Adenoviral gene transfer into the normal and injured spinal cord: enhancedtransgene stability by combined administration of temperature-sensitive virus and transient immune blockade

This study characterized gene transfer into both normal and injured adult r at dorsal spinal cord using first (E1-/E3-) or second (E1-/E2A(125)/E3-, te mperature sensitive; ts) generation of replication-defective adenoviral (Ad ) vectors. A novel immunosuppressive regimen aimed at blocking CD4/CD45 lym phocytic receptors was tested for improving transgene persistence. In addit ion, the effect of gene transfer on nociception was also evaluated. Seven d ays after treatment, numerous LacZ-positive cells were observed after trans fection with either viral vector. By 21 days after transfection, beta-galac tosidase staining was reduced and suggestive of ongoing cytopathology in bo th Ad-treated groups, despite the fact that the immunogenicity of LacZ/Ad(t s) appeared less when compared with that elicited by the LacZ/Ad vector. In contrast, immunosuppressed animals showed a significant (P less than or eq ual to 0.05) increase in the number of LacZ-positive cells not displaying c ytopathology. In these animals, a concomitant cytopathology. In these anima ls, a concomitant reduction in numbers of macrophages/microglia and CD4 and CD8 lymphocytes was observed. Only animals that received LacZ/Ad(ts) and i mmunosuppression showed transgene expression after 60 days. Similar results were observed in animals in which the L4-L5 dorsal roots were lesioned bef ore transfection. Gene transfer into the dorsal spinal cord did not affect nociception, independent of the adenovirus vector. These results indicate t hat immune blockade of the CD4/CD45 lymphocytic receptors enhanced transgen e stability in adult animals with normal or injured spinal cords and that p ersistent transgene expression in the spinal cord does not interfere with n ormal neural function.