Human Hematopoietic Long-Term Culture (hLTC) for Human Cytomegalovirus Latency and Reactivation

Of the many research challenges posed by the study of human cytomegalovirus (HCMV) latency, one of the most notable is the requirement for the use of primary hematopoietic cell culture. Culturing hematopoietic progenitor subpopulations requires that consideration be given to maintaining their physiological relevance. We describe a long-standing primary CD34+ hematopoietic progenitor cell (HPC) system as an in vitro model to study HCMV latent infection. Key aspects of the model include infection of primary human CD34+ HPCs prior to ex vivo expansion, a long-term culture with a stromal cell support designed to maintain the ability of stem cells to support hematopoietic reconstitution, and an assay to quantify infectious centers produced prior to and following a reactivation stimulus. Importantly, this system has been used to identify a number of viral determinants of latency or reactivation and findings have been recapitulated in vivo using a humanized mouse model for HCMV latency. Therefore, this system offers a powerful approach to defining virus–host interactions and mechanisms important for HCMV latency and reactivation.