Recovery from cytomegalovirus infection is associated with activation of peripheral blood lymphocytes

The number of CD8bright and CD56+ lymphocytes in the peripheral blood and their activation status were monitored by flow cytometry in 23 renal transplant recipients with cytomegalovirus (CMV) infection and were correlated with the virus load (as determined by CMV antigenemia) and clinical symptoms. Recovery from CMV infection coincided with expansion of the CD8bright and CD56+ subsets and with increased expression of the activation marker HLA-DR. Primary infection was associated with activation of both subsets, whereas during secondary infection, mainly CD8bright cells responded. Progressive CMV disease (requiring antiviral treatment) and relapse occurred in association with low numbers of activated CD8bright and CD56+ cells. Lymphocyte activation and antibody responses against CMV often occurred simultaneously, but different kinetics of these responses in some patients indicated that cellular responses are necessary to control viral replication, whereas humoral responses alone may be insufficient. Monitoring of lymphocyte activation may provide clinically useful information during CMV infection.