Dichotomy between survival and lytic gene expression in RNase L- and PKR-deficient mice transduced with an adenoviral vector expressing murine IFN-beta following ocular HSV-1 infection

The Transmission of SARS-CoV-2 Infection on the Ocular Surface and Prevention Strategies

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global health problem. Although the respiratory system is the main impaired organ, conjunctivitis is one of its common findings. However, it is not yet understood if SARS-CoV-2 can infect the eye and if the ocular surface can be a potential route of SARS-CoV-2 transmissions. Our review focuses on the viral entry mechanisms to give a better understanding of the interaction between SARS-CoV-2 and the eye. We highlighted findings that give evidence for multiple potential receptors of SARS-CoV-2 on the ocular surface. Additionally, we focused on data concerning the detection of viral RNA and its spike protein in the various ocular tissues from patients. However, the expression level seemed to be relatively low compared to the respiratory tissues as a result of a unique environment surrounding the ocular surface and the innate immune response of SARS-CoV-2. Nevertheless, our review suggests the ocular surface as a potential route for SARS-CoV-2 transmission, and as a result of this study we strongly recommend the protection of the eyes for ophthalmologists and patients at risk.

Study of interferon-β antiviral activity against Herpes simplex virus type 1 in neuron-enriched trigeminal ganglia cultures

Herpes simplex virus type 1 (HSV-1) causes a lytic infection in epithelial cells before being captured and moved via retrograde axonal transport to the nuclei of the sensory neurons of the trigeminal ganglion or dorsal root, where it establishes a latent infection. HSV-1 infection induces an antiviral response through the production of Beta Interferon (IFN-β) in infected trigeminal ganglia. The aim of this work was to characterize the response induced by IFN-β in neuron-enriched trigeminal ganglia primary cultures infected with HSV-1. An antiviral effect of IFN-β in these cultures was observed, including reduced viral production and increased cell survival. In contrast, viral infection significantly decreased both double stranded RNA dependent protein kinase (Pkr) transcription and Jak-1 and Stat-1 phosphorylation, suggesting a possible HSV-1 immune evasion mechanism in trigeminal cells. Additionally, HSV-1 infection upregulated Suppressor of Cytokine Signaling-3 (Socs3) mRNA; upregulation of socs3 was inhibited in IFN-β treated cultures. HSV-1 infection increased the number of Socs3 positive cells and modified the intracellular distribution of Socs3 protein, in infected cells. This neuron-enriched trigeminal ganglia culture model could be used to elucidate the HSV-1 viral cycle in sensory neurons and to study cellular antiviral responses and possible viral evasion mechanisms that underlie the choice between viral replication and latency.

Bioadhesive hyaluronan-chitosan nanoparticles can transport genes across the ocular mucosa and transfect ocular tissue

Gene transfer is considered to be a promising alternative for the treatment of several chronic diseases that affect the ocular surface. The goal of the present work was to investigate the efficacy and mechanism of action of a novel DNA nanocarrier made of hyaluronan (HA) and chitosan (CS), specifically designed for topical ophthalmic gene therapy. With this goal in mind, we first evaluated the transfection efficiency of the plasmid DNA-loaded nanoparticles in a human corneal epithelium cell model. Second, we investigated the bioadhesion and internalization of the nanoparticles in the rabbit ocular epithelia by confocal laser scanning microscopy. Third, we determined the in vivo efficacy of these nanocarriers in terms of their ability to transfect ocular tissues. The results showed that HA-CS nanoparticles and, in particular, those made of low molecular weight CS (10-12 kDa), led to high levels of expression of secreted alkaline phosphatase in the human corneal epithelium model. In addition, we observed that, following topical administration to rabbits, these nanoparticles entered the corneal and conjunctival epithelial cells and, then, become assimilated by the cells. More importantly, these nanoparticles provided an efficient delivery of the associated plasmid DNA inside the cells, reaching significant transfection levels. Therefore, we conclude that these nanoparticles may represent a new strategy toward the gene therapy of several ocular diseases.

