Human coronaviruses: A brief review

At the beginning of this century, most of the effort aimed at defining the cause of common colds was spent searching for a bacterial aetiology. It was not until the work of Dochez and his colleagues at the Rockefeller Institute in New York in the 1930s that viruses were considered to be the likely causative agents.’ Their work with chimpanzees and human volunteers showed that filtered nasal secretions were able to cause colds in inoculated chimpanzees and isolated volunteers. The next major advance awaited the development of cell culture techniques in the 1950s when Enders showed that poliomyelitis virus could be propagated in human kidney cells. This technique was applied to the isolation of common cold viruses, and in 1956 ECHO 28 (also initially called J.H. or 2060) was isolated in monkey kidney cells;’ this virus is now known to be a rhinovirus. By 1965, it was known that as well as rhinoviruses, adenoviruses, myxoviruses (influenza and parainfluenza viruses and respiratory syncytial virus) and enteroviruses were all causative agents of the common cold. Yet, a substantial proportion of colds seemed not to be due to any of these. Using human fetal tracheal organ culture, Tyrrell and Bynoe in Salisbury cultivated a virus that they termed €3814 agent from the nasal washing and swab taken from a schoolboy with a cold in 1960.3 This nasal washing, number B814, was able to cause cold symptoms in 5 of 1 I volunteers inoculated intranasally. B814 agent was ether labile and could pass through a bacteria-tight filter. It could reduce the ciliary activity of organ tissue, and could also be detected by virus interference in these organ cultures. At the same time as the Salisbury team were discovering B814, Hamre and Procknow in Chicago were reporting another new virus cultivatable in human embryo kidney cells from nasal secretions collected from a group of medical students in 1962.4 Virus was grown from five individuals, four of whom had been suffering from a cold. One isolate from student specimen 229E was chosen as the prototype strain and further characterised. It was shown to be ether-labile, about 89pm in diameter, and had an RNA genome. Electron microscope examination of both B814 and 229E viruses showed them to be morphologically identical to avian infectious bronchitis virus and mouse hepatitis virus. These