Photochemical pathogen reduction: improved safety for the blood supply?

Safety of the blood supply depends on an increasingly intense donor-screening process and a series of serologic or nucleic acid-based tests for HIV1/2, HTLVI/II, hepatitis B, hepatitis C, and syphilis. There are, however, no tests for myriad other disease agents that could threaten the blood supply, including bacteria, malaria, babesiosis, Chagas disease, and emerging agents such as West Nile virus. Pathogen reduction (PR) technology is a new approach that places a PR compound in the donor blood bag ready to be activated after blood collection. Several technologies are separately being developed for platelets, red cells, and plasma. The common approach taken by the various methodologies is to disrupt pathogen DNA or RNA polymerase activity and interfere with pathogen nucleic acid replication and, thus, disease transmission. The key is for the PR technology to prevent pathogen transmission but preserve functional activity of transfused cells and plasma proteins.

van Rhenen and colleagues (page 2426) report on the first randomized double-blind clinical trial in European patients using one such technology. Their system exposes bags of buffy-coat–prepared platelets containing a synthetic psoralen compound (amotosalen) to UVA light. Once photoactivated, the amotosalen intercalates and crosslinks pathogen nucleic acid bases, preventing replication. van Rhenen's protocol randomized thrombocytopenic oncology patients to receive either untreated control (n = 51 patients; 256 transfusions) or photochemically treated (PCT; n = 52 patients; 311 transfusions) platelet products. The estimated effect of PCT treatment on the mean 1-hour posttransfusion corrected count increment (CCI), one primary endpoint, was a decrease of 1800 (P = .11) in the platelet count. The mean 24-hour CCI for the PCT arm, however, was 3200 lower than that for the control arm (P = .02). Blinded, clinically assessed bleeding events were equivalent between the 2 groups, speaking to preservation of platelet hemostatic function. There were no reported differences in adverse events between the 2 groups.

While data from this first reported clinical trial are very promising, more data on in vivo platelet function would be useful. Further, any long-term adverse effects on recipients exposed to platelets treated by the amotosalen and UVA light procedure remain to be determined. Clearly, this paper presages the future focus on PR methods for ensuring the safety of the blood supply from known, as well as emerging, pathogens. This study reports on buffy-coat–prepared platelets, a technology used widely in Europe but not in the United States, where platelets are prepared by apheresis or from whole blood as platelet-rich plasma. Studies on these products and future reports on red cell PR systems are awaited. At least in the US for the short term, PR technology might be used in addition to, not in lieu of, existing blood screening maneuvers. The important role to be played by PR in the future remains to be defined.