Herpes simplex virus type 1 infection of polarized epithelial cells requires microtubules and access to receptors present at cell-cell contact sites.

Mucosal epithelia are invaded from the apical surface during a primary infection by herpes simplex virus type 1 (HSV-1). HSV-1 progeny virus, synthesized from latently infected peripheral neurons that innervate such epithelia, reinfects the epithelia most likely from the basolateral surface. The epithelial cell lines MDCK and Caco-2 can be induced in vitro to differentiate into polarized cells with distinct apical and plasma membrane domains separated by tight junctions if they are cultured on porous membrane filters. Our data using these culture systems showed that highly polarized epithelial cells were not susceptible to apical HSV-1 infection. However, HSV-1 infected these cells if added from the basolateral surface or if a depletion of extracellular Ca(2+) had weakened the strength of the cell-cell contacts. Basolateral infection and apical infection after the Ca(2+) switch required an intact microtubule network for genome targeting to the nucleus. This system can be used to identify the microtubule motors that HSV-1 uses during virus entry in polarized epithelial cells.