Role of IFN-λ in Herpes Simplex Virus-1-induced corneal Immunopathology

Abstract

The Herpes simplex virus (HSV) is a highly successful pathogen in the Herpesviridae family, consisting of eight enveloped human herpesviruses. These double-stranded DNA viruses with similar morphology can reactivate latent infection and develop productive lytic infections. HSV-1, a highly prevalent pathogen, spreads through close contact and causes lifelong infections. It can cause asymptomatic, mild, or fatal illnesses. The annual medical, social, and financial costs of HSV infection exceed $400 million in the USA. Anti-HSV medications like acyclovir, valacyclovir, penciclovir, and famciclovir effectively treat herpes virus infections. Still, they have hazardous side effects and are not effective in treating drug-resistant variants. Despite years of research, no approved vaccinations are available for prevention or therapy. HSV-1 infection of the cornea causes a severe immunoinflammatory and vision-impairing condition called herpetic stromal keratitis (SK). The virus replication in corneal epithelium, followed by neutrophil- and CD4+ T cell-mediated inflammation, plays a dominant role in SK. Although previous studies demonstrate critical functions of type I IFNs (IFN-α/β) in HSV-1 infection, the role of recently discovered IFN-λ (type III IFN), specifically at the corneal mucosa, is poorly defined. Our study using a mouse model of SK pathogenesis shows that HSV-1 infection induces a robust IFN-λ response compared with type I IFN production at the corneal mucosal surface. However, the normal progression of SK indicates that the endogenous IFN responses are insufficient to suppress HSV–1-induced corneal pathology. Therefore, we examined the therapeutic efficacy of exogenous rIFN-λ during SK progression. Our results show that rIFN-λ therapy suppressed inflammatory cell infiltration in the cornea and significantly reduced the SK pathologic condition. Early rIFN-λ treatment significantly reduced neutrophil and macrophage 3 infiltration and IL-6, IL-1 β, and CXCL-1 production in the cornea. Notably, the viricidal capacity of neutrophils and macrophages measured by reactive oxygen species generation was not affected. Similarly, ex vivo rIFN-λ treatment of HSV-1-stimulated bone marrow-derived neutrophils significantly promoted IFN-stimulated genes without affecting reactive oxygen species production. Collectively, our data demonstrate that exogenous topical rIFN-λ treatment during the development and progression of SK could represent a novel therapeutic approach to control HSV–1–induced inflammation and associated vision impairment. RNA-seq analysis has transformed gene expression research by enabling extensive and precise quantitative measurements. This study showcased the potential of RNA-seq in comprehending gene regulation during corneal HSV-1 infection following exogenous rIFN-λ therapy. We employed DESeq2 analysis to compare gene expression levels between corneas infected with HSV-1 and corneas treated with rIFN-λ. We elucidated the antiviral and anti-inflammatory mechanism of rIFN-λ in the context of corneal HSV-1 infection in mice, confirming previous studies on the therapeutic effects of IFN-λ against HSV-1. Prolonged treatment with acyclovir (ACV), a preferred systemic therapy against HSV-1 infection, often leads to the development of HSV-1 strains resistant to ACV. In this study, we generated and characterized ACV-resistant (ACVR) HSV-1 (McKrae), a neurotropic strain that mimics the clinical HSV-1 infection caused by an ACV-resistant strain. This virus was utilized to check the effectiveness of IFN-λ in inhibiting ACVR HSV-1. We found that IFN-λ effectively inhibits the formation of matured virus particles.