Varicella-zoster virus gene expression in latently infected and explanted human ganglia

A consistent feature of varicella-zoster virus (VZV) latency is the restric ted pattern of viral gene expression in human ganglionic tissues. To unders tand further the significance of this gene restriction, we used in situ hyb ridization (ISH) to detect the frequency of RNA expression for nine VZV gen es in trigeminal ganglia (TG) from 35 human subjects, including 18 who were human immunodeficiency virus (HIV) positive. RNA for VZV gene 21 was detec ted in 7 of 11 normal and 6 of 10 HIV-positive subjects, RNA for gene 29 wa s detected in 5 of 14 normal and 11 of 11 HIV-positive subjects, RNA for ge ne 62 was detected in 4 of 10 normal and 6 of 9 HIV-positive subjects, and RNA for gene 63 was detected in 8 of 17 normal and 12 of 15 HIV-positive su bjects. RNA for VZV gene 4 was detected in 2 of 13 normal and 4 of 9 HIV-po sitive subjects, and RNA for gene 18 was detected in 4 of 15 normal and 5 o f 15 HIV-positive subjects. By contrast, RNAs for VZV genes 28, 40, and 61 were rarely or never detected. In addition, immunocytochemical analysis det ected the presence of VZV gene 63-encoded protein in five normal and four H IV-positive subjects. VZV RNA was also analyzed in explanted fresh human TG and dorsal root ganglia from five normal human subjects over a period of u p to 11 days in culture. We found a very different pattern of gene expressi on in these explants, with transcripts for VZV genes 18, 28, 29, 40, and 63 all frequently detected, presumably as a result of viral reactivation. Tak en together, these data provide further support for the notion of significa nt and restricted viral gene expression in VZV latency.