Photochemical Inactivation of Bacteria and HIV in Buffy–Coat–Derived Platelet Concentrates under Conditions That Preserve in vitro Platelet Function

Background and Objectives: A photochemical process has been tested for the inactivation of viruses and bacteria in buffy–coat derived platelet concentrates (BC PCs). Materials and Methods: BC PCs in 35% CPD plasma and 65% platelet–additive solution (PAS III) were exposed to photochemical treatment (PCT) with 150 μM of the psoralen S–59 and a 3 J/cm2 treatment with long–wavelength ultraviolet light (UVA, 320–400 nm). Platelet function was evaluated following PCT using a panel of in vitro assays. Results: This PCT process was highly effective at inactivating gram–positive bacteria (Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis) and gram–negative bacteria (Enterobacter aerogenes, Pseudomonas aeruginosa, Serratia marcescens). No viable bacteria were detected following PCT and 7 days of platelet storage while bacterial growth was detected in paired untreated control BC PCs. Complete inactivation of the gram–positive Bacillus cereus was achieved only in one of two replicate experiments with BC PCs. PCT was also highly effective for inactivation of human immunodeficiency virus HIV–1 in BC PCs inoculated with approximately 106 tissue culture infectious doses per milliliter (TCID50/ml) of cell–associated HIV–1. Rapid inactivation was observed with increasing UVA doses: with 150 μM S–59 and a 1 J/cm2 treatment of UVA, a reduction of 5.6±0.5 log TCID50/ml was achieved, and a reduction of >6.4 log TCID50/ml was achieved with 150 μM S–59 and a 3 J/cm2 treatment of UVA. No physiologically relevant differences in platelet functions were found between the test and the control BC PCs during 7 days of storage. Conclusion: PCT with 150 μM S–59 and a 3 J/cm2 UVA treatment does not adversely affect in vitro properties of BC PCs stored at 22°C for 7 days. The PCT process inactivated bacteria and HIV–1 inoculated into the BC PCs. These results extend the earlier reported efficacy of PCT apheresis PCs to BC PCs.