SARS­CoV­2 spike protein­induced host inflammatory response signature in human corneal epithelial cells.

Coronavirus disease 2019 (COVID­19), caused by the severe acute respiratory syndrome coronavirus­2 (SARS­CoV­2), led to an outbreak of viral pneumonia in December 2019. The present study aimed to investigate the host inflammatory response signature­caused by SARS­CoV­2 in human corneal epithelial cells (HCECs). The expression level of angiotensin­converting enzyme 2 (ACE2) in the human cornea was determined via immunofluorescence. In vitro experiments were performed in HCECs stimulated with the SARS­CoV­2 spike protein. Moreover, the expression levels of ACE2, IL­8, TNF­α, IL­6, gasdermin D (GSDMD) and IL­1ß in HCECs were detected using reverse transcription­quantitative PCR and/or western blotting. It was identified that ACE2 was expressed in normal human corneal epithelium and HCECs cultured in vitro. Furthermore, the expression levels of IL­8, TNF­α and IL­6 in HCECs were decreased following SARS­CoV­2 spike protein stimulation, while the expression levels of GSDMD and IL­1ß were increased. In conclusion, the present results demonstrated that the SARS­CoV­2 spike protein suppressed the host inflammatory response and induced pyroptosis in HCECs. Therefore, blocking the ACE2 receptor in HCECs may reduce the infection rate of COVID­19.

Co-expression of SARS-CoV-2 entry genes in the superficial adult human conjunctival, limbal and corneal epithelium suggests an additional route of entry via the ocular surface.

PURPOSE: The high infection rate of SARS-CoV-2 necessitates the need for multiple studies identifying the molecular mechanisms that facilitate the viral entry and propagation. Currently the potential extra-respiratory transmission routes of SARS-CoV-2 remain unclear. METHODS: Using single-cell RNA Seq and ATAC-Seq datasets and immunohistochemical analysis, we investigated SARS-CoV-2 tropism in the embryonic, fetal and adult human ocular surface. RESULTS: The co-expression of ACE2 receptor and entry protease TMPRSS2 was detected in the human adult conjunctival, limbal and corneal epithelium, but not in the embryonic and fetal ocular surface up to 21 post conception weeks. These expression patterns were corroborated by the single cell ATAC-Seq data, which revealed a permissive chromatin in ACE2 and TMPRSS2 loci in the adult conjunctival, limbal and corneal epithelium. Co-expression of ACE2 and TMPRSS2 was strongly detected in the superficial limbal, corneal and conjunctival epithelium, implicating these as target entry cells for SARS-CoV-2 in the ocular surface. Strikingly, we also identified the key pro-inflammatory signals TNF, NFKß and IFNG as upstream regulators of the transcriptional profile of ACE2+TMPRSS2+ cells in the superficial conjunctival epithelium, suggesting that SARS-CoV-2 may utilise inflammatory driven upregulation of ACE2 and TMPRSS2 expression to enhance infection in ocular surface. CONCLUSIONS: Together our data indicate that the human ocular surface epithelium provides an additional entry portal for SARS-CoV-2, which may exploit inflammatory driven upregulation of ACE2 and TMPRSS2 entry factors to enhance infection.

Susceptibility of eye mucosa to SARS CoV-2: sanitary biosecurity / Susceptibilidad de las mucosas oculares al SARS COV-2: bioseguridad sanitaria

RESUMEN: El SARS CoV-2, agente causal de la enfermedad llamada Covid-19, infecta las mucosas digestivas y respiratorias, afectando las células epiteliales. El virus ingresa a través del receptor de membrana ACE2 provocando la disrupción de la homeostasis celular. Frecuentes reportes indican la presencia de conjuntivitis ocular en pacientes diagnosticadas con Covid-19, lo cual ha alertado a los científicos sobre el potencial foco de infección viral de las secresiones lagrimales.Los epitelios de la conjuntiva ocular sub-palpebral y corneal, se caracterizan por presentar el receptor de la enzima convertidora de angiotensina 2 (ACE2) y proteasa transmembrana asociada serina 2 (TMPRSS2), cuya interacción activa los mecanismos de liberación de citoquinas, capaces de instalar un proceso de conjuntivitis infecciosa por SARS CoV-2, pero no necesariamente hacer extensiva la infección hacia los sistemas digestivo y respiratorio.Aunque este proceso inflamatorio es más frecuente como una expresión de la infección general y más grave. Sin embargo, cualquiera sea la vía de infección o ingreso del virus SARS CoV-2 es importante considerar el riesgo de infectividad de las lágrimas y las secresiones conjuntivales en los pacientes. Este estudio pretende llamar la atención sobre las medidas de cuidados y control sanitario, incorporando mejores normas de protección personal y bioseguridad, especialmente en el áreas de oftalmología, asumiendo que la mucosa ocular puede ser una vía de entrada del virus y a la vez una fuente de contagio.También considerar la potenciación de la infección viral con las enfermedades de base asociadas, como glaucoma y diabetes.Se sugiere además incorporar estudios histológicos de la mucosa ocular para diferenciar epitelios sanos e infectados.

SUMMARY: SARS CoV-2, the causal agent of the Covid- 19 disease, infects the digestive and respiratory mucosa, affecting epithelial cells. The virus enters through the ACE2 membrane receptor causing the disruption of cell homeostasis. Frequent reports indicate the presence of ocular conjunctivitis in patients diagnosed with Covid-19, which has alerted scientists to the potential source of viral infection from lacrimal secretions. The epithelia of the sub-palpebral and corneal ocular conjunctiva are characterized by presenting the receptor for angiotensin-converting enzyme 2 (ACE2) and associated transmembrane protease serine 2 (TMPRSS2), whose interaction activates cytokine release mechanisms, with the ability to start the infectious conjunctivitis process by SARS CoV-2, but not necessarily extend the infection to the digestive and respiratory systems. Although this inflammatory process is more frequent as an expression of the general and more serious infection. However, whatever the route of infection or entry of the SARS CoV-2 virus, it is important to consider the risk of infection of tears and conjunctival secretions in patients. This study aims to draw attention to health care and control measures, incorporating better standards of personal protection and biosafety, especially in the areas of ophthalmology, assuming that the ocular mucosa can be a route of entry for the virus, and at the same time a source of contagion. A further consideration is the potential of viral infection with associated underlying diseases, such as glaucoma and diabetes. It is also suggested to incorporate histological studies of the ocular mucosa to differentiate healthy and infected epithelia.