Molecular analysis of acyclovir-induced suppression of HSV-1 replication in rabbit corneal cells

An in vitro HSV drug-suppression model has been established in rabbit corneal cell (SIRC) monolayers. Confluent SIRC monolayers were inoculated with McKrae strain HSV-1 (0.014 PFU/cell) and subsequently suppressed with acyclovir (ACV) (40 micrograms/ml) after adsorption for 1 hr at 37 degrees C. On days 0-5 postinoculation (PI), infectious HSV-1 was detected in approximately 50% of the SIRC cell cultures by standard supernatant and cell-free homogenate co-culture assays. On days 6-10 postsuppression, infectious HSV was detected in only 7-19% of the cultures. After removal of ACV suppression in the cultures (day 11 PI), HSV cytopathology developed to a 3-4+ level within 2-5 days. Dot blot hybridization of DNA extracted from the cultures indicated that the HSV genome was retained consistently in SIRC cells at a level of 0.0015-0.015 copies per cell during active ACV-suppression. During ACV-suppressed infection, approximately 0.9% of the SIRC cells contained the HSV genome as demonstrated by blot hybridization. After removal of ACV, a 1000-fold increase in HSV DNA concentration in SIRC cell cultures was detected.