Detection of immediate early protein ICP27/IE63 and thymidine kinase in the course of reactivation of latent herpes simplex virus 1 infection

We followed the kinetics of reactivation of latent Herpes simplex virus 1 (HSV-1) infection established in rabbits by corneal route. The corresponding trigeminal ganglia (TG) were cultured and the culture medium was examined at daily intervals for release of infectious virus. Sections from the cultured TG fragments were stained with antisera against non-structural proteins such as the immediate early (IE) protein ICP27 and the early (E) proteins thymidine kinase (TK), the large subunit of ribonucleotide reductase (RR1), the ori-binding protein OBP and with a human serum obtained from volunteers immunized with an experimental subunit HSV-1 envelope (env) vaccine containing late structural proteins gB1, gC1, gD1 and gG1 (env antiserum). By indirect immunofluorescence (IF) test, ICP27 was detected in a few neurons from day 1 post explantation (p.e.), while TK was observed in neurons from day 2 p.e. Fluorescence with the human env antiserum was seen at day 3 p.e. The RR1 and OBP antisera stained productively infected Vero cells from 3 and 4 hrs post inoculation (p.i.), respectively. However, these sera showed no IF in cultured ganglion fragments at any interval examined. Our results showed the same cascade of HSV-1 IE and E protein expression during productive infection and reactivation in vitro.