Togaviruses: Molecular Biology

This article addresses important aspects of the molecular biology of viruses in the genera Alphavirus and Rubivirus, family Togaviridae. First, the structure of the virus particle and the organization of the genome are described, highlighting important commonalities and differences between the two genera. A comprehensive review is then provided of the sequential steps occurring during virus infection and replication including: (1) virion binding to cell surface receptors, entry into the host cell, and uncoating of the genomic RNA; (2) translation of the nonstructural proteins (the replication machinery), transcription, and replication of the genome in the cytoplasm of the infected cell; and (3) translation and maturation of the viral structural proteins, packaging of the genome into nucleocapsids, and budding of enveloped progeny virions from the cell's plasma membrane. The way in which the virus replication scheme has facilitated the development of togavirus infectious clone technology is also outlined. Finally, our current understanding of the battle which ensues between the infecting virus and the targeted host cell is discussed, addressing issues of cell viability versus cytopathic effect, shut-off of host versus viral protein synthesis, and sensitivity or resistance to the interferon-mediated antiviral response.