Abstract
In human cytomegalovirus (HCMV)-seropositive patients, CD34(+) hematopoietic progenitor cells (HPCs) provide an important source of latent virus that reactivates following cellular differentiation into tissue macrophages. Multiple groups have used primary CD34(+) HPCs to investigate mechanisms of viral latency. However, analyses of mechanisms of HCMV latency have been hampered by the genetic variability of CD34(+) HPCs from different donors, availability of cells, and low frequency of reactivation. In addition, multiple progenitor cell types express surface CD34, and the frequencies of these populations differ depending on the tissue source of the cells and culture conditions in vitro In this study, we generated CD34(+) progenitor cells from two different embryonic stem cell (ESC) lines, WA01 and WA09, to circumvent limitations associated with primary CD34(+) HPCs. HCMV infection of CD34(+) HPCs derived from either WA01 or WA09 ESCs supported HCMV latency and induced myelosuppression similar to infection of primary CD34(+) HPCs. Analysis of HCMV-infected primary or ESC-derived CD34(+) HPC subpopulations indicated that HCMV was able to establish latency and reactivate in CD38(+) CD90(+) and CD38(+/low) CD90(-) HPCs but persistently infected CD38(-) CD90(+) cells to produce infectious virus. These results indicate that ESC-derived CD34(+) HPCs can be used as a model for HCMV latency and that the virus either latently or persistently infects specific subpopulations of CD34(+) cells.IMPORTANCE Human cytomegalovirus infection is associated with severe disease in transplant patients and understanding how latency and reactivation occur in stem cell populations is essential to understand disease. CD34(+) hematopoietic progenitor cells (HPCs) are a critical viral reservoir; however, these cells are a heterogeneous pool with donor-to-donor variation in functional, genetic, and phenotypic characteristics. We generated a novel system using embryonic stem cell lines to model HCMV latency and reactivation in HPCs with a consistent cellular background. Our study defined three key stem cell subsets with differentially regulated latent and replicative states, which provide cellular candidates for isolation and treatment of transplant-mediated disease. This work provides a direction toward developing strategies to control the switch between latency and reactivation.