[Blood leukocytes are not a primary latent site of cytomegalovirus]

Conflicting results do exist regarding blood leukocytes as a site of CMV latency. In an attempt to detect latently infected blood cells we studied CMV major immediate early (MIE) antigen expression in monocytes or mononuclear leukocytes from 80 blood donors (71 seropositive) after in vitro stimulation and subsequent antigen detection by immunocytochemistry (detection limit 1 positive cell/10(6) cells). None of the more than 800 cytospin preparations investigated turned out to be positive. Additionally the granulocyte macrophage colony stimulating factor (GM-CSF)/hydrocortisone (HC) stimulated monocytes were analysed by reverse transcriptase PCR for the presence of MIE mRNA and were also completely negative. In contrast to the negative findings in blood samples, we detected CMV DNA by PCR in 6 out of 20 suddenly deceased individuals in tissue samples of the lung, but not in those of other organs. We conclude that we have no evidence that blood leukocytes are a site of latent CMV. The transmission of CMV by blood transfusions may be mediated by rare phagocytes that transiently bear CMV after uptake from infected endothelial cells.