An in vitro model for the regulation of human cytomegalovirus latency and reactivation in dendritic cells by chromatin remodelling

1 Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Level 5 Box 157, Hills Road, Cambridge CB2 2QQ, UK 2 Cambridge Institute for Medical Research, School of Clinical Medicine, University of Cambridge, Addenbrooke's Hospital, Level 5 Box 157, Hills Road, Cambridge CB2 2QQ, UK Correspondence J. H. Sinclair js{at}mole.bio.cam.ac.uk Human cytomegalovirus (HCMV) is a frequent cause of major disease following primary infection or reactivation from latency in immunocompromised patients. Infection of non-permissive mononuclear cells is used for analyses of HCMV latency in vitro . Using this approach, it is shown here that repression of lytic gene expression following experimental infection of CD34 + cells, a site of HCMV latency in vivo , correlates with recruitment of repressive chromatin around the major immediate-early promoter (MIEP). Furthermore, long-term culture of CD34 + cells results in carriage of viral genomes in which the MIEP remains associated with transcriptionally repressive chromatin. Finally, specific differentiation of long-term cultures of infected CD34 + cells to mature dendritic cells results in acetylation of histones bound to the MIEP, concomitant loss of heterochromatin protein 1 and the reactivation of HCMV. These data are consistent with ex vivo analyses of latency and may provide a model for further analyses of the mechanisms involved during latency and reactivation. Published online ahead of print on 31 August 2005 as DOI 10.1099/vir.0.81161-0.