FIG 2.

Delineation of UL37 amino acids involved in infectious virus production. (A) Schematic of the UL37 protein depicting known functional domains and the approximate locations of nine single- and double-amino-acid replacements constructed to assess their role in infectious virus production. (B) Images of viral plaques produced in the transfection-infection complementation of the UL37-null virus. Vero cells were transfected with each plasmid. After 36 h, plasmid-transfected cells were infected with UL37-null virus at an MOI of 5 and virus stocks were collected at 24 hpi. Viral plaques were visualized by immunohistochemistry at 48 hpi (see Materials and Methods). The plasmids encoding mutations in the amino acids of UL37 that were able to complement the UL37-null virus are marked with a green plus, and the mutations which were not able to complement are marked by a red minus. (C) Viral titers obtained in the transfection-infection complementation assay. Titers of virus stocks collected at 24 hpi with the UL37-null virus were determined on the BD45 cell line, which expresses the UL37 protein in trans. A plasmid expressing the wild-type UL37 protein was used as a positive control. A second positive control consisted of mock transfection, followed by infection with wild-type HSV-1, while a UL20-expressing plasmid was used as a negative control.