TKT and infection: Infection of neuronal cultures with 5×105 p.f.u. (1.3×108 input genomes) per well of the VP16- mutant (in1329), containing an ICP4P lacZ reporter cassette in the TK locus (Homer et al., 1999), resulted in β-Gal expression in 32 % of neurones and no detectable reporter gene expression in non-neuronal cells.