Recurrent herpetic stromal keratitis in mice, a model for studying human HSK

Rift Valley Fever Virus Infects the Posterior Segment of the Eye and Induces Inflammation in a Rat Model of Ocular Disease

People infected with the mosquito-borne Rift Valley fever virus (RVFV) can suffer from eye-related problems resulting in ongoing vision issues or even permanent blindness. Despite ocular disease being the most frequently reported severe outcome, it is vastly understudied compared to other disease outcomes caused by RVFV. Ocular manifestations of RVFV include blurred vision, uveitis, and retinitis. When an infected individual develops macular or paramacular lesions, there is a 50% chance of permanent vision loss in one or both eyes. The cause of blinding ocular pathology remains unknown in part due to the lack of a tractable animal model. Using 3 relevant exposure routes, both subcutaneous (SC) and aerosol inoculation of Sprague Dawley rats led to RVFV infection of the eye. Surprisingly, direct inoculation of the conjunctiva did not result in successful ocular infection. The posterior segment of the eye, including the optic nerve, choroid, ciliary body, and retina, were all positive for RVFV antigen in SC-infected rats, and live virus was isolated from the eyes. Proinflammatory cytokines and increased leukocyte counts were also found in the eyes of infected rats. Additionally, human ocular cell lines were permissive for Lrp1-dependent RVFV infection. This study experimentally defines viral tropism of RVFV in the posterior segment of the rat eye and characterizes virally-mediated ocular inflammation, providing a foundation for evaluation of vaccines and therapeutics to protect against adverse ocular outcomes. IMPORTANCE Rift Valley fever virus (RVFV) infection leads to eye damage in humans in up to 10% of reported cases. Permanent blindness occurs in 50% of individuals with significant retinal scarring. Despite the prevalence and severity of this outcome, very little is known about the mechanisms of pathogenesis. We addressed this gap by developing a rodent model of ocular disease. Subcutaneous infection of Sprague Dawley rats resulted in infection of the uvea, retina, and optic nerve along with the induction of inflammation within the posterior eye. Infection of human ocular cells induced inflammatory responses and required host entry factors for RVFV infection similar to rodents. This work provides evidence of how RVFV infects the eye, and this information can be applied to help mitigate the devastating outcomes of RVF ocular disease through vaccines or treatments.

Inhibitory effects of baicalein against herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) is a ubiquitous and widespread human pathogen, which gives rise to a range of diseases, including cold sores, corneal blindness, and encephalitis. Currently, the use of nucleoside analogs, such as acyclovir and penciclovir, in treating HSV-1 infection often presents limitation due to their side effects and low efficacy for drug-resistance strains. Therefore, new anti-herpetic drugs and strategies should be urgently developed. Here, we reported that baicalein, a naturally derived compound widely used in Asian countries, strongly inhibited HSV-1 replication in several models. Baicalein was effective against the replication of both HSV-1/F and HSV-1/Blue (an acyclovir-resistant strain) in vitro. In the ocular inoculation mice model, baicalein markedly reduced in vivo HSV-1/F replication, receded inflammatory storm and attenuated histological changes in the cornea. Consistently, baicalein was found to reduce the mortality of mice, viral loads both in nose and trigeminal ganglia in HSV-1 intranasal infection model. Moreover, an ex vivo HSV-1-EGFP infection model established in isolated murine epidermal sheets confirmed that baicalein suppressed HSV-1 replication. Further investigations unraveled that dual mechanisms, inactivating viral particles and inhibiting IκB kinase beta (IKK-β) phosphorylation, were involved in the anti-HSV-1 effect of baicalein. Collectively, our findings identified baicalein as a promising therapy candidate against the infection of HSV-1, especially acyclovir-resistant strain.

•

Baicalein is highly effective against HSV-1infection ex vivo and in vivo.

•

Inactivation of viral particles and suppression of NF-κB activation were involved in the anti-viral effect of baicalein.

•

Hence, our work offers experimental basis for baicalein as a potential drug in treating HSV-1 associated diseases.

