Rhinovirus C Targets Ciliated Respiratory Epithelial Cells

Rationale:  The Rhinovirus C (RV-C) produce high symptom burdens in children and asthmatics, however, their primary target host cell in the airways remains unknown.  We hypothesized that the RV-C target ciliated respiratory epithelial cells (RECs), 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).  We further hypothesized that ciliated tissues are required for susceptibility to the RV-C in the upper respiratory tract.

Methods:  RV-C15 infection and target cell morphology were assessed using immunofluorescent and time-lapse epifluorescent imaging in REC cultures, and immunohistochemistry and flow cytometry of differentiated RECs, sinus, adenoid, and tonsil epithelium, respectively.

Results:  RV-C15 produced a scattered pattern of infection, and infected epithelial cells were shed.  RV-C15 inoculation resulted in the infection of 1.4-12% of cultured cells.  Infected cells stained positively for acetylated-alpha-tubulin (aat, p<0.001) but not wheat germ agglutinin or Muc5AC (p=ns).  The uninfected ciliated cell population expressed 2.2-fold more CDHR3 than other epithelial cell populations (p<0.001). RV-C15 inoculation reduced the CDHR3 expressing ciliated cell population from 70 to 58% (p<0.001).  RV-C15 replicated in sinus and adenoid, but not tonsil epithelium following ex vivo inoculation.

Conclusions:  In summary, the RV-C replicate only in ciliated RECs in vitro and CDHR3 expression is largely confined to ciliated RECs. Accordingly, sinus and adenoid tissues (ciliated epithelium) but not tonsils (nonciliated epithelium) were susceptible to RV-C infection ex vivo.  These findings suggest that factors regulating ciliary differentiation and CDHR3 expression may be important determinants of RV-C illness severity.