A herpesvirus vector can transduce axotomized brain neurons

Abstract

If gene therapy is to be used to promote axon regeneration after spinal cord injury, a suitable vector for transgene delivery must be obtained. Replication-defective herpes simplex virus (HSV) vectors are promising candidates. We have examined whether they can express a LacZ transgene in injured neurons of adult rat brain. We transected the medial forebrain bundle, injected replication-defective HSV/ LacZ vectors close to the lesion site, and looked for transgene expression at 2–14 days after the lesion. The vectors carried the LacZ transgene controlled either by the cytomegalovirus immediate-early promoter (vector CS5) or the HSV latency-associated promoter (vector CS1). CS5 transfected many cells near the lesion at 2 days, but did not give persistent expression at 5 days. CS1, in contrast, labeled many neurons in midbrain regions remote from the injection site at 5 days, and much of this expression remained at 12–14 days. The neurons of most interest were in the substantia nigra pars compacta and parabrachial nuclei, which were axotomized by the lesion. Vector-driven β-galactosidase expression was detected in neurons in both regions. These were confirmed as axotomized by double immunofluorescence for c-Jun. By 12–14 days, many substantia nigra neurons had disappeared but some transduced neurons remained; there was no net loss of transduced neurons from the parabrachial nuclei. These results show that an HSV vector is capable of transducing axotomized cells in the central nervous system and producing transgene expression in them for at least 2 weeks after injection.