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

To better understand mechanisms that limit rAAV transduction in the lung, w e have evaluated several unique features of rAAV infection in polarized pri mary airway epithelial cultures. rAAV was found to transduce the basolatera l surface of airway epithelia 200-fold more efficiently than the apical mem brane. These differences in membrane infection correlated with the abundanc e of apical heparan sulfate proteoglycan (AAV-2 receptor) and virus binding . UV irradiation augmented rAAV transduction greater than 20-fold, only whe n 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/m(2) UV. Although virus binding and the abundance of heparan sulfate proteoglycan were not increased at the ap ical membrane following UV irradiation, increased receptor-independent endo cytosis of fluorescent beads was seen at the apical membrane following UV i rradiation. We hypothesize that endocytotic processes associated with apica l membrane-specific pathways of viral entry, and/or processing of virus to the nucleus, may be altered following UV irradiation. Interestingly, UV irr adiation had an inhibitory effect on rAAV transduction from the basolateral membrane, which correlated with a decrease in the abundance of heparan sul fate proteoglycan at the basal membrane. In summary, these findings suggest that independent pathways of viral transduction may occur in the apical an d basolateral compartments of polarized airway epithelia.