral sensory neurons affects latency-reactivation in HSV-1 ocularly infected mice.

We previously reported that HSV-1 infectivity in vitro and in vivo requires HSV glycoprotein K (gK) binding to the ER signal peptide peptidase (SPP). Anterograde-retrograde transport via peripheral nerves between the site of infection (i.e., eye) and the site of latency (neurons) is a critical process to establish latency and subsequent viral reactivation. Given the essential role of neurons in HSV-1 latency-reactivation, we generated mice lacking SPP specifically in peripheral sensory neurons by crossing Advillin-Cre mice with SPPfl/fl mice. Expression of SPP mRNA and protein were significantly lower in neurons of Avil-SPP-/- mice than in control mice despite similar levels of HSV-1 replication in the eyes of Avil-SPP-/- mice and control mice. Viral transcript levels in isolated neurons of infected mice on days 2 and 5 post infection were lower than in control mice. Significantly less LAT, gB, and PD-1 expression was seen during latency in isolated neurons and total trigeminal ganglia (TG) of Avil-SPP-/- mice than in control mice. Finally, reduced latency and reduced T cell exhaustion in infected Avil-SPP-/- mice correlated with slower and no reactivation. Overall, our results suggest that blocking SPP expression in peripheral sensory neurons does not affect primary virus replication or eye disease but does reduce latency-reactivation. Thus, blocking of gK binding to SPP may be a useful tool to reduce latency-reactivation.

Herpes simplex virus PCR in 2230 explanted corneal buttons.

PURPOSE: To determine herpes simplex virus (HSV) DNA prevalence and mean cycle threshold of polymerase chain reaction (PCR) in corneal tissue of patients with penetrating keratoplasty (PKP), with (HSK+) and without (HSK-) previous clinical herpetic keratitis history. METHODS: Retrospective review of recipient corneal buttons which were explanted through PKP between March 2010 and September 2018 at the Department of Ophthalmology, Saarland University Medical Center in Homburg/Saar, Germany. Corneal tissue samples were analysed by real-time PCR for the presence of HSV DNA. For each subject, clinical data, including patients' demographics and clinical diagnoses, were collected. RESULTS: In total, 2230 corneal samples (age at the time of the surgery 57.3 ± 19.2 years) of 1860 patients were analysed. HSV PCR was positive in 137 (6.1%) corneal samples, with a 30.57 ± 6.01 (range 14-39) mean cycle threshold (Ct) value. Two hundred ninety-eight (13.4%) corneas of 266 patients were clinically HSK+, and 1932 (86.6%) corneas of 1600 patients were clinically HSK-. HSV DNA was detected significantly more frequently (p < 0.0001) in HSK+ corneal samples (108 corneal samples; 36.2%), than in HSK- corneal samples (29 corneal samples; 1.5%). Ct value was significantly lower in HSK+ than in HSK- corneal samples (29.8 ± 5.8 versus 32.6 ± 5.9; p = 0.008). CONCLUSION: Our data demonstrate that a positive clinical history of HSK is related to HSV PCR positivity in about every 2.8th patient. In addition, about every 66th explanted corneal tissue is HSV PCR-positive despite the lack of clinical suspicion. These patients may need additional local/systemic antiviral treatment to avoid newly acquired HSK following penetrating keratoplasty.

Intramuscular Vaccination With the HSV-1(VC2) Live-Attenuated Vaccine Strain Confers Protection Against Viral Ocular Immunopathogenesis Associated With γδT Cell Intracorneal Infiltration.

Herpes simplex virus type-1 (HSV-1) ocular infection is one of the leading causes of infectious blindness in developed countries. The resultant herpetic keratitis (HK) is caused by an exacerbated reaction of the adaptive immune response that persists beyond virus clearance causing substantial damage to the cornea. Intramuscular immunization of mice with the HSV-1(VC2) live-attenuated vaccine strain has been shown to protect mice against lethal ocular challenge. Herein, we show that following ocular challenge, VC2 vaccinated animals control ocular immunopathogenesis in the absence of neutralizing antibodies on ocular surfaces. Ocular protection is associated with enhanced intracorneal infiltration of γδ T cells compared to mock-vaccinated animals. The observed γδ T cellular infiltration was inversely proportional to the infiltration of neutrophils, the latter associated with exacerbated tissue damage. Inhibition of T cell migration into ocular tissues by the S1P receptors agonist FTY720 produced significant ocular disease in vaccinated mice and marked increase in neutrophil infiltration. These results indicate that ocular challenge of mice immunized with the VC2 vaccine induce a unique ocular mucosal response that leads into the infiltration of γδ T cells resulting in the amelioration of infection-associated immunopathogenesis.

