Background: Monocytes are suggested to harbor latent cytomegalovirus (CMV) in peripheral blood, which concurs with the finding that all CMV-susceptible cells carry the CD13 surface molecule. Here, we investigated whether all latently and productively CMV-infected peripheral blood mononuclear cells (PBMCs) could be eliminated by depletion of CD13-expressing cells.
Methods: Depletion of CD13-positive cells was performed with monoclonal antibodies and magnetic cell separation (MACS) beads followed by MACS. CMV DNA and cDNA were amplified by polymerase chain reaction with specific primers for two CMV genes, major immediate early and phosphoprotein 150. The presence of infectious virus was tested by incubating homogenized in vitro- or in vivo-infected PBMCs with human fibroblasts. CMV infection of fibroblasts was detected by intracellular expression of CMV proteins.
Results: Elimination of CD13-positive PBMCs removed productively in vitro- and in vivo-infected cells, as demonstrated by detection of infectious virus only in PBMC fractions containing CD13-positive cells. In support of this finding, CMV RNA was not detected in pure CD13-negative cell fractions. Furthermore, CMV DNA was found exclusively in CD13-positive PBMCs obtained from patients with acute CMV infection.
Conclusions: Our data suggest that CMV replicates exclusively in CD13-positive PBMCs. These findings have important clinical applications, because the elimination of CD13-positive cells may reduce the risk for transmission of latent CMV in blood products and bone marrow grafts and thereby also decrease the risk for CMV-induced complications, such as chronic graft-versus-host disease in bone marrow transplant patients.