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BACKGROUND:  WBC depletion by filtration may prevent the transmission of HTLV-I, which requires cell-to-cell contact. The removal of HTLV-I-infected cells in routinely filtered blood cell components was measured.

STUDY DESIGN AND METHODS:  The study was conducted in Martinique where systematic screening for HTLV-I and -II and universal leukoreduction are mandatory. HTLV-I was quantified by use of real-time PCR in 8 RBC units and 4 PLT concentrates before and after filtration. HTLV-I proviral load in PBMNCs was determined in five of the eight HTLV-I-infected blood donors.

RESULTS:  The amount of MNC-associated HTLV-I DNA in RBC units before filtration was 21 × 106± 29 × 106 copies (mean ± SD). HTLV-I was detected in 4 of 8 RBC units after filtration, with a number of copies in the MNC fraction ranging from 20 to 140, following a 4.9 to 5.8 log reduction. Flow cytometry analysis performed in 2 of the filtered RBC units containing detectable HTLV-I showed suboptimal and out-of-range leukoreduction (0.56 × 106 and 1.22 × 106 residual WBCs). HTLV was not detected in filtered RBCs from the blood donor with the highest percentage of HTLV-I-infected PBMCs (9%).

CONCLUSION:  This study confirms that HTLV-I-infected cells can be detected in filtered blood cell components and shows that optimal leukoreduction is critical for HTLV-I removal.