Human herpesvirus 7

Human herpesvirus 7, reported in 1990 is a lymphotropic member of the betah erpesvirus subfamily of herpesviruses. The virus is highly seroprevalent, p rimary infection usually occurs during childhood, and it has been associate d with cases of exanthem subitum, pityriasis rosea, neurological manifestat ions and transplant complications. The latter two may warrant antiviral int ervention, in vitro studies have shown that HHV-7 is susceptible to several nucleoside phosphonate compounds. In vitro, the virus has approximately a 5 day growth cycle in cultured lymphocytes; in vivo, latency is established in peripheral blood T-cells and a persistent infection is established in s alivary gland tissue from which infectious virus is constitutively shed in saliva. The HHV-7 genome is approximately 145 kb and encodes at least 84 di fferent proteins. Studies characterising HHV-7 gene products and the requir ed interactions between viral and cellular genes necessary for virus replic ation, persistence and latency are in their infancy. HHV-7 infection has a variety of effects on host cells including upregulation of interleukin 15 a nd down-modulation of the cell surface molecule CD4; the latter serves as t he cellular membrane receptor for HHV-7. Since HIV also infects T-cells via the CD4 molecule, the interactions of these viruses within T-cells during the course of AIDS are important areas of investigation.