pUL37 R2 is essential for HSV-1 neuroinvasion.

(A) Diagram of the neuroinvasive route examined in mice following inoculation of a scarified cornea with HSV-1. (B) Representative images of the cornea (2 dpi), trigeminal ganglia (6 dpi), and principal sensory trigeminal nuclei (Pr5; 6 dpi), following corneal inoculation with wild-type or R2-mutant HSV-1. Infected cells were visualized by virtue of a pUL25/mCherry fluorescent capsid reporter encoded by the viruses (scale bars for trigeminal ganglia and Pr5 are 500 μm; cornea scale bar is 1000 μm). (C) Mice were infected on both eyes with untagged wild-type (WT) or R2-mutant (R2) HSV-1 following corneal scarification. Viral titers in the tear films were independently determined from each eye by swabbing at the indicated day post-infection (dpi). At 4 days post corneal inoculation, the combined titer of the left and right trigeminal ganglia and of the whole brain were determined. The mean titer of each data set is indicated by a red bar (5 mice per virus; *, p < 0.05 based on a two-tailed unpaired t test). (D) qPCR was preformed using primers directed against the HSV-1 UL35 gene. Trigeminal ganglia and brain samples were collected at 4 days post infection and scored as positive for viral DNA if the threshold cycle (Ct) value was below the average Ct value of the water controls by more than two standard deviations (inset). Amplification curves for both HSV-1 WT and R2-mutant infected samples are shown.