Polarization of viral entry and release in epithelial cells

Epithelial cells line the body and organ surfaces, and form a barrier to virus entry as well as to dissemination of progeny virus in the infected host. Epithelial cells are typically polarized and exhibit two distinct surface domains. Viruses may enter polarized epithelial cells through only one membrane surface and not the other, thus restricting sites which are susceptible to infection. Furthermore, the release of many viruses from epithelial cells is directional, which may have important implications in pathogenesis. The restricted sites of viral entry and release are also important determinants of the availability of viral components for interaction with the immune system.