6-Thioguanine Inhibits Herpes Simplex Virus 1 Infection of Eyes.

Herpes simplex virus 1 (HSV-1) infects eye corneal tissues leading to herpetic stromal keratitis (HSK), which is one of the leading causes of blindness. Here in our study, we found that 6-thioguanine (6-TG), a once clinically approved medication for child acute myelogenous leukemia, inhibited multiple strains of HSV-1 infection in vitro and in vivo. 6-TG is more potent than acyclovir (ACV) and ganciclovir (GCV), with the 50% inhibitory concentration (IC50) of 6-TG at 0.104 µM with high stimulation index (SI) (SI = 6,475.48) compared to the IC50 of ACV at 1.253 µM and the IC50 of GCV at 1.257 µM. In addition, 6-TG at 500 µM topically applied to the eyes with HSV-1 infection significantly inhibits HSV-1 replication, alleviates virus-induced HSK pathogenesis, and improves eye conditions. More importantly, 6-TG is effective against ACV-resistant HSV-1 strains, including HSV-1/153 and HSV-1/blue. Knockdown of Rac1 with small interfering RNA (siRNA) negatively affected HSV-1 replication, suggesting that Rac1 facilitated HSV-1 replication. Following HSV-1 infection of human corneal epithelial cells (HCECs), endogenous Rac1 activity was upregulated by glutathione S-transferase (GST) pulldown assay. We further found that Rac1 was highly expressed in the corneal tissue of HSK patients compared to normal individuals. Mechanistic study showed that 6-TG inhibited HSV-1 replication by targeting Rac1 activity in HSV-1 infected cells, and the Rac1 is critical in the pathogenesis of HSK. Our results indicated that 6-TG is a promising therapeutic molecule for the treatment of HSK. IMPORTANCE We reported the discovery of 6-TG inhibition of HSV-1 infection and its inhibitory roles in HSK both in vitro and in vivo. 6-TG was shown to possess at least 10× more potent inhibitory activity against HSV-1 than ACV and GCV and, more importantly, inhibit ACV/GCV-resistant mutant viruses. Animal model studies showed that gel-formulated 6-TG topically applied to eyes locally infected with HSV-1 could significantly inhibit HSV-1 replication, alleviate virus-induced HSK pathogenesis, and improve eye conditions. Further study showed that HSV-1 infection upregulated Rac1 expression, and knockdown of Rac1 using siRNA markedly restricted HSV-1 replication, suggesting that Rac1 is required for HSV-1 replication. In addition, we also documented that Rac1 is highly expressed in corneal tissues from HSK patients, indicating that Rac1 is associated with HSK pathogenesis. In view of the high potency of 6-TG, low cytotoxicity, targeting a distinct therapeutic target, we suggest that 6-TG is a potential candidate for development as a therapeutic agent for HSK therapy.

Advancing Our Understanding of Corneal Herpes Simplex Virus-1 Immune Evasion Mechanisms and Future Therapeutics.

Herpes stromal keratitis (HSK) is a disease that commonly affects the cornea and external eye and is caused by Herpes Simplex Virus type 1 (HSV-1). This virus infects approximately 66% of people worldwide; however, only a small portion of these people will develop symptoms in their lifetime. There is no cure or vaccine available for HSV-1; however, there are treatments available that aim to control the inflammation caused by the virus and prevent its recurrence. While these treatments are beneficial to those suffering with HSK, there is a need for more effective treatments to minimise the need for topical steroids, which can have harmful effects, and to prevent bouts of disease reactivation, which can lead to progressive corneal scarring and visual impairment. This review details the current understanding of HSV-1 infection and discusses potential novel treatment options including microRNAs, TLRs, mAbs, and aptamers.

Suppression of CD80 Expression by ICP22 Affects Herpes Simplex Virus Type 1 Replication and CD8+IFN-γ+ Infiltrates in the Eyes of Infected Mice but Not Latency Reactivation.

