Structure-Based Mutations in the Herpes Simplex Virus 1 Glycoprotein B Ectodomain Arm Impart a Slow-Entry Phenotype

Fan, Qing; Kopp, Sarah J.; Connolly, Sarah A.; Longnecker, Richard

The current model of HSV entry proposes that the gH/gL heterodimer conveys a signal to gB to trigger fusion (31) . To explore whether a defect in the gB-gH/gL interaction might contribute to the penetration defect observed in the gB 3A viruses, a cell-cell fusion assay was used. This assay permits the titration of different levels of gH/gL DNA, which results in different levels of protein expression. Expression of higher levels of gH/gL may compensate for a weak interaction between gB 3A and gH/gL. When cells were cotransfected with gD, gH, gL, and gB 3A, increasing the amounts of gH and gL DNA transfected did not enhance cell-cell fusion (Fig. 9C) . In fact, greater levels of gH/gL DNA impaired the fusion mediated by gB 3A. These results do not exclude the possibility that the gB 3A mutant has a defect in gH/gL interaction; however, the results do not support the hypothesis either.