Photochemical treatment of platelet concentrates offers the potential for reducing transfusion-related viral and bacterial diseases.

We have studied the photochemical reactions of 8-methoxypsoralen (8-MOP) with calf thymus DNA. Analysis of the photoproducts formed was carried out by enzymatic digestion of the 8-MOP-modified DNA, followed by HPLC separation of photoadducts by high-pressure liquid chromatography (HPLC). The 4',5' (furan-side) monoadduct of 8-MOP bound to thymidine is converted to cross-linked thymidine-8-MOP-thymidine diadduct by 341.5 nm light with a quantum yield of 0.028 +/- 0.004. This is 4 times greater than the quantum yield for initial adduct formation (0.0065 +/- 0.0004). When low levels of 8-MOP are covalently bound to DNA by using 397.9 nm light, less than 10% of the adducts formed are diadducts yet nearly 70% are in 5'-TpA cross-linkable sites. The furan-side monoadducts in these sites can subsequently be converted to diadduct or to a lesser extent 3,4 (pyrone-side) monoadduct.

No abstract

We describe a photochemical procedure for the sterilization of polynucleotides that are created by the Polymerase Chain Reaction (PCR). The procedure is based upon the blockage of Taq DNA polymerase when it encounters a photochemically modified base in a polynucleotide strand. We have discovered reagents that can be added to a PCR reaction mixture prior to amplification and tolerate the thermal cycles of PCR, are photoactivated after amplification, and damage a PCR strand in a manner that, should the damaged strand be carried over into a new reaction vessel, prevent it from functioning as a template for the PCR. These reagents, which are isopsoralen derivatives that form cyclobutane adducts with pyrimidine bases, are shown to stop Taq polymerase under conditions appropriate for the PCR process. We show that effective sterilization of PCR products requires the use of these reagents at concentrations that are tailored to the length and sequence of the PCR product and the level of amplification of the PCR protocol.

These results indicate that no neoantigens were detected by ELISA after PCT, suggesting that transfusion of PCT PLTs or PCT plasma does not induce adverse immunologic responses.