Screening Method for CRISPR/Cas9 Inhibition of a Human DNA Virus: Herpes Simplex Virus

Herpes simplex keratitis: A brief clinical overview

The aim of our minireview is to provide a brief overview of the diagnosis, clinical aspects, treatment options, management, and current literature available regarding herpes simplex keratitis (HSK). This type of corneal viral infection is caused by the herpes simplex virus (HSV), which can affect several tissues, including the cornea. One significant aspect of HSK is its potential to cause recurrent episodes of inflammation and damage to the cornea. After the initial infection, the HSV can establish a latent infection in the trigeminal ganglion, a nerve cluster near the eye. The virus may remain dormant for extended periods. Periodic reactivation of the virus can occur, leading to recurrent episodes of HSK. Factors triggering reactivation include stress, illness, immunosuppression, or trauma. Recurrent episodes can manifest in different clinical patterns, ranging from mild epithelial involvement to more severe stromal or endothelial disease. The severity and frequency of recurrences vary among individuals. Severe cases of HSK, especially those involving the stroma and leading to scarring, can result in vision impairment or even blindness in extreme cases. The cornea's clarity is crucial for good vision, and scarring can compromise this, potentially leading to visual impairment. The management of HSK involves not only treating acute episodes but also implementing long-term strategies to prevent recurrences and attempt repairs of corneal nerve endings via neurotization. Antiviral medications, such as oral Acyclovir or topical Ganciclovir, may be prescribed for prophylaxis. The immune response to the virus can contribute to corneal damage. Inflammation, caused by the body's attempt to control the infection, may inadvertently harm the corneal tissues. Clinicians should be informed about triggers and advised on measures to minimize the risk of reactivation. In summary, the recurrent nature of HSK underscores the importance of both acute and long-term management strategies to preserve corneal health and maintain optimal visual function.

Construction of BHV-1 UL41 Defective Virus Using the CRISPR/Cas9 System and Analysis of Viral Replication Properties

Bovine herpesvirus type 1 (BHV-1) is a neurotropic herpesvirus that causes infectious rhinotracheitis and vulvovaginitis in cattle. The virion host shutoff protein encoded by the BHV-1 UL41 gene is highly conserved in the Alphaherpesvirinae subfamily. This protein can degrade viral and host messenger RNA (mRNA) to interrupt host defense and facilitate the rapid proliferation of BHV-1. However, studies on the BHV-1 UL41 gene are limited, and BHV-1 defective virus construction using the CRISPR/Cas9 system is somewhat challenging. In this study, we rapidly constructed a BHV-1 UL41-deficient strain using the CRISPR/Cas9 system in BL primary bovine-derived cells. BHV-1 UL41-defective mutants were screened by Western blot analysis using specific polyclonal antibodies as the primary antibodies. During the isolation and purification of the defective strain, a mixed virus pool edited by an efficient single-guide RNA (sgRNA) showed a plaque number reduction. Viral growth property assessment showed that BHV-1 UL41 was dispensable for replication, but the UL41-defective strain exhibited early and slowed viral replication. Furthermore, the BHV-1 UL41-deficient strain exhibited enhanced sensitivity to temperature and acidic environments. The BHV-1 UL41-deficient strain regulated viral and host mRNA levels to affect viral replication.

Antiviral Targeting of Varicella Zoster Virus Replication and Neuronal Reactivation Using CRISPR/Cas9 Cleavage of the Duplicated Open Reading Frames 62/71

Varicella Zoster Virus (VZV) causes Herpes Zoster (HZ), a common debilitating and complicated disease affecting up to a third of unvaccinated populations. Novel antiviral treatments for VZV reactivation and HZ are still in need. Here, we evaluated the potential of targeting the replicating and reactivating VZV genome using Clustered Regularly Interspaced Short Palindromic Repeat-Cas9 nucleases (CRISPR/Cas9) delivered by adeno-associated virus (AAV) vectors. After AAV serotype and guide RNA (gRNA) optimization, we report that a single treatment with AAV2-expressing Staphylococcus aureus CRISPR/Cas9 (saCas9) with gRNA to the duplicated and essential VZV genes ORF62/71 (AAV2-62gRsaCas9) greatly reduced VZV progeny yield and cell-to-cell spread in representative epithelial cells and in lytically infected human embryonic stem cell (hESC)-derived neurons. In contrast, AAV2-62gRsaCas9 did not reduce the replication of a recombinant virus mutated in the ORF62 targeted sequence, establishing that antiviral effects were a consequence of VZV-genome targeting. Delivery to latently infected and reactivation-induced neuron cultures also greatly reduced infectious-virus production. These results demonstrate the potential of AAV-delivered genome editors to limit VZV productive replication in epithelial cells, infected human neurons, and upon reactivation. The approach could be developed into a strategy for the treatment of VZV disease and virus spread in HZ.