Atypical cytomegalovirus retinal disease in pyroptosis-deficient mice with murine acquired immunodeficiency syndrome

The Host-Pathogen Interplay: A Tale of Two Stories within the Cornea and Posterior Segment

Ocular infectious diseases are an important cause of potentially preventable vision loss and blindness. In the following manuscript, we will review ocular immunology and the pathogenesis of herpesviruses and Pseudomonas aeruginosa infections of the cornea and posterior segment. We will highlight areas of future research and what is currently known to promote bench-to-bedside discoveries to improve clinical outcomes of these debilitating ocular diseases.

Spotlight on pyroptosis: role in pathogenesis and therapeutic potential of ocular diseases

Pyroptosis is a programmed cell death characterized by swift plasma membrane disruption and subsequent release of cellular contents and pro-inflammatory mediators (cytokines), including IL‐1β and IL‐18. It differs from other types of programmed cell death such as apoptosis, autophagy, necroptosis, ferroptosis, and NETosis in terms of its morphology and mechanism. As a recently discovered form of cell death, pyroptosis has been demonstrated to be involved in the progression of multiple diseases. Recent studies have also suggested that pyroptosis is linked to various ocular diseases. In this review, we systematically summarized and discussed recent scientific discoveries of the involvement of pyroptosis in common ocular diseases, including diabetic retinopathy, age-related macular degeneration, AIDS-related human cytomegalovirus retinitis, glaucoma, dry eye disease, keratitis, uveitis, and cataract. We also organized new and emerging evidence suggesting that pyroptosis signaling pathways may be potential therapeutic targets in ocular diseases, hoping to provide a summary of overall intervention strategies and relevant multi-dimensional evaluations for various ocular diseases, as well as offer valuable ideas for further research and development from the perspective of pyroptosis.

Essential Role of NLRP3 Inflammasome in Mediating IL-1β Production and the Pathobiology of Staphylococcus aureus Endophthalmitis

Staphylococcal endophthalmitis is one of the leading causes of blindness following ocular surgery and trauma. Dysregulated inflammation during bacterial endophthalmitis causes host-induced inflammatory damage and vision loss if it remains unchecked. Emerging evidence indicates that inflammasome plays a critical role in regulating innate immunity in various infectious and inflammatory diseases. However, the role of the inflammasome in endophthalmitis remains elusive. Here, using a mouse model of Staphylococcus (S) aureus endophthalmitis, we show that NLRP3/ASC/Caspase-1 signaling regulates IL-1β production in endophthalmitis. We also show that S. aureus and its cell wall components and toxins induce the activation of the NLRP3 inflammasome complex in mouse eyes. Moreover, we found that both infiltrating neutrophils and retinal microglia contribute toward NLRP3 activation and IL-1β production in S. aureus-infected eyes. Furthermore, our data using NLRP3^-/- and IL-1β^-/- mice revealed that NLRP3 and IL-1β deficiency leads to increased intraocular bacterial burden and retinal tissue damage. Altogether, our study demonstrated an essential role of NLRP3 inflammasome activation in regulating innate immune responses in bacterial endophthalmitis.

PANoptosis in Viral Infection: The Missing Puzzle Piece in the Cell Death Field

In the past decade, emerging viral outbreaks like SARS-CoV-2, Zika and Ebola have presented major challenges to the global health system. Viruses are unique pathogens in that they fully rely on the host cell to complete their lifecycle and potentiate disease. Therefore, programmed cell death (PCD), a key component of the host innate immune response, is an effective strategy for the host cell to curb viral spread. The most well-established PCD pathways, pyroptosis, apoptosis and necroptosis, can be activated in response to viruses. Recently, extensive crosstalk between PCD pathways has been identified, and there is evidence that molecules from all three PCD pathways can be activated during virus infection. These findings have led to the emergence of the concept of PANoptosis, defined as an inflammatory PCD pathway regulated by the PANoptosome complex with key features of pyroptosis, apoptosis, and/or necroptosis that cannot be accounted for by any of these three PCD pathways alone. While PCD is important to eliminate infected cells, many viruses are equipped to hijack host PCD pathways to benefit their own propagation and subvert host defense, and PCD can also lead to the production of inflammatory cytokines and inflammation. Therefore, PANoptosis induced by viral infection contributes to either host defense or viral pathogenesis in context-specific ways. In this review, we will discuss the multi-faceted roles of PCD pathways in controlling viral infections.

A Mouse Model That Mimics AIDS-Related Cytomegalovirus Retinitis: Insights into Pathogenesis

With the appearance of the worldwide AIDS pandemic four decades ago came a number of debilitating opportunistic infections in patients immunosuppressed by the pathogenic human retrovirus HIV. Among these was a severe sight-threatening retinal disease caused by human cytomegalovirus (HCMV) that remains today a significant cause of vision loss and blindness in untreated AIDS patients without access or sufficient response to combination antiretroviral therapy. Early investigations of AIDS-related HCMV retinitis quickly characterized its hallmark clinical features and unique histopathologic presentation but did not begin to identify the precise virologic and immunologic events that allow the onset and development of this retinal disease during HIV-induced immunosuppression. Toward this end, several mouse models of experimental cytomegalovirus retinitis have been developed to provide new insights into the pathophysiology of HCMV retinitis during AIDS. Herein, we provide a summary and comparison of these mouse models of AIDS-related HCMV retinitis with particular emphasis on one mouse model developed in our laboratory in which mice with a murine acquired immunodeficiency syndrome (MAIDS) of murine retrovirus origin develops a reproducible and well characterized retinitis following intraocular infection with murine cytomegalovirus (MCMV). The MAIDS model of MCMV retinitis has advanced the discovery of many clinically relevant virologic and immunologic mechanisms of virus-induced retinal tissue destruction that are discussed and summarized in this review. These findings may extend to the pathogenesis of AIDS-related HCMV retinitis and other AIDS-related opportunistic virus infections.