Polarity influences the efficiency of recombinant adenoassociated virus infection in differentiated airway epithelia.

To better understand mechanisms that limit rAAV transduction in the lung, we have evaluated several unique features of rAAV infection in polarized primary airway epithelial cultures. rAAV was found to transduce the basolateral surface of airway epithelia 200-fold more efficiently than the apical membrane. These differences in membrane infection correlated with the abundance of apical heparan sulfate proteoglycan (AAV-2 receptor) and virus binding. UV irradiation augmented rAAV transduction greater than 20-fold, only when virus was applied to the apical membrane. Ultrastructural analysis of UV-irradiated primary cultures demonstrated significant changes in microvilli architecture following exposure to 25 J/m2 UV. Although virus binding and the abundance of heparan sulfate proteoglycan were not increased at the apical membrane following UV irradiation, increased receptor-independent endocytosis of fluorescent beads was seen at the apical membrane following UV irradiation. We hypothesize that endocytotic processes associated with apical membrane-specific pathways of viral entry, and/or processing of virus to the nucleus, may be altered following UV irradiation. Interestingly, UV irradiation had an inhibitory effect on rAAV transduction from the basolateral membrane, which correlated with a decrease in the abundance of heparan sulfate proteoglycan at the basal membrane. In summary, these findings suggest that independent pathways of viral transduction may occur in the apical and basolateral compartments of polarized airway epithelia.