Rhinovirus C targets ciliated airway epithelial cells

Background: The Rhinovirus C (RV-C), first identified in 2006, produce high symptom burdens in children and asthmatics, however, their primary target host cell in the airways remains unknown. Our primary hypotheses were that RV-C target ciliated airway epithelial cells (AECs), and that cell specificity is determined by restricted and high expression of the only known RV-C cell-entry factor, cadherin related family member 3 (CDHR3).

Methods: RV-C15 (C15) infection in differentiated human bronchial epithelial cell (HBEC) cultures was assessed using immunofluorescent and time-lapse epifluorescent imaging. Morphology of C15-infected differentiated AECs was assessed by immunohistochemistry.

Results: C15 produced a scattered pattern of infection, and infected cells were shed from the epithelium. The percentage of cells infected with C15 varied from 1.4 to 14.7% depending on cell culture conditions. Infected cells had increased staining for markers of ciliated cells (acetylated-alpha-tubulin [aat], p < 0.001) but not markers of goblet cells (wheat germ agglutinin or Muc5AC, p = ns). CDHR3 expression was increased on ciliated epithelial cells, but not other epithelial cells (p < 0.01). C15 infection caused a 27.4% reduction of ciliated cells expressing CDHR3 (p < 0.01). During differentiation of AECs, CDHR3 expression progressively increased and correlated with both RV-C binding and replication.

Conclusions: The RV-C only replicate in ciliated AECs in vitro, leading to infected cell shedding. CDHR3 expression positively correlates with RV-C binding and replication, and is largely confined to ciliated AECs. Our data imply that factors regulating differentiation and CDHR3 production may be important determinants of RV-C illness severity.