Combined VPA/AZT treatment is linked to a significant reduction of the PVL in STLV-1 asymptomatic carriers. The PVL (copy number/10⁵ PBMCs) was determined by real-time PCR, as previously described.³⁶  For a given animal, all samples were run at the same time, to avoid interexperimental variation. The values presented here are the mean of 2 independent assays. C indicates controls; A, AZT; V, valproate; and VA, valproate + AZT.