The Herpes Simplex Virus Type 2 (HG52) Variant JH2604 Has a 1488 bp Deletion which Eliminates Neurovirulence in Mice

The herpes simplex virus type 2 (HG52) deletion variant JH2604 is avirulent (LD₅₀ > 10⁷ p.f.u./mouse) for mice compared to the parental wild-type virus (LD₅₀ < 10² p.f.u./mouse) and fails to replicate in vivo. JH2604 has a 1488 bp deletion within the 3 kb BamHI v fragment (0 to 0.02 and 0.81 to 0.83 map units) which removes one copy of the 17 bp direct repeat DR1 element of the a sequence and terminates 522 bp upstream of the 5' end of the immediate early gene 1. In vivo selection after transfection of intact JH2604 DNA with the BamHI g (v + u) joint fragment of HG52 results in the isolation of wild-type virus with an LD₅₀ of < 10² p.f.u./mouse. These results show that a 1488 bp sequence within the terminal portion of the genome long repeat region confers neurovirulence on strain HG52.