HSV-1 infection and pathogenesis in the tree shrew eye following corneal inoculation

Herpes simplex virus type I (HSV-1) infection causes inflammation in the cornea known as herpes simplex virus keratitis (HSK), a common but serious corneal disease. It is not entirely clear whether the virus during recurring infection comes from the trigeminal ganglia or the eye tissue, including the retina and ciliary ganglion. Because the tree shrew is closely related to primates and tree shrew eye anatomic structures are similar to humans, we studied HSV-1 corneal infection in the tree shrew. We found that HSK symptoms closely mimic those found in human HSK showing typical punctiform and dendritic viral keratitis during the acute infection period. Following the HSV-specific lesions, complications such as stromal scarring, corneal thickening (primary infection), opacity, and neovascularization were observed. In the tree shrew model, following ocular inoculation, the cornea becomes infected, and viral protein can be detected using anti-HSV-1 antibodies in the epithelial layer and retina neuronal ganglion cells. The HSV-1 transcripts, ICP0, ICP4, and LAT can be detected at 3 days post-infection (dpi), peaking at 5 dpi. After 2 weeks, ICP4 and ICP0 transcripts are reduced to a basal level, but the Latency Associated Transcripts (LATs) continue to accumulate. Interestingly, after the acute infection, we still detected abundant active HSV-1 in tree shrew eyes. Further, we found HSV-1 persistent in the ciliary ganglion and cornea. These findings are discussed in support of the tree shrew as a non-human primate HSK model, which could be useful for mechanistic studies of HSK.

CXCL10/CXCR3-Dependent Mobilization of Herpes Simplex Virus-Specific CD8+ TEM and CD8+ TRM Cells within Infected Tissues Allows Efficient Protection against Recurrent Herpesvirus Infection and Disease

Herpes simplex virus 1 (HSV-1) establishes latency within the sensory neurons of the trigeminal ganglia (TG). HSV-specific memory CD8⁺ T cells play a critical role in preventing HSV-1 reactivation from TG and subsequent virus shedding in tears that trigger recurrent corneal herpetic disease. The CXC chemokine ligand 10 (CXCL10)/CXC chemokine receptor 3 (CXCR3) chemokine pathway promotes T cell immunity to many viral pathogens, but its importance in CD8⁺ T cell immunity to recurrent herpes has been poorly elucidated. In this study, we determined how the CXCL10/CXCR3 pathway affects TG- and cornea-resident CD8⁺ T cell responses to recurrent ocular herpesvirus infection and disease using a well-established murine model in which HSV-1 reactivation was induced from latently infected TG by UV-B light. Following UV-B-induced HSV-1 reactivation, a significant increase in both the number and function of HSV-specific CXCR3⁺ CD8⁺ T cells was detected in TG and corneas of protected C57BL/6 (B6) mice, but not in TG and corneas of nonprotected CXCL10^-/- or CXCR3^-/- deficient mice. This increase was associated with a significant reduction in both virus shedding and recurrent corneal herpetic disease. Furthermore, delivery of exogenous CXCL10 chemokine in TG of CXCL10^-/- mice, using the neurotropic adeno-associated virus type 8 (AAV8) vector, boosted the number and function of effector memory CD8⁺ T cells (T_EM) and tissue-resident memory CD8⁺ T cells (T_RM), but not of central memory CD8⁺ T cells (T_CM), locally within TG, and improved protection against recurrent herpesvirus infection and disease in CXCL10^-/- deficient mice. These findings demonstrate that the CXCL10/CXCR3 chemokine pathway is critical in shaping CD8⁺ T cell immunity, locally within latently infected tissues, which protects against recurrent herpesvirus infection and disease.IMPORTANCE We determined how the CXCL10/CXCR3 pathway affects CD8⁺ T cell responses to recurrent ocular herpesvirus infection and disease. Using a well-established murine model, in which HSV-1 reactivation in latently infected trigeminal ganglia was induced by UV-B light, we demonstrated that lack of either CXCL10 chemokine or its CXCR3 receptor compromised the mobilization of functional CD8⁺ T_EM and CD8⁺ T_RM cells within latently infected trigeminal ganglia following virus reactivation. This lack of T cell mobilization was associated with an increase in recurrent ocular herpesvirus infection and disease. Inversely, augmenting the amount of CXCL10 in trigeminal ganglia of latently infected CXCL10-deficient mice significantly restored the number of local antiviral CD8⁺ T_EM and CD8⁺ T_RM cells associated with protection against recurrent ocular herpes. Based on these findings, a novel "prime/pull" therapeutic ocular herpes vaccine strategy is proposed and discussed.

