For a virus to invade a host cell it needs to penetrate the physical barrier imposed by the plasma membrane. Viruses have evolved specialized surface proteins to meet this challenge. These proteins facilitate delivery of the viral genetic information into the host cell by either fusing the viral envelope with a host cell membrane or by forming membrane pores. Membrane fusion and pore formation critically depend on the engagement of host cell receptors and receptor choice is a key determinant of viral tropism. The multi-faceted interplay between viral and cellular factors during virus entry is a fascinating field of study, which can provide important insight into viral pathogenesis and define new targets for intervention. This book provides a comprehensive overview of this exciting field of research.

STEFA N PÖHLMANN is Professor for Infection Biology and Head of the Infection Biology Unit of the German Primate Center. His research is focused on virus host cell interactions, particularly on the molecular processes underlying host cell entry of human immunodeficiency virus and emerging viruses. Stefan Pöhlmann received his academic degrees (Dr. rer. nat., venia legendi) from the FriedrichAlexanderUniversity ErlangenNurnberg. Before his appointment at the German Primate Center, he worked as a postdoctoral fellow at the University of Pennsylvania, as a junior research group leader at the FriedrichAlexanderUniversity ErlangenNurnberg and as an assistant professor at Hannover Medical School. He serves on the editorial board of theJournal of VirologyandVirologyand serves as academic editor forPLoS ONE.

GRAHAM SIMMONS is an Associate Investigator at Blood Systems Research Institute and Associate Professor in the Department of Laboratory Medicine at the University of California, San Francisco. He is interested in many aspects of viral entry, particularly for blood transfusion transmissible agents and other emerging and reemerging viruses that may be a threat to the blood supply. Graham Simmons received his doctoral training from the Institute of Cancer Research in London prior to performing an EMBOsponsored postdoctoral fellowship at the University of Pennsylvania.

Attachment Factors.- Picornavirus Entry.- Reovirus Receptors, Cell Entry, and Proapoptotic Signaling.- Entry of Influenza Virus.- Filovirus Entry.- Paramyxovirus Entry.- Cellular entry of retroviruses.- Class II Fusion Proteins.- Entry of Rhabdoviruses into Animal Cells.- Entry of Herpesviruses into Cells: The Enigma Variations.