Previously, we reported that herpes simplex virus type 1 (HSV-1) ICP22 binds to the CD80 promoter and suppresses its expression in vitro and in vivo. To better understand the impact of ICP22 binding to CD80 on HSV-1 infectivity and pathogenicity, we mapped the region of ICP22 required to bind the CD80 promoter to a 40-amino-acid (aa) region of ICP22. We constructed a recombinant HSV-1 expressing a truncated form of ICP22 that lacks these 40 aa, which does not bind to the CD80 promoter (KOS-ICP22Δ40) and retains the ability to replicate efficiently in rabbit skin cells, in contrast to ICP22-null virus. The replication of this recombinant virus in vitro and in vivo was higher than that of the ICP22-null virus, but virus replication kinetics were lower than those of the wild-type (WT) control virus. Similar to ICP22-null virus, the KOS-ICP22Δ40 mutant virus increased CD80 expression in dendritic cells (DCs) and interferon gamma (IFN-γ) expression in CD8+ T cells but not CD4+ T cells in infected mouse corneas. In contrast to the significantly reduced virus replication in the eyes of ocularly infected mice, the levels of latency reactivation were similar between KOS-ICP22Δ40 virus and WT virus. Thus, blocking ICP22 binding to the CD80 promoter using a recombinant virus expressing a truncated ICP22 that lacks CD80 promoter binding appears to reduce virus replication and enhance CD8+IFN-γ+ infiltrates in corneas of infected mice, with no effect on latency reactivation. IMPORTANCE Direct binding of HSV-1 ICP22 to the CD80 promoter downregulates the expression of the costimulatory molecule CD80 but not CD86. In this study, we fine mapped the region of ICP22 required for binding to the CD80 promoter and constructed a recombinant virus containing a deletion in ICP22 that failed to bind to the CD80 promoter. This recombinant virus replicated less efficiently in vitro and in vivo than did the WT control virus, although CD80-expressing CD11c+ cells and IFN-γ-expressing CD8+ T cells were increased. Interestingly, the levels of latency and reactivation in the two viruses were similar despite lower virus replication in the eyes of infected mice. Therefore, blocking the interaction of ICP22 with the CD80 promoter could be used to temper the immune response.

Role Played by Receptors for Advanced Glycosylation End Products in Corneal Endothelial Cells after HSV-1 Infection.

Senescence, sterile inflammation, and infection cause dysfunction of corneal endothelial cells, leading to visual morbidity that may require corneal transplantation. With increasing age, the extracellular matrix is modified by non-enzymatic glycation forming advanced glycation end products (AGEs). The modifications are primarily sensed by the receptors for the AGEs (RAGE) and are manifested as a type I interferon response. Interestingly, in our study, human corneal endothelial cells (HCEn) cells did not respond to the typical RAGE ligands, including the AGEs, high mobility group box 1 (HMGB1), and serum amyloid-A (SAA). Instead, HCEn cells responded exclusively to the CpG DNA, which is possessed by typical corneal pathogen, herpes simplex virus-1 (HSV-1). Upon HSV-1 infection, the surface expression of RAGE was increased, and endocytosed HSV-1 was associated with RAGE and CpG DNA receptor, TLR9. RAGE DNA transfection markedly increased interferon-ß secretion by CpG DNA or HSV-1 infection. HSV-1 infection-induced interferon-ß secretion was abolished by TLR9 inhibition and partially by RAGE inhibition. Global transcriptional response analysis confirmed that RAGE and TLR9 were both significantly involved in type I interferon responses. We conclude that RAGE is a sensor of HSV-1 infection and provokes a type I interferon response.

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.

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.

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

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

Targeting herpes simplex virus with CRISPR-Cas9 cures herpetic stromal keratitis in mice.

Herpes simplex virus type 1 (HSV-1) is a leading cause of infectious blindness. Current treatments for HSV-1 do not eliminate the virus from the site of infection or latent reservoirs in the trigeminal ganglia. Here, we target HSV-1 genomes directly using mRNA-carrying lentiviral particles that simultaneously deliver SpCas9 mRNA and viral-gene-targeting guide RNAs (designated HSV-1-erasing lentiviral particles, termed HELP). We show that HELP efficiently blocks HSV-1 replication and the occurrence of herpetic stromal keratitis (HSK) in three different infection models. HELP was capable of eliminating the viral reservoir via retrograde transport from corneas to trigeminal ganglia. Additionally, HELP inhibited viral replication in human-derived corneas without causing off-target effects, as determined by whole-genome sequencing. These results support the potential clinical utility of HELP for treating refractory HSK.