Bolstering the Number and Function of HSV-1-Specific CD8+ Effector Memory T Cells and Tissue-Resident Memory T Cells in Latently Infected Trigeminal Ganglia Reduces Recurrent Ocular Herpes Infection and Disease

HSV type 1 (HSV-1) is a prevalent human pathogen that infects >3.72 billion individuals worldwide and can cause potentially blinding recurrent corneal herpetic disease. HSV-1 establishes latency within sensory neurons of trigeminal ganglia (TG), and TG-resident CD8⁺ T cells play a critical role in preventing its reactivation. The repertoire, phenotype, and function of protective CD8⁺ T cells are unknown. Bolstering the apparent feeble numbers of CD8⁺ T cells in TG remains a challenge for immunotherapeutic strategies. In this study, a comprehensive panel of 467 HLA-A*0201-restricted CD8⁺ T cell epitopes was predicted from the entire HSV-1 genome. CD8⁺ T cell responses to these genome-wide epitopes were compared in HSV-1-seropositive symptomatic individuals (with a history of numerous episodes of recurrent herpetic disease) and asymptomatic (ASYMP) individuals (who are infected but never experienced any recurrent herpetic disease). Frequent polyfunctional HSV-specific IFN-γ⁺CD107^a/b+CD44^highCD62L^lowCD8⁺ effector memory T cells were detected in ASYMP individuals and were primarily directed against three "ASYMP" epitopes. In contrast, symptomatic individuals have more monofunctional CD44^highCD62L^highCD8⁺ central memory T cells. Furthermore, therapeutic immunization with an innovative prime/pull vaccine, based on priming with multiple ASYMP epitopes (prime) and neurotropic TG delivery of the T cell-attracting chemokine CXCL10 (pull), boosted the number and function of CD44^highCD62L^lowCD8⁺ effector memory T cells and CD103^highCD8⁺ tissue-resident T cells in TG of latently infected HLA-A*0201-transgenic mice and reduced recurrent ocular herpes following UV-B-induced reactivation. These findings have profound implications in the development of T cell-based immunotherapeutic strategies to treat blinding recurrent herpes infection and disease.

The Characteristics of Herpes Simplex Virus Type 1 Infection in Rhesus Macaques and the Associated Pathological Features

As one of the major pathogens for human herpetic diseases, herpes simplex virus type 1 (HSV1) causes herpes labialis, genital herpes and herpetic encephalitis. Our aim here was to investigate the infectious process of HSV1 in rhesus macaques and the pathological features induced during this infection. Clinical symptoms that manifested in the rhesus macaque during HSV1 infection included vesicular lesions and their pathological features. Viral distribution in the nervous tissues and associated pathologic changes indicated the typical systematic pathological processes associated with viral distribution of HSV1. Interestingly, vesicular lesions recurred in oral skin or in mucosa associated with virus shedding in macaques within four to five months post-infection, and viral latency-associated transcript (LAT) mRNA was found in the trigeminal ganglia (TG) on day 365 post-infection. Neutralization testing and enzyme-linked immunospot (ELISpot) detection of specific T cell responses confirmed the specific immunity induced by HSV1 infection. Thus, rhesus macaques could serve as an infectious model for HSV1 due to their typical clinical symptoms and the pathological recurrence associated with viral latency in nervous tissues.

Real-time polymerase chain reaction for the diagnosis of necrotizing herpes stromal keratitis

AIM

To design, optimize and validate a rapid, internally controlled real-time polymerase chain reaction (RT-PCR) test for herpes simplex virus (HSV) in the diagnosis of necrotizing herpes stromal keratitis.

