Human cytomegalovirus reactivation in bone-marrow-derived granulocyte/monocyte progenitor cells and mature monocytes

Monocyte/granulocyte progenitor cells of the bone marrow are a major site of human cytomegalovirus (HCMV) latency. The mechanisms of establishment and maintenance of HCMV latency are still unknown. Reactivation of the latent virus in bone-marrow-derived progenitor cells has been demonstrated in vitro and suggested to occur also in vivo. Clinical studies have shown that reactivation is a rather frequent event not only in immunosuppressed but also in nonimmunosuppressed patients and in healthy blood donors. At least three independent mechanisms of virus reactivation are discussed: systemic inflammation connected with strong tumor necrosis factor alpha release; application of cAMP-elevating drugs, and highly stressful events associated with increased plasma catecholamine levels.