Human herpesvirus 7, reported in 1990 is a lymphotropic member of the betaherpesvirus subfamily of herpesviruses. The virus is highly seroprevalent, primary
infection usually occurs during childhood, and it has been associated with cases of
exanthem subitum,
pityriasis rosea,
neurological manifestations and transplant complications. The latter two may warrant
antiviral intervention, 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 salivary gland tissue from which infectious virus is constitutively shed in saliva. The HHV-7 genome is approximately 145 kb and encodes at least 84 different
proteins. Studies characterising HHV-7 gene products and the required interactions between viral and cellular genes necessary for virus replication, persistence and latency are in their infancy. HHV-7
infection has a variety of effects on host cells including upregulation of
interleukin 15 and down-modulation of the cell surface molecule CD4; the latter serves as the 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.