Over the Fence or Through the Gate: How Viruses Infect Polarized Cells

Abstract

Polarized epithelial and endothelial layers in multi cellular organisms constitute the first line of defense from the environment. These highly specialized cells possess tight junctions and regulate the passage of substances into and out of organs such as the gut, lung, liver and brain. An increasing number of viruses can overcome these barriers to gain access to underlying tissues. Different virus families have evolved a variety of strategies to enter polarized cells, including: the transcytosis of virus–immune complexes; engagement of apically expressed receptors and virus–receptor-dependent endocytosis; ligation of signaling receptors that promote actin cytoskeletal reorganization; and lateral diffusion of virus–receptor complexes to tight junctions (reviewed in [1]). Recent studies highlighted in this article reveal new mechanisms by which viruses utilize antiviral immune responses to enter polarized cells and to disseminate in vivo.