Transfusion-transmitted cytomegalovirus: behaviour of cell-free virus during blood component processing. A study on the safety of labile blood components in Switzerland.

backgroundNowadays, most blood products are leukocyte-reduced. After this procedure, the residual risk for transfusion transmitted cytomegalovirus (TT-CMV) is mostly attributed to cell-free viruses in the plasma of blood donors following primary infection or viral reactivation. Here, objectives are: 1) to study the behaviour of cell-free CMV through the blood component processing; 2) to determine the anti-CMV seroprevalence, the level of viremia, the window-period in blood donor population; and 3) to identify cases of TT-CMV in bone marrow transplant (BMT) recipients. MATERIALS AND

methodsCell-free CMV was injected into blood bags originating from regular donors. Blood components were processed according to either the CompoSelect

resultsCell-free CMV passes without any decrease in viral load through all stages of blood processing. The anti-CMV seroprevalence was 46.13%. Four DNA positive samples out of 42,240 individual blood donations were identified (0.009%); all had low levels of viremia (range 11-255 IU/mL). No window-period donation was identified. No TT-CMV was found. DISCUSSION: Cell-free CMV remains a concern with current blood component processing as it passes through all the processes. However, since low levels of CMV DNA were identified in the donations tested, and no BMT recipients had TT-CMV, the residual threat of TT-CMV after leukocyte reduction appears to be very low.