Photodynamic treatment of adenoviral vectors with visible light: an easy and convenient method for viral inactivation

Recombinant adenovirus vectors are popular fools for gene transfer and gene therapy However biosafety constraints require that all handling of the vec tors and vector-containing samples is restricted to dedicated containment l aboratories, unless they had undergone a validated virus-inactivation proce dure, which decontaminates the samples from any active virus. In this study we evaluated the feasibility of photodynamic treatment (PDT) with visible light to inactivate recombinant adenovirus vectors in biological samples, w ith minimum associated effects on other biological activities. Several phot osensitizers were tested for their capacity to inactivate a model human ade novirus vector, AdCMVLuc, upon illumination. Four photosensitizers (methyle ne blue (IB), rose bengal (RB), uoporphyrin (UP) and aluminum phthalocynine tefrasulphonate (AIPcS(4))) could inactivate the adenovirus, as measured b y expression of the luciferase reporter gene and by plaque assay. Of these, MB demonstrated to be the most effective sensitizer in phosphate-buffered saline (PBS), giving > 7 log,, inactivation of the adenovirus. DNA isolated from MB- and light-treated virions was inefficient as a template for; tran scription. Furthermore, Southern blot analysis revealed fragmentation of th e viral DNA. Based on ifs preference.; for DNA, MB is suited for adenovirus inactivation in blood plasma. Spiking experiments in which AdCMVLuc was ad ded to plasma samples demonstrated a reduction (>4 log(10)-fold) of reporte r gene expression to almost background levels In contrast to MB, photodynam ic treatment with RE, UP or AIPcS(4) did not lead to DNA damage. Although a lterations of the viral capsid could not be detected the binding pattern of the particles to target cells was significantly changed, Taken together, o ur data demonstrate that PDT is an efficient, convenient and useful method for the inactivation of adenovirus vectors in biological samples.