Treating SARS-CoV-2 infection in human 3D respiratory models

The current Coronavirus disease (COVID-19) pandemic has far-reaching consequences with a disruption of modern society never witnessed before by locking much of the world down, crashing economies or health care services to name a few. The infectious agent causing COVID-19 is the virus SARS-CoV-2. Its extremely rapid spread within populations around the globe increases the demand for understanding the pathogenicity of the virus during entry via respiratory tissues as well as for testing effective drugs or novel vaccination strategies to being armed against future attacks by the virus. During the last months, asymptomatic to mild to very severe courses upon infection with SARS-CoV-2 were reported, raising questions about the factors involved in these differences. Recently, we developed an optimized respiratory human 3D system model system, which mimics the upper and lower respiratory tract and is therefore ideal for the investigation of SARS-CoV-2 infections. In addition, immune cells can be included to this respiratory model and relevant scenarios of host-pathogen interaction can be investigated. During CURE we aim to (i) monitor the pathogenesis of SARS-CoV-2 during early transmission events and characterize tissue and cellular damage, (ii)investigate immune-mediated mechanisms in the early and late phase of infection, and (iii) test possible treatment options using drugs already approved for other diseases. Our respiratory 3D tissue model will contribute to additional treatment options for COVID-19 patients and furthermore provide new knowledge on tissue damage and viral transmission.

The COVID 19 pandemic has shown how profoundly a novel respiratory virus can strain health systems and societies. SARS CoV 2 can also cause highly variable outcomes, from asymptomatic infection to severe disease. The CURE project aimed to clarify key disease mechanisms and immune mediated factors in a human relevant experimental system and to derive implications for therapy and prevention. A core project result was the establishment and use of a complex human respiratory 3D tissue model for SARS CoV 2 research. The model reproduces central features of the upper and lower airways, including epithelial barrier function, cellular differentiation, and mucosal properties, and enables controlled infection with defined viral variants. A major advantage is the option to integrate immune cells, allowing analysis of early and late host pathogen interactions and downstream inflammatory processes in a physiologically meaningful setting. Using this platform, virus induced tissue and cellular damage was systematically characterized and linked to inflammatory response patterns. Variant comparisons indicated that Omicron subvariants in respiratory tissue can show reduced penetration, less epithelial injury, and attenuated inflammatory responses compared with earlier variants, while still affecting barrier integrity and immune activation. In parallel, infection associated regulatory programs in epithelial cells were investigated, including the role of non coding RNAs as modulators of antiviral responses and inflammation. A key focus was adaptive immunity, particularly T cells. Evidence from clinical observations and model based analyses supports that robust SARS CoV 2 specific T cell responses are associated with milder disease and contribute to viral control, even when neutralizing antibody activity against emerging variants varies strongly between individuals. This underlines T cells as an important correlate of protection and helps explain why individuals with similar antibody measures may experience different clinical courses. The project also showed that vaccination and booster regimens shape cellular and humoral immunity in distinct ways, and that targeted boosting can be especially relevant in older populations to sustain reliable T cell and antibody responses against variants. Therapeutic work addressed two complementary levels. First, drug repurposing tested approved compounds in a human relevant infection model. Antiviral agents suppressed viral replication even for strongly immune evasive Omicron lineages, but this did not necessarily translate into a proportional reduction of tissue inflammation, supporting combined strategies that address viral load and immunopathology as partially independent targets. Second, locally acting barrier protective approaches were evaluated in human airway epithelial cultures with the aim of stabilizing epithelial integrity and reducing viral burden. Overall, the CURE project provides an animal sparing human respiratory test system and delivers deeper insights into SARS CoV 2 pathogenesis, variant dependent effects, and the importance of T cell immunity and inflammatory control, supporting the prioritization of future interventions and therapeutic concepts.