Figure 3.

Schematic representation of the derivation of R7020 (aka NV1020). This virus was constructed for the purpose of creating a vaccine for HSV-1 and HSV-2 that would be administered by intramuscular injection of living virus.¹³⁸ HSV-1(F) was initially deleted for thymidine kinase (U_L23) and U_L24. The internal set of the inverted repeats, containing α0, α4, γ₁34.5, ORF O, and ORF P, was replaced with a novel construct that contained U_L23 fused to the α4 promoter-regulatory region and 3′ to a series of HSV-2 genes (U_S2, HSV protein kinase, U_S5, glycoproteins G, D, and I, as well as a portion of E). The terminal inverted repeat remained intact. Thus, this chimeric virus, containing both HSV-1 and HSV-2 sequences, has been extensively tested in both rodent and primate species for safety (LD₅₀ = 2.7 × 10⁶ PFU versus 3.8 × 10² PFU for HSV-1(F)) and genetic stability.^138,139