Animal Viruses
 
Viruses have long been invisible partners, because of small size of their particles, of life on this planet, including animals, and the discipline of virology was born only 100 years ago. Compared to cells, virus particles have much simpler structures, with splendid regularity (see Fig. 1 of Virus Infection, Animal). Therefore, X-ray crystallographic studies have been performed successfully for some kinds of viruses and have generated precise structures of the whole virion particles. These structural studies give an insight into molecular basis of interaction of proteins in assembled proteins of virion particles.
Viruses carry their own genomes that encode the genetic information for their replication in infected cells. Because of being obligatory parasites of host cells, viruses largely depend on host components and metabolism for their replication. In general, viruses use macromolecular biosynthesis pathways common to those in host cells. They often have, however, special mechanisms of DNA replication and gene expression that give advantage to viruses in the competition for cellular resources, resulting in death or immortalization of the host cells. Thus studies of virus replication have frequently led to discoveries of novel mechanisms in infected cells.
A number of molecular interactions between viral and host factors occur in infected hosts. Development of virus diseases must reflect the sum total of the interactions between virus and cells involved in the virus-specific response to replication, dissemination in an entire body, and host immune responses. Virus replications are actually limited to specific species, tissues, and cell types within hosts. These virus responses must be due to the distribution of host factors that support the virus replication. As such host factors, new molecules with unknown natural functions may be discovered, and new research projects with such molecules may open in other fields of the life
sciences, such as cell biology. New functions of known molecules may also be found. Thus, identification of host factors affecting the virus replication and dissemination is very important for understanding the development of virus diseases, as well as of host mechanisms at molecular level. Complete understanding of the molecular basis of virus pathogenicity and replication in a whole body would help in the use of viruses as virus-related expression vectors in future gene therapy.
Animal virology has always been one of the leading edges in the field of molecular biology. This volume contains current molecular biological information available from studies on representative animal viruses, and individual entries describe the most recent molecular biological information of a particular virus: adenovirus, cytomegalovirus, Epstein–Barr virus, helper virus, hepatitis B virus, herpesvirus, HIV, influenza virus, papovavirus, poliovirus, polyomavirus, reovirus, rhinovirus, Rous sarcoma virus, Semliki Forest virus, Sendai virus, SV40, vaccinia virus, and vesicular stomatitis virus. The information contained is unlikely to be altered in the future, although new and important concepts of the field of animal virology will continue to contribute to all of the life sciences.