Evaluation of HTLV‐I removal by filtration of blood cell components in a routine setting

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Abstract
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.