Circulating Dendritic Cells Isolated from Healthy Seropositive Donors Are Sites of Human Cytomegalovirus Reactivation In Vivo

Abstract

Primary infection with human cytomegalovirus (HCMV) is generally asymptomatic in healthy individuals and results in a lifelong infection of the host. In contrast, in immunosuppressed transplant recipients and late-stage AIDS patients, HCMV infection and reactivation can result in severe disease or death. In vivo, latency is established in bone marrow CD34؉ progenitor cells with reactivation linked with their differentiation to macrophages and dendritic cells (DCs). However, previous analyses have relied on ex vivo differentiation of myeloid progenitor cells to DCs in culture. Here, we now report on the isolation and analysis of circulating blood myeloid DCs, resulting from natural differentiation in vivo, from healthy HCMV-seropositive carriers. We show that these in vivo-differentiated circulating DCs are fully permissive for HCMV and exhibit a phenotype similar to that of monocyte-derived DCs routinely used for in vitro studies of HCMV. Importantly, we also show that these DCs from healthy HCMV-seropositive donors carry HCMV genomes and, significantly, are typically positive for viral immediate-early (IE) gene expression, in contrast to circulating monocytes, which carry genomes with an absence of IE expression. Finally, we show that HCMV reactivation from these circulating DCs is enhanced by inflammatory stimuli. Overall, these data argue that the differentiation in vivo of myeloid progenitors to circulating DCs promotes the reactivation of HCMV lytic gene expression in healthy individuals, thereby providing valuable confirmation of studies performed using in vitro generation of DCs from myeloid precursors to study HCMV reactivation.

The Association of Human Cytomegalovirus with Biomarkers of Inflammation and Immune Activation in HIV-1-Infected Women

“…4 At the same time, monocytes are known to be sites of CMV latency, 48 although they are not permissive for virus replication. In the absence of HIV-1, induction of replicating CMV has been shown to occur with the terminal differentiation of monocytes to myeloid dendritic cells, 49 and in vitro studies have demonstrated that monocyte to macrophage differentiation leads to production of infectious virus. [50][51][52] If HIV-1 infection activates monocytes and macrophages, 53 it is likely that CMV could be reactivated and replicate leading to an inflammatory response.…”

Cytomegalovirus-Associated CD4+CD28null Cells in NKG2D-Dependent Glomerular Endothelial Injury and Kidney Allograft Dysfunction

“…CMV prophylaxis with 100 days of valganciclovir was given to the D+RÀ serostatus group only, with dose adjustment for renal function. Serial whole blood samples were taken for CMV DNA polymerase chain reaction in all patients at day 0 (before transplantation) and then at weeks 1,2,3,4,6,8,10,12,16,20,24,28,34,40,46, and 52. The clinical team remained unaware of these results, and no changes in clinical management ensued (it is not unit policy to undertake viral load testing and preemptive therapy in the context of asymptomatic CMV infection, as is the case in most centers, so these assessments were undertaken for research purposes only).…”

Cell-type specific activities of cytomegalovirus GPCR homologues

“…It is well established that HCMV can infect and induce latency in pluripotent mononuclear cells in the bone marrow, particularly CD34 + . Even though monocytes carry the viral genome, replicating virus can only be detected upon cell differentiation (Goodrum et al, 2002;Hahn et al, 1998;Reeves & Sinclair, 2013). The inability of MCMV to produce progeny in the undifferentiated cells of the bone marrow does not exclude the possibility of initial stages of replication occurring, during the acute phase of infection, before latency be established.…”

“…It is well documented that MCMV can infect different cell types; however, it exhibits selectivity for specific cells at early points of infection (Hsu et al, 2009). Viral dissemination is mainly associated with cells from the myeloid lineage (Bale & O'Neil, 1989;Hanson et al, 1999;Noda et al, 2006;Stoddart et al, 1994), and mononuclear phagocytes (monocytes, macrophages and dendritic cells), the very first cellular defence against infection at entry sites, are recognized reservoirs of MCMV Hamano et al, 1998;Reeves & Sinclair, 2013;Stoddart et al, 1994).…”

“…Both of these cell types are permissive for viral productive infection, and expression of IE lytic genes can be detected in circulating cells. The immune system is responsible for restraining any viral reactivation attempts and serious symptoms are only observed in individuals with compromised immunity (Poole et al, 2015;Reeves & Sinclair, 2013;Towler et al, 2012).…”