Corneal gene therapy

Gene therapy to the cornea can potentially correct inherited and acquired diseases of the cornea. Factors that facilitate corneal gene delivery are the accessibility and transparency of the cornea, its stability ex vivo and the immune privilege of the eye. Initial corneal gene delivery studies characterized the relationship between intraocular modes of administration and location of reporter gene expression. The challenge of achieving effective topical gene transfer, presumably due to tear flow, blinking and low penetration of the vector through epithlelial tight junctions left no alternative but invasive administration to the anterior chamber and corneal stroma. DNA vaccination, RNA interference and gene transfer of cytokines, growth factors and enzymes modulated the corneal microenvironment. Positive results were obtained in preclinical studies for prevention and treatment of corneal graft rejection, neovascularization, haze and herpetic stromal keratitis. These studies, corneal gene delivery systems and modes of administration, and considerations regarding the choice of animal species used are the focus of this review. Opportunities in the field of corneal gene therapy lie in expanding the array of corneal diseases investigated and in the implementation of recent designs of safer vectors with reduced immunogenicity and longer duration of gene expression.

Oligoadenylate synthetase/protein kinase R pathways and alphabeta TCR+ T cells are required for adenovirus vector: IFN-gamma inhibition of herpes simplex virus-1 in cornea

An adenoviral (Ad) vector containing the murine IFN-gamma transgene (Ad:IFN-gamma) was evaluated for its capacity to inhibit HSV-1. To measure effectiveness, viral titers were analyzed in cornea and trigeminal ganglia (TG) during acute ocular HSV-1 infection. Ad:IFN-gamma potently suppressed HSV-1 replication in a dose-dependent fashion, requiring IFN-gamma receptor. Moreover, Ad:IFN-gamma was effective when delivered -72 and -24 h before infection as well as 24 h postinfection. Associated with antiviral opposition, TG from Ad:IFN-gamma-transduced mice harbored fewer T cells. Also related to T cell involvement, Ad:IFN-gamma was effective but attenuated in TG from alphabeta TCR-deficient mice. In corneas, alphabeta TCR(+) T cells were obligatory for protection against viral multiplication. Type I IFN involvement amid antiviral efficacy of Ad:IFN-gamma was further investigated because types I and II IFN pathways have synergistic anti-HSV-1 activity. Ad:IFN-gamma inhibited viral reproduction in corneas and TG from alphabeta IFNR-deficient (CD118(-/-)) mice, although viral titers were 2- to 3-fold higher in cornea and TG compared with wild-type mice. The absence of IFN-stimulated antiviral proteins, 2'-5' oligoadenylate synthetase/RNase L, and dsRNA-dependent protein kinase R completely eliminated the antiviral effectiveness of Ad:IFN-gamma. Collectively, the results demonstrate the following: 1) nonexistence of type I IFN receptor does not abolish defense of Ad:IFN-gamma against HSV-1; 2) antiviral pathways oligoadenylate synthetase-RNase L and protein kinase R are mandatory; and 3) alphabeta TCR(+) T cells are compulsory for Ad:IFN-gamma effectiveness against HSV-1 in cornea but not in TG.

Herpes simplex virus type 2-mediated disease is reduced in mice lacking RNase L

RNase L helps mediate the antiviral state induced by type I interferons (IFNalphabeta). Although herpes simplex virus (HSV) encodes inhibitors of the IFNalphabeta-induced antiviral response, the IFNalphabeta system serves the body as a first line of defense against HSV. We investigated whether RNase L limits HSV-2 replication and virulence. RNaseL(-/-) and wild-type C57BL/6 mice were infected intravaginally with HSV-2 strain 333. Although initial replication in the genital epithelium was similar, mice lacking RNase L developed less severe genital and neurologic disease than wild-type mice, survived longer, and contained lower viral titers in the nervous system. CD4(+) T cell infiltration into the genital tract and spinal cord of RNase L(-/-) mice was reduced, suggesting that a restricted inflammatory response may account for reduction in disease. Thus, RNase L does not play a significant role in control of HSV-2 infection in vivo; instead, RNase L may regulate aspects of the inflammatory response that contribute to disease.