Chemokine receptor trafficking and viral replication.

Chemokines and chemokine receptors have emerged as crucial factors controlling the development and function of leukocytes. Recent studies have indicated that, in addition to these essential roles, both chemokines and chemokine receptors play critical roles in viral infection and replication. Not only are chemokine receptors key components of the receptor/fusion complexes of primate immunodeficiency viruses, but chemokines can also influence virus entry and infection. Many viruses, in particular herpesviruses, encode chemokines and chemokine receptors that influence the replication of both the parent virus and other unrelated viruses. The cell surface expression of the chemokine receptors is regulated through their interaction with membrane trafficking pathways. Ligands induce receptor internalization and downmodulation through endocytosis, and recycling is regulated within endosomes. Part of the mechanism through which chemokines protect cells from HIV infection is through ligand-induced internalization of the specific chemokine receptor co-receptors. In addition, mechanisms may exist to regulate the trafficking of newly synthesized receptors to the cell surface. Here we discuss aspects of the mechanisms through which chemokine receptors interact with membrane-trafficking pathways and the influence of these interactions on viral replication.