The Herpesvirus Family in the 21st Century

Eight members of the human herpesvirus (HHV) family have been discovered to date. All the viruses have a characteristic virion structure and share a number of other features. From the perspective of potential treatments, these include the encoding of a protease enzyme which is essential for virus assembly, a DNA polymerase and at least one kinase enzyme which can phosphorylate nucleosides. The herpesviruses also demonstrate a number of mechanisms for avoiding the host immune system, including interference with different stages of the presentation of viral peptides on the cell surface by class I human leukcocyte antigen (HLA) proteins. Three members of the herpesvirus family (HHV-6, HHV-7 and HHV-8) have been discovered within the last 10 years. Both HHV-6 and HHV-7 cause exonthem subitum, although HHV-7 seems to be less pathogenic than HHV-6. HHV-6 also appears to be associated with a number of other disorders. HHV-8 was discovered by the newly developed technique of representational difference analysis, and was identified in Kaposi's sarcoma (KS) tissue. Although the studies to date do not prove that HHV-8 causes KS, they show that the virus is closely associated with the disease. Since discovery of these HHV has been facilitated by the development of new techniques, further technological advances could help to uncover new members of the family.