Penetration kinetics of PrV mutants. Rates of entry of gG–β-Gal recombinant PrV-1112, PrV-gE/I−, PrV-gM−, or PrV-gE/I/M− into wild-type RK13 (A), Vero (B), or MDBK (C) cells were determined as described elsewhere (37). Average values and standard deviation from three independent experiments are depicted.