Introduction

A virus receptor is defined as a component of the cell surface that contains a domain which is structurally and conformationally complementary with a domain on the viral attachment protein (VAP) and forms a stable complex with the VAP. Association of the VAP with the receptor is followed by a biological response which may include internalization and replication of the virus, cytopathic changes in the cell, activation of second messenger systems, inhibition of host protein synthesis, or down regulation of receptors. The interaction with the host cell receptor is the initial stage in the viral infectious cycle. Besides being necessary for entrance of the virus into the cell, the receptor plays a major role in determining cell and species tropisms. Binding of virions to host cell receptors places them in intimate physical contact with the cell surface, and sets the stage for crossing the membrane barrier. Viruses then enter the cell either by direct fusion with the plasma membrane or by adsorptive- or receptor-mediated endocytosis. Many viruses have been shown to enter by both mechanisms, although some may preferentially utilize one of the two pathways. With either process, the viral genome gains entrance to the cytoplasm without lysing the cell membrane, which would be fatal to the cell. Paulson (1985) and Marsh and Helenius (1989) reviewed data on the entry of enveloped and non-enveloped viruses into cells.

Virus receptors

Any normal constituent comprising or associated with the cell membrane of the host cell is potentially a virus receptor.