Herpes Simplex Virus Type 1 McKrae and 17syn1 Result in Different In Vivo Reactivation Phenotypes

The herpes simplex virus type 1 (HSV-1) LAT gene is the only viral gene abundantly transcribed during latency. LAT null mutants created with strains McKrae and 17syn1 are impaired for both in vivo spontaneous and in vivo-induced reactivation. Thus, LAT is essential for efficient in vivo-induced and spontaneous reacti-vation. Different investigators have studied two LAT mutants containing a StyI-StyI region deletion corre-sponding to LAT nucleotides 76 to 447. One mutant, dLAT371 (parent strain, McKrae), had parental high frequencies of spontaneous reactivation. In vivo-induced reactivation was not examined. The other mutant, 17DSty (parent strain, 17syn1), had parental frequencies of in vitro reactivation following cocultivation of explanted ganglia but reduced frequencies of in vivo-induced reactivation. Spontaneous reactivation frequency was not reported for 17DSty. These combined results suggested the possibility that in vivo spontaneous reactivation and in vivo-induced reactivation may map to different regions within the LAT domain. We now report that dLAT371 has in vivo-induced reactivation frequencies of the parent and that 17DSty has reduced frequencies of in vivo spontaneous reactivation. Thus, dLAT371 demonstrated the parental phenotype for both in vivo spontaneous and-induced reactivation while the apparently identical 17DSty was impaired for both i