Background-Human rhinoviruses (HRVs) characteristically cause upper respiratory tract infection but they also infect the lower airways causing acute bronchitis and exacerbating asthma.

in vitro studies of the effects of rhinovirus on human airway epithelium have used cells grown under conditions known to produce low levels of differentiation. The relevance of the results to native epithelium is questionable. Here we grew primary cultures of human tracheal or nasal epithelium under three conditions. One condition produced pseudostratified, mucociliary cells virtually indistinguishable from native epithelium. The other two conditions produced undifferentiated squamous cells lacking cilia. Cells were infected for 6 h with rhinovirus-16. After a 24-h incubation period, we determined levels of viral RNA in the cells, numbers of infectious viral particles released in the mucosal medium, expression of a variety of epithelial cytokines and other proteins, release of IL-6 and IL-8, and transepithelial electrical resistance and voltage. After infection, levels of viral RNA in the poorly differentiated cells were 30 or 130 times those in the differentiated. Furthermore, expression of mRNA for inflammatory cytokines, release of infectious particles, and release of IL-6 and IL-8 were closely correlated with the degree of viral infection. Thus well-differentiated cells are much more resistant to viral infection and its functional consequences than are poorly differentiated cells from the same source. ion transport; porous-bottomed inserts; short-circuit current; transepithelial electrical resistance RHINOVIRUS (RV) causes severalfold increases in the output of a variety inflammatory cytokines from human airway epithelial cell lines (29,41) and from primary cultures of human airway epithelium (18,23,31,39). However, the cell lines used (A549 and BEAS-2B) generally do not form tight junctions (17,25), and the primary cultures were grown on solid supports, an approach known to produce highly undifferentiated cells (36). We questioned whether results obtained on such cultures were really representative of viral infection of native epithelium. Accordingly, we have grown cells from the same tracheas and nasal scrapings under several different culture conditions to achieve a range of differentiation from a squamous to a full-blown pseudostratified, mucociliary phenotype. We then compared the susceptibility of these various cultures to viral infection. METHODS

Airway epithelial cultures are generally derived from tracheas postmortem or from surgical specimens of nasal polyps or turbinates. Scrapings of the mucosal surface have been little used as starting material for cultures because of their low yield of epithelial cells and their contamination with mucous secretions, blood, and underlying connective tissue. For the first time, we report that human airway epithelial cells obtained from nasal scrapings or bronchial brushings can be grown in culture to produce polarized cell sheets suitable for studies of vectorial transport.

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