pUL37 R2 is essential for sustained retrograde motion during ingress.

Dorsal root ganglion (DRG) sensory neuron explants were infected in 2 ml of media with 3.5 x 10⁷ PFU/ml of PRV (WT and R2 mutant) or 1.3 x 10⁷ PFU/ml of HSV-1 (WT and R2 mutant). Viruses encoded a pUL25/mCherry or pUL25/GFP fusion to provide imaging of individual capsids in living cells. Capsid axonal transport was recorded by time-lapse fluorescence imaging between 3–4 hpi. More than 90 capsids were analyzed per experiment across three biological replicates. (A) Fraction of time that individual wild-type (WT) and R2-mutant (R2) capsids moved retrogradely (white), anterogradely (gray), or were motionless (black). Error bars are s.d. (B) Net displacement of capsids over a period of 10 seconds. Positive values indicate movement towards neuronal soma (retrograde displacement). Error bars are s.d. (****, p < 0.0001 based on two-tailed unpaired t test). (C) Representative kymographs of axonal transport in neurons. Distance and time are represented on the x and y axis respectively. (D) Delivery of capsids to nuclear rims at 3–4 hpi following co-infection of DRGs with a pUL25/GFP tagged wild-type (WT) virus and either WT or R2 mutant virus encoding a pUL25/mCherry capsid tag.