TMEFF1 and viral infectious disease: In the absence of an appropriate method for quantifying cell-surface NECTIN-1 expression in neurons, we investigated whether a lack of TMEFF1 resulted in enhanced HSV-1–cell membrane fusion and virus entry during the first few hours of viral infection by assessing HSV-1 entry with a modified HSV-1 encoding a fusion of β-lactamase to the viral tegument protein pUL47, making it possible to quantify CCF2 cleavage following the entry of HSV-1 into the cells47.