Human Nasal Turbinate Tissues in Organ Culture as a Model for Human Cytomegalovirus Infection at the Mucosal Entry Site

The initial events of viral infection at the primary mucosal entry site following horizontal person-to-person transmission have remained ill defined. Our limited understanding is further underscored by the absence of animal models in the case of human-restricted viruses, such as human cytomegalovirus (HCMV) - a leading cause of congenital infection and a major pathogen in immunocompromised individuals. Here we established a novel ex vivo model of HCMV infection in native human nasal turbinate tissues. Nasal-turbinate tissue viability and physiological functionality were preserved for at least seven days in culture. We found that nasal mucosal tissues were susceptible to HCMV infection, with predominant infection of ciliated respiratory epithelial cells. A limited viral spread was demonstrated, involving mainly stromal- and vascular endothelial cells within the tissue. Importantly, functional antiviral and pro-leukocyte-chemotactic signaling pathways were significantly upregulated in the nasal mucosa in response to infection. Conversely, HCMV downregulated the expression of nasal epithelial-cell related genes. We further revealed tissue-specific innate immune response patterns to HCMV, comparing infected human nasal-mucosal and placental tissues, representing the viral entry- and the maternal-to-fetal transmission site, respectively. Taken together, our studies provide insights into the earliest stages of HCMV infection. Studies in this model could help evaluate new interventions against the horizontal transmission of HCMV.IMPORTANCE HCMV is a ubiquitous human pathogen, causing neurodevelopmental disabilities in congenitally infected children and severe disease in immunocompromised patients. The earliest stages of HCMV infection in the human host have remained elusive in the absence of a model for the viral entry site. Here we describe the establishment and use of a novel nasal turbinate organ culture, to study the initial steps of viral infection and the consequent innate immune responses, within the natural complexity and the full cellular repertoire of human nasal mucosal tissues. This model can be applied to examine new antiviral interventions against the horizontal transmission of HCMV and potentially other viruses.