title: Chromosomally integrated human herpesvirus 6: questions and answers.
abstract: Chromosomally integrated human herpesvirus 6 (ciHHV-6) is a condition in which the complete HHV-6 genome is integrated into the host germ line genome and is vertically transmitted in a Mendelian manner. The condition is found in less than 1% of controls in the USA and UK, but has been found at a somewhat higher prevalence in transplant recipients and other patient populations in several small studies. HHV-6 levels in whole blood that exceed 5.5 log10 copies/ml are strongly suggestive of ciHHV-6. Monitoring DNA load in plasma and serum is unreliable, both for identifying and for monitoring subjects with ciHHV-6 due to cell lysis and release of cellular DNA. High HHV-6 DNA loads associated with ciHHV-6 can lead to erroneous diagnosis of active infection. Transplant recipients with ciHHV-6 may be at increased risk for bacterial infection and graft rejection. ciHHV-6 can be induced to a state of active viral replication in vitro. It is not known whether ciHHV-6 individuals are put at clinical risk by the use of drugs that have been associated with HHV-6 reactivation in vivo or in vitro. Nonetheless, we urge careful observation when use of such drugs is indicated in individuals known to have ciHHV-6. Little is known about whether individuals with ciHHV-6 develop immune tolerance for viral proteins. Further research is needed to determine the role of ciHHV-6 in disease.
authors: Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI 48201, USA. ppellett@med.wayne.edu
authors: Philip E
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mesh_terms: D002877:Chromosomes, Human / Q000821:virology*; D015654:Herpesvirus 6, Human / Q000235:genetics / Q000502:physiology*; D006801:Humans; D019349:Roseolovirus Infections / Q000235:genetics / Q000821:virology*; D016662:Virus Integration