Pathogen inactivation in blood products.

A combination of the economic importance of blood as a resource and the advent of the AIDS epidemic has led to a requirement for improved pathogen screening techniques for donated blood. However, due to window periods where infective agents cannot be detected, the ability to disinfect of blood and its derivatives plasma, platelets and red blood cell concentrates has assumed great importance. Whereas conventional disinfection techniques such as solvent-detergent treatment or ultra-violet irradiation may be employed in plasma or protein concentrates, the collateral damage associated with such treatments disallows their use with cellular fractions. In many ways the pathogen selectivity required here is akin to standard antimicrobial chemotherapy but is complicated by the requirement for activity against the full range of microbes--viruses, bacteria, yeasts and protozoa--rather than simply antibacterial or antiviral etc. The recent problems due to prion agents in the blood supply mean that such agents should also be included in any proposed disinfecting regimen. Several new approaches to microbial disinfection have been proposed by academia and the "blood industrials" : targeted chemotherapy, photochemotherapy and photodynamic antimicrobial chemotherapy.