Changes of biological character were observed after 20, 40, 60, 80,100, 120 and 140 micromoL/L ACV were added into cell cultures, and also the morphological observation was detected with phase-contrast microscopy after HSV-2 was inoculated into SH-SY5Y cells using MOI of 0.1, 1, 10 and 100. Adenosine monophosphate pretreatment did not, however, eradicate latent virus. The adoptive transfer of cytolytic T lymphocytes derived from in vitro cultures after restimulation with HSV-infected, syngeneic stimulator cells exhibiting class I H-2-restricted, L3T4- Lyt-2+ HSV-specific cytolytic activity immediately before infection with a high dose of HSV reduced the levels of infectious HSV recovered from the footpad tissue during acute infection and the levels of latent HSV reactivated from the dorsal root ganglia to levels expected from mice infected with a low dose. The deletion of both regions almost completely eliminated acute LAT transcription, although additional acute LAT-region transcription directed by sequences upstream of either region was detected by reverse transcriptase PCR. These explant cultures yielded both TK+ and TK− viruses on reactivation. In rare instances, a publisher has elected to have a “zero” moving wall, so their current issues are available in JSTOR shortly after publication. We conclude that downstream regulatory elements are necessary for maximal acute LAT expression but do not constitute an independent promoter during latency and do not play an obvious role in the establishment of our reactivation from latency.