METHODS

Tears alone or together with corneal epithelium scrapings from 30 patients (30 eyes) suspected of necrotizing herpes stromal keratitis were tested for HSV DNA by RT-PCR. The samples were collected during the first visit and then on the subsequent 7, 14, 28, 42, and 56d. The symptoms of the patients were scored before treatment to determine the correlation between HSV concentration in the corneal epithelium scrapings and clinical scores.

RESULTS

The positive rate (46.4%) in the corneal epithelium group before the therapy was significantly higher than that (13.3%) in the tears group (P=0.006). There were 13 positive HSV patients before the therapy, the concentration of HSV DNA in corneal epithelium scrapings group was significantly higher than that in the tears group (paired t-test, P=0.0397). Multilevel mixed-effects model analysis showed that the difference between the corneal epithelium scrapings group and the tears group was statistically significant (P=0.0049). The Spearman rank correlation analysis indicated a positive correlation between the HSV concentration in the corneal epithelium scrapings and clinical scores before the treatment (r=0.844, P<0.0001).

CONCLUSION

RT-PCR appears to be a powerful molecular tool for the diagnosis of necrotizing herpes stromal keratitis.

Prior Corneal Scarification and Injection of Immune Serum are Not Required Before Ocular HSV-1 Infection for UV-B-Induced Virus Reactivation and Recurrent Herpetic Corneal Disease in Latently Infected Mice

PURPOSE

Blinding ocular herpetic disease in humans is due to spontaneous reactivation of herpes simplex virus type 1 (HSV-1) from latency, rather than to primary acute infection. Mice latently infected with HSV-1 undergo little or no in vivo spontaneous reactivation with accompanying virus shedding in tears. HSV-1 reactivation can be induced in latently infected mice by several in vivo procedures, with UV-B-induced reactivation being one commonly used method. In the UV-B model, corneas are scarified (lightly scratched) just prior to ocular infection to increase efficiency of the primary infection and immune serum containing HSV-1 neutralizing antibodies is injected intraperitoneally (i.p.) to increase survival and decrease acute corneal damage. Since scarification can significantly alter host gene transcription in the cornea and in the trigeminal ganglia (TG; the site of HSV-1 latency) and since injection of immune serum likely modulates innate and adaptive herpes immunity, we investigated eliminating both treatments.

MATERIAL AND METHODS

Mice were infected with HSV-1 with or without corneal scarification and immune serum. HSV-1 reactivation and recurrent disease were induced by UV-B irradiation.

RESULTS

When corneal scarification and immune serum were both eliminated, UV-B irradiation still induced both HSV-1 reactivation, as measured by shedding of reactivated virus in tears and herpetic eye disease, albeit at reduced levels compared to the original procedure.

CONCLUSION

Despite the reduced reactivation and disease, avoidance of both corneal scarification and immune serum should improve the clinical relevance of the UV-B mouse model.

Decreased reactivation of a herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) mutant using the in vivo mouse UV-B model of induced reactivation

Blinding ocular herpetic disease in humans is due to herpes simplex virus type 1 (HSV-1) reactivations from latency, rather than to primary acute infection. The cellular and molecular immune mechanisms that control the HSV-1 latency-reactivation cycle remain to be fully elucidated. The aim of this study was to determine if reactivation of the HSV-1 latency-associated transcript (LAT) deletion mutant (dLAT2903) was impaired in this model, as it is in the rabbit model of induced and spontaneous reactivation and in the trigeminal ganglia (TG) explant-induced reactivation model in mice. The eyes of mice latently infected with wild-type HSV-1 strain McKrae (LAT((+)) virus) or dLAT2903 (LAT((-)) virus) were irradiated with UV-B, and reactivation was determined. We found that compared to LAT((-)) virus, LAT((+)) virus reactivated at a higher rate as determined by shedding of virus in tears on days 3 to 7 after UV-B treatment. Thus, the UV-B-induced reactivation mouse model of HSV-1 appears to be a useful small animal model for studying the mechanisms involved in how LAT enhances the HSV-1 reactivation phenotype. The utility of the model for investigating the immune evasion mechanisms regulating the HSV-1 latency/reactivation cycle and for testing the protective efficacy of candidate therapeutic vaccines and drugs is discussed.